Choledochal cysts are cystic dilatation of the bile duct, outside the liver or within which are congenital anomalies of the bile duct. Depending on the morphological appearance they are classified into five different types. This classification was described by Todani in 1977. At the author's center they form the second commonest Hepatobiliary disorder among children requiring surgical correction (News Letter-oct2003). The first case in the literature was reported way back in 1852 by Douglas, in a 17 year old adolescent girl who presented with the classical symptoms of jaundice, pain abdomen and a palpable mass in the abdomen.
Why do they develop?
The causation of the cystic dilatation is probably multifactorial. Majority of patients who present with choledochal cysts, have an anomalous junction of the common bile duct with the pancreatic duct (APBJ); i.e; the pancreatic duct enters the common bile duct one cm proximal to the Ampulla of Vater. This abnormality may result in reflux of the pancreatic secretions into the common bile duct with resultant activation of the pro-enzymes in the alkaline biliary environment and resultant damage of the mucosa of the common bile duct. The other theories include congenital weakness of the wall of the bile duct and defective re-cannalization of the duct during embryonic development of the organs in a foetus.
Personal views :
The condition is more common in Asia and encountered in 1 in thousand births in Japan. Females are more prone to develop it than the males (4:1). In the authors experience almost all the children who were operated belonged to the female sex. Close to 70% of the children will manifest some symptoms related to the cyst before ten years of age. However in some the disease becomes apparent only in adulthood. The author has reported one such case in the newsletter of this site, wherein the patient presented with multiple stones in the bile duct as well as within the liver at 24 years of age and was ultimately cured by removal of the bileduct along with the affected part of the liver containing the stones.
Types of choledochal cysts :
Todani in his publication in 1977, had described five anatomical variations of the choledochal cyst (Type-I to Type-V) Type-I Cysts are the commonest variety (80-90%) and they are saccular or fusiform dilataion of the entire or the major portion of the bile duct, sometimes including the segmental ducts.
The Type-II cysts are sessile cystic, protruding remnants, which may or may not retain the communication with the main duct. The type-II cysts are also termed choledochocoels, which are demonstrable only in the intraduadenal portion of the common duct. They may often have the pancreatic duct draining into them. The type-V has two subtypes, in subtype-A the
What the patient suffers form :
The child develops yellowness of eyes and urine (jaundice) and pain in abdomen. Examination by a doctor may reveal a mass in the right upper part of abdomen. They may also have fever, Nausea, Vomitting or other associated symptoms.
Sometimes, they present to the doctor for the first time with a complication in the cyst:-
A child who has symptoms suggestive of choledochal cyst usually undergoes the liver function tests in addition to routine work-up. The liver function tests may show raised levels of bilirubin and liver enzymes (AST, ALT, Alkaline Phosphatase, etc). It is usually the ultrasound (USG) of the abdomen that usually clinches the diagnosis. USG of abdomen remains the easiest and most non-invasive investigation for diagnosis despite an equally accurate diagnosis by CT scan of the abdomen. It is sometimes also possible to diagnose Choledochal cyst on antenatal USG (during later part of pregnancy). Outline of the anatomy and classification of the cyst is best achieved by cholangiography (radiologic visualization of the biliary tree). MRCP is the preferred modality for obtaining the cholangiogram as it is non-invasive and gives a good quality image. ERCP or PTC may be used when MRCP is not available, although the associated complications and risk of infection may sometimes outweigh the benefit obtained. The need of a cholangiogram is best decided on a case to case basis by an experienced clinician.
Complete surgical excision (removal) of the cyst remains the gold standard in the treatment of choledochal cysts. The drainage of remaining bile duct is re-established with a loop of jejunum (part of small intestine) fashioned as a Roux-n-Y. The part of bile duct used for the drainage procedure depends upon the type of cyst encountered. In cases where the intrahepatic tree is involved or intrahepatic stones have formed, resection of the involved part of liver may be required. Complete excision of the cyst removes the potential source of infection, calculus formation and the dreaded cholangiocarcinoma. When first seen with an associated complication, the patient may require emergency surgery (rupture of cyst producing peritonitis) or a liver transplant (associated advanced biliary cirrhosis) The surgery for choledochal cyst is technically difficult and is best performed at centres having adequate expertise and good outcome.