Renal Venous Anatomy in 192 Human Kidneys: Morphometry, Hilar Topography, and Anatomical Variants

Renal venous anatomy is relevant to nephrectomy, living-donor evaluation, and retroperitoneal surgery. Classical descriptions often present a single renal vein on each side, whereas published series show that additional veins, retroaortic and circumaortic courses, and variable hilar tributaries are common. This study describes formation patterns, morphometry, and variants in four separate, non-overlapping methodological series of surgical specimens and imaging examinations, with particular attention to the termination of the posterior primary venous branch, the types of venous anastomosis, and the relation of the vein to the artery at the hilum. We examined 192 adult human kidneys (93 right, 99 left) in four separate methodological series, with no kidney examined by more than one technique: anatomical dissection of nephrectomy specimens (n = 64), methacrylate injection and corrosion casting of nephrectomy specimens (n = 93), contrast-enhanced CT angiography (n = 23), and barium injection with radiography of nephrectomy specimens (n = 12). The kidney was the unit of analysis. Because some right and left kidneys may have originated from the same individual and the pairing structure could not be reconstructed, right- and left-sided findings are reported descriptively, without inferential side comparisons. Each feature was analysed only in the kidneys in which it could be assessed. The four techniques differ in their ability to detect small tributaries and anastomoses, and frequencies pooled across methods are descriptive. Among 122 kidneys assessed for hilar formation, the renal vein was formed of two primary trunks in 76/122 (62.3%; 95% CI 53.4-70.4), three trunks in 34/122 (27.9%), and four trunks in 12/122 (9.8%). The confluence was assessed in 110 kidneys and was intrasinusal in 40/110 (36.4%), juxtahilar in 34/110 (30.9%), and extrarenal in 36/110 (32.7%). A posterior primary venous branch was present in 56/122 (45.9%): 19/50 right (38.0%) and 37/72 left (51.4%); it joined the already formed main trunk in 32/56 and took part in the confluence in 14/56. In 90 kidneys the main vein lay anterior to the artery in 42/90 (46.7%). In the descriptive morphometric summary of 78 veins, mean length was 6.9 cm on the left (range 4.8-12.5) and 2.9 cm on the right (range 1.5-5.5). At least one venous anastomosis was recorded in 77/192 kidneys (40.1%; 95% CI 33.4-47.2; pooled across methods): 45/93 right (48.4%; 95% CI 38.5-58.4) and 32/99 left (32.3%; 95% CI 23.9-42.0). Multiple renal veins were identified in 16/116 assessable kidneys (13.8%), including 14/52 right (26.9%) and 2/64 left (3.1%). A retroaortic left renal vein was seen in 2/42 assessed left veins (4.8%), and a complete circumaortic ring in one left specimen. The renal vein was often formed of more than one primary trunk, a posterior branch was present in about half of the kidneys assessed, and multiple veins predominated on the right, in line with previous surgical and imaging series. The more specific contributions of this material are the posterior-branch termination map, the classification of anastomosis types, and the vein-artery counts at the hilum. The study is anatomical and descriptive. It does not measure surgical outcomes and does not show that additional venous imaging is required in every patient.