The caecum is about 6 cm long and opens from the ileum and ileocaecal valve (Tortora and Derrickson [243]).

The colon consists of three parts. The ascending colon runs from the caecum and joins the transverse colon and the hepatic flexure. The transverse colon is in front of the duodenum, where it joins the descending colon at the splenic flexure. The descending colon travels down towards the middle of the abdomen, where it joins the sigmoid colon, which is S‐shaped and becomes the rectum (Tortora and Derrickson [243]).

The rectum is approximately 20 cm long and is a dilated section of the colon. It joins the anal canal, which is approximately 2–3 cm long (Tortora and Derrickson [243]).

A colonoscopy is performed to investigate specific symptoms originating from the lower GI tract, such as bleeding. The endoscopist uses direct vision to diagnose, sample and document changes in the lower GI tract (MacKay et al. [130], Pagana and Pagana [177], Taylor et al. [238]).

Competencies and consent are the same as those discussed in the section on gastroscopy, above.

The NPSA ([170]) has highlighted the risks in relation to bowel preparation and actions required to minimize these. Harm to patients has occurred where oral bowel preparations were prescribed to those with definite contraindications; however, the majority of the incidents (56%) were related to the administration of the bowel preparations (Connor et al. [36]). The NPSA ([170]) identified that one death and 218 patient safety incidents resulting in moderate harm were related to the use of oral bowel preparations where contraindications were not considered or assessed.

A colonoscope is a flexible endoscope that generally uses fibreoptics to allow direct visualization of the rectum and colon (Chernecky and Berger [32], MacKay et al. [130], Pagana and Pagana [177], Smith and Watson [231]).

Bowel preparation agents, such as senna tablets and Citramag, are given to the patient to take 1 day before the colonoscopy to clear the bowel and minimize faecal contamination (Connor et al. [36]). A sedative and possibly an analgesic are usually administered before the procedure. This involves the administration of a benzodiazepine such as midazolam and an opioid such as fentanyl or pethidine. Doses must be titrated for elderly patients and those with co‐morbidities such as cardiac or renal failure. An antispasmodic may also be given. Oxygen therapy should also be administered during sedation. Generally, 2 litres per minute is adequate for most circumstances to maintain oxygen saturation levels and prevent hypoxaemia (BSG [29], Connor et al. [36], MacKay et al. [130], Riley [208]).

A medical and nursing history and assessment must be undertaken to identify any care needs or concerns that may be significant. In particular, this should cover the patient's current drug therapy, drug reactions and allergies, any organ dysfunctions (such as cardiac and/or respiratory disease), and previous and current illnesses. It is also important to be aware of any coagulopathies, as samples of tissue or biopsy may need to be taken during the procedure. This can be pre‐empted by reviewing blood results prior to the colonoscopy (Chernecky and Berger [32], Pagana and Pagana [177]).

To complete a successful colonoscopy, the bowel must be clean so that the physician can clearly view the colon. Most patients will require a bowel preparation. It is very important that the patient is given clear written instructions for bowel preparation well in advance of the procedure. Without proper preparation, the colonoscopy will not be successful and the test may have to be repeated. The patient must be individually assessed before being supplied with the bowel preparation and the potential contraindications, considered below.

The choice of bowel preparation must consider the advantages and disadvantages of each product, the tolerability, efficacy and possible side‐effects. If the patient feels nauseated or vomits while taking the bowel preparation, they are advised to wait 30 minutes before drinking more fluid and start with small sips of solution. Some activity such as walking or a few cream crackers may help decrease the nausea (Connor et al. [36], Smith and Watson [231], Swan [235]).

Two days prior to the colonoscopy, specific light foods may be eaten, such as steamed white fish, and others avoided, such as high‐fibre foods. On the day before the colonoscopy, breakfast from the approved food groups may be eaten while drinking plenty of clear fluids. The period of bowel cleansing generally should not be longer than 24 hours. On the day of the procedure, patients can drink tea or coffee with no milk 4 hours before and water up to 2 hours before. Some patients who are at risk of hypovolaemia and dehydration may need to be admitted to hospital for pre‐hydration (Connor et al. [36], MacKay et al. [130], Smith and Watson [231], Swan [235]).

A set of observations (including temperature, pulse, blood pressure, respiration rate and oxygen saturations) should also be taken to identify any pre‐procedural abnormalities and provide a baseline. If the patient has diabetes, their blood glucose level should be checked (BSG [26], [29], Connor et al. [36], Smith and Watson [231]).

Physiological monitoring and care post‐sedation should be the same as those for gastroscopy. However, larger doses of sedative and opioids may have been used so further observation is required. The patient may feel some cramping or a sensation of having gas, but this quickly passes on eating and drinking. Bloating and distension typically occur for about an hour after the examination until air in the bowel that developed during the procedure is expelled. Unless otherwise instructed, the patient may immediately resume a normal diet, but it is generally recommended that the patient waits until the day after the procedure to resume normal activities (BSG [29], MacKay et al. [130]).

If a biopsy was taken or a polyp was removed, the patient may notice light rectal bleeding for 1–2 days after the procedure. Large amounts of bleeding, the passage of clots or abdominal pain should be reported immediately.

When an endoscopic mucosal resection (EMR) or an endoscopic submucosal dissection (ESD) is conducted, a thermal injury to the bowel wall may occur. The patient may present with localized tenderness and pyrexia. Generally, conservative management is adequate, but it is essential to monitor the patient's condition as they may go on to develop a perforation (MacKay et al. [130]).

During the procedure, the greatest risk or possible complication is bowel perforation; this may be apparent during the procedure but it can present 3–4 days after the procedure. It occurs in 1 in 1000 cases (MacKay et al. [130], Pagana and Pagana [177]). If a snare polypectomy was conducted, the incidence of perforation is 0.1–0.3%. The incidence rises to 5% following an EMR (MacKay et al. [130], Smith and Watson [231]). The nurse monitoring the patient after colonoscopy should be familiar with potential signs and symptoms, such as unresolved abdominal pain, rigidity and/or bleeding. If a perforation occurs, surgical intervention is likely to be required (MacKay et al. [130], Pagana and Pagana [177], Smith and Watson [231], Suissa et al. [234]).

On average, haemorrhage occurs in 3 in 1000 procedures but the incidence and complication rates may be higher where a procedure involves a polypectomy. MacKay et al. ([130]) state that the incidence post‐polypectomy should be less than 1%, and it should be 0.5–6.0% following EMR. Post‐procedure monitoring by the nurse again includes observing for signs and symptoms of bleeding (MacKay et al. [130], Smith and Watson [231]). Depending on the severity of the bleed, it may be managed conservatively, but embolization may be required in haemodynamically unstable patients (MacKay et al. [130], Pagana and Pagana [177], Suissa et al. [234]).