ACUTE
ACALCULOUS CHOLECYSTITIS RADIOLOGY PEARLS
ACUTE ACALCULOUS CHOLECYSTITIS:
ESSENTIAL FACTS ABOUT ACUTE ACALCULOUS CHOLECYSTITIS:
Acute acalculous cholecystitis is
inflammation of the gallbladder without gallstones and represents only upto 5%
of cases of cholecystitis. Untreated Acute acalculous cholecystitis progresses
rapidly and has a very high risk of mortality.
Predisposing factors:
Include malignancy, diabetes burn, injury, recent
surgery or trauma, cardiac disease,total parenteral nutrition and
positive pressure ventilation. The clinical presentation may differ from
that of calculous cholicystitis (cholecystitis due to gallstones) in that the
severity of disease may be out of proportion to the severity of right
hypochondriac pain. Some patients are pain-free despite pyrexia and increased
white cell count.
Severe presentations of Acute Acalculous cholecystitis:
Gangrenous cholecystitis may occur with calculous or
acalculous cholecystitis and is a lethal complication, caused by secondary
ischemic necrosis; look for sloughed or broken membranes, intramural or
intraluminal gas, an irregular or absent gallbladder wall, and abscess
formation.
Emphysematous cholecystitis
This may occur with calculous or acalculous
cholecystitis and is an ominous condition usually caused by E.coli and
Klebsiella infection. About 50% of cases occur in the setting of diabetes, and
the characteristic finding is gas inside the gallbladder wall. On ultrasonography
gas is seen in the non dependant wall of gallbladder which differentiates it
from gallstones which are gravity dependant. If left untreated, this condition
may lead to perforation of gallbladder with resultant peritonitis.
Treatment options:
Include percutaneous cholecystostomy(usually the first
line and definitive treatment for AC in which gallbladder in drained through
skin),surgical cholecystectomy, and endoscopic nasobiliary drain for suboptimal
surgical or radiologic candidates.
DIFFERENTIAL DIAGNOSIS:
Acute cholecystitis:
This is indicated by pericholecystic fat stranding and
the clinical presentation. As no cholilithiasis is visible, the findings
suggest acalculous cholecystitis (AC). Sloughed mucosal membranes within the
gallbladder indicate gangrenous cholecystitis.
Adjacent inflammation
Infection from diverticulitis, pancreatitis,
hepatitis, or peptic ulcer disease: This can secondarily involve the
gallbladder or mimic acute cholecystitis.
OTHER IMAGING FINDINGS:
HIDA scan may
be first-line or in cases equivocal for Acute cholicystitis on CT or
ultrasound; a positive study shows nonvisualization of technetium-99m
iminodiacetic acid within the gallbladder after 4 hours or after intravenous
morphine.
Ultrasound is the
best modality for the evaluation of cholecystitis, although Acute cholecystitis
is often diagnosed by CT during the work-up of chronically ill patients for
pyrexia of unknown origin. Look for absence of stones, sludge, luminal
distension, PCC fluid, and wall thickening that shows hyperemia by power
Doppler.
PEARLS:
Systemic diseases such as hypoproteinemia or organ failure (liver, renal,
heart) can mimic imaging findings of acute Acute cholicystitis.
Calculous cholecystitis
May present on ultrasound with the
WES sign indicating large stones against the gallbladder wall.
Xanthogranulomatous cholecystitis
Typically occurs in the setting of chronic calculous
cholecystitis and can be confused with gallbladder CA; this is a destructive,
inflammatory process often associated with gallbladder wall thickening with hypodense
intramural nodules. A low threshold for imaging in high-risk patients and for
cholecystostomy in equivocal cases is required because Acute acalculous
cholicystitis is life-threatening and rapidly progressing despite the mild
outward clinical signs.
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