<unk> s are normally located in the retroperitoneal space between the T12 and L3 vertebrae after ascending from the pelvis during development to rest underneath the adrenal glands. In patients with this condition, the<unk>  ascent is commonly arrested by the inferior mesenteric artery due to the central fusion of the<unk> s. However, this is present in only 40% of cases, and, in 20% of cases, the fused<unk>  remains in the pelvis. Its ascension may also be restricted by its own renal artery. Additionally, during normal development, the<unk> s undergo a 90 degree medial rotation while ascending. However, due to the renal fusion, this rotation is impaired resulting in abnormal placement of the ureters. This in turn can lead to urinary stasis and drainage issues. Furthermore, approximately 70% of<unk> s in normal individuals are supplied by a single renal artery with the remaining 30% having embryonic collateral or accessory arteries. With<unk> s, the majority are supplied by derivatives of the abdominal aorta or common illiac arteries depending on the final position of the<unk> s.
Horseshoe kidney
Page kidney
Multicystic dysplastic kidney
Ectopic kidney
Crossed renal ectopia
Supernumerary kidney
Medullary sponge kidney
Renal segmental hypoplasia