Hydronephrosis in childhood : An experimental and clinical study

Abstract: In this thesis the pathophysiology of hydronephrosis due to ureteropelvic junction (UPJ) obstruction was studied. The kidney adapts to obstruction by changes in renal blood flow (RBF) and glomerular filtration rate (GFR). GFR is mainly regulated by the tubuloglomerular feedback (TGF) which acts as a negative feedback between the tubule and glomerular vessels.In earlier micropuncture experiments on rats with partial unilateral obstruction we have found an increase in TGF sensitivity during volume expansion (VE). It has also been shown that the degree of UPJ obstruction could be calculated using a pressure/flow (P/F) study technique.In a first series of experiments, the TGF response to VE in rats with bilateral partial obstruction was examined. A new balance between the kidneys occured, where the diuresis was greatest on the least obstructed side.The RBF was investigated by real transit time ultrasound in two studies. RBF was normal during basal conditions, but became significantly increased during VE in hydronephrotic animals. The response was thromboxane and/or nitric oxide dependent.In a last study, 44 patients with a diagnosis of hydronephrosis were examined with the P/F study technique prior to operation. It was shown that the outflow resistance of the UPJ could be accurately calculated in all cases.It is concluded that the normal adaptation of the kidney to obstruction depends on the presence of a normally functioning contralateral kidney. This adaptation includes a change of the filtration characteristics with is achieved through Tx and NO dependent vasodilatation and probably areduction of the filtration coefficient. It is further concluded that the degree of obstruction can be accurately calculated by a P/F study in patients with hydronephrosis.