(Radiographics. 2001;21:799-824.)
© RSNA, 2001
Intravenous Urography: Technique and Interpretation1
Raymond B. Dyer, MD,
Michael Y. M. Chen, MD and
Ronald J. Zagoria, MD
1 From the Department of Radiology, Wake Forest University School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157-1088. Recipient of a Certificate of Merit award for an education exhibit at the 2000 RSNA scientific assembly. Received January 9, 2001; revision requested January 23 and received February 20; accepted February 28. Address correspondence to R.B.D. (e-mail: rdyer@wfubmc.edu).
Index Terms: Genitourinary system, diseases, 80.20, 80.30, 80.81, 80.84 • Ureter, stenosis or obstruction, 82.843, 82.844 • Urography, 80.11, 80.12
 |
LEARNING OBJECTIVES FOR TEST 1
|
|---|
After reading this article and taking the test, the reader will be able to:
- Describe proper intravenous urographic technique.
- List the rules of urographic interpretation.
- Apply the rules of urographic interpretation to the evaluation of urinary tract disease.
Intravenous urography has long been the cornerstone of the imaging evaluation of urinary tract disease. However, other imaging modalities such as ultrasonography, computed tomography, and magnetic resonance imaging are being used with increasing frequency. The declining use of urography in clinical practice presents a challenge for instruction in urographic technique and interpretation. In addition, alternative modalities also have their limitations, and despite their increasing use, the ideal "global" urinary tract examination remains controversial. Nevertheless, urography may still be important in the diagnosis of some urinary tract disease processes. It is frequently performed in the evaluation of hematuria. Urography may also be performed in the pre- or posttherapeutic evaluation of stone disease that has been discovered with other imaging modalities. The urographic imaging sequence is designed to optimize depiction of specific portions of the urinary tract during maximal contrast material opacification, and a tailored urographic study may provide diagnostic detail beyond the current capabilities of other imaging modalities. However, this can be accomplished only with good technique, an understanding of the limitations of the procedure, and adherence to basic rules of interpretation. The ability to relate urographic findings of disease processes to other imaging modalities will remain an important skill until the ideal urinary tract imaging technique emerges.
|
Introduction
|
|---|
For decades, intravenous urography has been the primary imaging modality for evaluation of the urinary tract. In recent years, however, other imaging modalities including ultrasonography (US), computed tomography (CT), and magnetic resonance (MR) imaging have been used with increasing frequency to compensate for the limitations of intravenous urography in the evaluation of urinary tract disease (1). Like intravenous urography, however, these examinations have their limitations. Large portions of the urinary tract are not visualized at US; CT requires contrast material administration and excretory images (at times with a prolonged delay), often with image reformatting for evaluation of the urothelium; and MR imaging may not demonstrate calcifications or show the urothelium with sufficient resolution for evaluation of subtle abnormalities. Thus, despite increasing use of these alternative modalities, the ideal "global" urinary tract examination remains controversial (1,2). Axial imaging with contrast material opacification of the urinary tract will likely evolve as the most efficient imaging evaluation. However, the declining use of intravenous urography in clinical practice reduces the opportunity to learn important interpretive skills. Formal urography (or the urographic equivalent of conventional radiography of the urinary tract following administration of contrast material for CT) is frequently performed in the evaluation of hematuria. Urography may also be performed in the pre- or posttherapeutic evaluation of stone disease that has been discovered with other modalities. In our opinion, CT with digital and reformatted images does not provide sufficient anatomic detail for evaluation of subtle uroepithelial neoplasms or other collecting system disease (3).
In this article, we discuss and illustrate basic urographic technique, review the rules of urographic interpretation, and discuss the importance of applying these rules to the interpretation of findings seen at other imaging modalities.
|
Standard Intravenous Urography
|
|---|
Like any other imaging study, intravenous urography should ideally be tailored to answer a specific clinical question (4,5). Our standard procedure for intravenous urography with optional images is outlined in the Table (6–10).
The preliminary kidney, ureter, bladder (KUB) radiograph is an indispensable part of the sequence. This image should be obtained with appropriate technique (65–75 kVp, high milliam-perage, short exposure time) to maximize inherent soft-tissue contrast and optimize visualization of calcium-containing lesions that are potentially of urinary tract origin (8). "Proper" KUB radiography may require additional images for evaluating portions of the urinary tract not seen on the standard 14 x 17-inch image. Imaging should encompass the area from the suprarenal region to a level below the symphysis pubis (Fig 1) (8). The patient should void immediately prior to undergoing this examination.
View larger version (158K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 1. Urethral calculus in a patient with a recent history of severe right flank pain. Collimated radiograph demonstrates a calcification centered over the anatomic pelvis, behind the symphysis (arrow). This was the only calcification that was identified. CT helped confirm the presence of the urethral calculus. This case demonstrates the importance of full coverage of anatomic structures at KUB radiography.
|
|
An assessment of the probable location of calcifications in the abdomen with respect to the urinary tract should be made prior to the injection of contrast material, which can obscure a calcification (Fig 2). Oblique conventional radiographs may be extremely helpful in ascertaining the position and nature of calcifications. This is especially important when a patient has flank pain but no obvious urinary tract calculus is seen on the KUB radiograph (the complex anatomy of the sacrum may obscure even sizable calculi) (Fig 3). Although the evaluation of flank pain with unenhanced CT has lessened the need for this study, these techniques may be important when conventional radiography is used for follow-up.
View larger version (129K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 2a. Calculus. (a) Urogram demonstrates no significant dilatation of the collecting system, with subtle changes in the opacified ureter. (b) Preliminary radiograph shows an 8-mm calculus in the ureter (arrow). This case demonstrates how a calculus can be obscured by contrast material.
|
|
View larger version (138K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 2b. Calculus. (a) Urogram demonstrates no significant dilatation of the collecting system, with subtle changes in the opacified ureter. (b) Preliminary radiograph shows an 8-mm calculus in the ureter (arrow). This case demonstrates how a calculus can be obscured by contrast material.
|
|
View larger version (153K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 3a. Calculus in a patient with right flank pain. (a) Collimated preliminary radiograph of the pelvis shows no obvious stones. (b) Right posterior oblique radiograph of the pelvis shows a 6-mm ureteral calculus now projected onto the iliac bone (arrow). A urogram (not shown) helped confirm right ureteral obstruction secondary to the stone. This case shows how a calculus can be obscured by the complex sacral anatomy.
|
|
View larger version (151K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 3b. Calculus in a patient with right flank pain. (a) Collimated preliminary radiograph of the pelvis shows no obvious stones. (b) Right posterior oblique radiograph of the pelvis shows a 6-mm ureteral calculus now projected onto the iliac bone (arrow). A urogram (not shown) helped confirm right ureteral obstruction secondary to the stone. This case shows how a calculus can be obscured by the complex sacral anatomy.
|
|
In patients who are to undergo nephrotomography after contrast material administration, a preliminary nephrotomogram is obtained. We use the following formula to determine our preliminary tomographic level (11–13): (anteroposterior abdominal diameter [cm] x 
) - 2 cm. On the basis of the appearance of the kidney on this image, adjustment of the levels to be obtained following contrast material administration can be made. Additional conventional tomograms may be obtained prior to the injection of contrast material in patients being evaluated for urinary tract stone disease. The preliminary images should always be reviewed for findings that may indicate urinary tract disease and with the intention of detecting other abdominal processes that might be mistaken for findings having a urinary tract origin (Fig 4).
View larger version (151K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 4. Emphysematous pyelonephritis in a patient who was referred for urography for left flank pain. Preliminary radiograph reveals striated gas within the renal parenchyma as well as a large perirenal gas collection that extends into the retroperitoneum surrounding the adrenal gland. A finding of emphysematous pyelonephritis does not require further imaging, but urgent intervention.
|
|
A review of contrast materials and of the physiology of urinary excretion is not within the scope of this article, but excellent references are available (6,14–18). Contrast materials currently in use are excreted almost exclusively by glomerular filtration, with subsequent concentration in the postglomerular nephron and progressive opacification of the urinary tract. The urographic imaging sequence is designed to optimize depiction of specific portions of the urinary tract during maximal contrast material opacification.
In virtually all new patients, we perform nephrotomography following the bolus administration of contrast material for optimal renal parenchymal visualization. Urographic nephrograms are produced primarily by filtered contrast material within the nephron, with optimal visualization of the renal parenchyma 1–3 minutes after bolus injection (19). The tomographic levels are determined on the basis of the scout tomographic findings as described earlier. Linear tomography performed with a 20° arc allows coverage of most kidneys in three images separated by 1 or 2 cm. It is imperative that the entire renal outline be visualized for optimal mass detection. Nephrotomography is always performed after contrast material administration in patients with hematuria when a mass is a consideration, in patients who are poorly prepared, and for optimal assessment of the renal parenchyma. A standard radiograph collimated to the kidneys may be sufficient in young patients when obstruction is the specific issue, when repeat urography is performed shortly after a study that included tomography, or when the kidneys have been evaluated with other cross-sectional modalities and are without known parenchymal abnormality. If a kidney is not evident within the renal fossa at initial tomography, a KUB radiograph obtained during the nephrographic phase may demonstrate a nephrogram in an ectopic location. Masses that project from the anterior or posterior aspect of the kidney but do not produce distortion of the renal outline at lin-ear tomography may be overlooked. In such cases, oblique radiographs or oblique nephrotomograms may be of added benefit if findings allow lateralization.
A KUB radiograph is obtained 5 minutes after the administration of contrast material to assess temporal symmetry and progress of opacification. Compression, an essential part of optimal urographic technique (especially when low-osmolar contrast material is used), is then applied unless there is a specific contraindication (20,21). We prefer using a device that can be placed around the patient rather than one that is attached to the imaging table. The ureters are compressed against the sacrum as the ureter traverses the sacral ala (Fig 5). Contraindications for the use of abdominal compression include evidence of obstruction on the 5-minute image, abdominal aortic aneurysm or some other abdominal mass, recent abdominal surgery or severe abdominal pain, suspected urinary tract trauma, and presence of urinary diversion or a renal transplant (22).
View larger version (131K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 5a. Value of compression. (a) On a radiograph obtained 5 minutes after administration of low-osmolar urographic contrast material, the collecting system is bilaterally underfilled and poorly demonstrated. (b) On a radiograph obtained 5 minutes after compression was applied, distention of the collecting system is significantly improved (arrows).
|
|
View larger version (132K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 5b. Value of compression. (a) On a radiograph obtained 5 minutes after administration of low-osmolar urographic contrast material, the collecting system is bilaterally underfilled and poorly demonstrated. (b) On a radiograph obtained 5 minutes after compression was applied, distention of the collecting system is significantly improved (arrows).
|
|
An image collimated to the kidneys for evaluation of the renal calices and collecting systems is obtained 5 minutes after the compression device is applied (23). This is especially important when low-osmolar contrast material is used because the osmotic diuresis and ultimate distention of the collecting system may not be as great as with high-osmolar materials. For optimal evaluation of the ureters and pelvocaliceal systems, oblique images or repeat tomograms (20° arc, thick sections) may be helpful (Fig 6). Compression images obtained after an even greater delay can sometimes provide additional information.
View larger version (148K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6a. Value of oblique imaging. (a) Ten-minute anteroposterior radiograph of the right kidney obtained with compression suggests a filling defect within the right interpolar collecting system (arrow). (b) Steep right posterior oblique radiograph demonstrates that the filling defect is caused by a posterior papillary tip (arrow).
|
|
View larger version (150K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6b. Value of oblique imaging. (a) Ten-minute anteroposterior radiograph of the right kidney obtained with compression suggests a filling defect within the right interpolar collecting system (arrow). (b) Steep right posterior oblique radiograph demonstrates that the filling defect is caused by a posterior papillary tip (arrow).
|
|
Imaging during early bladder filling may be important in the assessment of patients with suspected bladder disease. With low-osmolar contrast materials, delayed bladder filling due to minimal osmotic diuresis may necessitate imaging during compression to prevent the opacity of contrast material in the bladder from becoming too great for adequate assessment.
Release of compression allows delivery of a bolus of concentrated contrast material into the ureters. We obtain a KUB radiograph immediately following compression release (15 minutes after contrast material administration) and supplement this image with fluoroscopic spot images to ensure that the entire luminal surface of the ureters has been imaged (Fig 7) (6,24,25). If fluoroscopy is not available, oblique KUB radiographs can be obtained for this purpose. In addition, it should be remembered that contrast material–opacified urine is heavier than nonopacified urine. Gravity maneuvers such as imaging with the patient in the prone or dependent oblique position often assist with visualization of unopacified portions of the ureters, especially in cases of obstruction (26). In such cases, delayed images should be obtained until opacification to the level of obstruction is identified or until it is determined that renal excretion is insufficient for adequate opacification.
If the bladder is sufficiently distended and opacified, it may be adequately evaluated on previously obtained images. If, however, there is specific concern for bladder disease, delayed images may be obtained to improve bladder distention, and oblique, prone, or postvoid images may be obtained to evaluate filling defects (Fig 8) (27).
View larger version (128K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 8a. Collapsed bladder. (a) On a radiograph obtained during bladder filling, the contrast material is smoothly defined and the bladder wall has become less evident. A normal uterine impression on the superior margin is noted. (b) Postvoid radiograph shows a normal collapsed bladder with mucosal ridges less than 3 mm in width.
|
|
View larger version (134K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 8b. Collapsed bladder. (a) On a radiograph obtained during bladder filling, the contrast material is smoothly defined and the bladder wall has become less evident. A normal uterine impression on the superior margin is noted. (b) Postvoid radiograph shows a normal collapsed bladder with mucosal ridges less than 3 mm in width.
|
|
|
Urographic Interpretation
|
|---|
The renal parenchyma is optimally assessed during the nephrographic phase of urography. The entire renal contour should be assessed, and nephrotomography almost always affords better visualization than standard imaging. The renal contour should be smooth, and the inability to visualize a given portion of the contour requires explanation. There should be temporal symmetry of the nephrographic development (5). Nephrographic evolution requires adequate renal blood flow, normal parenchymal excretory function without obstruction, and normal venous outflow (Figs 9, 10) (5,19). The size of the kidneys should be assessed on every urogram, and this is best performed during the nephrographic phase. There is inherent magnification in conventional radiography compared with other imaging modalities. The normal kidney may range from 9 to 13 cm in cephalocaudal length, with the left kidney inherently larger than the right by 0.5 cm and the kidneys slightly larger in men than in women (7,28–30). Several methods of assessing renal size have been reported, but approximate symmetry should be anticipated. Significant discrepancies (right kidney 
1.5 cm larger than the left kidney, left kidney 2 cm larger than the right kidney) require explanation (Figs 11, 12).
View larger version (107K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 9a. Abnormal nephrographic evolution. (a) Final image of a tomographic sequence demonstrates symmetric nephrograms and pyelograms. Renal size is normal. (b) On a 10-minute image, no pyelogram is evident. The nephrograms are persistent, and the kidneys are smaller. With this imaging sequence alteration, the patient should be evaluated immediately for the development of hypotension related to the procedure or as a reaction to contrast material administration.
|
|
View larger version (93K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 9b. Abnormal nephrographic evolution. (a) Final image of a tomographic sequence demonstrates symmetric nephrograms and pyelograms. Renal size is normal. (b) On a 10-minute image, no pyelogram is evident. The nephrograms are persistent, and the kidneys are smaller. With this imaging sequence alteration, the patient should be evaluated immediately for the development of hypotension related to the procedure or as a reaction to contrast material administration.
|
|
View larger version (108K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 10a. Abnormal nephrographic evolution. (a) One-minute image shows slight asymmetry of the nephrographic opacity, with less opacity in the right kidney than in the left. (b) Image obtained at 80 minutes shows a persistent, very dense right nephrogram, a typical finding in acute high-grade obstruction. A 2-mm stone was discovered at the right ureterovesical junction.
|
|
View larger version (104K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 10b. Abnormal nephrographic evolution. (a) One-minute image shows slight asymmetry of the nephrographic opacity, with less opacity in the right kidney than in the left. (b) Image obtained at 80 minutes shows a persistent, very dense right nephrogram, a typical finding in acute high-grade obstruction. A 2-mm stone was discovered at the right ureterovesical junction.
|
|
View larger version (100K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 11a. Right renal artery stenosis. (a) Fourth nephrotomogram from a "minute sequence" urogram (performed in the past for evaluation of renovascular hypertension) shows a small right kidney with decreased nephrographic density and temporal asymmetry of filling of the right collecting system compared with the left. (b) Fifteen-minute urographic image helps confirm the asymmetric renal size. Note the hyperconcentration of contrast material in the right collecting system compared with the left.
|
|
View larger version (100K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 11b. Right renal artery stenosis. (a) Fourth nephrotomogram from a "minute sequence" urogram (performed in the past for evaluation of renovascular hypertension) shows a small right kidney with decreased nephrographic density and temporal asymmetry of filling of the right collecting system compared with the left. (b) Fifteen-minute urographic image helps confirm the asymmetric renal size. Note the hyperconcentration of contrast material in the right collecting system compared with the left.
|
|
View larger version (120K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 12. Enlarged kidneys in a young patient with early, asymmetric findings of autosomal dominant polycystic kidney disease. Nephrotomogram shows enlarged kidneys, the left more so than the right. Note the multiple parenchymal defects ("Swiss cheese" nephrogram).
|
|
Contour abnormalities can be associated with a change in parenchymal thickness, which should always be interpreted with regard to the appearance of the underlying renal collecting system. It is often helpful to draw the "interpapillary line" to aid in the evaluation of parenchymal thickness (Fig 13) (31). Parenchymal thickness averages 3–3.5 cm in the polar regions and 2–2.5 cm in the interpolar regions. Indentations or increased parenchymal thickness may be a reflection of congenital anatomic variation (5,7,22,32). These anomalies tend to occur in predictable locations (Figs 14, 15). A decrease in parenchymal thickness with an underlying abnormal caliceal configuration may reflect postinflammatory (Fig 16) or stone-related scarring, whereas parenchymal loss that occurs between the calices without underlying caliceal distortion may be secondary to renal infarction. Increased parenchymal thickness associated with underlying caliceal distortion is more typical of masses (Fig 17). Absence of nephrographic enhancement within the lesion suggests a simple cyst (Fig 18) (22). A build-up of parenchyma at the margins of a lesion (parenchymal "beaking"), once considered a sign of a simple cyst, reflects only the slow growth of the lesion within the parenchyma and can be seen with both benign and malignant renal masses (Fig 19). Masses may also produce a "double contour" at tomography, an often overlooked finding (Fig 20). Urographic detection of masses requires further cross-sectional imaging for confirmation of the benign or malignant nature of the process. US is preferred when urographic findings suggest a cyst, whereas CT is recommended when the findings suggest a solid lesion.
View larger version (24K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 13. Normal interpapillary line. Drawing illustrates how the renal outline should be closely paralleled by a line connecting the papillary tips (dotted line). Deviations from this pattern require explanation.
|
|
View larger version (125K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 14. Normal indentation. Nephrotomogram shows an indentation at the junction of the middle and lower aspects of the kidney (sulcus interpartialis inferior) (arrow). A similar indentation may occur at the junction of the upper and middle portions of the kidney (sulcus interpartialis superior). Indentations in the renal contour frequently reflect persistent fetal renal anatomy.
|
|
View larger version (113K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 15. Normal "increased" parenchymal thickness. Nephrotomogram shows prominent cortical tissue (arrowheads), a finding that can also reflect normal fetal renal anatomy. Typical areas of prominence include the hilar lips, cortical columns (usually seen at the junction of the upper and middle thirds of the kidney), and other "humps" that should be reflected in the interpapillary line.
|
|
View larger version (116K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 17. Renal cell carcinoma. Nephrotomogram shows a mass in the midportion of the left kidney (arrows) producing increased parenchymal thickness and distorting the collecting system.
|
|
View larger version (123K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 18. Simple cyst. Nephrotomogram shows a nephrographic defect in the midportion of the left kidney (arrow) with increased parenchymal thickness and distortion of the underlying collecting system. US helped confirm a simple cyst.
|
|
View larger version (154K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 19. Simple cyst. Nephrotomogram shows build-up of normal parenchymal tissue (cortical "beaking") at the margins of an unenhanced mass in the lower pole of the left kidney (arrows). The lesion was confirmed to be a simple cyst at US.
|
|
View larger version (132K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 20. Renal cell carcinoma. Nephrotomogram shows a double contour within the kidney (arrows). This finding may easily be overlooked but can be an important observation. CT helped confirm the presence of a solid mass projecting from the posterior aspect of the kidney and accounting for the double contour. This was surgically proved to represent a renal cell carcinoma.
|
|
The position of the kidney should also be assessed at nephrotomography. A portion of each upper renal pole usually extends above the 12th rib, with the right kidney normally slightly lower than the left due to the position of the liver. The vertical axis of the kidney should parallel the upper one-third of the psoas muscle. Alterations in axis and position may occur as a response to abdominal or retroperitoneal masses, alterations in visceral size, or congenital renal anomalies related to position or fusion (Fig 21).
View larger version (118K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 21. Axis and position alteration. Nephrotomogram demonstrates characteristic axis alteration associated with a horseshoe kidney. Horseshoe kidney is also associated with positional and rotational anomalies. Anomalous collecting system morphologic features and drainage are associated with an increased prevalence of infection, stone formation, and urothelial tumors. (Reprinted, with permission, from reference 33.)
|
|
On the 5-minute image, the nephrogram should be receding as the collecting system becomes opacified. On the 10-minute image, the pyelogram is the dominant urographic element. Alterations in this temporal sequence require explanation (34). Visualization of the collecting system and renal pelvis can be augmented with the use of abdominal compression, the Trendelenburg position, and other gravity maneuvers such as placing the patient with the side of interest in the ipsilateral posterior oblique position. The appearance of the calices and renal pelvis should be examined closely because intravenous urography is the most accurate imaging modality for visualizing the urothelium-lined surfaces and evaluating potential abnormalities (transitional cell carcinoma, mucosal striations, pyelitis cystica).
Compound papillae are likely to occur in the polar regions, whereas simple papillae with the classic chalice appearance of the calix and acutely angulated forniceal margins are usually seen in the interpolar region. Early and mild obstruction is indicated by subtle rounding of the forniceal margins (Fig 22), with increasingly more severe and prolonged obstruction evidenced by progressive loss of the papillary impression and eventual clubbing of calices. The recognition of contrast material within the papillae may reflect a continuum from papillary blush through benign tubular ectasia to medullary sponge kidney (Figs 23–25) (5,7,19). Larger parenchymal collections of contrast material may reflect an inflammatory process such as tuberculosis, changes of papillary necrosis (Figs 26, 27), or neoplastic excavation related to transitional cell carcinoma. Contrast material–filled outpouchings from the collecting system may represent abortive calices or collecting system diverticula (Fig 28) (35). Because a diverticulum must fill via its communication with the collecting system, opacification is often delayed. Filling defects within the calices or collecting system are also an important finding (Figs 29, 30). Aberrant papillae may produce disconcerting findings and can be confused with other causes of radiolucent filling defects within the collecting system or renal pelvis, the most important of which is transitional cell carcinoma (Fig 31) (5). Parenchymal or renal sinus structures and pathologic processes may be reflected in impressions on the collecting system elements (Fig 32).
View larger version (111K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 22. Caliceal obstruction in a patient with a left distal ureteral stone who presented with acute flank pain. Nephrotomogram shows rounded left-sided caliceal fornices, whereas those on the right side have an acute angular appearance. Fullness of the collecting system and proximal ureter is also seen.
|
|
View larger version (96K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 23a. Papillary blush. (a) Early urographic image shows prominent papillary opacity but no resolvable tubular structures in the region of the papillae. (b) Ten-minute image obtained with compression shows a decrease in the prominence of the papillary opacity, a finding that is typical of papillary blush. A further decrease in papillary opacity is often seen on later images following compression release.
|
|
View larger version (106K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 23b. Papillary blush. (a) Early urographic image shows prominent papillary opacity but no resolvable tubular structures in the region of the papillae. (b) Ten-minute image obtained with compression shows a decrease in the prominence of the papillary opacity, a finding that is typical of papillary blush. A further decrease in papillary opacity is often seen on later images following compression release.
|
|
View larger version (118K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 24. Tubular ectasia in a patient with microscopic hematuria. Image of the left kidney obtained with compression shows resolvable linear striations in virtually all papillae. A retrograde pyelogram obtained later (not shown) showed no filling of the tubules, implying an intact antireflux mechanism. It is anticipated that other pathologic causes of papillary excavation would be identified at the time of retrograde pyelography.
|
|
View larger version (117K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 25. Medullary sponge kidney. Urographic image shows resolvable collections of contrast material in the papillary tips. Stones that were evident within the papillae at preliminary radiography appeared to "enlarge" as the cavities filled with contrast material during urography ("growing calculus sign"), a finding that is indicative of medullary sponge kidney.
|
|
View larger version (138K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 26. Papillary necrosis due to sickle cell anemia. Pyelographic-phase urographic image demonstrates a long extension of contrast material from the fornices into the renal substance in the upper (black arrow) and lower (white arrow) poles.
|
|
View larger version (141K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 27. Papillary necrosis caused by analgesic abuse. Pyelographic image shows central cavities within multiple papillae (arrows). (Figs 26 and 27 reprinted, with permission, from reference 33.)
|
|
View larger version (155K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 28a. Caliceal diverticulum. (a) Preliminary image demonstrates clustered calcifications in the upper pole of the right kidney. (b) Urographic pyelogram shows slowed temporal filling of a large cavity in communication with, but peripheral to, the uppermost calix, a finding that is consistent with a caliceal diverticulum.
|
|
View larger version (130K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 28b. Caliceal diverticulum. (a) Preliminary image demonstrates clustered calcifications in the upper pole of the right kidney. (b) Urographic pyelogram shows slowed temporal filling of a large cavity in communication with, but peripheral to, the uppermost calix, a finding that is consistent with a caliceal diverticulum.
|
|
View larger version (139K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 29. Oncocalix (tumor-filled calix) secondary to transitional cell carcinoma. Pyelographic image shows irregular filling in the caliceal structures of the upper pole of the left kidney (arrow).
|
|
View larger version (152K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 30. Transitional cell carcinoma in a patient with gross hematuria. Urographic image of the collecting system demonstrates a large papillary filling defect (arrow) with irregularity of the contrast material in the renal pelvis and proximal ureteral lumen. This proved to be a transitional cell carcinoma.
|
|
View larger version (137K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 31. Aberrant papilla in a patient with a history of transitional cell carcinoma. Tomography performed with compression for collecting system distention showed a filling defect in the middle infundibulum, suggesting an aberrant papilla. Oblique image helps confirm this urographic finding. Note the rim of contrast material at the margin of the somewhat angular defect (arrow). The benign nature of this finding was confirmed with nephroscopy.
|
|
View larger version (123K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 32a. Renal sinus cysts. (a) Longitudinal US image of the left kidney suggests hydronephrosis. Similar findings were seen in the right kidney. (b) Nephrotomogram obtained with compression shows narrowing and displacement of opacified collecting system elements and the renal pelvis bilaterally without hydronephrosis. This incongruity between US and urographic findings is typical of renal sinus cysts.
|
|
View larger version (97K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 32b. Renal sinus cysts. (a) Longitudinal US image of the left kidney suggests hydronephrosis. Similar findings were seen in the right kidney. (b) Nephrotomogram obtained with compression shows narrowing and displacement of opacified collecting system elements and the renal pelvis bilaterally without hydronephrosis. This incongruity between US and urographic findings is typical of renal sinus cysts.
|
|
In addition to aiding in the evaluation of parenchymal thickness, the interpapillary line is important in ensuring the presence of calices subtending all portions of the renal parenchyma. Lack of filling of a portion of the collecting system ("phantom calix") can be produced by benign or malignant processes (Fig 33). Although there is a tendency toward side-to-side symmetry in the number of calices (usually 7–14 calices), this is not always the case. This assessment is also helpful in determining the presence of a caliceal complement appropriate to the size of the kidney. The axis of the kidney should be reflected in the axis of the collecting system (Fig 34). There should be temporal symmetry in opacification and qualitatively equivalent contrast material opacity in the two collecting systems.
View larger version (114K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 33a. Tuberculosis. (a) Nephrotomogram shows decreased nephrographic opacity and nonfilling of the collecting system elements (phantom calices) in the lower pole of the left kidney. (b) Left retrograde pyelogram shows marked irregularity of the calices and infundibula in the left lower pole. Note the "moth-eaten" appearance of the calices. Urine samples obtained during this procedure were positive for urinary tract tuberculosis. Similar findings may be seen with an infiltrative process such as transitional cell carcinoma.
|
|
View larger version (126K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 33b. Tuberculosis. (a) Nephrotomogram shows decreased nephrographic opacity and nonfilling of the collecting system elements (phantom calices) in the lower pole of the left kidney. (b) Left retrograde pyelogram shows marked irregularity of the calices and infundibula in the left lower pole. Note the "moth-eaten" appearance of the calices. Urine samples obtained during this procedure were positive for urinary tract tuberculosis. Similar findings may be seen with an infiltrative process such as transitional cell carcinoma.
|
|
View larger version (132K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 34. Renal cell carcinoma. Pyelographic image shows the axis of the lower pole of the right kidney parallel to the margin of the psoas muscle and reversal of the normal axis of the collecting system. This finding indicates a mass in the upper pole of the right kidney. Note also the marked caliceal distortion, which is further proof that a mass (in this case, renal cell carcinoma) is present.
|
|
At the release of compression, the bolus of contrast material–laden urine entering the ureters provides optimal visualization throughout their length (25). Segmental nonvisualization of the ureter due to peristalsis can be overcome with compression release, and the entire ureter, filled from the ureteropelvic junction to the ureterovesi-cal junction, may be identified on one or two images. Persistence of a standing column of contrast material on several images may indicate obstruction (Fig 35) or ureteral ileus (nonobstructive dilatation related to inflammation). This finding should be interpreted in the context of other urographic findings. The ureter usually begins as a smooth extension from the renal pelvis lateral to the lateral margin of the psoas muscle. At about the L3 level, the ureter passes ventral to the muscle, crossing from lateral to medial (36). In its upper retroperitoneal course, the ureter passes along the outer half of the transverse processes of the upper lumbar vertebra. It crosses anterior to the iliac vasculature at a slightly higher position on the right than on the left. At the point of vascular crossover, there is often minimal medial deviation of the ureter. Once within the anatomic pelvis, the ureter typically parallels the inner margin of the iliac bone until it enters the bladder at the ureterovesical junction. Medial deviation of the ureter should be considered when the ureter overlies the ipsilateral lumbar pedicle (25,36,37). There is greater specificity if the ureter is seen medial to the pedicle. Separation of the ureters by less than 5 cm is also used as a criterion for medial deviation. As a general guideline, lateral deviation should be considered when the ureter lies more than 1 cm beyond the tip of the transverse process, but comparison with the position of the contralateral ureter should always be made (Fig 36). Any abrupt change in ureteral course requires explanation (Fig 37). Some ureteral deviations are characteristic (Fig 38) (25,31,36), whereas others, although they produce striking urographic images, represent normal variations (Fig 39). Because the ureter is highly mobile, determining the significance of ureteral deviation seen at urography often requires cross-sectional imaging.
View larger version (82K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 35. Collecting system dilatation. Fifteen-minute urographic image demonstrates a standing column of contrast material from the ureteropelvic junction to the ureterovesical junction on the right, a finding that is associated with mild collecting system dilatation. A stone is impacted at the ureterovesical junction. Note also the edema in the right side of the interureteric ridge (arrow), which is normally less than 3 mm in thickness.
|
|
View larger version (109K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 36. Ureteral deviation in a patient with diffuse abdominal pain. Urographic image shows lateral proximal and medial distal ureteral deviation. Note the positional and rotational abnormalities of the kidneys. The bladder is pear-shaped due to retroperitoneal and iliac chain lymphadenopathy. Splenomegaly with downward displacement of the left kidney is also seen.
|
|
View larger version (83K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 38. Circumcaval ureter. Urographic image shows the proximal right ureter with a "reversed J" appearance, a finding that is characteristic of circumcaval ureter. Associated moderate hydroureteronephrosis is also seen in this case.
|
|
View larger version (110K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 39. Psoas muscle hypertrophy. Urographic image shows the distal ureters centrally located and straightened bilaterally. Note the enlargement of the psoas muscles. There is also a slight alteration of the right renal axis and abrupt transition of the left midureter over the belly of the psoas muscle. These findings are typical of the ureteral position in patients with psoas muscle hypertrophy.
|
|
An absolute ureteral diameter exceeding 8 mm is considered by some authors to represent a criterion for dilatation (25). In general, asymmetry of ureteral caliber is a more significant finding. Early in its course, high-grade ureteral obstruction may be associated with only minimal ureteral dilatation. More chronic forms of obstruction and other chronic ureteral conditions are typically associated with greater degrees of ureteral dilatation (Figs 40, 41). Nonobstructive dilatation may occur as a result of high urine flow (fluid diuresis, diabetes insipidus), reflux, or inflammatory processes.
View larger version (115K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 40. Ureteral obstruction secondary to orthotopic ureterocele. Urographic image demonstrates the typical "cobra head" configuration of an orthotopic ureterocele in the bladder (arrow). Occasionally, such a ureterocele can be associated with obstructive changes—in this case, marked ureteral dilatation, columnization, and associated fullness of the collecting system.
|
|
View larger version (120K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 41. Primary megaureter. Late urographic image demonstrates tapered narrowing of the left ureter at the ureterovesical junction (arrow) associated with dilatation of the distal third of the ureter, with minimal upper urinary tract obstructive changes. These findings are typical of primary megaureter, but other causes of obstruction should be excluded with cystoscopy.
|
|
Familiarity with the normal appearance of peristalsis, areas of anatomic narrowing including the ureteropelvic junction and ureterovesical junction, and the iliac vascular transition is critical for accurate diagnosis of ureteral disease.
Impressions by gonadal veins may become quite prominent in females. Other causes of ureteral narrowing are generally categorized as either intrinsic or extrinsic to the ureteral wall (Figs 42, 43). Ureteral filling defects may be single or multiple and can usually be attributed to luminal, mural, or extrinsic causes (Fig 44). Care should be taken to visualize the entire luminal surface of the ureter, especially in patients with hematuria (Fig 45).
View larger version (161K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 42. Extrinsic vascular narrowing in a patient who had recently given birth. Urographic image shows prominent indentations (ureteral "notching") medially and laterally along the upper third of the left ureter (arrows). In this case, the finding was believed to be secondary to a prominent gonadal vein.
|
|
View larger version (138K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 43. Ureteral pseudodiverticula. An area of persistent narrowing in the distal ureter was identified at urography. Oblique image reveals that the area of narrowing is associated with small ureteral outpouchings (arrow). This finding is consisten | |
Top
LEARNING OBJECTIVES FOR TEST...
Introduction
