Seven (quadruple right and triple left) renal arteries and their topological relationship with other branches of the abdominal aorta.

Supernumerary renal arteries are frequently observed, but their developmental origin remains controversial. One hypothesis, the ladder theory, ascribed origins of multiple renal arteries to a segmental array of mesonephric arteries. However, recent studies in both rodents and humans demonstrated evidence against this theory. We describe a rare variation in a Japanese female cadaver exhibiting seven renal arteries encountered during student dissection practice in 2023. On the right side, the main renal artery branched off from the aorta 29 mm below the origin of the superior mesenteric artery. Three additional renal arteries branched off at the level of or below the inferior mesenteric artery. On the left side, two renal arteries branched off at usual high positions, but another branch below the inferior mesenteric artery. In 43 cadavers dissected in 2023, all renal arteries including duplicate type, but except for the present case, arose at high positions near the superior mesenteric artery. Incidence of connection between multiple renal arteries and adrenal and/or gonadal arteries was 78.6% (11 out of 14 kidneys). Importantly, all these connections were observed at high-positioned branches. Combining present results with previous data in literatures revealed the close relationship between high-positional branching and connections with adrenal/gonadal arteries (p = 0.0056), suggesting two factors influencing renal artery development: (1) prenatal, interconnected arteries at high positions, and (2) low-positioned individual branches arising from the aorta during kidney ascent with poor interconnectivity. Arteries involved in these two events might regress with various degrees, leading to diversity in number and connectivity of renal arteries.