Acalculous Cholecystitis

Published on 19/07/2015 by admin

Filed under Radiology

Last modified 19/07/2015

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 Findings identical to calculous cholecystitis (except gallstones)

image Thickening of gallbladder wall > 3 mm
image Positive sonographic Murphy sign

– May be absent or impossible to elicit in critically ill patients at highest risk
image Gallbladder distention (> 5 cm in transverse plane)
image Gallbladder wall hyperemia on color Doppler
• CT and MR

image Gallbladder wall thickening (> 3 mm) with mural/mucosal hyperenhancement

– May be associated with intramural lucency on CT caused by wall edema (subserosal halo sign)
image Dilated gallbladder (> 5 cm) with pericholecystic fluid and fat stranding
image Hyperenhancement of liver adjacent to gallbladder
• Hepatobiliary scintigraphy

image Nonvisualization of gallbladder 4 hours after injection of radiotracer (or 30 minutes after morphine)

TOP DIFFERENTIAL DIAGNOSES

• Acute calculous cholecystitis
• Gallbladder wall edema
• Hyperplastic cholecystoses
• Gallbladder carcinoma
• AIDS cholangiopathy

PATHOLOGY

• Not associated with obstruction of cystic duct by stones
• Most often result of bile stasis and gallbladder ischemia
• Typically occurs in critically ill patients (trauma, surgery, sepsis, mechanical ventilation, immunosuppression, etc.)

CLINICAL ISSUES

• Higher risk of morbidity/mortality compared to calculous cholecystitis with ↑ risk of complications

image More likely than calculous cholecystitis to present atypically
image Insidious presentation in critically ill patients and diagnosis is often delayed
• Preferred treatment: Cholecystectomy and broad spectrum intravenous antibiotics
• Cholecystostomy used as bridge to definitive cholecystectomy in critically ill, unstable patients
image
(Left) Coronal CECT in a critically ill ICU patient demonstrates severe gallbladder (GB) wall thickening and edema with pericholecystic fat stranding and fluid. Note the lack of clear enhancement of the GB wall near the fundus image, concerning for gangrenous cholecystitis.

image
(Right) Coronal CECT acquired a day later shows placement of a cholecystostomy tube image, a common temporizing measure in critically ill patients too unstable for cholecystectomy.
image
(Left) CECT of a diabetic septic female 4 days post laparotomy for a perforated duodenal ulcer shows a distended GB, wall thickening image, and pericholecystic fat infiltration image. No gallstones were identified at ultrasound.

image
(Right) Hepatobiliary scan of the same patient shows progressive small bowel filling image but no GB activity 30 minutes post tracer administration. No GB activity was shown after morphine administration (an observation that increases exam specificity).

TERMINOLOGY

Definitions

• Acute inflammation of gallbladder (GB) unrelated to gallstones

IMAGING

General Features

• Best diagnostic clue

image Combination of imaging features and clinical history

– Ultrasound: Distended GB with wall thickening, pericholecystic fluid, and positive sonographic Murphy sign but no gallstones
– Hepatobiliary scintigraphy: Nonvisualization of GB
– Typical clinical history: Critically ill patient

Ultrasonographic Findings

• Findings identical to acute calculous cholecystitis (except for absence of gallstones)

image Ultrasound often equivocal due to inability to elicit sonographic Murphy sign in intubated/unconscious patients
• Thickening of GB wall > 3 mm

image Higher thresholds increase specificity, but decrease sensitivity

– Using cutoff value of 3 mm leads to better sensitivity but lower specificity
– Using cutoff value of 4 mm (or 5 mm) leads to better specificity at the cost of having more false-negative cases
image Striated appearance of wall is common (no longer thought to be suggestive of gangrenous cholecystitis)
• Positive sonographic Murphy sign (pain with insonation over GB that is accentuated with deep breathing)

image May be absent or impossible to elicit in critically ill ICU patients at highest risk for acalculous acute cholecystitis
• GB distention (> 5 cm in transverse plane)
• Pericholecystic echogenic fat (due to inflammation)
• GB wall hyperemia on color Doppler images
• Complications

image Gangrenous cholecystitis: Asymmetric wall thickening, intraluminal linear membranes, and echogenic material due to sloughed mucosa and irregularity/ulcerations of GB wall

– May not be associated with wall hyperemia due to necrosis
image Emphysematous cholecystitis: Intramural and intraluminal gas with multiple bright echogenic reflectors and “dirty” posterior acoustic shadowing

– Champagne sign: Tiny, nonshadowing echogenic foci rising up in real-time from dependent portion of GB
image Perforated GB: Collapsed GB with discrete wall defect and adjacent pericholecystic fluid collection ± complex fluid in peritoneal cavity

– Most common site of perforation is fundus, which can be difficult to visualize in some patients
– Sonographic hole sign: Visualization of defect in GB wall is more easily diagnosed on CT
image Hemorrhagic cholecystitis: Echogenic clot within GB

CT Findings

• Imaging findings are identical to acute calculous cholecystitis (except for absence of gallstones)
• Uncomplicated acalculous cholecystitis

image GB wall thickening (> 3 mm) with mural and mucosal hyperenhancement

– May be associated with intramural lucency caused by wall edema (subserosal halo sign)
image Pericholecystic fluid and fat stranding
image Hyperenhancement of liver adjacent to GB (most apparent in arterial phase)
image Dilated GB (> 5 cm in diameter)
• Complicated acalculous cholecystitis

image Gangrenous cholecystitis: Hypoenhancement or nonenhancement of portions of GB wall

– May be associated with small sites of ulceration or outpouchings in GB wall
– Often associated with asymmetric wall thickening
– Intraluminal linear strands due to sloughed mucosa
image Emphysematous cholecystitis: Intramural or intraluminal gas with other findings of cholecystitis
image Hemorrhagic cholecystitis: High-density blood within GB ± blood in intrahepatic/extrahepatic ducts

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