A 19-year-old college student comes to the physician with generalized weakness and diarrhea for the last year. She describes 8-10 watery bowel movements daily, including at night. She has abdominal cramps but no vomiting or blood or mucus in the stool. She drinks 8 cups of coffee daily but does not use tobacco, alcohol, or illicit drugs. She is currently applying for a merit scholarship and must be at the top of her class to qualify.
Her blood pressure is 92/54 mm Hg, pulse is 94/min, and respirations are 12/min. Her body mass index is 17 kg/m². Examination shows no abnormalities.
Stool study results are as follows:

An esophagogastroduodenoscopy is unremarkable with normal duodenal biopsies.
Which of the following is the most likely diagnosis?

Question

A 19-year-old college student comes to the physician with generalized weakness and diarrhea for the last year. She describes 8-10 watery bowel movements daily, including at night. She has abdominal cramps but no vomiting or blood or mucus in the stool. She drinks 8 cups of coffee daily but does not use tobacco, alcohol, or illicit drugs. She is currently applying for a merit scholarship and must be at the top of her class to qualify.
Her blood pressure is 92/54 mm Hg, pulse is 94/min, and respirations are 12/min. Her body mass index is 17 kg/m². Examination shows no abnormalities.
Stool study results are as follows:

An esophagogastroduodenoscopy is unremarkable with normal duodenal biopsies.
Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec193a_9812_0cb8_853d_df48fa6c3062_MD0002_00 This patient's clinical presentation suggests factitious diarrhea. Factitious diarrhea is most commonly due to laxative abuse or addition of substances (eg, water) that dilute the stool. The condition requires a high index of suspicion in patients with risk factors such as female gender, high education level, highly stressful environment, and low body mass index indicating possible anorexia nervosa. Other common findings include nocturnal symptoms, weight loss, orthostatic hypotension (if significant volume depletion is present), hypokalemia from prolonged diarrhea, and hypermagnesemia if magnesium-containing laxatives are used. Factitious diarrhea is a diagnosis of exclusion after ruling out organic causes. Patients will usually see multiple practitioners and deny any laxative abuse. Evaluation first involves 24-hour stool specimen to document liquid or solid stool. Liquid stool requires a fresh specimen for osmolality, sodium, potassium, and osmotic gap calculation. Osmolality < 250 mOsm/kg indicates possible water added to the stool, and osmolality > 400 mOsm/kg indicates possible urine in the stool. Stool osmolality of 250-400 mOsm/kg with osmotic gap < 75 mOsm/kg suggests secretory laxative use (eg, saline laxatives, senna, bisacodyl). Osmotic gap > 75 mOsm/kg suggests laxative use with unmeasured solute (eg, magnesium sulfate, lactulose, sorbitol). osmolality Esophagogastroduodenoscopy is typically normal in factitious diarrhea, but colonoscopy may show melanosis coli due to chronic laxative abuse. Stool testing for laxatives is not readily available. This patient has an osmotic diarrhea (stool osmotic gap of 130 mOsm/kg), most likely due to magnesium salt consumption. Measurement of stool magnesium is helpful as values > 108 mg/dL suggest magnesium-induced diarrhea. (Choices A, B, C, and E) Secretory diarrhea causes stool osmotic gap < 50 mOsm/kg. Causes include Crohn's disease (positive fecal leukocytes), collagenous colitis (microscopic colitis), hyperthyroidism (increased stool frequency rather than volume), and VIPomas (uncommon neuroendocrine tumors in the pancreas). This patient's elevated stool osmolal gap makes these unlikely. Educational objective: Factitious diarrhea is usually due to laxative abuse and is a diagnosis of exclusion that requires a high index of suspicion. Stool analysis typically shows osmotic diarrhea with osmolality of 250-400 mOsm/kg. Esophagogastroduodenoscopy is typically normal, but colonoscopy may show melanosis coli related to chronic laxative abuse. __________ References: Evaluation of chronic diarrhea. (http://www.ncbi.nlm.nih.gov/pubmed/22085666) Laxative abuse: epidemiology, diagnosis and management. (http://www.ncbi.nlm.nih.gov/pubmed/20687617)

A 19-Year-Old College Student Comes to the Physician with Generalized