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-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.
- 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.
- In low fistula, rectal pouch is distal to the Stephen’s line (Pubococcygeal line).
- In intermediate, pouch is at the level of ischial spine (Kelly’s point).
- In high fistula, rectal pouch is proximal to the Stephen’s line.
- 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