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The Human Phenotype Ontology (HPO) is downloaded weekly from The file downloaded is considered the "last stable build" available for the ontology. For more about the HPO, view their website at

Term:Internal anal sphincter achalasia
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Accession:HP:6000018 term browser browse the term
Definition:A disorder of the internal anal sphincter (IAS) in which the IAS fails to relax that manifests clinically as intractable constipation.
Comment:The internal anal sphincter, which is a specialized smooth muscle continuation of the circular muscle layer of rectum, plays a significant role in the maintenance of anorectal continence and in the pathophysiology of incontinence and constipation. Internal anal sphincter achalasia is a clinical condition with presentation similar to Hirschsprung disease but with the presence of ganglion cells on suction rectal biopsy.
Synonyms:exact_synonym: Anal achalasia

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  Human phenotype 0
    Phenotypic abnormality 0
      Abnormality of the digestive system 0
        Abnormality of digestive system physiology 0
          Abnormal anus physiology 0
            Internal anal sphincter achalasia 0
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