A 32-year-old man is evaluated for recurrent nausea and vomiting. The patient has nausea and upper abdominal discomfort after meals and feels full even after eating a small amount of food. He also has experienced several episodes of vomiting of undigested food particles but has had no fever or diarrhea. The patient has a history of type 1 diabetes mellitus and diabetic neuropathy. Physical examination shows a clear oropharynx. The abdomen is soft, nondistended, and nontender with no organomegaly. Bowel sounds are normoactive. Stool testing for occult blood is negative. Upper gastrointestinal endoscopy reveals no abnormalities. Treatment with an oral medication is initiated, but it is stopped after the patient experiences abnormal involuntary movements. A macrolide antibiotic is prescribed, which improves his symptoms. Which of following mechanisms is most likely responsible for the improvement in this patient's symptoms?

Question

A 32-year-old man is evaluated for recurrent nausea and vomiting.  The patient has nausea and upper abdominal discomfort after meals and feels full even after eating a small amount of food.  He also has experienced several episodes of vomiting of undigested food particles but has had no fever or diarrhea.  The patient has a history of type 1 diabetes mellitus and diabetic neuropathy.  Physical examination shows a clear oropharynx.  The abdomen is soft, nondistended, and nontender with no organomegaly.  Bowel sounds are normoactive.  Stool testing for occult blood is negative.  Upper gastrointestinal endoscopy reveals no abnormalities.  Treatment with an oral medication is initiated, but it is stopped after the patient experiences abnormal involuntary movements.  A macrolide antibiotic is prescribed, which improves his symptoms.  Which of following mechanisms is most likely responsible for the improvement in this patient's symptoms?

Quizplus · Accepted Answer

This patient with diabetes mellitus has postprandial nausea, vomiting of undigested food, bloating, and early satiety, raising strong suspicion for diabetic gastroparesis, an autonomic neuropathy of the gastrointestinal tract marked by delayed gastric emptying in the absence of mechanical obstruction (eg, normal esophagogastroduodenoscopy [EGD]). Metoclopramide, a dopamine 2 receptor antagonist, can improve symptoms but is occasionally associated with extrapyramidal side effects (eg, dystonia) and tardive dyskinesia (eg, involuntary movements). For patients with gastroparesis who cannot tolerate metoclopramide, erythromycin, a macrolide antibiotic, can be used as an alternate prokinetic agent. The prokinetic effects of erythromycin stem from the activation of the motilin receptor in the smooth muscle of the upper digestive tract, which results in coordinated peristaltic contractions that begin in the stomach and move through the entire upper digestive system (thereby propelling food into the colon). When used as an antibiotic, erythromycin can cause significant abdominal cramping, but in the setting of gastroparesis, the prokinetic effects can be leveraged to improve gastric emptying and ameliorate gastroparesis symptoms. However, the agonist effects of erythromycin diminish over time (tachyphylaxis) so it is generally used for short periods (<4 weeks). (Choices B and C) Patients with irritable bowel syndrome (IBS) who have significant gastrointestinal bloating symptoms can be treated with antispasmodic medications (eg, dicycloverine) that block gastrointestinal muscarinic receptors. Those with constipation-predominant IBS are sometimes treated with lubiprostone, a chloride channel activator, to increase intestinal fluid secretion. IBS is usually marked by periods of diarrhea and/or constipation and abdominal bloating; early satiety and vomiting of undigested food would be atypical. (Choice D) Peptic ulcer disease (PUD) is treated with medications (eg, proton pump inhibitor, sucralfate) that have a protective effect on the gastrointestinal mucosa. Although PUD can occasionally cause nausea, vomiting, and early satiety due to gastric outlet obstruction, most patients have significant upper abdominal pain. In addition, an EGD would show a gastric or duodenal ulcer. (Choice E) Patients with small intestinal bacterial overgrowth (SIBO)-colonization of the small intestine with colonic bacteria-often develop bloating, abdominal discomfort, flatulence, and/or diarrhea. However, early satiety and vomiting of undigested food would be atypical. In addition, SIBO is generally treated with rifaximin or neomycin. Educational objective: Erythromycin stimulates upper gastrointestinal motility by acting as an agonist on motilin receptors in the muscularis externa. Therefore, it can be used to treat gastroparesis (ie, delayed gastric emptying), a condition that frequently occurs in patients with long standing diabetes mellitus.

A 32-Year-Old Man Is Evaluated for Recurrent Nausea and Vomiting