Congenital anomalies of the kidney relate to number, form and position of the kidneys.
While bilateral renal agenesis is incompatible with survival, unilateral renal agenesis, or the failure of one kidney to form, is compatible with a normal life, provided there is a normal contralateral kidney. It represents a rare but well recognised urological situation. There are no symptoms or signs relating unilateral renal agenesis. The diagnosis is usually made by way of a chance finding during routine investigation of the urinary tract or, occasionally, through ultrasound scanning of the abdomen for non-urological reasons. Care is required in the interpretation of such investigations, since often the ‘shape’ of a kidney can be seen in the loin as relating to the normal fat and fascial tissues of the loin, notwithstanding the absence of the kidney. Proof positive of unilateral renal agenesis is obtained by endoscopic examination of the bladder and attempted retrograde studies of the ureter. In unilateral renal agenesis, the related ureter is either absent or under-developed.