Acute cholecystitis is a condition characterized by gallbladder wall inflammation. Patients classically present with right upper quadrant (RUQ) abdominal pain, fever, and leukocytosis. There are 2 main types of acute cholecystitis: calculous and acalculous.
Acute calculous cholecystitis: Constitutes 90%-95% of all cases. Gallstones obstruct the cystic duct, resulting in acute inflammation of the gallbladder wall. There are 2 primary types of gallstones:
- Cholesterol gallstones – Approximately 80% of all gallstones in the United States.
- Pigmented gallstones – Made of calcium bilirubinate and calcified bilirubin. This type of gallstone can be either black or brown. Black stones comprise 20% of all gallstones and are found in patients with chronic hemolytic anemia, Gilbert syndrome, liver cirrhosis, or cystic fibrosis. Brown gallstones are more common in the Asian population, and they develop in the setting of chronic biliary tract infection such as parasitic infections.
Pathophysiology of acute cholecystitis: About 10% of the population has gallstones. In most people, gallstones are asymptomatic. Biliary colic develops in 1%-4% of patients annually, and acute cholecystitis eventually develops in about 20% of patients with symptomatic gallstones if an elective cholecystectomy is not performed. The presence of gallstones alone is not predictive of acute cholecystitis. However, patients who are symptomatic from gallstones should consider cholecystectomy to prevent future development of acute cholecystitis.
Acute calculous cholecystitis is caused when a gallstone blocks the cystic duct, impairing gallbladder drainage. Temporary obstruction can cause biliary colic. Sustained obstruction can result in gallbladder wall inflammation, subsequent wall thickening, and pericholecystic fluid accumulation.
Inflammation is sterile in early cases, but secondary infection develops in most patients. Common organisms are Enterobacteriaceae (Escherichia coli, Klebsiella spp, Enterobacter spp), Enterococcus spp, and anaerobes (Bacteroides spp, Clostridium spp, Fusobacterium spp).
Demographics and risk factors of acute cholecystitis:
Sex – Women are more likely to develop gallstones because of higher estrogen levels. For the same reason, pregnancy and hormone replacement therapy increase the risk of gallstones. Approximately 25% of women older than 60 have gallstones. Cholecystitis develops in women more frequently due to the relative prevalence of gallstones.
Age – Gallstones are unusual in children. In cases when they occur, they are commonly pigment stones. The following conditions put children at a higher risk of having gallstones:
- Spinal injury
- History of abdominal surgery
- Sickle cell disease
- Impaired immunity
- Intravenous (IV) nutrition
Obesity and weight changes – In obesity, the liver overproduces cholesterol, which increases the risk of gallstone formation. Rapid weight loss is also a risk factor for the development of cholesterol gallstones.
Pregnancy – Increase in cholesterol saturation of bile and impaired gallbladder contraction during pregnancy predispose to formation of cholesterol stones or biliary sludge.
Genetics – Having a family member with gallstones increases one's risk. Mutation of gene ABCG8 increases the risk of gallstone formation.
AIDS – Biliary disease occurs via 2 mechanisms in patients with AIDS:
- Acute acalculous cholecystitis
- AIDS cholangiopathy (commonly due to Cryptosporidium or cytomegalovirus)
Ascariasis – This is a geographical risk factor in regions such as China and Southeast Asia. It can cause cholecystitis, cholangitis, hepatic abscess, or even pancreatitis.
Clinical manifestations of acute cholecystitis:
RUQ pain – Can be episodic or sustained, severe, and located in the RUQ or epigastrium that can radiate to the shoulder or back. Exacerbated by eating, particularly fatty meals, and at night. Pain from biliary colic is episodic. Acute cholecystitis is classically accompanied by prolonged episodes of pain.
Physical examination findings – Tenderness and guarding in the RUQ and Murphy's sign.
Murphy's sign –
- Arrest in inspiration while palpating the gallbladder during a deep breath.
- Sensitivity of 50%-60% and a high specificity of up to 79%-96%.