Upper GI Endoscopy & Colonoscopy — How It Works, Benefits & Recovery — Procedure Guide, Recovery & Risks | MyMedicPlus

Upper gastrointestinal (UGI) endoscopy, also called gastroscopy or oesophagogastroduodenoscopy (OGD), is the gold-standard examination of the oesophagus, stomach, and duodenum using a flexible video endoscope — a thin, manoeuvrable tube two centimetres in diameter containing a high-definition camera, light source, and working channels for biopsy forceps or therapeutic instruments. Colonoscopy is the complementary lower GI investigation, in which a longer (one hundred and fifty to one hundred and eighty centimetre) flexible colonoscope is advanced from the rectum through the entire colon to the ileocaecal valve, allowing visualisation of the entire colorectal mucosa and, in some cases, the terminal ileum. Both procedures are performed by gastroenterologists or colorectal surgeons in dedicated endoscopy units and enable direct mucosal inspection, targeted biopsy, and simultaneous therapeutic intervention (polypectomy, haemostasis, stricture dilation). Together they constitute the most important tools for diagnosing and managing pathology throughout the gastrointestinal tract. In the United Kingdom approximately one million colonoscopies and two million upper GI endoscopies are performed annually. Globally, colonoscopy is the cornerstone of colorectal cancer screening programmes recommended by ASGE, ESGE, and national gastroenterology societies. Combined UGI endoscopy and colonoscopy is performed under conscious sedation.

UGI endoscopy is indicated for dysphagia (difficulty swallowing) at any age, iron-deficiency anaemia unexplained by other investigations, persistent upper abdominal pain or dyspepsia not responding to proton pump inhibitor therapy, confirmed or suspected peptic ulcer disease, upper gastrointestinal bleeding (haematemesis or melaena), clinical suspicion of Barrett's oesophagus, surveillance of known oesophageal or gastric pathology, and exclusion of upper GI malignancy in patients with alarm symptoms (unexplained weight loss, dysphagia, persistent vomiting, palpable mass). Colonoscopy is indicated for colorectal cancer screening in average-risk adults aged forty-five years and above per USPSTF and ACS guidelines, lower gastrointestinal bleeding (rectal bleeding, haematochezia, occult blood positivity on FIT test), iron-deficiency anaemia without upper GI source, unexplained change in bowel habit lasting more than six weeks, clinical suspicion or known inflammatory bowel disease requiring assessment and biopsy, polypectomy or polyp surveillance, and colorectal cancer resection margins assessment. Both procedures are indicated for patients with hereditary colorectal cancer syndromes (Lynch syndrome, familial adenomatous polyposis) requiring intensive surveillance starting at younger ages. Combined procedures on the same day (bidirectional endoscopy) are performed when both upper and lower GI evaluation is required to investigate iron-deficiency anaemia or unexplained GI bleeding.

UGI endoscopy begins with the patient lying on their left side. A throat anaesthetic spray (lignocaine 10%) may be administered to reduce the gag reflex. Intravenous conscious sedation — typically midazolam two to five milligrams with or without intravenous fentanyl fifty to one hundred micrograms — is given after a cannula is sited and monitoring attached (oxygen saturation, blood pressure, ECG). The endoscope is inserted through the patient's mouth, over the tongue, through the pharynx, and into the oesophagus. Under direct vision the operator advances the scope through the oesophagus, across the gastro-oesophageal junction, around the stomach (systematic inspection including retroflexion in the gastric body to view the cardia and fundus), through the pylorus, and into the first and second parts of the duodenum. Biopsies are taken from suspicious areas. Colonoscopy requires bowel preparation the preceding day with a laxative solution (macrogol-based or sodium picosulphate preparation) to clear faecal material. With the patient in the left lateral position and under conscious sedation, the colonoscope is advanced under combined direct vision and abdominal palpation support from nursing staff. Carbon dioxide (CO2) insufflation reduces post-procedure bloating compared to air. Full intubation of the colon to the caecum is confirmed by identifying the ileocaecal valve and appendix orifice. A slow, systematic withdrawal over at least six minutes is the key quality measure for adenoma detection. Polyps are removed with snare polypectomy (cold or hot, depending on size) during withdrawal.

Diagnostic UGI endoscopy provides direct visualisation with simultaneous biopsy capability, achieving diagnostic accuracy exceeding ninety percent for peptic ulcer disease, Barrett's oesophagus, and upper GI malignancy — superiority to barium meal studies and CT for mucosal pathology. In acute upper GI bleeding, endoscopy both diagnoses the source and treats it (injection, thermal coagulation, clips) in ninety-five percent of cases, reducing the need for emergency surgery. Colonoscopy is the only screening modality that detects and simultaneously removes precancerous polyps, reducing colorectal cancer incidence by forty to sixty percent and colorectal cancer mortality by sixty to seventy percent in the screened population — evidence from multiple large randomised trials including NordICC (2022, NEJM) and COLONPREV. Adenoma detection rate (ADR) — the percentage of screening colonoscopies at which at least one adenoma is detected — is the key quality metric: each one percent increase in ADR corresponds to a three percent decrease in interval colorectal cancer risk. High-quality colonoscopy (ADR greater than twenty-five percent in average-risk populations) is therefore directly cancer-preventive. Both procedures allow immediate tissue diagnosis of suspicious lesions with biopsy results typically available in five to seven working days.

Upper GI endoscopy is a very safe procedure with serious complication rates below one in one thousand. Aspiration of gastric contents is the most significant risk, particularly in patients who have not fasted adequately (minimum six hours for solids, two hours for clear fluids). Sore throat and abdominal discomfort are common minor aftereffects lasting up to twenty-four hours. Oesophageal perforation is rare (less than one in five thousand) and occurs most commonly with therapeutic procedures or Zenker's diverticulum. Colonoscopy carries higher procedural risks due to its greater complexity: perforation occurs in one in one thousand to one in three thousand procedures (higher with therapeutic interventions), serious post-polypectomy bleeding in one in one hundred to one in two hundred polypectomies, and post-polypectomy syndrome (transmural burn causing localised peritoneal irritation) in approximately one percent of snare polypectomies. These serious complications require hospitalisation and occasionally surgical intervention. Sedation-related adverse events (respiratory depression, hypotension, aspiration) occur in less than one percent of cases with appropriate pre-procedure assessment and monitoring. Failure to achieve complete caecal intubation occurs in three to five percent of colonoscopies, most commonly due to patient anatomy, inadequate preparation, or colonic tortuosity, and may require CT colonography or repeat procedure.

After UGI endoscopy or colonoscopy under conscious sedation, patients are monitored in the recovery area for one to two hours until they are fully alert, their oxygen saturation is stable, and they are able to walk safely. Patients must not drive, operate machinery, or make important decisions for twenty-four hours after receiving intravenous sedation, and must be accompanied home by a responsible adult. Mild throat soreness (after gastroscopy), abdominal bloating, and flatulence (after colonoscopy) are common and resolve within two to four hours. Normal diet can be resumed within two to four hours of gastroscopy and after colonoscopy as soon as the patient feels comfortable. Following polypectomy, patients are advised to avoid NSAIDs and aspirin for five to seven days to reduce the risk of delayed bleeding. Biopsy results are communicated by the referring doctor at a follow-up appointment typically within two to four weeks. Surveillance intervals after colonoscopy depend on polyp number, size, and histology: no polyps or one to two small tubular adenomas below ten millimetres require repeat colonoscopy at five to ten years; three to four or any adenoma with high-risk features requires three-year surveillance; five or more adenomas or those above ten millimetres require one-year surveillance.