FCPS Paediatrics TOACS · Interactive Station

🩺 Neonatal Renal Vein Thrombosis (RVT) — Clinical recognition, lab interpretation, management & counseling (IDM + renal mass) 📚 Paeds Online – paeds.online

⚕️ OBSERVED STATION · CPSP FORMAT · 8 MINUTES · NEONATAL THROMBOSIS

📖 Problem-Oriented Clinical Scenario + Lab Data (Neonatal RVT)

👶🏻 Clinical Scenario (read aloud – 2 minutes):

A 5-day-old term infant presents to the emergency department with vomiting, lethargy, and poor feeding. Mother is a known type 1 diabetic since age 10 years (poor glycemic control during pregnancy). The baby has not passed urine for the last 18 hours. On examination, the infant is lethargic, pale, with mild jaundice. A firm, non-tender left flank mass is palpable. Vital signs: HR 170/min, RR 58/min, BP 68/40 mmHg, temperature 37.8°C. No other abnormalities.

Laboratory investigations are as follows:

Na⁺ 144 mmol/L

K⁺ 5.3 mmol/L

Urea 7.8 mmol/L

Creatinine 125 μmol/L (↑↑)

Hb 16.3 g/dL

Platelets 60 × 10⁹/L (↓)

LFT & clotting Normal

Urinalysis: Protein +++, RBC +++

📊 Imaging & Diagnostic Consideration:
• Renal Doppler Ultrasound (to be ordered): expected findings — enlarged left kidney, loss of corticomedullary differentiation, echogenic intraluminal material in left renal vein, absent venous flow on Doppler; possible extension into IVC. Right kidney normal.
• Key differentials: adrenal hemorrhage (suprarenal mass, hyponatremia), congenital mesoblastic nephroma, hydronephrosis, unilateral renal agenesis with compensatory hypertrophy.

💡 Examiner instruction (interactive): The candidate must interpret the clinical scenario and lab data, recognize renal vein thrombosis as the likely diagnosis, discuss risk factors (IDM, polycythemia, hyperviscosity), plan immediate management (fluid resuscitation, partial exchange transfusion if polycythemic, supportive care), anticoagulation indications, and explain long-term renal sequelae.

🔍 Examiner Q&A – Renal Vein Thrombosis (Neonatal RVT)

❓ Q1 (Examiner): “Based on the history and labs, what is your most likely diagnosis? Justify.”

✅ Candidate’s structured answer:
• Diagnosis: Neonatal Renal Vein Thrombosis (RVT), left-sided.
• Justification: Infant of diabetic mother (hyperviscosity/polycythemia risk), acute renal failure (↑ creatinine, anuria), palpable renal mass, thrombocytopenia, hematuria + proteinuria. Classical triad: flank mass, thrombocytopenia, hematuria. Doppler ultrasound would confirm absent venous flow.

❓ Q2 (Examiner): “What are the risk factors for neonatal renal vein thrombosis?”

✅ Candidate's answer:
• Maternal: Diabetes mellitus (most important), polycythemia, dehydration, sepsis, asphyxia.
• Neonatal: Polycythemia, hyperviscosity, umbilical venous catheter (thrombus extension), inherited thrombophilias (Factor V Leiden, prothrombin mutation, protein C/S deficiency), dehydration, congenital nephrotic syndrome.
• This infant: IDM → polycythemia / hyperviscosity → renal venous stasis → thrombosis.

❓ Q3 (Examiner): “Explain the pathophysiology of RVT in an infant of diabetic mother.”

✅ Candidate's answer:
• Maternal hyperglycemia → fetal hyperglycemia → fetal hyperinsulinism → increased erythropoietin → polycythemia and hyperviscosity.
• Hyperviscosity → sluggish renal venous flow → increased risk of thrombosis, especially in the left renal vein (anatomically longer).
• Dehydration and perinatal stress further increase risk.

❓ Q4 (Examiner): “What immediate investigations would you order?”

✅ Candidate's answer:
• Renal Doppler ultrasound – diagnostic (enlarged kidney, echogenic streaks, absent venous flow, possible extension into IVC).
• Coagulation workup: PT, APTT, fibrinogen, d-dimer, antithrombin III, protein C/S, Factor V Leiden, prothrombin gene mutation, lipoprotein (a), homocysteine.
• Complete blood count (thrombocytopenia, polycythemia), serum creatinine, BUN, electrolytes.
• Echocardiogram – rule out extension into IVC/right atrium.

❓ Q5 (Examiner): “How do you interpret the platelet count of 60 × 10⁹/L in this setting?”

✅ Candidate's answer:
• Severe thrombocytopenia is characteristic of RVT due to platelet consumption within the thrombus and consumptive coagulopathy (localized DIC).
• It is not immune-mediated; platelet transfusion not indicated unless active bleeding.
• Typically resolves as thrombosis resolves.

❓ Q6 (Examiner): “What is the immediate medical management of neonatal RVT?”

✅ Candidate's answer:
• Supportive care: Correct dehydration (IV fluids cautiously, avoid overload), monitor renal function, strict input/output, blood pressure control.
• Treat hyperviscosity: Partial exchange transfusion if Hct >65-70% with symptoms.
• Anticoagulation (controversial but often used for bilateral or IVC extension): Unfractionated heparin or LMWH (enoxaparin) in selected cases, after consulting hematology.
• Avoid nephrotoxic drugs. Monitor for hypertension (renin-mediated).

❓ Q7 (Examiner): “Is thrombolytic therapy or thrombectomy indicated in neonates?”

✅ Candidate's answer:
• Generally not first-line due to high bleeding risk. Reserved for massive bilateral RVT with impending renal failure, extension into IVC causing critical compromise, or pulmonary embolism.
• Options: tissue plasminogen activator (tPA) – high risk; surgical thrombectomy rarely performed.
• Most centers treat with supportive care + anticoagulation only.

❓ Q8 (Examiner): “What are the complications of neonatal RVT?”

✅ Candidate's answer:
• Acute: acute kidney injury (AKI), persistent anuria, hypertension, extension to IVC, adrenal hemorrhage (if ipsilateral), sepsis, consumptive coagulopathy.
• Long-term: chronic kidney disease (CKD), renal atrophy, persistent hypertension, proteinuria, renal vein recanalization, renal scarring.
• Up to 50% develop some degree of renal impairment; some require dialysis or transplantation.

❓ Q9 (Examiner): “How does renal vein thrombosis differ from adrenal hemorrhage?”

✅ Candidate's answer:
• Adrenal hemorrhage also seen in IDM, presents with flank mass, anemia, jaundice, but often hypotension, hyponatremia (adrenal insufficiency), and ultrasound shows suprarenal heterogeneous mass.
• RVT: thrombocytopenia, hematuria, renal vein thrombus on Doppler, anuria. Coexisting possible.

❓ Q10 (Examiner): “What is the role of renal biopsy in suspected RVT?”

✅ Candidate's answer:
• No role in acute setting. Diagnosis is clinical + Doppler ultrasound.
• Biopsy contraindicated due to bleeding risk and thrombocytopenia.

❓ Q11 (Examiner): “What is the long-term follow-up needed for this infant?”

✅ Candidate's answer:
• Serial blood pressure monitoring (risk of renin-mediated hypertension).
• Renal function surveillance (serum creatinine, eGFR, urine protein/creatinine ratio).
• Renal ultrasound at 3, 6, 12 months to assess for atrophy or compensatory hypertrophy of contralateral kidney.
• Nephrology referral; manage hypertension with ACE inhibitors if needed.
• Long-term risk of CKD.

❓ Q12 (Examiner): “What is the prognosis of unilateral vs bilateral RVT?”

✅ Candidate's answer:
• Unilateral (this case): 60-80% recover near-normal function, but 20-40% develop hypertension or mild CKD. Affected kidney may atrophy.
• Bilateral: poor prognosis; up to 50% develop end-stage renal disease (ESRD) requiring dialysis/transplant.
• Early supportive care improves outcomes.

❓ Q13 (Examiner): “Would you use anticoagulation in this infant? Justify.”

✅ Candidate's answer:
• For isolated unilateral RVT without IVC extension, many experts favor supportive care alone (fluids, correct polycythemia) as spontaneous recanalization occurs.
• If extensive thrombus (bilateral, IVC extension, or renal failure progression), start LMWH (enoxaparin) after hematology consult. Monitor anti-Xa levels.
• Current evidence (THROMBOPED registry) suggests anticoagulation reduces extension but doesn't improve long-term renal outcome significantly.

❓ Q14 (Examiner): “How do you counsel parents about recurrence risk and future pregnancies?”

✅ Candidate's answer:
• Recurrence risk in infancy is low if thrombophilia workup negative. However, if inherited thrombophilia is detected, future siblings may be at risk.
• For future pregnancies, mother should have strict glycemic control preconceptionally, and neonatal team should monitor for polycythemia and dehydration.
• No specific prenatal treatment for RVT; perform newborn screening for hyperviscosity if IDM.
• Reassure that most infants with unilateral RVT do well but need long-term kidney follow-up.

🗣️ Examiner’s probing points:
• “What if the baby develops anuria and creatinine rises to 200 μmol/L despite fluids?” → Consider dialysis (peritoneal or hemodialysis) if refractory hyperkalemia/acidosis.
• “When would you start ACE inhibitors?” → If hypertension persists beyond 1–2 weeks or develops later.
• “What is the earliest sign on ultrasound?” → Enlarged kidney, echogenic lines in veins, loss of corticomedullary differentiation; Doppler confirms absent flow.

📘 Topic Summary: Neonatal Renal Vein Thrombosis (RVT)

🔍 Definition
Thrombotic occlusion of renal vein(s) in newborns; most common non-catheter-related neonatal renal thrombosis. Associated with IDM, polycythemia, dehydration, prothrombotic states.

📊 Classic Triad
Flank mass (enlarged kidney), thrombocytopenia, hematuria/proteinuria. Plus acute kidney injury (anuria/oliguria).

🩺 Diagnostics
Renal Doppler ultrasound (gold standard): absent venous flow, enlarged echogenic kidney, possible IVC thrombus. Coagulation workup for thrombophilia.

⚕️ Management
Supportive: correct dehydration, treat polycythemia (partial exchange if Hct>65-70%). Anticoagulation (LMWH) for bilateral/IVC extension. Avoid nephrotoxins. BP control.

📈 Prognosis
Unilateral: good renal survival (~70-80%), but hypertension and mild CKD common. Bilateral: high risk (50% ESRD). Long-term nephrology follow-up essential.

📌 Prevention (IDM)
Strict maternal glycemic control, prevent neonatal polycythemia, maintain hydration, avoid umbilical catheter if possible, early feeding.

⭐ High-yield pearls – Neonatal RVT (TOACS):
• Always suspect in infant of diabetic mother + acute renal failure + flank mass.
• Differentiate from adrenal hemorrhage (adrenal insufficiency, hyponatremia, normal Doppler, suprarenal mass).
• Do NOT give platelet transfusion for isolated thrombocytopenia unless bleeding.
• Partial exchange transfusion indicated for symptomatic polycythemia (Hct >65-70% with hyperviscosity symptoms).
• Anticoagulation: weigh risks – consult hematology.
• Long-term: monitor for hypertension even after kidney atrophy.

🗣️ Candidate Role-Play & Examiner Feedback (TOACS Observed Station)

💬 To the candidate (role-play tasks):
1. Introduce yourself to the parents (simulated), obtain consent, explain the urgency.
2. Perform focused examination: Palpate abdomen (flank mass), assess hydration, vital signs, check for hypertension.
3. Verbally interpret labs: “High creatinine, low platelets, hematuria, proteinuria – suggestive of renal vein thrombosis.”
4. Order renal Doppler and discuss differential (adrenal hemorrhage, hydronephrosis, tumor).
5. Propose initial management: IV fluids (careful), check hematocrit, consult nephrology/hematology, consider partial exchange if polycythemic, start anticoagulation if extensive thrombus.
6. Counsel parents: Explain thrombosis, risk factors (mother’s diabetes), treatment plan, possible long-term kidney follow-up, good prognosis for unilateral involvement.

📝 Examiner Marking Grid (RVT station – CPSP format):

✅ Correctly interprets case: IDM + anuria + flank mass + thrombocytopenia → RVT
✅ Orders appropriate diagnostic test (Renal Doppler US) and coagulation panel
✅ Identifies hyperviscosity/polycythemia as major risk factor
✅ Proposes supportive management (fluids, exchange transfusion if indicated)
✅ Discusses anticoagulation judiciously (with hematology consultation)
✅ Recognizes complications: AKI, hypertension, CKD
✅ Provides clear, empathetic counseling to parents
✅ Arranges long-term follow-up (BP, renal function, nephrology)
✅ Avoids common errors: platelet transfusion, unnecessary thrombolytics

📚 Key references: Nelson Textbook of Pediatrics (22nd ed) – Renal Vein Thrombosis; American Heart Association Scientific Statement on Neonatal Thrombosis; CPSP neonatology guidelines; Paeds.Online neonatal thrombosis module.

💡 Common pitfalls to avoid:
• Missing the diagnosis of RVT and attributing anuria to dehydration only.
• Ordering renal biopsy (contraindicated).
• Not checking for extension into IVC (risk of pulmonary embolism).
• Failing to consider underlying thrombophilia.
• Not discussing long-term hypertension and CKD surveillance with parents.