E
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correct answer
E Intrasphincteric botulinum toxin (Botox™) injection
Internal anal spincter achalasia (IASA) is a condition defined by the absence of the rectoanal inhibitory reflex (RAIR) with normal ganglion cells present in a suction or full thickness rectal biopsy. Historically, the term “ultrashort Hirschsprung disease” has been used interchangeably with IASA by some authors, however contemporary studies differentiate the two conditions based on the presence or absence of ganglion cells, with ultrashort HD usually referring to a 1-3 cm length of aganglionosis.
IASA tends to differ in its clinical presentation compared to HD. A recent series of 192 children undergoing high resolution anorectal manometry for chronic constipation identified 28 children with a median age 6 years, who met diagnostic criteria of IASA (ie absent RAIR with ganglion cells present). In comparison to 53 children with HD, IASA patients were more likely to have passed meconium within 48h and experienced onset of symptoms later than HD patients, but earlier than those diagnosed with functional constipation.
Response to treatment for IASA is variably reported. A systematic review of 395 patients treated with either internal sphincter myectomy or Botox™ reported that myectomy patients were more likely to achieve regular bowel movements. This review included studies published over 40 years ago, and so the accuracy of diagnosis should not be assumed. Other reports describe the safety and effectiveness of Botox™ injection, particularly if done with ultrasound guidance, with response rates of variable duration ranging from 55-95%. Myectomy as a first line procedure should be discouraged, given the effectiveness of Botox™ and the potential detrimental effects on continence that may not become apparent for years.
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