The signs and symptoms on clinical examination are not consistent, although the presence of a palpable right upper quadrant mass with tenderness and fever in an elderly male should raise suspicion of acute acalculous cholecystitis. In a study of 22 ICU patients, only plasma alkaline phosphatase and urea levels were found to be significantly elevated when comparing the presence of necrosis or gangrene versus inflammation of the gallbladder. 'Liver function' studies are non-specific, particularly in the ICU patient who may have vascular insufficiency leading to an elevation in serum chemistries for other reasons. Although technetium hepato-iminodiacetic acid (HIDA) scans can be perfomed in the iCu and have 100 per cent sensitivity and 90 per cent specificity for acute acalculous cholecystitis, false-negative results have been reported. The use of the synthetic cholecystokinin octapeptide, sincalide, for cholescintigraphy has a high incidence of false negativity. In addition, some of the ICU patients may not be fed enterally, and thus radionuclide studies will give false-positive results, accounting for a high sensitivity but low specificity.
Ultrasound is a portable and less expensive study which can be done at the bedside in the ICU ( Fig 1). Significant findings include a gallbladder wall thickness of 4
mm or more, the presence of pericholecystic fluid, subserosal edema in the absence of ascites, intramural gas, and sloughing of the mucosal membrane. The presence of biliary sludge is a soft sign, and in the presence of right upper quadrant pain coupled with normal liver function and amylase levels is only 75 per cent accurate. A sonographic Murphy's sign of gallbladder distension and a thickened wall on ultrasound with right upper quadrant pain induced with the ultrasound probe may be a useful diagnostic tool. CT scanning may also be helpful, with positive findings for acute acalculous cholecystitis being similar to those seen on ultrasound. However, CT scanning requires transportation of patients out of the ICU with its inherent risks.
Fig. 1 Ultrasonogram showing a thickened gallbladder wall (between arrows) and sludge (single arrow) in a patient with operatively confirmed acute acalculous cholecystitis.
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