Teaching Case

A 13-year-old female presented with fever, abdominal distension and pain for two weeks. Her external abdominopelvic ultrasound was suggestive of loculated intraperitoneal collections, raising the possibility of tuberculosis. Therefore, an ascitic fluid tap was performed afterwards confirming the presence of Mycobacterium tuberculosis. She was referred to our centre for further management. Serum direct bilirubin was raised and a CT scan (CECT) was ordered to look for the cause of obstructive jaundice.

CT of the abdomen and pelvis with intravenous contrast administration revealed:

• Peripherally vascularised cystic lesion seen along the left infrahepatic space and at the porta hepatis communicating with the common hepatic duct with dilatation of the central intrahepatic biliary radicles.
• A small rent through its anterior wall communicating with the perihepatic ascites.
• Common bile duct was not seen separately from this lesion.
• Peritoneal ascites and smooth vascularised peritoneal thickening.

These findings raised the possibility of a ruptured choledochal cyst, which was confirmed on cholangiography- MR.

A subsequent ascitic tap demonstrated a bilious tap with high bilirubin content (more than the serum).

Background 

Choledochal cyst is a congenital anomaly characterised by dilatation of intra-, extrahepatic branches of biliary tree or both [1] [2]. The exact etiopathogenesis is still unknown; however, the widely accepted theory by Babbitt states that the anomalous pancreaticobiliary junction leads to reflux of pancreatic enzymes into the biliary system causing its dilatation secondary to increased intraluminal pressure [3]. Rupture of choledochal cyst resulting in biliary peritonitis is a rare complication, occurring, in fact, in less than 2% of the cases [4].

Clinical perspective 

This entity usually manifests in the first two decades of age with the classical triad of a palpable mass, abdominal pain, and jaundice, observed in less than 20% of the patients [5]. They may present due to complications such as ascending cholangitis. recurrent pancreatitis, progressive biliary cirrhosis, portal hypertension, stones in the cyst, and malignant transformation in the biliary tract [6]. Rupture of choledochal cyst should be suspected in children with acute abdomen, dilated biliary ducts and bilious ascites.

C. Imaging perspective

• Ultrasound is considered the screening modality which shows an anechoic lesion with posterior acoustic enhancement and possible communication with the biliary system.
• CT confirms a cyst with non-vascularised thin wall contiguous with a bile duct. It helps delineate the biliary tree anatomy, identify potential malignant wall thickening, and decide the surgical approach.
• MRCP is a non-invasive study useful for assessing the biliary and pancreatic ducts [1]. The defect in the cyst wall can be detected either on CT and MR.

Outcome 

Most patients with abdominal tuberculosis respond to standard-specific drugs [8]. The surgical option is reserved to subjects with acute complications[8]. After demonstration of a ruptured choledochal cyst, its excision and biliary reconstruction were planned. In uncomplicated choledochal cysts, the management depends on the type of the cyst according to the Todani classification[9]. In our case, the patient underwent an emergency excision of the choledochal cyst with hepaticojejunostomy which confirmed rupture of the cyst and peritonitis. The techniques of minimal dissection and good bowel washes are adopted in view of abdominal tuberculosis. In the postoperative period, enhanced recovery after surgery (ERAS) protocols are to be followed[11]. However, the child succumbed to multiorgan system failure.

Take home message/teaching points

In an epidemiological country like India, loculated ascites with peritonitis, keeps abdominal tuberculosis higher up in the differential diagnosis. However, in our case, the absence of necrotic lymphadenopathy, omental caking, bowel wall thickening, normal ileocecal junction and caecum led us to consider other causes. Demonstration of a cystic lesion at the porta hepatis, without delineation of a separate common bile duct, and a rent in its wall clinched the diagnosis of a rare complication (ruptured choledochal cyst).