Endoscopy: What It Shows, What It Cannot, and How to Prepare

Key takeaways

• Endoscopy is a direct-vision test: it shows the inner lining of an organ, not what lies beneath or behind it.
• Endoscopy is both diagnostic and therapeutic: biopsies, polyp removal, bleeding control and stent placement are all possible during the same session.
• "Endoscopy" is a family of procedures, not one test; gastroscopy, colonoscopy, bronchoscopy, cystoscopy and ERCP carry different preparations and different risk profiles.
• A normal endoscopy does not exclude every disease: pancreatic, small-bowel and deep-wall disease can be missed and may need CT, MRI or capsule studies.
• Preparation is set by the performing unit: fasting times, bowel preparation and medicine adjustments differ between hospitals and between procedures.

At a glance

Also known as

• Endoscopy test, scopy: common usage in Indian hospitals
• Upper GI endoscopy / OGD / EGD / gastroscopy: the mouth-route examination of food pipe, stomach and duodenum
• Colonoscopy, sometimes called lower GI scopy
• Dooerbeen / camera test, pet ki camera jaanch: informal descriptions patients often use
• Sigmoidoscopy: limited examination of the left colon and rectum

What endoscopy is

An endoscope is a tube containing a light source, a camera chip or fibre-optic bundle, channels for air, water and suction, and a working channel through which instruments can be passed. The camera sends live images to a screen, so the doctor sees the mucosal surface magnified and illuminated.

Because instruments can pass down the working channel, endoscopy is often therapeutic as well as diagnostic. In the same sitting a doctor may take pinch biopsies, remove a polyp, clip a bleeding ulcer, band oesophageal varices, dilate a narrowing, place a stent or retrieve a swallowed object.

Endoscopy is not a single examination. The scope, the route, the preparation, the sedation and the risks all change with the organ being studied. A gastroscopy and an ERCP are performed with similar-looking equipment but are very different in complexity and in complication rate.

Why endoscopy is done

• Upper GI symptoms: persistent heartburn or indigestion not responding to treatment, difficulty or pain on swallowing, repeated vomiting, suspected ulcer disease, unexplained iron-deficiency anaemia.
• GI bleeding: vomiting blood, black tarry stools, or bleeding per rectum, both to find the source and to treat it.
• Lower GI symptoms: change in bowel habit, chronic diarrhoea, blood in stool, suspected inflammatory bowel disease, abnormal imaging of the colon.
• Cancer detection and surveillance: assessment of suspicious lesions, colon polyp removal, follow-up of Barrett's oesophagus, coeliac disease or previous polyps.
• Biliary and pancreatic disease: ERCP for bile duct stones, blocked ducts and jaundice needing drainage.
• Airway and urinary problems: bronchoscopy for persistent cough with abnormal chest imaging or coughing blood; cystoscopy for visible blood in urine or bladder symptoms.

Who should consider an endoscopy

Endoscopy is requested by a doctor after clinical assessment, it is not a walk-in screening test for everyone with an upset stomach. Referral is commonly considered for:

• Adults with difficulty swallowing, food sticking, or painful swallowing at any age.
• Adults with unintentional weight loss, persistent vomiting, or an abdominal mass alongside dyspepsia.
• Adults with iron-deficiency anaemia without an obvious cause.
• Adults with dyspepsia that persists despite an adequate trial of treatment, or that begins in later adult life.
• Anyone with visible or suspected GI bleeding.
• People with rectal bleeding, a persistent change in bowel habit, or a strong family history of colorectal cancer or polyps, colonoscopy rather than gastroscopy.
• People with known coeliac disease, Barrett's oesophagus, cirrhosis with varices, or previous polyps, on a surveillance interval set by their gastroenterologist.

Whether an endoscopy is the right next step, and which endoscopy, depends on the specific problem. Results vary depending on individual clinical circumstances.

What endoscopy cannot detect or exclude

Endoscopy is a surface examination. Its blind spots matter:

• It does not see through the wall. Tumour depth, lymph nodes and spread beyond the organ are not assessed by standard endoscopy; that needs endoscopic ultrasound (EUS), CT or MRI.
• Gastroscopy does not assess the pancreas, gallbladder, liver parenchyma or aorta. A normal gastroscopy does not exclude gallstone disease, pancreatitis or pancreatic cancer.
• Most of the small intestine is out of reach. Standard gastroscopy reaches the duodenum; colonoscopy reaches the last part of the ileum. Disease in between may need capsule endoscopy, enteroscopy or MR enterography.
• Colonoscopy is not perfect. Flat lesions, small polyps and lesions behind folds can be missed, particularly if the bowel preparation is poor or the caecum is not reached.
• Gastroscopy does not diagnose cardiac chest pain. Chest pain that could be cardiac needs cardiac assessment, not reassurance from a normal scopy.
• Functional disorders show nothing. Irritable bowel syndrome, functional dyspepsia and many motility problems produce a normal-looking lining. A normal report does not mean symptoms are imaginary.
• Biopsy sampling is selective. A negative biopsy means the tissue taken showed no abnormality; it does not prove the whole organ is normal.

A finding that is "not identified" at endoscopy has not been excluded. If symptoms continue or worsen despite a normal report, go back to your doctor rather than assuming nothing more can be wrong.

Related but different examinations

No single procedure is superior across the board. These tests answer different questions, and the right first test depends entirely on the presenting problem, bleeding, jaundice, cough and dysphagia each lead to a different starting point.

How to prepare

Preparation is operational and varies between hospitals, between endoscopists and between procedures. The written instruction sheet from the unit performing your procedure takes precedence over any general advice, including this page. General patterns:

• Fasting: solid food is usually stopped several hours before sedation, and clear fluids are stopped closer to the procedure. Exact times are set by the unit and the anaesthetist.
• Bowel preparation: required for colonoscopy and sigmoidoscopy. This involves a laxative solution, sometimes split into two doses, plus dietary restriction for a day or more before.
• Medicines: tell the team about every medicine and supplement, especially blood thinners, antiplatelet drugs, insulin and other diabetes medicines, iron tablets and acid-suppressing drugs. Do not start, stop or change any prescribed medicine on your own, ask the prescriber or the endoscopy team.
• Escort and transport: if sedation is planned, a responsible adult should accompany you home. Do not drive, ride a two-wheeler or operate machinery for the rest of that day.
• Consent and history: declare heart or lung disease, sleep apnoea, previous anaesthetic problems, allergies, pregnancy, artificial heart valves, implanted devices and previous abdominal surgery.

If you have diabetes on glucose-lowering treatment

Fasting and bowel preparation can cause low blood sugar. Insulin and sulfonylurea doses often need planned adjustment, and SGLT2 inhibitors may need temporary interruption before prolonged fasting. This must be arranged in advance with your prescriber, never adjusted by yourself.

If you have heart failure or advanced chronic kidney disease

Large-volume bowel preparations can cause fluid and electrolyte shifts. Tell the unit about heart failure, dialysis, advanced CKD, cirrhosis with ascites or any fluid restriction so an appropriate preparation and monitoring plan can be chosen.

If you are on blood thinners or antiplatelet drugs

Decisions balance bleeding risk during biopsy or polyp removal against clotting risk if the drug is paused, particularly with recent coronary stents, mechanical valves or atrial fibrillation. The plan is individual and must come from the prescriber together with the endoscopist.

If you are pregnant or breastfeeding

Endoscopy in pregnancy is done only when clearly needed, commonly for significant bleeding, and is planned jointly with the obstetric team. Sedation choice, positioning, timing in pregnancy and avoidance of radiation-based procedures such as ERCP where possible are all specifically considered.

Children

Paediatric endoscopy uses smaller scopes, paediatric-specific fasting rules and usually general anaesthesia or deep sedation with a paediatric anaesthetist. Weight-based bowel preparation regimens differ from adult ones and must be prescribed by the paediatric team.

Older adults

Sedation is often given in reduced doses, and frailty, dehydration risk during bowel preparation and interacting medicines need review before the procedure.

What happens during endoscopy

• Check-in: identity, consent, fasting status and medicines are confirmed. A cannula is placed for sedation, and monitoring of pulse, blood pressure and oxygen is attached.
• Numbing or sedation: for gastroscopy a local anaesthetic throat spray may be used, with or without intravenous sedation. Colonoscopy is usually done under sedation. Some procedures need general anaesthesia.
• Passing the scope: you lie on your left side for GI endoscopy. A mouthguard protects the teeth for gastroscopy. Air or carbon dioxide is used to open the lumen, which can cause bloating or an urge to belch or pass wind, this is expected.
• Examination and treatment: the endoscopist inspects systematically, photographs findings and takes biopsies if needed. Biopsy itself is not painful, as the lining has no pain nerve endings of that kind.
• Recovery: you rest in a recovery area until alert. You may be offered fluids once the throat spray has worn off and swallowing is safe.
• Discharge: the endoscopist usually explains visual findings the same day and gives a written report. Biopsy results follow separately.

How long the process takes

• Diagnostic gastroscopy: commonly about 5-15 minutes of scope time.
• Diagnostic colonoscopy: commonly about 20-45 minutes, longer if polyps are removed or the colon is difficult to navigate.
• ERCP, EUS and complex therapeutic procedures: often 45 minutes to over an hour.
• Whole hospital visit: usually a few hours, allowing for registration, pre-procedure checks and recovery from sedation.
• Bowel preparation: adds roughly a day of dietary restriction and laxative use before a colonoscopy.

Actual scheduling and recovery-bay times differ between units and depend on the day's case mix.

Understanding your report

An endoscopy report describes what was seen, where, and what was done. Common elements include the extent reached, the quality of the view or bowel preparation, descriptions of the lining, photographs, biopsy sites, and any therapy performed.

• "Normal study": the areas seen looked normal. This is reassuring for structural disease in that region but does not explain every symptom, and does not cover organs outside the scope's reach.
• Inflammation, erosions, gastritis, oesophagitis: descriptive terms. Visual appearance alone does not identify the cause; biopsies, Helicobacter pylori testing and clinical history are needed.
• Ulcer: needs a cause to be established. Gastric ulcers are usually biopsied and often re-examined later.
• Polyp: most colonic polyps are benign. The tissue report determines type and whether surveillance is needed.
• Varices: enlarged veins, usually related to liver disease; need specialist management.
• "Suspicious lesion" or "growth": a visual impression, not a diagnosis. Only the histopathology report can confirm or refute cancer.
• Incomplete study: if the caecum was not reached or the preparation was inadequate, a repeat or alternative test may be advised.

Grading terms used for oesophagitis, gastritis or haemorrhoids are descriptive and partly observer-dependent. A "grade" does not by itself indicate how serious your condition is, and two endoscopists may grade the same appearance slightly differently. Do not act on a report without having it interpreted by the doctor who requested it.

When results can be misleading

Findings that may be falsely reassuring (disease under-called)

• Poor bowel preparation hides polyps and small lesions during colonoscopy.
• Incomplete examination: scope not advanced to the caecum, or a stricture preventing passage.
• Recent or ongoing acid-suppressing therapy can heal surface changes and can also make H. pylori tests taken at endoscopy falsely negative.
• Recent antibiotics or bismuth similarly reduce the yield of H. pylori biopsy-based tests.
• Blood or food residue obscuring the view during a bleeding episode.
• Disease outside reach: small-bowel, pancreatic or extraluminal disease will simply not appear.
• Sampling error: biopsies taken away from the abnormal area.

Findings that may look worse than they are (disease over-called)

• Scope trauma can cause small linear abrasions or minor mucosal tears that look like disease.
• Suction artefact and air insufflation can create redness or pseudo-lesions.
• Bowel preparation itself can cause mild mucosal changes resembling colitis.
• Non-specific "mild gastritis" is very commonly reported and often has little bearing on symptoms.
• Iron tablets can darken the lining and mimic pathology.

Risks and safety

Serious complications from diagnostic endoscopy are uncommon, but they are not zero, and risk differs sharply across the endoscopy family. Risk rises with therapeutic procedures, urgent bleeding cases, and in people with significant heart, lung, liver or kidney disease.

Diagnostic gastroscopy

Common and minor: sore throat, bloating, temporary hoarseness. Uncommon: bleeding after biopsy, reaction to sedation, low oxygen levels, aspiration. Rare: perforation of the food pipe or stomach.

Colonoscopy and polypectomy

Common: cramping, bloating, small amount of blood after biopsy or polyp removal. Uncommon to rare: significant bleeding after polyp removal (which can occur days later), perforation, post-polypectomy burn syndrome, complications of bowel preparation such as dehydration or electrolyte disturbance.

ERCP

Carries the highest complication rate of the routine GI endoscopic procedures. Recognised risks include pancreatitis after the procedure, bleeding after sphincterotomy, infection of the bile ducts and perforation. ERCP uses X-rays, so pregnancy must be declared.

Bronchoscopy

Cough, transient fall in oxygen, minor bleeding after biopsy; less commonly fever, bleeding needing intervention, or pneumothorax after lung biopsy.

Cystoscopy

Burning on passing urine, small amount of blood, urinary infection; rarely urinary retention or urethral injury.

Sedation and anaesthesia

Risks include breathing depression, low blood pressure, aspiration and drug reactions. These risks are higher in obstructive sleep apnoea, obesity, significant heart or lung disease, frailty and in emergency procedures. Monitored sedation by trained staff reduces but does not remove this risk.

Results vary depending on individual clinical circumstances. Ask your endoscopist to quantify your own risk for the specific procedure planned.

Special situations

Pregnancy

Endoscopy is deferred unless the indication is strong. Gastroscopy for significant bleeding is the commonest reason. Radiation-based procedures are avoided or shielded and minimised, and the obstetric team is involved in planning.

Children

Paediatric endoscopy is performed by paediatric gastroenterologists with paediatric anaesthetic support. Indications differ from adults and include suspected coeliac disease, food-related inflammation of the food pipe, suspected foreign body and chronic diarrhoea with growth faltering.

Older adults

Sedation doses are typically reduced, bowel preparation may need to be modified to avoid dehydration, and the benefit of surveillance procedures is weighed against overall health and life expectancy.

Diabetes on glucose-lowering treatment

Fasting and bowel preparation raise the risk of hypoglycaemia. A medicine and monitoring plan should be agreed with the prescriber before the procedure date. Carry glucose monitoring equipment and treatment for low sugar to the hospital.

Chronic kidney disease and heart failure

Preparation choice, fluid volumes and electrolyte monitoring need tailoring. Declare dialysis schedules so timing can be coordinated.

Liver disease and cirrhosis

Endoscopy is used to look for and treat oesophageal varices. Clotting abnormalities, low platelets and sedation sensitivity in advanced liver disease all need specific planning.

Implanted devices and prosthetic valves

Pacemakers and implantable defibrillators affect the use of electrosurgical instruments during polyp removal, so declare them. Antibiotic cover before endoscopy is not routine for most patients; the decision is individual.

Endoscopy in the Indian context

• Common indications reflect local disease patterns. Acid peptic disease and Helicobacter pylori-associated gastritis are frequent reasons for gastroscopy. Gastrointestinal tuberculosis is an important differential for ileocaecal ulceration and can closely mimic Crohn's disease, and colonoscopic biopsies with tissue testing are often central to telling them apart.
• Chronic liver disease is a major driver of endoscopy for variceal screening and banding, including alcohol-related and metabolic dysfunction-associated steatotic liver disease (MASLD, the term that replaced NAFLD; MASH replaced NASH, with MetALD describing coexisting metabolic and alcohol-related contributions).
• Drug-induced liver and gut injury from anti-tubercular therapy, non-steroidal painkillers bought over the counter, and some AYUSH, herbal and gym supplement preparations is a recognised concern; declare everything you take, including non-prescription remedies.
• Corrosive ingestion and foreign body removal remain frequent emergency endoscopy indications, particularly in children.
• Vernacular usage matters. Patients and referral letters may say "scopy", "camera test", "upper GI scopy" or "pet ki jaanch", all generally refer to the procedures described here, but confirm which organ is being examined.
• Data protection. Endoscopy images, videos and reports are sensitive personal health data; handling of consent and digital records is governed by the Digital Personal Data Protection Act, 2023, alongside professional confidentiality obligations under National Medical Commission conduct rules.
• Advertising rules. Claims that any procedure cures disease are prohibited under the Drugs and Magic Remedies (Objectionable Advertisements) Act, 1954; be sceptical of packages promising guaranteed outcomes.

Cost and insurance in India

Costs differ widely between cities, between government and private facilities, and between diagnostic and therapeutic procedures. Prices quoted anywhere should be treated as indicative only and confirmed with the facility in writing before the procedure.

Factors that change the price:

• Procedure type: diagnostic gastroscopy is the least expensive of the group; colonoscopy, EUS and ERCP cost progressively more.
• Sedation or anaesthesia: throat spray only, conscious sedation, or general anaesthesia with an anaesthetist, each adds a different amount.
• Therapeutic add-ons: polypectomy snares, clips, banding kits, stents, dilators, injection agents and retrieval devices are charged as consumables.
• Histopathology: biopsy processing is billed per specimen block, plus any special stains, immunohistochemistry or tissue testing for tuberculosis.
• Day-care versus inpatient: recovery bay, room category and any overnight stay.
• Facility type and city: tier of city, accreditation status and whether the unit is government, trust-run or corporate.
• Emergency out-of-hours procedures usually cost more than planned lists.

Insurance points to check: many indemnity policies cover endoscopy when it is part of a covered admission or day-care procedure, but purely outpatient diagnostic endoscopy may be excluded. Verify day-care procedure coverage, cashless network status, pre-authorisation requirements, waiting periods for pre-existing disease, and whether consumables and histopathology are payable. Government schemes such as Ayushman Bharat PM-JAY cover specified packages at empanelled hospitals, eligibility and package inclusions should be confirmed with the hospital's insurance desk.

Myths and facts

Frequently asked questions

Will I be awake during an endoscopy?

That depends on the procedure and unit. Gastroscopy is often done with throat spray alone or with light sedation, so you may be drowsy but rousable. Colonoscopy is usually done under sedation. Some procedures, and most paediatric endoscopies, need general anaesthesia. Discuss your preference and fitness beforehand.

Can endoscopy tell me straight away whether I have cancer?

Endoscopy can show a lesion that looks suspicious, and the endoscopist may say so on the day. Confirmation requires histopathology of the biopsy, which is reported separately. Staging, how deep and how far spread, usually needs additional tests such as endoscopic ultrasound, CT or PET-CT.

Do I need a colonoscopy if my gastroscopy was normal?

Not automatically. Gastroscopy and colonoscopy answer different questions about different parts of the gut. A colonoscopy is considered when symptoms, bleeding, anaemia, family history or surveillance requirements point to the colon. The decision belongs to the doctor assessing you.

How soon can I eat and go back to work?

After a straightforward diagnostic procedure with sedation, most people eat once fully awake and swallowing safely, and resume usual activity the next day. Avoid driving, machinery and important decisions for the rest of the day. Therapeutic procedures may carry longer dietary and activity restrictions.

Is endoscopy safe if I have heart or lung disease?

Endoscopy is often still possible, but sedation risk is higher and needs planning. Tell the team about angina, recent heart attack, heart failure, arrhythmia, stents, COPD, asthma, oxygen use or sleep apnoea. Monitoring, sedation choice and sometimes anaesthetist involvement are adjusted accordingly.

Why do I have to take such a large bowel preparation for colonoscopy?

Polyps and early cancers are small and easy to hide behind stool. A clean colon directly improves detection and reduces the chance of a repeat procedure. If you have kidney disease, heart failure, a fluid restriction or diabetes, ask the unit for a preparation regimen suited to your condition.

What if my symptoms continue after a normal endoscopy?

Return to the doctor who requested the procedure. Ongoing symptoms may reflect a condition endoscopy cannot show, such as a motility or functional disorder, gallbladder or pancrea