Since the hemorrhoidal vascular cushions contribute 15% of the resting anal tone, surgeries involving these structures may affect continence status. Partial internal sphincterotomy, fistulotomy, anal stretch (Lords operation), hemorrhoidectomy or transanal advancement flaps may all lead to FI post operatively, with soiling being far more common than solid FI. The "keyhole deformity" refers to scarring within the anal canal and is another cause of mucus leakage and minor incontinence. This defect is also described as a groove in the anal canal wall, and may occur after posterior midline fissurectomy or fistulotomy, or with lateral IAS defects. Rare causes of traumatic injury to the anal sphincters include military or traffic accidents complicated by pelvic fractures, spine injuries or perineal lacerations, insertion of foreign bodies in the rectum, and sexual abuse. Nontraumatic conditions causing anal sphincter weakness include scleroderma, damage to the pudendal nerves and IAS degeneration of unknown cause. Radiation induced FI may involve the anal canal as well as the rectum, when proctitis, anal fistula formation and diminished function of internal and external sphincter occur. Irradiation may occur during radiotherapy, e.g. for prostate cancer. Pelvic floor
Many people with FI have a generalized weakness of the pelvic floor, especially puborectalis. A weakened puborectalis leads to widening of the anorectal angle, and impaired barrier to stool in the rectum entering the anal canal, and this is associated with incontinence to solids. Abnormal descent of the pelvic floor can also be a sign of pelvic floor weakness. Abnormal descent manifests as descending perineum syndrome (>4 cm perineal descent).
Other causes of incomplete evacuation include non-emptying defects like a rectocele. Straining to defecate pushes stool into the rectocele, which acts like a diverticulum and causes stool sequestration. Once the voluntary attempt to defecate, albeit dysfunctional, is finished, the voluntary muscles relax, and residual rectal contents are then able to descend into the anal canal and cause leaking. : 37

Central nervous system
Continence requires conscious and subconscious networking of information from and to the anorectum. Defects/brain damage may affect the central nervous system focally (e.g. stroke, tumor, spinal cord lesions, trauma, multiple sclerosis) or diffusely (e.g. dementia, multiple sclerosis, infection, Parkinsons disease or drug-induced). FI (and urinary incontinence) may also occur during epileptic seizures. Dural ectasia is an example of a spinal cord lesion that may affect continence. Diarrhea
Liquid stool is more difficult to control than formed, solid stool. Hence, FI can be exacerbated by diarrhea. Some consider diarrhea to be the most common aggravating factor. Where diarrhea is caused by temporary problems such as mild infections or food reactions, incontinence tends to be short lived. Chronic conditions, such as irritable bowel syndrome or Crohns disease, can cause severe diarrhea lasting for weeks or months. Diseases, drugs, and indigestible dietary fats that interfere with the intestineal absorption may cause steatorrhea (oily rectal discharge & fatty diarrhea) and degrees of FI. Respective examples include cystic fibrosis, orlistat, and olestra. Postcholecystectomy diarrhea is diarrhea that occurs following gall bladder removal, due to excess bile acid. Orlistat is an anti-obesity (weight loss) drug that blocks the absorption of fats.