Membranous Glomerulonephritis Workup

Updated: Oct 09, 2019
  • Author: Abeera Mansur, MD; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Workup

Laboratory Studies

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  • Urine microscopy: Urine sediment is typically nephrotic, with oval fat bodies and fatty casts; however, in mild cases, the urinalysis may reveal proteinuria without formed elements in the sediment.

  • Serum creatinine

  • Blood urea nitrogen

  • Serum albumin

  • Proteinuria (quantitative) with a 24-hour urine collection: A ratio of spot urine protein to creatinine is easier to obtain, and the findings may be sufficient for screening purposes.

  • Creatinine clearance

  • Antinuclear antibodies

  • Anti–double-strand DNA, if results from antinuclear antibody testing are positive

  • Hepatitis B serology (if positive, DNA quantitation)

  • Hepatitis C (if positive, RNA quantitation)

  • Syphilis serology

  • Complement levels

  • Cryoglobulin, particularly if hepatitis C and/or low levels of complement are found

  • Lipid profile

  • Urinary C5b-9

  • Urinary beta-2 microglobulin (worse prognosis with an increased level)

  • Malignancy workup: An exhaustive workup for malignancy is not recommended because most cases of membranous nephropathy are not associated with cancer. However, because some increase in the rate of occult malignancy is recognized in patients with newly diagnosed membranous nephropathy, (1) ensure that age-appropriate health screening (eg, mammography, sigmoidoscopy) has been performed, and (2) investigate any clues from the initial patient history and physical examination.

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Imaging Studies

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  • Sonogram

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Procedures

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  • Renal biopsy: Definitive diagnosis is made based on findings from a renal biopsy.

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Histologic Findings

Pathologic features can be observed using light microscopy, immunofluorescence microscopy, and electron microscopy.

  • Light microscopy: The mesangium is normal, with no hypercellularity. All glomeruli are involved. The capillary walls are thickened with patent capillary lumina. Subepithelial deposits are seen; with trichrome stain, they are shown to have spikes.

  • Immunofluorescence microscopy: Use strong granular capillary wall staining for immunoglobulin G (IgG), with C3 and both kappa and lambda light chains.

  • Electron microscopy

    • A considerable diversity of prognosis is seen with idiopathic membranous nephropathy. In a study of 105 patients with idiopathic membranous nephropathy, 2 different groups were identified on the electron microscopic findings. In the homogeneous type, only 1 patient developed end-stage renal failure, and earlier remission occurred in this group. With regard to secondary outcome, increased age, focal segmental glomerular sclerosis, arteriolosclerosis, and heterogeneous type of electron microscopic findings were independent risk factors.

    • Stage 1: Features appear normal using light microscopy, but, with electron microscopy, a few electron-dense deposits are seen along the capillary walls.

    • Stage 2: Numerous and larger deposits with spikes are seen.

    • Stage 3: New extracellular material surrounds the deposits.

    • Stage 4: Initial electron-dense deposits become electron-lucent, and capillary walls become thickened.

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Other Tests

Measurement of anti-PLA2R antibodies in serum and detection of PLA2R antigen in glomerular deposits can now be done routinely. Anti-PLA2R antibodies have high specificity (close to 100%), sensitivity (70-80%), and predictive value. [13]

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