Polycystic kidney disease

Polycystic kidney disease occurs as two distinc genetic disorders, autosomal dominant and autosomal recessive forms. The incidence of polycystic kidney disease is 1 in 1000 live births, making it the most common of the inherited disorders. Autosomal dominant polycystic kidney disease, in which bilateral renal cysts form and progress, rarely presents in neonate. When it does, the presentation is similar to that of the recessive form, with a broad range of severity from asymptomatic through severe renal dysfunction, along with variable degrees of hypertension. As a result, the parents of any baby who has polycystic kidney disease should themselves undergo ultrasonographic examinations to rule out the small possibility of the disease being the autosomal dominant form. any patients have no renal symptoms through childhood, but in the long term, more than 50% deteriorate progressively to end-stage disease, often over decades.

The clinical presentation includes polycystic kidneys, congenital hepatic fibrosis, and some degree of biliary dysgenesis, although hepatic symptoms are uncommon in neonatus. The renal manifestations vary in severity but generally include large kidneys that appear echogenic on prenatal ultrasonography, with initially normal amniotic fluid volume. Characteristically, the kidney filled with multiple small cysts that are not easily visible on early ultrasonography and only appear as gestation proceeds, although the kidneys are large and echogenic. The gross appearance of the kidney mirrors of the ultrasonographic findings, with numerous small cysts throughout the parenchyma.

In more severe cases of autosomal recessive polycystic kidney disease, the amniotic volume declines as gestation progresses, and in many cases, oligohydramnios is present by late in the second trimester. These more severely affected fetuses may develop the Potter phenotype, with pulmonary hypoplasia and a small chest, beaked and flattened  nose, and deformations of the extrimities and spine. This phenotype is most likely to develop when severe oligohydramnios is present by mid-gestation. In these instances, the degree of lung hypoplasia may be critical, making extrauterine survival imposible.

Among a recent large cohort of patients for whom prenatal diagnosis is available, the early mortality was slightly more then 25%, primarly as a result  of respiratory failure and sepsis.A total of 41% of patients required mechanical ventilation after birth, and almost 12% of the survivors developed chronic lung disease. Longer term, 42% developed chronic renal insufficiency, and more than 25% of patients manifested slowed or delayed growth in infancy and early childhood, related to poor renal and pulmonary function. Importantly, the median age of the patients was 5,4 years, demonstrating that survival at least through childhood is possible with this disease.