The role of the gallbladder and biliary tree in digestion

The gallbladder or gall bladder stores bile produced by the liver; it is connected to the liver by the hepatic duct. This small, pear-shaped organ lies below the liver. It is essentially a hollow pouch that can stretch to up to 4 cm in width when filled with bile.

The gallbladder is a part of the digestive system. Bile becomes concentrated during the duration of its storage in the gallbladder; this increases its effectiveness in aiding fat digestion. The concentrated bile stored in the gallbladder is released into the duodenum when fatty foods enter the digestive tract and bile stimulating enzymes are released. The bile travels down the bile ducts and enters the duodenum via the common bile duct. The bile then mixes with the pancreatic juices and helps digestion.

What is bile?

One of the many functions of the liver is to secrete bile. Bile plays an important role in fat digestion and absorption because it helps break down large fat particles and helps transport these fats through the intestinal membrane. Bile also helps serve as an important way of excreting waste products from blood.

Bile breaks up fats in the partially digested food; it also neutralizes acids. The most abundant substance in bile is categorized as bile salts. Bile also contains cholesterol, minerals, bilirubin and lecithin. The cholesterol in bile can occasionally form hard lumps and crystallize. These formations are termed gallstones. Women, obese individuals, and people above the age of 40 have a higher risk of developing gallbladder stones.

Gallstones and laparoscopic cholecystectomy

Inflammation of the gallbladder lining often results from low grade infection. This low grade infection changes the balance of water and bile salts causing cholesterol and other minerals in the bile to clump together and form gallstones. The filling and emptying of the gallbladder is likely also impaired in patients who suffer from gallstones.

In patients with gallbladder stones that cause symptoms, gallbladder removal will usually be recommended. The procedure is termed cholecystectomy and can usually be performed laparoscopically and called laparoscopic cholecystecomy.

Gallstones and Obesity

There is a clear co-relation between obesity and gallbladder stones. Similarly, those suffering from obesity-related diabetes are also at greater risk of gallbladder stones. Research shows that bile produced in the bodies of obese individuals contains more cholesterol than normal levels; this leads to formation of gallstones. Rapid weight-loss may also cause gallstones to develop. Avoiding foods rich in saturated fats can help keep the gallbladder healthy.

Obesity is not only a risk factor, but the more overweight a person is, then the greater the risk of gallstones. As Body Mass Index (BMI) increases, the risk for developing gallstones rises and patients who suffer from morbid obesity may have a risk that is many times greater than the general population. The kind of fat and the distribution of the fat may also be important. Men with more centralized fat, the fat around the abdomen that makes a person look like an apple, had a greater risk of developing symptomatic gallstones.

Biliary Tree

The biliary tract or the biliary tree serves as the path for the bile from the gallbladder to travel into the small intestine. It is referred to as a tree because several branches of this tract come together at the bile duct.

The liver forms the bile which then travels down the bile tubes. Sometimes this bile is diverted to the gallbladder where it is concentrated. Bile from the gallbladder or directly from the liver travel down the bile tubes where they intersect with the tubes of the pancreas that carry pancreatic juice and digestive enzymes. These tubes then empty into the first part of the small intestine, the duodenum.

The biliary tree can sometimes get blocked because of gallstones- this can be a serious condition requiring surgery and possibly a procedure with an endoscope to open up the bile tubes called an ERCP. Gallstones that migrate into the biliary tree can also irritate the pancreas and produce a dangerous condition called gallstone pancreatitis.

If the gallbladder is removed, then bile will travel directly from the liver into the duodenum. Although bile still flows into the intestine from the liver, fat digestion may be less efficient because the bile is not concentrated. Any clinical difference in fat digestion have not been reliably clinically proven therefore most doctors will say that having your gallbladder removed will not cause any adverse side effects.

How is digestion and bile flow changed after gallbladder removal?

In appropriately selected patients, laparoscopic cholecystecomy can greatly reduce gastrointestinal symptoms to improve quality-of-life for patients. There are hypothetical digestive changes that occur after gallbladder removal but even in large studies, these changes appear to be minor.

As the gallbladder has proximity to the pancreas during embryonic development, there could be feedback loops or other changes in digestion that have yet to be discovered. Most of the major hypothetical alterations in digestion after gallbladder removal have been carefully studied and the vast majority of scientific literature finds no significant changes after gallbladder removal.

For example, a Chinese study evaluating the possible role of gallbladder function found no statistical differences between liver function nor immune function after cholecystecomy. Bile reflux seen during endoscopic evaluation of the stomach is likely increased after gallbladder removal as investigators have seen the pH of gastric fluid change accordingly however these changes do not seem to be clinically significant. Gallbladder removal has not been shown to increase reflux symptoms (GERD) either.