Duodenum Inversum in a Pediatric Patient: A Rare Anatomical Variant Complicating Functional Abdominal Pain

Duodenum inversum is a rare congenital anomaly characterized by the retrograde and superior course of the third portion of the duodenum before midline crossing. Although predominantly incidental in adults, pediatric cases have been reported and can complicate the evaluation of gastrointestinal symptoms.

A 6-year-old male with attention deficit hyperactivity disorder, treated with dextroamphetamine–amphetamine and clonidine, presented with five days of nausea, vomiting, and abdominal pain.1 He had a history of intermittent constipation, with no bowel movement for five days prior. On examination, he demonstrated mild epigastric tenderness without guarding or rebound. Vital signs were notable for blood pressure above the 95th percentile. Laboratory evaluation was within normal limits, including electrolytes and liver function tests.

Initial imaging aimed to evaluate superior mesenteric artery (SMA) syndrome due to epigastric pain exacerbated in supine and upright positions and recent weight loss of 6.6 kg. Abdominal radiography revealed moderate stool burden but no obstruction or pneumatosis. Upper gastrointestinal fluoroscopy demonstrated redundancy and a retrograde course of the third portion of the duodenum, consistent with duodenum inversum, while ruling out SMA syndrome.

Management focused on conservative measures. The patient underwent polyethylene glycol (PEG) bowel clean-out and rehydration, resulting in symptom resolution, improved dietary tolerance, and regular bowel movements. Pediatric gastroenterology and surgery consultations confirmed that surgical intervention was unnecessary due to the absence of obstruction or acute abdomen. Discharge included PEG as needed, cyproheptadine for functional abdominal pain, and dietary modifications. Outpatient follow-up showed persistent mild abdominal pain but progressive improvement with continued therapy. Esophagogastroduodenoscopy performed during follow-up demonstrated normal anatomy and only mild inactive gastritis. At the five-month follow-up, the patient exhibited symptom resolution and weight gain.

This case highlights the importance of recognizing duodenum inversum in pediatric patients presenting with nonspecific gastrointestinal complaints. While often benign and incidentally detected, the anomaly may complicate the evaluation of functional abdominal pain, gastroesophageal reflux, or constipation. Conservative management is appropriate in the absence of obstruction, with surgical intervention reserved for complications such as obstruction, duodenitis, or peptic ulcer disease. Awareness of this rare anomaly facilitates accurate diagnosis, prevents unnecessary interventions, and guides appropriate long-term management.

Reference:

1. Ahmadian R, Cardero DR, Montaño KN. A Rare Case of Duodenum Inversum in a Pediatric Patient. Case Reports in Pediatrics. 2025;2025(1):9994811. 

Link: https://onlinelibrary.wiley.com/doi/10.1155/crpe/9994811