What are the key differences between Nephritic Syndrome and Nephrotic Syndrome, and how do they relate to Acute Kidney Injury (AKI)?

From the Guidelines

To effectively teach final year medical students about nephritic syndrome, nephrotic syndrome, and acute kidney injury (AKI), a comprehensive approach focusing on clinical presentation, pathophysiology, diagnosis, and management is essential. When discussing nephritic syndrome, it is crucial to emphasize the classic presentation of hematuria, proteinuria (<3.5g/day), hypertension, and decreased GFR, as well as the underlying causes such as post-streptococcal glomerulonephritis, IgA nephropathy, and lupus nephritis 1. The diagnostic workup should include urinalysis showing RBC casts, serum creatinine, complement levels, and potentially renal biopsy. Treatment varies by underlying cause but may include steroids, immunosuppressants, and supportive care.

For nephrotic syndrome, the tetrad of heavy proteinuria (>3.5g/day), hypoalbuminemia, edema, and hyperlipidemia should be highlighted, along with the pathophysiology involving podocyte damage leading to increased glomerular permeability 1. Common causes include minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, and diabetic nephropathy. Management includes ACE inhibitors or ARBs, such as enalapril 5mg daily or losartan 50mg daily, diuretics like furosemide 20-40mg daily for edema, statins for hyperlipidemia, and specific treatments for underlying causes.

When teaching about AKI, the KDIGO definition and classification system based on creatinine and urine output, as outlined in the 2012 KDIGO clinical practice guideline, should be used 1. The teaching should be organized around pre-renal (volume depletion, heart failure), intrinsic (ATN, glomerulonephritis), and post-renal (obstruction) causes. Emphasis should be placed on the importance of early recognition, daily monitoring of fluid balance, electrolytes, and creatinine, and prompt management of the underlying cause. Practical aspects like indications for renal replacement therapy, medication dose adjustments, and prevention strategies in high-risk patients should also be included.

Key points to cover in the teaching include:

• Nephritic syndrome: clinical presentation, pathophysiology, diagnosis, and management
• Nephrotic syndrome: clinical presentation, pathophysiology, diagnosis, and management
• AKI: definition, classification, pre-renal, intrinsic, and post-renal causes, early recognition, and management
• Importance of early recognition and prompt management of AKI to reduce morbidity and mortality
• Practical aspects of AKI management, including renal replacement therapy and medication dose adjustments.

From the Research

Nephritic and Nephrotic Syndrome

• Nephrotic syndrome is characterized by edema, proteinuria, hypoalbuminemia, and hyperlipidemia 2
• The most common causes of nephrotic syndrome in children are idiopathic minimal change disease and focal segmental glomerulosclerosis (FSGS), while in adults, FSGS and membranous nephropathy (MN) are the most common primary causes 2
• Nephritic syndrome is associated with hematuria and proteinuria, and abnormal kidney function, and carries a poorer prognosis, typically associated with hypertension 3
• The most common causes of nephritic syndrome are post-infectious GN, IgA nephropathy, and lupus nephritis 3

Diagnosis and Management

• Diagnosis of nephrotic syndrome involves measuring proteinuria and serum albumin and lipid levels, and evaluating for secondary causes 2
• In children, most cases of nephrotic syndrome are due to minimal change disease, which is responsive to steroid treatment 2
• In adults, biopsy is typically indicated for diagnosis, except in patients with positive test results for serum anti-phospholipase A2 receptor antibodies, which is diagnostic of MN 2
• Management of nephrotic syndrome involves reduction of proteinuria with glucocorticoids, and alternative therapies for frequent recurrences and/or steroid-resistant cases 2

Acute Kidney Injury (AKI)

• AKI is a common complication in patients with nephrotic syndrome, and can be caused by hypovolemia, nephrotoxic medications, and infections 4
• Urinary biomarkers such as KIM-1 and NGAL can be used to diagnose AKI in patients with nephrotic syndrome, and to differentiate between acute tubular necrosis and proliferative glomerulonephritis 5
• AKI in nephrotic syndrome can be multifactorial in origin, and requires prompt diagnosis and treatment to improve patient outcomes 4
• There is limited data on the correlation between AKI in pediatric nephrotic syndrome and long-term outcomes, highlighting the need for further research in this area 4