What is the technique for performing an open rectal biopsy in pediatric patients to rule out Hirschsprung's disease (HD)?

Open Rectal Biopsy Technique for Hirschsprung's Disease Diagnosis

Overview of Biopsy Approaches

Rectal suction biopsy (RSB) combined with acetylcholinesterase (AChE) staining is the current gold standard for diagnosing Hirschsprung's disease, with a sensitivity of 96.84% and specificity of 99.42%. 1 However, "open" rectal biopsy typically refers to full-thickness surgical biopsy, which is reserved for specific clinical scenarios when less invasive methods are inadequate or contraindicated.

When Full-Thickness (Open) Rectal Biopsy is Indicated

Full-thickness rectal biopsy is performed when:

• Suction biopsies are inadequate or non-diagnostic - This occurs in approximately 10% of cases where insufficient submucosal tissue is obtained 1
• Repeated suction biopsies fail to provide diagnosis - About 8.46% of patients require repeat biopsy 1
• Clinical suspicion remains high despite negative suction biopsy - Particularly in neonates with classic symptoms (delayed meconium passage, abdominal distension, vomiting) 2
• Patient age or anatomy precludes safe suction biopsy - Complications are significantly more frequent in newborns and infants (OR 9.00) 1

Surgical Technique for Full-Thickness Rectal Biopsy

Patient Positioning and Preparation

• Position the patient in lithotomy or prone jackknife position for optimal exposure 3
• Perform the procedure under general anesthesia in pediatric patients to ensure adequate muscle relaxation and prevent patient movement 3

Biopsy Site Selection

• Obtain tissue from the posterior rectal wall, 2-3 cm above the dentate line 4
• Avoid the anterior wall to minimize risk of injury to adjacent structures 3
• Stay at least 2 cm proximal to the dentate line to ensure adequate submucosal tissue with ganglion cells if present 1

Tissue Procurement

• Make a transverse or longitudinal incision through all layers of the rectal wall (mucosa, submucosa, and muscularis propria) 3
• Obtain a specimen measuring at least 3 mm in depth to ensure adequate submucosa for ganglion cell identification 1, 4
• Include muscularis propria in the specimen - This is the critical advantage over suction biopsy, as it definitively demonstrates the presence or absence of ganglion cells in the myenteric plexus 1

Closure and Hemostasis

• Close the defect in layers using absorbable sutures (typically 4-0 or 5-0 Vicryl) 3
• Achieve meticulous hemostasis before closure, as persistent rectal bleeding requiring transfusion occurs in 0.53% of cases 1
• Ensure watertight closure to prevent perforation (risk 0.06%) or pelvic sepsis (risk 0.06%) 1

Specimen Handling

• Orient the specimen immediately on a card or filter paper to prevent curling and ensure proper sectioning 1
• Submit for both hematoxylin and eosin (H&E) staining and acetylcholinesterase (AChE) staining 1
• Communicate with pathology that this is a full-thickness specimen for HD evaluation 3

Key Diagnostic Features to Identify

The pathologist will evaluate for:

• Absence of ganglion cells in the submucosal (Meissner's) and myenteric (Auerbach's) plexuses - This is diagnostic of HD 1
• Hypertrophied nerve trunks on AChE staining - Supportive evidence of HD 1
• Adequate submucosa and muscularis propria - Essential for definitive diagnosis 1

Clinical Context for Patient Selection

Pediatric surgeons are significantly more likely to obtain adequate (OR 6.0) and positive biopsies (OR 6.7) compared to gastroenterologists, largely because they biopsy younger patients with more classic HD symptoms 3.

Key clinical features that increase likelihood of positive biopsy include:

• Delayed passage of meconium beyond 48 hours (p<0.001) 3, 2
• Obstructive symptoms (abdominal distension, vomiting) (p<0.001) 3, 2
• Trisomy 21 (p<0.001) 3
• Full-term gestation (p=0.03) 3
• Male gender (p=0.02) 3
• Transition zone on contrast enema (p<0.05) 2

All patients with HD had one or more of these significant features, while only 64% of patients with idiopathic constipation had these features 2. The classic triad (delayed meconium, vomiting, abdominal distension) was present in 98% of HD patients versus 60% of constipated patients 2.

Complications and Risk Mitigation

The overall complication rate for rectal biopsy is 0.65%, with:

• Persistent rectal bleeding requiring transfusion: 0.53% 1
• Bowel perforation: 0.06% 1
• Pelvic sepsis: 0.06% 1

Complications are 9 times more frequent in newborns and infants compared to older children 1. Therefore, in neonates, consider delaying biopsy until after the first month of age when feasible, using serial rectal manometry for interim management 5.

Alternative: Endoscopic Mucosal Resection Technique

An emerging alternative to traditional open biopsy is endoscopic mucosal resection (EMR) using band ligation devices, which provides adequate samples (>3 mm with submucosa) in all cases studied 4. This technique:

• Is performed at 3 cm from the dentate line 4
• Can be done with or without submucosal lifting injection 4
• Provides adequate tissue for ganglion cell identification 4
• Is less invasive than full-thickness surgical biopsy 4

However, this technique is still under evaluation and may not replace full-thickness biopsy when EMR specimens are inadequate 4.