DISEASE OF THE BILIARY TRACT

Congenital abnormalities

Biliary atresia

Biliary atresia has an incidence of 1 in 12 000 live births and presents in the first week of life as cholestatic jaundice. Untreated it pursues a relentless course, with progressive liver failure and death before the age of 3 years. The cause of the atresia is unknown, but failure of vacuolation of the solid biliary bud in the early weeks of intrauterine life is one possible explanation. Inflammatory obliteration of previously patent ducts occurring about the time of birth is currently considered to be the cause. Viruses and metabolic disorders are two possible causes of such inflammation.

 

Classification

Three pathological types of atresia are recognized: Type 1, atresia of the common bile duct; Type 2, atresia of the common hepatic duct; and Type 3, atresia of the right and left hepatic ducts. Types 1 and 2 are relatively easy to correct surgically. In Type 3 disease there is often a conical area of fibrous tissue at the hilum of the liver which contains within it multiple small biliary radicals. The number of these ducts decreases with time and this adds to the urgency of diagnosis.

 

Diagnosis

Biliary atresia is notoriously difficult to diagnose. Jaundice in the newborn can be caused by hepatocellular disease, intrahepatic bile duct hypoplasia, or a choledochal cyst, as well as biliary atresia. Conventional methods of investigation which are useful in adults are less valuable in infants. For example there is rarely any intrahepatic duct dilatation, so that ultrasound is of limited help. Histological examination of a liver biopsy is the most reliable method of diagnosis, but in clinical practice a range of tests is usually needed.

 

Treatment

The discovery on microscopy of small biliary radicals in the fibrous tissue at the hilum of the liver has led to the development of portoenterostomy for the treatment of Type 3 biliary atresia. In this procedure all of the fibrous tissue and atretic ducts at the porta hepatis are resected en bloc. An open enterotomy in the antimesenteric border of a jejunal loop is then sutured to the edge of the fibrous tissue in the porta hepatis. Bile drains from the liver into the bowel through the tiny ducts at the liver hilum. This Kasai operation allows long-term survival of nearly half of the patients (Fig. 17) 1240. If atresia involves only the extrahepatic bile ducts, it is possible to anastomose the residual dilated hepatic ducts to a Roux-en-Y loop of small bowel. Unfortunately the results of hepaticojejunostomy are not much better than those of portoenterostomy. Various modifications of the Kasai procedure have been suggested, including bringing up the Roux loop to the skin surface in order to allow easy access to the hepatic anastomosis, but this appears to convey little advantage.

 

Bacterial cholangitis and portal hypertension are the two common complications of the Kasai operation. Cholangitis requires treatment with systemic antibiotics and the exclusion of a surgically correctable obstruction such as kinking of the Roux loop. Portal hypertension consequent upon hepatic fibrosis is a long-term problem: injection sclerotherapy is the treatment of choice for children who develop varices.

 

Even though the Kasai operation has markedly improved the management of biliary atresia the results are not completely satisfactory. However, the results of liver transplantation in children have improved so much that it is now the treatment of choice for children with end-stage liver failure (see Section 10.6 74). Since there are few paediatric liver donors it is necessary to reduce the size of an adult liver for transplantation into an infant, but the surgery and the immunosuppression is tolerated without difficulty. Portoenterostomy remains the first treatment for biliary atresia; liver transplantation is available when portoenterostomy is impossible or liver function fails.

 

Choledochal cyst

Choledochal cyst is an aneurysmal dilatation of the bile duct. It is a rare condition, with an incidence between 1: 100 000 and 1: 150 000 live births in the West, although it is probably more common in the East. Females are affected two to four times more often than are males. Most patients present in infancy, although a significant minority are diagnosed as adults.

 

Aetiology

The aetiology is unknown. Partial biliary obstruction and a weakness of the wall of the bile duct are the two basic defects required for the formation of a cyst: both these abnormalities may be congenital or acquired. Abnormal recanalization of the bile duct, which is complete by the fifth week of intrauterine development, may result in areas of stenosis and dilatation. This theory is supported by the occurrence of choledochal cysts in neonates and by the finding of multiple areas of stenosis and dilatation in some patients with a choledochal cyst. A cyst may also develop following trauma, or from fibrosis and stenosis of the distal common bile duct due to recurrent cholangitis associated with stones in the bile duct. Early changes of this type are sometimes seen at ERCP.

 

Classification

Cystic dilatation may affect any part of the biliary system: five patterns have been described. Type 1, a cystic or fusiform dilatation of the common bile duct, is the most common (82 per cent). Type 2 (3 per cent) is a supraduodenal diverticulum of the common bile duct, and Type 3 (5 per cent) is a diverticulum of the intraduodenal bile duct, or choledochocoele. Type 4 (9 per cent) consists of multiple cysts: Type 4A cysts affect both the intrahepatic and extrahepatic bile ducts, while Type 4B cysts affect the extrahepatic duct only. Type 5 (1 per cent) describes cysts of the intrahepatic bile ducts. These may be solitary or multiple, and this type includes Caroli's disease (Fig. 18) 1241. They can vary in size from 2 cm in diameter to giant cysts, and the wall is composed of fibrous tissue which may be up to 1 cm thick. The cyst is lined by cuboidal biliary epithelium, which is often ulcerated in adults.

 

Diagnosis

Choledochal cysts present either as a mass or with biliary obstruction. The classic triad of abdominal pain, jaundice, and a mass occurs in less than one-half of patients. Most adults present with jaundice or cholangitis. Infants also present with jaundice, but may vomit due to duodenal compression and may also have a palpable mass in the abdomen.

 

Ultrasonography will usually confirm the diagnosis. Cholangiography is absolutely essential to delineate the biliary anatomy accurately and thus determine the best approach to surgical treatment. ERCP is the easiest method of obtaining a cholangiogram (Fig. 19) 1242, but percutaneous and operative cholangiography may also be needed. An arteriogram to delineate the relationship of the cyst to the hepatic artery and the portal vein may be very valuable before embarking on surgical treatment.

 

Treatment

Once diagnosed the treatment of a choledochal cyst is surgical. Although numerous operations have been described, a Type 1 cyst should ideally be excised completely. The distal bile duct is then anastomosed to the small bowel& mdash; usually the jejunum via a Roux-en-Y loop. In infants the structures may be sufficiently mobile to allow use of the duodenum. Anastomoses between the cyst wall and the bowel are usually unsatisfactory in the long term. The cyst wall is often devoid of mucosa and is lined only by granulation tissue, so that a stricture develops. This leads to recurrent cholangitis and the development of stones within the cyst. The high risk of carcinoma developing in a choledochal cyst is also a reason for complete excision. This is usually possible but if it is difficult it is acceptable simply to excise the lining of the cyst and thus protect the portal vein by a partial thickness of the cyst wall. Previous surgery, recurrent cholangitis, and portal hypertension all make treatment difficult.

 

Type 2 cysts can usually be excised, the defect in the common bile duct being repaired by primary suture over a T-tube brought out through a separate incision in the duct. Small choledochoceles (Type 3) may be treated by endoscopic sphincterotomy. Larger ones require a surgical sphincterotomy using the transduodenal approach. Type 4 cysts are treated by a combination of techniques, depending on the precise anatomy in each individual case. Segmental resection of the liver may be necessary, particularly if there are intrahepatic stones, strictures, or abscesses as well as an extra-hepatic cyst. Hepaticojejunostomy is then necessary to reconstitute biliary drainage.

 

Complications

Rupture may occur spontaneously in infants, and cholangitis develops in both adults and children. Gallstones can develop within the cyst, more commonly in adults (Fig. 19) 1242. Secondary biliary cirrhosis supervenes in 15 per cent of adults with chronic bile duct obstruction. Carcinoma develops within the cyst in 8 per cent of patients and is a fatal complication. The diagnosis is usually made at operation or at autopsy. Most patients are in their thirties, and 75 per cent of tumours are adenocarcinomas, although squamous carcinoma and cholangiocarcinoma also occur. The mean survival after diagnosis is 8.5 months.

 

Acquired disease

The most common acquired abnormality of the biliary system is gallstones. In most patients these remain dormant, but they may cause biliary colic simply by mechanical obstruction. More frequently, stones lead to acute or chronic inflammation within the biliary tree and causes symptoms. Inflammation without stones can occur in both the gallbladder and the bile duct, but is unusual, as are infarction of the gallbladder and benign neoplasms of the biliary tract. Damage to the bile duct occurs rarely at the time of cholecystectomy. It may lead to the development of a benign biliary stricture, which is one of the most serious complications of biliary tract surgery. Abnormalities of biliary function probably do occur but at the present time they are poorly understood.

 

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