Focal Segmental Glomerulosclerosis Workup

Updated: Dec 07, 2020
  • Author: Sreepada TK Rao, MD, FACP; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Workup

Laboratory Studies

In patients with focal segmental glomerulosclerosis (FSGS), urinalysis reveals large amounts of protein, along with hyaline and broad waxy casts, whereas red blood cell (RBC) casts are generally absent. Broad casts may be observed in patients with advanced cases. Serum creatinine (SCr) concentration or creatinine clearance (CrCl) is usually within reference ranges in early stages.

In patients with idiopathic FSGS, investigational findings for an underlying etiology are generally negative. Such conditions may include the following:

  • Systemic lupus erythematosus (serum complement C4/C3 levels, antinuclear antibody/anti-DNA titers)
  • Hepatitis B or C infection
  • Vasculitis (antineutrophil cytoplasmic antibody titers, serum protein electrophoresis)

In patients thought to have secondary FSGS, obtain HIV antibody, CD4, and viral load studies; serology for hepatitis B and C; and parvovirus testing. Diagnosis of FSGS in morbidly obese patients is by excluding other causes. FSGS can be considered in patients with proteinuria on the basis of nephrotic syndrome; however, in young patients with an absence of RBC casts and negative serologic study findings, definitive diagnosis rests on a kidney biopsy.

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Histologic Findings

Kidney biopsy is the most definitive way to establish the diagnosis. The characteristic lesion in FSGS is segmental solidification of the glomerular tuft, usually in the perihilar region and sometimes in the peripheral areas, including the tubular pole. In the affected glomeruli, capillaries are segmentally obliterated by accumulation of acellular matrix and hyaline deposits, along with adhesion to the Bowman capsule. Coarsely granular deposits of IgM and C3 are often found in these areas.

Diffuse foot process fusion occurs, predominantly in the sclerotic segments, although partial effacement may be observed overlying normal-appearing lobules. Many morphologic subsets, such as a cellular variant (endocapillary and extracapillary hypercellularity), a collapsing variant (FSGS with mesangial hypercellularity), and FSGS with tip lesions (localized sclerotic lesions limited to the proximal tubular pole of the glomerulus) have been described (see Overview/Pathophysiology). Whether these diverse lesions reflect different pathogeneses or can account for the differences in the prognosis in patients with FSGS is unclear.

In HIV-associated FSGS, in addition to collapsing glomerular lesions with microcystic dilatation of renal tubules, electron microscopy of the kidney reveals tubuloreticular inclusions in endothelial and mesangial cells, an indirect marker of viral disease. [4, 5]

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Ultrasonography

In the early stages of FSGS, ultrasound examination reveals normal or large kidneys with increased echogenicity, suggesting diffuse intrinsic medical renal disease. In patients with advanced renal failure, kidneys are small and shrunken, indicating severe glomerular scarring and interstitial fibrosis. In HIV-associated FSGS, ultrasound generally reveals large echogenic kidneys.

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