Jaundice is caused by an accumulation of bilirubin in the bloodstream. Bilirubin is a yellow pigmented substance that is one of the end products of the breakdown of the hemoglobin molecule that carries oxygen in the red blood cells. When red blood cells are broken down hemoglobin is metabolized by the body into bilirubin. Bilirubin is metabolized by the liver so that it is either excreted in the bile or conjugated so that it can be excreted in the urine. When bilirubin accumulates in the bloodstream it causes a yellow hue to the skin and eyes, called jaundice. When the accumulation is caused by a blockage of the outflow of bile from the it is called obstructive jaundice.
As the bile is produced in the liver it drains through increasingly large bile ducts, like the twigs of a tree branch come together to larger and larger branches and finally to the trunk. The common bile duct is like the trunk of the bile duct system and drains into the first part of the small bowel a few inches distal to the outlet of the stomach.
The digestive juices from the pancreas also drain into the common bile duct, and a side branch of the common bile duct leads to the gall bladder. The common bile duct has a muscular sphincter at it’s entrance to the small bowel called the Sphincter of Oddi, that is squeezed closed most of the time, and opens when food in the stomach sends a chemical signal to the sphincter to relax and allow bile to drain. When the sphincter is closed bile backs up into the gall bladder where it is concentrated and stored. The same chemical, cholecystokinin, that causes the sphincter to relax causes the gall bladder to contract and squirt out bile.
This anatomic proximity of the common bile duct and the head of the pancreas and the gall bladder make it at risk to become blocked, or obstructed by several conditions. When gall stones develop and a gall stone blocks the common bile duct there is usually significant pain. This can be associated with jaundice, but the jaundice is usually painful.
Painless jaundice can occur when the obstruction to the outflow of bile is very gradual in onset. The conditions that cause painless jaundice are usually much more serious, and cancers of the pancreas or the bile duct are the most common causes. By the time jaundice occurs the cancers are often too advanced for successful treatment. Painless jaundice is an ominous sign to physicians.
Jaundice can also be caused by disease of the cells of the liver. In general these problems cause release of enzymes that usually are stored inside the liver cells into the bloodstream in large numbers. The commonly measured serum enzymes measured are called AST and ALT. In hepatocellular disease these are often very elevated. In obstructive jaundice the enzymes of the bile ducts are often elevated much more than these transaminases. The enzyme alkaline phosphatase (Alk Phos) is typically elevated much more than the AST or ALT in obstructive jaundice.
To evaluate a patient with suspected obstructive jaundice a test to visualize the anatomy of the bile ducts is usually performed. Often this starts with an abdominal ultrasound. Ultrasound is especially good at visualizing gall stones, because the solid stones reflect ultrasound waves really well and show up easily. CT scan is often needed to evaluate for pancreatic masses or solid lesions in the liver. If an obstruction is found a procedure called endoscopic retrograde cholangiopancreatography (ERCP) where a scope is used to go through the mouth, esophagus and stomach and into the small intestine, the opening of the common bile duct into the duodenum is located, and a small tube is passed into the common bile duct and dye injected to get excellent x-ray images of the common bile duct and the pancreatic ducts. It an obstruction is found, sometimes a stent (tube to make an opening past the obstruction) can be passed upward past the blockage to relieve the obstruction.
Jaundice symptoms associated with obstructive jaundice are often severe itching without a rash. This can be difficult to treat, but sometimes the medications that bind to bile acids like cholestyramine can be used to help with the itching.