In this study, we determined the incidence of parastomal hernia of loop stoma in the laparoscopic era, and identified risk factors for parastomal formation. We also found associations between parastomal hernia and stoma-related complications of peristomal skin disorders, stoma outlet obstruction, and stoma prolapse. These new findings provide important information for performance of optimal laparoscopic surgery. An understanding of risk factors for parastomal hernia is important because this can decrease the incidence of complications, contribute to improved QOL, and reduce medical costs [7-9]. A stoma that was not formed through the middle of the rectus abdominis muscle was found to be a risk factor for parastomal hernia, and a laparoscopic approach was associated with this risk factor.
Well-established risk factors for parastomal hernia after stoma creation include older age, increased BMI, DM, incision size, laparoscopic approach, and presence of other abdominal wall hernias [19,20]. A stoma passing through the rectus abdominis muscle has also been reported to reduce parastomal hernia formation [20,21]. A single study reported a lower hernia rate compared with a lateral pararectus approach, but it is uncertain whether a stoma passing through the rectus abdominis muscle prevents parastomal hernia formation, and European Hernia Society (EHS) guidelines do not indicate a preference for stoma construction at a lateral pararectus location over a transrectus location . However, many surgeons recognize generally that a stoma passing through the rectus abdominis muscle sheath reduces parastomal hernia formation, and this maneuver is performed without a clear basis in creation of a stoma.
A stoma that did not pass through the middle of the rectus abdominis muscle was a risk factor for parastomal hernia formation. The middle of this muscle has the greatest thickness in almost all people, and it is possible that a stoma passing through this point is protecting against parastomal hernia formation into subcutaneous fat in front of the rectus abdominis muscle. High abdominal pressure causes herniation into the weak point of the abdominal wall, including that due to operation scar, parastoma, and the inguinal canal . The stoma site is generally the weakest point, but a stoma passing through the middle of the rectus abdominis muscle may have a lower incidence of parastomal hernia formation because abdominal pressure might uniformly act on the parastomal site, rather than on a limited part of this site, as might occur for a stoma that does not pass through the middle of the muscle. Therefore, a transrectus stoma should be created with passage through the middle of the rectus abdominis muscle.
A laparoscopic approach was found to be associated with formation of a stoma that did not pass through the middle of the rectus abdominis muscle. A laparoscopic approach has previously been identified as an independent risk factor for parastomal hernia, but no randomized trials comparing laparoscopic and open approaches have been performed [19,24]. In stoma creation in a laparoscopic approach, especially for a temporary stoma in laparoscopic rectal surgery, the operation bed is often not flat, but in a head down and right down position, and pneumoperitoneum may remain. This position and pneumoperitoneum causes stoma site dislocation and difficulty passing the stoma through the middle of the rectus abdominis muscle because of changes in the preoperative stoma site marking and rectus abdominis position. Therefore, a laparoscopic approach may be associated with a stoma that does not pass through the middle of the rectus abdominis muscle, and might be a potential risk factor for parastomal hernia formation.
We also found that parastomal hernia was associated with peristomal skin disorders, as also shown in several other studies [20,25,26]. This may be due to frequent pouch leakage caused by parastomal hernia, which can induce damage to peristomal skin [20,27]. However, severe peristomal skin disorders were not associated with parastomal hernia. An association between parastomal hernia and stoma prolapse has also been shown previously [28,29], and in the present study, the incidence of stoma prolapse in cases with parastomal hernia was higher than that in cases with no parastomal hernia, but the difference was not significant. In contrast, stoma outlet obstruction was higher in cases with no parastomal hernia, and the fascia size has been associated with stoma outlet obstruction and parastomal hernia . Thus, a shorter fascia incision results in stoma outlet obstruction, and a longer incision is linked to parastomal hernia. Thus, a low incidence of parastomal hernia might decrease peristomal skin disorders significantly, but is not related to severity, and increased stoma outlet obstruction may cause more severe problems for patients.
This study had several limitations. First, it was a retrospective study at a single institution in Japan and the number of patients was small. Second, the follow-up period associated with hernia formation was not constant and the exact time of the onset was unclear. Time frame has been reported to be an important risk factor for parastomal hernia . However, in the present study, pre- and perioperative factors, but not postoperative factors, were examined as potential risk factors for parastomal hernia. Third, we did not investigate the severity of parastomal hernia, but this complication, especially when detected only by CT, did not affect QOL and financial costs. Further analysis in a larger sample size including cases with greater severity and using the diagnosis date of stoma-related complications is therefore needed to clarify the associations between risk factors and stoma-related complications, including parastomal hernia.
In conclusion, this study revealed that a stoma that does not pass through the middle of the rectus abdominis muscle is a risk factor for parastomal hernia, and that a laparoscopic approach is associated with this risk factor. Thus, a laparoscopic approach might be a risk factor for parastomal hernia. Further studies in more patients and with different severities and durations of stoma-related complications, including parastomal hernia, are needed to define these associations with certainty.