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Nephrotic syndrome
Nephrotic syndrome is massive protein leak through the kidney filter (above 3.5 g a day) with low albumin and oedema; in adults the commonest primary cause is membranous nephropathy, and the complication to remember is hypercoagulability.
Why it matters in the exam
Exam questions present marked oedema, "frothy" urine, a very low albumin and high cholesterol, and ask about the cause, the next test or a complication. The candidate must separate nephrotic (heavy protein, a "quiet" urine sediment) from nephritic (blood and red cell casts, hypertension). As for causes: membranous nephropathy is linked to the anti-PLA2R antibody, and in an older adult a tumour must be sought; minimal change disease is linked to NSAIDs and Hodgkin disease and responds well to steroids; FSGS is linked to obesity, HIV and heroin use; and amyloidosis appears with myeloma or chronic inflammatory disease.
Complications are tested just as often: venous thrombosis — especially renal vein thrombosis in membranous disease, with sudden flank pain and haematuria — because antithrombin III is lost in the urine; infections with encapsulated bacteria; and hyperlipidaemia. General treatment includes an ACEi or ARB to reduce protein, diuretics and salt restriction, a statin and sometimes prophylactic anticoagulation when albumin is very low. Diabetes is the commonest secondary cause of nephrotic-range protein in adults. In children, by contrast, most cases are minimal change disease, so a child with typical nephrotic syndrome receives steroids without a biopsy, whereas an adult almost always needs a biopsy to decide treatment. Remember too that the oedema of nephrotic syndrome appears first around the eyes in the morning and later in the legs and abdomen.
Key points
- Nephrotic: protein above 3.5 g a day, albumin below 3 g/dL, oedema and hyperlipidaemia.
- In adults: membranous (anti-PLA2R), FSGS, minimal change, diabetes and amyloidosis.
- Minimal change: NSAIDs and Hodgkin, responds to steroids.
- Complications: thrombosis (renal vein), infections and hyperlipidaemia.
- General treatment: ACEi or ARB, diuretics, statin, and anticoagulation when albumin is below 2.5 g/dL in membranous disease.
Summary table
| Disease | Associations and clues | Diagnostic test | Treatment |
|---|---|---|---|
| Membranous nephropathy | Adults; tumours, NSAIDs, hepatitis B, lupus | Serum anti-PLA2R; biopsy | Supportive; rituximab at moderate-high risk |
| Minimal change disease | NSAIDs, Hodgkin; common in children | Biopsy: podocyte foot-process effacement on electron microscopy | Prednisone; good response |
| FSGS | Obesity, HIV, heroin, African ancestry | Biopsy: focal sclerosis | Primary: steroids; secondary: treat the cause |
| Diabetic nephropathy | Long-standing diabetes, retinopathy | Gradually rising albuminuria | ACEi/ARB, SGLT2 inhibitor, finerenone |
| Amyloidosis | Myeloma, chronic inflammation | Congo red stain: apple-green birefringence | Treat the underlying disease |
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Sources
- KDIGO Clinical Practice Guideline for the Management of Glomerular Diseases, 2021 — Nephrotic syndrome; membranous nephropathy; minimal change disease; FSGS
- Harrison's Principles of Internal Medicine, 21st edition (2022) — Glomerular Diseases
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.
See also: in children: Nephrotic syndrome in children