Acalculous cholecystitis is the term for inflammation of the gallbladder that is not due to the presence of gallstones. Most cases of acute cholecystitis (inflamed gallbladder) occurs due to gallbladder stones (within the gallbladder) or biliary stones (lodged in the bile duct). In these cases it is referred to as calculous cholecystitis. Since it is so common, acute cholecystitis is considered to be synonymous with calculous cholecystitis. It is therefore important to differentiate acalculous cholecystitis specifically. Although it is less common, acalculous cholecystitis is associated with more serious complications, some of which can be life-threatening.
Cholecystitis is a fairly common condition and gallbladder removal (cholecystectomy) is the most commonly conducted major surgery done by general surgeons in the United States. Acute cholecystitis is more common after the age of 40 years and the risk increases progressively with age. Only about 10% of acute cholecystitis cases are not due to gallstones (acalculous cholecystitis). The other 90% of cases are therefore calculous cholecystitis – gallbladder inflammation due to gallstones.
The gallbladder is the reservoir for bile, the liquid substance containing cholesterol and wastes produced by the liver. The gallbladder is a hollow thin-walled organ that can distend to accommodate the bile that it holds. This bile is drained first through the cystic duct and then through the common bile duct to be passed out into the small intestine. Although the gallbladder is not essential for life, it does play an important role in digestion. By releasing large amounts of bile during digestion, particularly in response to the presence of fatty foods in the gut, bile emulsifies fats.
Inflammation is the body’s response to injury. It is a protective mechanism intended to limit the damage to body. Inflammation of the gallbladder simply means that the organ is experiencing some sort of injury and the body is responding to this stimulus. Once the stimulus is removed and inflammation subsides, the body’s healing processes can repair the damage where possible. While the mechanism behind gallbladder inflammation due to gallstones (calculous cholecystitis) is better understood, it is not always as clear with acalculous cholecystitis.
It appears that gallbladder inflammation in acalculous cholecystitis, where the injury is not always clearly identifiable, is a result of ischemia in many instance. This is a type of injury that arises with interruption in blood supply. The more favored reason behind the pathophysiology of acalculous cholecystitis in severely ill patients is inflammation due to biliary stasis. This means that the gallbladder is not contracting and releasing bile as normal. The bile becomes more viscous (thicker consistency) and may form biliary sludge which is not an actual gallstone but can cause inflammation in a similar manner to calculous cholecystitis.
The symptoms of acalculous cholecystitis are largely the same as acute calculous cholecystitis. However, patients who usually suffer with acalculous cholecystitis are often extremely ill and the symptoms of underlying disorders may be more prominent. Some patients who are debilitated may be unable to report all of the symptoms and the only clinical sign that is present is a distended abdomen, usually with fever. Sometimes even these symptoms can be attributed to the underlying cause and therefore difficult to isolate it as being due to acalculous cholecystitis.
- Unexplained fever
- Abdominal distension
- Tenderness of the abdomen
- Abdominal discomfort or pain, usually in the right upper quadrant (RUQ)
- Elevated white blood cell count (leukocytosis)
Vomiting, loss of appetite, weakness and malaise are non-specific symptoms of acute cholecystitis. In acalculous cholecystitis, these symptoms are more likely due to the underly cause of gallbladder inflammation.
Severe and untreated cholecystitis can lead to complications like :
- Perforation of the gallbladder – tear in the gallbladder wall with its contents spilling into the abdominal cavity.
- Gangrene of the gallbladder – portion of the gallbladder wall dies and decomposes.
Patients with these complications may go into shock, experience peritonitis or develop sepsis.
Acalculous cholecystitis tends to occur in patients who are severely ill. It is believed that an underlying disorder that impairs circulation to the gallbladder via the cystic artery then leads to ischemia. Another possibility is that since critically ill patients are not eating, the gallbladder is not stimulated to contract and release bile. Gallbladder dysmotility may also be seen with pregnancy and certain liver disorders. Subsequent bile stasis and sludge formation causes inflammation. Infection is another possible cause of acalculous cholecystitis.
There are certain factors that increases the risk of developing acalculous cholecystitis.
- Abdominal trauma
- Elderly people
- Extensive burns
- Heart failure
- HIV infection and AIDS
- Infection of the bile duct
- Postoperatively, especially after surgery to the abdomen
- Prolonged labor
- Septicemia (“blood poisoning”)
- Severe and prolonged infections with high fevers
Various laboratory tests are done to identify the cause of acalculous cholecsystitis. These tests usually do not confirm the diagnosis. Other investigations that should be conducted are imaging studies. This includes :
- Ultrasound of the right upper quadrant (RUQ)
- Computed tomography (CT) scan of the abdomen
- Cholescintigraphy (HIDA) scan
Most of these imaging studies are conducted to confirm or exclude the presence of gallstones, identify any complications of cholecystitis and assess the severity of the condition. The gallbladder wall will appear thickened and there may be fluid around the gallbladder (pericholecystic fluid) as a result of inflammation.
Patients should be managed in the hospital settings. Intravenous (IV) administration of fluids is usually necessary. Medication for pain management should be avoided in patients who are critically ill. Antibiotics are the only drugs that should be considered and only for calculous cholecystitis associated with bacterial infections.
The treatment for acalculous cholecystitis is surgical removal of the gallbladder (cholecystectomy). However, acalculous cholecystitis often occurs in patients who are severely ill and therefore surgery may not always be advisable at that point in time. Interim measures include :
- Endoscopic gallbladder stent placement
- Percutaneous cholecystostomy
These procedures facilitate drainage of the gallbladder either directly into the duodenum of the small intestine or externally into the environment through a catheter. Once the patient improves, a cholecystectomy should be done. The procedure can be done laparaoscopically or with open surgery. Ideally a cholecystectomy should not be delayed due to the high risk of complications in acalculous cholecystitis, which are often severe and life threatening.