Pre-operative mechanical bowel cleansing or not? an updated meta-analysis

Pre-operative mechanical bowel preparation has been considered an efficient regimen against leakage and infectious complications, after colorectal resections. This dogma is based only on observational data and experts' opinions. The aim of this study was to evaluate the efficacy and safety of prophylactic pre-operative mechanical bowel preparation before elective colorectal surgery.

EMBASE, LILACS, MEDLINE and The Cochrane Library and abstracts from major gastroenterological congresses were searched. No language restrictions were applied. The selection criterion used was randomised clinical trials (RCT) comparing any kind of mechanical bowel preparation with no preparation in patients submitted to elective colorectal surgery and where anastomotic leakage, mortality, and wound infection were outcome measurements. Data were independently extracted by the reviewers and cross-checked. The methodological quality of each trial was assessed by the same reviewers. For meta-analysis the Peto-Odds ratio was used.

Of 1592 patients (9 RCTs), 789 were allocated to mechanical bowel preparation (Group A) and 803 to no preparation (Group B) before elective colorectal surgery. Anastomotic leakage developed in 48 (6%) of 772 patients in A compared with 25 (3.2%) of 777 patients in B; Peto OR 2.03, 95% (CI: 1.28-3.26; P = 0.003). Wound infection occurred in 59 (7.4%) of 791 patients in A and in 43 (5.4%) of 803 patients in B; Peto OR 1.46, 95% (CI: 0.97-2.18; P = 0.07); Five (1%) of 509 patients died in group in A compared with 3 (0.61%) of 516 patients in group B; Peto OR 1.72, 95% (CI: 0.43-6.95; nonsignificant).

There is no evidence that patients benefit from mechanical bowel preparation. On the contrary taking colorectal surgery as a whole, pre-operative bowel cleansing leads to a higher rate of anastomotic leakage. The dogma that mechanical bowel preparation is necessary before elective colorectal surgery has to be reconsidered.