Topography and Composition of the Iliolumbar Veins in a South African Cohort: Implications for Spinal Surgery

STUDY DESIGN: A descriptive cross-sectional study of the anatomical variations, morphometry, and histology of the iliolumbar veins (ILVs). PURPOSE: This study aimed to describe the anatomical variations of the ILVs and determine their tissue composition in South African cadavers of European descent. OVERVIEW OF LITERATURE: A safe anterior surgical approach to the L4/L5 intervertebral disc space requires understanding the anatomy of the ILVs. Limited understanding of ILVs and their variations may lead to inadvertent avulsion of veins with subsequent hemorrhage and damage to the adjacent nerves intraoperatively. Variations in ILVs are population specific, but such reports are limited in the South African population. METHODS: Eighty-nine adult cadavers were dissected to reveal ILV patterns. The variations (origin, course, and drainage pattern), morphometries, and topography of the ILVs were studied. A total of 19 (10 proximal, nine distal) ILVs were processed for hematoxylin and eosin, Masson’s trichrome, and Verhoeff’s histological staining to determine the tissue composition. RESULTS: The ILVs were identified in 100% of the cases, and 45% of the ILVs were anastomosed to each other bilaterally. The right-side ILVs terminated into the posterior surfaces of the iliac vessels (p=0.001), whereas the left-side ILVs terminated into the lateral surfaces (p=0.001). The left-side proximal ILVs had higher elastic fiber composition (p=0.030). The ratio of the ILVs’ elastic fibers to collagen fibers was 1:9, and 61% of the cadavers exhibited type 1 ILV pattern. Moreover, 42% of the ILVs were at the S1 vertebral level with 31% lying between L4 and L5 spinal nerve roots. The obturator nerve coursed anteriorly to the ILVs in 96% of cases. CONCLUSIONS: The ILV variations described for South Africans present new additional patterns, such as bilateral anastomosis and laterality of the terminal drainage. The ILVs have more collagen fibers than elastic fibers, predisposing them to avulsion during surgical retraction. The identification of all the ILVs is crucial to minimize inadvertent hemorrhage and damage to adjacent structures.