Ascaris-induced pancreatitis

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Ascaris-induced pancreatitis is the most common form of parasite-induced pancreatitis.

Epidemiology

Ascariasis in parts of India is the second most common form of pancreatitis after gallstones . It is rare outside of endemic regions however.

Clinical presentation

The presentation will be similar to other forms of acute pancreatitis. Other signs and symptoms of ascariasis may also be present.

Pathology

Ascariasis is due to infection by the human roundworm, Ascaris lumbricoides. Single or multiple worms may be involved. Invasion and subsequent blockage of the distal biliary tree, and less commonly the pancreatic duct, by the helminth causes obstruction to pancreatic enzyme outflow and pancreatic injury .

Radiographic features

Ultrasound

Ultrasound is sensitive and specific for detecting the presence of worms in the biliary tree .

  • linear echogenic strips without acoustic shadowing in the pancreatic or biliary ducts (known as the "strip sign") 
  • an anechoic tube within the worm may be seen which represents its gastrointestinal tract (known as the "inner tube sign")
  • if multiple worms are present a spaghetti like appearance may be visible
ERCP
  • smooth linear filling defects within the bile ducts
MRI
  • T2: linear filling defect with associated pancreatic duct dilation

Treatment and prognosis

Intravenous fluids, analgesia and bowel rest is recommended in the acute treatment followed by antihelminth treatment . Endoscopic extraction of the worms, or surgery if this fails, can also be used. Dead or fragmented worms can potentially serve as a nidus for future stone formation or could contribute to recurrent pancreatitis so removal is important .