Pancreatitis Due to Ascaris lumbricoides: Second Occurrence After 2 Years

South Med J. 2001;94(1) 

In This Article

Discussion

It is estimated that 25% of the world's population is infected with A lumbricoides, making this the most common helminthic infection worldwide.[1]Ascaris infection begins with ingested foods contaminated with fertilized eggs. The eggs hatch in the duodenum, releasing the larval stage of the parasite. The larvae penetrate the small bowel mucosa and enter the venous circulation. After reaching the lungs via the bloodstream, the larvae break into the alveoli and ascend the bronchial tree. From the oropharynx, the larvae are swallowed and mature into adult worms in the gastrointestinal tract.[1] This cycle takes about 2 months.

Most infections are asymptomatic but can produce a wide spectrum of symptoms including malaise, fever, headaches, nausea, diarrhea, dyspnea, pneumonitis, and pneumonia.[1] In patients with a heavy worm load, the adult worms can cause abdominal pain, small bowel obstruction, biliary colic, gallstone formation, cholecystitis, pyogenic cholangitis, liver abscess, and pancreatitis.[1,2] Khuroo et al[2] reported 500 cases in India of hepatobiliary and pancreatic disease due to A lumbricoides. Of those patients, 56% had biliary colic, 24% had acute cholangitis, 13% had cholecystitis, 6% had acute pancreatitis, and 1% had hepatic abscess. Sandouk et al[3] reported 300 cases of pancreatic-biliary ascariasis in Syria and noted that 16% had acute cholangitis, 4% had acute pancreatitis, and 1% had obstructive jaundice. Additionally, they reported that 80% of the patients had a history of either cholecystectomy or endoscopic sphincterotomy. Ascaris causes pancreatitis due to obstruction of papilla of Vater, invasion of common bile duct, or invasion of pancreatic duct and can occur with abdominal pain, back pain, emesis, fever, or jaundice.[4] Although Ascaris-induced pancreatitis is predominantly diagnosed in tropical countries, it has been seen in western countries, as well.[5,6]

The diagnosis of Ascaris pancreatitis requires a high degree of suspicion. The worms move freely in and out of the biliary tree and therefore can be easily missed.[3] Furthermore, stool studies lack sensitivity and specificity. The diagnosis can be attempted with ultrasonography, computed tomography (CT), or ERCP. Ultrasonography is a simple, noninvasive test that reveals long, linear, echogenic strips that may show acoustic shadowing. This has a sensitivity of 50% to 86% for worms in the biliary tree, but the sensitivity for detecting worms in the pancreatic duct is not known.[4,7,8] Additionally, ultrasonography cannot diagnose ascariasis in the duodenum. A CT scan can also be useful but has a lower sensitivity than ultrasonography.[3,9]

Use of ERCP allows better identification of worms in the duodenum and in the pancreatic-biliary tree, while providing a safe, therapeutic option of removing the worms.[2,7] Sandouk et al[3] noted that ERCP accurately made a definitive diagnosis by showing a smooth filling defect in the common bile duct, a worm protruding from the ampullary orifice, or evidence of damage to the ampulla in 93% of patients who had clinical or ultrasonographic findings of this infection. Worm extraction from the ampullary orifice, biliary duct, or pancreatic duct was successful in 98% of patients, with only 13% requiring a sphincterotomy to achieve these results.[3] Most worms were extracted by flushing the bile ducts or by use of grasping forceps or balloon catheters. Thus, ERCP has now become the investigation modality of choice.

Anthelmintic therapy with mebendazole or albendazole is effective in eradicating ascariasis in 84% to 100% of cases.[8] These agents inhibit phosphorylation in the mitochondria, causing a depletion of the worm's glucose. Pyrantel pamoate is a neuromuscular blocking agent that causes paralysis of the worms. The worms are then expelled by normal gastrointestinal peristalsis. Despite these excellent results, patients can have a reinvasion of this organism from either reinfection or ineffective therapy, with a reported incidence of 15% to 28% at 1 year.[2,4] Our patient most likely became reinfected while visiting the Philippines. This theory is plausible, since it takes approximately 2 months for the development of an adult worm after egg ingestion.

The differential diagnosis of pancreatitis includes gallstone disease, alcohol abuse, drugs, toxins, infections, metabolic abnormalities, and vascular abnormalities, but it should be expanded to include ascariasis in patients with recent travel to underdeveloped countries or immigrants from endemic areas. The prognosis of Ascaris-induced pancreatitis is excellent if the patient is diagnosed and treated early. The mortality rate is 3% in endemic areas, but this can be higher if physicians in Western countries do not consider this as part of their differential diagnosis.[8] If ascariasis is suspected, ERCP can be used as a diagnostic as well as a therapeutic modality for this entity.

The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States Government.

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