Gallbladder

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Gallbladder

The gallbladder (or cholecyst sometimes gall bladder) is a pear-shaped organ that stores about 50 mL of bile (or "gall") until the body needs it for digestion. The gallbladder is about 7-10cm long in humans and is dark green in appearance due to its contents (bile), not its tissue. It is connected to the liver and the duodenum by the biliary tract.

Anatomy

Not all mammals have gallbladders. The rat and horse, for example, do not have a specialized organ for the storage of bile. The gallbladder is connected to the main bile duct through the gallbladder duct (cystic duct or, in Latin, ductus cysticus). The main biliary tract runs from the liver to the duodenum, and the cystic duct is effectively a "cul de sac", serving as entrance and exit to the gallbladder. The surface marking of the gallbladder is the intersection of the mid-clavicular line (MCL) and the transpyloric plane, at the tip of the ninth rib. The blood supply is by the cystic artery and vein, which run parallel to the cystic duct. The cystic artery is highly variable, and this is of clinical relevance since it must be clipped and cut during a cholecystectomy.

Microscopic anatomy

The gallbladder has an epithelial lining characterised by recesses called Aschoff's recesses, which are pouches inside the lining. Under the epithelium there is a layer of connective tissue, followed by a muscular wall that contracts in response to cholecystokinin, a peptide hormone secreted by the duodenum.

Function

The gallbladder stores bile, which is released when food containing fat enters the digestive tract, stimulating the secretion of cholecystokinin (CCK). The bile emulsifies fats and neutralizes acids in partly digested food. After being stored in the gallbladder, the bile becomes more concentrated than when it left the liver, increasing its potency and intensifying its effect on fats.

Role in disease

Cholestasis

Cholestasis is the blockage in the supply of bile into the digestive tract. It can be "intrahepatic" (the obstruction is in the liver) or "extrahepatic" (outside the liver). It can lead to jaundice, and is identified by the presence of elevated bilirubin level that is mainly conjugated.

Bilary colic

This is when a gallstone blocks either the common bile duct or the duct leading into it from the gallbladder. This condition causes severe pain in the right upper abdomen and sometimes through to the upper back. It is described by many doctors as the most severe pain in existence, between childbirth and a heart attack. Other symptoms are nausea and vomiting, diarrhea, bleeding caused by continuous vomiting, and dehydration caused by the nausea and diarrhea. Another more serious complication is total blockage of the bile duct which leads to jaundice, which if it is not corrected naturally or by a surgical procedure can be fatal as it causes liver damage. The only long term solution is the removal of the gall bladder.

Cholelithiasis

Up to 25% of all people have gallstones (cholelithiasis), composed of cholesterol, lecithin and bile acids. These can cause colicky shooting abdominal pain, usually in relation with the meal, as the gallbladder contracts and gallstones pass through the bile duct. Surgery (cholecystectomy, removal of the gallbladder) is the most common treatment for gallstones. It can be performed laparoscopically, and it is in fact one of the most common procedures done through the laparoscope.

People traditionally considered at an increased risk of cholelithiasis are people who are 4 F's:

Female
Fat (obesity)
Fair (Caucasian, but this is disputed by recent studies)
Forty (middle-aged)

Cholecystitis

Please refer to main article: Cholecystitis

Acute or chronic inflammation of the gall bladder causes abdominal pain. 90% of cases of acute cholecystitis are caused by the presence of gallstones. The actual inflammation is due to secondary infection with bacteria of an obstructed gallbladder, with the obstruction caused by the gallstones.

Choledocholithiasis

Please refer to main article: Choledocholithiasis

When gallstones obstruct the common bile duct, the patient develops jaundice and liver cell damage. It is a medical emergency, requiring endoscopic or surgical treatment.

Gallstone ileus

A rare clinical entity is ileus (bowel obstruction) by a large gallstone, or gallstone ileus. This condition develops in patients with longstanding gallstone disease, in which the gallbladder forms a fistula with the digestive tract. Large stones pass into the bowel, and generally block the gut at the level of Treitz' ligament or the ileocecal valve, two narrow points in the digestive tract. The treatment is surgical.

Gallbladder Cancer

Cancer of the gallbladder is a rare but highly fatal disease. It has been associated with gallstone disease, estrogens, cigarette smoking, alcohol consumption and obesity. Despite aggressive modern surgical approaches, advanced imaging techniques, and endoscopy, nearly 90% of patients die from advanced stages of the disease and experience pain, jaundice, weight loss, and ascites.

Gallbladder Polyps and Primary Scerlosing Cholangitis

Polyps (growths) are sometimes detected during diagnostic tests for gallbladder disease. Small gallbladder polyps (up to 10 mm) pose little or no risk, but large ones (greater than 15 mm) pose some risk for cancer, so the gallbladder should be removed. Patients with polyps 10 mm to 15 mm have a lower risk but they should still discuss removal of their gallbladder with their physician. Of special note is a condition called primary sclerosing cholangitis, which causes inflammation and scarring in the bile duct. It is associated with a lifetime risk of 7% to 12% for gallbladder cancer. The cause is unknown, although primary sclerosing cholangitis tends to strike younger men who have ulcerative colitis. Polyps are often detected in this condition and have a very high likelihood of malignancy.

External links

Abdomen | Digestive system | Hepatology

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