USMLE/COMLEX 1 - Nausea, Vomiting, Diarrhea

Here are key facts for USMLE Step 1 & COMLEX-USA Level 1 from the Nausea, Vomiting, Diarrheatutorial, as well as points of interest at the end of this document that are not directly addressed in this tutorial but should help you prepare for the boards. See the tutorial notes for further details and relevant links.

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1. Vomiting: Forceful eviction of the stomach contents caused by contractions of the GI tract and muscles of the thorax 2. Regurgitation: Ejection of food from the esophagus 1. Medications: Antibiotics, opioids, antidepressants, vitamins and mineral supplements, NSAIDs, chemotherapy 2. GI motility disorders: Damaged nerves or mechanical obstruction preventing normal passage of food 3. Neurological triggers: Motion sickness, central nervous disorders (migraines, infections, increased intra-cranial pressure) 4. Mechanical obstructions: Adhesions, volvulus, foreign bodies, hernias, tumors 1. Malabsorption disorders: Lactose intolerance, celiac disease 2. Inflammatory conditions: Inflammatory bowel disease (Crohn's disease and ulcerative colitis), microscopic colitis 3. Exocrine dysfunction: Pancreatic insufficiency leading to steatorrhea 1. Gastroenteritis: Infections from norovirus, rotavirus, E. coli, Salmonella, Shigella, and Campylobacter 2. Vascular conditions: Intestinal ischemia 3. Functional disorders: Irritable bowel syndrome 4. Endocrine disorders: Thyroid disorders, adrenal insufficiency, and diabetes

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1. Esophageal achalasia: Damaged esophageal nerves cause sustained lower esophageal sphincter contraction, presenting with heartburn, chest pain, and regurgitation 2. Gastroparesis: Results from vagus nerve damage and loss of stomach muscle function, causing early satiety, heartburn and vomiting 3. Early pregnancy: Associated with nausea and vomiting throughout the day, resulting from first trimester hormonal changes 4. Cyclical vomiting syndrome: Recurring severe episodes of vomiting triggered by stress and excitement, often beginning in childhood 1. Steatorrhea: Characteristic of pancreatic insufficiency, presents as oily, foul-smelling, yellowish stools that float due to high fat content 2. Carcinoid syndrome: Produced by neuroendocrine tumors in 30-40% of patients, characterized by watery, loose stools, flushing, wheezing, and valvular heart disease 1. Vomiting complications: Aspiration, dehydration, electrolyte imbalance, undernutrition, and esophageal tears 2. Diarrhea complications: Malabsorption of nutrients, dehydration, and electrolyte imbalances 1. IBD subtypes: Crohn's disease (mucous diarrhea) versus ulcerative colitis (bloody diarrhea) 2. Functional vs. organic: Irritable bowel syndrome results from disordered brain-gut communication

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Below is information not explicitly contained within the tutorial but important for USMLE & COMLEX 1. 1. Chemoreceptor trigger zone: Located in area postrema of medulla, responds to drugs and toxins 2. Vestibular apparatus: Connection to vomiting center explains motion sickness 3. Osmotic vs. secretory diarrhea: Different mechanisms of fluid accumulation in the intestinal lumen 1. Alarm symptoms: Blood in stool, nocturnal symptoms, weight loss suggesting organic disease 2. Bristol stool chart: Classification system for stool consistency 3. Acute vs. chronic: Management differs based on duration of symptoms 1. Laboratory evaluation: CBC, CMP, TSH, celiac panel, stool studies 2. Imaging studies: Abdominal X-ray for obstruction, CT for inflammation or masses 3. Endoscopic procedures: Upper endoscopy and colonoscopy for direct visualization 1. Fluid and electrolyte replacement: Critical first step in severe cases 2. Antiemetics: Classes include antihistamines, anticholinergics, 5-HT3 antagonists, and NK1 receptor antagonists 3. Antidiarrheals: Loperamide and bismuth subsalicylate mechanisms 4. Disease-specific therapy: Targeted approaches based on underlying etiology