Biliary ascariasis causing cholelithiasis in a child

Clinical History

A four-year old local male Filipino presented to our institution with recurrent abdominal pain and constipation, without vomiting. Family history was unremarkable. Physical examination demonstrated jaundiced skin and icteric sclerae but no significant abdominal findings. Total and direct bilirubin levels were elevated.

Imaging Findings

An abdominal radiograph revealed a radiopaque density to the right of T11-T12. An abdominal ultrasound showed slight dilatation of the right intrahepatic ducts. The common bile duct was also dilated measuring 0.8 cm. There was a non-mobile echogenic focus without posterior acoustic shadowing seen within the gallbladder, with associated thickening of the gallbladder wall measuring 0.42 cm. No high-level echo or shadowing focus was noted. Some parts of the biliary tree were not visualized due to overlying intestinal gas. Findings were suggestive of cholecystitis with the echogenic focus probably representing ascaris remnant versus tumefactive bile. The patient underwent open cholecystectomy with intra-operative cholangiogram wherein mucinous materials were collected within the gallbladder, which may represent ascaris carcass. A black-pigmented stone was also found in the distal common bile duct. Histopathologic findings were consistent with chronic cholecystitis with cholelithiasis.

Discussion

Gallstones in children are predominantly of the pigment type, usually found in those with haematologic disorders and in those with a history of prolonged parenteral nutrition. [1, 2] They are formed due to supersaturation of bile with calcium bilirubinate. [3] Patients typically present with jaundice and right upper quadrant pain. [1] Several factors account for gallbladder stone formation. Biliary ascariasis is an uncommon but possible cause for gallstones. Ascaris lumbricoides is a giant roundworm prevalent in tropical countries such as the Philippines. It enters the human body as an infective egg that hatches into larvae within the small intestines. [4] Being a visceral larval migrant, it can enter the common bile duct and remain in that area producing cholangitis, strictures, calculi, cholecystitis, pancreatitis, and liver abscesses. [5-7] Almost all ascaris worms in the biliary system will return into the intestine, but those that remain will cause obstruction. Irritation caused by the worm or its excretions result in biliary colic and sphincter of Oddi spasm with partial biliary obstruction. [8] This can lead to an intense inflammatory response resulting in duct necrosis, calcification, stenosis, fibrosis and cholangitis. [8] Dead worms may disintegrate and become a nidus for calculus formation. [9]

Ultrasound is a reliable and cost-effective modality for the screening of biliary ascariasis. The worms may appear as linear or curly echogenic structures in the biliary tracts, which may have characteristic movements if they are still alive. [6] Other characteristic sonographic features include a long, linear, parallel echogenic strip, usually without acoustic shadowing, a bull’s eye or spaghetti appearance, or an impacted-worm sign. [4] There can also be gallbladder distension, oedema of the gallbladder wall and the presence of sludge. [10] Stones that are found within the ducts are more consistent with those due to biliary ascariasis than with other aetiologies such as chronic haematologic, haemolytic and metabolic disorders. [11] Total bilirubin levels higher than 1.3 mg/dL, a dilated common bile duct (>6 mm), and gallbladder wall thickening (>3 mm) on ultrasound are also noted findings. [10]

More than 95% respond to conservative management as worms return spontaneously into the intestine. [9] Anti-helminthic agents, which are routinely given to toddlers in the Philippines, are effective as prophylactic against infestation and enhance return of worms into the gut. [5] Complications are managed surgically or by ERCP.

Biliary ascariasis producing gallstone is an uncommon occurrence especially in children. However, this should be considered in endemic regions and in patients without other probable causes of biliary stones.

Differential Diagnosis List

Final Diagnosis

Chronic cholecystitis with choledocholithiasis likely secondary to biliary ascariasis

URL:	https://www.eurorad.org/case/13915
DOI:	10.1594/EURORAD/CASE.13915
ISSN:	1563-4086