Penyakit Hirschsprung

01Pathophysiology

Hirschsprung disease is a congenital motility disorder caused by the failure of neural crest cells to complete their craniocaudal migration along the developing gut during weeks 5 through 12 of gestation. This arrested migration results in the complete absence of ganglion cells in both the myenteric (Auerbach) plexus and the submucosal (Meissner) plexus of the affected bowel segment. Without these ganglion cells, the involved segment cannot undergo coordinated peristaltic relaxation.
The aganglionic segment remains in a state of tonic contraction, creating a functional obstruction. Stool and gas cannot pass through this narrowed, contracted distal segment, which causes the proximal normally innervated bowel to dilate progressively. This is why the disease is paradoxically named: the problem is in the narrow segment, but the "megacolon" develops proximally as a compensatory dilation.
The length of the aganglionic segment determines the clinical severity. In roughly 80% of cases, the disease is limited to the rectosigmoid region (short-segment disease). In about 15 to 20%, it extends proximal to the sigmoid (long-segment disease). In rare cases, total colonic aganglionosis occurs. The disease always involves the internal anal sphincter and extends proximally in a continuous fashion; skip lesions do not occur.
The reason these patients fail to pass meconium in the first 48 hours is directly tied to the pathophysiology: the aganglionic rectum cannot relax to allow evacuation. This single clinical feature, delayed meconium passage in an otherwise full-term infant, is the classic vignette trigger for this diagnosis.

02Classification and Clinical Manifestation

03Diagnostic Workup

The workup begins when a neonate fails to pass meconium within 48 hours of birth, or when an infant presents with refractory constipation and abdominal distension. The best initial test is an unprepared contrast (barium) enema. It is critical that no rectal preparation (enemas, digital stimulation) be performed beforehand, as this can decompress the bowel and obscure the transition zone. The classic finding on barium enema is a narrow distal segment transitioning to a dilated proximal segment. A 24-hour delayed film showing retained barium further supports the diagnosis. In neonates younger than 2 to 4 weeks, the transition zone may not yet be apparent on contrast enema, making interpretation less reliable in this age group.
Despite the utility of barium enema, the gold standard for diagnosis is rectal suction biopsy. This is a bedside procedure that does not require general anesthesia. The biopsy must be obtained at least 2 cm above the dentate line, because the normal distal rectum is physiologically hypoganglionated and sampling too low can produce a false-positive result. Histology reveals the absence of ganglion cells in the submucosal plexus and the presence of hypertrophied nerve fiber bundles that stain positive for acetylcholinesterase. If the suction biopsy is inconclusive, a full-thickness rectal biopsy under anesthesia may be needed to evaluate the myenteric plexus.
Anorectal manometry is used primarily as a screening tool, particularly in older children with chronic constipation. The test evaluates the rectoanal inhibitory reflex (RAIR): in normal individuals, rectal distension causes the internal anal sphincter to relax. In Hirschsprung disease, this reflex is absent. A normal RAIR effectively excludes the diagnosis. However, a positive (abnormal) manometry result must still be confirmed with biopsy.

04Management and Treatment

Acute stabilization is the priority in any neonate presenting with bowel obstruction. The child is placed NPO, nasogastric decompression is initiated, and IV fluids are started. Serial rectal irrigations with warm normal saline (10 to 20 mL/kg per session) are performed to decompress the dilated proximal bowel and evacuate retained stool. These irrigations are both therapeutic and diagnostic: if rectal washouts produce dramatic decompression and relief of symptoms, this strongly supports the diagnosis.
Once the diagnosis is confirmed, the decision between immediate definitive surgery and a staged approach depends on the clinical status. In a stable, well-nourished infant with short-segment disease, a single-stage transanal pull-through can be performed. The three classic surgical techniques are the Swenson (full-thickness resection and direct anastomosis), Duhamel (retrorectal pouch creation), and Soave (endorectal mucosal stripping with pull-through). All three achieve the same goal: removing the aganglionic segment and bringing the ganglionated bowel down to the anus. The Soave procedure is the most commonly used in modern practice.
If the child is unstable, severely distended, malnourished, or has active enterocolitis, a staged approach is preferred. The first stage involves a diverting colostomy placed in the most distal segment of bowel confirmed to contain ganglion cells (verified by frozen section at the time of surgery). Definitive pull-through is then performed months later once the child has recovered.
The most feared complication is Hirschsprung-associated enterocolitis (HAEC), which can occur before or after surgery. It presents with fever, explosive diarrhea, abdominal distension, and can progress to septic shock and perforation. HAEC requires aggressive treatment with IV antibiotics covering gram-negative and anaerobic organisms, frequent rectal irrigations, and full resuscitative support. This is the leading cause of mortality in Hirschsprung disease.
Postoperatively, families should be counseled about potential long-term complications including soiling, constipation, and enterocolitis recurrence. Most children achieve acceptable bowel function by school age, but a subset will require ongoing bowel management programs.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common trap with Hirschsprung disease on licensing exams is confusing it with functional constipation. Both present with chronic constipation in a young child, but the distinguishing detail is buried in the vignette: Hirschsprung constipation dates back to the neonatal period (often with delayed meconium passage documented in the birth history), and on rectal examination, the vault is empty because stool is trapped proximal to the aganglionic segment. In functional constipation, the rectum is full of stool because the problem is behavioral withholding, not anatomic obstruction. Another common pitfall is selecting the wrong diagnostic test. Students frequently choose anorectal manometry or barium enema as the definitive answer when the question stem asks for the confirmatory test. The answer is always rectal suction biopsy. Remember the rule: barium enema is the best initial test to identify the transition zone, but biopsy is required to confirm absent ganglion cells. A third trap involves the association with Down syndrome. Any vignette describing a child with trisomy 21 and chronic constipation since birth should trigger immediate consideration of Hirschsprung disease, not simple constipation attributed to hypotonia. Finally, be alert for the enterocolitis complication: a post-surgical Hirschsprung patient who returns with fever, explosive diarrhea, and distension has HAEC until proven otherwise, and the next best step is rectal irrigations with broad-spectrum antibiotics, not observation. The core competency being tested is your ability to recognize the classic neonatal presentation, select the correct confirmatory diagnostic test, and distinguish this condition from its closest mimics based on key clinical details woven into the vignette.