Microbiology · Year 2 · from Microbiology
Case 2: Ascariasis with Intestinal Obstruction
Presentation
A 6-year-old boy from rural Guatemala presents with severe colicky abdominal pain, bilious vomiting, and abdominal distension for 24 hours. He has had no bowel movement or passage of flatus. His mother reports that he had a cough 2-3 weeks ago that resolved spontaneously. On examination, temperature is 37.8°C, the abdomen is distended and tympanitic with high-pitched bowel sounds and diffuse tenderness. Abdominal radiograph shows dilated loops of small bowel with air-fluid levels and an unusual "whirlpool" pattern of soft tissue density in the right lower quadrant.
Clinical Image
Surgical specimen showing a bolus of Ascaris lumbricoides worms causing intestinal obstruction - a serious complication of heavy worm burden in children.
Image Source: Lecture image - Ascaris complications
Questions
- What is the diagnosis, and what caused the earlier respiratory symptoms?
- Explain the life cycle of this parasite and how it relates to the clinical presentation.
- What is the mechanism of intestinal obstruction?
- What is the management of this condition?
Answers
- Diagnosis and respiratory symptoms: This is intestinal obstruction caused by Ascaris lumbricoides (roundworm) infection. The earlier cough represents Loeffler syndrome - transient pulmonary infiltrates and eosinophilia occurring when migrating larvae pass through the lungs. This phase occurs 1-2 weeks after egg ingestion, before adult worms mature in the intestine.
- Life cycle and clinical correlation:
- Egg ingestion: Fertilized eggs in contaminated soil/food hatch in small intestine
- Larval migration: Larvae penetrate intestinal wall, enter bloodstream, travel to liver, then lungs (causing Loeffler syndrome at 1-2 weeks)
- Pulmonary phase: Larvae ascend airways, are swallowed, return to intestine
- Adult worms: Mature in small intestine over 2-3 months; can live 1-2 years, reaching 15-35 cm length
- Egg production: Female worms produce 200,000 eggs/day, passed in stool
The timeline fits: ingestion → pulmonary symptoms at 2-3 weeks → intestinal symptoms as worm burden increases.
- Mechanism of obstruction: Ascaris causes mechanical intestinal obstruction through:
- Worm bolus: Mass of entangled adult worms (can be dozens to hundreds) physically blocks intestinal lumen
- Most common in children: Narrower intestinal diameter relative to worm size, and often heavier worm burdens
- Can also cause biliary obstruction (worms migrate into biliary tree), appendicitis (worms in appendix), and intestinal perforation
- The "whirlpool" sign on imaging represents the tangled worm mass
- Management:
- Partial obstruction (most cases): Conservative management
- NPO, IV fluids, nasogastric decompression
- Anthelmintic therapy once obstruction resolving: Albendazole or mebendazole
- Avoid anthelmintics during complete obstruction (paralyzed worms may worsen blockage)
- Complete obstruction or complications (perforation, volvulus):
- Surgical intervention: Manual extraction of worm bolus, bowel resection if necrotic
- Supportive care: Monitor for worm passage in stool after treatment
- Prevention: Improved sanitation, periodic mass deworming programs in endemic areas