Parastomal hernia prevention guidelines: methodology and limitations

Stavros Athanasios Antoniou^*

• Papageorgiou General Hospital, Thessaloniki, Greece

INTRODUCTION The European Hernia Society (EHS) Guidelines published in 2023 provide an update summary of best available evidence on the prevention of parastomal hernias [1]. In these guidelines, the panel provided a conditional recommendation to use a mesh in patients with an end colostomy and fair life expectancy, and a strong recommendation to use a mesh in patients at high risk to develop a parastomal hernia; including a history of abdominal wall hernia, connective tissue disorder, obesity, or patients who are likely to be treated with chemotherapy. Previous guidelines of the same Society published in 2018 had issued a strong recommendation across patients with an end colostomy [2]. Studies conducted around the time of the most recent guideline publications, examining the use of prophylactic mesh in Europe, indicate that while the proportion of surgeons employing prophylactic mesh is rising, adherence to the recommendations remains very low [3 – 5]. The reasons behind this have not yet been studied systematically and in depth. SUMMARY OF THE DATA The evidence comprised 12 randomized controlled trials, 3 of which provided long-term follow-up data [6]. Summary analyses indicate: •Prophylactic mesh and standard end colostomy have a similar risk of major perioperative complications (Clavien-Dindo ≥3). •Patients with a prophylactic mesh have on average a 67% lower risk of a parastomal hernia in the long run. In other words, 32% of patients without mesh will develop a parastomal hernia, against a 11% of patients with mesh. •Patients with a prophylactic mesh have on average a 82% lower risk of surgery for parastomal hernia compared to patients without mesh – or 2% versus 5%, respectively. •There is no difference in quality of life. LOOKING BEYOND THE DATA These data come from randomized trials, which are known to provide a rigorous assessment of postoperative outcomes [7]. Some of the studies have used imaging studies to assess the presence of a parastomal hernia. Results of studies using clinical, or a combination of clinical and radiological assessment did not differ. Furthermore, meta-regression analyses indicated a more pronounced effect with increasing duration of follow-up [8]. In other words, prophylactic mesh appears to prevent, but also to delay the occurrence of a parastomal hernia in patients who will develop it. In clinical practice, surgeons that use a prophylactic mesh for both hernia prevention but also for the treatment of parastomal hernias, observe small recurrences which infrequently incur practical problems with abdominal wall function, esthetics, or application of stoma bags. This contrasts with the frequently encountered complicated bulgy parastomal hernias without prophylactic mesh. Reoperation in patients with a prophylactic mesh and parastomal hernia recurrence is a rather rare scenario, and when this is necessary, resection of the stoma does not go far beyond what would be resected when revising a typical colostomy. THE ISSUE OF PATIENT-CENTERED SURGERY A key feature of modern guidelines is that they bring the patient perspective at forefront. Patient preferences are the primary factor that drives clinical practice [9]. In line with Grading of Recommendations, Assessment & Evaluation (GRADE) and Guidelines International Network (GIN) guideline development standards [10, 11], the most recent EHS guidelines involved a diverse panel of field surgeons, researchers, stoma care nurses, methodologists, systematic reviewers, statisticians and patient partners – specifically, patients with lived experience of colorectal resection with an end colostomy. The panel of surgeons, stoma care nurses and patient partners were presented the evidence, and recommendations were based upon the patient perspective. The panel was asked: If you were a patient about to have an end colostomy, and you were informed that: •you would have a risk of 32% to have a parastomal hernia without a mesh and 11% with mesh, •you would have a risk of 2% risk of surgery for parastomal hernia with mesh, versus 5% without mesh, •and no difference in other key endpoints, which management option would you prefer? If almost all patients would opt for a prophylactic mesh, a strong recommendation is warranted. If most patients would prefer a prophylactic mesh, but a non-negligible proportion would not, then a conditional recommendation suggests that management options should be discussed with the patient. In the EHS parastomal hernia prevention guidelines, panel members unanimously agreed that there would be minimal variation in patient preferences, hence they would support a strong recommendation. Nevertheless, we opted to provide a more conservative set of recommendations, specifically a strong recommendation for high-risk patients, and a conditional recommendation for the average and low-risk patients. The reasons are outlined below. LIMITATIONS OF THE EVIDENCE The body of the evidence is straightforward with regards to the direction of the effects, in spite of single randomized trials and observational studies indicating no effect [12–15]. It is well known that individual studies are prone to type II statistical error (that is, false negative results, because the sample size is small to detect an actual effect) [16]; they do not reflect practice variation, rather than practice of one or few participating institutions [17]; and frequently have methodological limitations, especially detection bias, due to higher intensity of and different patterns of follow-up in patients receiving the intervention [18, 19]. Furthermore, they typically include a subset of patients from the wider patient population, usually healthier patients with few risk factors [20, 21]. Similarly, previous meta-analyses have not applied rigorous methods to appraise the certainty of the evidence, such as risk of bias assessment at the outcome level, rather than at the study level, sensitivity analyses of studies at low versus higher risk of bias, and rating the certainty using decision anchors [22, 23]. Despite the fact that the evidence is sufficiently robust to support a strong recommendation even for low or average-risk patients, there are conceptual barriers that prevent wide implementation of the recommendations. These are summarized in the evidence-to-decision framework that accompanies the recommendations. First, there is a gap in surgeons’ experience with using a mesh at the stoma site. This becomes more complex if we consider that the most effective site of placing the mesh may be the retrorectus or retromuscolar position. Second, there are concerns among surgeons that the mesh may be infected. Despite robust evidence of similar risks of complications Clavien-Dindo class ≥3, there is a culture of ‘resistance to change’ and it is difficult to be persuasive in shifting long-held clinical practices [24]. Third, there is a growing movement against the use of mesh in several European countries, which has influenced the opinions of some patients [25]. Even if these concerns are not grounded on scientific evidence, patient preferences must still be acknowledged. Shared decision-making between patient and surgeon is essential to ensure informed consent regarding the operative approach. DISCUSSION Bridging the gap between evidence-informed and empirical surgical practice remains a significant challenge. Encouragingly, the new generation of surgeons is more open to questioning established dogmas and embracing change. However, several obstacles must still be addressed to achieve optimal surgical research and practice. Surgical research must follow highest methodological standards Trials and observational studies must provide data on key outcomes, such as major complications, rather than composite outcomes of overall complications. If the distribution of major and minor complications is skewed between the groups, the summary outcome will be misleading. Outcome assessment of both observational and randomized studies must be blinded. This ensures an unbiased assessment of the outcome, both in terms of intensity and methods of follow-up. Furthermore, the patient perspective must be key when measuring outcomes. For example, although radiological assessment is informative, primarily from the research lens, clinical assessment is paramount from the patients’ perspective. Long-term follow-up of key outcomes is essential for the objective evaluation of surgical effectiveness. Substantial evidence indicates that the prophylactic benefits of mesh become more apparent over time, and that small parastomal hernias may have limited impact on patients' well-being. In this context, the publication of short-term follow-up data may offer limited value, as previous short-term studies have often been inconclusive and, at times, potentially misleading. Surgical practice must be contexed and follow research evidence Surgeons must be aware that as high as 41% of patients with an end colostomy will have a parastomal hernia in the long term. This incidence is particularly high, and the beneficial effect of a prophylactic mesh is pronounced because of this high baseline risk. Patients should be informed of the high risk of parastomal hernia in the absence of prophylactic measures, as well as the significantly reduced risk associated with the use of a prophylactic mesh. The relevance of this risk can vary depending on the underlying disease and surgical indication. For example, a patient undergoing proctocolectomy for familial adenomatous polyposis may place considerable importance on minimizing the risk of parastomal hernia. In contrast, for an older patient with stage IV low rectal cancer, the long-term implications of a parastomal hernia may be less clinically significant. A key outcome to be measured in future studies is quality of life, which can be affected by factors that are not always well captured, such as the size of the parastomal hernia or difficulties in applying the stoma bag. Surgical dogmas are evolving, albeit more slowly than warranted. Innovations, such as minimally invasive techniques which proved the safety of simple ligation of the appendix, are driving this shift. The use of synthetic meshes is becoming more accepted even in clean-contaminated and contaminated fields [26]. History has shown that delayed adoption of well-established research evidence can expose patients to unnecessary risks and complications [27]. Effective communication among surgeons – through conferences, clinical visits, fellowships, and educational courses – plays a critical role in promoting the dissemination and adoption of evidence-informed practices.