Anus and perianal area
Benign or nonneoplastic lesions
Internal anal sphincter achalasia

Author: Elliot Weisenberg, M.D. (see Authors page)

Revised: 3 October 2017, last major update August 2014

Copyright: (c) 2002-2017,, Inc.

PubMed Search: Internal anal sphincter achalasia

Cite this page: Weisenberg, E. Internal anal sphincter achalasia. website. Accessed May 21st, 2018.
Definition / general
  • Uncommon condition with presentation similar to Hirschsprung disease, i.e. bowel obstruction with dilation of bowel proximal to the anal sphincter but with the presence of ganglia on biopsy
  • Poorly understood, likely multifactorial:
    • Lack of nitrergic (mediated by nitric oxide) innervations
    • Defective innervation of the neuromuscular junction
    • Decreased peripheral nerve fibers
    • Absent or markedly decreased interstitial cells of Cajal that leads to failure of relaxation of the internal anal sphincter in response to rectal distension (the rectosphincteric inhibitory reflex) (Semin Pediatr Surg 2009;18:246)
Clinical features
  • Similar to Hirschsprung disease
  • Manometry shows absence of rectosphincteric inhibitory reflux with rectal inflation
  • Rectal suction biopsy shows presence of ganglia
Prognostic factors
  • Most patients respond well to treatment
Microscopic (histologic) description
  • Presence of ganglia. decreased peripheral nerve fibers with special stains, marked decrease to absence of interstitial cells of Cajal with c-kit immunostaining (Arch Pathol Lab Med 2003;127:1192)
Microscopic (histologic) images

Images hosted on other servers:

Reduction of nerve fibers and interstitial cells of Cajal

Negative stains
Differential diagnosis