A SUPERNUMERARY kidney is a fairly common abnormality of the renal tract and may cause no symptoms. The ureter of the supernumerary kidney is usually only doubled in its upper part and a fulllength duplication of the ureter is uncommon. Most supernumerary kidneys are fused with their fellow-a true, free supernumerary kidney is very rare.
Ectopic or extravesical opening of the supernumerary ureter is very rare, and Scott (1944) estimated that about three hundred cases had been reported in the literature in females.
Incontinence is the usual presenting symptom of ectopia of the ureter in females, but in males symptoms may be absent, or may be of obstructive or infective nature, and incontinence does not occur.
Fused Supernumerary Kidney.-The fused supernumerary kidney is one of the commonest renal abnormalities and its main features have been excellently summarized by Nation (1944) as follows :- I . Incidence : During intravenous pyelography 2.7 per cent of cases presented duplication of the renal pelvis on one or both sides. These investigations were on selected patients, and in an unselected series of post-mortem examinations the frequency was I in 16,000 bodies.
-
Sex : Females were affected 27 per cent more often than males.
-
Unilateral duplication is ten times commoner than bilateral.
-
Age at onset of symptoms is usually above 30 years.