✅ Model Answer:
• Diagnosis: Renal vein thrombosis (RVT) – neonatal.
• Evidence: Perinatal asphyxia, gross hematuria, flank mass, thrombocytopenia, absent venous flow on Doppler ultrasound.
• Next step: Renal Doppler ultrasound (confirms diagnosis). Supportive care – IV hydration, treat sepsis if present. Anticoagulation (heparin) if bilateral RVT or IVC extension. Monitor renal function, BP, and platelet count. Nephrology consultation.

✅ Model Answer:
• Risk factors: Perinatal asphyxia, dehydration, sepsis, polycythemia, maternal diabetes, congenital nephrotic syndrome, IV line (umbilical vein catheter).
• Pathophysiology: Thrombosis of the renal vein (usually left side) due to hypercoagulability, stasis, or vascular injury → venous congestion → renal enlargement, hematuria, proteinuria, and impaired renal function.
• Extension: May extend into the inferior vena cava (IVC) or adrenal vein.
• Platelet consumption: Thrombocytopenia occurs due to consumption.
• Outcome: Most neonates recover with supportive care; complications include renal atrophy, hypertension, and chronic kidney disease.

✅ Model Answer:
• Classic triad: Gross hematuria, flank mass, thrombocytopenia.
• Other features:
- Hypertension: Due to renal ischemia or renin release.
- Oliguria or anuria.
- Sepsis: Often present (especially if umbilical catheter).
- Abdominal distension.
- Adrenal hemorrhage: If extension to adrenal vein.
- IVC extension: May cause bilateral RVT or Budd-Chiari syndrome (rare).
• Onset: Usually within the first few days of life.

✅ Model Answer:
• Imaging:
- Renal Doppler ultrasound: First-line – shows enlarged kidney, absent or reversed venous flow, intraluminal thrombus, or echogenic streaks in the renal vein.
- Abdominal CT angiography: If ultrasound is inconclusive (shows filling defect in renal vein/IVC).
- Echocardiogram: To rule out IVC extension or cardiac involvement.
• Laboratory tests:
- CBC: Thrombocytopenia (common), anemia (due to blood loss).
- Serum creatinine: May be elevated (acute kidney injury).
- Urinalysis: Gross hematuria, proteinuria.
- Coagulation studies: PT, PTT, fibrinogen (may be normal).
- Thrombophilia workup: If recurrent or familial (Factor V Leiden, protein C/S deficiency, antithrombin III).
• Other: Blood culture (rule out sepsis).

✅ Model Answer:
• Supportive care (mainstay):
- IV hydration: Maintain adequate urine output.
- Treat sepsis: If present (empiric antibiotics).
- Monitor BP, urine output, creatinine.
- Platelet transfusion: If severe thrombocytopenia (<20,000) or bleeding.
• Anticoagulation:
- Unfractionated heparin (UFH): For bilateral RVT, IVC extension, or progressive thrombus. Dose: loading 75-100 U/kg, then 28 U/kg/hour, target aPTT 60-85 sec.
- Low molecular weight heparin (LMWH): Enoxaparin 1-2 mg/kg q12h (monitor anti-Xa).
- Duration: Usually 3-6 weeks (or until thrombus resolution).
• Thrombolysis: rTPA (rare, if life-threatening IVC obstruction).
• Surgical thrombectomy: Rarely indicated.

✅ Model Answer:
• Renal:
- Renal atrophy: Shrunken kidney on follow-up ultrasound (30-50% of cases).
- Chronic kidney disease (CKD): In severe cases.
- Renal vein calcification: May be seen on ultrasound.
• Vascular:
- Hypertension: Due to renal ischemia (may be transient or permanent).
- IVC thrombosis: May lead to Budd-Chiari syndrome or pulmonary embolism (rare).
• Other:
- Adrenal hemorrhage: If extension to adrenal vein.
- Proteinuria: May persist.
- Growth failure: If CKD develops.
- Recurrence: If underlying thrombophilia.

✅ Model Answer:
• Prognosis:
- Good with supportive care and anticoagulation (if indicated).
- Complete recovery: In most neonates (70-80%).
- Renal atrophy: 30-50% develop renal atrophy on follow-up.
- Hypertension: 10-20% develop hypertension (usually transient).
- CKD: Rare (if bilateral RVT or severe ischemia).
- Mortality: Low (<5%), usually due to associated sepsis or prematurity.
• Long-term follow-up:
- Monitor BP: Annually.
- Monitor proteinuria: Spot urine protein/creatinine ratio annually.
- Monitor creatinine/eGFR: Annually.
- Renal ultrasound: At 3-6 months and then annually (for renal atrophy).
- Thrombophilia workup: If recurrent thrombosis or family history.
- Educate parents: About signs of hypertension and renal dysfunction.

✅ Model Answer:
• Renal vein thrombosis (neonatal):
- Age: Neonates (first days of life).
- Risk factors: Perinatal asphyxia, sepsis, dehydration, polycythemia, maternal diabetes.
- Presentation: Gross hematuria, flank mass, thrombocytopenia.
- Ultrasound: Enlarged kidney, absent venous flow, echogenic streaks (thrombus).
- Treatment: Supportive, anticoagulation if bilateral/IVC.
- Prognosis: Good; may develop renal atrophy.
• Wilms tumor (neonatal – rare):
- Age: Usually >1 year (rare in neonates).
- Risk factors: WT1 mutations, WAGR syndrome, Beckwith-Wiedemann.
- Presentation: Asymptomatic abdominal mass (most common), hematuria (less common), hypertension.
- Ultrasound: Solid/hypoechoic mass with internal vascularity.
- Treatment: Surgical nephrectomy + chemotherapy.
- Prognosis: Good with treatment (survival >90%).
• Key difference: RVT presents early (<1 week) with risk factors and thrombocytopenia; Wilms tumor is rare in neonates and presents as a solid mass.