Development of fetal lamb lung and kidney in obstructive uropathy: a preliminary report

Oligohydramnios, whatever the cause, results in lungs that are 'hypoplastic' or at least smaller than normal. The fine structure in such lungs has not been reported previously. Three fetal lambs had both ureters ligated at 60, 72 and 58 days of gestation. They were sacrificed at 117, 143 and 142 days of gestation. The lungs were fixed by tracheal perfusion at 15 mm Hg. Individual lobar volumes were determined, and the lungs were sampled for electron microscopy. Total lung volumes for 2 of the lambs were very close to those previously reported for lungs of equivalent gestation with diaphragmatic hernia. The third lamb had a twin that had been unrecognised at the time of the original procedure. This lamb's lung volumes were normal. The morphological appearances of the lungs at the electron microscopy level are not normal but dramatically different from those previously reported in lambs with diaphragmatic hernia, phrenic nerve avulsion, and fetal tracheostomy. The lungs of the lamb with bilateral ureteric ligation and a normal twin were essentially normal. These preliminary findings point to the need for more studies of lung structure in oligohydramnios/obstructive uropathy models. However, the normal lungs in a lamb with grossly dysplastic kidneys and a normal twin argue against any important renal trophic factor in lung development in the fetal lamb. An interesting sidelight to this investigation was the unequivocal demonstration that early ureteric ligation results in true renal dysplasia in the fetal lamb. The kidneys of the lamb sacrificed at 117 days were smaller than normal and grossly dysplastic. The kidneys of the lambs that underwent ureteric ligation at 60 and 72 days were structurally different, with the ureters ligated at 60 days being small and dysplastic, while those with the ureters ligated at 72 days were larger and appeared almost polycystic.