Renal Venous Thrombosis in Infancy

Thrombosis of the venous system of one or both kidneys occurs as an acute and life-threatening illness. In the pediatric age group, the primary involvement is witin the intrarenal venous circulation, rather than the main renal vein. For this reason the appropriate term is renal venous thrombosis (RVT). Ninety percent of the patients are less than 1 year of age and 75% are less than 1 month of age. Males are affected at a rate nearly twice that of females. An appreciation of the circumstances in which this disease occurs and the associated clinical symptoms and findings can aid in early diagnosis and increase the potential for successful management. PATHOGENESIS The arcuate veins drain the interlobular veins from the cortex and the ascending vasa recta veins of the medulla (Fig 1).1 It is in these small veins that the initial thromboses originate and subsequently spread distally to involve the stellate veins of the cortex and proximally to the interlobar and main renal veins. The slow double capillary circulation within the kidney is considered to be especially vulnerable to thrombosis in situations of (1) hemoconcentration with or without dehydration, (2) hypercoaguability, (3) hyperosmolality, and (4) hypoperfusion (Fig 2).2 The observation that three of four infants with renal venous thrombosis are less than 1 month of age emphasizes the vulnerability of the neonate to this illness.