IgA Nephropathy Workup

  • Author: Mona Brake, MD; Chief Editor: Vecihi Batuman, MD, FACP, FASN   more...
 
Updated: Jan 5, 2012
 

Laboratory Studies

  • The first step in confirming the diagnosis is a careful urinalysis of a first-void urine sample performed by an experienced urine analyst. Direct examination of the urine sediment is required to identify RBCs and RBC casts, both of which indicate glomerular injury.
  • Quantitating proteinuria testing can be accomplished by a 24-hour measurement of urinary protein or semiquantitatively by measuring a urine protein/creatinine ratio. A normal ratio should be less than approximately 0.1. Also, adults older than 50 years with proteinuria should have a urine protein electrophoresis performed to exclude monoclonal light chains as a cause of proteinuria.
  • Assess renal function in patients with proteinuria or hematuria by a 24-hour creatinine clearance test, or the glomerular filtration rate (GFR) can be estimated using the Modification of Diet in Renal Disease (MDRD) formula.
  • Although the serum IgA level is elevated in up to half of patients, this finding is insensitive, nonspecific, and of no clinical utility.
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Procedures

  • Diagnosis of IgA nephropathy is confirmed by renal biopsy.
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Histologic Findings

Light microscopy

The most common light microscopy findings are focal or, more often, diffuse mesangial proliferation and extracellular matrix expansion (as seen in the image below). Morphology can range from normal to moderate or severe intracapillary or extracapillary proliferative lesions. While some patients have IgA deposits on immunofluorescence and little or no change by light microscopy, a few patients have segmental necrotizing lesions with crescent formation due to extensive disruption of the capillaries. Occasionally, patients have focal glomerular sclerosis indistinguishable from focal segmental glomerulosclerosis on light microscopy. A number of other findings can be observed in advanced disease, including interstitial fibrosis, tubular atrophy, and vascular sclerosis. These findings can be helpful prognostic tools in patients with IgA nephropathy.

Light microscopy of a glomerulus from a patient wiLight microscopy of a glomerulus from a patient with immunoglobulin A nephropathy showing increased mesangial matrix and cellularity.

Electron microscopy

Electron microscopy shows mesangial hypercellularity and increased mesangial matrix. The important finding is electron-dense deposits in the mesangium, such as those in the image below, but deposits in the subendothelial and subepithelial region of the glomerular capillary wall are found in a minority of patients, especially those with more severe disease.

Electron microscopy showing large dark mesangial dElectron microscopy showing large dark mesangial deposits.

Immunofluorescence

Immunofluorescence findings are the pathologic hallmark of this disease. IgA is deposited in a diffuse granular pattern in the mesangium (as seen in the image below) and occasionally in the capillary wall. Immunoglobulin G (IgG)4 may accompany IgA, and C3 is often present.

Immunofluorescence microscopy demonstrating large Immunofluorescence microscopy demonstrating large mesangial immunoglobulin A (IgA) deposits diagnostic of IgA nephropathy.
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Contributor Information and Disclosures
Author

Mona Brake, MD  Assistant Professor, Department of Internal Medicine, Kansas University School of Medicine

Mona Brake, MD is a member of the following medical societies: American College of Physicians and American Society of Nephrology

Disclosure: Nothing to disclose.

Coauthor(s)

Douglas Somers, MD  Assistant Professor, Department of Internal Medicine, Division of Nephrology, University of Iowa Medical Center

Douglas Somers, MD is a member of the following medical societies: American Society of Nephrology

Disclosure: Nothing to disclose.

Specialty Editor Board

James H Sondheimer, MD, FACP  Associate Professor of Medicine, Wayne State University School of Medicine; Medical Director of Hemodialysis, Harper University Hospital at Detroit Medical Center; Medical Director, DaVita Greenview Dialysis (Southfield)

James H Sondheimer, MD, FACP is a member of the following medical societies: American College of Physicians and American Society of Nephrology

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Christie P Thomas, MBBS, FRCP, FASN, FAHA  Professor, Department of Internal Medicine, Division of Nephrology, Medical Director, Kidney and Kidney/Pancreas Transplant Program, University of Iowa Hospitals and Clinics

Christie P Thomas, MBBS, FRCP, FASN, FAHA is a member of the following medical societies: American College of Physicians, American Heart Association, American Society of Nephrology, and Royal College of Physicians

Disclosure: Nothing to disclose.

Rebecca J Schmidt, DO, FACP, FASN  Professor of Medicine, Section Chief, Department of Medicine, Section of Nephrology, West Virginia University School of Medicine

Rebecca J Schmidt, DO, FACP, FASN is a member of the following medical societies: American College of Physicians, American Medical Association, American Society of Nephrology, International Society of Nephrology, National Kidney Foundation, Renal Physicians Association, and West Virginia State Medical Association

Disclosure: Renal Ventures Ownership interest Other

Chief Editor

Vecihi Batuman, MD, FACP, FASN  Professor of Medicine, Section of Nephrology-Hypertension, Tulane University School of Medicine; Chief, Medicine Service, Southeast Louisiana Veterans Health Care System

Vecihi Batuman, MD, FACP, FASN is a member of the following medical societies: American College of Physicians, American Society of Hypertension, American Society of Nephrology, and International Society of Nephrology

Disclosure: Nothing to disclose.

Additional Contributors

The authors thank Dr. Tim Timmerman, pathologist, for his invaluable help with the pathology slides.

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Light microscopy of a glomerulus from a patient with immunoglobulin A nephropathy showing increased mesangial matrix and cellularity.
Electron microscopy showing large dark mesangial deposits.
Immunofluorescence microscopy demonstrating large mesangial immunoglobulin A (IgA) deposits diagnostic of IgA nephropathy.
 
 
 
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