Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (544 page)

*Lesions that resemble primary glomerular diseases are indicated in parentheses.
Source: Madaio MP, Harrington JT. The diagnosis of glomerular diseases: acute glomerulonephritis and the nephrotic syndrome.
Arch Intern Med.
2001;161(1):25–34.

   Laboratory Findings

   Urinalysis: Marked proteinuria: >3.5 g/24 hour in adults (normal protein excretion is <150 mg/24 hour) and >50 mg/kg/day in children. Albumin is the main urinary protein. Total protein-to-creatinine ratio (mg/mg) in a random urine specimen correlates closely with daily protein excretion in g/1.73 m
²
of body surface area. Minimal hematuria and azotemia may present but not part of the syndrome. Granular and epithelial cell casts are present in the urine.

   Decreased serum albumin (usually <2.5 g/dL) and total protein. Serum α
₂
and β-globulins are markedly increased, γ-globulin is decreased, and α
₁
-globulin is normal or decreased. If γ-globulin is increased, systemic diseases (e.g., SLE) should be ruled out.

   Changes secondary to proteinuria and hypoalbuminemia such as decreased serum calcium, decreased serum ceruloplasmin, and increased fibrinogen may be present.

   Hyperlipidemia: increased serum cholesterol, usually >350 mg/dL. Low or normal serum cholesterol levels may occur with poor nutrition and suggest poor prognosis. Serum triglycerides and total lipids are increased.

   Helpful serologic studies can be evaluated based on the clinical settings and may include ANA testing, complement (C3, C4), serum free light chains, and urine protein electrophoresis/immunofixation, syphilis and hepatitis B and C serology.

   Antithrombin III levels can be decreased in the blood due to its loss in the urine resulting in hypercoagulability. In addition, platelet hyperreactivity is found in 70% of patients and other abnormalities in coagulation factors, clotting inhibitors, and fibrinolytic system have been also described. Associated renal vein thrombosis has been reported in approximately 25% of cases.

   Renal biopsy establishes the diagnosis.

Suggested Reading

Loscalzo J. Venous thrombosis in the nephrotic syndrome.
N Engl J Med.
2013;368(10):956–958.

RADIATION NEPHROPATHY

   Definition

   This type of nephritis involves exposure of one or both kidneys to ionizing radiation (>2,000 rad). The injury is related to total dose and duration of radiation, and it affects approximately 20% of patients receiving radiation to kidneys.

   Latent period is 6–12 months for acute radiation nephropathy. Most affected individuals progress after >10 years to chronic nephritis with diminishing renal function and severe hypertension.

   Laboratory Findings