Spontaneously ruptured choledochal cyst: Rare diagnosis on hepatic scintigraphy.

A 47-day-old female infant presented with congenital inguinal hernia, seizure on the 2(nd) day of life, fever, progressive jaundice, acholic stools and distension of abdomen. She was suspected to have choledochal cyst with extrahepatic biliary atresia (EHBA) and referred for an Hepatobiliary Tc-99m iminodiacetic acid (HIDA) scan. On HIDA scan, a functional diagnosis of ruptured choledochal cyst was made which was not possible on anatomical imaging like ultrasound (USG)/computed tomography (CT) scan. This was supported thereafter by bilious aspirate on abdominal paracentesis. Immediate laparotomy with T-tube insertion was done. The child improved dramatically after the procedure. Biliary peritonitis secondary to cyst perforation or rupture is a rare complication reported to occur in 1-2% cases of choledochal cyst. Early diagnosis and management is the key to reduce the morbidity and mortality.

INTRODUCTION

Choledochal cyst is a rare congenital anomaly of the bile ducts. It consists of cystic dilatation of the extrahepatic biliary tree, intrahepatic biliary radicles or both. Initial mention of choledochal cysts was made in 1723 by Vater and Ezler. Alonso-Lej et al. and later Todani classified choledochal cysts into five subtypes. The pathogenesis is multifactorial. Some aspects are consistent with congenital etiology and others with congenital predisposition to acquire the disease under conditions like anomalous pancreatobiliary junction with subsequent reflux cause.[1] In support of congenital cause, defects in epithelization, recanalization of the developing bile ducts during organogenesis and congenital weakness of the duct wall are implicated. The clinical presentation changes with age. Overt, dramatic signs and symptoms are more common in infancy. Jaundice, mass and pain abdomen are the classical findings, especially in infancy.

CASE REPORT

A 47-day-old female infant with jaundice from Leh, India, was referred for a Tc-99m HIDA scan to rule out extrahepatic biliary atresia (EHBA). There was no history of direct or indirect trauma. On day 2 of life, the child developed fever and had a seizure. Over the next few days, she started having jaundice, distension of the abdomen, acholic stools and was found to be anemic. The child was treated as a case of ABO incompatibility with phototherapy in view of mother's blood group “O” and baby's “B.” Subsequent laboratory examination revealed conjugated hyperbilirubinemia (total 6.8 mg%, conjugated 5.4 mg%). Other hepatic and renal biochemical functions were mildly deranged. Serology for HBsAg and HIV was negative. First ultrasound (USG) on 12.08.10 revealed? portal venous thrombosis with cirrhosis, ascites and mass in relation to segment VI of the liver. Repeat USG on 03.09.10 showed cystic lesion in the region of porta hepatis with diagnosis of choledochal cyst and differential diagnosis of enteric duplication cyst. The child was treated with antibiotics and therapeutic ascitic fluid tap due to respiratory distress. Tc-99m HIDA scan was ordered to rule out EHBA, which showed adequate tracer uptake by the liver in 5 min. A photopenic area appeared at porta hepatis which subsequently Accumulated and held the activity [Figure 1]. Delayed imaging at 2 h showed slowly rising activity in the ascitic fluid [Figure 2]. This was indicative of choledochal cyst with leak into the peritoneal cavity. Immediate laparotomy was done and the leak was identified in a fusiform dilatation of the extrahepatic biliary duct with gall bladder opening into it (Type I). T-tube was placed into the perforation. The child recovered from the sepsis with biliary diversion and antibiotics, and was planned for definitive surgery. Choledochal cyst rupture is managed with major excision–reconstruction procedure unlike spontaneous perforation of the extrahepatic bile duct which is managed by temporary tube cholecystectomy or subhepatic drainage till subsidence of the biliary leak.[2]

Figure 1

Initial composit dynamic images showing adequtae tracer uptake by liver at 05 min and filling up of the choledochal cyst by radiotracer

Figure 2

Delayed images at 01hr and 02hrs showing the persistent radiotracer activity in the choledochal cyst and increasing activity in the ascitic fluid. Another adjacent focus of increased radiotracer activity is intrahepatic ductal pooling

DISCUSSION

Incidence of the choledochal cyst is very low (1/100,000–150,000 live births), but now with the improved diagnostic techniques it is diagnosed more frequently. About 80% of the cysts become symptomatic early and are diagnosed before the age of 10 years. Cysts are more common in Japanese[1] and three times more common in women. Biliary peritonitis secondary to cyst perforation or rupture is a rare complication reported to occur in 1–2%[3] cases of choledochal cyst, compared to other complications like cholangitis, cirrhosis, portal hypertension, hepaticocholedochal lithiasis, liver abscess, etc.[4] It is important to differentiate a spontaneous perforation of choledochal cyst from spontaneous perforation of the extrahepatic bile duct – a classic entity which is more common and occurring exclusively in infants below 20 weeks of age. Choledochal cysts must be differentiated from cysts in other nearby organs, including cystic lesions of the kidney (renal cyst, hydronephrosis and Wilm's tumor), pancreas (pseudocyst), or duodenum (diverticulum), etc. The malignant potential of a choledochal cyst is about 2.4%.[5] USG/computed tomography (CT) scan is used to demonstrate choledochal cyst, and Tc-99m HIDA and Magnetic resonance cholangiopancreatography (MRCP) for increasing the accuracy. Percutaneous transhepatic cholangiography (PTC), endoscopic retrograde cholangiopancreatography, oral and IV cholecystography are the other diagnostic tests.

Tc-99m HIDA scan

Once a cyst is identified with one of the imaging modalities, cholescintigraphy confirms the diagnosis. Usually there is no need for pre-treatment with phenobarbitone, unless the child is severely jaundiced. Routinely, 1 min per frame images are obtained for 60 min. Delayed images are obtained at 4 and 24 h when necessary. Delayed filling of abnormal biliary tree with activity persisting in the cyst on delayed images is diagnostic of a choledochal cyst. Postoperative scan can also be used to check the patency of the anastomosis or to detect any leak.

In conclusion, choledochal cysts have no classical symptoms and USG is the initial screening tool. Tc-99m HIDA scan is used to increase the accuracy of the diagnosis and can provide additional vital information influencing the management. It is also useful in postoperative follow-up.