The ideal bowel preparation reliably empties the intestine of all faecal material, with no histologic alteration of the colonic mucosa, and with as little discomfort and side-effects as possible for the patient. Non-invasive possibilities of bowel preparation, which consist of oral liquid diet or minimal residue diet, combined with laxatives, give suboptimal results and must be started days before the planned intervention. The most commonly prescribed preoperative bowel preparations are poly-ethylene glycol (PEG) and sodium phosphate. Historically these prescribed solutions are called mechanical bowel preparation in the surgical literature; however, this nomenclature seems outdated since there is no actual “mechanical” aspect to these drugs. In this chapter we have chosen to speak of bowel preparation, as is done in the field of gastroenterology.

Polyethylene glycol (PEG) is iso-osmotic, non-absorbable and acts by retaining fluid in the colon. Four litres are required. It is generally well tolerated; however, up to 15 % of patients do not complete the preparation due to poor taste and/or the large volume. PEG can safely be given to patients with comorbidities such as electrolyte disturbances, renal failure, heart failure, and liver insufficiency. Reduced volume options are available in a 2-l formulation, combined with stimulant agents such as bisacodyl or prokinetic agents such as metoclopramide. They have been associated with an equivalent level of cleansing and better patient tolerance.

Several histological studies have shown that bowel preparation is associated with bowel wall alterations consisting of loss of superficial mucus and epithelial cells, as well as inflammatory changes such as lymphocyte and polymorphonuclear cell infiltration. In addition, bowel preparation can be associated with a higher rate of bowel contents spillage, because liquid contents cause higher rates of spillage. This showed a trend toward more infectious complications; however, this increase was not statistically significant. The degree of inadequate bowel preparation is described between 20 and 40 % in literature.

For all the above mentioned pathophysiological and patient-related reasons, the use of bowel preparation has been questioned in recent years. Patients in general do not like it, so do we really need it? Does it facilitate surgery? Are infectious and non-infectious complications decreased with bowel preparation? Does it facilitate the possibility to palpate small intraluminal masses intraoperatively? All these questions led to many prospective randomized trials and Cochrane reviews (Table 5.1). When we look at the evidence regarding infectious post-operative complications, we can subdivide the results for colon and rectum resections.