Diagnostic Ultrasound - Abdomen and Pelvis

Acute Acalculous Cholecystitis
Diagnoses: Biliary System
• Anechoic or low-level echoes in lumen from bile or mucus
• Nonthickened wall
PATHOLOGY
General Features
• Etiology
○ Acalculous cholecystitis constitutes ~ 10% of acute
cholecystitis
○ Pathogenesis is multifactorial
– Combination of increased bile viscosity and wall
ischemia with reperfusion injury
□ Bile stasis secondary to fasting, obstruction,
surgery, or procedures irritates gallbladder
epithelium
□ Ischemia from systemic hypotension, shock,
trauma, recent surgery, sepsis, burns, vasculitis
○ Occurs in critically ill patients with multiple risk factors
– Post major surgery, severe trauma, sepsis, diabetes,
atherosclerotic disease, TPN
– Infection: Bacterial, viral, fungal, parasitic
(opportunistic GB infection in AIDS)
– Obstruction of cystic duct by extrinsic compression by
metastases, lymphadenopathy
Gross Pathologic & Surgical Features
• Bile cultures positive in up to 78%, gram-negative bacilli
most common
Microscopic Features
• Ischemia and reperfusion injury
• Increased and deeper bile infiltration into gallbladder wall
• Necrosis, leucocyte infiltration, lymphatic dilation
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Acute RUQ pain, fever, sepsis in critically ill patient
• Other signs/symptoms
○ Nonspecific leucocytosis, elevation of liver function tests
• Clinical profile
○ Raised WBC, abnormal liver function tests
• Diagnosis may be challenging in critically ill patient with
multiple comorbidities
Demographics
• Age
○ More common in middle-aged and elderly
• Gender
○ M:F = 3:1
• Epidemiology
○ 0.2-0.4 % of critically ill patients
Natural History & Prognosis
• Worse prognosis than acute calculous cholecystitis
• 40% develop complications such as gangrene, perforation,
and empyema
• Mortality rate up to 30%
Treatment
• Prompt cholecystectomy is standard if patient is surgical
candidate
• Percutaneous cholecystostomy
○ Useful in poor operative risk patients, in combination
with antibiotics
○ May be diagnostic (bile obtained for culture) and
therapeutic
○ Not indicated for gangrenous gallbladders
○ Requires cholangiography to exclude bile duct stones
and obstruction prior to removal of cholecystostomy
tube
• Percutaneous drainage of pericholecystic fluid collections
DIAGNOSTIC CHECKLIST
Consider
• Ultrasound is first-line modality given portability, rapidity,
and repeatability
• Consider diagnosis when US features of acute cholecystitis
without impacted gallstone
○ High index of suspicion in critically ill patients
○ Repeat ultrasound for indeterminate cases
– Or HIDA scan
Image Interpretation Pearls
• Confirm with HIDA scan
○ Limitations of HIDA: Lengthy, requires transportation of
patient
• Assess for complications such as gangrene or perforation
○ CT more sensitive for complications or alternative
diagnoses
SELECTED REFERENCES
1. Atar E et al: Percutaneous cholecystostomy in critically ill patients with acute
cholecystitis: complications and late outcome. Clin Radiol. 69(6):e247-52,
2014
2. Charalel RA et al: Complicated cholecystitis: the complementary roles of
sonography and computed tomography. Ultrasound Q. 27(3):161-70, 2011
3. Gore RM et al: Gallbladder imaging. Gastroenterol Clin North Am. 39(2):265-
87, ix, 2010
4. Huffman JL et al: Acute acalculous cholecystitis: a review. Clin Gastroenterol
Hepatol. 8(1):15-22, 2010
5. Ziessman HA: Nuclear medicine hepatobiliary imaging. Clin Gastroenterol
Hepatol. 8(2):111-6, 2010
6. Smith EA et al: Cross-sectional imaging of acute and chronic gallbladder
inflammatory disease. AJR Am J Roentgenol. 192(1):188-96, 2009
7. van Breda Vriesman AC et al: Diffuse gallbladder wall thickening: differential
diagnosis. AJR Am J Roentgenol. 188(2):495-501, 2007
8. Hanbidge AE et al: From the RSNA refresher courses: imaging evaluation for
acute pain in the right upper quadrant. Radiographics. 24(4):1117-35, 2004
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