MDCT-based prevalence of anatomically challenging sacral hiatus morphology in adults: implications for procedural safety

Abstract Background The sacral hiatus is the primary percutaneous access point for caudal epidural blocks and other trans-sacral interventions. Its anatomical variability is a known contributor to procedural failure and complications, yet the prevalence of high-risk morphology in living adults remains incompletely characterized. Purpose This study aimed to classify sacral hiatus morphology using multidetector computed tomography (MDCT) in a diverse adult population and to estimate the prevalence of anatomical variations that could complicate percutaneous trans-hiatal access. Methods This retrospective study included 258 adults (142 men, 116 women; mean age 47.2 ± 14.6) who underwent pelvic MDCT imaging for various non-traumatic indications. Two independent radiologists assessed multiplanar reconstructions for apex level, canal dimensions, and hiatus shape. Challenging anatomy was defined by pre-specified criteria: apex at/above S3, canal depth < 3 mm, or absent/irregular hiatus. Results Anatomically challenging features were identified in 34.9% (90/258) of the cohort. The V-shape (38.0%) was most common. A high apex (at/above S3) was observed in 28.4% (73/257 patent cases), with no significant sex difference ( p  = 0.213). Canal depth was ≤ 3 mm in 31.0% (80/258). Based on composite criteria, 34.9% (90/258) had challenging anatomy. Interobserver agreement for dimensional measurements was robust ( r  ≥ 0.893), and for categorical classification, it was substantial ( κ  ≥ 0.669). Conclusions MDCT demonstrates a high prevalence of sacral hiatus variants that can complicate trans-hiatal access. Proactive radiologic identification of these features on routine studies provides valuable pre-procedural intelligence, potentially enhancing safety across anesthesia, interventional pain medicine, and orthopedics.