ANORECTAL MALFORMATIONS (ARM)

- It is due to imperfect fusion of post-allantoic gut with the proctodaeum.

- Incidence is one in 4500 newborns.

Present classification of ARM—

• Nonsyndromic ARM
• Nonsyndromic ARM with fistula

- Recto-perineal

- Recto-urinary (with bladder neck, bulbar or prostatic urethra) in males.

- Rectovestibular, rectovaginal, cloacal in females.

• Nonsyndromic ARM without fistula – imperforate anus
• Nonsyndromic complex fistula—cloaca with short common channel <3 cm; cloaca with long common channel >3 cm; H shaped rectovaginal fistula; rectal duplication.
• Syndromic ARM—associated with different syndromes.

CLINICAL FEATURES: -

- Newborn presents with inability to pass meconium, abdominal distension, features of intestinal obstruction, improper anal dimple,sometimes with complaints of passing meconium per urethra.

- It can be associated with—cardiac anomaly, tracheo-oesophageal fistula, renal anomalies, spinal anomalies. VATER/VACTERL anomaly.

- Most common ARM in boys is rectobulbar fistula with fistula beginning distal to puborectalis from distal rectum to bulbar urethra.

- Most common ARM in females is rectovestibular fistula.

INVESTIGATIONS: -

1. Wangenstein’s invertogram: Usually done 6–12 hours after birth, so as to allow air to reach the rectal pouch. A metal coin (marker) is strapped at the presumed site of anus and X-ray is taken. Length between the rectal pouch and anal dimple marker is more than 2.5 cm in high anal fistula.
2. In low fistula, rectal pouch is distal to the Stephen’s line (Pubococcygeal line).
3. In intermediate, pouch is at the level of ischial spine (Kelly’s point).
4. In high fistula, rectal pouch is proximal to the Stephen’s line.
5. Murugassu’s technique: Through visible anal dimple, meconium is aspirated by passing a needle into the rectal pouch in sitting propped up position. Watersoluble iodine dye is injected. Lateral X-ray is taken to study the level through Stephen line and Kelly’s point