Think mechanical bowel preparation (MBP) is a must for gynecologic surgery?
Although MBP has been around since the 1930s, a growing body of data suggest that, with rare exception, gynecologists can eliminate routine use of preoperative MBP from their practice.
In this article, we discuss the evidence surrounding MBP so that you can assess the benefits and risks it poses for your surgical patients.
Unproven assumptions are behind MBP
For most of the past century, MBP has been used in advance of abdominal surgery,
including gynecologic surgery. Clinicians made the rational assumption that, by decreasing the fecal load within the colon, they could lower the risk of certain surgical complications, especially during an era when antibiotics were not available to treat serious infectious morbidity. In modern times, the practice has continued when major abdominal surgery is planned. Why? Because surgeons believe it will reduce the risk of wound infection, anastomotic leakage, and bowel spillage in the event of injury, and that it will increase the ease of bowel manipulation.1
A growing body of literature challenges these assumptions and suggests that MBP is not associated with these benefits—and may even increase the incidence of some of these complications. Moreover, the induction of profuse, watery diarrhea to evacuate the colon before surgery has been associated with severe electrolyte imbalance, renal failure, and difficult intraoperative fluid management.
These risks make a thorough assessment of MBP’s effects imperative to guide optimal practice.
- Mechanical bowel prep has many side effects, ranging from mild (discomfort) to severe (renal failure).
- The risks of surgical site infection and anastomotic leakage are not lower with MBP, compared with no preparation, in patients undergoing elective colon surgery.
- MBP does not reduce the risk of intraoperative contamination of the surgical field.
- In unplanned injuries to unprepared colon (e.g., in cases involving trauma), primary anastomosis is the recommended mode of repair rather than diverting colostomy.
- MBP does not ease bowel manipulation in laparoscopy, compared with no preparation.
- The only proven value of MBP is to improve visibility during intraoperative colonoscopy.
- Gynecologists can eliminate the routine use of MBP from their surgical practice.
MBP is the chemical or physical process of eliminating fecal matter from the intestinal tract. There are a variety of methods, including ingestion of an oral preparation and enemas and suppositories. Historically, MBP included stimulant laxatives, such as senna extract and castor oil, and hyperosmotic solutions, such as mannitol and lactulose.
MBP is distinctly separate from antibiotic bowel preparation and preoperative prophylactic antibiotics, both of which fall beyond the scope of this article.
The most common forms of MBP prescribed today are balanced electrolyte solutions, including polyethylene glycol, and saline laxatives, such as magnesium citrate and sodium phosphate.2
Some investigators have attempted to determine which MBP formulations are most effective, based on visualization during colonoscopy, but a recent meta-analysis suggests that most formulations perform similarly.3
The risks associated with MBP are clearly documented in the literature and range in intensity from mild to severe. Overall, patients report discomfort, with symptoms such as abdominal pain and distension, nausea and vomiting, weakness, and insomnia.4 High-volume preparations, such as polyethylene glycol, are unpalatable to patients and, therefore, less likely to be ingested completely, leaving the surgeon with a partially evacuated colon.
Dehydration and electrolyte disturbances may also complicate the use of MBP, particularly with saline laxatives. Although young patients can likely tolerate electrolyte shifts without severe sequelae, elderly patients who have comorbid heart and kidney disorders may become further deconditioned during the MBP process. Seizures and esophageal tears have been reported as a result of MBP.5 Sodium phosphate, in particular, is associated with renal failure, with 171 cases reported to the US Food and Drug Administration (FDA) from 2006 to 2007—leading to an issued warning not to employ this agent in preoperative MBP in the liquid formulation.6
In addition, in one study, investigators observed an increased time to the return of bowel function and a prolonged hospital stay among patients who underwent MBP.7
Purported benefits of MBP
Reducing the risk of surgical site infection
Surgical site infection (SSI)—whether intra-abdominal or in the superficial wound—is a serious complication that can lead to severe morbidity. As colorectal surgeons began performing more aggressive colon surgery in the 1930s, 40s, and 50s, they sought a way to reduce SSI. Mortality from colon surgery was 10% to 30%, with a rate of SSI of 80% to 90%, so surgeons began to seek a method to decrease the fecal bacterial load, presuming that doing so would also reduce the rates of infection and mortality and allow for primary repair of the colon. MBP appeared to address the problem.1