Cholelithiasis - etiology, pathogenesis, clinical features
Etiology and overview
High prevalence (10-15%), risk factors are the four F’s:
- Fat
- Forty +
- Female
- Fertile
Fundamentally, gallstone formation is due to failure to maintain biliary solutes, primary cholesterol and calcium salts in a solubilized state. Gallstones can either by pigmented stones or cholesterol stones (pigmented forms can be black or brown), the vast majority are cholesterol stones. Note, black pigment stones are often visible on x-ray, while cholesterol stones are usually invisible.
Pathogenesis
Cholesterol stones are formed due to excess cholesterol relative to bile salts and phospholipids, meaning the bile becomes supersaturated and the excess cholesterol forms crystals. These crystals embed in the gallbladder mucin with bilirubin to form a biliary sludge, from whence they can congregate to a gallstone.
Black pigment stones consist of polymerized calcium bilirubinate, a result of excessive calcium and unconjugated bilirubin. These types of stones are more common in patients who have excessive amounts of unconjugated bilirubin (e.g. chronic hemolytic anemia), they are typically found in the gallbladder.
By contrast, brown pigment stones are typically found in the bile ducts. They are the result of a bacterial infection that releases enzymes that cause precipitation of calcium, bilirubin and FFAs that result in the formation of brown pigment stones. Brown pigment stones are common in Asian communities.
A loss of gallbladder contractility is also seen in some patients with gallstones, it is thought that this loss can be both a causative factor for gallstones and a result.
Clinical features
Patients can be asymptomatic (of which only a small percentage go on to develop complications) or symptomatic. The main manifestation is pain termed biliary colic, caused by blockage of the cystic duct and therefore increase in gallbladder tension. Association with meals is about 50% of patients, and occurs in episodes, duration of pain is typically 1-5 hours, although can last all day. Other symptoms include nausea, bloating and vomiting along with jaundice (although this isn’t so common).
Diagnosis is via transabdominal ultrasound, where we look for a shadow. Treatment is operative management, commonly via a laparoscopic cholecystectomy. Nonsurgical options are rarely used.
Image: “Ultrasonography of sludge and gallstones, annotated” by Mikael Häggström , M.D. Author info - Reusing images - Conflicts of interest: None Mikael Häggström , M.D. Consent note , CC0, via Wikimedia Commons.