Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (554 page)

   Autosomal Recessive Polycystic Kidney Disease (ARPKD)

   Less common than ADPKD with an incidence of 1: 20,000 live births. It is caused by mutations of the
PKHD1
(polycystic kidney and hepatic disease 1) gene and typically identified during the first few weeks after birth.

   Children born with ARPKD often develop kidney failure before reaching adulthood. In addition, they demonstrate liver scarring and can have nephrolithiasis, hypertension, and urinary tract infections.

   Kidney and liver imaging studies of the fetus or newborn establish the diagnosis.

Suggested Reading

Harris PC, Torres VE. Polycystic kidney disease.
Annu Rev Med.
2009;60:321–337.

RENAL PARENCHYMAL MALFORMATION

   Definition

This condition causes failure of normal nephron development and results from genetic and environmental factors. Genetic factors include mutations in the genes expressed during kidney development (e.g.,
EYA1, SIX1, TCF2, SALL1, FRAS1, PAX2
); environmental factors include exposure to teratogens and nutritional deficiencies.

   Laboratory Findings

   Renal parenchymal malformation disorders can be distinguished based on histologic examinations and they include:

   Renal hypoplasia: the number of structurally normal nephrons is decreased. Renal size is typically reduced by 2 standard deviations from the mean size for the age.

   Renal dysplasia: characterized by the presence of malformed kidney tissue elements. Dysplastic kidneys are variable in size but usually smaller than normal.

   Renal agenesis: defined as congenital absence of renal parenchymal tissue. The majority of patients with unilateral renal agenesis are asymptomatic.

   Multicystic dysplasia: characterized by a nonfunctioning dysplastic kidney with multiple cysts.

   Renal tubular dysgenesis: very rare disorder characterized by the absence or poor development of proximal tubules.