LabMed

Diseases of the Glomeruli

At a Glance

Urinalysis demonstrates the presence of proteinuria. A 24-hour urine collection is recommended when possible to confirm a loss of more than 3.5 grams of protein. The urine sediment is less likely to contain red cells or red cell casts; however, it may demonstrate oval fat bodies, which are indicative of hyperlipidemia.

Serum tests will reveal hypoproteinemia and hypoalbuminemia. Levels of cholesterol, apolipoprotein B, and triglycerides are typically elevated. Serum and urine electrophoresis should be considered in adults with nephrotic syndrome. Primary amyloidosis (AL amyloidosis) may occur with multiple myeloma or without other evidence of systemic disease and is characterized by deposition of immunoglobulin light chains. Secondary amyloidosis is associated with chronic inflammation and deposition of serum amyloid A protein (AA amyloidosis). Urinalysis dipsticks are more sensitive to the presence of albumin than to immunoglobulin light chains; the latter may be detected more readily and be characterized by urine immunofixation. The GFR may be estimated from serum creatinine levels using equations, such as the MDRD equation. A formal GFR measurement may be needed to determine and follow renal disease.

Patients with the nephrotic syndrome are at risk of having a hypercoagulable state because of renal loss of anti-thrombin III, protein C, protein S, and platelet activation.

Patients with HIV infection may develop HIV-associated nephropathy and are more commonly seen in African-American patients. This diagnosis should be considered, especially in patients with focal segmental glomerulosclerosis.

SLE can manifest both nephritic and nephrotic features, and, in a large percentage of patients, renal disease is significant. Renal biopsy should be considered when patients with SLE demonstrate hematuria or proteinuria.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

A basic panel of tests for evaluating suspected glomerular disease includes:

  • Urinalysis with microscopic examination of the urine sediment

  • Urine protein quantitation, preferably based on a 24-hour urine collection

  • Serum albumin, creatinine, BUN, electrolytes, and cholesterol

  • Creatinine glomerular filtration rate

If post-streptococcal glomerulonephritis is suspected, ASO, anti-DNAse, or anti-hyaluronidase tests may be useful, especially if rising titers are found.

Other tests that may be useful in establishing a diagnosis include:

  • Serum IgA levels

  • ANA

  • ANCA

  • Anti-GBM

  • Serum complement levels

  • Cryoglobulins

  • Serum and urine protein electrophoresis with immunofixation if an M-protein is found

  • Renal biopsy in patients with glomerular disease

What Lab Results Are Absolutely Confirmatory?

Renal biopsy provides a definitive diagnosis but may not be necessary (e.g., acute post-streptococcal glomerulonephritis).

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Glomerular filtration rate should be followed in patients with glomerular disease.

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