it consists of cystic dilatation of the extrahepatic biliary tree , intrahepatic biliary radicles or both .
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 . 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 .
a 47-day - old female infant with jaundice from leh , india , was referred for a tc-99 m 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% ) .
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-99
m 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 ] .
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 ) .
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 .
initial composit dynamic images showing adequtae tracer uptake by liver at 05 min and filling up of the choledochal cyst by radiotracer 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
incidence of the choledochal cyst is very low ( 1/100,000150,000 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 .
biliary peritonitis secondary to cyst perforation or rupture is a rare complication reported to occur in 12% cases of choledochal cyst , compared to other complications like cholangitis , cirrhosis , portal hypertension , hepaticocholedochal lithiasis , liver abscess , etc .
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 .
usg / computed tomography ( ct ) scan is used to demonstrate choledochal cyst , and tc-99 m 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 . 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 .
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 ,
m hida scan is used to increase the accuracy of the diagnosis and can provide additional vital information influencing the management .
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 .
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 ,
tc-99 m hida scan is used to increase the accuracy of the diagnosis and can provide additional vital information influencing the management .
 a 47-day - old female infant presented with congenital inguinal hernia , seizure on the 2nd 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-99 m 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 12% cases of choledochal cyst . 
 early diagnosis and management is the key to reduce the morbidity and mortality . 
INTRODUCTION
CASE REPORT
DISCUSSION
Tc-99m HIDA scan