Fleshman 2013.

Methods	Randomised trial. Block randomisation using 160 equally weighted blocks of 2 treatments with a blocking factor of 4
Participants	113 (mean age = 60 years, +/‐ 14 years (1 SD)) Male 59:54 Female
Interventions	In the experimental group (n = 49), a 6 x 6 cm or 8 x 8 cm porcine‐derived acellular dermal matrix was inserted between the anterior and posterior rectal sheath, with a cruciate incision in the centre. The control group (n = 53) had a traditional end colostomy/ileostomy in the same position.
Outcomes	The presence of a parastomal hernia was assessed using clinical examination, or CT scan if there was clinical doubt. Other outcomes included safety and stoma‐related quality of life.
Length of Follow Up	Maximum 24 months
Notes	Data from 12 months' follow‐up sought but not received from author. 5 participants from the control group and 7 participants from the intervention group lost to follow‐up.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomised trial (1:1 randomisation)
Allocation concealment (selection bias)	Low risk	Quote: "Randomization was conducted centrally by using 160 equally weighted blocks of 2 treatments with a blocking factor of 4. Patients and staff members who performed the assessments were blinded as to assignment" Comment: Probably occurred
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Comment: Not possible to blind the surgeon as to which procedure was being performed
Blinding of outcome assessment (detection bias) All outcomes	High risk	Quote: "of the 13 hernias that occurred, 11 were confirmed by CT scan and 2 were confirmed operatively." Comment: No standardised, predefined way of assessing the presence of a PH, although assessors were blinded to the procedure performed
Incomplete outcome data (attrition bias) All outcomes	Low risk	24‐month PH data on 45 of 113 participants not included in the final analysis. The author has adequately justified participants excluded in the final analysis.
Selective reporting (reporting bias)	Low risk	Comment: No selective reporting identified.
Early Stopping	Low risk	Comment: Sample size calculation given. No early stopping reported.