Horseshoe kidney, also known as ren arcuatus (in Latin), renal fusion or super kidney, is a congenital disorder affecting about 1 in 500 people that is more common in men, often asymptomatic, and usually diagnosed incidentally. In this disorder, the patient's kidneys fuse together to form a horseshoe-shape during development in the womb. The fused part is the isthmus of the horseshoe kidney. The abnormal anatomy can affect kidney drainage resulting in increased frequency of kidney stones and urinary tract infections as well as increase risk of certain renal cancers.