Nephrotic Syndrome Flare

A nephrotic syndrome (NS) flare/relapse is defined as the recurrence of nephrotic-range proteinuria (uPCR ≥2 g/g or dipstick ≥3+ for 3 consecutive days) in a patient who had previously achieved complete remission. [1-2] Life-threatening complications occur during 1–4% of flares, particularly when albumin is <20–25 g/L. [3] Relapse rates are high: 70–80% of adults with minimal change disease (MCD) relapse, with average time to relapse ~22 weeks. [4] In children, ~50% of steroid-sensitive patients develop frequently relapsing or steroid-dependent disease. [5]

• Onset and progression of edema — periorbital (morning), lower extremity, scrotal/labial, ascites [3]
• Foamy/frothy urine — often the first symptom noticed by patients [3]
• Antecedent upper respiratory infection — a common relapse trigger [6]
• Timing relative to steroid taper or discontinuation of immunosuppressive agents [1]
• Prior relapse frequency, steroid responsiveness, and time to last remission [1]
• Weight gain trajectory — quantify over days to weeks
• Medication adherence — particularly to steroids, CNIs, or MMF [7]
• Abdominal pain (peritonitis, renal vein thrombosis), dyspnea (pleural effusion, PE), headache (cerebral venous sinus thrombosis) [6]
• Decreased urine output — suggests AKI or hypovolemia [8]

• Shock/hypotension — hypovolemia from protein losses, aggravated by diuretics or sepsis; warrants urgent albumin infusion [3]
• Fever with abdominal pain — spontaneous bacterial peritonitis (SBP), reported in 1.5–16% of relapses [3]
• Unilateral leg swelling, pleuritic chest pain, dyspnea — DVT/PE; VTE risk is ~27% in adults with NS [2-3]
• Headache with neurological signs — cerebral venous sinus thrombosis [6]
• Oliguria/anuria — AKI complicating NS, especially in adults >50 with severe hypoalbuminemia [8]
• Severe respiratory distress — massive pleural effusion or pulmonary edema from albumin infusion [3]
• Albumin <2.0 g/dL — threshold for life-threatening complications including thrombosis and infection [2-3]

Relevant contributors and cautions:

• NSAIDs — can cause NS (interstitial nephritis with MCD) and worsen renal function; avoid during flares [6]
• Bisphosphonates, lithium, D-penicillamine, heavy metals — secondary causes of NS [6]
• DOACs (factor Xa inhibitors, direct thrombin inhibitors) — have significant albumin binding and are lost in nephrotic urine; pharmacokinetics are poorly studied; not recommended for anticoagulation in NS per KDIGO/KDOQI [7]
• Diuretics — use cautiously; can precipitate hypovolemia and AKI, especially in the setting of severe hypoalbuminemia [8-9]

Common treatments during flare:

• Loop diuretics (furosemide, bumetanide, torsemide) — first-line for edema; give BID; higher doses needed due to albumin binding in tubular lumen [2][9]
• Thiazide add-on (metolazone, HCTZ) — for diuretic resistance; give 2–5 hours before loop diuretic [2]
• ACEi/ARB — antiproteinuric effect; continue unless hypotensive or AKI [10]
• Corticosteroids — mainstay of relapse treatment (see Treatment Plan below) [1-2]
• Anticoagulation — heparin or warfarin if VTE risk > bleeding risk; use the UNC online tool for risk assessment [2][7]

• Sodium restriction: 1.5–2 g/day (60–90 mmol/day) during flares to manage edema and optimize diuretic response [2]
• Fluid restriction: recommended if Na <130 mEq/L (after excluding pseudohyponatremia from hyperlipidemia) [3]
• Protein intake: moderate protein intake (0.8–1 g/kg/day in adults); excessive protein does not replace urinary losses and may worsen hyperfiltration
• Avoid high-sodium processed foods during active disease
• Long-term: lipid-lowering diet given associated hyperlipidemia [11]

• Constitutional: fatigue, weight gain, malaise
• Respiratory: dyspnea (pleural effusion, PE), cough
• GI: abdominal pain/distension (ascites, SBP), nausea, decreased appetite
• GU: foamy urine, decreased urine output, hematuria (suggests atypical etiology)
• MSK: joint pain, rash (lupus nephritis)
• Neuro: headache, vision changes (cerebral venous thrombosis, posterior reversible encephalopathy syndrome)
• Skin: periorbital puffiness, scrotal/labial edema
• Infectious: fever, URI symptoms (relapse trigger), varicella exposure in immunosuppressed patients [3]

• Family history of NS or kidney disease — suggests genetic/hereditary forms, especially in steroid-resistant disease [3]
• Consanguinity — increases likelihood of monogenic NS [3]
• Medication compliance history from caregivers (especially in pediatric patients)
• Recent infections or sick contacts — URI is the most common relapse trigger [6-7]
• Vaccination status — particularly pneumococcal, meningococcal, varicella in immunosuppressed patients [3]
• Social context: access to medications, ability to monitor urine dipstick at home

• Steroid-dependent or frequently relapsing disease (≥2 relapses in first 6 months or ≥3/year) [1]
• Upper respiratory tract infections — most common trigger [6]
• Steroid taper or discontinuation — relapses commonly occur during or within 14 days of stopping steroids [1]
• Non-adherence to immunosuppressive therapy
• Underlying histology: MCD has highest relapse rate (~70–80% in adults); membranous nephropathy has highest VTE risk [2][4]
• VTE risk factors during flare: albumin <2.5 g/dL, female sex, BMI ≥30, AKI, sepsis, lupus nephritis, IV corticosteroid use, immobility [2][12]
• Age >50 (adults) — increased risk of AKI complicating MCD [8]

When a known NS patient presents with worsening edema, confirm true relapse vs. alternative causes:

• True NS relapse — recurrence of nephrotic-range proteinuria with hypoalbuminemia
• Heart failure — elevated JVP, S3, pulmonary crackles; BNP elevated; proteinuria typically subnephrotic
• Hepatic cirrhosis/liver failure — stigmata of liver disease, ascites predominant, low albumin from synthetic failure
• Medication-induced NS — NSAIDs, bisphosphonates, lithium [6]
• Secondary glomerulonephritis — lupus nephritis (low C3/C4, ANA+), membranoproliferative GN, IgA nephropathy; suspect if hematuria, hypertension, or low complement [3][6]
• Renal vein thrombosis — flank pain, hematuria, acute worsening of proteinuria; more common in membranous nephropathy [2]
• Infection-triggered transient proteinuria vs. true relapse — confirm with 3 consecutive days of dipstick ≥3+ [1]
• Progression to FSGS — 10–30% of adults initially diagnosed with MCD may have underlying FSGS on repeat biopsy [4]

• Number and timing of prior relapses — defines frequently relapsing vs. infrequently relapsing vs. steroid-dependent disease [1]
• Steroid responsiveness — steroid-sensitive vs. steroid-resistant [1]
• Prior immunosuppressive agents used and response (cyclophosphamide, CNIs, MMF, rituximab) [1][13]
• Prior complications: VTE, AKI, SBP, steroid side effects (osteoporosis, diabetes, cataracts, growth failure in children) [7]
• Renal biopsy results — histologic subtype (MCD, FSGS, membranous) [10]
• Baseline renal function and prior creatinine values
• Comorbidities: diabetes, hypertension, obesity, thrombophilia

• Vitals: blood pressure (hypertension or hypotension), heart rate (tachycardia if hypovolemic), weight (compare to dry weight), temperature (infection)
• General: cushingoid features (chronic steroid use), overall volume status
• Eyes: periorbital edema (often first sign, worse in morning) [3]
• Lungs: decreased breath sounds (pleural effusion), crackles (pulmonary edema)
• Cardiovascular: JVP assessment, S3 (to exclude heart failure)
• Abdomen: ascites (shifting dullness, fluid wave), tenderness/guarding (SBP), hepatomegaly
• Extremities: pitting edema (lower extremity, sacral), unilateral swelling (DVT)
• Genitalia: scrotal/labial edema [3]
• Skin: skin breakdown from severe edema, striae (steroid use)
• Neuro: mental status, focal deficits (cerebral venous thrombosis)

Recommended labs during a flare:

• Urinalysis with microscopy — confirm ≥3+ protein; assess for hematuria, casts [3][6]
• Spot urine protein-to-creatinine ratio (uPCR) — quantify proteinuria (≥2 g/g = nephrotic range) [1]
• Serum albumin — severity marker; <2.5 g/dL significantly increases VTE risk [2]
• BMP (creatinine, BUN, electrolytes) — assess renal function, hyponatremia [3]
• CBC — infection, hemoconcentration
• Lipid panel — hyperlipidemia is expected [10]
• Coagulation studies — if VTE suspected
• Blood cultures — if febrile or concern for SBP/sepsis

Rule-out labs (if atypical features or first presentation):

• Complement C3/C4, ANA, anti-dsDNA, ANCA, ASO titer — if hematuria, hypertension, or systemic symptoms [3][6]
• Hepatitis B/C, HIV — secondary causes [6]
• Anti-PLA2R antibodies — if membranous nephropathy suspected [14]

Monitoring parameters:

• Daily urine dipstick until remission, then at least twice weekly [3]
• Blood pressure and body weight twice weekly during relapse [3]

• Renal ultrasound — consider if reduced eGFR, hematuria, abdominal pain, or concern for renal vein thrombosis; also to exclude structural abnormalities [3]
• Chest X-ray — if dyspnea, to evaluate for pleural effusion or pulmonary edema
• Doppler ultrasound of renal veins/lower extremities — if clinical suspicion for DVT or renal vein thrombosis [2]
• CT pulmonary angiography — if PE suspected
• Routine imaging is not needed for uncomplicated relapses in patients with known NS [15]

• Urine dipstick — point-of-care confirmation of relapse (≥3+ for 3 consecutive days) [1]
• UNC Bleeding Risk Tool (www.med.unc.edu/gntools/bleedrisk.html) — online calculator to weigh VTE risk vs. bleeding risk for anticoagulation decisions in NS [2][7]
• Renal biopsy — indicated if atypical features (macroscopic hematuria, low C3, sustained hypertension, systemic symptoms), steroid resistance, or AKI not attributed to hypovolemia [3]
• Genetic testing — for congenital NS, primary steroid-resistant NS, or suspected syndromic forms [3]
• DEXA scan — every 12–18 months if prolonged or high cumulative steroid exposure [3]
• Ophthalmologic exam — yearly for cataracts/glaucoma screening with chronic steroid use [3]

• Indications: chest pain, dyspnea, tachycardia, or suspected PE/VTE
• Assess for right heart strain pattern (S1Q3T3, right axis deviation, RBBB) if PE suspected
• Electrolyte-related changes: hypokalemia (U waves, QT prolongation) from diuretic use; hyperkalemia if AKI develops
• Not routinely required for uncomplicated NS relapse

A nephrotic syndrome flare represents the recurrence of heavy proteinuria and hypoalbuminemia in a previously remitting patient, most commonly triggered by infection or steroid taper. Severity stratification is driven by the degree of hypoalbuminemia — albumin <2.0–2.5 g/dL marks the threshold for life-threatening complications including VTE (up to 27% in adults), AKI, and serious infection. [2-3][8]

Key considerations:

• Typical presentation: progressive edema, weight gain, foamy urine, fatigue
• Atypical features warranting further workup: hematuria, hypertension, low complement, systemic symptoms, AKI not from hypovolemia [3]
• Complications to anticipate: VTE (DVT, renal vein thrombosis, PE), SBP (especially in children), AKI (diuretic-induced hypovolemia or intrinsic from severe MCD), and infections due to immunoglobulin/complement losses [3][8][11]
• Relapse pattern classification (infrequent, frequent, steroid-dependent) guides long-term immunosuppressive strategy [1]

Initial stabilization (ED/acute setting)

• Assess volume status carefully — patients may appear volume-overloaded (edema) but be intravascularly depleted [3][9]
• If hypotensive/hypovolemic: IV albumin 25% (1 g/kg over 2–4 hours) with close monitoring for pulmonary edema [3]
• If euvolemic with significant edema: loop diuretics (furosemide 1–2 mg/kg IV or equivalent); consider co-administration with IV albumin for diuretic resistance [3]

Immunosuppressive therapy

Adults (MCD relapse):

• Infrequent relapse: prednisolone 20–30 mg/day (lower dose than initial treatment may suffice) until proteinuria remits, then taper [2]
• Frequent relapse/steroid-dependent: glucocorticoid-sparing agents — rituximab, cyclophosphamide, CNIs (cyclosporine/tacrolimus), or MMF per KDIGO 2021 [2][16]
• Rituximab has shown relapse reduction of ~5-fold in observational studies; a 2025 RCT confirmed efficacy for adult FRNS/SDNS [16]

Children (per KDIGO 2025):

• Relapse treatment: prednisone/prednisolone 60 mg/m²/day (max 60 mg) until complete remission for ≥3 days, then 40 mg/m² alternate days (max 40 mg) for 4 weeks [1]
• FRNS/SDNS: glucocorticoid-sparing agents recommended — options include CNIs, cyclophosphamide, levamisole, MMF, or rituximab [1][13]

Supportive care

• Sodium restriction 1.5–2 g/day [2]
• ACEi or ARB for antiproteinuric effect (hold if hypotensive or AKI) [10]
• VTE prophylaxis: mobilization, hydration, avoid central lines; consider anticoagulation (heparin/warfarin) if albumin <2.5 g/dL, especially in membranous nephropathy [2][7]
• Infection vigilance: low threshold for blood cultures and empiric antibiotics if febrile [3]

Admission criteria

• Severe/symptomatic edema (respiratory compromise, tense ascites, scrotal edema limiting mobility)
• Hemodynamic instability or signs of hypovolemic shock [3]
• AKI (rising creatinine, oliguria) [8]
• Suspected VTE (DVT, PE, renal vein thrombosis, cerebral venous thrombosis) [2]
• Suspected serious infection (SBP, sepsis, pneumonia) [3]
• Albumin <2.0 g/dL with inability to ensure close outpatient follow-up
• Need for IV diuretics or IV albumin

Discharge criteria

• Stable vital signs, improving edema, adequate oral intake
• Tolerating oral diuretics and steroids
• No evidence of AKI, VTE, or infection
• Reliable follow-up with nephrology arranged
• Patient/family able to perform home urine dipstick monitoring

Observation indications

• Moderate edema requiring IV diuretics with expected rapid response
• Borderline renal function requiring serial monitoring

Specialist consultation triggers

• Nephrology — all flares should have nephrology involvement for immunosuppressive management, consideration of steroid-sparing agents, and biopsy decisions [10]
• Hematology — if VTE occurs or complex anticoagulation decisions
• Infectious disease — atypical or severe infections in immunosuppressed patients

Follow-up timing

• Nephrology follow-up within 1–2 weeks of discharge or initiation of steroid therapy
• Repeat labs (albumin, creatinine, uPCR) at 1–2 weeks and at 4 weeks to assess response [2]
• If on steroid-sparing agents: drug levels (CNI trough), CBC, LFTs per agent-specific monitoring [3]

Symptoms requiring immediate reassessment

• Worsening edema despite treatment, rapid weight gain (>1 kg/day)
• Decreased urine output or dark/bloody urine
• Fever, abdominal pain (SBP), or signs of infection
• Unilateral leg swelling, chest pain, or sudden dyspnea (VTE/PE)
• Severe headache or neurological changes (cerebral venous thrombosis)

Patient counseling points

• Daily urine dipstick monitoring until remission, then at least twice weekly [3]
• Weigh daily; report weight gain >2 kg in 2–3 days
• Strict sodium restriction during active disease
• Do not abruptly stop steroids — taper as directed
• Avoid NSAIDs and nephrotoxins
• Ensure pneumococcal and influenza vaccinations are up to date [3]

Expected recovery course

• In steroid-sensitive disease, ~50% of adults respond by 4 weeks, with the remainder taking up to 16 weeks [4]
• Children typically respond faster, with most achieving remission within 1–2 weeks of steroid initiation [4]
• Edema resolves as proteinuria remits and albumin normalizes
• Relapse is common (~70–80% in adults with MCD), and patients should be counseled about long-term disease management and the potential need for steroid-sparing agents [4][16]

Images

1. KDIGO 2025 Clinical Practoice Guideline for the Mnagement of Nephrotic Syndrome in Children. — Garabed Eknoyan, Norbert Lameire, Wolfgang C. Winkelmayer, et al Kidney Disease: Improving Global Outcomes. 2025.

2. The 2021 Clinical Practice Guideline for the Management of Glomerular Diseases. — Pierre Ronco, Brad Rovin, Detlef Schiandorf, et al Kidney Disease: Improving Global Outcomes. 2021.

3. Childhood Nephrotic Syndrome. — Vivarelli M, Gibson K, Sinha A, Boyer O. Lancet. 2023.

4. Interventions for Minimal Change Disease in Adults With Nephrotic Syndrome. — Azukaitis K, Palmer SC, Strippoli GF, Hodson EM. The Cochrane Database of Systematic Reviews. 2022.

5. Tacrolimus or Mycophenolate Mofetil for Frequently Relapsing or Steroid-Dependent Nephrotic Syndrome. — Wang J, Liu F, Yan W, et al. JAMA Pediatrics. 2025.

6. Idiopathic Nephrotic Syndrome in Children. — Noone DG, Iijima K, Parekh R. Lancet. 2018.

7. KDOQI US Commentary on the 2021 KDIGO Clinical Practice Guideline for the Management of Glomerular Diseases. — Beck LH, Ayoub I, Caster D, et al. American Journal of Kidney Diseases : The Official Journal of the National Kidney Foundation. 2023.

8. Acute Kidney Injury Complicating Nephrotic Syndrome of Minimal Change Disease. — Meyrier A, Niaudet P. Kidney International. 2018.

9. The Nephrotic Syndrome. — Orth SR, Ritz E. The New England Journal of Medicine. 1998.

10. Diagnosis and Management of Nephrotic Syndrome in Adults. — Kodner C. American Family Physician. 2016.

11. Nephrotic Syndrome: Pathophysiology and Consequences. — Claudio P, Gabriella M. Journal of Nephrology. 2023.

12. Risk Factors of Venous Thromboembolism in Patients With Nephrotic Syndrome: A Retrospective Cohort Study. — Shinkawa K, Yoshida S, Seki T, Yanagita M, Kawakami K. Nephrology, Dialysis, Transplantation : Official Publication of the European Dialysis and Transplant Association - European Renal Association. 2020.

13. KDIGO 2025 Clinical Practice Guideline for the Management of Nephrotic Syndrome in Children. — Floege J, Gibson KL, Vivarelli M, et al. Kidney International. 2025.

14. Membranous Nephropathy. — Katie Trinh, Bhadran Bose Evidence-Based Nephrology, 2nd Edition. 2022.

15. Nephrotic Syndrome in Adults: Diagnosis and Management. — Kodner C. American Family Physician. 2009.

16. Rituximab for Relapsing Nephrotic Syndrome in Adults. — Isaka Y, Sakaguchi Y, Shinzawa M, et al. The Journal of the American Medical Association. 2025.