Nephrotic Syndrome — Causes, Symptoms, and Why Kidney Biopsy Is the Only Path to the Right Diagnosis
Nephrotic syndrome is one of the most alarming kidney presentations legs and feet swollen to the point of pitting deeply when pressed, face puffed overnight, frothy or bubbly urine that persists despite drinking more water, and profound fatigue. It develops quickly sometimes within days and when it arrives, it demands urgent medical attention. But nephrotic syndrome is not itself a diagnosis. It is a clinical syndrome a constellation of findings that results from several completely different kidney diseases, each with its own cause, its own natural history, and its own treatment. Treating nephrotic syndrome without knowing which underlying disease is responsible means giving the wrong treatment to a significant proportion of patients.
This is why kidney biopsy is essential in adult nephrotic syndrome not as a precautionary investigation, but as the diagnostic procedure that makes the correct treatment possible. At KIMS Secunderabad, nephrotic syndrome is evaluated by Dr. Aswini Dutt T, whose specific subspecialty focus in glomerular disease means that the most complex presentations steroid-resistant FSGS, PLA2R-positive membranous nephropathy, difficult lupus nephritis are managed with the depth of expertise these conditions require.
What is nephrotic syndrome — the defining findings
Nephrotic syndrome is defined by four cardinal findings that occur together as a consequence of massive protein leakage from the damaged kidney filter:
Heavy proteinuria (above 3.5 grams per day)
The hallmark finding. The glomerular filtration barrier normally impermeable to proteins as large as albumin is breached, allowing proteins to pour into the urine. The frothy, foamy quality of the urine that most patients first notice is caused by proteins in the urine lowering the surface tension, in the same way that detergent produces foam.
Hypoalbuminaemia (serum albumin below 30 g/L)
As albumin leaks into the urine faster than the liver can replace it, plasma albumin levels fall. Albumin is the principal protein maintaining oncotic pressure the force that keeps fluid inside blood vessels. When albumin is low, fluid shifts out of blood vessels into surrounding tissues.
Oedema (fluid accumulation in tissues)
The consequence of low oncotic pressure — fluid leaves blood vessels and accumulates in dependent areas (ankles, legs, feet on standing) and in the face and around the eyes (particularly prominent in the morning after lying flat overnight). Severe nephrotic syndrome causes fluid in the abdominal cavity (ascites), around the lungs (pleural effusions), and in the scrotum.
Hyperlipidaemia (high cholesterol and triglycerides)
A reactive response the liver, sensing low oncotic pressure, upregulates lipoprotein synthesis. Total cholesterol and LDL are markedly elevated in nephrotic syndrome, contributing to the substantially increased cardiovascular risk associated with heavy proteinuria.
Additional complications of nephrotic syndrome:
Hypercoagulability: Loss of anticoagulant proteins in the urine creates a thrombotic state — nephrotic syndrome is a significant risk factor for deep vein thrombosis and pulmonary embolism.
Infection Risk: Loss of immunoglobulins in the urine impairs immune defence, increasing susceptibility to infections.
Nutrition: Protein malnutrition can occur in severe, prolonged cases.
Causes of nephrotic syndrome — why biopsy is essential
In adults, nephrotic syndrome can be caused by a range of different primary glomerular diseases and secondary causes (systemic conditions affecting the kidney). The clinical presentation heavy proteinuria, oedema, hypoalbuminaemia is essentially identical regardless of which disease is responsible. The treatment is fundamentally different. Without a kidney biopsy, the correct disease cannot be identified and the correct treatment cannot be prescribed.
Minimal Change Disease (MCD)
The most common cause of nephrotic syndrome in children and a significant cause in adults (especially over 60). The glomeruli appear normal on light microscopy; the only diagnostic finding is fusion of podocyte foot processes on electron microscopy. MCD responds to steroids in 80-90% of adult cases. Without electron microscopy, MCD cannot be diagnosed, which may lead to treatment delays or unnecessary aggressive immunosuppression.
Focal Segmental Glomerulosclerosis (FSGS)
The most common cause of nephrotic syndrome in adults in India, characterised by segmental scarring. FSGS can be: • Primary: Immune-mediated; treated with steroids, tacrolimus, or rituximab. • Secondary: Linked to obesity or reduced nephron mass; does not respond to immunosuppression. • Genetic: Steroid-resistant; requires specialized management. Clinical context and biopsy histology are the only ways to distinguish these three completely different subtypes.
Membranous Nephropathy
The leading cause in adults above 40. Characterised by subepithelial immune deposits and a 'spike and dome' appearance. PLA2R antibody testing now identifies primary cases in 70-80% of patients. Treatment: Rituximab is now the preferred first-line for primary cases with heavy proteinuria. Secondary cases (associated with malignancy, hepatitis B, or autoimmune disease) require treating the underlying cause.
Diabetic Nephropathy
The most common cause of nephrotic-range proteinuria globally. While a biopsy may not be needed if the clinical history is typical (long-term diabetes, retinal changes), atypical features — like rapid onset or active urine sediment — warrant a biopsy to exclude a superimposed glomerular disease.
Lupus Nephritis
Systemic lupus erythematosus (SLE) affects the kidney in up to 60% of patients. Class V lupus nephritis presents specifically with nephrotic syndrome. Biopsy is essential for classification (ISN/RPS), which directly determines the intensity of immunosuppression required.
Amyloidosis
AL and AA amyloidosis deposit amyloid fibrils in the glomeruli. Biopsy with Congo red staining shows apple-green birefringence under polarised light, and EM confirms the fibril characteristics. Treatment targets the underlying plasma cell disorder or inflammatory cause, not standard kidney-directed immunosuppression.
Nephrotic syndrome in an adult with no prior kidney disease should prompt urgent nephrology review and kidney biopsy within 1 to 2 weeks of presentation. At KIMS, the biopsy is usually arranged within 5 to 10 working days of the clinic consultation confirming nephrotic-range proteinuria.
How nephrotic syndrome is investigated at KIMS
The evaluation of nephrotic syndrome requires a systematic approach, combining laboratory markers with advanced pathology to identify the specific underlying cause.
| Investigation | What it shows · Why it is needed |
|---|---|
| Urine dipstick + ACR/PCR | Confirms heavy proteinuria (3+ or 4+ on dipstick; PCR above 300 mg/mmol). Starting point for all nephrotic syndrome evaluation. |
| 24-hour urine protein | Quantifies proteinuria precisely (above 3.5g/day = nephrotic range). Baseline for monitoring treatment response. |
| Serum albumin | Hypoalbuminaemia confirms nephrotic syndrome. Severity of hypoalbuminaemia indicates risk of thrombosis and infection. |
| Lipid profile | Hypercholesterolaemia and hypertriglyceridaemia — both elevated in nephrotic syndrome. Cardiovascular risk assessment. |
| Renal function (eGFR, creatinine) | Baseline kidney function. Rapid decline in eGFR with nephrotic syndrome suggests rapidly progressive GN overlay or severe disease. |
| ANA, anti-dsDNA, complement (C3, C4) | Screen for systemic lupus erythematosus as cause. |
| Hepatitis B, C, HIV serology | Important secondary causes of membranous nephropathy and MPGN. |
| PLA2R antibody | Highly specific for primary membranous nephropathy — positive in 70–80% of primary cases. Guides diagnosis and treatment monitoring. |
| SPEP & Free Light Chains | Screen for paraproteinaemia as cause of amyloidosis or MIDD (Monoclonal Immunoglobulin Deposition Disease). |
| Kidney biopsy (LM + IF + EM) | The definitive diagnostic investigation. Performed after serology results are available. NABL-accredited at KIMS — all three components in-house. |
Treatment principles for nephrotic syndrome
Treatment varies completely by the underlying cause identified on biopsy. General supportive measures apply across all causes while the specific treatment is initiated:
Oedema management
Dietary sodium restriction (below 2g/day), loop diuretics (furosemide) for oedema relief. Diuretic doses must be carefully titrated — over-diuresis in hypoalbuminaemic patients causes intravascular volume depletion and AKI.
Anticoagulation
Low molecular weight heparin or warfarin for patients with serum albumin below 20 g/L or prior thrombotic events. The thrombotic risk in severe nephrotic syndrome is high enough to warrant prophylactic anticoagulation in most cases.
Statins
For hyperlipidaemia management. Atorvastatin 20 to 40mg daily is the standard choice.
ACE inhibitor or ARB
To reduce proteinuria and provide reno-protection regardless of the specific underlying disease.
Infection prevention
Pneumococcal vaccine, avoidance of live vaccines during immunosuppression.
Disease-specific treatment is initiated once biopsy confirms the diagnosis: prednisolone for MCD and primary FSGS, rituximab for primary membranous nephropathy and steroid-resistant FSGS, calcineurin inhibitors (tacrolimus) for steroid-resistant primary FSGS, and appropriate immunosuppression for lupus nephritis based on ISN/RPS class.
Frequently Asked Questions — Nephrotic Syndrome
Foamy or frothy urine — foam that persists for more than 30 seconds after urinating — is the most common symptom that prompts nephrotic syndrome patients to seek medical attention. It is caused by proteins in the urine lowering the surface tension, producing foam in the same way detergent does. Not all foamy urine indicates serious kidney disease — concentrated urine (from dehydration) can also appear foamy. But persistent, prominent foam that appears consistently and does not clear quickly warrants a urine protein test. A simple urine dipstick test showing 2+ or more protein, or a urine ACR above 30 mg/mmol, should prompt nephrology referral.
Leg swelling (oedema) in nephrotic syndrome results from hypoalbuminaemia — the loss of albumin in the urine causes plasma albumin to fall. Albumin is the protein that maintains oncotic pressure — the force keeping fluid inside blood vessels. When albumin is low, fluid shifts from blood vessels into surrounding tissues, accumulating in dependent areas (legs, ankles, feet when standing) and the face (particularly periorbital oedema — swelling around the eyes, worse in the morning). Nephrotic oedema pits deeply when pressed and does not resolve with leg elevation overnight. It is distinct from cardiac oedema (which responds somewhat to elevation) and venous oedema (which affects one leg rather than both).
No — nephrotic and nephritic syndrome are different clinical presentations of glomerular disease. Nephrotic syndrome is characterised by heavy proteinuria (above 3.5g/day), hypoalbuminaemia, oedema, and hyperlipidaemia — the result of a leaky glomerular filtration barrier that allows protein to escape. Nephritic syndrome is characterised by haematuria (blood in urine — often with red cell casts on microscopy), hypertension, and variable proteinuria — the result of glomerular inflammation and endothelial injury. Some glomerular diseases produce a mixed picture — membranoproliferative GN and lupus nephritis can present with features of both. The distinction guides initial investigation and, in broad terms, treatment direction.
In children below 8 years old, nephrotic syndrome is so frequently caused by minimal change disease — which responds to steroids — that empirical steroid therapy without biopsy is the international standard (KDIGO guidelines). If the child does not respond to steroids within 4 to 6 weeks (steroid-resistant nephrotic syndrome), biopsy is then required. In adults, the range of possible causes is far wider — membranous nephropathy, FSGS, minimal change disease, lupus nephritis, diabetic nephropathy, amyloidosis — and the treatment differs completely between them. Empirical steroid therapy in adults without biopsy is inappropriate except in specific clinical situations where the diagnosis is highly probable from serological findings alone (such as PLA2R-positive membranous nephropathy with typical clinical presentation).
Minimal change disease has the best prognosis — 80 to 90% of adults achieve complete remission with steroids, though relapses are common. Membranous nephropathy treated with rituximab achieves complete or partial remission in 60 to 70% at 24 months, with good long-term kidney survival in most patients who achieve remission. Primary FSGS is more variable — steroid-sensitive FSGS responds well, but steroid-resistant FSGS has a higher risk of progression to ESRD over years. Secondary causes (diabetic nephropathy, amyloidosis) are generally not curable but are manageable, with outcomes depending on control of the underlying condition. The KIMS approach gives each patient an honest and specific prognosis based on the biopsy diagnosis, clinical features, and response to initial treatment.
The risk of thrombosis in nephrotic syndrome is significantly elevated — particularly when serum albumin falls below 20 to 25 g/L. The mechanism is the urinary loss of anticoagulant proteins (protein C, protein S, antithrombin III) combined with elevated clotting factors (due to increased hepatic synthesis) and increased platelet reactivity. Deep vein thrombosis of the leg veins, renal vein thrombosis (which can cause acute flank pain and worsening proteinuria), and pulmonary embolism are all documented complications. The KIMS team assesses thrombotic risk at presentation and initiates prophylactic anticoagulation with low molecular weight heparin for high-risk patients — particularly those with serum albumin below 20 g/L or prior thrombotic events.
KIMS Secunderabad — Dr. Aswini Dutt T with specific glomerular disease subspecialty expertise (MCD, FSGS, membranous nephropathy, lupus nephritis), NABL-accredited pathology laboratory performing complete kidney biopsy workup (light microscopy + immunofluorescence + electron microscopy) in-house within 5 to 7 working days, real-time ultrasound-guided biopsy with same-day discharge protocol. PLA2R antibody testing and serum protein electrophoresis for comprehensive nephrotic syndrome workup. NABH accredited. Call 040 - 44885000.