Location of Anal Dimple and Its Positional Alignment with the Caudal Termination of the Striated Muscle Complex in Patients with Anorectal Malformations

Abstract

Background In children with anorectal malformations (ARM), the midline perineal skin feature known as the anal dimple (AD) is commonly used as a surface landmark to guide surgical placement of the neoanus. The striated muscle complex (SMC), vital for continence, is presumed to align with this dimple and misalignment may lead to poor functional outcome such as incontinence. This study was conducted to find out whether the location of the SMC correlate with AD in patients with ARM.

Methods This cross-sectional study included 30 ARM patients undergoing various anorectal procedures. Intraoperatively, the boundaries of the AD and SMC were marked, and distances between centers (C-C) and lengths of AD (A-B) and SMC (A⸍-B) were recorded using Vernier calipers.

Results Mean age was 16 months and male to female ratio 2:1. Recto-bulbar urethral fistula was predominant in male and vestibular fistula in female. In majority (80%) of the cases, SMC was posterior to AD. Male had more posterior location whereas female had more anterior location of SMC in relation to AD. Distance between the center of AD and center of SMC (C-C⸍) was found higher in the recto-bulbar urethral fistula followed by the recto-vesical fistula in comparison with perineal and vestibular fistula (F= 8.22, p= 0.00). Mean (C-C⸍) displacement was 3.4 mm. Length of AD, SMC and C-C⸍ weakly correlated with each other.

Conclusion The anatomical location of the SMC does not consistently match the AD. Reliance on the AD alone may risk misplacement of the neoanus, suggesting that intraoperative SMC visualization is crucial.  

Journal of Paediatric Surgeons of Bangladesh (2024) Vol. 15 (1 & 2): 3-9