Show notes
GERD 1: Pathogenesis — It's Not Just Acid BurnsEpisode keywords: GERD pathogenesis, cytokine-mediated esophageal injury, transient LES relaxation TLESR, GABA-B baclofen reflux, LES pressure GERD, nucleus tractus solitarius reflux, ACG GERD definition 2022Episode SummaryThe "acid burn" model of reflux esophagitis has been replaced. This episode covers the Dunbar JAMA 2016 paradigm shift showing that acid triggers a cytokine-mediated inflammatory response that builds from deep to superficial, not from the surface inward. It then establishes the two-component antireflux barrier, the neural control of transient LES relaxations, and one of the most consistently board-tested misconceptions: that most GERD patients have normal resting LES pressure.Key TopicsACG 2022 GERD definition: Reflux of stomach contents causing troublesome symptoms and/or complications, objectively documented by endoscopy or ambulatory pH monitoring. Approximately 20% of Western adults report weekly heartburn.The cytokine-mediated injury model: Acid contacts esophageal epithelial cells, which secrete pro-inflammatory cytokines that recruit T lymphocytes. The damage is inflammatory, not chemical. Histologic consequence: basal cell hyperplasia and elongated papillae appear before surface erosions. Injury builds from inside out. This explains why symptom severity does not correlate with endoscopic severity.The two-component LES: The intrinsic LES is smooth muscle providing tonic contraction. The extrinsic LES is the crural diaphragm, skeletal muscle that dynamically augments pressure during inspiration and straining. Both components must be understood to explain hiatal hernia and fundoplication mechanics.TLESRs as the dominant reflux mechanism: Transient LES relaxations are sudden, prolonged relaxations not triggered by swallowing, lasting more than 10 seconds, representing the normal belch reflex. Controlled by the nucleus tractus solitarius in the medulla. Inhibited by GABA-B neurons, which is why baclofen (a GABA-B agonist) reduces TLESR frequency. CCK-1 receptors mediate intrinsic sphincter relaxation during TLESRs, connecting fatty meals to reflux through a defined pathway.The TLESR misconception: GERD patients do not have more TLESRs than normal people. The frequency is the same. What differs is that a higher proportion of TLESRs in GERD are associated with acid reflux rather than just gas venting. The problem is content, not frequency.LES pressure in GERD: Most GERD patients have normal resting LES pressure. Only patients with severe erosive esophagitis consistently have abnormally low LES pressure, generally below 10 mmHg. GERD is not simply a "weak sphincter" disease for the majority of patients.Board PearlsHigh-yield: The Dunbar model means histologic changes precede endoscopic findings. Basal cell hyperplasia and T-cell infiltration on biopsy can represent early reflux injury even with a normal-looking mucosal surface.Board trap: A question states a GERD patient has normal LES pressure and asks if this rules out GERD. It does not. Normal resting LES pressure is the expected finding in most reflux patients.High-yield: Baclofen reduces TLESRs via GABA-B agonism at the nucleus tractus solitarius. This is a high-frequency board mechanism question.GERD 2: The Antireflux Barrier, Clearance, and Hiatal HerniaEpisode keywords: antireflux barrier, hiatal hernia reflux mechanism, esophageal clearance GERD, nocturnal acid reflux, H. pylori Barrett's inverse association, obesity GERD mechanism, IEM reflux esophagitis, angle of His flap valveEpisode SummaryThe antireflux barrier has three components, esophageal clearance has four mechanisms, and hiatal hernia disrupts all of them simultaneously. This episode builds on the pathophysiology of Episode 1 to explain why hiatal hernia size correlates with reflux severity, why nighttime reflux is more injurious than daytime reflux, and two systemic factors that modify GERD risk through mechanisms boards specifically test: H. pylori and obesity.Key TopicsThree components of the antireflux barrier: The LES smooth muscle provides tonic pressure. The EGJ flap valve (angle of His) creates a geometric one-way valve that tightens when the fundus distends. The crural diaphragm provides skeletal muscle augmentation during inspiration and straining. All three can fail independently or together.Hill classification and AFS grading: The flap valve is graded endoscopically. Hill Grade I is a prominent fold closely approximating the scope. Hill Grade IV is no fold at all, a gaping hiatus. AFS Grade 1 indicates all components intact; higher grades indicate progressive failure.Four esophageal clearance mechanisms: Gravity, peristalsis, salivation, and submucosal gland bicarbonate secretion. During sleep, three of the four are eliminated simultaneously: the supine position removes gravity, swallowing frequency drops to near zero eliminating peristalsis, and salivation stops. Only submucosal secretion persists. This is why nocturnal reflux is disproportionately injurious.IEM and reflux esophagitis: Between 25 and 48% of reflux esophagitis patients have ineffective esophageal motility. IEM impairs clearance and is a risk factor for more severe disease. It is also the primary reason manometry is required before antireflux surgery. A weak esophagus wrapped with a 360-degree Nissen cannot generate sufficient peristaltic force and develops dysphagia.Hiatal hernia mechanics: Hernia separates the intrinsic LES from the crural diaphragm, displacing the LES into the negative-pressure thorax. The crura now squeeze around the stomach below the herniated segment, creating a reservoir that readily refluxes. Fundal distention of the herniated segment increases TLESR frequency. The angle of His widens as the hernia enlarges, destroying the flap valve. All three antireflux components fail simultaneously. Hernia size correlates with reflux severity.H. pylori and the inverse association: H. pylori causing predominantly corpus (fundic) gastritis leads to parietal cell atrophy and reduced acid production. Less acid means less esophageal injury. This creates an inverse association between H. pylori, Barrett's esophagus, and esophageal adenocarcinoma. Clinical policy: GI societies do NOT recommend routine H. pylori testing and treatment in GERD patients. GERD is NOT a contraindication to treating H. pylori when another indication exists. Do not withhold treatment for peptic ulcer disease because a patient has reflux.Obesity and GERD: Dose-dependent positive association with BMI. Visceral adipose tissue increases intragastric pressure, promotes hiatal hernia formation, and secretes adipokines that directly impair esophageal barrier integrity and dilate intercellular spaces. Obesity is also an independent risk factor for Barrett's and esophageal adenocarcinoma beyond its effect on reflux volume.Board PearlsBoard trap: A patient with GERD has incidentally found H. pylori. Does treating the infection worsen reflux? Treat the H. pylori if an indication exists. Manage GERD on its own merits. Do not withhold treatment.High-yield: Nocturnal reflux is more injurious because three of four clearance ...