Evaluating risk factors for development of a parastomal hernia: a retrospective matched case-control study

Aim
Identify risk factors most likely to contribute to parastomal hernia development.

Methods
Retrospective matched case-control study using retrospective case note reviews. One public and one private South Australian hospital. Ostomates who underwent stoma formation surgery between 2018 and 2021, and did ('cases', nequivalent50) or did not ('controls', nequivalent50) develop parastomal hernia were matched by ostomy type. Potential parastomal hernia risk factors were identified from the literature and expert opinion to build a case note review tool. Case notes were selected by surgical date from 2018. Analyses were conducted in which univariable logistic regression investigated relationships between potential risk factors and parastomal hernia development. Exploratory subgroup analyses investigated whether relationships between risk factors and development of parastomal hernia differed according to ostomy type.

Results
Patient characteristics were summarised descriptively and by hospital. Statistically significant evidence was found of links between development of parastomal hernia and higher BMI (OR for 5 kg/m2 increase: 1.74; 95% CI: 1.19, 2.76), post-operative infection (OR 2.68; 95% CI: 1.04, 7.33), multiple abdominal surgeries (OR 4.21; 95% CI: 1.18, 19.90), time since surgery (OR >30 months: 0.003; 95% CI: 0.0004, 0.02), and aperture size (OR for 1mm increase: 1.12; 95% CI: 1.02,1.24). Sufficient evidence was not found of expected relationships with factors such as smoking, chemotherapy and/or pelvic radiotherapy, lifestyle and activity factors.

Conclusions
This study contributes to furthering the understanding of the relationships between known risk factors to inform stomal therapy nurses' practice in the prevention of a parastomal hernia. High body mass index, postoperative infection, multiple surgeries, wide diameter of the stoma, and time since surgery of less than 30 months increased the risk of parastomal hernia, other factors did not reach significance probably due to use of an underpowered sample.

Opportunities to repeat this study would further strengthen the necessary evidence of the most important risk factors.