Fecal Incontinence in Women: Causes and Treatment

Ashima Makol; Madhusudan Grover; William E Whitehead


Women's Health. 2008;4(5):517-528. 

In This Article

Risk Factors

Several risk factors for FI have been identified in epidemiological studies or clinical case series. We will first discuss those risk factors that are unique to women.

Obstetric trauma is a major predisposing factor.[38] The injury may involve either the external anal sphincter, internal anal sphincter or the pudendal nerves, or all three. Prospective studies demonstrate that nearly 35% of primiparous women have evidence of sphincter disruption following vaginal delivery,[38–40] and between a third to two-thirds of women who sustain a recognized third-degree tear during delivery subsequently suffer from FI.[41–43] More severe fourth-degree sphincter tears convey a greater risk of FI than smaller third-degree tears.[44,45] FI is known to be more prevalent in women who deliver vaginally and have recognized anal sphincter tears (17%) compared with those who deliver vaginally without such tears (8%).[46] Other important obstetrical risk factors for both sphincter laceration and FI are a cumulative number of vaginal deliveries,[47] vacuum extraction, forceps delivery, prolonged second stage of labor, large birthweight and occipito-posterior presentation.[48–51] Some studies suggest that cesarean delivery is associated with lower rates of sphincter laceration and FI compared with vaginal delivery,[52] but other studies find no significant difference.[53,54] When an obstetrical injury does occur, rates of FI are greatest in the immediate postpartum period and decline by 6 months.[55] However, FI can also occur or recur many years later.[56] It has been difficult to evaluate the long-term impact of sphincter laceration on FI because there is a strong tendency for the prevalence of FI to increase with age, independent of obstetric history.[1] However, it has been shown that women with a history of third- or fourth-degree sphincter laceration are at increased risk of sphincter laceration and incontinence during subsequent vaginal deliveries.[45]

Episiotomy is an obstetric technique in which the external sphincter is intentionally cut in the belief that this prevents uncontrolled tears on the perineum and sphincter during vaginal childbirth. This was once standard practice and is still performed in some places. However, large case series have demonstrated that episiotomy does not reduce the severity of sphincter lacerations or the risk of FI, but instead exacerbates it.[57,58] Midline episiotomies are associated with higher rates of sphincter laceration compared with mediolateral episiotomy.[59]

Hysterectomy is also a risk factor for FI in women, and the association is stronger if the hysterectomy is combined with oophorectomy.[14] The mechanism for this is unknown; it does not appear to be due to the loss of estrogen, since no differences in prevalence have been found between women on HRT and those not on it.[14]

Hemorrhoids are more common in women than in men and often develop for the first time during straining with childbirth.[60] Overall, 48–63% of patients with grade 3 or 4 hemorrhoids (requiring manual reduction), report soiling of underwear.[61,62] Moreover, surgical treatment of hemorrhoids sometimes includes a myectomy of the internal anal sphincter to reduce anal canal pressure (and, hence, reduce straining), and this is associated with an increasedincidence of FI. In a large case series at the Mayo Clinic (Rochester, MN, USA), myectomy was shown to result in some degree of FI in 45% of individuals postoperatively and was found to be significantly higher in women.[63]

There is a higher incidence of obstetrical injury in Asian compared with Caucasian women.[64] A postal survey carried out in 7879 women who delivered babies during the same year at three hospitals showed a higher incidence of FI in Asian women than in Caucasians (OR = 3.2).[52] However, another study reported a nonsignificant tendency for fewer Asian women to report FI compared with Caucasian women (21 vs 29%).[65] In the Childbirth and Pelvic Symptoms study,[46] there was indirect evidence to suggest that African–American women were less likely to sustain a third- or fourth-degree laceration (this was shown by the fact that they were less frequent in the control group without tears) and, among women with sphincter tears, African–Americans made up most (59%) of the ‘other races' category that were significantly less likely than Caucasians to report FI in the postpartum period. These differences may be related to anthropometric differences in pelvic anatomy.

Age is significantly associated with the prevalence of FI in both men and women,[46,66] although the physiological mechanisms that account for the increased risk of FI in older people are unknown. Age at childbirth is also associated with increased risk of obstetrical complications leading to an increased risk of FI.[46]

Diarrhea is consistently found to be a risk factor for FI in both men and women with odds ratios (ORs) generally above 4.[14,67] There is an interaction between stool consistency and structural defects to the sphincter – in women with third- or fourth-degree sphincter lacerations sustained during childbirth, the likelihood of FI is greater in women with frequent loose stools as compared to those with formed stools.[68] The relationship between diarrhea and FI is probably causative, as liquid stool is more difficult to control than solid stool. The symptom of urgency (having to rush to the toilet) has also been associated with FI. Two population-based surveys found urgency to be a strong risk factor (OR = 5) that is independent of diarrhea and other risk factors.[56,67]

Since pathophysiological mechanisms overlap for UI and FI, an association between the two would be expected. Population-based studies have demonstrated that up to 50% of patients with FI also have UI (double incontinence) and the risk of FI in individuals with UI may be increased by up to sixfold.[69–72] However, UI is probably not a contributing cause of FI; it serves only as a marker variable to alert the clinician to screen for FI.

Obesity is a risk factor for both FI and UI.[73] The mechanism for this may be that obesity increases the intra-abdominal pressure on the pelvis, rendering the continence mechanism less efficient. It is not known whether weight loss in the obese incontinent patient results in an improvement in FI.

Population-based studies have demonstrated an excess incidence of FI in patients with IBS (OR = 2–8),[66,74] and IBS is more common in women than in men by approximately 2:1.[75] Inflammatory bowel disease (ulcerative colitis and Crohn's disease) is also associated with a higher prevalence of FI.[76]

Many neurological disorders place patients at increased risk of FI. Diabetes mellitus (DM) was associated with a 40% increase in the risk of FI in one study.[66] In a large, population-based study, the proportion of patients reporting FI to occur at least several times was 12.8% for DM patients versus 3.8% in non-DM patients, while those reporting FI to occur often was 2.6 versus 0.8% in DM and non-DM patients, respectively; the OR was estimated to be 2.7.[77] Microvascular complications associated with DM may damage the innervation of the rectum and pelvic floor musculature and this is presumed to be the mechanism for the increased risk of FI in DM patients.[78] Other neurological diseases, including stroke, multiple sclerosis, dementia, traumatic spinal cord and brain injury, have been associated with FI. These can affect continence by interfering with sensory perception or motor function, or both. In the Copenhagen Stroke Study investigating 935 consecutive admissions for stroke, FI was transiently present in the majority of patients and the prevalence of FI remained elevated compared with population norms at 1 year.[79] A total of 30–50% of patients with multiple sclerosis are reported to have FI.[80] Idiopathic pudendal neuropathy is another common cause of FI, particularly in older women, and frequently occurs in association with a sphincter defect.[81]

In addition to its association with specific diseases and injuries affecting the pelvic floor, FI is also associated with a high overall burden of illness. Goode and colleagues found that poor self-perceived general health status was a risk factor for FI, with an OR measuring 1.9 among women with FI versus those without it.[14] There are also reports that childhood sexual or physical abuse and adult sexual abuse increase the risk of FI.[5] The mechanism for this is unknown.

The ability to determine risk factors for FI is limited by the way in which most studies have been designed and analyzed. The majority of studies on FI have been cross-sectional in design, which helps identify associations with FI but not causality. An example is UI, which is strongly associated with FI but is unlikely to be a cause of FI. Therefore, it is not known if changing a particular risk factor will reduce or eliminate FI. More prospective studies are needed to identify modifiable risk factors.


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