Horseshoe kidney causes

During early fetal development, the kidneys are developed in the pelvis and then later they move upwards in abdomen. Sometimes due to unknown reason the lower ends of both kidneys fuse together forming a ‘U’ shaped single kidney.

Although the exact cause is unknown, but there are two main theories.^[1]

• One theory suggests that during the fifth week of fetal development both kidneys are so close together leading to mechanical fusion of lower end of both kidneys. This kind of fusion creates the fibrous isthmus because it is made of connective tissue.
• Other theory suggests that posterior nephrogenic cells, which are the cells responsible for formation of kidney, migrate to wrong place leading to joining of lower end of both kidneys. This time it is called parenchymal isthmus because it is made of kidney cells.

The horseshoe kidney remains lower in abdomen than normal kidneys due to blockade caused by inferior mesenteric artery during its movement from pelvis to abdomen in 7-8 weeks of development.

Template:WH Template:WS