Horseshoe kidney may be classified into three groups based on: Morphological appearance of fusion, site of the fusion, ans vascular supply or angiographic appearance of the vessels.
Horseshoe kidney classification
Hydronephrosis classification
Mannheim's Peritoneal index score 
Acute tubular necrosis classification
Horseshoe kidney physical examination
Cystic nephroma physical examination
Kidney stone classification scheme
Horseshoe kidney epidemiology and demographics