Associations between kidney position and surplus renal arteries in horseshoe kidney: case report and analysis.

We report the anatomical findings of a case of horseshoe kidney, and analyze the associations between kidney position and surplus renal arteries in horseshoe kidneys found in Japanese autopsies in the past. The horseshoe kidney of our case fused at the lower poles of the original kidneys. Its right and left upper poles were at the middle region of the first and second lumbar vertebrae, respectively. The kidney was supplied by eight arteries. Our analysis of the correlation between the ascent of a horseshoe kidney and the number of surplus arteries found no significant association. However, there was a significant association between the region of the kidney where the surplus arteries entered and the location where they diverged from the aorta. Therefore, the ascent of a horseshoe kidney is not necessarily arrested because of the existence of many surplus arteries. After a horseshoe kidney partially ascends, the arteries which might become normal renal arteries are generated. In our case, we observed large splenomegaly, and noted that the left upper pole was the lowest compared with the horseshoe kidneys in the past autopsy reports. We suggest it is necessary to consider additional influences that determine the position of a horseshoe kidney.