Acute acalculous cholecystitis

Acute acalculous cholecystitis refers to the development of cholecystitis in a gallbladder either without gallstones or with gallstones where they are not the contributory factor. It is thought to occur most often due to biliary stasis and/or gallbladder ischaemia.

Epidemiology

Acute acalculous cholecystitis represents 5-10% of cases of acute cholecystitis.

Risk factors

Risk factors for acute acalculous cholecystitis include ²:

• severe tissue injury (e.g. major trauma and burns)
• postoperative (especially following major surgery e.g. valvular replacement ¹³) 
• diabetes mellitus
• malignancy
• vasculitis
• congestive heart failure
• shock
• cardiac arrest
• advanced age ¹²
• concomitant opioid therapy
• positive-pressure ventilation (PPV)
• total parenteral nutrition (TPN)
• viral infections: Epstein-Barr virus, dengue virus, hepatitis A virus, hepatitis B virus, hepatitis C virus, cytomegalovirus (CMV), disseminated varicella-zoster virus (VZV), Zika virus and HIV ¹⁵

Pathology

Acute acalculous cholecystitis usually occurs in critically ill or injured patients (e.g. trauma, burns, sepsis). The risk factors listed above may affect the perfusion of the gallbladder and favour bile stasis leading to injury and inflammation. Subsequent ischaemia-reperfusion injury to the gallbladder is also a central pathogenic feature ^2,9. A rare cause of acalculous cholecystitis occurring in patients with advanced cancer is gallbladder metastases ¹⁰.

Radiographic features

Generally, ultrasound is needed to confidently exclude the presence of gallstones.

Ultrasound

May show gallbladder wall oedema, pericholecystic fluid, and gallbladder distention (the first two considered the two most important criteria ²). The sonographic Murphy sign may be positive. A sonolucent intramural layer or “halo” that represents intramural oedema may also be present.

A sonogram may be considered highly suggestive of the diagnosis with two of the following major criteria, or one major and two minor criteria fulfilled ¹⁴;

• major criteria
  • gallbladder wall thickness >3 mm
  • wall striation
  • pericholecystic fluid
  • sonographic Murphy sign
  • intramural gas
  • mucosal sloughing
• minor criteria
  • echogenic bile or sludge in the lumen
  • transverse diameter >5 cm

Scintigraphy

Tc-99m iminodiacetic acid cholescintigraphy is considered a highly reliable test and may be performed even in acutely ill patients. Ideally, there is non-visualisation of the gallbladder.

Treatment and prognosis

The importance of recognising acalculous cholecystitis lies in the fact that these patients have a high rate of recurrence when treated with medical management. As such, cholecystectomy is the definitive treatment. However, patients that are not fit for surgery can undergo percutaneous or endoscopic biliary drainage as an alternative therapy, though cholecystectomy may still be performed when the patient improves.