What are the causes of partial obstruction of the duodenum in pediatric patients?

Causes of Partial Duodenal Obstruction in Pediatrics

Partial duodenal obstruction in pediatric patients is most commonly caused by duodenal stenosis, incomplete duodenal webs, annular pancreas, and malrotation with intermittent volvulus, with duodenal stenosis presenting more insidiously than complete atresia. 1, 2, 3

Intrinsic Causes

Duodenal Stenosis

• Duodenal stenosis results from incomplete failure of recanalization of the primitive gut lumen during embryologic development, creating a narrowed but patent lumen 2
• Presents with an indolent clinical course including poor weight gain, intermittent "spit-ups," and recurrent emesis rather than acute bilious vomiting 3
• May manifest with hypochloremic metabolic alkalosis due to chronic vomiting 3
• Diagnosis is challenging because symptoms are less dramatic than complete obstruction, requiring high clinical suspicion 3

Incomplete Duodenal Web

• Represents type I duodenal atresia with a mucosal web containing a small central perforation allowing partial passage of contents 2
• Can present beyond the immediate newborn period with feeding intolerance and failure to thrive 1, 4
• Diagnosed via upper GI series showing delayed gastric emptying and narrowing at the web site 3

Annular Pancreas

• Accounts for approximately 30-40% of duodenal obstruction cases and frequently causes partial rather than complete obstruction 5, 6
• The pancreatic tissue encircles the duodenum, creating variable degrees of luminal narrowing 6
• Commonly associated with duodenal atresia (33% of duodenal atresia cases have annular pancreas) 5

Extrinsic Causes

Malrotation with Intermittent Volvulus

• Malrotation can present with partial obstruction from Ladd bands compressing the duodenum or from intermittent midgut volvulus 1
• Associated with 28% of duodenal atresia cases and can occur at any age, though frequency decreases with time 5
• May present with a normal bowel gas pattern or nonclassic findings on radiographs, making diagnosis challenging 1
• Upper GI series is the reference standard, showing abnormal position of the duodenojejunal junction (ligament of Treitz), though false-negative rates of 3% and false-positive rates of 10-15% occur 1

Associated Conditions and Risk Factors

Prematurity and Polyhydramnios

• Duodenal obstruction is associated with prematurity in 46% of cases and maternal polyhydramnios in 33% 5
• Polyhydramnios detected antenatally should raise suspicion for duodenal pathology 4

Down Syndrome

• Present in 24% of duodenal atresia cases, making chromosomal evaluation important 5
• Down syndrome itself does not influence postoperative morbidity 6

Cardiac and Other Congenital Anomalies

• Cardiac anomalies are the major cause of long-term morbidity and mortality in duodenal obstruction patients 5, 7, 6
• 67.5% of duodenal obstruction cases have associated anomalies including cardiac, GI, and renal malformations 6

Diagnostic Approach

Initial Imaging

• Plain abdominal radiographs showing dilated stomach and proximal duodenum with variable distal gas suggest partial obstruction 1, 8
• The classic "double bubble" sign indicates duodenal-level obstruction but may be less pronounced in stenosis 8, 2

Definitive Diagnosis

• Upper GI series is essential for diagnosing partial obstruction, showing delayed passage of contrast through a narrowed segment 1, 3
• Ultrasound has limited utility for duodenal obstruction diagnosis compared to fluoroscopic studies 8

Clinical Pitfalls

• Partial obstruction may be masked by infrequent feeding or concentrated formula, delaying diagnosis 3
• Presentation can be atypical with chronic symptoms rather than acute bilious vomiting 3
• Late complications occur in 12% of patients, with 6% late mortality, necessitating long-term follow-up into adulthood 7
• Revision surgery is required in approximately 9-10% of cases for persistent symptoms 7