Ultrasound of Acalculous cholecystitis

Inflammation of the gallbladder without stones is relatively uncommon. A thickened, tender gallbladder wall in the absence of any other obvious cause of thickening may be due to acalculous cholecystitis. This condition tends to be associated with patients who are already hospitalized and have been fasting, including post-trauma patients, those recovering from surgical procedures and diabetic patients. It is brought about by bile stasis leading to a distended gallbladder and subsequently decreased blood flow to the gallbladder. This, especially in the weakened postoperative state, can lead to infection. Because no stones are present, the diagnosis is more difficult and may be delayed. Patients with acalculous cholecystitis are therefore more likely to have severe pain and fever by the time the diagnosis is made, increasing the incidence of complications such as perforation.

The wall may appear normal on ultrasound in the early stages, but progressively thickens (Fig.a). Biliary sludge is usually present and a pericholecystic abscess may develop in the later stages. A positive Murphy’s sign may help to focus on the diagnosis, but in unconscious patients the diagnosis is a particularly difficult one.
Because patients may already be critically ill with their presenting disease, or following surgery, there is a role for ultrasound in guiding percutaneous cholecystostomy at the bed-side to relieve the symptoms. Chronic acalculous cholecystitis implies a recurrent presentation with typical symptoms of biliary
colic, but no evidence of stones on ultrasound.
Patients may also demonstrate a low ejection fraction during a cholecystokinin-stimulated hepatic iminodiacetic acid (HIDA) scan. The symptoms are relieved by elective laparoscopic cholecystectomy in most patients, with similar results to those for gallstone disease (although some are found to have biliary pathology at surgery, which might explain the symptoms, such as polyps, cholesterolosis or biliary crystals/tiny stones in addition to chronic inflamation).

(fig.a )Acalculous cholecystitis. The gallbladder wall is markedly thickened and tender on scanning.
and Gravity-dependent sludge with a thick, oedematous wall. No stones were present.