Choledochal Cyst

Dilated
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Diagnosis and reasoning

The acute abdomen is one of the most common presentations in clinical practice, with a spectrum of causative etiologies ranging from self-limited disease to life-threatening conditions. The location of the abdominal pain is key towards guiding the diagnostic reasoning in this situation; note that pain in the right upper quadrant is usually due to pulmonary, renal, hepatobiliary, or pancreatic disease. In this particular patient, the presence of a 3-year history of pain in the same location provides an important clue; when considered along with the current presentation, this brings up four main possibilities: recurrent biliary colic, recurrent acute cholecystitis, acute recurrent pancreatitis, or nephrolithiasis. Unfortunately, the examination is not particularly helpful; while the mild right-upper quadrant tenderness might be due to gallbladder disease, this is too non-specific a finding. Liver chemistries are an essential component of her workup; here, the elevated liver enzymes suggest either hepatobiliary disease or pancreatic disease. Note that biliary colic usually does not cause derangement of liver functions. A pancreatic enzyme assay is also important; this shows marked elevations of both serum amylase and lipase - could this be acute pancreatitis ? Unfortunately, no single laboratory test or clinical sign is pathognomonic for acute pancreatitis; the presentation of this patient is not classical enough to unambiguously establish this diagnosis. Imaging of the abdomen should probably be the next step, aiming to detect signs of pancreatic inflammation; ultrasonography has an acceptable sensitivity in this regard; note also that it is the recommended initial imaging modality in patients with right upper quadrant pain. Not only does this demonstrate the presence of focal pancreatic inflammation, confirming that acute pancreatitis is indeed present, but it also reveals a surprising finding: a cystic structure near the distal common bile duct and the head of the pancreas. Could this be a choledochal cyst? Diagnosing the presence of a choledocal cyst requires demonstration of continuity of the cyst with the biliary tree; this characteristic differentiates it from other intra abdominal cysts such as pancreatic pseudocysts, echinococcal cysts or biliary cystadenomas. MRCP is the imaging study of choice in this scenario; the resultant findings confirm the presence of a type 1 choledocal cyst. Her immediate treatment should involve management of the acute pancreatitis, of which appropriate analgesia is a key element; she should also be kept nil by mouth in order to rest the pancreas. Considering definitive management of the choledochal cyst (which is best performed once the acute episode of pancreatitis has resolved), total excision of the cyst combined with cholecystectomy is the treatment of choice, followed by reconstruction of the biliary tract using a Roux-en-Y hepaticojejunostomy.


Discussion

Choledocal cysts are congenital dialatations of the intra- and/or -extrahepatic biliary tree. They are rare, with an estimated incidence ranging from 1 in 100,000 to 1 in 150,000 persons in North America; the condition is more prevalent in Asia than in the west, and in women more than in men. Most patients with choledochal cysts are diagnosed during infancy or childhood, with 60% of cases identified before the age of 10 years. However, note that the condition may be discovered at any age. The pathogenesis of choledocal cysts is unclear; they are classified into 5 types according to the system introduced by Todani and colleagues. These are as follows: Type I - dilatation of the extrahepatic bile duct Type II - true diverticulum from the extrahepatic bile duct Type III - dilatation of the extra-hepatic bile duct within the duodenal wall (choledochocoele) Type IV - cysts involving either the intra and/or extrahepatic ducts Note that type I cysts are the commonest form, accounting for 75% of cases. Choledochal cysts are often asymptomatic, and only discovered incidentally, following investigation for other disease. While the 'classical' presentation consists of jaundice, upper abdominal pain and a palpable abdominal mass, this is rare; in adults, the most common presenting symptom is acute abdominal pain, followed by jaundice and cholangitis. Patients may also present due to the complications of choledochal cysts; of these the two most common are stone formation and malignancy. Other important complications include recurrent pancreatitis, liver abscesses, and portal hypertension. Between 1% to 12% of patients present with spontaneous cyst rupture, resulting in sepsis and biliary peritonitis. Ultrasonography may confirm the presence of an abnormal cyst in the biliary tree, while computerized tomography (CT) may additionally reveal the extent of the intra- or extrahepatic dilatation. However, note that magnetic resonance cholangiopancreatography (MRCP) is the gold standard diagnostic test in these patients; it will clearly demarcate the relevant anatomy, including the relationship between the bile duct and pancreatic duct. Because of the increased risk of development of cholangiocarcinoma, complete excision of the cyst combined with cholecystectomy is the treatment of choice, ideally followed by a Roux-en-Y biliary diversion. The prognosis of these patients following excision of the cyst is usually excellent.


Take home messages

  1. Both liver chemistries and ultrasonography are key to the workup of patients with acute right upper quadrant pain.
  2. MRCP is the gold standard investigation for detection of choledocal cysts.
  3. Important complications of choledochal cysts include stone formation, malignancy, recurrent pancreatitis, liver abscesses, and portal hypertension.

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