Chapter 68: Nephritic Syndromes

Patient Story

An 8-year-old girl presents to the emergency room with severe headache and tea-colored urine of 2 days duration (Figure 68-1). She has just completed a 10-day course of amoxicillin for streptococcal pharyngitis. Her blood pressure upon arrival is 132/88. She is diagnosed with probable post-streptococcal glomerulonephritis and treated with salt restriction and a diuretic, and recovers.

Introduction

Nephritic syndrome is characterized by gross hematuria, acute kidney injury and retention of salt and water (manifested as hypertension with/without edema).

Synonyms

Acute glomerulonephritis, acute nephritis.

Epidemiology

• Peak incidence is between the age of 5 and 12 years.

• Post-streptococcal glomerulonephritis is uncommon in children less than 3 years of age.

• Incidence ranges from 9.5 to 28.5 per 100,000.¹

• Post-streptococcal glomerulonephritis is far more common in the developing countries.¹

Etiology and Pathophysiology

• Post-streptococcal glomerulonephritis is the most common cause of nephritic syndrome in children. It follows a pharyngeal or skin infection involving a nephritogenic strain of group A beta-hemolytic streptococci.

• Streptococcal antigens form immune complexes that activate a complement mediated cascade of inflammatory glomerular injury.²

• Less common etiologies for nephritic syndrome include: membranoproliferative glomerulonephritis, lupus nephritis, IgA nephropathy, Henoch-Schonlein purpura, infectious glomerulonephritis (commonly associated with endocarditis), and post-infectious glomerulonephritis due to other bacterial, viral, or parasitic etiologies.

• Rapidly progressive glomerulonephritis is a syndrome characterized by rapid loss of renal function (over a period of days to weeks) and the presence of glomerular crescents on renal biopsy (Figure 68-2). It represents the most severe presentation of any form of acute nephritis.³

Diagnosis

Clinical Features

• Nephritic syndrome classically presents with an abrupt onset of gross hematuria (tea-colored urine; Figure 68-1), oliguria, elevated blood pressure, and/or generalized edema.

• Onset of gross hematuria is 1 to 2 weeks following streptococcal pharyngitis and 3 to 6 weeks following streptococcal skin infection. In contrast, gross hematuria associated with IgA nephropathy commonly occurs concurrently with an upper respiratory infection.

• Mild (subclinical) cases of nephritis may be reflected by microscopic hematuria detected on urinalysis.⁴

Laboratory Testing

• Acute kidney injury is often present, manifested by variable elevation in serum creatinine.

• Urinalysis shows microscopic hematuria. Red blood cell casts confirm the glomerular origin of hematuria (Figure 68-3).

• Proteinuria may ...