How to diagnose Hirschsprung's disease in a newborn or infant patient?

Diagnosing Hirschsprung's Disease in Newborns and Infants

Newborns with delayed passage of meconium beyond 24-48 hours, abdominal distension, and bilious vomiting should be evaluated for Hirschsprung's disease using a stepwise diagnostic algorithm starting with plain abdominal radiographs, followed by contrast enema, and confirmed with rectal biopsy. 1

Initial Clinical Evaluation

Key Historical Features That Identify Hirschsprung's Disease

• Delayed passage of meconium (present in 94.2% of cases) is the most critical historical feature, particularly when occurring beyond 24-48 hours of life 1, 2, 3
• Bilious vomiting (present in 75% of cases) strongly suggests distal bowel obstruction 2, 3
• Abdominal distension (present in 100% of cases) is a universal finding 2, 3
• Onset of symptoms in the first week of life occurs in 60% of Hirschsprung's patients versus only 15% with idiopathic constipation 2

Physical Examination Findings

• Abdominal distension with palpable bowel loops 4
• Empty rectal vault on digital rectal examination (though this is not always reliable) 5
• Explosive passage of stool and gas following rectal examination may occur 5

Associated Conditions to Screen For

• Trisomy 21 (Down syndrome) significantly increases likelihood of Hirschsprung's disease 6
• Congenital central hypoventilation syndrome (CCHS) requires screening for PHOX2B mutations, particularly PARM 20/26 and higher 1

Diagnostic Imaging Algorithm

Step 1: Plain Abdominal Radiographs (First-Line Study)

Plain abdominal radiographs should be obtained first to evaluate for bowel obstruction patterns 1, 7

Characteristic findings include:

• Numerous dilated bowel loops with air-fluid levels throughout the abdomen 7
• Absence or paucity of distal gas in the rectum and distal colon, indicating distal bowel obstruction 7
• Dilated proximal bowel with transition to collapsed distal bowel 7

Critical limitation: Plain radiographs cannot definitively diagnose Hirschsprung's disease and serve only as a screening tool to identify that obstruction exists, not to determine the specific etiology 7

Step 2: Contrast Enema (Diagnostic Imaging Procedure of Choice)

Following abnormal plain films, contrast enema should be performed as the diagnostic imaging procedure of choice 1, 7

Key diagnostic features:

• Transition zone between the narrow aganglionic distal segment and the dilated proximal colon (sensitivity approximately 80%) 1, 7
• Rectosigmoid ratio calculation can be performed to assess for abnormal caliber 3

Important limitations:

• 20% false-negative rate means contrast enema should be considered a screening tool only, not definitive for excluding Hirschsprung's disease 1
• Cannot exclude the diagnosis if clinical suspicion remains high despite negative enema 1

Step 3: Rectal Biopsy (Gold Standard for Confirmation)

Rectal biopsy remains the gold standard for definitive diagnosis of Hirschsprung's disease 1, 7, 8

Histopathological findings:

• Absence of ganglion cells in the colonic submucosa 8, 5
• Hypertrophic nerve trunks in the submucosa and muscularis propria 8, 5

Ancillary diagnostic tests:

• Acetylcholinesterase histochemistry shows increased acetylcholinesterase-positive nerve fibers 8
• Calretinin immunohistochemistry (absence of calretinin-positive ganglion cells) is extremely helpful in challenging cases 8

Technical considerations:

• Adequate biopsy depth must include submucosa to evaluate for ganglion cells 8, 6
• Pediatric surgeons are more likely to obtain adequate (OR 6.0) and positive biopsies (OR 6.7) compared to gastroenterologists 6

Clinical Decision Rule for Rectal Biopsy

All patients with Hirschsprung's disease have one or more of these features: 2

• Delayed passage of meconium
• Abdominal distension
• Vomiting
• Transition zone on contrast enema

Conversely, in children with constipation and NONE of these features, rectal biopsy is not necessary to exclude Hirschsprung's disease 2

Immediate Management During Diagnostic Workup

Patients with suspected Hirschsprung's disease require immediate supportive measures: 1

• NPO status (nothing by mouth) 1
• Intravenous fluid resuscitation to correct dehydration and electrolyte abnormalities 1
• Nasogastric tube decompression 1
• Immediate pediatric surgical consultation for any neonate with bilious vomiting 1

Critical Pitfalls to Avoid

• Do not rely on plain radiographs alone to exclude Hirschsprung's disease, as they cannot differentiate between causes of distal obstruction 7
• Do not accept a negative contrast enema as definitive if clinical suspicion remains high, given the 20% false-negative rate 1
• Do not delay rectal biopsy in patients with classic symptoms (delayed meconium, distension, vomiting) as this is the only definitive diagnostic test 1, 8
• Monitor closely for enterocolitis (occurs in up to one-third of patients), which is a significant cause of mortality and can occur before or after diagnosis 5
• Ensure adequate biopsy depth including submucosa, as superficial biopsies are inadequate for diagnosis 8, 6