Fistulotomy combined with sphincteroplasty remains a standard surgical approach for selected cases of primary simple fistula-in-ano. However, the extent to which modifiable and metabolic risk factors influence postoperative healing in this specific population has not been fully clarified. This gap in the literature is particularly relevant in high-volume centers where patient comorbidities are common and surgical outcomes must be optimized.

The objective of this study is to determine whether tobacco use and/or type 2 diabetes mellitus (DM2) predispose patients undergoing fistulotomy with sphincteroplasty for a primary simple fistula-in-ano to poorer postoperative wound healing.

Clinical records of patients who underwent fistulotomy with sphincteroplasty for a primary simple fistula-in-ano were retrospectively reviewed for the period between January 2025 and January 2026. A comparative analysis was performed to assess whether tobacco use and/or a diagnosis of DM2 influenced postoperative healing. Patients were systematically evaluated during scheduled outpatient follow-up visits, where the percentage of wound healing was documented. Statistical analyses were performed using Jamovi software package, version 2.6.45.0

A total of 42 patients were included in this study, of whom 36 (85.7%) were male and 6 (14.3%) were female. The mean age was 48.4 years [standard deviation (SD) 11.1]. All patients (100%) underwent fistulotomy with sphincteroplasty performed by the same surgical team. Of the total, 13 patients (30.95%) had no comorbidities, 9 (21.42%) were chronic tobacco users, 9 (21.42%) had a diagnosis of DM2, and 11 (26.19%) were both chronic tobacco users and diagnosed with DM2. Mean follow up was 2.5 months (1-7 months, SD 1.66). Wound healing was assesed by the same examiner and graded 0–10 (0 being a fresh, bleeding wound and 10 being a 100% healed wound).

A multivariable linear model was constructed to evaluate the effect of smoking status (tobacco use), DM2, and their interaction on wound healing outcomes in a cohort of 42 patients undergoing fistulotomy with sphincteroplasty.
The overall model demonstrated poor explanatory capacity, with an R² of 0.044 and an adjusted R² of 0.000, indicating that only 4.4% of the variability in wound healing outcomes was explained by the included predictors. The model was not statistically significant (F(3,39) = 0.597, p = 0.621).

Analysis of variance (ANOVA) revealed no statistically significant effects for any of the independent variables. Smoking status showed no significant association with wound healing (F = 1.007, p = 0.322, η²p = 0.025), nor did DM2 (F = 0.284, p = 0.597, η²p = 0.007). Additionally, the interaction between smoking and DM2 was not significant (F = 0.064, p = 0.802, η²p = 0.002), suggesting no combined effect of these variables on the outcome.

Parameter estimates demonstrated small effect sizes with wide confidence intervals crossing zero. Smoking was associated with a non-significant positive coefficient (β = 0.095, SE = 0.094, p = 0.322), while DM2 showed a non-significant negative coefficient (β = -0.071, SE = 0.132, p = 0.597). The interaction term between smoking and DM2 also showed no significant effect (β = -0.048, SE = 0.189, p = 0.802).

Overall, these findings indicate that neither smoking status, DM2, nor their interaction were significantly associated with wound healing outcomes in this cohort. However, the low explanatory power of the model suggests that other unmeasured factors may play a more substantial role. Additionally, the relatively small sample size may have limited the statistical power to detect clinically relevant differences.

Identifying factors that predispose patients undergoing fistulotomy plus sphincteroplasty to suboptimal wound healing is crucial to facilitate the development of individualized, patient-centered treatment strategies to ensure optimal therapeutic outcomes.