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KembaraXtra -Medicine- Nephrotic Syndrome
Nephrotic syndrome is a clinical disorder caused by defects in the glomerular filtration barrier that lead to heavy protein loss in the urine. It is defined by nephrotic-range proteinuria greater than 3 g per 24 hours, hypoalbuminemia with serum albumin below 3 g/dL, peripheral edema, hyperlipidemia, lipiduria with oval fat bodies and fatty casts, and associated hypogammaglobulinemia. The altered glomerular basement membrane becomes excessively permeable due to immune complexes, nephrotoxic antibodies, or nonimmune mechanisms, allowing loss of albumin and other large proteins.
The pathophysiology centers on increased glomerular protein filtration and reduced plasma oncotic pressure, resulting in sodium and water retention and edema. Severe hypoalbuminemia may cause postural hypotension, syncope, or shock. Hyperlipidemia develops as hepatic lipoprotein synthesis increases in response to low oncotic pressure. Patients are at increased risk of thromboembolic events, particularly when serum albumin is very low, protein excretion is high, fibrinogen levels are elevated, and antithrombin III levels are reduced.
Nephrotic syndrome may arise from primary renal diseases or secondary systemic conditions. In adults, membranous nephropathy is the most common primary cause and may be associated with chronic infections such as hepatitis B or C or autoimmune disease. Minimal change disease accounts for most pediatric cases and typically responds well to corticosteroids. Focal segmental glomerulosclerosis affects adolescents and young adults and may be primary or secondary to conditions such as HIV, obesity, or heroin use. Diabetic nephropathy is the most common secondary cause in adults and is heralded by microalbuminuria. Other causes include systemic lupus erythematosus, monoclonal gammopathies such as amyloidosis and multiple myeloma, HIV-associated nephropathy, preeclampsia, hepatitis, and drug-induced disease.
Clinical presentation varies widely. Many patients are asymptomatic aside from foamy urine and gradual weight gain from fluid retention. Edema may range from mild pitting edema to generalized anasarca with ascites and pleural effusions. Hypertension or hypotension may occur depending on intravascular volume status. Hematuria may be present, particularly with renal vein thrombosis. Acute dyspnea, tachycardia, or hypotension should raise concern for pulmonary embolism, a recognized complication of the hypercoagulable state.
Evaluation begins with urinalysis demonstrating heavy proteinuria and lipiduria with oval fat bodies. Laboratory studies reveal hypoalbuminemia, hyperlipidemia, and possible anemia. Quantification of proteinuria is performed with a 24-hour urine collection or protein-to-creatinine ratio. Additional testing is guided by suspected systemic disease and may include autoimmune markers, hepatitis serologies, and serum or urine protein electrophoresis. Renal ultrasound is useful in secondary causes, and renal biopsy is the definitive diagnostic test when response to steroids is poor or etiology is unclear.
Management focuses on treating the underlying cause and controlling complications. Sodium restriction and cautious diuresis with loop diuretics are used to manage edema, avoiding overly aggressive fluid removal to prevent renal failure and thrombosis. ACE inhibitors or ARBs reduce proteinuria and slow progression of renal disease. Corticosteroids are the mainstay for primary nephrotic syndromes, particularly minimal change disease. Anticoagulation is indicated for confirmed thromboembolic events and may be considered prophylactically in patients with profound hypoalbuminemia. Lipid-lowering therapy and nutritional support are important adjuncts.
Hospital admission is required for patients with severe edema, respiratory compromise, acute renal failure, thromboembolic complications, or significant comorbid disease. Stable patients without complications may be managed as outpatients with close nephrology follow-up. Long-term prognosis depends on the underlying cause, degree of proteinuria, blood pressure control, and response to therapy, with vigilant monitoring essential to reduce complications and progression to chronic kidney disease.
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