Clinical scenario: Nephrotic syndrome | sudden hematuria & flank pain
A 13-year-old boy with steroid-resistant nephrotic syndrome presents with sudden-onset severe left flank pain and gross hematuria. He has facial puffiness and bilateral pedal edema. His blood pressure is 130/85 mmHg.
Investigations:
- Serum albumin: 1.7 g/dL
- Urine protein: 4+
- Serum creatinine: 1.4 mg/dL (baseline 0.7 mg/dL)
- Hemoglobin: 13.2 g/dL
- Platelets: 420 × 10⁹/L
- Urinalysis: Numerous RBCs
Renal ultrasound shows an enlarged left kidney without hydronephrosis.
What is the most appropriate next investigation to confirm the diagnosis?
A. Contrast-enhanced CT renal angiography
B. DMSA renal scan
C. Doppler ultrasonography of the renal veins
D. Micturating cystourethrogram
E. Tc-99m MAG3 renogram
Correct answer & Explanation:
Correct Answer: C. Doppler ultrasonography of the renal veins
Explanation
Children with nephrotic syndrome, especially steroid-resistant disease with severe hypoalbuminemia, are at high risk of venous thromboembolism due to:
- Urinary loss of antithrombin III
- Increased fibrinogen and clotting factors
- Hemoconcentration
- Platelet hyperaggregability
The combination of:
- Sudden flank pain
- Gross hematuria
- Rising serum creatinine
- Enlarged kidney
should immediately suggest renal vein thrombosis (RVT).
The initial investigation of choice is renal Doppler ultrasonography, which can demonstrate absent or reduced venous flow and is non-invasive, rapid, and readily available in children.
Why the other options are incorrect
A. Contrast-enhanced CT renal angiography
Useful if Doppler findings are inconclusive, but it is not the first investigation because of radiation and contrast exposure.
B. DMSA renal scan
Assesses cortical scarring and differential renal cortical function, not venous thrombosis.
D. Micturating cystourethrogram
Used to diagnose vesicoureteric reflux and posterior urethral valves.
E. Tc-99m MAG3 renogram
Evaluates renal drainage and perfusion but is not the preferred test for diagnosing RVT.
Key Learning Points
- Severe nephrotic syndrome is a hypercoagulable state.
- Sudden flank pain with hematuria in nephrotic syndrome should prompt suspicion for renal vein thrombosis.
- Doppler ultrasonography is the first-line diagnostic investigation.
- Early anticoagulation after confirmation can preserve renal function and prevent thromboembolic complications.
