Fecal incontinence (FI), or in some forms, encopresis, is a lack of control over defecation, leading to involuntary loss of bowel contents — including flatus (gas), liquid stool elements and mucus, or solid feces.

The most common causes are thought to be immediate or delayed damage from childbirth, complications from prior anorectal surgery (especially involving the anal sphincters or hemorrhoidal vascular cushions), altered bowel habits (e.g., caused by irritable bowel syndrome, Crohn's disease, ulcerative colitis, food intolerance, or constipation with overflow incontinence).

[3][4] Fecal incontinence has three main consequences: local reactions of the perianal skin and urinary tract, including maceration (softening and whitening of the skin due to continuous moisture), urinary tract infections, or decubitus ulcers (pressure sores);[1] a financial expense for individuals (due to the cost of medication and incontinence products, and loss of productivity), employers (days off), and medical insurers and society generally (health care costs, unemployment);[1] and an associated decrease in quality of life.

[5] There is often reduced self-esteem, shame, humiliation, depression, a need to organize life around easy access to a toilet, and avoidance of enjoyable activities.

For example, obstetric injury may precede onset by decades, but postmenopausal changes in the tissue strength reduce in turn the competence of the compensatory mechanisms.

[1][10] The most common factors in the development are thought to be obstetric injury and after-effects of anorectal surgery, especially those involving the anal sphincters and hemorrhoidal vascular cushions.

The resting tone of the anal canal is not the only important factor; both the length of the high-pressure zone and its radial translation of force are required for continence.

This means that even with normal anal canal pressure, focal defects such as the keyhole deformity can be the cause of substantial symptoms.

[22] Lesions which mechanically interfere with, or prevent the complete closure of the anal canal can cause a liquid stool or mucous rectal discharge.

[5] A weakened puborectalis leads to widening of the anorectal angle and impaired barrier to the stool in the rectum entering the anal canal, and this is associated with incontinence to solids.

Hospitalized patients and care home residents may develop FI via this mechanism,[8] possibly a result of lack of mobility, reduced alertness, the constipating effect of medication, and/or dehydration.

[29] Therefore, the recto-anal inhibitory reflex (RAIR) is persistently activated, meaning the internal anal sphincter relaxes, which is not under voluntary control.

[29] Nitrates, calcium channel antagonists, beta-adrenoceptor antagonists (beta-blockers), sildenafil, selective serotonin reuptake inhibitors Cephalosporins, penicillins, macrolides Glyceryl trinitrate ointment, diltiazem gel, bethanechol cream, botulinum toxin A injection Laxatives, metformin, orlistat, selective serotonin reuptake inhibitors, magnesium-containing antacids, digoxin Loperamide, opioids, tricyclic antidepressants, aluminium-containing antacids, codeine Benzodiazepines, tricyclic antidepressants, selective serotonin reuptake inhibitors, anti-psychotics Continence requires conscious and subconscious networking of information from and to the anorectum.

Chronic conditions, such as irritable bowel syndrome or Crohn's 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.

[36] Females have lower anal canal pressures and less robust sphincters than males, which may make them more susceptible to incontinence, particularly if coercion is involved.

The rectoanal excitatory reflex (RAER) is an initial, semi-voluntary contraction of the EAS and puborectalis which in turn prevents incontinence following the RAIR.

Digital rectal examination is performed to assess resting pressure and voluntary contraction (maximum squeeze) of the sphincter complex and puborectalis.

[38] Proctosigmoidoscopy involves the insertion of an endoscope (a long, thin, flexible tube with a camera) into the anal canal, rectum and sigmoid colon.

The procedure allows for visualization of the interior of the gut and may detect signs of disease or other problems that could be a cause, such as inflammation, tumors, or scar tissue.

[40] The Rome process published diagnostic criteria for functional FI, which they defined as "recurrent uncontrolled passage of fecal material in an individual with a developmental age of at least four years".

[1][2][5][8][10] "Social continence" has been given various precise definitions for the purposes of research; however, generally it refers to symptoms being controlled to an extent that is acceptable to the individual in question, with no significant effect on their life.

Discharge generally refers to conditions where there is pus or increased mucus production, or anatomical lesions that prevent the anal canal from closing fully, whereas fecal leakage generally concerns disorders of IAS function and functional evacuation disorders which cause a solid fecal mass to be retained in the rectum.

[2] In children over the age of four who have been toilet trained, a similar condition is generally termed encopresis (or soiling), which refers to the voluntary or involuntary loss of (usually soft or semi-liquid) stool.

[55] However, persistent leaking of residual irrigation fluid during the day may occur and make this option unhelpful, particularly in persons with obstructed defecation syndrome who may have an incomplete evacuation of any rectal contents.

Consequently, the best time to carry out the irrigation is typically in the evening, allowing any residual liquid to be passed the next morning before leaving the home.

[59] Anal plugs (sometimes termed tampons) aim to block the involuntary loss of fecal material, and they vary in design and composition.

[63][64] Risk factors include age, female gender, urinary incontinence, history of vaginal delivery (non-Caesarean section childbirth), obesity,[45] prior anorectal surgery, poor general health, and physical limitations.

[70] In 1975, Parks describes post anal repair, a technique to reinforce the pelvic floor and EAS to treat idiopathic cases.

During the last 20 years, dynamic graciliplasty, sacral nerve stimulation, injectable perianal bulking agents and radiofrequency ablation have been devised, mainly due to the relatively poor success rates and high morbidity associated with the earlier procedures.