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Purpose: Parastomal hernia (PSH) is a common and often burdensome stoma complication. Surgical repair carries high morbidity and mortality. Hence, prevention of PSH formation would be ideal, which requires better understanding of risk factors. We aimed to examine the role of abdominal rectus muscle (ARM) thickness and its postoperative atrophy in PSH pathogenesis. We hypothesised that a thin ARM upon stoma creation is a risk factor for PSH development, and that patients developing PSH show a higher degree of postoperative ARM atrophy compared to patients without PSH.

Methods: Radiological bilateral ARM measurements on 205 patients, before and after rectal cancer surgery with Hartmann’s procedure or abdominoperineal resection, among Swedish patients recruited retrospectively from the Swedish Colorectal Cancer Registry. Hypotheses were tested using t-test and multivariable logistic regression.

Results: Patients developing PSH had a greater degree of ARM atrophy than hernia-free patients (-3.2 mm [-36.4%] vs. -1.6 mm [-18.2%]; p = 0.002). Postoperative ARM atrophy (OR 1.17; 95% CI 1.05–1.31, p = 0.006), body mass index (OR 1.15; 95% CI 1.06–1.24, p < 0.001) and laparoscopic approach (OR 2.60; 95% CI 1.27–5.31, p = 0.009) were independent risk factors for PSH in the multivariable model. Preoperative anteroposterior thickness of the ARM was not found to be a risk factor.

Conclusion: Patients developing PSH had a more pronounced atrophy of the ipsilateral ARM than patients without PSH. A thinner ARM preoperatively did not increase the risk for PSH. Further research should focus on what causes postoperative ARM atrophy.