Lower gastrointestinal endoscopy

Introduction

Since flexible endoscopy of the colon was introduced in 1963, it has become the gold-standard diagnostic test for evaluation of colonic disease. Improvements in technique and technology have also led to advances in therapeutic procedures, and the boundary between endoscopic and surgical procedures is becoming increasingly blurred. A good understanding of both the technique and technology is essential for an endoscopist to perform high-quality, safe endoscopy. This chapter gives an insight into how lower gastrointestinal (GI) endoscopy is influencing the practice of colorectal surgery.

Indications and contraindications

Checklist

Checklists prevent errors, have a positive impact on patient morbidity and mortality in surgical settings and are now commonplace, or mandatory, in many endoscopy units.

Sedation

Sedation during colonoscopy is the subject of much debate and research. A large multicentre European audit showed that most colonoscopies were done using moderate (conscious) sedation and that although deep sedation was associated with shorter procedure times and fewer technical difficulties, it was also more resource-intensive and required more hospitalisations for complications. American Society of Gastrointestinal Endoscopy recommendations are that routine use of deep sedation in average-risk patients cannot be endorsed. A recent British position statement noted that the need for deep sedation and anaesthesia is increasing because of the growing complexity of GI endoscopy. Flexible sigmoidoscopy is most often performed unsedated, as the use of intravenous sedation would negate many of the potential benefits of the procedure. Unsedated colonoscopy is certainly possible with few complications and good acceptability. Nitrous oxide (Entonox) can be a useful adjunct in unsedated patients as it is short acting and reversible, but does have a cost implication and is implicated in climate change, as it is 300 times more potent as a greenhouse gas than carbon dioxide.

Insertion technique

Insertion technique varies even amongst expert colonoscopists. Technique depends on local circumstances, sedation practice, endoscopist preference and equipment available. However, there are some basic principles that are recognised to contribute to safe, efficient colonoscopy.

Patient position change

Moving the patient’s position from the left lateral position during both insertion and withdrawal can shift both fluids away from, and air into, the uppermost segment of bowel, preventing unnecessary suctioning of fluid and insufflation of gas. It can provide mechanical advantage by opening up acute bends, especially at the rectosigmoid junction, splenic and hepatic flexures. The effective use of gravity to assist the passage of the endoscope is a simple, technique that is easily learnt. It has been shown to be effective in promoting endoscope tip advancement in two-thirds of cases, but it does require cooperation from the patient and can be difficult if heavy sedation or general anaesthesia is used ( Fig. 1.1 ). If water immersion or exchange is used, the patient should remain in the left lateral position while negotiating the left colon, as the water helps weigh down the sigmoid, minimising loop formation by reducing acute bends and tight angulations.

Three-dimensional imager

Magnetic imaging systems (ScopeGuide, Olympus Optical Company; ScopePilot, Pentax Medical) use low-voltage magnetic fields to produce a real-time, three-dimensional image of the entire colonoscope shaft in both anteroposterior and lateral views, allowing the colonoscopist to visualise the configuration of the scope within the patient ( Fig. 1.2 ). This can help determine if there is an anterior component to a loop and so assist with loop resolution, as well as aiding accurate tip location. A sensor can assist with accurate hand-pressure placement.

Meta-analysis of eight randomised controlled trials has shown real-time magnetic imaging to be of benefit in training and educating inexperienced endoscopists and improves the caecal intubation rate for experienced and inexperienced endoscopists.

Withdrawal and examination technique

It should be remembered that the aim of colonoscopy is to visualise the whole of the colonic mucosa to identify pathology. A systematic review of back-to-back studies has shown a polyp miss rate at colonoscopy of 22%, even in expert hands, although most missed polyps were small (<1 cm). All studies investigating miss rates have shown a variation in performance between endoscopists, and this can be wide even with expert examiners (>10 000 procedures), with sensitivities ranging from 17–48% in one large study. This implies that there is a link between individual technical skill and outcome measures. Studies looking at the causes of post-colonoscopy colorectal cancers have shown that up to 89% may be avoidable, although tumour biology may be more important than endoscopist factors.