Nephrotic Syndrome (Study Outline) 1. Background Definitio…
Nephrotic Syndrome (Study Outline) 1. Background Definition: A glomerular disorder characterized by heavy proteinuria (>3.5 g/day), hypoalbuminemia, edema, hyperlipidemia, and lipiduria. Pathophysiology: Injury to the glomerular filtration barrier (podocytes) → massive loss of protein → ↓ plasma oncotic pressure → edema and hepatic upregulation of lipoprotein synthesis. Common causes (high-yield): Primary: Minimal change disease (most common in children). Focal segmental glomerulosclerosis (FSGS). Membranous nephropathy (most common in adults). Secondary: Diabetes mellitus (leading cause). Amyloidosis. SLE (can cause nephritic or nephrotic). Infections (HIV, hepatitis), medications, malignancy. 2. History Edema—generalized, often periorbital in AM and dependent in PM. Foamy urine (due to proteinuria). Fatigue, weight gain from fluid retention. History clues for secondary causes: Longstanding diabetes, IV drug use, HIV risk, hepatitis exposure, autoimmune symptoms, malignancy. Thrombotic history: nephrotic state increases risk for DVT/PE. 3. Exam Findings Edema: pitting, generalized (anasarca in severe cases). Ascites, pleural effusions in advanced disease. Labs may manifest clinically: xanthelasma (hyperlipidemia). Possible hypertension (less pronounced than nephritic syndrome). Signs of underlying disease: diabetic retinopathy, purpura (amyloidosis rare), rash (SLE). 4. Making the Diagnosis Urinalysis: Massive proteinuria (>3.5 g/day). Oval fat bodies (“Maltese cross” under polarized light). Lipiduria, fatty casts. Blood tests: Hypoalbuminemia, hyperlipidemia (↑ LDL, ↑ triglycerides). May have normal or mildly low GFR initially. Serologic testing based on suspected etiology: Autoimmune panel (ANA, anti-dsDNA), hepatitis serologies, HIV testing. Renal ultrasound: typically normal-sized kidneys. Renal biopsy: Often required to determine etiology (minimal change vs. FSGS vs. membranous). Gold Standard: Renal biopsy demonstrating characteristic podocyte/glomerular changes consistent with specific nephrotic pathology. 5. Management (Exam Concepts) General principles: Control edema (concept-level: sodium restriction). Adjust medications based on GFR. Avoid nephrotoxins. Proteinuria reduction (high-yield exam concept): RAAS modulation principles for reducing intraglomerular pressure and protein loss. Hyperlipidemia management: conceptual treatment of elevated LDL/TG in nephrotic states. Thrombosis risk: nephrotic syndrome increases clot risk—recognize risk factors conceptually. Cause-directed (exam-level concepts): Minimal change disease: immunosuppression principles. FSGS: BP control, immunosuppression concepts. Membranous nephropathy: immunologic evaluation and immunosuppression principles. Diabetic nephropathy: optimize glucose/BP. Indications for referral: heavy proteinuria, unclear cause, or progression toward CKD. QUESTION A 36-year-old man presents with progressive swelling in his legs and face over the past two weeks. He also reports frothy urine and a recent 6-pound weight gain. He denies hematuria, joint pain, or rash. Medical history is significant for intravenous drug use. On exam, his blood pressure is 132/82 mmHg, and he has periorbital edema, pitting edema to the knees, and mild ascites. Laboratory studies: Urinalysis: 4+ protein, no hematuria, oval fat bodies 24-hour urine protein: 7.2 g Serum albumin: 2.1 g/dL (3.5–5.0) Serum creatinine: 1.1 mg/dL Total cholesterol: 294 mg/dL HIV test: positive Which of the following is the most likely diagnosis? A) Focal segmental glomerulosclerosisB) Membranous nephropathyC) Minimal change diseaseD) Diabetic nephropathy