Birth injury not major cause of late-onset fecal incontinence
MedWire News: Extensive episiotomy is the only obstetric event to increase the likelihood of late-onset fecal incontinence (FI), US researchers suggest.
The team from the Mayo Clinic in Rochester, Minnesota, found that, unlike grade 3 or 4 episiotomy, other birth factors such as prolonged labor or forceps-assisted delivery did not significantly predict the risk for FI years later.
Although obstetric pelvic floor injury is a risk factor for postpartum FI, the majority of women with FI develop symptoms decades after vaginal delivery, and obstetric history is not significantly linked to FI in this population, explain Adil Bharucha and co-authors.
Acknowledging that obstetric events are an imperfect surrogate marker for anal and pelvic floor injury, which may not be symptomatic, the team examined the relationship between birth and FI further in a nested case-control study of 68 women with FI (average age 57 years) and 68 age-matched population-based women without the condition.
The women's obstetric records were reviewed, their bowel habits recorded, and magnetic resonance imaging (MRI) was used to examine pelvic floor anatomy and motion during voluntary contraction and defecation.
FI began after the age of 40 years in 91% of patients, and after the age of 60 years in 44% of patients. Taking into consideration FI frequency and type (passive, urge, both, or neither), and stool volume and consistency, the patients were classified as having mild (29%), moderate (65%), or severe (6%) FI.
In multivariate analysis, women with FI were a significant 8.8 times more likely than controls to have internal sphincter injury (28 vs 6%), and 1.7 times more likely to have a reduced perineal descent during defecation (2.6 vs 3.1 cm).
Women with FI were also more likely than controls to have external sphincter injury (25 vs 4%), but this was no longer significant after adjusting for confounding factors.
Although puborectalis injury was significantly linked to impaired anorectal motion during squeeze, it was not an independent predictor for FI, the researchers note.
Women who had undergone grade 3 or 4 episiotomy were 3.9 times more likely to have pelvic floor injury and therefore be at increased risk for FI. No other obstetric event was associated with pelvic floor injury.
Of note, women with external sphincter atrophy were more likely to be heavy smokers, defined as 20 or more pack-years, than those without (50 vs 23%), although the numbers of women affected were small so the association was only of borderline significance.
"These findings may be partly explained by observations that smoking impairs muscle protein synthesis and increases the expression of genes associated with impaired muscle maintenance, thereby increasing the risk of sacropenia in skeletal muscle," Bharucha et al suggest.
The team also notes that FI was associated with the proportion of urgent bowel movements and loose stool consistency, supporting previous guidelines stating that women with FI should at first be conservatively treated with guidance on managing bowel disturbances.
"However, anal imaging should be considered in women who have refractory FI despite adequate management of bowel disturbances," the researchers say.
As anal sphincter defects were noted on asymptomatic controls as well as FI patients, the researchers conclude that consensus guidelines recommending surgical repair of defects in patients with idiopathic FI should be "revisited."
They recommend MRI evaluation of pelvic floor motion to determine whether pelvic floor training with biofeedback therapy may be of benefit to patients with FI. They suggest that the technique could also be used to elucidate the impact of pelvic floor injury on function, and potentially whether the patient will benefit from sphincteroplasty.
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By Lynda Williams