Gastroenterologists use a wide range of tests to examine every part of your digestive tract, from the esophagus to the rectum. Some involve a camera on a flexible tube, others rely on imaging, breath samples, or stool analysis. The specific tests your doctor orders depend on your symptoms, but here’s what each one involves and what it’s looking for.
Upper Endoscopy
An upper endoscopy (also called an EGD) is one of the most common procedures in gastroenterology. A thin, flexible tube with a camera is guided through your mouth into the esophagus, stomach, and the first part of the small intestine. The whole thing typically takes 5 to 10 minutes under sedation.
Your gastroenterologist may recommend an upper endoscopy for persistent heartburn that hasn’t responded to medication, difficulty swallowing, unexplained upper abdominal pain (especially with weight loss), chronic vomiting, or iron deficiency anemia when the source appears to be in the upper digestive tract. It’s also the primary way to evaluate peptic ulcers, celiac disease, esophageal strictures, and Barrett’s esophagus, a precancerous change in the esophageal lining. During the procedure, the doctor can take small tissue samples for biopsy, which are sent to a lab for closer analysis.
Colonoscopy and Sigmoidoscopy
A colonoscopy examines the entire large intestine using a similar camera-tipped tube inserted through the rectum. It’s the standard screening tool for colorectal cancer, generally recommended every 10 years for average-risk adults starting at age 45. Beyond screening, colonoscopies investigate symptoms like chronic diarrhea, rectal bleeding, unexplained abdominal pain, and signs of inflammatory bowel disease such as Crohn’s disease or ulcerative colitis. If the doctor spots polyps (small growths that can become cancerous), they can remove them during the procedure itself.
A sigmoidoscopy is a shorter version that only examines the rectum and the lower left portion of the colon. It takes less time, requires less preparation, and usually doesn’t need sedation. The tradeoff is that it can’t see the rest of the colon. If polyps or anything concerning are found during a sigmoidoscopy, you’ll typically need a full colonoscopy as a follow-up.
Colonoscopy Prep
Preparation is the part most people dread. You’ll need to follow a clear liquid diet for the full day before the procedure, with no solid food at all. You’ll also drink a bowel prep solution that clears out the colon so the camera has a clear view. You must stop all liquids four hours before the procedure. Your doctor will also let you know which medications to pause beforehand.
Capsule Endoscopy
The small intestine sits between the stomach and the colon, and it’s too long and winding for a standard scope to reach. Capsule endoscopy solves this problem. You swallow a pill-sized camera that travels through your entire digestive tract over several hours, taking thousands of images along the way. A sensor worn on your body records the images, which your doctor reviews later.
Capsule endoscopy has been the gold standard for examining the small bowel since 2003. It’s painless and doesn’t require sedation. Doctors typically order it after a standard upper endoscopy and colonoscopy have come back normal but symptoms persist. Common reasons include obscure gastrointestinal bleeding suspected to originate in the small bowel, evaluation for Crohn’s disease when other imaging hasn’t provided answers, suspected small intestinal tumors, iron deficiency anemia with no identified source, and surveillance in patients with certain hereditary cancer syndromes. It’s not an option if you have a known bowel obstruction or stricture, since the capsule could get stuck.
Stool Tests
Not every gastroenterology test requires a procedure room. Stool tests are noninvasive and can reveal a lot about what’s happening inside your gut. Your doctor may order several types depending on your symptoms.
- Fecal calprotectin: This measures a protein released by white blood cells when there’s inflammation in the intestines. Elevated levels can help distinguish inflammatory bowel disease from irritable bowel syndrome, which doesn’t cause the same kind of measurable inflammation. It’s particularly useful because it can help your doctor decide whether you need a colonoscopy or whether your symptoms point to a functional issue.
- Fecal occult blood / FIT: These detect hidden blood in stool that isn’t visible to the naked eye. A positive result may indicate polyps, colorectal cancer, ulcers, or other sources of bleeding in the digestive tract.
- Stool cultures and parasite tests: When chronic diarrhea is the main symptom, your doctor may check for bacterial infections, parasites, or their eggs.
Breath Tests
Breath tests are simple, noninvasive, and done in the office. You drink a specific solution, then breathe into a collection device at timed intervals. The gas composition of your breath tells your doctor what’s happening in your gut.
The most common use is testing for small intestinal bacterial overgrowth (SIBO). After drinking a glucose and water mixture, a rapid rise in hydrogen or methane in your breath suggests that bacteria are fermenting the sugar in your small intestine, where they shouldn’t be in large numbers. A separate breath test using a urea solution can detect an active H. pylori infection, the bacterium responsible for most stomach ulcers. Breath tests for lactose or fructose intolerance work on a similar principle, measuring gas production after you consume those specific sugars.
Liver Elastography
If your gastroenterologist suspects liver disease, they may order a liver elastography scan, most commonly performed with a device called FibroScan. A probe placed against your skin sends painless pressure waves through the liver, and the speed of the resulting “shear wave” correlates with how stiff the liver tissue is. Stiffer tissue means more scarring (fibrosis).
This test examines roughly 100 times more liver volume than a traditional needle biopsy, and it carries none of the risks associated with puncturing the liver. It’s especially accurate at detecting advanced stages of fibrosis and cirrhosis. Gastroenterologists now use elastography routinely to monitor conditions like hepatitis B, hepatitis C, and nonalcoholic fatty liver disease, often reserving biopsy for cases where results are inconclusive or more detailed tissue analysis is needed.
ERCP and MRCP
These two tests focus on the bile ducts and pancreatic ducts, the small tubes that carry digestive fluids from the liver, gallbladder, and pancreas into the intestine.
MRCP is a specialized MRI scan. It produces detailed images of the bile and pancreatic ducts without any instruments entering your body. There’s no sedation, no radiation, and no recovery time. It’s used primarily as a diagnostic tool to look for blockages like gallstones stuck in a duct, narrowing, or tumors.
ERCP combines endoscopy with X-ray imaging. A scope is passed through your mouth and into the small intestine, where dye is injected into the ducts so they show up on X-ray. The key advantage of ERCP is that it’s both diagnostic and therapeutic: if a gallstone is blocking a duct, the doctor can remove it during the same procedure. If a duct is narrowed, they can place a stent to open it. Because ERCP carries a complication rate of 5 to 6% for diagnostic use and up to 10% for therapeutic procedures, doctors generally reserve it for situations where treatment is likely needed, using MRCP first when they just need a picture.
Motility Testing
Motility tests measure how well the muscles of your digestive tract squeeze and relax. They’re used when symptoms suggest a coordination problem rather than a structural one.
Esophageal manometry involves a thin, pressure-sensing tube passed through the nose and into the esophagus. As you swallow sips of water, the sensors record how your esophageal muscles contract and whether the valve between your esophagus and stomach opens and closes properly. This test is essential for diagnosing swallowing disorders and is often required before anti-reflux surgery.
Anorectal manometry uses a similar pressure-sensing approach in the rectum and anal canal. It measures the strength and coordination of the muscles involved in bowel movements, including how your sphincter muscles contract, how your rectum senses fullness, and whether you can effectively bear down during a simulated evacuation. Doctors order this test for chronic constipation, fecal incontinence, or when they suspect a pelvic floor coordination problem. During the test, a small balloon is gradually inflated inside the rectum in increments until you report sensations of fullness, urgency, and maximum tolerance.
Gastric Emptying Study
If your doctor suspects gastroparesis, a condition where the stomach empties too slowly, the main diagnostic test is a gastric emptying study. You eat a light meal (typically eggs and toast) that contains a tiny amount of radioactive tracer. A scanner positioned over your abdomen then tracks how quickly the food moves out of your stomach over the course of about four hours. The rate of emptying is compared to established normal values, and significant delays confirm the diagnosis. You’ll need to stop any medications that could affect stomach motility before the test, so your doctor will give you a specific list of what to hold.