Historically called the “nephritic syndrome.” Characterized by development, over days, of azotemia, hypertension, edema, hematuria, proteinuria, and sometimes oliguria. Salt and water retention are due to reduced glomerular filtration rate (GFR) and may result in circulatory congestion. Red blood cell (RBC) casts on urinalysis confirm diagnosis. Proteinuria is usually <3 g/d. Most forms of acute GN are mediated by humoral immune mechanisms. Clinical course depends on underlying lesion (Table 145-1 Causes of Acute Glomerulonephritis).
Acute Poststreptococcal GN
This is the prototype of the nephritic syndrome and the most common cause in childhood. Nephritis develops 1-3 weeks after pharyngeal or cutaneous infection with “nephritogenic” strains of group A β-hemolytic streptococci. Diagnosis depends on a positive pharyngeal or skin culture (if available), positive titers for antistreptococcal antigens (ASO, anti-DNAse, or antihyaluronidase), and hypocomplementemia. Renal biopsy reveals diffuse proliferative GN. Treatment consists of correction of fluid and electrolyte imbalance. In most cases, the disease is self-limited, although the prognosis is less favorable and urinary abnormalities are more likely to persist in adults.
Postinfectious GN
May follow other bacterial, viral, and parasitic infections. Examples are bacterial endocarditis, sepsis, hepatitis B, and pneumococcal pneumonia. Features are milder than with poststreptococcal GN. A specific IgA-dominant acute postinfectious GN, with a dominance of IgA deposits on immunofluorescence, can be seen after staphylococcal infections, particularly in diabetics. Control of primary infection usually produces resolution of postinfectious GN, but steroids are often administered in severe cases to avoid dialysis.