Question

A 1-week-old septic neonate develops hematuria, thrombocytopenia, and a palpable flank mass. What is the most likely diagnosis?

• A. Microangiopathic hemolytic anemia
• B. Bilateral renal vein thrombosis
• C. Contrast study is the best diagnostic tool
• D. Posterior urethral valves

Hint:

Remember the classical triad of Neonatal Renal Vein Thrombosis:
1. Palpable flank mass
2. Gross or microscopic hematuria
3. Thrombocytopenia
Doppler USG is the diagnostic modality of choice; contrast studies should be avoided due to high risk of acute tubular necrosis.

Answer 1

The Correct Option is B

Concept:
Neonatal renal vein thrombosis (RVT) is the most common non-catheter-related vascular thrombosis seen in the neonatal intensive care unit.
It classically presents in critically ill or dehydrated neonates, particularly those with perinatal asphyxia, sepsis, polycythemia, or maternal diabetes, with a distinct clinical triad of gross hematuria, a palpable unilateral or bilateral flank mass, and consumptive thrombocytopenia.
Explanation:
• Renal vein thrombosis in neonates most commonly originates in the small intrarenal arcuate and interlobular veins before propagating into the main renal vein and inferior vena cava.

• The classical diagnostic triad includes a palpable abdominal/flank mass (due to acute renal engorgement, edema, and venous congestion), gross or microscopic hematuria, and thrombocytopenia (caused by local consumption and destruction of platelets within the forming thrombus).

• Neonatal sepsis leads to dehydration, hemoconcentration, endothelial injury, and systemic activation of the coagulation cascade, creating ideal Virchow's triad conditions for thrombogenesis.

• Color Doppler Ultrasonography is the first-line imaging modality of choice for confirming renal vein thrombosis as it non-invasively evaluates renal enlargement, increased echogenicity, loss of corticomedullary differentiation, and absence of venous blood flow without nephrotoxic contrast agents.

• Microangiopathic hemolytic anemia (MAHA) can cause thrombocytopenia and hematuria (such as in Hemolytic Uremic Syndrome), but it does not classically produce a large, rapidly enlarging palpable flank mass in a 1-week-old neonate.

• Posterior urethral valves typically present with bilateral hydronephrosis, a palpable distended urinary bladder, and poor urinary stream, rather than acute consumptive thrombocytopenia and acute unilateral/bilateral flank masses.
Final Answer:
The clinical triad of gross hematuria, consumptive thrombocytopenia, and a palpable flank mass in a septic neonate is diagnostic of bilateral renal vein thrombosis.