Prophylactic mesh placement is not sufficient: what should we do to prevent parastomal hernia associated with ileal conduit?

Ileal conduit (IC) remains the gold standard of urinary diversion after cystectomy, despite being introduced in 1950 by Bricker (1). Parastomal hernia (PSH) is one of the representative long-term complications. Although most cases are asymptomatic and can be managed conservatively, PSH can induce not only cosmetic and functional problems, but also life-threatening conditions requiring emergent repair.

Djaladat et al. reported the results of their randomized controlled trial (RCT) evaluating the efficacy of prophylactic biological mesh placement as a preventive strategy for PSH formation associated with IC (2). The primary end point was time to radiological PSH. The study did not demonstrate a statistically significant prophylactic effect of biological mesh in preventing radiological PSH. On the other hand, an RCT conducted by Liedberg et al. demonstrated that prophylactic synthetic mesh placement significantly reduced the incidence of clinical PSH, which was the primary endpoint of the study (3). However, the incidence of radiological PSH was not significantly reduced by the mesh. After all, in both studies, the incidence of radiological PSH was 19% to 38% within 2 years irrespective of mesh use, which is comparable to the rates in non-mesh procedure reported in other studies (4-6). Some investigators have pointed out that the efficacy of preventive mesh placement might become significant with a longer follow-up in the study by Djaladat et al. (7,8). Median follow-up time of patients without an event was 24 months (interquartile range, 17–26 months) in this study. On the other hand, according to other retrospective reports, the majority of PSH cases developed within two years after the operation (4-6,9,10), suggesting that extending the follow-up period may not change the negative results of the study.

Surgical procedures for stoma creation have been reported as risk factors for PSH, along with patient characteristics such as body mass index (BMI), preoperative malnutrition, and a history of laparotomy (6). Then, modification of the surgical procedure is feasible to prevent PSH. Prophylactic mesh placement has been considered a promising approach, but the results of two RCTs suggest that the effectiveness of mesh usage itself is limited. We should consider other approaches to modify the surgical procedure to prevent PSH formation. Several studies, including ours, indicate that the size of the abdominal muscle defect impacts on PSH development (5,6,11), although this issue was not addressed in the two RCT reports. In the two RCTs, the size of the incision on the mesh used for the keyhole technique was not reported. It is difficult to determine the appropriate size because the size of the ileum and thickness of the mesenteric fat are different among individuals. Needless to say, too small a passage may cause ischemia of the ileal segment. The cutoff value of the size in predicting PSH varied among studies. Hussein et al. reported that a size greater than 30 mm was associated with the future development of PSH (5), whereas our study identified 24 mm as the optimal cutoff (6). Regardless, intervention regarding the size of passage for IC has the potential to reduce the incidence of PSH. It is definite that we should take care not to create an abdominal muscle defect that is too large. Although “two fingerbreadths” has been widely used as an indicator for the passage of the IC (4,9), the diameter of two fingers varies among surgeons. Among 17 surgeons at Department of Urology, Sapporo Medical University, the mean size was 25 mm (range, 17 to 33 mm; data not shown). Therefore, certain standards should be established to determine the size of the passage for the IC.

Recently, we developed a novel procedure for the creation of an IC stoma aimed at preventing PSH, based on the results of our previous study (12). The procedure included the following three major points: (I) the passage of the IC in the abdominal wall was created with a diameter of at most 2.4 cm unless it was constrictive; (II) a vertical incision was made in the posterior rectus sheath and peritoneum, 2 cm lateral to the stoma center, creating a short tunnel between the abdominal muscle and peritoneum with the posterior rectus sheath; and (III) the IC was separately fixed to the anterior and posterior rectus sheaths along with the peritoneum. Fixation to the anterior rectus sheath was performed using 6–8 interrupted absorbable sutures placed externally through the abdominal wall. In contrast, fixation to the posterior rectus sheath and peritoneum was achieved using 3–4 interrupted absorbable sutures via the midline incision, creating a short extraperitoneal route for the IC. With this non-mesh prophylactic technique, the incidence of PSH was significantly reduced compared to the conventional procedure (4.0% vs. 23.2% at 2 years). The same outcomes may not be expected in patients with a higher BMI, because this series included Japanese patients with a relatively low BMI (mean 23.4 kg/m²). Greater size of the passage for the IC may be appropriate for patients with large physiques. Moreover, effects of fixation of the IC to the abdominal rectus sheath is unknown, because its preventive effect against PSH formation considered negative (10,13). Despite these limitations, the results of our study are promising. The additional operative time is similar to or shorter than that of prophylactic mesh technique. Furthermore, non-clinical basic research by Kanabolo et al. indicated that a linear facial incision and suture reinforcement may be effective in preventing PSH (14). These results suggest that there is room for improvement in surgical procedures to prevent PSH development aside from prophylactic mesh. Although the standardization of the surgical procedure is difficult, further prospective randomized studies that consider factors other than mesh usage are warranted.

Acknowledgments

None.

Footnote

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