Gastrointestinal disorders span the entire alimentary tract from the esophagus to the anus, as well as the hepatobiliary system and pancreas. They account for substantial morbidity, healthcare utilization, and economic burden. Advances in endoscopy, imaging, and biologic therapies have transformed the management of many GI diseases.
Esophageal Disorders
Gastroesophageal Reflux Disease
GERD occurs when reflux of gastric contents into the esophagus causes troublesome symptoms or complications. The lower esophageal sphincter (LES) — a tonic high-pressure zone at the gastroesophageal junction — is the primary antireflux barrier. Transient LES relaxations, hypotensive LES, hiatal hernia, and impaired esophageal clearance contribute to reflux.
Clinical presentation. Heartburn (retrosternal burning), regurgitation, and dysphagia are typical. Atypical manifestations include chronic cough, asthma, laryngitis, and non-cardiac chest pain. Alarm features (dysphagia, odynophagia, weight loss, anemia, hematemesis) warrant urgent endoscopy.
Diagnosis and treatment. Typical symptoms without alarm features can be managed empirically with acid suppression. Proton pump inhibitors (omeprazole, pantoprazole, esomeprazole) are first-line therapy. Diagnostic testing (upper endoscopy, ambulatory pH monitoring, esophageal manometry) is reserved for refractory symptoms, atypical presentations, or pre-operative evaluation. Complications include erosive esophagitis, strictures, Barrett esophagus (intestinal metaplasia of the distal esophagus, a precursor to esophageal adenocarcinoma), and aspiration.
Esophageal Motility Disorders
Achalasia. Impaired LES relaxation and absent esophageal peristalsis due to loss of inhibitory neurons in the myenteric plexus. Presents with progressive dysphagia to solids and liquids, regurgitation, and weight loss. Diagnosis by esophageal manometry (Chicago Classification). Treatment includes pneumatic dilation, laparoscopic Heller myotomy with partial fundoplication, and peroral endoscopic myotomy (POEM).
Gastroduodenal Disorders
Peptic Ulcer Disease
PUD encompasses gastric and duodenal ulcers resulting from disruption of the mucosal barrier. The two dominant causes are Helicobacter pylori infection and non-steroidal anti-inflammatory drug (NSAID) use. Gastric acid and pepsin contribute to ulcer formation.
Helicobacter pylori. A Gram-negative bacterium that colonizes the gastric mucosa, causing chronic gastritis in all infected individuals. It is the strongest risk factor for peptic ulcer disease and gastric adenocarcinoma. Diagnosis by stool antigen test, urea breath test, or endoscopic biopsy. Treatment with triple or quadruple therapy (PPI + clarithromycin + amoxicillin or metronidazole; or PPI + bismuth + tetracycline + metronidazole) for 14 days.
Clinical presentation. Epigastric pain (relieved by food in duodenal ulcers, worsened by food in gastric ulcers), bloating, nausea, and early satiety. Complications include bleeding (hematemesis, melena), perforation, penetration, and gastric outlet obstruction.
Management. Acid suppression with PPI, eradication of H. pylori, and discontinuation of NSAIDs. Emergency endoscopy for bleeding ulcers with injection, cautery, or clip application. Surgery (vagotomy, antrectomy) is reserved for refractory bleeding or perforation.
Inflammatory Bowel Disease
IBD comprises two chronic, relapsing inflammatory conditions of the gastrointestinal tract: Crohn disease and ulcerative colitis.
Crohn Disease
Crohn disease can affect any part of the GI tract from mouth to anus, with discontinuous transmural inflammation. Skip lesions, fistulas, abscesses, and strictures are characteristic. Inflammation is driven by dysregulated immune responses to gut microbiota in genetically susceptible individuals.
Clinical features. Chronic diarrhea, abdominal pain (typically right lower quadrant), weight loss, and fatigue. Perianal disease (fistulas, fissures, abscesses) occurs in 25–30%. Extraintestinal manifestations include arthritis, uveitis, erythema nodosum, pyoderma gangrenosum, and primary sclerosing cholangitis.
Diagnosis. Ileocolonoscopy with biopsies reveals patchy inflammation, cobblestone mucosa, and deep ulcers. Cross-sectional imaging (CT enterography, MR enterography) evaluates small bowel disease and extraenteric complications.
Treatment. Aminosalicylates, corticosteroids (for acute flares), immunomodulators (azathioprine, 6-MP, methotrexate), and biologic therapies (anti-TNF: infliximab, adalimumab; anti-integrin: vedolizumab; anti-IL-12/23: ustekinumab). Surgical resection is required for complications (strictures, fistulas, abscesses) but is not curative.
Ulcerative Colitis
UC is a mucosal inflammation confined to the colon, extending continuously from the rectum proximally. It is characterized by bloody diarrhea, urgency, and tenesmus.
Treatment. 5-ASA compounds (mesalamine) are first-line for mild to moderate disease. Corticosteroids for acute flares. Immunomodulators and biologics (similar to Crohn) for moderate to severe disease. Total proctocolectomy with ileal pouch-anal anastomosis (IPAA) is curative for refractory disease.
Irritable Bowel Syndrome
IBS is a disorder of gut-brain interaction characterized by recurrent abdominal pain related to defecation, associated with altered stool frequency or form. Rome IV criteria are used for diagnosis. Pathophysiology involves visceral hypersensitivity, altered motility, gut microbiome alterations, and psychosocial factors. Subtypes: IBS-C (constipation-predominant), IBS-D (diarrhea-predominant), IBS-M (mixed). Treatment is symptom-directed: fiber, osmotic laxatives, lubiprostone, linaclotide for constipation; loperamide, rifaximin, eluxadoline for diarrhea; low-FODMAP diet; gut-directed hypnotherapy; tricyclic antidepressants for global symptoms.
Liver Diseases
Hepatitis
Viral hepatitis. Hepatitis A (fecal-oral, self-limited), hepatitis B (bloodborne, sexual, vertical), hepatitis C (bloodborne), hepatitis D (requires HBV), and hepatitis E (fecal-oral). HBV and HCV cause chronic hepatitis, cirrhosis, and hepatocellular carcinoma. HBV is preventable by vaccination. HCV is curable with DAAs.
Alcoholic hepatitis. Acute-on-chronic liver inflammation due to heavy alcohol use. Severe alcoholic hepatitis (Maddrey discriminant function ≥32) is treated with corticosteroids or pentoxifylline.
Metabolic dysfunction-associated steatohepatitis (MASH). Formerly NASH, MASH is the hepatic manifestation of metabolic syndrome and the fastest-growing cause of liver disease worldwide. It ranges from simple steatosis to steatohepatitis with fibrosis, cirrhosis, and HCC. Lifestyle intervention is cornerstone. Resmetirom, a thyroid hormone receptor-beta agonist, is the first FDA-approved pharmacotherapy.
Cirrhosis
Cirrhosis is the end-stage of chronic liver disease, characterized by fibrosis and nodular regeneration. Portal hypertension leads to varices, ascites, spontaneous bacterial peritonitis, hepatorenal syndrome, and hepatic encephalopathy. The Child-Pugh and MELD scores assess severity and guide transplantation. Complications are managed with beta-blockers (variceal prophylaxis), diuretics (ascites), lactulose and rifaximin (encephalopathy), and terlipressin (hepatorenal syndrome). Liver transplantation is definitive therapy for decompensated cirrhosis.
Gallbladder and Pancreatic Disorders
Cholelithiasis (gallstones). Cholesterol or pigment stones in the gallbladder. Most are asymptomatic. Complications include biliary colic, acute cholecystitis, choledocholithiasis, and gallstone pancreatitis. Laparoscopic cholecystectomy is definitive treatment.
Acute pancreatitis. Inflammatory condition of the pancreas with autodigestion by prematurely activated pancreatic enzymes. Gallstones and alcohol are the most common causes. The revised Atlanta Classification defines severity (interstitial edematous vs necrotizing pancreatitis). Management includes aggressive fluid resuscitation, pain control, and enteral nutrition. Necrotizing pancreatitis requires ICU care, and infected necrosis may require necrosectomy.
Gastrointestinal Malignancies
Esophageal cancer. Squamous cell carcinoma (upper and middle esophagus) and adenocarcinoma (distal esophagus, associated with GERD/Barrett esophagus). Poor prognosis due to late presentation.
Gastric cancer. Adenocarcinoma is the second most common cause of cancer death globally. Risk factors include H. pylori infection, diet, smoking, and pernicious anemia.
Colorectal cancer. Third most common cancer worldwide. Screening with colonoscopy, FIT, or multitarget stool DNA reduces mortality.
Pancreatic cancer. Highly lethal; 5-year survival <12%. Most present with advanced disease. See article 03 for detailed discussion.
Summary
Gastrointestinal disorders encompass a wide spectrum from functional conditions (IBS, GERD) to inflammatory diseases (IBD, celiac) to life-threatening malignancies. H. pylori eradication has dramatically reduced peptic ulcer disease. Biologic therapies have transformed the management of IBD. Liver disease, particularly MASH, is increasing in prevalence. Endoscopy is central to diagnosis and treatment across the GI tract. The integration of gastroenterology, hepatology, surgery, and oncology is essential for comprehensive care.