Many of the initial studies on adhesion development were comprised of patients with infertility, but more recent observations have been extended to women without infertility and to men. Studies have covered patients undergoing colectomies, for instance, as well as neonates undergoing cardiothoracic procedures.
In a recent review article on adhesion prevention and reduction, members of an interdisciplinary consensus conference stated that adhesions develop after “nearly all” abdominal and pelvic procedures performed through either standard laparotomy or laparoscopic approaches. With respect to gynecologic surgery, they point out, research has shown that the most common site for postsurgical adhesion development is the ovary (Surg. Innov. 2010;17:183–8).
Consequences
Pelvic adhesions are a well-recognized cause of infertility, contributing to up to an estimated 40% of the cases of infertility in women. Adhesions are also a leading cause of bowel obstruction and a significant cause of chronic or recurrent pelvic pain.
The contribution of pelvic adhesions to chronic pelvic pain is not completely understood. Adhesions may be the cause of pain in some women, and in other women, an incidental finding that is not contributing to pain. In patients who have endometriosis as well, the question remains as to the contribution of endometriosis per se, or adhesions, to the pain. Endometriosis can cause adhesions and chronic pelvic pain, presumably through the cyclic generation of inflammatory molecules.
The relationship between chronic pain and adhesions is further complicated by ensuing questions about the efficacy of adhesiolysis. The two randomized trials that have thus far examined the role of adhesiolysis in the reduction of chronic pelvic pain failed to demonstrate a significant improvement in pain after adhesiolysis; however, the high failure rates after follow-up may be due to adhesion reformation and de novo adhesion formation (Fertil. Steril. 2004;82:1483–91). Performance of more randomized comparisons in the future may yield improved outcomes when adhesiolysis is paired with postprocedure use of anti-adhesion adjuvants.
Despite the uncertainties, multiple studies support the current estimation that adhesions cause or significantly contribute to chronic pelvic pain in up to 30% of women with the problem. As the Ovarian Adhesion Study Group noted in one of its reports, adhesions have been reported as a primary cause of chronic pelvic pain in 13%-36% of women, depending on the study (Obstet. Gynecol. 1995;86:335–40). Economic analyses also have quantified the impact of adhesion-related hospital readmissions. A study done in the United Kingdom, for instance, concluded that 6% of all hospital readmissions in patients who had undergone abdominal or pelvic surgery were directly related to adhesions (Lancet 1999;353:1476–80).httother report on hospitalizations for lower abdominal adhesiolysis in the United States estimated that in 1988, the cost of adhesions stemming from gynecologic procedures alone was almost $1.2 billion. This estimate did not include outpatient and indirect costs (Surg. Gynecol. Obstet. 1993;176:271–6).
Why, How Adhesions Develop
Our current understanding is that adhesions develop as a result of injury to and devascularization of the peritoneum, and the subsequent inflammatory response and peritoneal wound healing process. Tissue hypoxia triggers a cascade of intracellular responses that, in combination with the fibrinous collection of blood and serosanguinous fluid at the tissue surface, may result in adhesion development.
In the initial postsurgical period, either overt bleeding or oozing may occur at the site(s) of tissue injury, forming clots. In combination with serosanguinous fluid, which may leak from damaged peritoneal surfaces, a fibrinous mass thus develops at the surgical sites and sites of tissue injury. This represents an initial step in peritoneal repair.
When surrounding tissue is normal and there is a sufficient amount of plasminogen activator present in the peritoneum — and when numerous other events and conditions are optimal — the resulting fibrinous mass can be degraded. As that occurs, and tissue healing continues, fibroblasts are recruited to the surface of the injury site from underlying tissues.
If the fibrinous mass is no longer present, fibroblasts “stop” at the tissue surfaces, and become covered by mesothelial cells which line the peritoneal surface as the process of remesothelialization occurs. This process appears to be initiated within hours after surgery and is generally believed to be completed in 3–5 days. (In such instances, healing would have occurred without adhesions, although subperitoneal fibrosis may have occurred.)
Various hypoxia-driven responses, however, such as a reduction in plasminogen activator activity, can cause the fibrinous mass to persist during the healing process, before remesothelialization occurs. In this case, fibroblasts migrate not only to, but through, the injury site, and into the persisting fibrinous mass. This is subsequently followed by deposition of collagen, fibronectin, and other extracellular matrix materials — creating the beginnings of a true adhesion.