A 62-year-old woman comes to the office for diarrhea. She has had 4 or 5 watery, brown stools every day for the past 6 months. Although most episodes occur during the day, she wakes up at least once a night to defecate. There is no associated hematochezia, melena, vomiting, or unexpected weight loss. Medical history is significant for type 2 diabetes mellitus and hypertension. She takes lisinopril, insulin, and metformin. She has no recent travel or new medications. Family history is unremarkable. She does not drink alcohol. Temperature is 37.4 C (99.3 F), blood pressure is 125/80 mm Hg, and pulse is 80/min. The abdomen is nontender and nondistended. Complete blood count, serum chemistries, and stool studies are normal. Which of the following is the most likely cause of this patient's diarrhea?

Question

A 62-year-old woman comes to the office for diarrhea.  She has had 4 or 5 watery, brown stools every day for the past 6 months.  Although most episodes occur during the day, she wakes up at least once a night to defecate.  There is no associated hematochezia, melena, vomiting, or unexpected weight loss.  Medical history is significant for type 2 diabetes mellitus and hypertension.  She takes lisinopril, insulin, and metformin.  She has no recent travel or new medications.  Family history is unremarkable.  She does not drink alcohol.  Temperature is 37.4 C (99.3 F), blood pressure is 125/80 mm Hg, and pulse is 80/min.  The abdomen is nontender and nondistended.  Complete blood count, serum chemistries, and stool studies are normal.  Which of the following is the most likely cause of this patient's diarrhea?

Quizplus · Accepted Answer

11ec160b_3ada_9e8c_9249_e92c0a1db73d_MD0001_00 This patient with diabetes mellitus has several months of watery diarrhea that occurs both during the day and at night. In the setting of normal laboratory evaluation, this presentation suggests diabetic diarrhea due to diabetic autonomic neuropathy (DAN). Long-standing hyperglycemia results in the accumulation of cross-linked glycosylated serum proteins in the vasa nervorum, which causes inflammation and damage to peripheral nerves. Although this most commonly results in a distal, symmetric polyneuropathy of the feet, it can also result in damage to sympathetic and parasympathetic nerves, leading to autonomic dysfunction. Risk factors include poor glucose control and other vascular risk factors (eg, hypertension, obesity). Loss of autonomic input to the gastrointestinal tract results in abnormal peristalsis, leading to disordered small-bowel and colonic motility, which can result in rapid intestinal transport. Furthermore, intestinal water and electrolyte secretion is increased. Fecal incontinence is particularly common in patients with long-standing diabetes, resulting from both a large volume of watery diarrhea and decreased anorectal sensation. Other common gastrointestinal manifestations of DAN include gastroparesis and gastroesophageal reflux. Patients with diabetic diarrhea typically have painless, secretory-like diarrhea that persists with fasting (eg, nocturnal diarrhea). Laboratory evaluation, including fecal leukocytes and fecal occult blood testing, is usually unremarkable. (Choice A) Although altered small-bowel motility related to DAN can predispose to small intestinal bacterial overgrowth, this occurs due to an increase in small bowel bacteria, not a decrease in colonic bacterial burden. It typically causes abdominal bloating, discomfort, and gas. Nocturnal diarrhea is unexpected. (Choice B) Lactase deficiency can cause osmotic diarrhea after lactose ingestion, leading to postprandial loose stools and bloating. However, unless patients are eating during the night, nocturnal bowel movements would not occur. (Choice D) Exocrine pancreatic insufficiency (EPI), which is common in chronic pancreatitis or after pancreatic resection, leads to bulky, foul-smelling stool (eg, steatorrhea). Although insulin resistance can mildly impact pancreatic secretions, EPI leading to steatorrhea is rare in diabetes. (Choice E) Crohn disease, which causes transmural gastrointestinal inflammation, can cause watery diarrhea. However, abdominal pain, anemia, abnormal stool studies (eg, fecal occult blood, fecal calprotectin), and possibly fever are expected. Educational objective: Prolonged hyperglycemia in diabetes mellitus can injure the parasympathetic and sympathetic nervous system, resulting in diabetic autonomic neuropathy. This can lead to disordered small-bowel and colonic motility and increased intestinal secretions, resulting in secretory-like diarrhea (eg, fasting bowel movements).

A 62-Year-Old Woman Comes to the Office for Diarrhea