1 General introduction 19 Pathophysiology Although the etiology of CAF is uncertain, it is assumed that pain causes an increased sphincter pressure leading to diminished anodermal blood flow and local ischemia.9,10 Besides that, passing of hard stools or sudden evacuation of liquid stool can lead to mucosal damage, resulting in an overreaction of the external anal sphincter (EAS) continence reflex and an increase of basal resting pressure.28 This could lead to spasm which prevents CAF from healing.28,29 It is also theorized that insufficient stretchability of the anal sphincters leads to mucosal tears during defecation and this mucosa releases vasoconstrictors which arrests the healing process.30 Another hypothesis is that pelvic floor dysfunction may be part of the pathophysiology. In a retrospective study among 179 patients diagnosed with CAF, it was found that a large percentage of the patients had pelvic floor complaints such as obstructive defecation, sexual complaints, and pelvic floor dysfunction.31 Chronic constipation is also a predisposing factor.32
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