A 62-year-old woman comes to the office due to a change in bowel habits. For 2 months, she has had bowel movements once every 5 or 6 days. The patient describes her stools as hard and lumpy and of small volume; defecation is uncomfortable. She has no trouble passing gas and has no other symptoms, including no nausea, vomiting, or weight changes. The patient was admitted to the hospital 3 months ago for acute diverticulitis, and her hospital course was complicated by new-onset atrial fibrillation. Colonoscopy a month after hospitalization revealed sigmoid diverticulosis but no masses or polyps. The patient takes fiber supplements, diltiazem, and apixaban. She does not use tobacco or alcohol. Vital signs are within normal limits. Cardiac auscultation reveals an irregular heart rhythm but no murmurs. Abdominal examination is significant for mild distension. Which of the following best explains this patient's symptoms?

Question

A 62-year-old woman comes to the office due to a change in bowel habits.  For 2 months, she has had bowel movements once every 5 or 6 days.  The patient describes her stools as hard and lumpy and of small volume; defecation is uncomfortable.  She has no trouble passing gas and has no other symptoms, including no nausea, vomiting, or weight changes.  The patient was admitted to the hospital 3 months ago for acute diverticulitis, and her hospital course was complicated by new-onset atrial fibrillation.  Colonoscopy a month after hospitalization revealed sigmoid diverticulosis but no masses or polyps.  The patient takes fiber supplements, diltiazem, and apixaban.  She does not use tobacco or alcohol.  Vital signs are within normal limits.  Cardiac auscultation reveals an irregular heart rhythm but no murmurs.  Abdominal examination is significant for mild distension.  Which of the following best explains this patient's symptoms?

Quizplus · Accepted Answer

11ec160b_3bcc_c78d_9249_ab05e9b787a9_MD0001_00 Constipation is an exceedingly common gastrointestinal condition with a wide variety of underlying etiologies (eg, autonomic neuropathy, hypothyroidism, electrolyte abnormalities). In this patient who developed constipation after new-onset atrial fibrillation, the most likely etiology is a drug effect related to diltiazem. Diltiazem and verapamil are non-dihydropyridine calcium channel blockers that decrease conduction velocity in the sinoatrial and atrioventricular nodes and are often used in the management of atrial fibrillation. Constipation, a common adverse effect, occurs due to inhibition of the colonic migrating motor complex, resulting in slowed contractions of colonic smooth muscle. This is not typically seen with dihydropyridine calcium channel blockers (eg, amlodipine, nifedipine). Other common medications that cause constipation include opiates, serotonin 5-HT₃ antagonists (eg, ondansetron), iron tablets, aluminum-containing agents (eg, antacids), and medications with anticholinergic properties (eg, diphenhydramine, tricyclic antidepressants, first-generation antipsychotics). (Choice A) Alterations in the colonic microbiome are common after antibiotic therapy but typically cause diarrhea (eg, Clostridioides [formerly Clostridium] difficile colitis), not constipation. (Choice B) The gastrocolic reflex is a neurogenic reflex triggered by gastric distension from food, leading to colonic contractions; impairment of the reflex can cause constipation. However, this typically occurs in patients with diabetic neuropathy and gastroparesis. (Choice C) Inappropriate contraction of pelvic floor muscles occurs with dyssenergic defecation, preventing the expulsion of stool from the rectum. Dyssenergic defecation is more common in the elderly and often associated with neurologic disorders (eg, Parkinson disease) or trauma. The development of symptoms after this patient started diltiazem is more consistent with medication-induced constipation. (Choice E) A rectocele, which occurs when the rectum prolapses into the posterior vaginal wall, usually develops in elderly, multiparous women. Although constipation is common, patients usually describe pelvic pressure and the need to manually push on the vagina or rectum to defecate. (Choice F) Sigmoid volvulus typically presents with progressive abdominal pain, nausea, and constipation and eventually results in bowel obstruction (eg, failure to pass gas, obstipation, possible perforation). Symptoms occur over the course of days, not months. Educational objective: Constipation is a common adverse effect of non-dihydropyridine calcium channel blockers (eg, diltiazem, verapamil). Other medications that cause constipation include opiates, 5-HT₃ antagonists, iron tablets, aluminum-containing antacids, and medications with anticholinergic properties. __________ References: Effects of 5-hydroxytryptamine (serotonin) type 3 antagonists on symptom relief and constipation in nonconstipated irritable bowel syndrome: a systematic review and meta-analysis of randomized controlled trials. (http://www.ncbi.nlm.nih.gov/pubmed/18242143) Nifedipine and verapamil inhibit the sigmoid colon myoelectric response to eating in healthy volunteers. (http://www.ncbi.nlm.nih.gov/pubmed/9514436)

A 62-Year-Old Woman Comes to the Office Due to a Change