Revision 8 for 'Horseshoe kidney'
The kidneys and urinary tract are host to more survivable congenital abnormalities than any other system of the body. Most abnormalities either present early in life with mass, infection or decreased renal function, or remain silent to be discovered incidentally later in life. The most common reasons for discovery of silent cystic and congenital abnormalities of the urinary tract include microscopic hematuria, urinary tract infection, stone formation and investigation of unrelated problems.
The horseshoe kidney is probably the most common of all renal fusion anomalies, occurring in 0.25% of the population. It should not be confused with asymmetrical or off-center fused kidneys, which may give the impression of being horseshoe shaped. The anomaly consists of two distinct renal masses lying vertically on either side of the midline and connected at their respective poles (usually the lower poles) by a parenchymatous or fibrous isthmus that crosses the midplane of the body. Horseshoe kidneys are frequently associated with other congenital anomalies, including skeletal, cardiovascular and central nervous system defects, as well as other genitourinary anomalies such as hypospadias, undescended testes, bicornuate uterus and vaginal anomalies. The male to female ratio is approximately 2:1. The most common associated finding in these patients is UPJ obstruction, which occurs in up to 35% of patients. For many patients, the horseshoe kidney remains asymptomatic, and the horseshoe kidney is an incidental finding during radiological examination. Symptoms, when present, are usually due to obstruction, stones, or infection.