IBS, achalasia, gastroparesis, and GERD mechanisms and distinguishing features tested on USMLE Step 1.
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- What are the Rome IV criteria for diagnosing irritable bowel syndrome (IBS)?
- Recurrent abdominal pain at least 1 day/week in the last 3 months, associated with defecation, a change in stool frequency, or a change in stool form
- What are the three main subtypes of IBS based on predominant stool pattern?
- IBS-C (constipation-predominant), IBS-D (diarrhea-predominant), and IBS-M (mixed)
- Name three red flag symptoms that argue against a diagnosis of IBS and suggest another cause
- Weight loss, blood in stool, and nocturnal symptoms (waking from sleep with pain/diarrhea)
- What is the proposed underlying pathophysiology of IBS?
- Visceral hypersensitivity and altered brain-gut signaling, without structural or biochemical abnormality
- What is first-line treatment for constipation-predominant IBS (IBS-C)?
- Increased dietary fiber and osmotic laxatives; if inadequate, agents like linaclotide or lubiprostone
- What is a first-line pharmacologic option for diarrhea-predominant IBS (IBS-D)?
- Loperamide
- What is functional dyspepsia?
- Chronic upper abdominal discomfort or pain without an identifiable structural or biochemical cause on workup
- What is achalasia?
- A motility disorder characterized by failure of lower esophageal sphincter (LES) relaxation and loss of esophageal peristalsis
- What causes the LES dysfunction seen in primary achalasia?
- Degeneration of inhibitory neurons in the myenteric (Auerbach) plexus of the esophagus
- What are the hallmark esophageal manometry findings in achalasia?
- Increased LES resting pressure, incomplete LES relaxation with swallowing, and aperistalsis of the esophageal body
- What barium swallow finding is classic for achalasia?
- A 'bird-beak' (or 'rat-tail') tapering of the distal esophagus with proximal dilation
- What infectious disease can cause secondary achalasia?
- Chagas disease, caused by Trypanosoma cruzi
- Long-standing achalasia increases risk for which esophageal cancer?
- Squamous cell carcinoma of the esophagus
- What are the main treatment options for achalasia?
- Pneumatic dilation, surgical Heller myotomy, or botulinum toxin injection into the LES
- What is pseudoachalasia?
- A condition mimicking achalasia on manometry/imaging that is actually caused by malignancy infiltrating the gastroesophageal junction