Adhesive small bowel obstruction: epidemiology, biology and prevention.(Surgical Biology for the Clinician/Biologie chirurgicale pour le clinicien)(Disease/Disorder overview)

Intraabdominal adhesions develop after abdominal surgery as part of the normal healing processes that occur after damage to the peritoneum. Over the last 2 decades, much research has gone into understanding the biochemical and cellular processes that lead to adhesion formation. The early balance between fibrin deposition and degradation seems to be the critical factor in adhesion formation. Although adhesions do have some beneficial effects, they also cause significant morbidity, including adhesive small bowel obstruction, infertility and increased difficulty with reoperative surgery. Several strategies have been employed over the years to prevent adhesion formation while not interfering with wound healing. This article summarizes much of our current understanding of adhesion formation and strategies that have been employed to prevent them.

Les adherences intra-abdominales font leur apparition apres une chirurgie a l'abdomen dans le cours des mecanismes de guerison normaux suivant un dommage au peritoine. Au cours des deux dernieres decennies, on a effectue beaucoup de recherches afin de comprendre les phenomenes biochimiques et cellulaires a l'origine de la formation d'adherences. L'equilibre precoce entre le depot de fibrine et sa degradation semble jouer un role critique dans la formation d'adherences. Meme si les adherences ont certains effets benefiques, elles causent aussi une morbidite importante, y compris l'occlusion de l'intestin grele, l'infecondite et les difficultes accrues dans le cas d'interventions chirurgicales ulterieures. On a suivi au fil des ans plusieurs strategies pour prevenir la formation d'adherences sans nuire a la guerison de la plaie. Cet article resume une grande partie des connaissances actuelles au sujet de la formation d'adherences, ainsi que les strategies que l'on a suivies pour les prevenir.

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Postoperative adhesions form after trauma to the peritoneal cavity and are a result of the biochemical and cellular response that occurs in an attempt to repair the peritoneum. Although there are beneficial effects to adhesions, they are the leading cause of small intestinal obstruction after abdominal surgery and can be the source of significant morbidity, in some cases leading to mortality. This review aims to provide general surgeons with a broad overview of what is currently known about adhesions, the cellular and molecular events that are involved in their formation, the latest research developments in this area and the current available methods of prevention.

Background

Peritoneal adhesions can be defined as abnormal fibrous bands between organs or tissues or both in the abdominal cavity that are normally separated. (1-3) Adhesions may be acquired or congenital; however, most are acquired as a result of peritoneal injury, the most common cause of which is abdomino-pelvic surgery. (4) Less commonly, adhesions may form as the result of inflammatory conditions, intraperitoneal infection or abdominal trauma. (4)

It is estimated that 93% to 100% of patients who undergo transperitoneal surgery will develop postoperative adhesions. (5) The extent of adhesion formation varies from one patient to another and is most dependent on the type and magnitude of surgery performed, as well as whether any postoperative complications develop. (6) Another surgical factor that has been shown to contribute to adhesion formation is intraperitoneal foreign bodies, including mesh, glove powder, suture material and spilled gallstones. (7) Fortunately, most patients with adhesions do not experience any overt clinical symptoms. For others, adhesions may lead to any one of a host of problems and can be the cause of significant morbidity and mortality. (8)

Adhesions and small bowel obstruction (SBO)

Intraabdominal adhesions are the most common cause of SBO in industrialized countries, accounting for approximately 65% to 75% of cases. (5) There is a wide range of values reported in the literature for the risk of developing adhesive SBO after transperitoneal surgery, depending on the series of patients, how they were evaluated and the types of surgical procedures performed. In general, procedures in the lower abdomen, pelvis or both and those resulting in damage to a large peritoneal surface area tend to put patients at higher risk for subsequent adhesive obstruction. (4) It is estimated that the risk of SBO is 1% to 10% after appendectomy, (9,10) 6.4% after open cholecystectomy, (9) 10% to 25% after intestinal surgery (11,12) and 17% to 25% after restorative proctocolectomy (IPAA). (13-16)

The relation between postoperative adhesions and intestinal obstruction is not a new concept. In 1872, Thomas Bryant described a fatal case of intestinal obstruction caused by intraabdominal adhesions that developed after removal of an ovarian tumour. (17) Since Bryant's report, a significant amount of time and money has been invested into research on intraabdominal adhesions, with a primary focus on the development of methods to prevent their formation. Despite substantial work in this area, little progress has been made; to this day, no clinical standard exists for any preventive measure, either surgical or pharmacological, to control the formation of postoperative adhesions. (4)

Other complications of adhesions

SBO is probably the most severe consequence of intraabdominal adhesions, but it is not the only one, and the adverse effects of adhesions are not limited to the gut. (4) For example, in the gynecological literature, it has been found that adhesions are a leading cause of secondary infertility in women (responsible for 15%-20% of cases) (18) and, although controversial, there is evidence to suggest that they may be a cause of longer-term abdominal and pelvic pain. (19) For patients with chronic renal failure, adhesions may make peritoneal dialysis impossible, and their presence may preclude the use of intraperitoneal chemotherapy in those patients who are candidates. (4,6) For general surgeons, the presence of adhesions often makes reoperative surgery difficult and may increase the complication rate of the intended surgical procedure. (20) In the current era of advanced laparoscopic surgery, adhesions have taken on an even greater significance, frequently making laparoscopic approaches more difficult and, in some cases, entirely impossible. (4) Even with open reoperative surgery, extensive adhesiolysis is often necessary to ensure adequate exposure, not uncommonly resulting in prolonged operating times, increased blood loss and other complications. (4,20,21) Inadvertent enterotomy is probably the best recognized complication of adhesiolysis, with an incidence of approximately 20% in reoperative surgery. (20) These cases result in a poorer outcome for the patient, with prolonged hospitalization and a higher incidence of intensive care unit admissions. (20)

Socioeconomic burden of adhesive SBO

The consequences of postoperative adhesion formation have become a significant burden socioeconomically, and the treatment of adhesionrelated disease uses a significant portion of health care resources and dollars. (8) From a large-scale epidemiological study in Scotland, for example, 5.7% of hospital readmissions over a 10-year period were found to be directly related to adhesions, and 3.8% of these admissions required operative management. (8) In 1994, the estimated financial impact for direct patient care owing to adhesion-related disorders in the United States was US$1.3 billion. (22) In Sweden, it is estimated that the health care burden owing to adhesive disease reaches $13 million annually. (23) As the cost of health care continues to escalate and the number of patients requiring surgical care increases with the aging population, the financial burden of adhesions will continue…