The unilateral small kidney with special reference to the hypoplastic kidney. Review of the literature and authors' points of view.

Abstract

In connection with the publication of two papers on the clinical features and on the functional pattern in our material of patients with renal hypoplasia, an effort has been made to review the literature dealing with this condition. The frequency of unilateral small kidneys has been found to be about one in 500 autopsies. A kidney may be small because of congenital hypoplasia or pyelonephritic shrinkage or as a combination of both. The hypoplastic kidney is probably predisposed to infections. There are principally two kinds of hypoplastic kidneys: those with remnants of embryological development and those without. Kidneys without remnants of embryological development contain as a rule few calyces but may otherwise be of normal shape and of ordinary microscopical appearance. Primitive ducts and cartilage have been considered to be definite signs of embryological misdevelopment. Colloid cysts resembling thyroid tissue may probably be found both in hypoplastic kidneys without superimposed infections and in atrophic kidneys due to pyelonephritis. Radiologically the hypoplastic kidneys may be found to contain few calyces and the minor calyces may arise directly from the pelvis. The contralateral kidney is often enlarged. Good excretion of contrast medium favours the diagnosis of hypoplasia and makes pyelonephritic shrinkage less plausible. The artery of the hypoplastic kidney is described to be uniformly narrow in its whole length, while in pyelonephritis the mouth of the artery (the point where the renal artery arises from the aorta) has as a rule normal width, although the rest of the artery may be narrow. Split function tests have shown a good concentrating ability in hypoplasia in relation to the reduction in glomerular filtration rate, especially when compared with that in chronic pyelonephritis. Local pain, hypertension and urinary tract infections are common manifestations in renal hypoplasia. Blood pressure may be normalized after nephrectomy. Hypertension seems to be the most dangerous feature. If the blood pressure can be satisfactorily controlled, the prognosis in unilateral renal hypoplasia seems to be rather good.