Uriniferous perirenal pseudocyst. An unusual cause of a calcified abdominal mass in the neonate.

Radiologically visible calcification in the wall of a uriniferous perirenal pseudocyst is rare. This unusual finding was seen in a newborn infant who was found to have a left flank mass on the first day of life. When perirenal pseudocysts occur in infants, they are usually caused by congenital obstructive lesions of the urinary tract.