what is cbd obstruction

The clinical setting of cholestasis or failure of biliary flow may be due to biliary obstruction by mechanical means or by metabolic factors in the hepatic cells. For the sake of simplicity, the primary focus of this article is mechanical causes of biliary obstruction, further separating them into intrahepatic and extrahepatic causes. The discussion of intracellular/metabolic causes of cholestasis is very complex, the pathogenesis of which is not always clearly defined. Therefore, these causes are mentioned but are not discussed in detail.

Accumulation of bilirubin in the bloodstream and subsequent deposition in the skin causes jaundice (icterus). Conjunctival icterus is generally a more sensitive sign of hyperbilirubinemia than generalized jaundice. Total serum bilirubin values are normally 0.2-1.2 mg/dL. Jaundice may not be clinically recognizable until levels are at least 3 mg/dL. [2] Urine bilirubin is normally absent. When it is present, only conjugated bilirubin is passed into the urine as it is water soluble. This may be evidenced by dark-colored urine seen in patients with obstructive jaundice or jaundice due to hepatocellular injury. However, reagent strips are very sensitive to bilirubin, detecting as little as 0.05 mg/dL. Thus, urine bilirubin may be found before serum bilirubin reaches levels high enough to cause clinical jaundice.

Extrahepatic obstruction to the flow of bile may occur within the ducts or secondary to external compression. Overall, gallstones are the most common cause of biliary obstruction. Other causes of blockage within the ducts include malignancy, infection, and biliary cirrhosis. External compression of the ducts may occur secondary to inflammation (eg, pancreatitis) and malignancy. Regardless of the cause, the physical obstruction causes a predominantly conjugated hyperbilirubinemia.

Pathophysiology

To better understand these disorders, a brief discussion of the normal structure and function of the biliary tree is needed. Bile is the exocrine secretion of the liver and is produced continuously by hepatocytes. It contains cholesterol and waste products, such as bilirubin and bile salts, which aid in the digestion of fats. Half the bile produced runs directly from the liver into the duodenum via a system of ducts, ultimately draining into the common bile duct (CBD). The remaining 50% is stored in the gallbladder. In response to a meal, this bile is released from the gallbladder via the cystic duct, which joins the hepatic ducts from the liver to form the CBD. The CBD runs in the hepatodudoenal ligament and then courses through the head of the pancreas for approximately 2 cm; it joins the terminal part of the pancreatic duct to form the ampulla of Vater before passing through the papilla of Vater into the duodenum. [1]

Intrahepatic cholestasis generally occurs at the level of the hepatocyte or biliary canalicular membrane. Causes include hepatocellular disease (eg, viral hepatitis, drug-induced hepatitis), drug-induced cholestasis, biliary cirrhosis, and alcoholic liver disease. In hepatocellular disease, interference in the three major steps of bilirubin metabolism, ie, uptake, conjugation, and excretion, usually occurs. Excretion is the rate-limiting step and is usually impaired to the greatest extent. As a result, conjugated bilirubin predominates in the serum.

Disorders of the biliary tract affect a significant portion of the worldwide population, and the overwhelming majority of cases are attributable to cholelithiasis (gallstones). In the United States, 20% of persons older than 65 years have gallstones and 1 million newly diagnosed cases of gallstones are reported each year.

Biliary obstruction refers to the blockage of any duct that carries bile from the liver to the gallbladder or from the gallbladder to the small intestine. This can occur at various levels within the biliary system. The major signs and symptoms of biliary obstruction result directly from the accumulation of bilirubin and bile salts in the blood and the failure of bile to reach its proper destination.

Calling your health care provider

Treatment

Bile is a liquid secreted by the liver that contains cholesterol, bile salts, and waste products such as bilirubin. Bile salts aid in the digestion of fats. Bile passes out of the liver through the bile ducts and is concentrated and stored in the gallbladder until it is released into the small intestine after a meal to help with fat digestion.

The objective of treatment is to relieve the blockage. Stones may be removed using an endoscope during an ERCP. In some cases, surgery is required to bypass the obstruction. The gallbladder will usually be surgically removed if the biliary obstruction is caused by gallstones. Your health care provider will prescribe antibiotics for biliary obstruction if infection is suspected.

Biliary obstruction involves the blockage of any duct that carries bile from the liver to the gallbladder or from the gallbladder to the small intestine.

Risk factors include the following:

Expectations (prognosis)

Causes of obstruction include the following:

Complications