DOI: 10.1148/rg.244035149
RadioGraphics 2004;24:1117-1135
© RSNA, 2004
From the RSNA Refresher Courses
Imaging Evaluation for Acute Pain in the Right Upper Quadrant1
Anthony E. Hanbidge, MB, BCh, FRCPC,
Philip M. Buckler, MD,
Martin E. O’Malley, MD, FRCPC and
Stephanie R. Wilson, MD, FRCPC
1 From the Department of Medical Imaging, University Health Network and Mount Sinai Hospital, University of Toronto, Ontario, Canada. Presented as a refresher course at the 2002 RSNA scientific assembly. Received June 13, 2003; revision requested July 14 and received September 22; accepted September 23. All authors have no financial relationships to disclose. Address correspondence to A.E.H., Department of Medical Imaging, Toronto General Hospital, NCSB 1C-571, 585 University Ave, Toronto, ON, Canada M5G 2N2 (e-mail: anthony.hanbidge@uhn.on.ca).
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Abstract
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Acute cholecystitis is the most common cause of acute pain in the right upper quadrant (RUQ), and urgent surgical removal of the gallbladder is the treatment of choice for uncomplicated disease. However, cross-sectional imaging is essential because more than one-third of patients with acute RUQ pain do not have acute cholecystitis. In addition, patients with complications of acute cholecystitis, such as perforation, are often best treated with supportive measures initially and elective cholecystectomy at a later date. Ultrasound (US) is the primary imaging modality for assessment of acute RUQ pain; US is both sensitive and specific in demonstrating gallstones, biliary dilatation, and features that suggest acute inflammatory disease. Occasionally, additional imaging modalities are indicated. Computed tomography is valuable, especially for confirming the extent and nature of the complications of acute cholecystitis. Magnetic resonance cholangiopancreatography is helpful in complicated ductal disease (eg, recurrent pyogenic cholangiohepatitis) when more detailed diagnostic information is required for treatment planning, whereas endoscopic retrograde cholangiopancreatography is used when biliary intervention is required (eg, treatment of choledocholithiasis). Successful imaging with all modalities requires familiarity with both the characteristic and the unusual features of a wide variety of pathologic conditions. In addition, potential pitfalls must be recognized and avoided.
© RSNA, 2004
Index Terms: Aneurysm, hepatic, 952.73 • Bile ducts, calculi, 76.288 • Bile ducts, hemorrhage, 76.288 • Cholangitis, 76.288 • Cholecystitis, 762.285 Fistula, biliary, 762.284 • Gallbladder, perforation, 762.285 • Liver, abscess, 761.21 • Liver neoplasms, diagnosis, 761.319, 761.321
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LEARNING OBJECTIVES FOR TEST 5
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After reading this article and taking the test, the reader will be able to:
- Discuss the value of US in assessment of acute pain in the right upper quadrant.
- Identify the imaging features of acute cholecystitis and its complications.
- Describe additional pathologic conditions that can cause acute pain in the right upper quadrant when the gallbladder is normal.
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Introduction
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Patients presenting to the emergency department with abdominal pain localized to the right upper quadrant constitute a recognized patient population in whom acute cholecystitis is a prime diagnostic consideration. Although hepatobiliary disease in general and acute cholecystitis in particular may be the explanation for the patient’s symptoms, the clinical picture is often confusing and imaging is generally indicated early in an effort to reach a specific diagnosis. The primary treatment of acute cholecystitis is laparoscopic cholecystectomy. There is evidence that surgery in acute cholecystitis leads to better outcomes, and many surgeons prefer early cholecystectomy. However, more than one-third of patients suspected of having acute cholecystitis after initial clinical evaluation are ultimately proved to have a different diagnosis. In one study of 52 patients with acute right upper quadrant pain suspected of having acute cholecystitis, the diagnosis was confirmed in only 34.6%, whereas 32.7% had chronic cholecystitis and 32.7% had normal gallbladders (1).
Ultrasound (US) is the primary imaging modality used to evaluate acute right upper quadrant pain. In our experience, it is an accurate, safe, relatively inexpensive, and readily accessible imaging modality for investigating these patients. It is highly sensitive and specific for the detection of gallstones and biliary dilatation. As early as 1982, the accuracy of US (88%) was shown to be similar to that of scintigraphy with hepato-iminodiacetic acid (HIDA) (85%) in 91 patients suspected of having acute cholecystitis (2). In many practices, US has since replaced scintigraphy for these patients. Not only will US more easily demonstrate complications of acute cholecystitis, such as gangrenous and emphysematous change, but also it will frequently demonstrate an alternate diagnosis as the cause of the patient’s symptoms if the gallbladder is normal. Finally, scintigraphy is time-consuming, often requiring up to 4 hours for differentiation of acute from chronic cholecystitis (3). Many authors therefore suggest that nuclear imaging for the diagnosis of acute cholecystitis be reserved for patients with the rare equivocal sonogram (1,4,5).
US is also superior to computed tomography (CT) as the initial imaging investigation for assessment of biliary disease causing acute right upper quadrant pain. This view is supported by a study by Harvey et al (6) where CT was the initial imaging study in 57 patients, and CT findings resulted in underdiagnosis or misdiagnosis in eight of 11 patients with acute biliary disease. Follow-up US, performed within 48 hours of the CT, suggested the correct diagnosis and provided additional clinical information in seven of these eight patients. In addition, US findings resulted in altered clinical management in six of the 11 patients with acute biliary disease. US was the initial imaging study in 66 patients, and US findings were suggestive of biliary disease or the correct diagnosis in seven of seven patients with acute biliary disease. Follow-up CT within 48 hours of the US examination did not result in altered clinical treatment in any of these seven patients.
Although US is an excellent modality for the initial evaluation of the patient with acute right upper quadrant pain and will often suffice to direct treatment decisions, there are situations where additional imaging may be required. In general terms, CT is an excellent second choice. It will frequently provide a better overview of the scope and extent of disease where visibility with US is limited (eg, open wounds, surgical dressings, and obesity) and will complement the US findings in more complex cases. The combination of US and magnetic resonance (MR) imaging or MR cholangiopancreatography provides excellent potential for diagnosis of acute biliary ductal disease. On the other hand, endoscopic retrograde cholangiopancreatography (ERCP) with papillotomy is the treatment of choice for patients shown to have choledocholithiasis at US and may also be a helpful adjunct to intravenous fluids and antibiotics in treating patients with ascending cholangitis shown to have biliary dilatation at US.
The spectrum of diseases that may manifest as acute right upper quadrant pain includes acute cholecystitis and its complications, gangrene and perforation; gallbladder torsion; mimics of acute cholecystitis; choledocholithiasis; biliary colic caused by hemobilia; hepatic artery aneurysm; ascending cholangitis; liver abscess; recurrent pyogenic cholangiohepatitis; and complications of liver masses, such as rupture and hemorrhage. The operator must be familiar with the characteristic and unusual appearances of these conditions and must be aware of potential pitfalls that can mimic them.
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Acute Cholecystitis
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Acute cholecystitis occurs in approximately one-third of patients who have gallstones (7). Ninety percent to 95% are due to calculous obstruction of the gallbladder neck or cystic duct leading to increased intraluminal pressure and distention. Inflammation may result from chemical injury of the mucosa by bile salts and/or superimposed infection. Gallbladder ischemia and transmural necrosis may occur if the obstruction persists. The differential diagnosis for acute cholecystitis is extensive and includes choledocholithiasis, pancreatitis, peptic ulcer disease, acute hepatitis, liver abscess, liver neoplasm with complication, pneumonia, and heart disease.
The most sensitive US finding in acute cholecystitis is the presence of cholecystolithiasis in combination with maximal tenderness over the sonographically localized gallbladder (sonographic Murphy sign). In one study of 497 patients, Ralls et al (8) showed this combination of findings to have a positive predictive value of 92%. In our experience, the presence of a tensely distended gallbladder is also very helpful, and we are somewhat reluctant to entertain the diagnosis of acute cholecystitis in its absence. Lack of this finding will at least prompt us to look more carefully for another cause for the patient’s pain. Finally, every effort should be made to demonstrate the obstructing stone in the gallbladder neck or cystic duct (Figs 1, 2). Success will often depend on various maneuvers including the use of different acoustic windows (eg, subcostal and intercostal) to assess the cystic duct and altering the patient’s position (eg, supine, decubitus, sitting, and standing) to demonstrate lack of movement of an impacted stone in the gallbladder neck. Both gallbladder wall thickening (>3 mm) and pericholecystic fluid are secondary findings that are neither sensitive nor specific for acute cholecystitis. There are reports in the literature of improving sensitivity and specificity when making the diagnosis of acute cholecystitis with color and power Doppler US (9). However, we rarely include Doppler US as part of the routine examination when considering this diagnosis, relying instead on the gray-scale appearances and a positive or negative sonographic Murphy sign to confirm or refute the clinical impression.
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Figure 1a. Acute cholecystitis in a 38-year-old woman. (a) Sagittal sonogram shows stones (arrow) in a tense, distended gallbladder. The patient experienced maximal tenderness when the transducer was pressed over the fundus of the gallbladder (arrowhead) (sonographic Murphy sign). (b) Transverse oblique intercostal sonogram of the neck of the gallbladder (arrowheads) shows an obstructing stone (arrow).
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Figure 1b. Acute cholecystitis in a 38-year-old woman. (a) Sagittal sonogram shows stones (arrow) in a tense, distended gallbladder. The patient experienced maximal tenderness when the transducer was pressed over the fundus of the gallbladder (arrowhead) (sonographic Murphy sign). (b) Transverse oblique intercostal sonogram of the neck of the gallbladder (arrowheads) shows an obstructing stone (arrow).
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Figure 2. Acute cholecystitis in a 42-year-old man. Sagittal sonogram shows stones in the fundus (arrowheads) and an obstructing stone in the neck (arrow) of a tense, distended gallbladder, which was also tender.
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A potential problem when evaluating the gallbladder with US is the presence of tumefactive sludge within the gallbladder lumen. This appearance may raise the possibility of gallbladder cancer. Doppler US may be helpful by demonstrating blood flow in a polypoid neoplasm, whereas no flow will be detected in tumefactive sludge. In the asymptomatic patient, the problem may also be resolved by repeating the study after a fatty meal or after a period of a few days to weeks. In the acute setting, however, this distinction becomes more urgent as many of these patients may be candidates for early cholecystectomy. Laparoscopic cholecystectomy should not be performed if gallbladder cancer is a consideration because of the high recurrence rates (Fig 3). Open cholecystectomy should be performed in this situation with consideration given to resection of segments V and IVB of the liver. Additional imaging with triphasic CT can therefore be helpful (Fig 4). The absence of an enhancing mass at CT suggests that gallbladder cancer is not present.
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Figure 3. Recurrent gallbladder cancer in a 57-year-old man. Axial CT scan shows recurrent tumor at the site of the right upper quadrant port (arrow). There was also evidence of tumor recurrence at the site of the umbilical port (not shown).
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Figure 4a. Acute cholecystitis in a 64-year-old woman with pain and fever. (a) Sagittal sonogram shows stones (arrowheads) embedded in heterogeneous material. Abdominal CT was performed to rule out gallbladder cancer. (b) Axial CT scan shows a distended gallbladder with stones, wall thickening, and edema (arrowheads). A breach in the enhancing mucosa (arrow) suggests early, focal gangrene. No enhancing mass was seen at comparison with the unenhanced images (not shown). Acute cholecystitis was confirmed at surgery.
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Figure 4b. Acute cholecystitis in a 64-year-old woman with pain and fever. (a) Sagittal sonogram shows stones (arrowheads) embedded in heterogeneous material. Abdominal CT was performed to rule out gallbladder cancer. (b) Axial CT scan shows a distended gallbladder with stones, wall thickening, and edema (arrowheads). A breach in the enhancing mucosa (arrow) suggests early, focal gangrene. No enhancing mass was seen at comparison with the unenhanced images (not shown). Acute cholecystitis was confirmed at surgery.
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Acalculous cholecystitis accounts for 5%–10% of all cases of acute cholecystitis and occurs most commonly in patients in the intensive care unit. Predisposing factors include trauma, mechanical ventilation, hyperalimentation, the postoperative state, diabetes mellitus, vascular insufficiency, prolonged fasting, burns, and the postpartum state. These conditions share the propensity to produce gallbladder ischemia. Acalculous cholecystitis carries high morbidity and mortality rates partly because of difficulty and delay in making the diagnosis. These patients are challenging to assess clinically, and the sonographic features are nonspecific. Scintigraphy has the propensity to give false-positive results in this patient population. As a result, image-guided cholecystostomy tube placement is therefore often performed to decompress the gallbladder if there is a high index of suspicion and the gallbladder is distended at US.
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Complications of Acute Cholecystitis
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Gangrenous Cholecystitis
Increased intraluminal pressure may produce gallbladder wall ischemia and ultimately necrosis, resulting in gangrenous cholecystitis. It complicates acute cholecystitis in 2%–38% of cases (10). Perforation is more common than in uncomplicated cholecystitis, leading to increased morbidity and mortality. As the gallbladder necroses, clinical symptoms and signs may become more generalized. The abdominal pain may be diffuse in up to 50% of patients (11) possibly because of more generalized peritonitis with inflammation of the parietal peritoneum.
In the symptomatic patient, the presence of asymmetric gallbladder wall thickening or intraluminal membranes should be viewed with suspicion for gangrenous change (Fig 5). The sonographic Murphy sign may be negative in up to 66% of cases (11), probably because of denervation of the gallbladder wall by gangrenous changes. At CT, findings with the highest specificity for gangrenous cholecystitis are gas in the wall or lumen (100%), intraluminal membranes (99.5%), irregular or absent wall (97.6%), and abscess (96.6%) (12). Because of the increased risk of perforation (up to 10%) (10), early cholecystectomy should be performed if gangrenous cholecystitis is likely.
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Figure 5. Gangrenous cholecystitis in a 38-year-old man with polyarteritis nodosa and vague abdominal pain. Sagittal sonogram shows sloughed membranes (arrows) and sludge or pus layered in the gallbladder. The diagnosis was confirmed at urgent cholecystectomy.
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Emphysematous Cholecystitis
Emphysematous cholecystitis is a rare condition associated with the presence of gas-forming bacteria in the gallbladder wall and lumen. Cholecystolithiasis is often absent. It is more common in men than women (7:3) (13), and 40% of the patients are diabetic. There is a fivefold increased risk of gangrene and perforation. Emphysematous cholecystitis is a surgical emergency and is treated definitively with cholecystectomy. Percutaneous cholecystostomy may be used as a temporizing procedure in critically ill patients.
The appearance at US may be characteristic. Intraluminal gas appears as a nondependent hyperechoic focus with ring-down or comet-tail artifact. The gas may move with changes in the patient’s position. Intramural gas appears as an arclike echogenic interface with posterior reverberation artifact (14) (Fig 6). Care must be taken to distinguish this appearance from a gallbladder packed with stones (Fig 7) or calcificationin the gallbladder wall (porcelain gallbladder). In difficult cases, CT is most sensitive for confirming gas in the gallbladder wall or lumen (15). It also allows distinction between gas and wall calcification, as is seen with porcelain gallbladder. CT should also be performed in patients with acute right upper quadrant pain in whom the gallbladder is not definitely identified at sonography because a gas-filled gallbladder may be mistaken for gas-filled bowel with dire consequences.
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Figure 6a. Emphysematous cholecystitis in a 58-year-old diabetic man with end-stage renal disease. (a) Sagittal sonogram shows a curvilinear echogenic interface in the gallbladder fossa (arrowheads) with reverberation artifact (arrows). These findings are suggestive of gas in the wall of the gallbladder. (b) Axial CT scan shows gas in the gallbladder lumen (GB) and wall (arrow).
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Figure 6b. Emphysematous cholecystitis in a 58-year-old diabetic man with end-stage renal disease. (a) Sagittal sonogram shows a curvilinear echogenic interface in the gallbladder fossa (arrowheads) with reverberation artifact (arrows). These findings are suggestive of gas in the wall of the gallbladder. (b) Axial CT scan shows gas in the gallbladder lumen (GB) and wall (arrow).
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Figure 7. Cholelithiasis in a 34-year-old woman. Sagittal sonogram of the gallbladder shows the wall (W)-echo (E)-shadow (S) complex, which indicates that the gallbladder is filled with stones.
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Gallbladder Perforation
Gallbladder perforation is a serious complication of acute cholecystitis and may occur in up to 10% of cases. There is an associated mortality rate of 19%–24%. Early detection reduces morbidity and mortality. There are three categories of gallbladder perforation as classified by Niemeier (16): acute, subacute, and chronic. Acute perforation results in generalized peritonitis and has the worst prognosis. Subacute perforation is generally contained, resulting in pericholecystic abscess. Chronic perforation may result in an internal biliary fistula, often to the duodenum or common bile duct. Most perforations are subacute, accounting for 60% of all cases. Chronic perforation accounts for 30%, and acute perforation accounts for 10%.
Both US and CT are comparable in their ability to show the defect in the gallbladder wall (Fig 8). In one study of 23 patients, US helped diagnose the defect in the gallbladder wall in 16 (70%). Eighteen patients in this series underwent both US and CT, with US demonstrating the defect in 11 of these cases (61%) and CT demonstrating the defect in 14 (78%). This difference did not reach statistical significance (17).
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Figure 8a. Subacute gallbladder perforation in a 72-year-old man. (a) Sagittal sonogram shows a large stone (arrowhead) in the neck of a decompressed gallbladder (GB). There is evidence of a heterogeneous mass in the liver (?). (b) Sagittal sonogram of the liver shows the mass (A), which is complex, located in segment V, and suggestive of an abscess. (c) Sagittal sonogram obtained in a different plane than in a shows a breach in the gallbladder wall (arrow), which leads into the abscess. (d) Axial CT scan of the abdomen shows the large defect (arrowhead) in the gallbladder (GB) wall. The pericholecystic extent of the abscess is also seen.
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Figure 8b. Subacute gallbladder perforation in a 72-year-old man. (a) Sagittal sonogram shows a large stone (arrowhead) in the neck of a decompressed gallbladder (GB). There is evidence of a heterogeneous mass in the liver (?). (b) Sagittal sonogram of the liver shows the mass (A), which is complex, located in segment V, and suggestive of an abscess. (c) Sagittal sonogram obtained in a different plane than in a shows a breach in the gallbladder wall (arrow), which leads into the abscess. (d) Axial CT scan of the abdomen shows the large defect (arrowhead) in the gallbladder (GB) wall. The pericholecystic extent of the abscess is also seen.
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Figure 8c. Subacute gallbladder perforation in a 72-year-old man. (a) Sagittal sonogram shows a large stone (arrowhead) in the neck of a decompressed gallbladder (GB). There is evidence of a heterogeneous mass in the liver (?). (b) Sagittal sonogram of the liver shows the mass (A), which is complex, located in segment V, and suggestive of an abscess. (c) Sagittal sonogram obtained in a different plane than in a shows a breach in the gallbladder wall (arrow), which leads into the abscess. (d) Axial CT scan of the abdomen shows the large defect (arrowhead) in the gallbladder (GB) wall. The pericholecystic extent of the abscess is also seen.
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Figure 8d. Subacute gallbladder perforation in a 72-year-old man. (a) Sagittal sonogram shows a large stone (arrowhead) in the neck of a decompressed gallbladder (GB). There is evidence of a heterogeneous mass in the liver (?). (b) Sagittal sonogram of the liver shows the mass (A), which is complex, located in segment V, and suggestive of an abscess. (c) Sagittal sonogram obtained in a different plane than in a shows a breach in the gallbladder wall (arrow), which leads into the abscess. (d) Axial CT scan of the abdomen shows the large defect (arrowhead) in the gallbladder (GB) wall. The pericholecystic extent of the abscess is also seen.
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Cholecystoenteric Fistula
The gallbladder has a close anatomic relationship to the duodenum and the proximal transverse colon. As a result, inflammation of the gallbladder may lead to chronic perforation and fistulous communication to either of these structures. A cholecystoduodenal fistula is by far the more common. Once a fistula is established, air may pass from the bowel into the gallbladder and stones may pass from the gallbladder into the bowel. As these stones pass through the bowel they may cause mechanical obstruction, most often in the ileum (gallstone ileus) (18) (Fig 9) but also at other levels including the duodenum (Bouveret syndrome) (18) (Fig 10).
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Figure 9a. Gallstone ileus in a 46-year-old woman. (a) Axial CT scan shows a fistulous communication (arrowhead) between the gallbladder and the duodenum, both of which are filled with air. Note the dilated loops of the proximal small intestine (BL). (b) Axial CT scan obtained inferiorly to a shows gallstones in a distal ileal loop (arrow). The stones are the cause of the obstruction.
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Figure 9b. Gallstone ileus in a 46-year-old woman. (a) Axial CT scan shows a fistulous communication (arrowhead) between the gallbladder and the duodenum, both of which are filled with air. Note the dilated loops of the proximal small intestine (BL). (b) Axial CT scan obtained inferiorly to a shows gallstones in a distal ileal loop (arrow). The stones are the cause of the obstruction.
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Figure 10a. Duodenal obstruction by a gallstone (Bouveret syndrome) in an 85-year-old woman. (a) Transverse oblique sonogram of the gallbladder fossa shows gas (arrowhead) with reverberation artifact (arrows). (b) Sagittal sonogram obtained adjacent to the gallbladder fossa shows a large, fluid-filled structure (D). This structure demonstrated active peristalsis, which suggested that it was the duodenum. A gallstone (arrow) is seen within the structure. (c) Axial CT scan shows a fistulous communication (arrow) between the air-filled gallbladder and the distended, fluid-filled duodenum. (d) Axial CT scan obtained inferiorly to c shows a gallstone (arrow) in the third part of the duodenum. This large stone is the one seen on the sonogram (b). (e) Axial CT scan obtained inferiorly to d shows an additional large, laminated stone (arrow) that obstructs the jejunum. This stone was not seen at US.
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Figure 10b. Duodenal obstruction by a gallstone (Bouveret syndrome) in an 85-year-old woman. (a) Transverse oblique sonogram of the gallbladder fossa shows gas (arrowhead) with reverberation artifact (arrows). (b) Sagittal sonogram obtained adjacent to the gallbladder fossa shows a large, fluid-filled structure (D). This structure demonstrated active peristalsis, which suggested that it was the duodenum. A gallstone (arrow) is seen within the structure. (c) Axial CT scan shows a fistulous communication (arrow) between the air-filled gallbladder and the distended, fluid-filled duodenum. (d) Axial CT scan obtained inferiorly to c shows a gallstone (arrow) in the third part of the duodenum. This large stone is the one seen on the sonogram (b). (e) Axial CT scan obtained inferiorly to d shows an additional large, laminated stone (arrow) that obstructs the jejunum. This stone was not seen at US.
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Figure 10c. Duodenal obstruction by a gallstone (Bouveret syndrome) in an 85-year-old woman. (a) Transverse oblique sonogram of the gallbladder fossa shows gas (arrowhead) with reverberation artifact (arrows). (b) Sagittal sonogram obtained adjacent to the gallbladder fossa shows a large, fluid-filled structure (D). This structure demonstrated active peristalsis, which suggested that it was the duodenum. A gallstone (arrow) is seen within the structure. (c) Axial CT scan shows a fistulous communication (arrow) between the air-filled gallbladder and the distended, fluid-filled duodenum. (d) Axial CT scan obtained inferiorly to c shows a gallstone (arrow) in the third part of the duodenum. This large stone is the one seen on the sonogram (b). (e) Axial CT scan obtained inferiorly to d shows an additional large, laminated stone (arrow) that obstructs the jejunum. This stone was not seen at US.
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Figure 10d. Duodenal obstruction by a gallstone (Bouveret syndrome) in an 85-year-old woman. (a) Transverse oblique sonogram of the gallbladder fossa shows gas (arrowhead) with reverberation artifact (arrows). (b) Sagittal sonogram obtained adjacent to the gallbladder fossa shows a large, fluid-filled structure (D). This structure demonstrated active peristalsis, which suggested that it was the duodenum. A gallstone (arrow) is seen within the structure. (c) Axial CT scan shows a fistulous communication (arrow) between the air-filled gallbladder and the distended, fluid-filled duodenum. (d) Axial CT scan obtained inferiorly to c shows a gallstone (arrow) in the third part of the duodenum. This large stone is the one seen on the sonogram (b). (e) Axial CT scan obtained inferiorly to d shows an additional large, laminated stone (arrow) that obstructs the jejunum. This stone was not seen at US.
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Figure 10e. Duodenal obstruction by a gallstone (Bouveret syndrome) in an 85-year-old woman. (a) Transverse oblique sonogram of the gallbladder fossa shows gas (arrowhead) with reverberation artifact (arrows). (b) Sagittal sonogram obtained adjacent to the gallbladder fossa shows a large, fluid-filled structure (D). This structure demonstrated active peristalsis, which suggested that it was the duodenum. A gallstone (arrow) is seen within the structure. (c) Axial CT scan shows a fistulous communication (arrow) between the air-filled gallbladder and the distended, fluid-filled duodenum. (d) Axial CT scan obtained inferiorly to c shows a gallstone (arrow) in the third part of the duodenum. This large stone is the one seen on the sonogram (b). (e) Axial CT scan obtained inferiorly to d shows an additional large, laminated stone (arrow) that obstructs the jejunum. This stone was not seen at US.
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There may be difficulty identifying the gallbladder with US, as it is often air-filled and contracted from chronic inflammation. US may show evidence of bowel dilatation and will often demonstrate an obstructing stone in the bowel. However, CT will more accurately demonstrate the fistula and the level of bowel obstruction.
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Gallbladder Torsion
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Gallbladder torsion is a rare cause of acute abdominal pain with only limited case reports in the literature. It is usually seen in elderly patients, so it may become more common as the population ages. The majority of patients are female (84%). It is most commonly acalculous (>67%). Mobility of the gallbladder because of a long or absent mesentery ("floating gallbladder") predisposes to torsion, which may be either complete (>180°) or incomplete (<180°). Complete torsion is likely to result in vascular compromise and gangrene of the gallbladder, whereas incomplete torsion may only obstruct the cystic duct and blood supply to the gallbladder wall may be maintained. A high index of suspicion is required to make this diagnosis preoperatively. US may show a distended, tender gallbladder with an abnormal orientation remote from the gallbladder fossa (Fig 11). CT and MR imaging may help confirm the diagnosis (19) and may show tapering and twisting of the cystic duct.
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Figure 11a. Incomplete gallbladder torsion in a 94-year-old woman. (a) Sagittal sonogram of the midabdomen shows a cystic mass (C) with edematous walls anterior to the abdominal aorta (A). (b) Coronal oblique maximum intensity projection CT scan shows that the mass has a beaked neck (arrow), which extends into the gallbladder fossa.
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Figure 11b. Incomplete gallbladder torsion in a 94-year-old woman. (a) Sagittal sonogram of the midabdomen shows a cystic mass (C) with edematous walls anterior to the abdominal aorta (A). (b) Coronal oblique maximum intensity projection CT scan shows that the mass has a beaked neck (arrow), which extends into the gallbladder fossa.
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Mimics of Acute Cholecystitis
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Sympathetic thickening of the gallbladder wall occurring secondary to an acute inflammatory process in the right upper quadrant, including acute pancreatitis, perforated duodenal ulcer, hepatitis, right-sided diverticulitis, and even acute right-sided pyelonephritis, may cause confusion when assessing the gallbladder for acute cholecystitis (20). Edema of the gallbladder wall from a systemic condition (eg, congestive heart failure, hypoalbuminemia) may also be problematic.
Because many of these diagnoses mimic the presentation of acute cholecystitis, the diagnostic imager requires a high level of awareness in order to avoid mistakes (Figs 12–14). Gallstones may or may not be present. The patient may be tender in the right upper quadrant; however, an important point is that this tenderness is often remote from the sonographically localized gallbladder (Fig 15). We also find lack of tense gallbladder distention a useful "flag" to prompt us to consider an alternate diagnosis (Fig 16). Careful assessment of the right upper quadrant may then yield additional findings (eg, free air) that facilitate making the correct diagnosis.
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Figure 12. Acute viral hepatitis in a 38-year-old woman. Sagittal sonogram of the gallbladder shows a tiny, slitlike lumen (*) with massive "onion peel" edema of the wall (arrowheads).
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Figure 13. Congestive heart failure in a 56-year-old man. Sagittal sonogram of the gallbladder shows edema of the wall (arrowheads), pericholecystic free fluid (FF), and distention of the inferior vena cava (IVC).
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Figure 15a. Perforated diverticulitis of the hepatic flexure in a febrile 67-year-old woman. (a) Sagittal sonogram shows a distended gallbladder (GB) with a small amount of pericholecystic fluid (arrow) but no stones. (b) Sagittal sonogram obtained at the site of maximal tenderness shows a thickened hepatic flexure (HF) with an inflamed diverticulum (*), from which extends a linear tract of extraluminal gas (arrow) surrounded by inflamed fat (arrowheads).
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Figure 15b. Perforated diverticulitis of the hepatic flexure in a febrile 67-year-old woman. (a) Sagittal sonogram shows a distended gallbladder (GB) with a small amount of pericholecystic fluid (arrow) but no stones. (b) Sagittal sonogram obtained at the site of maximal tenderness shows a thickened hepatic flexure (HF) with an inflamed diverticulum (*), from which extends a linear tract of extraluminal gas (arrow) surrounded by inflamed fat (arrowheads).
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Figure 16a. Perforated duodenal ulcer in a 76-year-old man. (a) Sagittal sonogram shows a stone in the gallbladder neck (arrow). The patient had epigastric tenderness. Note that the gallbladder is not tensely distended. (b) Sonogram of the right upper quadrant, obtained with the patient in the left posterior oblique position, shows enhancement of the parietal peritoneal line (arrowhead) with reverberation artifact (arrow), findings suggestive of free air. (c) Axial CT scan of the abdomen shows pericholecystic inflammation (arrow) and pneumoperitoneum (arrowhead). GB = gallbladder.
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Figure 16b. Perforated duodenal ulcer in a 76-year-old man. (a) Sagittal sonogram shows a stone in the gallbladder neck (arrow). The patient had epigastric tenderness. Note that the gallbladder is not tensely distended. (b) Sonogram of the right upper quadrant, obtained with the patient in the left posterior oblique position, shows enhancement of the parietal peritoneal line (arrowhead) with reverberation artifact (arrow), findings suggestive of free air. (c) Axial CT scan of the abdomen shows pericholecystic inflammation (arrow) and pneumoperitoneum (arrowhead). GB = gallbladder.
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Figure 16c. Perforated duodenal ulcer in a 76-year-old man. (a) Sagittal sonogram shows a stone in the gallbladder neck (arrow). The patient had epigastric tenderness. Note that the gallbladder is not tensely distended. (b) Sonogram of the right upper quadrant, obtained with the patient in the left posterior oblique position, shows enhancement of the parietal peritoneal line (arrowhead) with reverberation artifact (arrow), findings suggestive of free air. (c) Axial CT scan of the abdomen shows pericholecystic inflammation (arrow) and pneumoperitoneum (arrowhead). GB = gallbladder.
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It is especially important not to misinterpret gallbladder wall edema secondary to acute hepatitis as representing acute cholecystitis. Some general anesthetics, if given to such a patient for emergent cholecystectomy, may have hepatotoxic effects and can be fatal.
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Choledocholithiasis
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Stones in the common bile duct may manifest with acute right upper quadrant pain and/or jaundice. They may also be discovered as a causative factor in acute pancreatitis or be uncovered incidentally at the time of imaging for some other reason.
US has a sensitivity of 70%–75% for detection of common bile duct stones (Fig 17). In one study, Laing et al (21) found that eight (89%) of nine proximal and 16 (70%) of 23 distal commonbile duct stones were visualized with US. Detection of choledocholithiasis can be substantially improved by scanning the proximal and distal common bile duct separately. The intrapancreatic portion of the bile duct should be assessed first in a transverse plane with the patient in a semierect right posterior oblique position. The proximal duct is best imaged by obtaining parasagittal scans with the patient in a supine left posterior oblique position (22).
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Figure 17. Choledocholithiasis in a 78-year-old man. Sagittal sonogram shows a large stone (arrows) with a faint shadow (lines), which is a result of scanning with compound imaging (arrowhead). With compound imaging, the sound waves are steered off axis, providing up to nine transmit angles (lines of sight) in the course of a single scan. Thus, the sound waves strike the stone from many different angles and disperse the shadow. SCT = sono-CT.
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If common bile duct stones are visualized with US, then the patient should be referred directly to ERCP for definitive management (papillotomy). On the other hand, if choledocholithiasis is suspected but cannot be confirmed with US, MR cholangiopancreatography is an excellent choice for further investigation, with a sensitivity of 95% and specificity of 100% (23) (Fig 18). If immediate access to MR cholangiopancreatography is limited, then CT is an alternative to diagnostic ERCP with 80% sensitivity and 100% specificity (24). However, it is mandatory in this scenario that an unenhanced, thinly collimated series through the liver and common bile duct be included in the study to improve detection of stones and to avoid misinterpretation of a common bile duct stone as an enhancing mass (Fig 19). It is also advisable in this situation to give water as an oral contrast agent, as positive oral contrast agents may obscure stones in the distal common bile duct.
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Figure 19a. Choledocholithiasis in a 69-year-old man. (a) Axial CT scan obtained after intravenous administration of contrast material shows an area of high attenuation in the distal common bile duct (arrow), a finding that raises the possibility of an enhancing mass. The bile ducts were dilated to this level (not shown). (b) Axial CT scan obtained without contrast material at the same level as a shows that the area of high attenuation is a stone (arrow).
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Figure 19b. Choledocholithiasis in a 69-year-old man. (a) Axial CT scan obtained after intravenous administration of contrast material shows an area of high attenuation in the distal common bile duct (arrow), a finding that raises the possibility of an enhancing mass. The bile ducts were dilated to this level (not shown). (b) Axial CT scan obtained without contrast material at the same level as a shows that the area of high attenuation is a stone (arrow).
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Hemobilia
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The classical clinical triad for hemobilia consists of melena, jaundice, and abdominal pain but is seen in less than 50% of patients. Two-thirds of cases are iatrogenic, whereas trauma accounts for 5% (25). It may manifest many weeks after the initial injury. The diagnosis can be made with US (Fig 20), unenhanced CT (high-attenuation clot within the bile ducts), or MR imaging and confirmed with endoscopy (blood from the ampulla of Vater) or angiography. In one review, 43% of cases were managed conservatively and 36% were managed with transarterial embolization (25). The remainder were managed surgically either because of failed transarterial embolization or at the time of laparotomy for other reasons.
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Figure 20. Hemobilia in a 47-year-old woman after transjugular liver biopsy. Sagittal sonogram of the bile duct shows a linear, heterogeneous clot (arrow) within the lumen. L = liver.
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Hepatic Artery Aneurysm
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Hepatic artery aneurysms are rare vascular lesions. They may be found incidentally at the time of abdominal imaging or may manifest more acutely as jaundice and/or abdominal pain (26).
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Abstract
LEARNING OBJECTIVES FOR TEST...
