Renal Venous Thrombosis

Basics

DESCRIPTION

  • Thrombus formation in renal veins (stellate veins, interlobular veins, ascending vasa recta, arcuate veins, hilar veins, or renal vein)
  • Most common non–catheter-related thromboembolism in the neonatal period
  • May also be associated with nephrotic syndrome, hypercoagulable states, and oral contraceptive use
  • May present with a clinical triad of flank mass, gross hematuria, and thrombocytopenia

EPIDEMIOLOGY

  • Most commonly seen in the newborn period
  • Slight male predominance
  • In neonates, most cases are unilateral (70%), with the left kidney more frequently affected. The left side predominance may be due to the anatomical course of the left renal vein underneath the aorta.

INCIDENCE

  • Not well-defined due to lack of data
  • Ranges from 0.5 to 2.3 per 100,000 live births

PREVALENCE

Accounts for 16–20% of thromboembolic events in newborns

RISK-FACTORS

  • Maternal diabetes mellitus
  • Birth asphyxia
  • Dehydration/blood loss
  • Polycythemia
  • Cyanotic heart disease
  • Hypercoagulable states
  • Nephrotic syndrome
  • Venous catheter
  • Sepsis
  • Oral contraceptive use
  • Renal transplant recipient

GENETICS

  • ~50% of affected neonates have at least one hereditary prothrombotic risk factor.
  • Factor V Leiden, protein C/S, and MTHFR mutations and lupus anticoagulant

GENERAL-PREVENTION

  • Maintaining a high index of suspicion in patients at risk (i.e., infant of diabetic mother, child with nephrotic syndrome)
  • Counseling regarding the importance of adequate fluid intake and avoidance of dehydration, especially in newborn infants
  • Prophylactic anticoagulation may be indicated in certain populations, although conclusive data is lacking.

PATHOPHYSIOLOGY

  • Thrombus formation is initiated by endothelial cell injury from hypoxia or other insults.
  • In neonates, non–catheter-related renal vein thrombosis (RVT) is believed to originate in the arcuate or interlobular veins, as evidenced by early ultrasound findings.
  • Thrombosis may extend to the inferior vena cava (IVC) in 50–60% of cases.
  • Neonates also have decreased levels of protein C, protein S, antithrombin, and plasminogen, which may make them more susceptible to thrombosis.
  • Lower renal blood flow may also predispose neonates to venous thrombosis.
  • In older children, thrombosis may be associated with nephrotic syndrome, hypercoagulable states, or cyanotic heart disease.
  • Renal venous thrombosis can result in renal enlargement, decreased renal venous flow, and increased arterial resistive indices.
  • Adrenal hemorrhage and left varicocele may also result from renal venous thrombosis.

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