Acute poststreptococcal GN
Done by Dr.Ali Abdul-RazakObjectives To know the causes of hematuria The causes of proteinuria To differentiate between nephrotic and nephritic syndromes
Acute poststreptococcal glomerulonephritis
It is characterized by sudden onset of gross hematuria, edema, hypertension and renal insufficiency. It is the second most common cause of gross hematuria after IgA nephropathy.Etiology: It follows infection of the throat (cold weather) or skin (warm weather) by certain nephritogenic strain of group A beta hemolytic streptococci. Pathology: evidence suggests that immune complexes, preformed by the combination of specific antibodies against streptococcal antigens, localize on the glomerular capillary wall and activate the complement system.
Immunofluorescence microscopy : reveals a lumpy-bumpy deposits of immunoglobulin and complements on the GBM. Electron microscopy: there is electron dense deposits or humps on the epithelial side of GBM . On light microscopy: All glomeruli appear enlarged with diffuse mesangial cell proliferation with increase in the mesangial matrix
Clinical manifestations: It is most common in children 5-12 years old and uncommon before the age of 3 years. Male-to-female ratio is 2:1 The typical nephritis syndrome occurs 1-2 weeks after a strep. Pharyngitis or 3 weeks after strep. Pyoderma. Presentations may vary from asymptomatic microscopic hematuria to acute renal failure.
There is a various degree of edema in 85% of cases (due to salt and water retention) starts as periorbital then may become generalized. Gross hematuria occurs in 30-50% of patients. The urine is usually described as being smoky, cola colored, tea colored, or rusty. Oliguria may be noted.
Hypertension is the third cardinal feature of PSAGN and is reported in 50-90% of children who are hospitalized with AGN. Hypertension is multifactorial and may be related to ECF volume expansion. Hypertensive encephalopathy has been reported in approximately 5% of hospitalized children and is the most serious early complication of this disease.
Dyspnea, orthopnea, and cough may be present. Pulmonary rales are often audible. Also there may be fever, malaise, lethargy and abdominal pain The acute phase resolves within 6-8 weeks. The urinary protein excretion and hypertension normalize by 4-6 weeks after the onset but microscopic hematuria may persist 1-2 years.
Diagnosis: Urinalysis show: RBC and RBC cast, hyaline cast. proteinuria 3+ by dipstick, corresponding to fewer than 2 g/m2/d.
2. Evidence for streptococcal infection: Cultures from either the pharynx or skin may be positive. Antibodies to a variety of streptococcal antigens (eg, Antistrepolysin O, Antihyalurinidase Ab, anti-DNase B). A mild anemia (normocytic, normochromic) is common due to hemodilution and low grade hemolysis.
Serum complement C3 level is reduced in the acute phase and returns to normal 6-8 weeks after the onset. Mild elevation of blood urea and creatinine. Electrolytes are normal except in patients with RF. Renal biopsy is indicated only in: a-Acute RF b-Nephrotic syndrome c-Absent evidence for strep. Infection d-Normal complement C3 level or if remain low 2 mo after the onset
Differential diagnosis: Other causes of hematuria: A-Glomerular hematuria: IgA nephropathy (Burger disease). Alport syndrome (hereditary nephritis) Membranous nephropathy Membranoproliferative GN
5. Focal segmental GN 6. Henoch-Schonlein purpura 7. SLE nephritis 8. Hemolytic uremic syndrome 9. Sickle cell glomerulopathy
B- Extraglomerular hematuria: Pyelonephritis, cystitis Acute tubular necrosis Hydronephrosis, polycystic kidney, Wilms tumor and trauma. Urolithiasis Munchausen-by-proxy syndrome
Complications: Hypertensive encephalopathy manifested by headache, vomiting, depressed sensorium, confusion, visual disturbances, aphasia, memory loss, coma, and convulsions. Acute renal dysfunction with increase urea, creatinine, hyperphosphatemia, hypocalcaemia and acidosis. Heart failure and pulmonary congestion.
Prognosis: Complete recovery occurs in more than 95% of cases Recurrences are extremely rare. Prevention: Early systemic antibiotic therapy for strep. Infection does not eliminate the risk of GN.
Treatment: 10 days course of penicillin is recommended to limit the spread of nephritogenic organisms. Dose <12 years: 25-50 mg/kg/d PO divided tid/qid Hospitalization is indicated if the child has significant hypertension or a combination of oliguria, generalized edema, and elevation of serum creatinine or potassium.
Mild-to-moderate hypertension is treated most effectively with bed rest, fluid restriction, and small dose of antihypertensive medications such as furosemide (1-3 mg/kg/d PO, administered 1-2 times daily) For patients resistant to treatment, either hydralazine or nifedipine is indicated.
Angiotensin-converting enzyme inhibitors (ACEI) are effective, although they have the potential to produce hyperkalemia and usually are not first-line drugs in AGN. Diet: A low-sodium, low-protein diet should be prescribed during the acute phase, when edema and hypertension present.