There are currently three main options available to clinicians in NHS Highland when considering the investigation of patients with lower GI symptoms. All of them have the ability to visualise the entire colon and rectum, exclude bowel cancer and diagnose alternative colorectal pathology but there are advantages and disadvantages to each. The following gives a summary of each test along with an estimate of the current capacity.
Colonoscopy
Logistics:
An optical colonoscopy is seen by many as the gold standard for the diagnosis of lower GI pathology. The test involves the patient physically attending the endoscopy department and having a flexible endoscope passed via the anus to the caecum or terminal ileum. A colonoscopy is termed ‘diagnostic’ if the nature of the pathology is unknown or ‘therapeutic’ if the pathology is known and a particular intervention is planned e.g. polypectomy or endomucosal resection (EMR). The preparation for the test is relatively intense and may involve stopping certain medications e.g. iron tablets or anticoagulants as well as following the specific dietary and bowel preparation advice provided by the endoscopy department. Detailed information on the current oral bowel cleansing protocols is provided via the NHSH endoscopy homepage (link below) but normally involves the patient following strict dietary advice as well as drinking 4 litres of ‘Vistaprep’ solution. The colonoscopy itself usually takes 30-45 minutes to complete and the patient is often asked to roll into different positions during the procedure. The procedure can be uncomfortable and each patient is offered the choice of IV sedation (usually a combination of fentanyl and midazolam) or inhaled nitrous oxide (Entonox). NHS Highland endoscopy intranet site
Advantages & Disadvantages:
A colonoscopy (or flexible sigmoidoscopy) is the only colonic investigation that has the ability to provide histological confirmation of a cancer via biopsy and/or the option to remove colorectal polyps. For this reason, it is the preferred investigation for patients deemed at high risk of having colorectal cancer and is therefore the test of choice for most patients referred in a USC category. The main disadvantage of the test is that it is an invasive procedure that carries a small but real risk of serious or even life-threatening complications such as perforation or bleeding. In addition, the invasive nature of the test, combined with the requirement for bowel preparation and medication alterations means it is not generally a good test for elderly, frail or co-morbid patients The other consideration from a service perspective is that colonoscopy has a limited capacity within NHS Highland and efforts should therefore be directed towards priority access for patients who are likely to benefit most.
Risks:
- Caution required in elderly or frail patient who may struggle with oral bowel preparation.
- Caution required in patients with diabetes, renal impairment or significant cardiorespiratory disease
- Complications associated with IV sedation, opiod use or Entonox inhalation e.g. respiratory depression or hypotension.
- Inability to complete the test due to pain, acute angulation, looping or other technical difficulty.
- Bleeding from a biopsy or damage to the bowel from the scope (1 in 1000)
- Bleeding from a polypectomy (1 in 100). Particular care must be taken if a patient takes blood-thinning medication.
- Perforation of the bowel (1 in 1000). In some cases this can require emergency surgery.
Capacity:
| Screening colonoscopy |
= |
550 per year |
| New colonoscopy |
= |
1000 per year |
| Return colonoscopy |
= |
500 per year |
CT colonogram (CTC)
Logistics:
A computed tomography pneumocolonogram (CTC) or ‘virtual’ colonoscopy is a specialised type of CT scan designed to detect pathology in the colon. The test involves the patient following specific instructions and can only be carried out in secondary care environments. Preparation involves following a low fibre diet for the 24 hour period before the test. On the day before the scan, patients are asked to drink 50ml of gastrograffin (diluted in 500ml of water) at 6pm. This has a slight laxative effect and the patient should be aware of the need to be near a toilet. On the day of the test, the patient attends the radiology department and has a cannula placed in order to receive Buscopan and x-ray contrast. Once on the scanning table, a small tube is inserted into the rectum and the colon is filled with carbon dioxide. During the scan sequence, the patient is asked to turn into different positions (supine, lateral, prone) to obtain complete views of the colon.
Advantages & Disadvantages:
A CTC is less invasive than an optical colonoscopy and is often chosen to exclude significant bowel pathology, including colorectal cancer, in patients who are unable or unwilling to tolerate a colonoscopy. However, it still requires some bowel preparation and involves passing a rectal tube which some patients can find uncomfortable. In general, a CTC is the preferred test for elderly patients although in those who are particularly frail a plain CT or not investigating at all may be more appropriate.
Risks:
- Involves ionising radiation, especially relevant to females of child bearing age.
- Involves IV contrast, especially relevant to those with kidney impairment or known allergies.
- Involves buscopan which can be associated with short-term side effects e.g. dry mouth or blurred vision
- Caution is required in patients with diabetes
- The test can miss low rectal pathology and should be supplemented with a careful rectal examination +/- rigid sigmoidoscopy if there is clinical concern.
- 1 in 3000 risk of perforation
Capacity:
700 per annum
Colon Capsule Endoscopy (CCE)
Logistics:
Colon capsule endoscopy (CCE) is a non-invasive alternative to colonoscopy. It involves the patient swallowing a capsule which captures around 50,000 images of the gastrointestinal (GI) tract as it travels through. Bowel preparation is required (equivalent to colonoscopy) to cleanse the colon before the procedure. “Boosters” (additional laxatives) are consumed after the capsule is swallowed to help propel the capsule through the GI tract and ensure the whole colon and rectum is visualised. Tests are currently carried out by a managed service at 4 sites across NHS Highland – Inverness, Thurso, Skye and Fort William. CCE procedures are interpreted by a consultant gastroenterologist and a report produced which is returned to the referring consultant to decide if further management is required. A link to the electronic version of the NHS Scotland Colon Capsule Endoscopy ‘Playbook’ is provided here https://learn.nes.nhs.scot/61072
Advantages & Disadvantages:
CCE is best suited for those patients with new lower GI symptoms with a low risk of harbouring colorectal pathology (based on their FIT result). Some patients who undergo CCE will require a further test such as colonoscopy or flexible sigmoidoscopy. For the majority, a further endoscopic procedure is required to treat or biopsy pathology found by the capsule, although some require a test because the colon and rectum have been inadequately visualised. The published accuracy of CCE for colorectal pathology is high and it can safely exclude colorectal cancer. CCE has been shown to be a safe test with a very low rate of adverse events. Overall, 37% of patients will not need any further investigation while 63% will require an additional or supplementary test (see below).
Risks:
- Approximate 30% chance of an ‘incomplete’ test.
- SCOTCAP data suggest 63% of patients will need an additional investigation or procedure, either because the test was incomplete or pathology (e.g. size significant polyps) was found.
- capsule retention is a rare complication (rate 0.05%) but can cause obstruction requiring emergency management
Capacity:
500-600 per annum
TAM (Treatments and Medicines) NHS Highland