[Pathological study of the kidney and the lung in patients with Potter sequence]

The condition in infants showing the characteristic facial abnormalities, limb deformities, and pulmonary hypoplasia induced by oligohydramnios is termed Potter sequence (PS). In addition to bilateral renal agenesis, Potter sequence could be caused by other urological abnormalities such as cystic dysplasia and obstructive uropathy. Although lethal in most of the patients with PS, some exceptional infants were reported to survive in spite of the antenatal demonstration of oligohydramnios from renal abnormalities. These surviving patients put new questions to us regarding the management of both respiratory and renal failure starting from the newborn periods. The diversity of clinical courses in patients with antenatally detected PS may imply that this entity has a spectrum of severity. Our study of infants autopsied on the diagnosis of PS was undertaken to determine various histological grade of the kidneys and the lungs.

Thirty-two autopsy cases of PS (19 males and 13 females) diagnosed by the presence of the characteristic stigmata, oligohydramnios, and renal or urological abnormalities were studied retrospectively. Patients were divided according to the urological abnormalities into 3 groups; renal hypodysplasia, urinary obstruction, and polycystic kidney disease (PCKD). Renal histology was evaluated by two parameters; renal glomerular count (RGC), and dysplastic grade. Developmental aspects of the lung were judged by lung/body-weight ratio (L/ B ratio) and radial alveolar count (RAC) proposed by Emery.

The underlying urological disorders included renal hypodysplasia in 22 patients, obstruction in 7, and polycystic kidney disease in 3. Dysplastic grade of 29 patients with hypodysplasia and obstruction consisted of grade 4 in 12 patient, grade 3 in 9, and grade 2 in 8. In 10 kidneys from 8 patients with grade 2-dysplasia, RGC was significantly fewer than that of normal fetuses for the gestational age. The term patient with PS showed the glomerular count equivalent to normal fetus of around 25 weeks of gestation. L/B ratio indicated definite pulmonary hypoplasia in 25 of 29 patients. The ratio was much smaller than normal in another 4 patients. RAC was calculated in 24 patients; of these only 2 had normal count for gestational age. In another 22, the number of air space stopped to increase at about 20 to 25 weeks of gestation. There was a tendency for L/B ratio to decrease according to dysplastic grade (1.3% for grade 2 vs. 0.9% for grade 3 and 4).

The primary urological abnormalities leading to PS included bilateral renal hypodysplasia, obstructive uropathy, and PCKD. Histological study of the kidneys indicates that PS is the spectrum disease with various degree of nephron formation. The development of the lung depends, in part, on the grade of renal dysplasia.