A 15-year-old boy is brought to the emergency department due to abdominal pain that started approximately 24 hours ago and is described as diffuse, severe, and stabbing. The pain is associated with frequent bilious emesis, and he is unable to tolerate any oral intake. The patient's last bowel movement was over 24 hours ago, and he is passing minimal flatus. He has had nausea, anorexia, and intermittent abdominal pain for the last 6 months. The patient has never required surgery. His family emigrated from Indonesia 4 weeks ago. Temperature is 37.6 C (99.7 F), blood pressure is 112/78 mm Hg, pulse is 110/min, and respirations are 12/min. Mucous membranes are pale and dry. Heart and lung sounds are unremarkable aside from tachycardia. The abdomen is diffusely tender and distended without rebound or involuntary guarding. Bowel sounds are high-pitched and loud. Laboratory results are as follows:
| Complete blood count | |
| Hemoglobin | 10.5 g/dL |
| Platelets | 455,000/mm3 |
| Leukocytes | 13,800/mm3 |
| Neutrophils | 60% |
| Lymphocytes | 20% |
| Eosinophils | 15% |
| Serum chemistry | |
| Sodium | 142 mEq/L |
| Potassium | 3.3 mEq/L |
| Creatinine | 1.2 mg/dL |
An abdominal x-ray shows small bowel dilation and air-fluid levels without pneumobilia. Which of the following is the most likely etiology of this patient's presentation?
This patient with abdominal pain and distension, high-pitched bowel sounds, obstipation, and imaging demonstrating small bowel dilation with air-fluid levels has a small bowel obstruction (SBO). In a patient with peripheral eosinophilia and recent emigration from an endemic region (eg, Asia, Africa, South America), this presentation is concerning for ascariasis. Ascaris lumbricoides is a parasitic roundworm spread via fecal-oral transmission. Ingested eggs hatch in the colon, and larvae penetrate the colonic wall to spread hematogenously to the lungs, where they are coughed up, swallowed, and mature into egg-laying adult worms in the small intestine.
Most patients are asymptomatic, with symptoms generally occurring only in those with a high worm burden. Pulmonary manifestations (eg, cough, eosinophilic pneumonitis) are rare but can occur within the first few weeks of an infection. Intestinal manifestations, which are more common, occur 1-2 months later and are usually nonspecific (eg, abdominal pain, nausea/vomiting, anorexia, diarrhea). However, adult worms can obstruct the lumen of the small bowel or hepatobiliary tree, resulting in SBO, biliary colic, cholangitis, or acute pancreatitis. Laboratory findings include peripheral eosinophilia (often the first sign of ascariasis) and signs of malnutrition (eg, vitamin deficiency, anemia).
The diagnosis is confirmed with visualization of Ascaris eggs or macroscopic worms in the stool or respiratory secretions. Management of an ascariasis SBO is usually conservative and includes nasogastric suction and fluid/electrolyte repletion, followed by definitive treatment with albendazole or mebendazole.
(Choice B) Gallstone ileus results from gallstone passage through a biliary-enteric fistula, leading to a mechanical SBO. However, pneumobilia is usually visualized on plain radiography and eosinophilia is unexpected. In addition, it occurs more commonly in elderly patients.
(Choice C) Peritoneal adhesions can cause SBO; however, they would be unexpected in a patient without prior intraabdominal surgeries. Eosinophilia would not occur.
(Choice D) Small bowel lymphoma can cause abdominal pain, malabsorption, and SBO. However, it is very rare and usually associated with unintentional weight loss. Peripheral eosinophilia is unexpected.
(Choice E) Ulcerative colitis can cause abdominal pain and malnutrition but usually also causes hematochezia. Unlike Crohn disease, ulcerative colitis does not involve the small bowel and would not cause SBO.
Educational objective:
Ascariasis typically affects patients with recent travel from endemic regions (eg, Asia, Africa, South America). It is often asymptomatic but may cause pulmonary (eg, cough, eosinophilic pneumonitis) or intestinal (eg, abdominal pain, nausea/vomiting, malnutrition) manifestations. Complications include obstruction of the small bowel or hepatobiliary tree (eg, cholangitis, pancreatitis). Treatment includes albendazole or mebendazole.