AKT · Renal & urology/Glomerular disease

Nephrotic syndrome

Glomerular podocyte injury → heavy proteinuria, hypoalbuminaemia, oedema, hyperlipidaemia

Overview

The triad of heavy proteinuria (>3.5 g/24 h), hypoalbuminaemia and oedema, with hyperlipidaemia. In children it is almost always minimal change disease (steroid-responsive); in adults think membranous nephropathy, FSGS, diabetic nephropathy and amyloid. The complications that get tested are thromboembolism (lost antithrombin III), infection (lost immunoglobulin) and hyperlipidaemia.

Recognise

Generalised/periorbital oedema, frothy urine, weight gain; heavy proteinuria, hypoalbuminaemia, hyperlipidaemia
Children: minimal change disease (selective proteinuria, steroid-responsive). Adults: membranous (anti-PLA2R), FSGS, diabetic, amyloid, lupus (membranous)
Complications: VTE (renal vein thrombosis, PE — loss of antithrombin III), infection (loss of immunoglobulin), hyperlipidaemia

Red flags

Renal vein thrombosis / PE (loss of clotting inhibitors) — sudden flank pain/haematuria or pleuritic chest pain
Spontaneous bacterial peritonitis / infection in a nephrotic child (lost immunoglobulin + ascites)

Differentials & how to tell them apart

Nephritic syndrome / GNhaematuria + red-cell casts + hypertension predominate, lighter proteinuria

Cardiac/hepatic oedemaraised JVP / chronic liver disease, no heavy proteinuria

Diabetic nephropathylong-standing diabetes + retinopathy + albuminuria — cross-ref endocrine

Investigations

Urine protein quantification (ACR/PCR or 24-h), serum albumin and lipids, U&Es/eGFR; cause work-up — anti-PLA2R (membranous), HbA1c, immunology/complement, hepatitis/HIV, serum/urine electrophoresis (amyloid/myeloma); renal biopsy in adults (children with typical minimal change are treated empirically without biopsy).

Management

Children → empirical steroids (minimal change); adults → biopsy-guided; supportive diuretic + ACEi/ARB + statin

1Confirm the triad (heavy proteinuria + hypoalbuminaemia + oedema) and work up the cause. A child with typical features → empirical oral corticosteroids (minimal change disease) without biopsy.Gate: In adults (or atypical/steroid-resistant children) → renal biopsy to direct treatment; watch for and treat the thrombotic (renal vein thrombosis/PE) and infective complications.
2Treat the underlying cause/immunosuppression per biopsy; support with salt restriction + loop diuretic, ACE inhibitor/ARB for proteinuria, and a statin; anticoagulate thrombotic complications.

Children: oral corticosteroids (empirical for minimal change) — most are steroid-responsive; biopsy only if atypical/steroid-resistant

Adults: treat the underlying cause + immunosuppression as indicated — membranous/FSGS managed per biopsy; treat diabetes/amyloid/lupus

Supportive: salt/fluid restriction + loop diuretic for oedema; ACE inhibitor/ARB to reduce proteinuria; statin — manage oedema, proteinuria and hyperlipidaemia

Anticoagulation for thrombotic complications — treat (and in high-risk severe hypoalbuminaemia consider prophylaxis); treat infections promptly

Key points

Heavy proteinuria + hypoalbuminaemia + oedema = nephrotic syndrome. Child → minimal change (steroids, no biopsy). Adult → biopsy (membranous = anti-PLA2R; FSGS; diabetic; amyloid). Tested complications: VTE/renal-vein thrombosis (lost antithrombin III), infection (lost Ig), hyperlipidaemia.

Monitor & prognosis

Proteinuria/albumin, renal function, oedema/weight, lipids, thrombotic/infective complications.

Childhood minimal change usually responds to steroids (relapsing); adult causes vary by histology.

Source: KDIGO; cross-ref child_health (minimal change), endocrine (diabetic nephropathy)