Nephrotic Syndrome

Nephrotic syndrome is a clinical syndrome, not a single disease — it is the final common pathway of podocyte injury from many possible underlying glomerular diseases, defined by a tetrad that should be recognized as a whole rather than by any single feature in isolation: heavy ("nephrotic-range") proteinuria — classically ≥3.5 g/day in an adult, or an equivalent spot urine protein-to-creatinine ratio — hypoalbuminemia (serum albumin generally below 30 g/L, often well below 25 g/L when frankly nephrotic), edema, and hyperlipidemia.^[1][2] Each feature follows mechanistically from the one before it: podocyte injury lets albumin cross the glomerular filtration barrier faster than the liver can replace it; hypoalbuminemia lowers plasma oncotic pressure and, together with intrarenal sodium retention, drives edema; and the liver's compensatory increase in lipoprotein synthesis — an attempt to restore oncotic pressure that overshoots on the lipid side — produces the hyperlipidemia.

This chapter is deliberately organized around the syndrome itself: its own diagnostic workup, its own genuinely distinct complications (venous thromboembolism, infection risk, dyslipidemia), its own symptom-targeted and adjunctive pharmacotherapy (diuretics with albumin support where indicated, RAAS blockade, statins, and anticoagulation), and the corticosteroid-response classification that drives next-step decisions specifically for the primary podocytopathies — minimal change disease (MCD) and primary focal segmental glomerulosclerosis (FSGS). It deliberately does not re-derive the full etiology-by-etiology immunosuppression choice for membranous nephropathy, FSGS, or IgA nephropathy — that decision framework, and the nephritic-versus-nephrotic differential more broadly, is covered in this platform's Glomerulonephritis chapter, with IgA nephropathy covered in its own dedicated chapter; both are cross-referenced throughout rather than repeated.

How it presents

Edema is usually what brings a patient to care. In children, it classically starts as periorbital edema noticed on waking — often mistaken at first for allergies — before progressing over days to dependent edema of the legs and, in more severe cases, ascites, pleural effusion, and scrotal or labial edema. In adults the same progression occurs but is more often first noticed as new lower-extremity or dependent edema, unexplained rapid weight gain, or frothy/foamy urine (the high protein content lowers urine surface tension) rather than the classically pediatric periorbital sign.

Etiology differs sharply between children and adults — and that difference should shape the initial workup

Diabetic glomerulosclerosis (Kimmelstiel-Wilson nodules), H&E stain. Diabetic nephropathy is the leading overall cause of nephrotic syndrome in adults; a long-standing diabetes history with a compatible clinical picture (retinopathy present, gradual-onset proteinuria, no hematuria) is often enough to support the diagnosis without biopsy. (Wikimedia Commons contributor "KGH"; CC BY-SA 3.0 / GFDL)

Other secondary causes worth actively screening for

NSAIDs, lithium, interferon, and anti-VEGF agents (e.g., bevacizumab) are recognized drug-induced causes — bisphosphonates (particularly pamidronate) are specifically associated with a collapsing variant of FSGS.^[1] Hepatitis B, hepatitis C, and HIV infection are each associated with specific glomerular lesions (membranous nephropathy, membranoproliferative/cryoglobulinemic patterns, and HIV-associated nephropathy respectively) — see the Glomerulonephritis chapter. In an older adult, amyloidosis and other paraproteinemic diseases are an important and easily missed secondary cause; a serum/urine protein electrophoresis with immunofixation and free light chains is a reasonable addition to the standard workup in this population (see Assessment & Diagnosis and Special Populations).

• Age under 10 — the age range in which minimal change disease dominates the differential.^[2]
• Diabetes mellitus, particularly long-standing or poorly controlled — the leading overall cause of nephrotic syndrome in adults.
• Obesity and reduced nephron mass (a solitary kidney, low birth weight) — drivers of secondary/adaptive FSGS.
• Recent or ongoing NSAID use — a recognized cause of minimal change disease, particularly a new or relapsing presentation in an adult.
• Lymphoma, especially Hodgkin lymphoma — a classic paraneoplastic association with minimal change disease in adults; solid-organ malignancy is a recognized secondary cause of membranous nephropathy, particularly in older adults.^[1]
• Lithium, interferon, anti-VEGF agents (e.g., bevacizumab), and bisphosphonates (particularly pamidronate) — recognized drug-induced causes.
• Hepatitis B, hepatitis C, or HIV infection.
• A known plasma cell dyscrasia (multiple myeloma, monoclonal gammopathy) or systemic amyloidosis, or an older adult with unexplained nephrotic syndrome and no clear primary cause on initial workup.
• Systemic lupus erythematosus or another known autoimmune disease.
• A family history of childhood nephrotic syndrome, consanguinity, or onset in the first year of life — raises suspicion for a genetic (congenital/infantile) form; see Special Populations.

Confirming the tetrad

Quantify proteinuria with a first-morning or spot urine protein-to-creatinine ratio (24-hour collection is an acceptable alternative but adds collection burden without materially improving accuracy for most purposes). The KDIGO 2025 pediatric guideline's complete-remission threshold — a urine protein-to-creatinine ratio ≤200 mg/g (≤20 mg/mmol), or a negative/trace dipstick, or under 100 mg/m²/day, on 3 or more consecutive days — is also a practical, current reference point for what "proteinuria has resolved" means when tracking treatment response in either a child or an adult.^[2] Pair this with serum albumin, a fasting lipid panel, and serum creatinine/eGFR in every patient at diagnosis and at each significant change in status.

Secondary-cause workup

• HbA1c or fasting glucose, and a compatible history/retinopathy exam, when diabetic nephropathy is suspected.
• Hepatitis B and C serologies, and HIV testing where clinically indicated.^[1]
• ANA and complement levels where lupus nephritis is a possibility (see the Glomerulonephritis chapter).
• Serum and urine protein electrophoresis with immunofixation, and serum free light chains, particularly in an older adult without an obvious primary cause — screening for a paraproteinemic disease or amyloidosis.
• Serum anti-PLA2R antibody where membranous nephropathy is suspected (see the Glomerulonephritis chapter for the complete risk-stratification framework).
• A thorough medication history specifically for NSAIDs, lithium, interferon, anti-VEGF agents, and bisphosphonates.

When to biopsy — a genuinely different approach in children versus adults

In children with a typical presentation (age 1-10, no gross hematuria, normal complement, normal renal function, no significant hypertension), current guidance favours an empiric corticosteroid trial before biopsy — response itself is treated as strong evidence for minimal change disease, since MCD is overwhelmingly the most common cause in this group and is highly steroid-responsive.^[2] Biopsy is reserved for atypical features (age under 1 or over 12, gross hematuria, hypertension, significant renal impairment, low complement, or extrarenal features suggesting a systemic disease) or for steroid-resistant disease (see Choose Initial Treatment).^[2] In adults, the differential is far more heterogeneous and a specific treatable subtype cannot be assumed from the syndrome alone — biopsy is generally pursued upfront in most adults with new nephrotic syndrome, except when the clinical picture strongly and specifically fits a non-biopsied diagnosis (most commonly long-standing diabetes with a compatible course and retinopathy present).^[1] This is a genuinely important, easily-missed practice difference between the 2 populations, not simply a matter of a lower threshold in adults.

• Achieve remission (per the current KDIGO thresholds above) where corticosteroid-responsive disease is present, using the current shorter, evidence-based initial regimen rather than an older, unnecessarily prolonged one.
• Reduce proteinuria toward the lowest achievable level with RAAS blockade, independent of and in addition to any disease-specific immunosuppression.
• Control edema without over-diuresis — total-body fluid overload can coexist with intravascular depletion in severe hypoalbuminemia, so the acute kidney injury risk of aggressive diuresis is real and disproportionate in this population.
• Correct or at least meaningfully improve the dyslipidemia of nephrotic syndrome, recognizing it often improves as proteinuria responds to disease-specific treatment.
• Identify patients who genuinely need prophylactic anticoagulation for venous thromboembolism risk, rather than waiting for a clot to occur.
• Classify corticosteroid response correctly (steroid-sensitive, late-responder, infrequently/frequently relapsing, steroid-dependent, steroid-resistant) and let that classification, not a generic "more steroids" reflex, drive the next step.
• Recognize and act on the syndrome-specific emergencies — spontaneous bacterial peritonitis, VTE, and severe intravascular depletion — without delay (see Red Flags & Refer).

Corticosteroid response classification — drives every next step for minimal change disease and primary FSGS

• Sodium restriction (roughly under 2 g/day) — one of the most effective non-drug interventions for edema and supports diuretic efficacy directly.
• Individualized fluid restriction for significant edema, guided by the degree of volume overload rather than applied reflexively to every patient.
• Protein intake at a normal (not high) level — a high-protein diet does not correct hypoalbuminemia and may accelerate kidney disease progression.
• Daily weight monitoring is the single most practical tool for both the patient and the care team to detect a genuine change in fluid status early, whether worsening or improving.
• Home first-morning urine dipstick monitoring is commonly taught to parents of children with steroid-sensitive disease specifically to catch a relapse early, before edema becomes clinically obvious — a simple, low-cost, genuinely useful self-monitoring tool that is easy to overlook when counselling.
• Activity: avoid prolonged immobility given the elevated VTE risk, but avoid strenuous exertion during a period of significant edema or suspected intravascular depletion.
• Vaccination: pneumococcal vaccination is specifically recommended given the functional loss of opsonizing antibodies through urinary protein loss, which raises infection risk from encapsulated organisms independent of any immunosuppression used.^[2] Complete standard immunizations before starting significant immunosuppression wherever the clinical timeline allows; live vaccines are generally deferred once high-dose corticosteroids or another immunosuppressive agent is underway.
• Avoid nephrotoxins, particularly regular NSAID use — doubly relevant here since NSAIDs are also a recognized direct cause of minimal change disease.

Patient education

Teach patients and (for a child) caregivers to recognize the specific emergencies in this chapter as reasons to seek care immediately rather than waiting: fever with abdominal pain (possible peritonitis), new leg swelling/pain or sudden chest pain/shortness of breath (possible VTE), and signs of dehydration or reduced urine output during diuresis (possible intravascular depletion).^[2][4] Reinforce that RAAS inhibitor benefit is measured in proteinuria trend and long-term kidney survival, not day-to-day symptoms, and should not be stopped without discussion even when the patient feels well. Discuss fertility preservation before cyclophosphamide is started in anyone of reproductive age, and confirm effective contraception before mycophenolate mofetil in anyone who could become pregnant — see the Glomerulonephritis chapter.

Pediatrics

Minimal change disease dominates the differential and is highly steroid-responsive; the response classification above should drive every treatment decision. Congenital nephrotic syndrome (onset before 3 months of age, most often from NPHS1 or NPHS2 gene mutations) is a distinct, high-risk presentation that does not follow the framework above — it does not respond to corticosteroids, carries a high risk of severe complications (infection, thrombosis, malnutrition) from massive protein loss, and requires specialized management, sometimes including nephrectomy, dialysis, and eventual transplantation; refer immediately to pediatric nephrology rather than trialing a standard steroid course.^[2]

Pregnancy

Distinguishing nephrotic syndrome from preeclampsia is a genuinely important differential in pregnancy, since both can present with new proteinuria, edema, and hypertension — new or worsening hypertension, a rising uric acid, and onset after 20 weeks favour preeclampsia, while a known pre-existing glomerular disease, a normal blood pressure, and onset earlier in pregnancy favour a primary nephrotic process, though the 2 can also coexist. ACE inhibitors, ARBs, and statins are all contraindicated in pregnancy; RAAS blockade should be stopped before conception where feasible or as soon as pregnancy is confirmed. Where prophylactic anticoagulation is indicated in pregnancy, low-molecular-weight heparin is preferred over warfarin (teratogenic) or a DOAC (limited safety data, and the pharmacokinetic uncertainty in hypoalbuminemia above applies here too).^[3]

Older adults

Actively screen for a secondary cause — malignancy-associated membranous nephropathy, diabetic nephropathy, and amyloidosis/paraproteinemic disease — before assuming a primary immune-mediated process; see Assessment & Diagnosis. Older adults also carry a higher baseline infection risk on significant immunosuppression.

Renal impairment

Reduce diuretic and anticoagulant dosing as appropriate for reduced eGFR; several agents in this chapter require dose or interval adjustment as kidney function changes through disease progression — see the Chronic Kidney Disease chapter's general renal-dosing principles, which apply throughout this chapter as well.

Monitor daily weight, edema exam, and urine protein (dipstick at home for a steroid-sensitive child, urine protein-to-creatinine ratio at clinic visits for others) at a frequency individualized to disease activity and treatment phase.

During active diuresis

Serum electrolytes and renal function, particularly early in a diuretic course or after a dose increase — watch specifically for signs of intravascular depletion (rising creatinine, orthostatic symptoms) rather than assuming a rising creatinine simply reflects the underlying disease.

RAAS blockade

Serum creatinine and potassium 2-4 weeks after starting or up-titrating an ACE inhibitor or ARB, and periodically thereafter.

Corticosteroid and steroid-sparing therapy

Blood glucose, blood pressure, growth (in children), and bone health with prolonged corticosteroid use; taper per the specific regimen rather than stopping abruptly. See the Glomerulonephritis chapter's Monitoring & Follow-Up for the complete steroid-sparing-agent-specific monitoring (calcineurin inhibitor trough levels, cyclophosphamide cumulative dose, mycophenolate/azathioprine CBC and liver enzymes, rituximab hepatitis B screening).

Dyslipidemia and VTE surveillance

Recheck the lipid panel once remission is achieved to reassess ongoing statin need. Reassess VTE risk (serum albumin trend, degree and persistence of proteinuria) at each visit while nephrotic-range proteinuria persists, and maintain a low threshold to investigate new leg swelling, chest symptoms, or flank pain as a possible thrombotic event.^[4]

1. Steroid-resistant disease not yet biopsied or genetically tested: complete that workup before further immunosuppression — a genetic form will not respond regardless of agent, and confirming this changes the entire plan.^[2]
2. Confirmed immune-mediated steroid-resistant disease not responding to a calcineurin inhibitor: reassess adherence and trough levels first, then escalate per the Glomerulonephritis chapter's framework (rituximab or an alternative steroid-sparing regimen) in conjunction with nephrology.^[1]
3. Frequently relapsing or steroid-dependent disease not controlled on the chosen steroid-sparing agent: reconfirm the diagnosis, reassess adherence, and consider switching agent class (e.g., calcineurin inhibitor to rituximab, or vice versa) rather than simply extending the current regimen.
4. Diuretic-refractory edema despite an escalated loop diuretic, sequential nephron blockade, and an albumin trial where appropriate: reassess for a missed secondary contributor to edema (cardiac, hepatic, or venous insufficiency) and involve nephrology for consideration of ultrafiltration in genuinely refractory cases.
5. Persistent nephrotic-range proteinuria despite maximized RAAS blockade and disease-specific treatment: reconfirm the diagnosis is correct (a repeat biopsy is occasionally warranted) before assuming simple treatment failure, and reassess VTE/infection risk as ongoing, not resolved.
6. A VTE event occurring despite prophylaxis, or in a patient who was not on prophylaxis: treat as an acute VTE emergency in its own right (see the Venous Thromboembolism chapter for acute management) while urgently reassessing the anticoagulation strategy and the underlying diagnosis.^[4]

• Diagnosing or treating based on proteinuria alone without confirming the full tetrad (hypoalbuminemia, edema, hyperlipidemia) — isolated nephrotic-range proteinuria without the rest of the syndrome is a different clinical situation.
• Over-diuresing — total-body fluid overload can coexist with intravascular depletion in severe hypoalbuminemia, so aggressive diuresis carries a disproportionate acute kidney injury risk.
• Assuming every child's relapse, or even every child's initial presentation, needs biopsy before treatment — for a typical pediatric presentation, an empiric steroid trial is the current standard, with response itself treated as strong diagnostic evidence.^[2]
• Continuing an older, longer (16-24 week) initial corticosteroid regimen out of habit rather than the current, evidence-supported shorter 8-12 week course.^[2]
• Missing VTE risk assessment until after a clot has already occurred, particularly in membranous nephropathy or severe hypoalbuminemia.^[4]
• Starting a DOAC for VTE prophylaxis in severe hypoalbuminemia without acknowledging the genuine pharmacokinetic uncertainty this creates.^[3]
• Missing spontaneous bacterial peritonitis by attributing fever and abdominal pain in a nephrotic patient to ascites or a benign viral illness.^[2]
• Forgetting pneumococcal vaccination, given the functional antibody loss from urinary protein wasting.^[2]
• Using NSAIDs for symptomatic relief in a nephrotic patient — NSAIDs are themselves a recognized cause of minimal change disease and worsen both proteinuria and renal perfusion.
• Missing a secondary cause (malignancy, amyloidosis, diabetes) in an older adult by assuming primary immune-mediated disease by default.
• Confusing new nephrotic-range proteinuria and edema in pregnancy with preeclampsia (or vice versa) without considering both possibilities.
• Overstating the evidence for albumin-plus-diuretic combination therapy — it is a reasonable time-limited trial in severe, refractory hypoalbuminemic edema, not a well-established, strongly evidenced intervention.^[5]
• Re-deriving or restating the Glomerulonephritis chapter's etiology-specific immunosuppression framework here instead of cross-referencing it — kept out deliberately so the 2 chapters don't drift out of sync with each other over time.

How to use this table: Doses require patient-specific confirmation, including renal/hepatic adjustment where relevant. Steroid-sparing immunosuppressive agents (calcineurin inhibitors, cyclophosphamide, mycophenolate mofetil, rituximab) are covered in full, with complete dosing and monitoring detail, in the Glomerulonephritis chapter's Drug Tables and are not repeated here — this chapter's tables cover the syndrome-specific drugs (diuretics, albumin, RAAS blockade, statins, anticoagulation) plus first-line corticosteroid dosing. Select any drug name to open its complete Pharmasist Drug Database page.

Diuretics and Albumin Support for Nephrotic Edema

Nephrotic-range hypoalbuminemia reduces diuretic delivery to its site of action — higher doses are often genuinely needed for equivalent effect.

Renin-Angiotensin System Blockade

Foundational proteinuria reduction — start regardless of which disease-specific immunosuppression, if any, is also used.

Statin Therapy

For the dyslipidemia of nephrotic syndrome; reassess ongoing need once remission is achieved.

VTE Prophylaxis and Treatment

Consider specifically in severe hypoalbuminemia (roughly below 20-25 g/L), membranous nephropathy, or additional VTE risk factors — do not wait for a clot to occur.

First-Line Corticosteroid Therapy

For minimal change disease and primary FSGS induction and relapse treatment. See the Glomerulonephritis chapter's Drug Tables for steroid-sparing agents used in relapsing, dependent, or resistant disease.