Extrahepatic obstruction

The term cholestatic jaundice is used to include all cases of extrahepatic obstructive jaundice. It also covers those cases of jaundice that exhibit conjugated hyperbilirubinemia due to micro-obstruction of intrahepatic biliary ductules by swollen, damaged hepatocytes (eg, as may occur in infectious hepatitis). 

In addition to drugs administered specifically to produce a metabolic effect, there are drug-related physiological changes that cause laboratory test abnormalities. Many drugs have been associated with the appearance of abnormal liver function tests in a fashion that simulates extrahepatic obstruction. These drugs include, among others, chlorpromazine, cinco-phen, methyltestosterone, thiouracil, p-aminosalicylic acid, sulfadiazine, reserpine, meprobromate, novobiocin, caffeine, and phenacemide (L7, L8, S6). 

Local anesthetics containing an amide linkage are metabolized principally by the liver.Thus, patients with hepatic disease may be more likely to exhibit toxic effects from the injectable anesthetics. Local tissue infiltration or nerve blocks should be avoided or performed using minimally effective anesthetic doses in patients with hepatitis, cirrhosis, extrahepatic obstruction (e.g., lithiasis), or other clinically significant hepatic dysfunction. 

The sensitivity of CT for the confirmation of focal lesions is 84-96%, with a specificity of 86-100%. Differentiation between intra- and extrahepatic obstruction was successful in 77-97% of cases the location of the obstruction was clarified in 79-98%, and the aetiology of the obstruction was established in up to 76% of cases. 

Extrahepatic obstructive jaundice is caused by stenos-ing processes. The region of Vater s papilla is particularly affected, for example by inflammations, stones, duodenal diverticula, carcinoma, parasites, cicatricial stenosis or adenomatosis. In this respect, special mention should also be made of carcinoma, cicatricial strictures and gallstones (s. figs. 8.14, 8.15 32.1, 32.15), compression of the common bile duct due to a cystic duct stone (= Mirizzi syndrome), haemobilia, and various parasites - such as Ascaris lumbricoides (s. fig. 25.8 ). All of these disorders can be found in the area of the extrahepatic bile ducts. (9, t9)... 

Tab. 13.2 Causes of extrahepatic obstructive cholestasis (with or without initial jaundice however, consecutive jaundice may develop later)...

Fig. 13.5 Bilirubinostasis with bile droplets (->) in the hepatocytes and canaliculi. Clinical diagnosis extrahepatic obstructive jaundice...

Mohapatra, M.K., Mohapatra, A.K., Acharya, S.K., Sahni, R, Nundy, S. Encephalopathy in patients with extrahepatic obstruction after li-enorenal shunts. Brit. J. Surg. 1992 79 1103-1105... 

The response of the liver to any form of biliary tree obstruction induces the synthesis of ALP by hepatocytes. Some of the newly formed enzyme enters the circulation to increase the enzyme activity in serum. The elevation tends to be more notable (greater than threefold) in extrahepatic obstruction (e.g., by stone or by cancer of the head of the pancreas) than in intrahepatic obstruction and is greater the more complete the obstruction. Serum enzyme activities may reach 10 to 12 times the upper reference limit and usually return to normal on surgical removal of the obstruction. A similar increase is seen in patients with advanced primary liver cancer or widespread secondary hepatic metas-tases. Liver diseases that principally affect parenchymal cells, such as infectious hepatitis, typically show only moderately (less than threefold) increased or even normal serum ALP activities (Table 21-3). Increases may also be seen as a consequence of a reaction to drug therapy. Intestinal ALP... 

Extrahepatic obstruction Stones Carcinoma Stricture Atresia... 

Conjugated hyperbilimbinemia is rare during the neonatal period. It can result from impaired hepatocellular function or extrahepatic obstmction. Hepatocellular defects can be caused by bacterial, viral, or parasitic infections, cystic fibrosis, a -antitrypsin deficiency, Dubin-Johnson and Rotor s syndromes, and other genetic disease. Extrahepatic obstruction can be congenital (biliary atresia) or acquired. 

Thus, De Schepper (D14) found an increase in blood pyruvate in acute viral hepatitis and in different varieties of hepatic cirrhosis the highest values were obtained during hepatic coma, whereas no elevation in blood pyruvate was observed in eases of jaundice due to extrahepatic obstruction. Other authors (A4, G17) found normal values in well-compensated cirrhosis. 

CT scanning is an invaluable Uxil in the investigation of the jaundiced patient. The dilated bile ducts are clearly visible in a CT scan of a patient with extrahepatic obstructive jaundice due to carcinoma of the head of the pancreas (Fig. 4). 

---