Gastrointestinal (Digestive) Disorders

How the digestive system works

Food travels from the mouth through the esophagus to the stomach, where acid and enzymes begin digestion. The small intestine absorbs most nutrients with help from bile (made by the liver and stored in the gallbladder) and pancreatic enzymes. The large intestine (colon) absorbs water and forms stool, which leaves through the rectum and anus. Nerves, hormones and gut bacteria coordinate all of this, and the gut and brain communicate constantly.

Functional vs structural disorders

Common gastrointestinal disorders

Upper GI tract

• GERD: acid reflux causing heartburn and regurgitation; can inflame the esophagus.
• Functional dyspepsia: upper abdominal discomfort and early fullness with normal tests.
• Gastritis and peptic ulcers: stomach lining inflammation or sores, mostly from H. pylori or NSAIDs; may bleed.
• Eosinophilic esophagitis: allergic inflammation causing food to stick.
• Gastroparesis: slow stomach emptying, often in diabetes.

Small intestine

• Celiac disease: immune reaction to gluten damaging the small bowel; diarrhea, bloating, anemia, weight loss.
• Lactose intolerance: bloating and diarrhea after dairy.
• Small intestinal bacterial overgrowth (SIBO).

Large intestine and rectum

• Irritable bowel syndrome: recurrent abdominal pain with altered bowel habits; affects about 1 in 10 people.
• Inflammatory bowel disease: Crohn's disease and ulcerative colitis; chronic inflammation causing diarrhea, bleeding, pain and weight loss.
• Diverticular disease and diverticulitis: pouches in the colon wall that can become inflamed.
• Constipation and hemorrhoids.
• Colorectal polyps and colorectal cancer.
• Infections: gastroenteritis from viruses, bacteria and parasites; C. difficile after antibiotics.

Liver, gallbladder and pancreas

• Gallstones and gallbladder inflammation.
• Fatty liver disease, hepatitis and cirrhosis.
• Pancreatitis and pancreatic cancer.

Common symptoms and what they suggest

Diagnosis

Doctors start with a history and examination, then choose tests based on symptoms:

• Blood tests: blood count, iron studies, liver and kidney function, celiac antibodies, inflammatory markers
• Stool tests: infections, H. pylori, calprotectin (gut inflammation), hidden blood
• Breath tests: H. pylori, lactose intolerance, SIBO
• Imaging: ultrasound, CT, MRI
• Upper endoscopy and colonoscopy: a camera to view the lining and take biopsies
• Specialized tests: pH monitoring for reflux, manometry for motility, capsule endoscopy

Treatment

• Diet changes: more fiber, reducing trigger foods, a gluten-free diet for celiac disease, a low-FODMAP diet for IBS with dietitian guidance.
• Lifestyle: regular meals, weight management, exercise, limiting alcohol, stopping smoking, managing stress.
• Medicines: acid reducers, antibiotics for H. pylori, laxatives or antidiarrheals, antispasmodics, gut-brain neuromodulators, anti-inflammatory and biologic drugs for IBD.
• Psychological therapies: cognitive behavioral therapy and gut-directed hypnotherapy are effective for IBS and functional dyspepsia.
• Procedures: removing polyps, treating bleeding, stretching strictures, removing gallstones from bile ducts.
• Surgery: gallbladder removal, bowel resection, anti-reflux surgery, cancer surgery.

Prevention

• Eat a fiber-rich diet with plenty of vegetables, fruit, whole grains and legumes.
• Stay hydrated and physically active.
• Limit alcohol, red and processed meat, and avoid smoking.
• Use NSAIDs cautiously.
• Get vaccinated against hepatitis A and B.
• Start colorectal cancer screening at 45 if you are at average risk, earlier with family history.

Frequently asked questions

What are the most common gastrointestinal disorders?

The most common are GERD (acid reflux), irritable bowel syndrome, constipation, functional dyspepsia, hemorrhoids, gallstones, gastroenteritis, diverticular disease and lactose intolerance. Inflammatory bowel disease, celiac disease and peptic ulcers are less common but important.

What is the difference between IBS and IBD?

IBS is a functional disorder: the gut looks normal on tests, but it is more sensitive and moves differently, causing pain and altered bowel habits. IBD, which includes Crohn's disease and ulcerative colitis, involves visible inflammation that damages the bowel and can cause bleeding and weight loss.

When should I see a doctor about digestive symptoms?

See a doctor if you have bleeding, black stools, unintended weight loss, difficulty swallowing, persistent vomiting, anemia, a change in bowel habit lasting more than 3 weeks, or new symptoms after age 45 to 50. Sudden severe pain needs emergency care.

Can stress cause digestive problems?

Yes. The gut and brain are closely linked, and stress can trigger or worsen IBS, indigestion, nausea and changes in bowel habit. Stress does not cause ulcers or IBD directly, but it can worsen symptoms. Stress management and psychological therapies help many gut disorders.

How are digestive disorders diagnosed?

Diagnosis begins with a history and exam, then blood, stool and breath tests. Imaging such as ultrasound or CT, and endoscopy or colonoscopy with biopsies, are used to look directly at the digestive tract. Many functional disorders are diagnosed from symptom patterns after ruling out other causes.