Reflux: What Could Be Causing It?

What Reflux Actually Is

Reflux describes the retrograde movement of gastric acid, pepsin, and sometimes bile from the stomach into the esophagus. The lower esophageal sphincter (LES), a ring of smooth muscle at the gastroesophageal junction, normally prevents this backflow. When the LES relaxes at the wrong time or cannot maintain adequate pressure, acidic contents contact esophageal mucosa and produce the burning sensation known as heartburn [1].

The Role of Transient LES Relaxations

The dominant mechanism behind most reflux episodes is the transient lower esophageal sphincter relaxation (TLESR). Unlike swallow-induced relaxation, TLESRs are vagally mediated events that occur independently of swallowing. A study published in Gastroenterology found that TLESRs account for up to 70% of reflux events in GERD patients and virtually all reflux episodes in healthy subjects [2]. Gastric distension from large meals or carbonated beverages is one of the strongest physiological triggers for TLESRs.

Reflux vs. GERD

Not all reflux is GERD. Physiological reflux happens in everyone, typically after meals, and resolves without symptoms. GERD is diagnosed when reflux causes troublesome symptoms or complications. The 2006 Montreal Definition, endorsed by the American Gastroenterological Association (AGA), classifies GERD as "a condition which develops when the reflux of stomach contents causes troublesome symptoms and/or complications" [3]. The distinction matters because treatment intensity and the need for diagnostic workup differ considerably.

Common Causes of Reflux

Multiple conditions produce or worsen reflux symptoms. Some are structural, some are functional, and some are entirely modifiable.

Hiatal Hernia

A hiatal hernia occurs when the proximal stomach herniates through the diaphragmatic hiatus into the thoracic cavity. This displacement separates the LES from the crural diaphragm, removing an important anti-reflux barrier. Endoscopic studies show that hiatal hernias are present in over 90% of patients with severe erosive esophagitis [4]. Small hernias (<2 cm) may cause no symptoms at all, while larger hernias strongly correlate with increased acid exposure time.

Obesity and Central Adiposity

Excess abdominal fat raises intragastric pressure and disrupts the gastroesophageal junction. A meta-analysis of 20 studies (N=18,346) published in Annals of Internal Medicine demonstrated that a BMI ≥30 was associated with a 2.5-fold increase in GERD symptoms and a 2.8-fold increase in erosive esophagitis compared to normal-weight individuals [5]. Even modest weight gain of 5 to 10 kg increases symptom frequency. Central adiposity appears to be the stronger predictor, regardless of total body weight.

Medication-Induced Reflux

Several drug classes lower LES pressure or directly irritate the esophageal mucosa. NSAIDs, bisphosphonates (particularly oral alendronate), calcium channel blockers, anticholinergics, benzodiazepines, and progesterone all reduce LES tone [6]. Tetracycline and potassium chloride tablets can cause direct mucosal injury if they lodge in the esophagus during transit. The American College of Gastroenterology (ACG) 2022 guidelines recommend reviewing the medication list in every patient presenting with new reflux symptoms [7].

Dietary and Behavioral Triggers

Certain foods relax the LES or stimulate acid secretion. Coffee, chocolate, alcohol, peppermint, and high-fat meals are the most frequently cited dietary triggers in clinical practice [7]. Late evening meals (eating within 2 to 3 hours of lying down) prolong supine acid exposure. A randomized crossover trial in the American Journal of Gastroenterology showed that a 6-hour dinner-to-bed interval reduced nocturnal reflux episodes by 45% compared to a 2-hour interval [8].

Delayed Gastric Emptying (Gastroparesis)

When the stomach empties slowly, retained food and acid increase gastric volume and intragastric pressure, promoting reflux. Up to 40% of patients with refractory GERD symptoms have documented delayed gastric emptying on scintigraphy [9]. Diabetes mellitus, post-surgical vagal injury, and idiopathic gastroparesis are common underlying etiologies. Treating the motility disorder often reduces reflux burden more effectively than escalating acid suppression alone.

Pregnancy

Reflux affects 40 to 85% of pregnant women, particularly in the second and third trimesters [10]. Progesterone relaxes the LES while the enlarging uterus increases abdominal pressure. Symptoms typically resolve within weeks after delivery. The ACG recommends lifestyle modifications first, followed by antacids or sucralfate, with PPIs reserved for refractory cases after risk-benefit discussion [7].

Less Common but Important Causes

Eosinophilic Esophagitis (EoE)

EoE is an immune-mediated condition characterized by eosinophilic infiltration of the esophageal mucosa. It mimics GERD with heartburn and dysphagia but does not respond to standard acid suppression. Diagnosis requires esophageal biopsies showing ≥15 eosinophils per high-power field [11]. EoE prevalence has risen sharply; a 2023 meta-analysis in Clinical Gastroenterology and Hepatology estimated 34.4 cases per 100,000 in the U.S. [11]. Distinguishing EoE from GERD is critical because treatment differs (dietary elimination or topical corticosteroids vs. PPIs).

Esophageal Motility Disorders

Conditions such as achalasia, ineffective esophageal motility, and distal esophageal spasm impair clearance of refluxed material from the esophagus. A patient with normal acid exposure but prolonged mucosal contact time may still develop symptoms and tissue damage. High-resolution manometry is the diagnostic standard for these disorders [12].

Functional Heartburn

Some patients report typical reflux symptoms despite normal acid exposure, normal endoscopy, and no symptom-reflux correlation on pH-impedance testing. The Rome IV criteria classify this as functional heartburn, a disorder of gut-brain interaction [13]. This diagnosis should be made only after GERD and EoE have been excluded. Treatment often involves neuromodulators such as low-dose tricyclic antidepressants rather than continued acid suppression.

Zollinger-Ellison Syndrome

This rare condition involves gastrin-secreting tumors (gastrinomas) that cause massive acid hypersecretion. Fasting serum gastrin levels exceeding 1,000 pg/mL in the setting of a gastric pH <2 are strongly suggestive [14]. Patients typically present with severe, refractory reflux and peptic ulcers in unusual locations (distal duodenum or jejunum).

How Reflux Is Diagnosed

Clinical History and Empiric PPI Trial

The ACG 2022 guidelines recommend starting with a clinical assessment. Typical symptoms (heartburn and regurgitation) that respond to an empiric 8-week PPI trial are considered diagnostic of GERD in most patients [7]. No additional testing is needed if symptoms resolve and no alarm features are present.

Upper Endoscopy (EGD)

Endoscopy is indicated when alarm symptoms are present (dysphagia, odynophagia, weight loss, anemia, or GI bleeding), when symptoms are refractory to PPI therapy, or for Barrett esophagus screening in high-risk patients [7]. The Los Angeles classification grades erosive esophagitis from A (mild) to D (severe). A normal endoscopy does not rule out GERD; approximately 50 to 70% of patients with PPI-responsive symptoms have non-erosive reflux disease (NERD) on endoscopy [15].

Ambulatory pH and pH-Impedance Monitoring

The 24-hour pH-impedance study is the gold standard for quantifying esophageal acid exposure. It measures total acid exposure time, number of reflux episodes, and symptom-reflux correlation using the symptom index (SI) and symptom association probability (SAP). The ACG recommends performing this test off PPI therapy for patients with a normal endoscopy and ongoing symptoms, and on PPI therapy for patients with persistent symptoms despite adequate dosing [7].

High-Resolution Manometry

Manometry does not diagnose GERD directly but is required before anti-reflux surgery to exclude achalasia or severe hypomotility, which are contraindications to standard fundoplication [12]. It also identifies weak LES pressure that may contribute to the reflux mechanism.

Treatment: Matching the Intervention to the Cause

Lifestyle Modifications

Weight loss is the single most evidence-supported lifestyle intervention. A prospective cohort study in The New England Journal of Medicine (N=10,545) found that a BMI reduction of ≥3.5 units decreased the odds of frequent reflux symptoms by 40% [16]. Head-of-bed elevation (15 to 20 cm using a wedge or bed risers) reduces supine acid exposure, particularly for nocturnal symptoms. Avoidance of trigger foods, cessation of smoking, and a minimum 3-hour post-meal interval before reclining are recommended by both the ACG and AGA [7].

Pharmacotherapy

PPIs remain first-line pharmacotherapy for GERD. A Cochrane review of 134 trials showed that PPIs resolve esophagitis in 78% of patients at 8 weeks and provide symptom relief in 57 to 72% of NERD patients [17]. Standard-dose options include omeprazole 20 mg, esomeprazole 20 to 40 mg, and lansoprazole 30 mg once daily before a meal. The ACG recommends the lowest effective dose and advises stepping down to H2 receptor antagonists (famotidine 20 to 40 mg) or on-demand PPI use for long-term management when possible [7].

For patients concerned about long-term PPI use: the 2024 AGA Clinical Practice Update noted that the absolute risk increases for commonly cited harms (kidney disease, bone fractures, dementia) are small and often confounded, and PPIs should not be withheld when clearly indicated [18].

Surgical and Endoscopic Options

Anti-reflux surgery (laparoscopic Nissen fundoplication or magnetic sphincter augmentation with the LINX device) is appropriate for patients with objectively confirmed GERD who prefer not to take lifelong medication, who have large hiatal hernias, or who have refractory symptoms despite optimized PPI therapy [7]. A five-year follow-up study of the LINX device (N=100) demonstrated that 85% of patients achieved ≥50% reduction in PPI use, with a mean esophageal acid exposure time within normal limits [19].

Transoral incisionless fundoplication (TIF) offers a less invasive endoscopic alternative, though long-term durability data remain limited.

When to Worry: Alarm Features and Complications

Red Flags That Require Prompt Evaluation

Seek medical evaluation within days (not weeks) for any of the following: difficulty swallowing solid foods, painful swallowing, unintentional weight loss of ≥5% body weight, vomiting blood or coffee-ground material, black tarry stools, or new-onset reflux after age 60 [7]. These findings raise concern for esophageal stricture, Barrett esophagus, or esophageal malignancy.

Barrett Esophagus

Chronic acid exposure can cause intestinal metaplasia in the distal esophagus, a precancerous change called Barrett esophagus. Barrett develops in an estimated 5 to 15% of chronic GERD patients [20]. Risk factors for progression to esophageal adenocarcinoma include long-segment Barrett (≥3 cm), male sex, central obesity, smoking, and family history. The ACG recommends screening endoscopy for patients with chronic GERD and three or more risk factors, followed by surveillance every 3 to 5 years if non-dysplastic Barrett is confirmed [20].

Extraesophageal Manifestations

Reflux may present atypically with chronic cough, laryngitis, dental erosions, or asthma exacerbations. The evidence linking reflux to these symptoms is less strong than for typical GERD. The ACG cautions against attributing extraesophageal symptoms to reflux without first confirming acid exposure with pH-impedance monitoring, as empiric PPI trials for suspected extraesophageal reflux have a high placebo response rate [7].

Reflux in Specific Populations

Older adults may experience less heartburn despite greater acid exposure, because age-related changes reduce esophageal sensitivity. This "silent reflux" pattern increases the risk of complications detected only at endoscopy. In patients on chronic NSAIDs or anticoagulants, even mild esophagitis carries a higher bleeding risk, making accurate diagnosis particularly important [6].

Patients taking GLP-1 receptor agonists for weight management may notice initial worsening of reflux due to delayed gastric emptying, a known pharmacological effect of the drug class [21]. This typically improves as dosing stabilizes, though clinicians should monitor symptoms closely during titration.