Acalculous cholecystitis

The majority of cholecystitis events in the ICU are acalculous. The severity of this condition among the critically ill demands this condition be treated in sufficient detail by the exam candidate. It has appeared several times, and every time in the same way, in the following identical repeated series of SAQs:

• Question 1 from the second paper of 2019
• Question 17 from the second paper of 2008
• Question 8 from the second paper of 2002

Each time, the candidates were called upon to  "outline  the clinical manifestations, appropriate investigations, and treatment of acalculous  cholecystitis." Probably the single best reference for this topic is this 2010 review article by Huffman and Schenker. Unless otherwise specified, the information in this quick summary is derived from their work.

Why is this specific to the ICU?

Unlike most of the cholecystitis outside the ICU, these gall bladders are inflamed without stones. The inflammation is frequently more severe, and the progression to gangrene and septic shock is more likely.

The most likely comorbidities in the ICU are trauma, burns and sepsis.

Risk Factors for Acalculous Cholecystitis

Strongly associated factors Trauma with massive transfusion Any recent surgery Burns Sepsis TPN Prolonged fasting Critical illness in general

Weakly associated factors ERCP Long hospital stay Immunosuppression Vasculitis CBD obstruction Obesity, diabetes, hypertension

Mechanism of pathogenesis

This environment, with a defenceless ischaemic gall bladder wall, gives rise to bacterial translocation into said wall. The typical features of this, on ultrasonography, include a distended gallbladder with a thickened wall and neither gallstones nor sludge inside. The wall may be emphysematous (suggesting that it is gangrenous and gas-forming anaerobes are migrating across it) and there may be gas bubbles in the gall bladder itself (the so-called “champaigne sign”). Pericholecystic fluid may be present, suggesting that inflammation is occurring; alternatively the CT abdomen may reveal a perforated gall bladder, and a collection forming in its ruins.

Unfortunately, there are no specific clinical findings that establish the diagnosis.
It therefore rests on imaging.

Radiological and Ultrasonographic Features of
Acalculous Cholecystitis

Thickened gall bladder wall (over 3.5-4mm) Pericholecystic fluid Intramural gas Echogenic or hyperdense bile sludge Sloughed mucosa Gall bladder distension

A HIDA cholescintigraphy study is another specialised option. HIDA stands for ⁹⁹Tc^m-labelled hepatic iminodiacetic acid. It (or one of its various analogues) is administered IV, and its excretion into the gall bladder is measured. If the presence of the isotope is not detected in the gall bladder after 4 hours, some sort of biliary obstruction must be present. If the isotope fills the gall bladder, a fatty meal or cholecystokinin can then be administered to force the gall bladder to contract; a gall bladder ejection fraction (GBEF) of over 40% represents normal function. Generally speaking, this modality is used when the ultrasonographic and CT findings are equivocal. It can predict outcome and direct therapy: of the patients with a normal GBEF, the majority (up to 90%) end up symptom free after three months with only conservative management. One rarely needs to resort to this; authors of one study of acalculous cholecystitis remark that "hepatobiliary scintigraphy, which is used when the diagnosis is difficult, was not deemed necessary in any of the patients in this series".

Management

The management of this condition does not vary massively from the normal management of acute cholecystitis.
One may wish to cover for E.coli and Klebsiella as well as Proteus, Enterococcus and Bacteroides. Typically the surgical “triple therapy” covers for all these organisms, but keeping in mind that this condition occurs in ICU patients frequently already on antibiotics one may wish to broaden the cover or add an antifungal agent.

Options for Management of Acalculous Cholecystitis

Option	Advantages	Disadvantages
Conservative (antibiotics)	Few complications May be the only option for high risk patients. In a mixed (calculous and acalculous) group, 87% of conservatively managed patients recovered completely. Patients with reasonably normal gall bladder function (over 40% GBEF) only need conservative management. There is still an option to progress to one of the other treatment options.	May delay definitive treatment The gallbladder may become necrotic and rupture, causing peritonitis Patients with a severely infected gall bladder will continue to get worse, as source control has not been achieved.
Percutaneous cholecystostomy	Fewer complications than open cholecystectomy Can serve as the definitive management option in 80% of cases Safe with ultrasound or CT guidance	No difference in mortality and morbidity when compared to laparoscopic cholecystectomy (but this was a population of patients who were not critically ill) Risk of drain dislodgement
Laparoscopic cholecystectomy	Fewer complications than open cholecystectomy A definitive management option	Not an option in some patients, particularly morbidly obese patients and those with severe respiratory failure Requires a surgeon familiar with the approach May end up converting to open anyway, losing all benefits of the laparoscopic approach.
Open cholecystectomy	A definitive management option. Allows for a thorough washout. Accomodates weird anatomy and allows earlier maagement of surgical complications. May be the only option for those with a gangrenous or perforated gall bladder.	Significant morbidity post operatively in the critically ill population (mortality may be up to 19%)

Ideally, to fix this problem surgically is the solution, but practically speaking this is going to be difficult in the critically ill patient.  Percutanous cholecystostomy may be the only answer; of those who respond the majority experience and improvement withn 48 hours- but in 41% it seems to make no difference to the severity of their shock, suggesting that in these patients the thick distended gallbladder was mistaken as the source of sepsis. Additionally, putting a tube though somebody’s abdominal wall is non a consequence-free step, and there are reports of horrible complications like bleeding from the liver. The drain may also dislodge during pressure area care, resulting in a spray of infected bile all over the peritoneum.