Altered bowel habit – loose stool (diarrhoea), constipation or both. There is a broad list of potential causes for diarrhoea. In the short term, gastroenteritis (i.e. a gut infection) always warrants consideration, and often resolves without specific treatment.

Diarrhoea that is more long-standing may be due to inflammatory bowel disease (including both Crohn’s disease and ulcerative colitis), irritable bowel syndrome, coeliac disease or microscopic colitis, just to name a few. Bowel cancer is a potential cause of altered bowel habit. A change of bowel habit is a common reason to undergo diagnostic colonoscopy.

Rectal bleeding – this may be due to a number of different conditions including haemorrhoids, colonic polyps, or even bowel cancer, and almost always warrants diagnostic colonoscopy. Polyps are small growths within the large bowel which have the potential to turn into bowel cancer in the long term.

Polyps are usually under 1 cm in size, however may be 2 or 3cm or even larger than this. The majority of colonic polyps can be safely excised / removed during colonoscopy

Abdominal pain – depending upon the site and nature of the pain, this also has a broad range of different possible diagnoses. Common conditions include gallstones, peptic ulcer disease, gastro-oesophageal reflux, and functional dyspepsia.

Family history of bowel cancer or previous colonic polyps – depending upon the family history, regular surveillance with colonoscopy to detect and remove polyps may be appropriate. Those with colonic polyps detected at previous colonoscopies generally have an increased risk of developing further polyps in the future and are often candidates for further surveillance colonoscopy as well. Detection and excision of colonic polyps has been shown to reduce the risk of developing colorectal cancer.

Postive faecal occult blood test (FOBT) – for example through the National Bowel Cancer Screening Program, or as requested by your GP. The FOBT (detection of microscopic amounts of blood in the stool) is a screening test, and a positive result almost always warrants colonoscopy as those with a positive test have an increased risk of colonic polyps, and indeed a small risk of bowel cancer at colonoscopy. If bowel cancer is detected, it is often found at an early stage where it can be much more easily treated.

Iron deficiency anaemia – This may be due to bleeding from the gut (e.g. from the stomach, small bowel or large bowel), even in the absence of symptoms. Depending upon the history and results of blood tests, further investigation is usually warranted.

Inflammatory bowel disease – Crohn’s disease and ulcerative colitis. The aim of treatment is to maximise the patient’s quality of life and minimise the risk of complications in the long term. Treatment of inflammatory bowel disease is often complex and treatment by a specialist with an interest is inflammatory bowel disease is warranted in almost all cases.

Gastro-oesophageal reflux (GORD) – reflux of acid from the stomach into the oesophagus, often causing heartburn or indigestion. In some cases reflux can lead to reflux oesophagitis (inflammation of the oesophagus). Those with poorly controlled reflux are at risk of developing Barrett’s oesophagus (a change in the lining of the lower oesophagus which has an increased risk of cancer of the oesophagus in the long term).

Surveillance gastroscopy every 2-3 years should be considered for patients with proven Barrett’s oesophagus. Information sheet about reflux

Swallowing difficulties (‘dysphagia’). This has a broad differential diagnosis, including oesophageal strictures, oesophageal cancer, oesophageal motility problems and eosinophilic oesophagitis. Dysphagia is always an indication for diagnostic gastroscopy.

Stomach or duodenal ulcers (a.k.a. peptic ulcer disease). The most common causes include Helicobacter pylori, an organism commonly found in the lining of the stomach and non-steroidal anti-inflammatory drugs (NSAIDs, e.g. Indocid, Naprosyn, etc.). Most easily diagnosed at gastroscopy, the treatment is tailored to the presumptive cause and is usually curative.

Historically, surgery was commonly performed for peptic ulcer disease, however with contemporary treatment this is rare.

Abnormal liver function tests are a common reason for referral to a gastroenterologist and have a very broad range of causes.

Incidental findings on imaging such as liver or pancreas lesions often warrant referral to a gastroenterologist