Suspected pyelo-ureteral junction obstruction in the fetus: when to do what? II. Experimental viewpoints.

Nowadays the postnatal management of antenatally detected hydronephrosis is much debated. Some authors claim that these cases ought to be operated very early, since there is rapid renal destruction and full recovery may only be achieved during this period. Others claim the opposite and recommend a nonoperative follow-up, provided that renal function is normal, as it is in the majority of cases. If experimental studies are to be used to settle this question, the created obstructions must correspond to human obstructions. That is, be partial and permanent, produced in fetal or newborn animals, preferably be moderate in degree, the diameter should grow in pace with the growing ureter, and be followed for a long period. Only three experimental series fulfil, to some extent, these requirements. In two of them a severe obstruction was produced, which within 5-8 weeks led to reductions by 80-95% in renal blood flow, glomerular filtration and potassium and phosphate excretions, which were in part compensated for and established early. In one study, a moderate obstruction was created which within 9 weeks led to reductions of 10-30% in renal blood flow, glomerular filtration, and potassium excretions, which were in part compensated for. The changes appeared very soon but were not progressive. Release of the obstruction had to be performed very early in order to avoid the lesions. The causes of the renal defects and of the absence of progression are discussed. It is concluded that the majority of human pyeloureteral obstructions are best imitated by a moderate type obstruction. The results do not support any rationale for early correction.(ABSTRACT TRUNCATED AT 250 WORDS)