Introduction Parastomal hernias (PH) have been reported to occur at a rate of 4–48% and it is the most frequent complication to occur as a result of stoma formation. This study evaluated the relationship between abdominal wall aperture (AWA) diameter and colostomy site position relative to the rectus abdominis muscle (RAM) to examine the effect on PH development.
Method A retrospective review of all end colostomies created following abdominoperineal excisions (APE) between February 2006 and November 2014. Those with no post-operative Computed Tomography (CT) imaging were excluded from the analysis. Data including age, sex, curative intent, and colostomy position relative to the RAM and serial AWA diameters on follow up CT imaging were collected retrospectively. The severity of PH was assessed using the Moreno-Matias classification.
Results One hundred and fourteen elective APEs were performed, of which 85 were the subject of this study. Seventy-three (85.9%) had the colostomy created through the RAM, whilst 12 (14.1%) had it lateral to the RAM (LRAM). Median time to first post-operative CT imaging was at 9.2 (0.1–43.6) months in the RAM group compared to 3.9 (0.2–10.6) months in the LRAM group (p = 0.056). The median AWA diameter on the earliest CT image after surgery was 19 (6–45) mm in the RAM group and 26 (15–46) mm in the LRAM group (p = 0.01).
We implemented a linear mixed effect model and found that in the LRAM group the AWA diameter increased on average by 1.5 mm per year (95% CI: 0.5, 2.5), whereas in the RAM group it increased by 1.6 mm per year (95% CI: 0.4, 2.8), after adjusting for age at surgery, gender and other unobserved patient-specific effects. The difference between both groups was 0.013 mm (95% CI: -0.09, 0.11; p > 0.05). The overall difference between the AWA size of the RAM group compared to the LRAM group was 9.6 mm (95% CI: 3.5, 15.6). We found that age increased the AWA size by 0.2 mm per year regardless of colostomy position.
An ordinal mixed effect model was fitted for the PH severity index. There was no significant difference in overall severity (p = 0.21) or rate of change of PH severity (p = 0.59) between both groups (RAM and LRAM).
Conclusion There was a significant difference between median AWA diameter on earliest CT image after surgery in the RAM group compared to LRAM group. AWA diameter increases with time regardless of colostomy position relative to the RAM. There was no significant difference between the rate of AWA progression between colostomies created through the RAM and those created through the LRAM. Furthermore, there was no significant difference between PH severity and colostomy position.
Disclosure of interest None Declared.