A 46-year-old woman comes to the office due to fecal incontinence. For the past several years, the patient has had fecal incontinence a few times per year. However, over the past year, it has worsened and now occurs once or twice a week, with leakage of liquid fecal material and a small amount of diarrhea. The patient has a formed bowel movement once a day. She has tried to change her diet, increasing dietary fiber and avoiding dairy products, but has had no improvement in her symptoms. The patient takes metformin for type 2 diabetes mellitus, and her last hemoglobin A1c was 7.2%. She has had 2 vaginal deliveries and no surgeries. BMI is 24 kg/m². Vital signs are normal. The abdomen is soft and nontender and has normoactive bowel sounds. There is a moderate amount of soft stool in the rectal vault, and anal sphincter tone is decreased. Deep tendon reflexes and sensation are intact in the bilateral lower extremities. Which of the following is the most likely cause of this patient's presentation?

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11ec25c8_d9c0_f0ac_bc81_89a7f5d9c39e_MD0003_00 Fecal incontinence, an involuntary loss of solid and/or liquid stool, can occur due to a variety of causes. In this woman with decreased anal sphincter tone, the most likely cause is an external anal sphincter (EAS) injury. EAS injuries are common in women because obstetric trauma (eg, from prior vaginal deliveries) can injure the pudendal nerve, which innervates the EAS, and/or cause direct damage to the anal sphincter muscle (ie, third- or fourth-degree perineal lacerations). Fecal incontinence due to EAS injury may be delayed (ie, presenting years after delivery) and initially intermittent because surrounding pelvic floor muscles and connective tissue can help compensate for the injured EAS and maintain continence. However, with age-related atrophy of the pelvic floor muscles, fecal incontinence can become increasingly frequent and severe (as in this patient). EAS injuries perineal lacerations On examination, patients typically have decreased anal sphincter tone and an asymmetric anal wink; patients with a large sphincter injury may have a palpable defect. The diagnosis is confirmed with endoanal ultrasound. Initial treatment includes dietary modification, bowel training, and antidiarrheal medication; surgical repair is based on symptom severity and patient preference. endoanal ultrasound (Choice A) Chronic fecal impaction can cause fecal incontinence when loose or liquid stool flows around the impacted stool in the rectum. This patient has daily, formed bowel movements, making this diagnosis unlikely. (Choice B) Decreased compliance of the rectum, which is normally elastic, can be caused by rectal fibrosis (eg, prior pelvic radiation). The stiffened rectal wall limits rectal expansion for stool storage, resulting in fecal incontinence plus increased stool frequency and urgency, which are not seen in this patient. (Choice D) Metformin can cause nausea/vomiting, abdominal pain, and diarrhea, but it does not typically cause isolated fecal incontinence. (Choice E) Although this patient with diabetes is at risk for diabetic autonomic neuropathy (ie, fecal incontinence due to decreased internal anal sphincter sensation), this condition is classically associated with upper gastrointestinal tract symptoms (eg, gastroparesis). In addition, severe autonomic neuropathy is usually preceded by peripheral neuropathy (eg, decreased sensation in the lower extremities), which is not seen in this patient. Educational objective: A common cause of fecal incontinence is external anal sphincter injury associated with obstetric trauma, which can cause direct sphincter muscle injury and/or denervation, resulting in decreased anal sphincter tone. Patients can have a delayed or intermittent presentation due to the gradual loss of compensatory pelvic floor stability with age. References: Obstetrics and fecal incontinence. (http://www.ncbi.nlm.nih.gov/pubmed/25320570) Office-based management of fecal incontinence. (http://www.ncbi.nlm.nih.gov/pubmed/23935551)

A 46-Year-Old Woman Comes to the Office Due to Fecal