A 45-year-old man comes to the office due to several months of diarrhea. The patient experiences watery diarrhea shortly after eating, occasional abdominal discomfort, easy fatigability, and unintentional weight loss. He has a history of Crohn disease for which he takes mesalamine. The patient also takes prednisone intermittently for disease exacerbations, and 6 months ago he was treated with metronidazole for a perianal abscess. Surgical history includes several intestinal resections due to complications of Crohn disease. He does not use tobacco or illicit drugs but drinks alcohol occasionally. Physical examination shows conjunctival pallor. The abdomen is nondistended, soft, and nontender. Vibratory and position sense are decreased in the lower extremities. Stool guaiac test is negative. Laboratory studies show macrocytic anemia and a low vitamin B₁₂ level. Which of the following is the most likely cause of this patient's presenting symptoms?

Question

Quizplus · Accepted Answer

This patient likely has short bowel syndrome, a malabsorptive condition that typically occurs in patients with massive small bowel resection and/or Crohn disease. Extensive intestinal disease or resection results in loss of absorptive surface area and a decrease in intestinal transit time, leading to postprandial voluminous diarrhea and weight loss due to malabsorption of macro- and micronutrients. Loss of functional distal ileum may specifically result in vitamin B₁₂ deficiency with macrocytic anemia, peripheral neuropathy, and subacute combined degeneration of the spinal cord (eg, impaired vibration and position sense). (Choice A) VIPoma is a pancreatic neuroendocrine tumor that secretes vasoactive intestinal polypeptide, resulting in secretory watery diarrhea (persists with fasting) and flushing. Malabsorption of macro- and micronutrients is not characteristic. (Choice B) Giardia is a protozoan parasite that may cause chronic diarrhea and malabsorption; however, infection typically occurs in high-risk individuals such infants, campers/hikers drinking from mountain streams, those who are immunocompromised, and travelers to resource-limited areas. (Choice C) Whipple disease is a rare multisystemic disorder caused by Tropheryma whipplei, a gram-positive, periodic acid-Schiff (PAS)-positive bacilli. Patients typically present with migratory polyarthritis followed by abdominal pain and malabsorptive diarrhea. Neurologic symptoms (eg, cognitive dysfunction, myoclonus) and cardiac disease (eg, endocarditis) are also characteristic. (Choice E) Numerous medications can cause diarrhea as an adverse effect; however, this is unlikely in this patient with malabsorption, vitamin B₁₂ deficiency, and weight loss in the setting of Crohn disease and intestinal resection. (Choice F) Chronic pancreatitis is most commonly caused by alcohol abuse and typically presents with abdominal pain and pancreatic insufficiency. Patients often have chronic diarrhea/malabsorption due to lack of digestive enzymes (exocrine insufficiency) and diabetes mellitus due to endocrine insufficiency. (Choice G) Dumping syndrome may occur after gastric bypass surgery or damage to the pyloric sphincter. Emptying of hyperosmolar chyme into the small intestine causes a rapid shift of fluid from the serum to the intestine, resulting in postprandial gastrointestinal (eg, nausea/vomiting, cramps, diarrhea) and vasomotor symptoms (eg, diaphoresis, flushing). Educational objective: Short bowel syndrome typically occurs in patients with massive small bowel resection and/or Crohn disease due to loss of intestinal absorptive surface area and a decrease in intestinal transit time. Patients usually present with postprandial voluminous diarrhea and weight loss due to malabsorption. Loss of functional distal ileum may result in vitamin B₁₂ deficiency. __________ References: Short bowel syndrome: a review of management options. (http://www.ncbi.nlm.nih.gov/pubmed/21727727) The pathophysiology of malabsorption. (http://www.ncbi.nlm.nih.gov/pubmed/26288588) Short bowel syndrome and malabsorption - causes and prevention. (http://www.ncbi.nlm.nih.gov/pubmed/26288591)

A 45-Year-Old Man Comes to the Office Due to Several