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MR Imaging of Acute Right Lower Quadrant Pain in Pregnant and Nonpregnant Patients¹

¹ From the Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Ave, Boston, MA 02215. Recipient of a Cum Laude award for an education exhibit at the 2005 RSNA Annual Meeting. Received June 7, 2006; revision requested July 19 and received September 13; accepted September 14. N.M.R. receives research support from GE Healthcare (Waukesha, Wis), is on the advisory board of Berlex Laboratories (Wayne, NJ), and is a consultant to CAD Sciences (White Plains, NY); all other authors have no financial relationships to disclose. Address correspondence to I.P. (e-mail: ipedrosa{at}bidmc.harvard.edu).

	Abstract

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction MR Imaging Protocols Normal Appendix Appendiceal Disorders Other Disorders Arising from... Obstetric and Gynecologic... Urinary Tract Disorders Conclusions References

 
The use of magnetic resonance (MR) imaging in the evaluation of acute abdominal pain is increasing, particularly in those circumstances where computed tomography (CT) is not desirable (eg, pregnancy, allergy to iodinated contrast material). Although ultrasonography (US) is considered the imaging study of choice for evaluation of abdominal pain in pregnant patients, MR imaging is a valuable adjunct to US in evaluation of pregnant patients with acute right lower quadrant (RLQ) pain who have inconclusive US results. MR imaging is also frequently used in patients with renal failure, in whom the use of iodinated contrast material is contraindicated, as well as in cases where CT results are inconclusive. In patients with acute RLQ pain, the breadth of abnormalities visible at MR imaging is very broad, with pathologic conditions potentially originating from multiple organ systems, but most commonly from the gastrointestinal and genitourinary systems. MR imaging is an excellent imaging modality for evaluation of RLQ pain and should be strongly considered in those patients in whom use of iodinated contrast media or radiation is not desirable.

© RSNA, 2007

	LEARNING OBJECTIVES FOR TEST 3

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction MR Imaging Protocols Normal Appendix Appendiceal Disorders Other Disorders Arising from... Obstetric and Gynecologic... Urinary Tract Disorders Conclusions References

 
After reading this article and taking the test, the reader will be able to:

• Discuss MR imaging protocols for evaluation of pregnant and nonpregnant patients with acute RLQ pain.
  
• Describe the MR imaging appearances of the normal and abnormal appendix.
  
• Identify various common conditions that masquerade as acute appendicitis in both pregnant and nonpregnant patients on MR images.
  

	Introduction

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction MR Imaging Protocols Normal Appendix Appendiceal Disorders Other Disorders Arising from... Obstetric and Gynecologic... Urinary Tract Disorders Conclusions References

 
The broad range of conditions causing acute right lower quadrant (RLQ) pain may involve multiple organ systems, including the gastrointestinal tract, urinary tract, and female reproductive tract. Imaging examinations are frequently indicated, as the clinical presentation is commonly confusing. The diagnostic algorithm is based on the clinical history, physical examination, and laboratory analysis. Computed tomography (CT) has become the standard of care in the evaluation of patients with suspected disease of the gastrointestinal and urinary tracts. Ultrasonography (US) is preferred in patients with suspected disease affecting primarily the uterus or adnexa and in pregnant patients. However, both modalities have limitations. CT relies on use of ionizing radiation and commonly iodinated contrast material, which are less desirable in pregnancy and in patients with contrast material allergy and renal failure. US can be limited in patients with large body habitus or in the presence of extensive air or calcification, and it is very dependent on operator experience (1). Despite these limitations, US is the imaging modality of choice in pregnant patients with RLQ pain because it uses neither ionizing radiation nor intravenous contrast material (2,3).

Magnetic resonance (MR) imaging has until very recently only rarely been proposed as an alternative imaging modality for evaluation of acutely ill patients. Limited availability of MR imaging units and the complexity, length, and cost of MR imaging examinations are some of the impediments to more widespread use in the acute setting. However, its multiplanar capacity and excellent soft-tissue contrast, the lack of ionizing radiation, and the generally accepted safety of the currently available intravenous contrast agents are favorable features for MR imaging in acutely ill patients. MR imaging has recently been proposed as an adjunct to US in the evaluation of pregnant patients in whom the US results are inconclusive or nondiagnostic (4–7).

Diagnosis of acute appendicitis in pregnancy represents a clinical challenge due to the anatomic and physiologic alterations associated with pregnancy (8,9). MR imaging is an excellent modality for excluding acute appendicitis when the appendix is not visualized at US (7). Furthermore, acute appendicitis can be diagnosed with MR imaging and an alternative diagnosis can be identified in a substantial number of pregnant women with right-sided abdominal pain (7).

In this article, we present MR imaging protocols for the comprehensive evaluation of RLQ pain in both pregnant and nonpregnant patients. The MR imaging appearance of the normal anatomic structures in the RLQ is reviewed with emphasis on the normal and abnormal appendix in both pregnant and nonpregnant patients. Finally, the MR imaging findings of common and uncommon disorders arising from the gastrointestinal tract, female reproductive tract, and urinary tract that can masquerade clinically as acute appendicitis are illustrated and discussed.

	MR Imaging Protocols

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction MR Imaging Protocols Normal Appendix Appendiceal Disorders Other Disorders Arising from... Obstetric and Gynecologic... Urinary Tract Disorders Conclusions References

 
Nonpregnant Patients
The MR imaging protocol for nonpregnant patients is detailed in Table 1. A phased-array body coil is recommended whenever possible because it offers superior signal-to-noise ratio compared with that of the built-in body coil. Oral contrast material is not used routinely for patients with suspected disease of the genitourinary tract, although it may be administered in those with suspected disease of the gastrointestinal tract. Before initiation of the study, a 1-mg intramuscular dose of glucagon (Glucagen; Bedford Laboratories, Bedford, Ohio) is given to decrease artifacts arising from bowel peristalsis.

We routinely administer gadopentetate dimeg-lumine (Magnevist; Berlex Laboratories, Wayne, NJ) intravenously at our institution for evaluation of abdominal and pelvic disease. MR images are obtained before and after a bolus of gadolinium contrast material at a dose of 0.1 mmol/kg and a rate of 2 mL/sec followed by a flush of 20 mL of saline given at the same rate. A bolus test of 2 mL of gadolinium contrast material at 2 mL/sec is used to time the arterial phase, as previously described by Earls et al (10). Alternatively, the arterial phase may be timed by using an automated bolus tracking device or fluoroscopic triggering technique. MR images are then acquired during the properly timed arterial phase, portal phase (20 seconds after the arterial phase), and delayed venous phase (60 seconds after the arterial phase).

Pre- and dynamic postcontrast images are obtained with a 3D fat-saturated T1-weighted spoiled GRE sequence. These 3D data sets offer superior signal-to-noise ratio and thinner sections (without an intersection gap) than do 2D acquisitions. In addition, 3D acquisitions can be used for generating multiplanar reformations or MR angiograms that allow a comprehensive evaluation of the abdomen or pelvis (11,12).

Pregnant Patients
Written informed consent regarding use of MR imaging in pregnancy is obtained before performing the examination.

MR examination is thought to be safe in pregnancy and can be used regardless of the trimester when the outcome of the examination has the potential to affect the care of the patient (13). Examinations are performed at a field strength of 1.5 T with the patient in the supine position and with a body phased-array coil. Patients receive an oral preparation consisting of 300 mL of Gastromark (Mallinckrodt Medical, St Louis, Mo) and 300 mL of Readi-cat 2 (E-Z-Em, Westbury, NY) starting 1–1.5 hours before the MR imaging examination. This solution provides negative contrast (dark signal intensity) within the bowel lumen on both T1- and T2-weighted images without causing substantial susceptibility effects that can obscure the anatomy (5,7,14). Intravenous contrast agents are not used.

The MR imaging protocol for pregnant patients is detailed in Table 2. Single-shot fast SE images are acquired in the three orthogonal planes (axial, coronal, and sagittal). Conventional SE and fast SE imaging is less desirable in the pregnant patient because fetal motion may substantially degrade image quality. Single-shot imaging provides a motion-insensitive strategy even in the presence of severe fetal motion. Furthermore, image quality in single-shot imaging is not degraded in those patients with limited breath-holding capability, a common occurrence among gravid patients. However, breath-hold acquisitions are encouraged to ensure adequate anatomic coverage and contiguous display of the anatomy.

	Normal Appendix

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction MR Imaging Protocols Normal Appendix Appendiceal Disorders Other Disorders Arising from... Obstetric and Gynecologic... Urinary Tract Disorders Conclusions References

 
The normal appendix is a blindly ending tubular structure that averages 10 cm in length and arises in the medial aspect of the cecum, approximately 3 cm below the ileocecal valve (15). The normal appendix is either collapsed or partially filled with fluid, contrast material, or air (15). In the absence of oral contrast material, the normal appendix is seen as a cordlike structure of intermediate signal intensity, similar to that of the bowel wall (16) (Fig 1). A hyperintense center and a hypointense wall on axial T2-weighted echo train images and predominantly low signal intensity on T1-weighted images have been described as the typical appearance of the normal appendix in the pediatric population (17). The normal appendiceal wall measures less than 2 mm in thickness (15). The normal appendiceal diameter typically measures less than 6 mm on single-shot fast SE images (7). The normal appendix can be seen at MR imaging in up to 90% of nonpregnant patients (16,17) and 83%–89% of pregnant women (6,7). Definitive visualization of the normal appendix has been reported in 78% and 60% of nonpregnant patients at T1-weighted SE imaging and T2-weighted single-shot turbo SE imaging, respectively (18).

View larger version (175K): [in this window] [in a new window] [Download PPT slide]   Figure 1.  Normal appendix in a 48-year-old woman with pelvic pain. Coronal T2-weighted single-shot fast SE image of the upper pelvis shows the cecum (C) and bladder (B). The normal appendix (arrows) is clearly delineated as a blind-ending tubular structure arising off the base of the cecum. In the absence of oral contrast material, the normal appendix demonstrates signal intensity similar to that of the bowel wall on single-shot fast SE images.

Single-shot fast SE images are the cornerstone of our MR imaging protocol for pregnant women and essential to identify the appendix. In our experience, use of a cross-reference imaging tool available in our picture archiving and communication system is crucial to confirm that this structure is the appendix by identifying its typical blind-end tubular appearance in the same anatomic location in all three planes.

In our experience, the oral preparation is essential in pregnant patients, in whom intravenous administration of gadolinium contrast agents is not used (7). The iron oxide particles in the oral preparation render the bowel containing oral contrast material as dark signal with all sequences, due to T2* effect. When the appendix is filled with air or oral contrast material, it appears larger and darker on TOF T2*-weighted images than on the single-shot fast SE images, the so-called blooming effect, due to susceptibility effects. The presence of blooming effect within the appendix virtually excludes acute appendicitis (7).

Identification of the blooming effect is crucial in differentiation between the normal appendix and pelvic venous varices in pregnancy. Pregnant women, particularly during their third trimester, can develop extensive varices. These veins appear as tubular hypointense structures on T1-weighted and single-shot fast SE images, an appearance identical to that of the normal appendix. Distinction between these two structures can be very challenging. Thorough comparison of the axial single-shot fast SE and TOF images allows differentiation between the normal appendix and venous varices. Pelvic varices demonstrate high signal intensity on TOF images due to the presence of flow, whereas the normal appendix filled with air or oral contrast material remains of low signal intensity on both TOF and single-shot fast SE images and shows the characteristic blooming effect (7) (Fig 2).

View larger version (130K): [in this window] [in a new window] [Download PPT slide]   Figure 2a.  Usefulness of oral contrast material and TOF imaging in evaluation of the normal appendix during pregnancy in a 31-year-old woman who was 30 weeks pregnant and had RLQ pain and nausea. (a) Axial T2-weighted single-shot fast SE image of the gravid abdomen shows the cecum (C) and terminal ileum (*). A possible normal appendix (arrow) is seen posterior to the cecum. However, other tubular hypointense structures (arrowheads) with a similar appearance are seen medial to the psoas muscle. (b) Axial TOF GRE image obtained at the same level shows the characteristic enlargement and decreased signal intensity of the appendix (arrow), the so-called blooming effect, which is caused by the susceptibility effect of air or the iron-based oral contrast medium within its lumen. Note the same effect in the cecum (C) and terminal ileum (*). This phenomenon virtually excludes appendicitis. TOF images are also essential in differentiating the common periovarian varices (arrowheads) with very high signal intensity from the hypointense appendix; this distinction cannot be made on the single-shot fast SE images alone.

View larger version (117K): [in this window] [in a new window] [Download PPT slide]   Figure 2b.  Usefulness of oral contrast material and TOF imaging in evaluation of the normal appendix during pregnancy in a 31-year-old woman who was 30 weeks pregnant and had RLQ pain and nausea. (a) Axial T2-weighted single-shot fast SE image of the gravid abdomen shows the cecum (C) and terminal ileum (*). A possible normal appendix (arrow) is seen posterior to the cecum. However, other tubular hypointense structures (arrowheads) with a similar appearance are seen medial to the psoas muscle. (b) Axial TOF GRE image obtained at the same level shows the characteristic enlargement and decreased signal intensity of the appendix (arrow), the so-called blooming effect, which is caused by the susceptibility effect of air or the iron-based oral contrast medium within its lumen. Note the same effect in the cecum (C) and terminal ileum (*). This phenomenon virtually excludes appendicitis. TOF images are also essential in differentiating the common periovarian varices (arrowheads) with very high signal intensity from the hypointense appendix; this distinction cannot be made on the single-shot fast SE images alone.

	Appendiceal Disorders

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction MR Imaging Protocols Normal Appendix Appendiceal Disorders Other Disorders Arising from... Obstetric and Gynecologic... Urinary Tract Disorders Conclusions References

View larger version (93K): [in this window] [in a new window] [Download PPT slide]   Figure 3.  Appendicitis in a 33-year-old woman who was 17 weeks pregnant and had RLQ pain and fever. Axial T2-weighted single-shot fast SE image of the lower abdomen shows the cecum (C) and terminal ileum (TI). The appendix (arrow) is identified posterior to the cecum. The appendix is enlarged (8-mm diameter) and thick walled and its lumen is filled with high-signal-intensity fluid, whereas the cecum and terminal ileum are completely filled with negative oral contrast material. The MR imaging findings were consistent with early appendicitis, which was confirmed at surgery.

View larger version (119K): [in this window] [in a new window] [Download PPT slide]   Figure 4a.  Mild acute appendicitis in a 20-year-old woman who was 10 weeks pregnant and had RLQ pain. C = cecum. (a) Sagittal T2-weighted single-shot fast SE image of the right lower abdomen shows the cecum tilted superiorly. Located just beneath the cecum is the appendix (arrows). Note that the cecum is completely filled with negative contrast material, as opposed to the high-signal-intensity lumen of the appendix. The appendiceal wall is visible, but the appendix is not dilated. (b) Sagittal fat-saturated T2-weighted single-shot fast SE image obtained at the same level shows increased signal intensity in the periappendiceal fat (arrows), a finding that confirms the presence of acute inflammation. Mild acute appendicitis was found at surgery and pathologic analysis.

View larger version (144K): [in this window] [in a new window] [Download PPT slide]   Figure 4b.  Mild acute appendicitis in a 20-year-old woman who was 10 weeks pregnant and had RLQ pain. C = cecum. (a) Sagittal T2-weighted single-shot fast SE image of the right lower abdomen shows the cecum tilted superiorly. Located just beneath the cecum is the appendix (arrows). Note that the cecum is completely filled with negative contrast material, as opposed to the high-signal-intensity lumen of the appendix. The appendiceal wall is visible, but the appendix is not dilated. (b) Sagittal fat-saturated T2-weighted single-shot fast SE image obtained at the same level shows increased signal intensity in the periappendiceal fat (arrows), a finding that confirms the presence of acute inflammation. Mild acute appendicitis was found at surgery and pathologic analysis.

View larger version (159K): [in this window] [in a new window] [Download PPT slide]   Figure 5.  Acute appendicitis in a 25-year-old woman who was 16 weeks pregnant and had RLQ pain and leukocytosis. Axial T2-weighted single-shot fast SE image of the right midabdomen shows the appendix (black arrowhead), which is curved medially, arising from the base of the cecum (C). Note the high signal intensity within the appendiceal lumen and that the appendix is dilated. A rounded area of low signal intensity (arrow) in the proximal appendix is noted; this area represents an appendicolith. Periappendiceal fat stranding is seen as a bandlike area of high signal intensity (white arrowheads) in the adjacent fat. The MR imaging findings were consistent with acute appendicitis, which was confirmed at surgery and pathologic analysis.

View larger version (119K): [in this window] [in a new window] [Download PPT slide]   Figure 6.  Appendiceal phlegmon in a 29-year-old woman who was 27 weeks pregnant and had RLQ pain. Sagittal T2-weighted single-shot fast SE image of the right hemiabdomen shows a heterogeneous moderately hyperintense mass (arrows) in the RLQ with mass effect on the cecum (C), an appearance consistent with a phlegmon. Note that the right ovary (arrowhead) is displaced anteriorly. The patient was treated with intravenous antibiotics, and follow-up MR imaging at 32 weeks showed resolution of the phlegmon with a persistent abnormally dilated appendix. The patient underwent cesarean section and appendectomy, which confirmed the diagnosis of perforated appendicitis.

Postsurgical inflammation at the base of the appendiceal remnant, the so-called stump appendicitis, is a rare event (20). An increased risk of this complication after laparoscopic appendectomy due to incomplete resection of the base of the appendix has been reported (21,22). The time of clinical presentation may be variable, with cases reported from 3 months to 21 years after appendectomy (23). CT findings may be similar to those present in acute appendicitis (ie, enhancing tubular structure arising from the cecum with adjacent fat stranding) if the appendiceal stump left after appendectomy is long (24). CT may also demonstrate a pericecal phlegmon or abscess, as well as thickening of the cecal wall with oral contrast material insinuating into the expected location of the appendiceal origin, the so-called arrowhead sign (25). Phlegmon, abscess formation, and wall thickening in the cecum are also visible at MR imaging (5).

An appendiceal mucocele is a rare entity that accounts for 0.25% of appendectomies (26,27). The clinical presentation and imaging findings can mimic acute appendicitis. Appendiceal mucoceles may be caused by different underlying conditions, and the result is a dilated, fluid- or mucus-filled appendix. Four histologic subtypes, ranging from benign to malignant processes, have been described: postobstructive mucous retention cyst, mucosal hyperplasia (resembling a hyperplastic polyp), mucinous cystadenoma (resembling an adenomatous polyp), and invasive mucinous cystadenocarcinoma (26,28–30). Most appendiceal mucoceles are found incidentally or due to chronic RLQ abdominal pain. Acute RLQ pain may occur secondary to perforation of the appendix. Appendiceal mucoceles may rupture, causing spillage of the mucinous contents into the peritoneal cavity or pseudomyxoma peritonei, which can be focal or diffuse (28,29).

The mucinous contents within the mucocele have high signal intensity on T2-weighted images. Although a fluid-filled appendix may be seen in both acute appendicitis and appendiceal mucoceles, the former typically has associated wall thickening and periappendiceal inflammation. In general, the degree of distention of the appendix in patients with mucoceles is disproportionate to the amount of appendiceal wall thickening and periappendiceal inflammation, with the exception of those in whom the mucocele is ruptured (Fig 7). Enlargement of the appendix beyond 15 mm in diameter should be viewed with suspicion, and careful attention should be paid to other findings that may indicate the presence of a neoplasm (31). In the presence of an appendiceal cystadenoma or cystadenocarcinoma, a focal mass may be seen at cross-sectional imaging.

View larger version (150K): [in this window] [in a new window] [Download PPT slide]   Figure 7a.  Ruptured appendiceal mucocele in a 72-year-old man with right-sided pelvic pain and abnormal appearance of the appendix at prior CT performed at another institution. (a) Coronal T2-weighted single-shot fast SE image shows the cecum (C), normal terminal ileum (black arrowheads), and bladder (B). A thick-walled appendix (arrow) is present, surrounded by an irregularly shaped fluid collection (white arrowheads). (b) Axial T2-weighted fast SE image shows cystic dilatation of the appendiceal tip (*) and periappendiceal free fluid (arrowheads), findings suggestive of a ruptured appendiceal mucocele. A ruptured mucocele secondary to an appendiceal cystadenoma was found at surgery and pathologic analysis.

View larger version (134K): [in this window] [in a new window] [Download PPT slide]   Figure 7b.  Ruptured appendiceal mucocele in a 72-year-old man with right-sided pelvic pain and abnormal appearance of the appendix at prior CT performed at another institution. (a) Coronal T2-weighted single-shot fast SE image shows the cecum (C), normal terminal ileum (black arrowheads), and bladder (B). A thick-walled appendix (arrow) is present, surrounded by an irregularly shaped fluid collection (white arrowheads). (b) Axial T2-weighted fast SE image shows cystic dilatation of the appendiceal tip (*) and periappendiceal free fluid (arrowheads), findings suggestive of a ruptured appendiceal mucocele. A ruptured mucocele secondary to an appendiceal cystadenoma was found at surgery and pathologic analysis.

	Other Disorders Arising from the Gastrointestinal Tract

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction MR Imaging Protocols Normal Appendix Appendiceal Disorders Other Disorders Arising from... Obstetric and Gynecologic... Urinary Tract Disorders Conclusions References

MR imaging allows exquisite visualization of the small and large bowel. Patients with inflammatory bowel disease (eg, Crohn disease and ulcerative colitis) presenting with acute RLQ pain can be adequately evaluated with MR imaging. Bowel wall edema is readily appreciated on T2-weighted single-shot fast SE images as a band of increased signal intensity within the wall thickness. Superior sensitivity of MR imaging compared with that of CT has been reported for detection of early and mild forms of inflammatory bowel disease (32). The degree of wall enhancement on gadolinium-enhanced images and the degree of high signal intensity on fat-saturated T2-weighted images correlate with disease activity (33,34).

Pelvic and perineal complications of Crohn disease including enteroenteric and enterovesical fistulas or abscesses can be accurately seen at MR imaging (35). MR imaging findings in patients with RLQ pain secondary to an acute flare of Crohn disease are variable depending on the stage of the disease. Mild acute inflammation usually manifests as mild thickening of the small bowel (particularly the terminal ileum) or colon. Prominence, dilatation, and tortuosity of the vasa recta coursing through proliferative mesenteric fat, the so-called comb sign, can be readily appreciated at MR imaging (Fig 8). However, similar findings can be seen in patients with other forms of ileitis (eg, infectious). An inflammatory phlegmon can be seen as a soft-tissue mass of intermediate signal intensity on T1-weighted images and mild increased signal intensity on T2-weighted images (better appreciated with fat saturation techniques). Frank increased signal intensity on T2-weighted images typically represents liquefaction within an abscess (Fig 9).

View larger version (130K): [in this window] [in a new window] [Download PPT slide]   Figure 8a.  Crohn disease in a 26-year-old woman with RLQ pain and fever. (a) Axial T2-weighted fast SE image of the lower abdomen shows marked mural thickening in the distal ileum (arrows) with a layer of increased signal intensity suggestive of submucosal edema. There is prominence, dilatation, and tortuosity of the vasa recta coursing through proliferative mesenteric fat, the comb sign (arrowheads). (b) Axial gadolinium-enhanced 3D fat-saturated T1-weighted GRE image obtained at the same level shows marked mural enhancement (arrows) in the abnormal loop of distal ileum. Linear areas of low signal intensity in the wall correspond to the edema in the bowel wall. The comb sign is better appreciated with gadolinium contrast material (arrowheads). These findings are consistent with an acute flare of Crohn disease.

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 8b.  Crohn disease in a 26-year-old woman with RLQ pain and fever. (a) Axial T2-weighted fast SE image of the lower abdomen shows marked mural thickening in the distal ileum (arrows) with a layer of increased signal intensity suggestive of submucosal edema. There is prominence, dilatation, and tortuosity of the vasa recta coursing through proliferative mesenteric fat, the comb sign (arrowheads). (b) Axial gadolinium-enhanced 3D fat-saturated T1-weighted GRE image obtained at the same level shows marked mural enhancement (arrows) in the abnormal loop of distal ileum. Linear areas of low signal intensity in the wall correspond to the edema in the bowel wall. The comb sign is better appreciated with gadolinium contrast material (arrowheads). These findings are consistent with an acute flare of Crohn disease.

View larger version (135K): [in this window] [in a new window] [Download PPT slide]   Figure 9a.  Abscess in a 59-year-old man with a history of Crohn disease who presented with fever, chills, and lower abdominal pain. (a) Axial T2-weighted fast SE image shows a thick-walled fluid collection (arrows) in the left hemipelvis, adjacent to the sigmoid colon (arrowheads). (b) Axial gadolinium-enhanced 3D fat-saturated T1-weighted GRE image obtained during the delayed venous phase shows peripheral rim and septal enhancement of the fluid collection (arrows). The sigmoid colon is again visualized (arrowheads). The diagnosis of an abscess related to Crohn disease was confirmed with percutaneous drainage of the fluid collection.

View larger version (128K): [in this window] [in a new window] [Download PPT slide]   Figure 9b.  Abscess in a 59-year-old man with a history of Crohn disease who presented with fever, chills, and lower abdominal pain. (a) Axial T2-weighted fast SE image shows a thick-walled fluid collection (arrows) in the left hemipelvis, adjacent to the sigmoid colon (arrowheads). (b) Axial gadolinium-enhanced 3D fat-saturated T1-weighted GRE image obtained during the delayed venous phase shows peripheral rim and septal enhancement of the fluid collection (arrows). The sigmoid colon is again visualized (arrowheads). The diagnosis of an abscess related to Crohn disease was confirmed with percutaneous drainage of the fluid collection.

View larger version (143K): [in this window] [in a new window] [Download PPT slide]   Figure 10a.  Small bowel obstruction in a 34-year-old woman with a history of ulcerative colitis and prior total colectomy who was 19 weeks pregnant and presented with nausea, vomiting, and abdominal pain. (a) Coronal T2-weighted single-shot fast SE image of the abdomen and pelvis shows the gravid uterus with the placenta (P). There is diffuse dilatation of fluid-filled loops of small bowel. Well-circumscribed areas of high signal intensity surround the bowel (arrows) and conform to the borders of the abdominal wall, a finding indicative of free fluid. (b) Sagittal T2-weighted single-shot fast SE image of the RLQ shows the dilated, fluid-filled small bowel loops. The patient’s ostomy (large arrowhead) is collapsed, and the end ileal loop (arrow) tapers abruptly to the ostomy; these findings indicate the transition point of the small bowel obstruction caused by stenosis at the level of the os-tomy. The free fluid is seen beneath the small bowel loops (small arrowhead). The small bowel obstruction was relieved after placement of a catheter and dilation of the ostomy.

View larger version (135K): [in this window] [in a new window] [Download PPT slide]   Figure 10b.  Small bowel obstruction in a 34-year-old woman with a history of ulcerative colitis and prior total colectomy who was 19 weeks pregnant and presented with nausea, vomiting, and abdominal pain. (a) Coronal T2-weighted single-shot fast SE image of the abdomen and pelvis shows the gravid uterus with the placenta (P). There is diffuse dilatation of fluid-filled loops of small bowel. Well-circumscribed areas of high signal intensity surround the bowel (arrows) and conform to the borders of the abdominal wall, a finding indicative of free fluid. (b) Sagittal T2-weighted single-shot fast SE image of the RLQ shows the dilated, fluid-filled small bowel loops. The patient’s ostomy (large arrowhead) is collapsed, and the end ileal loop (arrow) tapers abruptly to the ostomy; these findings indicate the transition point of the small bowel obstruction caused by stenosis at the level of the ostomy. The free fluid is seen beneath the small bowel loops (small arrowhead). The small bowel obstruction was relieved after placement of a catheter and dilation of the ostomy.

View larger version (108K): [in this window] [in a new window] [Download PPT slide]   Figure 11a.  Cecal pneumatosis in a 47-year-old diabetic woman with fever and abdominal pain 2 months after pancreatic transplantation. She had undergone renal transplantation 5 years before this admission. (a) Axial T2-weighted single-shot fast SE image of the lower abdomen shows an air-fluid level in the lumen of the cecum (black arrowhead). A curvilinear area of low signal intensity that conforms to the wall of the cecum (arrows) represents pneumatosis. Part of the cecal wall appears as a thin line of intermediate signal intensity (white arrowhead) that separates the luminal air from the pneumatosis. (b) Axial gadolinium-enhanced 3D fat-saturated T1-weighted GRE image of the upper abdomen, obtained during the portal venous phase, shows lack of signal within the left portal vein (arrow) due to air in the portal vein. (c) Unenhanced CT scan shows the cecal pneumatosis (arrows) and cecal wall thickening (arrowhead); CT also showed the air in the left portal vein. At surgery, a perforated diverticulum was found in the cecum.

View larger version (140K): [in this window] [in a new window] [Download PPT slide]   Figure 11b.  Cecal pneumatosis in a 47-year-old diabetic woman with fever and abdominal pain 2 months after pancreatic transplantation. She had undergone renal transplantation 5 years before this admission. (a) Axial T2-weighted single-shot fast SE image of the lower abdomen shows an air-fluid level in the lumen of the cecum (black arrowhead). A curvilinear area of low signal intensity that conforms to the wall of the cecum (arrows) represents pneumatosis. Part of the cecal wall appears as a thin line of intermediate signal intensity (white arrowhead) that separates the luminal air from the pneumatosis. (b) Axial gadolinium-enhanced 3D fat-saturated T1-weighted GRE image of the upper abdomen, obtained during the portal venous phase, shows lack of signal within the left portal vein (arrow) due to air in the portal vein. (c) Unenhanced CT scan shows the cecal pneumatosis (arrows) and cecal wall thickening (arrowhead); CT also showed the air in the left portal vein. At surgery, a perforated diverticulum was found in the cecum.

View larger version (154K): [in this window] [in a new window] [Download PPT slide]   Figure 11c.  Cecal pneumatosis in a 47-year-old diabetic woman with fever and abdominal pain 2 months after pancreatic transplantation. She had undergone renal transplantation 5 years before this admission. (a) Axial T2-weighted single-shot fast SE image of the lower abdomen shows an air-fluid level in the lumen of the cecum (black arrowhead). A curvilinear area of low signal intensity that conforms to the wall of the cecum (arrows) represents pneumatosis. Part of the cecal wall appears as a thin line of intermediate signal intensity (white arrowhead) that separates the luminal air from the pneumatosis. (b) Axial gadolinium-enhanced 3D fat-saturated T1-weighted GRE image of the upper abdomen, obtained during the portal venous phase, shows lack of signal within the left portal vein (arrow) due to air in the portal vein. (c) Unenhanced CT scan shows the cecal pneumatosis (arrows) and cecal wall thickening (arrowhead); CT also showed the air in the left portal vein. At surgery, a perforated diverticulum was found in the cecum.

	Obstetric and Gynecologic Disorders

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction MR Imaging Protocols Normal Appendix Appendiceal Disorders Other Disorders Arising from... Obstetric and Gynecologic... Urinary Tract Disorders Conclusions References

 
The female reproductive tract gives rise to a multitude of pathologic conditions that can manifest as acute RLQ pain. Most important, some of these entities may require surgical intervention, including ectopic pregnancy and ovarian torsion.

Ovarian Disorders
Hemorrhagic cysts are a very common cause of RLQ pain, frequently resulting from rupture into the peritoneal cavity. Hemorrhage may be seen in both functional and corpus luteum cysts. The signal intensity of the cyst varies depending on the age of the hemorrhage. Subacute hemorrhage (deoxyhemoglobin) is of intermediate signal intensity on T1-weighted images and low signal intensity on T2-weighted images. Later, the presence of intracellular methemoglobin causes increased signal intensity on T1-weighted images and decreased signal intensity on T2-weighted images. Layering blood products within the dependent portion of the cyst, the so-called hematocrit effect, can be seen on both T1- and T2-weighted images.

Pelvic endometriosis is another cause of RLQ pain. Endometriosis is defined as the presence of endometrial tissue outside the uterus. The most common location of ectopic endometrial tissue is the ovaries (37). Hormonal stimulation of the endometrial tissue causes enlargement and hemorrhage with subsequent formation of endometrial cysts (endometriomas) (37). MR imaging findings that suggest the diagnosis of endometrial cysts include homogeneous high signal intensity (equal to or greater than that of fat) on T1-weighted images; areas of decreased signal intensity or "shading" effect on T2-weighted images (usually mixed with areas of high signal intensity) in cysts that exhibit high signal intensity on T1-weighted images; and multiplicity (more than two cysts with increased signal intensity at T1-weighted imaging that adhere to each other) (37) (Fig 12). The shading effect is likely caused by the presence of high-viscosity contents, high protein concentration, and/or high iron concentration within the fluid (37,38).

View larger version (144K): [in this window] [in a new window] [Download PPT slide]   Figure 12a.  Endometriosis in a 37-year-old woman with RLQ pain and a right adnexal mass at US. (a) Axial T1-weighted GRE image shows two lesions (arrows) with homogeneous high signal intensity in the pelvis. (b) Sagittal T2-weighted fast SE image shows heterogeneous decreased or low signal intensity (shading) in the two lesions (arrows), which are located immediately superior to the uterus (U). Gadolinium-enhanced MR imaging showed no enhancement within the lesions. Endometriomas were confirmed at surgery and pathologic analysis.

View larger version (168K): [in this window] [in a new window] [Download PPT slide]   Figure 12b.  Endometriosis in a 37-year-old woman with RLQ pain and a right adnexal mass at US. (a) Axial T1-weighted GRE image shows two lesions (arrows) with homogeneous high signal intensity in the pelvis. (b) Sagittal T2-weighted fast SE image shows heterogeneous decreased or low signal intensity (shading) in the two lesions (arrows), which are located immediately superior to the uterus (U). Gadolinium-enhanced MR imaging showed no enhancement within the lesions. Endometriomas were confirmed at surgery and pathologic analysis.

Ovarian torsion occurs as a result of twisting of the ovary around its vascular pedicle, leading to ischemia. An ovarian lesion serves as the leading point in the majority of cases. Ovarian or paraovarian cysts are the most common lesions encountered in these patients. The ovarian cysts can be physiologic or neoplastic, with the most common neoplasm leading to torsion being a dermoid (43). Other conditions that may lead to ovarian torsion include ovarian hyperstimulation syndrome, abscesses, and malignant neoplasms (44). Ovarian torsion is occasionally seen in pregnancy.

MR imaging findings in ovarian torsion vary depending on the stage of the disease. Initially, there is ovarian enlargement caused by stromal edema, which is appreciated as diffuse high signal intensity on T2-weighted images (45). Fat saturation techniques improve the detection of ovarian edema on T2-weighted images (Fig 13). In the presence of a mass, detection of edema in the ovarian stroma may be challenging (45). Increased signal intensity of the ovarian stroma is an early sign, and a viable ovary is frequently found at surgery in these patients (45). As torsion progresses, the signal intensity in the ovary is variable due to the presence of hemorrhage and necrosis. Decreased signal intensity on T1- and T2-weighted images indicates hemorrhagic infarction (46).

View larger version (106K): [in this window] [in a new window] [Download PPT slide]   Figure 13a.  Ovarian torsion in a 31-year-old woman who was 30 weeks pregnant and had RLQ pain and nausea. US showed a mildly enlarged right ovary with normal arterial and venous flow. (a) Axial T2-weighted single-shot fast SE image of the right pelvis shows a mildly enlarged right ovary with areas of increased signal intensity in its stroma (arrow), findings consistent with edema. (b) On an axial fat-saturated T2-weighted single-shot fast SE image obtained at the same level, the high signal intensity within the ovarian stroma (*) caused by edema is seen more clearly. Note the peripherally located follicles, which appear prominent due to the stromal edema. A small amount of fluid is also present surrounding the ovary (arrowheads); this fluid was not appreciated without fat saturation. These MR imaging findings are characteristic of ovarian torsion, and the diagnosis was confirmed at surgery.

View larger version (139K): [in this window] [in a new window] [Download PPT slide]   Figure 13b.  Ovarian torsion in a 31-year-old woman who was 30 weeks pregnant and had RLQ pain and nausea. US showed a mildly enlarged right ovary with normal arterial and venous flow. (a) Axial T2-weighted single-shot fast SE image of the right pelvis shows a mildly enlarged right ovary with areas of increased signal intensity in its stroma (arrow), findings consistent with edema. (b) On an axial fat-saturated T2-weighted single-shot fast SE image obtained at the same level, the high signal intensity within the ovarian stroma (*) caused by edema is seen more clearly. Note the peripherally located follicles, which appear prominent due to the stromal edema. A small amount of fluid is also present surrounding the ovary (arrowheads); this fluid was not appreciated without fat saturation. These MR imaging findings are characteristic of ovarian torsion, and the diagnosis was confirmed at surgery.

View larger version (108K): [in this window] [in a new window] [Download PPT slide]   Figure 14a.  Ovarian torsion in a 29-year-old woman who was 9 weeks pregnant. (a) Coronal fat-saturated T2-weighted single-shot fast SE image shows enlargement and increased signal intensity of the right fallopian tube (large arrow) due to edema. The right ovary is enlarged (arrowhead), and its stroma is hyperintense relative to that of the left ovary (small arrow). Note the multiple fibroids (*) in the gravid uterus. (b) Axial fat-saturated T2-weighted single-shot fast SE image shows enlargement and increased signal intensity of the right fallopian tube (arrowheads). A twisted configuration of the right ovarian vascular pedicle (arrow) is appreciated within the edematous tube. * = fibroid. Ovarian torsion was confirmed at surgery.

View larger version (79K): [in this window] [in a new window] [Download PPT slide]   Figure 14b.  Ovarian torsion in a 29-year-old woman who was 9 weeks pregnant. (a) Coronal fat-saturated T2-weighted single-shot fast SE image shows enlargement and increased signal intensity of the right fallopian tube (large arrow) due to edema. The right ovary is enlarged (arrowhead), and its stroma is hyperintense relative to that of the left ovary (small arrow). Note the multiple fibroids (*) in the gravid uterus. (b) Axial fat-saturated T2-weighted single-shot fast SE image shows enlargement and increased signal intensity of the right fallopian tube (arrowheads). A twisted configuration of the right ovarian vascular pedicle (arrow) is appreciated within the edematous tube. * = fibroid. Ovarian torsion was confirmed at surgery.

Ovarian hyperstimulation syndrome occurs as a result of ovulation induction. Although up to 65% of patients undergoing ovulation induction have a mild form of this condition, the rare severe presentations require hospitalization. Patients present with pelvic pain, ascites, and bilateral ovarian enlargement with multiple cysts (48). Cysts with increased signal intensity are commonly seen secondary to hemorrhage (48). The prevalence of ovarian torsion is increased in patients with ovarian hyperstimulation syndrome (49). The clinical assessment of hyperstimulated patients with pelvic pain can be difficult. MR imaging can be helpful by showing the increased signal intensity of the ovarian stroma secondary to edema on T2-weighted images (Fig 15).

View larger version (126K): [in this window] [in a new window] [Download PPT slide]   Figure 15.  Ovarian torsion in ovarian hyperstimulation syndrome after ovulation induction in a 31-year-old woman who was 11 weeks pregnant and presented with acute RLQ pain. Axial fat-saturated T2-weighted fast SE image of the lower pelvis shows the cervix (white arrowhead) and rectum (R). Both ovaries are visible anteriorly and are enlarged with multiple follicles (black arrowheads). These findings are consistent with ovarian hyperstimulation syndrome, which was known to be present clinically. Note the asymmetrical enlargement of the right ovary, which also demonstrates a subtle increase in signal intensity of the stroma (*). A small amount of fluid is seen between the two ovaries (arrow). Although the right ovary had arterial and venous flow at Doppler US, the MR imaging find-ings were consistent with right ovarian torsion, which was confirmed at laparotomy.

View larger version (172K): [in this window] [in a new window] [Download PPT slide]   Figure 16a.  Ruptured ovarian dermoid cyst in a 59-year-old woman with pelvic pain. (a) Axial T2-weighted fast SE image shows an enlarged uterus (U) and a right adnexal mass (*). A moderate amount of free intraperitoneal fluid (black arrowheads) is seen as high signal intensity tracking posteriorly from the adnexal mass. There is thickening of the posterior peritoneum (white arrowhead). An exophytic nodule (arrow) is seen arising from the adnexal mass. Note the chemical shift artifact (black and white lines at the anterior and posterior margins of the nodule, respectively) between the nodule and the surrounding free fluid, a finding that suggests the presence of fat. (b, c) Axial in-phase (b) and opposed-phase (c) T1-weighted GRE images obtained at the same level show the intermediate-signal-intensity mass in the right adnexa (* in b). The exophytic nodule is seen as an ovoid area of high signal intensity (arrow). A thin hypointense rim (India ink artifact) is seen around the nodule on the opposed-phase image (arrow in c); this artifact is characteristically seen on opposed-phased images at the interface of bulk fat and water. The presence of bulk fat within an adnexal mass is virtually pathognomonic of an ovarian dermoid cyst. A ruptured ovarian dermoid cyst causing chemical peritonitis was found intraoperatively and at histologic analysis. U in b = uterus.

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 16b.  Ruptured ovarian dermoid cyst in a 59-year-old woman with pelvic pain. (a) Axial T2-weighted fast SE image shows an enlarged uterus (U) and a right adnexal mass (*). A moderate amount of free intraperitoneal fluid (black arrowheads) is seen as high signal intensity tracking posteriorly from the adnexal mass. There is thickening of the posterior peritoneum (white arrowhead). An exophytic nodule (arrow) is seen arising from the adnexal mass. Note the chemical shift artifact (black and white lines at the anterior and posterior margins of the nodule, respectively) between the nodule and the surrounding free fluid, a finding that suggests the presence of fat. (b, c) Axial in-phase (b) and opposed-phase (c) T1-weighted GRE images obtained at the same level show the intermediate-signal-intensity mass in the right adnexa (* in b). The exophytic nodule is seen as an ovoid area of high signal intensity (arrow). A thin hypointense rim (India ink artifact) is seen around the nodule on the opposed-phase image (arrow in c); this artifact is characteristically seen on opposed-phased images at the interface of bulk fat and water. The presence of bulk fat within an adnexal mass is virtually pathognomonic of an ovarian dermoid cyst. A ruptured ovarian dermoid cyst causing chemical peritonitis was found intraoperatively and at histologic analysis. U in b = uterus.

View larger version (131K): [in this window] [in a new window] [Download PPT slide]   Figure 16c.  Ruptured ovarian dermoid cyst in a 59-year-old woman with pelvic pain. (a) Axial T2-weighted fast SE image shows an enlarged uterus (U) and a right adnexal mass (*). A moderate amount of free intraperitoneal fluid (black arrowheads) is seen as high signal intensity tracking posteriorly from the adnexal mass. There is thickening of the posterior peritoneum (white arrowhead). An exophytic nodule (arrow) is seen arising from the adnexal mass. Note the chemical shift artifact (black and white lines at the anterior and posterior margins of the nodule, respectively) between the nodule and the surrounding free fluid, a finding that suggests the presence of fat. (b, c) Axial in-phase (b) and opposed-phase (c) T1-weighted GRE images obtained at the same level show the intermediate-signal-intensity mass in the right adnexa (* in b). The exophytic nodule is seen as an ovoid area of high signal intensity (arrow). A thin hypointense rim (India ink artifact) is seen around the nodule on the opposed-phase image (arrow in c); this artifact is characteristically seen on opposed-phased images at the interface of bulk fat and water. The presence of bulk fat within an adnexal mass is virtually pathognomonic of an ovarian dermoid cyst. A ruptured ovarian dermoid cyst causing chemical peritonitis was found intraoperatively and at histologic analysis. U in b = uterus.

Previous ectopic pregnancy, tubal surgery, in utero exposure to diethylstilbestrol, and assisted reproductive technology are the risk factors more strongly associated with ectopic pregnancy (53,54). Pelvic inflammatory disease and current smoking have also been associated with an increased risk for ectopic pregnancy (54). The most common location of implantation is the ampullary portion and isthmus of the fallopian tube (55). US remains the standard of care in the initial evaluation of pregnant patients in whom ectopic pregnancy is suspected. MR imaging has been proposed as a complementary imaging modality in selected patients in whom the clinical suspicion is high (ie, high-risk patients, infertility treatment) and the US findings are inconclusive. In these circumstances, MR imaging can help achieve a prompt diagnosis, which can contribute to the decision to use nonsurgical therapy (ie, methotrexate) (56).

A tubal hematoma (hematosalpinx) of intermediate signal intensity on T1-weighted images and low signal intensity on T2-weighted images is the most common MR finding in patients with ectopic pregnancy (56). Identification of a para-ovarian gestational sac–like structure in the adnexa supports the diagnosis. However, this finding is seen only in the minority of patients (56). In the presence of hemoperitoneum, free fluid of intermediate signal intensity greater than that of urine can be appreciated on T1-weighted images (56). MR imaging findings must be interpreted with caution, as there is potential overlap in the appearance of ectopic pregnancy with those of tubal endometriosis and hemorrhagic corpus luteum cysts.

The fallopian tube can also serve as a source for acute RLQ pain in cases of hydrosalpinx, tubal endometriosis, or tubo-ovarian abscess. Isolated fallopian tube torsion is a rare cause of acute RLQ pain (57,58). The preoperative diagnosis is frequently delayed due to the rarity of this condition. Underlying conditions affecting the tube may predispose to this condition, although torsion may also affect a previously healthy tube (57). Delay in diagnosis may lead to necrosis, infection, and peritonitis (57). US may demonstrate a hydrosalpinx or a paraovarian cyst (59). MR imaging findings include wall thickening of the distended fallopian tube, better appreciated on T2-weighted fast SE images. A swirled configuration of the tube away from the normal-appearing ovary can suggest the diagnosis (Fig 17).

View larger version (169K): [in this window] [in a new window] [Download PPT slide]   Figure 17a.  Isolated fallopian tube torsion in a 28-year-old woman with severe right-sided pelvic pain. A perirectal cyst was seen at endovaginal US. B = bladder. (a) Sagittal T2-weighted fast SE image shows a normal right ovary (black arrowhead) with a cyst (arrow) seen posteroinferiorly. A small amount of free fluid (white arrowhead) is seen above the ovary. (b) Sagittal T2-weighted fast SE image obtained slightly medial to a shows a cyst (*) in the posterior pelvis and a moderate amount of free fluid (arrow). On sequential images, the posterior pelvic cyst was clearly separate from the ovarian cyst. An area of intermediate to high signal intensity (arrowheads) is seen anterior to the tubal cyst with linear areas of low signal intensity in a swirled pattern. (c) Coronal oblique T2-weighted fast SE image of the midpelvis shows the normal uterus (black arrow) resting above the bladder. The right ovarian cyst (white arrow) is seen. Note the swirled appearance of the adnexal tissue (arrowheads) between the right ovary and uterus. At surgery, the paratubal cyst and right fallopian tube were twisted three times. The paratubal cyst was excised, and the tube was found to be viable after detorsion.

View larger version (176K): [in this window] [in a new window] [Download PPT slide]   Figure 17b.  Isolated fallopian tube torsion in a 28-year-old woman with severe right-sided pelvic pain. A perirectal cyst was seen at endovaginal US. B = bladder. (a) Sagittal T2-weighted fast SE image shows a normal right ovary (black arrowhead) with a cyst (arrow) seen posteroinferiorly. A small amount of free fluid (white arrowhead) is seen above the ovary. (b) Sagittal T2-weighted fast SE image obtained slightly medial to a shows a cyst (*) in the posterior pelvis and a moderate amount of free fluid (arrow). On sequential images, the posterior pelvic cyst was clearly separate from the ovarian cyst. An area of intermediate to high signal intensity (arrowheads) is seen anterior to the tubal cyst with linear areas of low signal intensity in a swirled pattern. (c) Coronal oblique T2-weighted fast SE image of the midpelvis shows the normal uterus (black arrow) resting above the bladder. The right ovarian cyst (white arrow) is seen. Note the swirled appearance of the adnexal tissue (arrowheads) between the right ovary and uterus. At surgery, the paratubal cyst and right fallopian tube were twisted three times. The paratubal cyst was excised, and the tube was found to be viable after detorsion.

View larger version (170K): [in this window] [in a new window] [Download PPT slide]   Figure 17c.  Isolated fallopian tube torsion in a 28-year-old woman with severe right-sided pelvic pain. A perirectal cyst was seen at endovaginal US. B = bladder. (a) Sagittal T2-weighted fast SE image shows a normal right ovary (black arrowhead) with a cyst (arrow) seen posteroinferiorly. A small amount of free fluid (white arrowhead) is seen above the ovary. (b) Sagittal T2-weighted fast SE image obtained slightly medial to a shows a cyst (*) in the posterior pelvis and a moderate amount of free fluid (arrow). On sequential images, the posterior pelvic cyst was clearly separate from the ovarian cyst. An area of intermediate to high signal intensity (arrowheads) is seen anterior to the tubal cyst with linear areas of low signal intensity in a swirled pattern. (c) Coronal oblique T2-weighted fast SE image of the midpelvis shows the normal uterus (black arrow) resting above the bladder. The right ovarian cyst (white arrow) is seen. Note the swirled appearance of the adnexal tissue (arrowheads) between the right ovary and uterus. At surgery, the paratubal cyst and right fallopian tube were twisted three times. The paratubal cyst was excised, and the tube was found to be viable after detorsion.

Rapid growth, torsion, or degeneration may be the cause of abdominal pain due to fibroids in pregnancy. Patients may present with focal pain, tenderness on palpation, low-grade fever, and leukocytosis. The diagnosis can typically be made with sonography by demonstrating point tenderness when the probe is over the fibroid. In those cases where direct assessment with US is not possible (ie, deep location within the pelvis), MR imaging can be helpful in making the diagnosis. Diffuse or peripheral high signal intensity at T1-weighted imaging and variable signal intensity at T2-weighted imaging are typically present in fibroids undergoing hemorrhagic degeneration during pregnancy (60). Diffuse increased signal intensity of uterine fibroids on T2-weighted images is caused by edema and may antedate degeneration (61) (Fig 18).

View larger version (135K): [in this window] [in a new window] [Download PPT slide]   Figure 18.  Acute degeneration of a fibroid in a 28-year-old woman who was 17 weeks pregnant and had progressive RLQ pain. US showed a mass in the RLQ at the point of maximum tenderness. The right ovary was not seen. MR imaging was performed in an attempt to differentiate between ovarian disease and an exophytic fibroid. Axial fat-saturated single-shot fast SE image shows the gravid uterus and placenta (P). An exophytic round mass (arrowheads) with a broad base of attachment to the right side of the uterus is seen and demonstrates diffuse high signal intensity due to edema. A focal area of very high signal intensity (arrow) within the mass is indicative of necrosis. The MR imaging findings are typical of acute degeneration in an exophytic fibroid. The patient’s symptoms improved with conservative treatment.

View larger version (120K): [in this window] [in a new window] [Download PPT slide]   Figure 19a.  Acute degeneration of fibroids after cesarean section in a 38-year-old woman with acute onset of pelvic pain, fever, and leukocytosis. (a) Axial 3D fat-saturated T1-weighted GRE image of the upper pelvis shows three areas of increased signal intensity (arrows) within the enlarged uterus, findings suggestive of red (hemorrhagic) degeneration of uterine fibroids. (b) Axial subtracted (postcontrast minus precontrast) 3D fat-saturated T1-weighted GRE image obtained at the same level shows lack of enhancement in the three fibroids (*). Acute degeneration of fibroids after cesarean section can cause post-partum pelvic pain and fever, which can mimic a postoperative abscess. The patient’s symptoms improved with conservative treatment.

View larger version (101K): [in this window] [in a new window] [Download PPT slide]   Figure 19b.  Acute degeneration of fibroids after cesarean section in a 38-year-old woman with acute onset of pelvic pain, fever, and leukocytosis. (a) Axial 3D fat-saturated T1-weighted GRE image of the upper pelvis shows three areas of increased signal intensity (arrows) within the enlarged uterus, findings suggestive of red (hemorrhagic) degeneration of uterine fibroids. (b) Axial subtracted (postcontrast minus precontrast) 3D fat-saturated T1-weighted GRE image obtained at the same level shows lack of enhancement in the three fibroids (*). Acute degeneration of fibroids after cesarean section can cause post-partum pelvic pain and fever, which can mimic a postoperative abscess. The patient’s symptoms improved with conservative treatment.

View larger version (125K): [in this window] [in a new window] [Download PPT slide]   Figure 20a.  Dilated gonadal vein in a 27-year-old woman who was 29 weeks pregnant and presented with RLQ pain. (a) Axial 2D TOF GRE image of the midabdomen shows a moderately enlarged right gonadal vein (black arrow) and periovarian venous varices (arrowheads). Note the normal appendix (white arrow) with low signal intensity due to air or oral contrast material in its lumen. (b) Sagittal T2-weighted single-shot fast SE image shows moderate right hydronephrosis with dilatation of the renal pelvis (white arrow). Note the extrinsic compression of the proximal ureter (arrowhead) by the enlarged gonadal vein (black arrow). It is unclear if the gonadal vein was the cause of or contributed to the patient’s symptoms, which improved after delivery.

View larger version (104K): [in this window] [in a new window] [Download PPT slide]   Figure 20b.  Dilated gonadal vein in a 27-year-old woman who was 29 weeks pregnant and presented with RLQ pain. (a) Axial 2D TOF GRE image of the midabdomen shows a moderately enlarged right gonadal vein (black arrow) and periovarian venous varices (arrowheads). Note the normal appendix (white arrow) with low signal intensity due to air or oral contrast material in its lumen. (b) Sagittal T2-weighted single-shot fast SE image shows moderate right hydronephrosis with dilatation of the renal pelvis (white arrow). Note the extrinsic compression of the proximal ureter (arrowhead) by the enlarged gonadal vein (black arrow). It is unclear if the gonadal vein was the cause of or contributed to the patient’s symptoms, which improved after delivery.

	Urinary Tract Disorders

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction MR Imaging Protocols Normal Appendix Appendiceal Disorders Other Disorders Arising from... Obstetric and Gynecologic... Urinary Tract Disorders Conclusions References

Patients with acute obstruction demonstrate increased perirenal fluid on T2-weighted images, most likely due to lymphatic congestion or forniceal rupture (73). Although this finding suggests acute obstruction, perirenal fluid can be secondary to any insult to the kidney and should be considered a nonspecific sign (72,73).

Ureteral patency can be inferred by the presence of a ureteral jet at Doppler US, although it does not exclude the presence of a nonobstructive stone. Transvaginal US is helpful in identification of stones at the ureterovesical junction. MR imaging can help in determining the level of obstruction. Hydronephrosis related to pregnancy can be easily recognized at MR imaging, as the dilated ureter is extrinsically compressed between the gravid uterus and psoas muscle at the level of the sacral promontory. In our experience, as well as in others’ (74), dilatation distal to the sacral promontory should raise suspicion for obstruction (ie, ureterovesical junction stone).

Care should be taken to not mistake flow artifact central in the ureter with a stone on T2-weighted single-shot fast SE images. This can be done by reviewing images in multiple planes when a ureteral stone is suspected. Fast imaging with a steady-state precession technique (eg, true FISP [Siemens Medical Solutions, Malvern, Pa], FIESTA [GE Healthcare, Waukesha, Wis], balanced FFE [Philips Medical Systems, Andover, Mass]) may be used to identify stones in the distal ureter. A 3D version of a steady-state precession sequence allows improved signal-to-noise ratio and multiplanar reformation to facilitate recognition of the stone (Fig 21).

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 21a.  Distal ureterolithiasis in a 39-year-old woman who was 11 weeks pregnant and had right-sided abdominal pain. US showed right hydronephrosis and a calculus in the distal ureter. MR imaging was performed due to worsening symptoms. (a) Sagittal fat-saturated T2-weighted single-shot fast SE image shows hydronephrosis (arrow) and extensive retroperitoneal fluid (arrowheads) around the right kidney, an appearance suggestive of forniceal rupture. (b) Coronal reformatted image from axial 3D fast imaging with steady-state acquisition shows a filling defect (arrow) in the distal right ureter (arrowheads), a finding consistent with a ureteral calculus. B = bladder. The patient’s symptoms resolved after ureteroscopy with basket extraction of the calculus followed by placement of a double-J stent.

View larger version (69K): [in this window] [in a new window] [Download PPT slide]   Figure 21b.  Distal ureterolithiasis in a 39-year-old woman who was 11 weeks pregnant and had right-sided abdominal pain. US showed right hydronephrosis and a calculus in the distal ureter. MR imaging was performed due to worsening symptoms. (a) Sagittal fat-saturated T2-weighted single-shot fast SE image shows hydronephrosis (arrow) and extensive retroperitoneal fluid (arrowheads) around the right kidney, an appearance suggestive of forniceal rupture. (b) Coronal reformatted image from axial 3D fast imaging with steady-state acquisition shows a filling defect (arrow) in the distal right ureter (arrowheads), a finding consistent with a ureteral calculus. B = bladder. The patient’s symptoms resolved after ureteroscopy with basket extraction of the calculus followed by placement of a double-J stent.

	Conclusions

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction MR Imaging Protocols Normal Appendix Appendiceal Disorders Other Disorders Arising from... Obstetric and Gynecologic... Urinary Tract Disorders Conclusions References

 
MR imaging is an excellent alternative to CT in those patients in whom the use of iodinated contrast media or radiation is not desirable. Furthermore, MR imaging is an excellent adjunct to US in pregnant patients with RLQ pain in whom the results of the US examination are inconclusive. Radiologists should become familiar with the MR imaging technique, advantages, and unique features of MR imaging for evaluating patients with acute RLQ pain.

	Footnotes

 

Abbreviations: GRE = gradient echo, RLQ = right lower quadrant, SE = spin echo, 3D = three-dimensional, TOF = time of flight, 2D = two-dimensional

See the commentary by Katz et al following this article.

	References

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