Acalculous cholecystitis

Blockage of the cystic duct in the absence of stones

Epidemiology

• Accounts for 5% of cholecystitis
• Typically occurs in critically unwell patients, but certainly CAN occur in otherwise well patients, although they usually have risk factors

Risk factors

Anatomical

• • Ampullary stenosis
  • Choledochal cyst
  • Cystic duct obstruction by some sort of CBD stent/PTC
  • Metastases to porta hepatis

Acute events

• • Critical illness including CPR
  • Prolonged TPN
  • Major trauma
  • Burns
  • Childbirth
  • Mechanical ventilation
  • Multiple transfusions
  • Non-biliary surgery
  • Sepsis/hypotension

Chronic morbidity

• • Coronary heart disease
  • CKD
  • Diabetes
  • CCF
  • Old age
  • Vasculitis

Immunosuppression

• • AML
  • AIDS
  • BM transplantation

Medications

• • Opioids
  • Sunitinib

Specific primary infections

• • Ascaris lumbricoides
  • Brucella
  • Campylobacter jejuni
  • Candida
  • Coxiella burnetii
  • Cryptosporidium
  • CMV
  • Echinococcus granulosis
  • EBV
  • Flavivirus
  • HBV and HAV
  • Isospora
  • Leptospira
  • Mycobacterium tuberculosis
  • Plasmodium
  • Salmonella
  • Vibrio cholerae

Pathophysiology

• Poorly understood
• Probably involves bile stasis (prolonged fasting) and GB ischaemia (low-flow state), which then causes GB distension and a local inflammatory response in the GB wall
• Once acalculous cholecystitis is established, secondary infection with enteric pathogens is common
• Can progress to gangrenous GB in about 50%
• Perforation is said to occur in 10%

Presentation

• Generally similar to that seen in calculous cholecystitis
• Critically ill patients may just have fever and may not have RUQ pain - consider as a cause of PUO in this setting, especially with imaging findings
• A smouldering disease with recurrent symptoms for months may reflect either gallstone-related disease or a functional GB disorder

Imaging

• USS first-line
  • >4mm wall thickness
  • Sonographic Murphy's sign
  • Pericholecystic fluid/subserosal oedema
  • However, most critically unwell patients in ICU will have at least one abnormal GB finding on USS, so the specificity is questionable (84% have one abnormal findings, and 57% have three or more)
• CT second-line - also excludes other causes
  • Gas in GB wall or lumen, lack of GB wall enhancement, and oedema around the GB have the highest specificity (99, 95 and 92% respectively) but all have poor sensitivity
• HIDA scan is diagnostic if a third-line study is required, but can have a false positive result
  • Failure to opacify the GB at one hour is a positive test
  • Specificity 58-88%

Diagnosis

• Generally made in patients with all of the following:
  • Clinical manifestations suggestive of cholecystitis
  • Risk factors for acalculous cholecystitis
  • Suggestive radiologic features
  • No evidence of other conditions

Differential diagnosis

• Acute calculous cholecystitis with missed gallstones on USS
• Wall thickening/oedema is also seen in:
  • Hypoalbuminaemia
  • Ascites
  • Sludge
  • Non-shadowing stones
  • Gallbladder cancer/adenomyomatosis
  • Chronic liver disease/hepatitis
  • Right heart failure
  • Fluid overload from kidney disease including nephrotic syndrome
  • Pancreatitis
  • Blockage of venous or lymphatic drainage of GB
  • Multiple myeloma
  • Pyelonephritis (reactive)
  • Systemic infection (viral or bacterial)
  • Brucellosis
  • Dengue
  • AIDS

Management

• As per calculous cholecystitis
• In most patients with true 'ICU' acalculous cholecystitis, start off with antibiotics, step up to perc cholecystostomy if not improving after a few days, and finally step up to cholecystectomy if still not improving
• Higher morbidity and mortality than calculous
• Percutaneous cholecystostomy is a much more attractive option - >90% of patients improve, and interval cholecystectomy is only necessary if follow-up imaging continues to demonstrate the positive findings
• GB necrosis, emphysematous cholecystitis, and perforation require cholecystectomy
• Failure to improve within 24 hours after cholecystostomy suggests gangrenous cholecystitis, catheter dislodgement, bile peritonitis, or an incorrect diagnosis. Rescue cholecystectomy is generally required to avoid imminent death.
• Remove the cholecystostomy tube when cholecystitis resolves and drainage is minimal (<10mL per day, which is usually 4-6 weeks later). Repeat the USS to exclude stones/sludge.