Editing 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

=== Cholesterol emboli ===

=== Haemobilia ===

=== 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 [[Acute calculous cholecystitis|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.
[[Category:Biliary]]