Diagnosis guide for clinicians
IgA nephropathy: when to suspect it and what to test
IgA nephropathy is an autoimmune kidney disease in which deposits of IgA and other antibodies damage the glomeruli, so the kidneys leak blood and protein into the urine.NIDDK
A 2026 JAMA review reports that about 60% of cases are found incidentally on urinalysis, and up to 30% present with episodic visible hematuria, often during an infection.JAMA review
A 2025 narrative review notes that glomerular hematuria without persistent proteinuria of 0.5 to 1g/day does not typically trigger a biopsy in adults, which delays diagnosis.Child vs adult narrative review
Red flags for IgA nephropathy
What the cited sources describe, grouped by life stage and organ. Each line links to its source.
Visible hematuria with infections
- Episodic visible hematuria, often during an upper respiratory or gastrointestinal tract infection (synpharyngitic hematuria), is the presentation in up to 30% of adults.JAMA review
- In children, IPNA suggests considering IgA nephropathy when gross hematuria during an upper respiratory infection lasts over 2 to 3 weeks or recurs over 2 to 3 times.IPNA pediatric recommendations
- A 2025 review of pediatric and adult cohorts found gross hematuria at presentation in 60% to 88% of children and 15% to 20% of adults.Child vs adult narrative review
- NIDDK describes pink or cola-colored urine and notes that first signs may follow a cold, sore throat or other respiratory infection.NIDDK
Persistent microscopic hematuria
- About 60% of adult cases are detected incidentally, with hematuria or proteinuria found on urinalysis.JAMA review
- Isolated microscopic hematuria of glomerular origin was once regarded as benign, but a Clinical Medicine review links it to a higher long-term risk of kidney failure.Clinical Medicine hematuria review
- The same review names IgA nephropathy, Alport syndrome and thin basement membrane nephropathy as the most common causes of isolated microscopic hematuria in children and young adults.Clinical Medicine hematuria review
- The ERA working group notes that the extent of microhematuria is associated with IgA nephropathy progression.ERA working group on KDIGO 2025
Proteinuria
- NIDDK lists foamy urine from proteinuria and swelling of the legs, feet or ankles among common signs.NIDDK
- IPNA recommends considering IgA nephropathy in children with hematuria plus UPCR of 0.2mg/mg or more persisting over 2 to 3 weeks on 2 clear samples, and normal C3.IPNA pediatric recommendations
- In the Travere-funded UK RaDaR cohort analysis, 30% of patients with time-averaged proteinuria of 0.44 to under 0.88g/g developed kidney failure within 10 years.RaDaR long-term outcomes
- The same Travere-funded analysis found kidney failure within 10 years in about 20% of patients with time-averaged proteinuria under 0.44g/g.RaDaR long-term outcomes
Hypertension, including in younger adults
- IgA nephropathy usually occurs in younger adults, with a reported mean age at diagnosis of 34 to 45 years.JAMA review
- A 2025 review found hypertension at biopsy in 22% to 37% of adults under 65 in most cohorts, and in 7% to 12% of children.Child vs adult narrative review
- The same review reports that hypertension at diagnosis is associated with poor kidney outcomes.Child vs adult narrative review
- NIDDK notes that kidney damage from IgA nephropathy can raise blood pressure, and high blood pressure can further damage the kidneys.NIDDK
Reduced eGFR, nephrotic or rapidly progressive presentations
- The KDIGO 2025 executive summary says most patients already have established chronic kidney disease at diagnosis, more or less advanced.KDIGO 2025 executive summary
- A 2025 review reports eGFR at diagnosis of 50 to 88mL/min/1.73m2 in adults, against 90 to 128mL/min/1.73m2 in children.Child vs adult narrative review
- Older adults are more likely to present with reduced eGFR, hypertension, acute kidney injury and higher proteinuria than younger patients.Contemporary review
- Nephrotic syndrome and rapidly progressive glomerulonephritis are less common presentations, each reported in under 5% of adults.JAMA review
Family history and associated conditions
- NIDDK lists a family history of IgA nephropathy or IgA vasculitis as making the disease more likely.NIDDK
- NIDDK also lists celiac disease, hepatitis, cirrhosis and HIV infection as conditions linked to IgA nephropathy.NIDDK
- A 2026 Frontiers in Medicine study states that one in seven people with IgA nephropathy has another apparently affected family member.Familial IgAN genetics study
Ancestry, sex and age
- NIDDK says IgA nephropathy is more common in people of East Asian or white European ancestry, in males and at ages 10 to 40.NIDDK
- A 2024 review reports greater prevalence and more severe presentations in Pacific-Asian populations, and says the disease is much less common in African Americans but does occur.Contemporary review
- The same review notes that age at diagnosis has been rising; RaDaR's median adult age rose from 40 years in 2013 to 45 years in 2020.Contemporary review
Often mistaken for
Diagnoses patients commonly carry first, and why the sources say they are confused.
| First diagnosis | Why it is confused |
|---|---|
| Urinary tract infection | IPNA lists urinary tract infection among the lower urinary tract causes of hematuria to exclude before glomerular causes are pursued.IPNA pediatric recommendations |
| Kidney stones or hypercalciuria | IPNA lists stones, hypercalciuria and hypocitraturia as lower urinary tract causes; in one Thai series of children with gross hematuria, 22% had hypercalciuria and 15.7% had IgA nephropathy.IPNA pediatric recommendations |
| Benign isolated microscopic hematuria | Glomerular microscopic hematuria was previously regarded as benign, but it carries a higher long-term risk of kidney failure even without proteinuria, hypertension or reduced function.Clinical Medicine hematuria review |
| Thin basement membrane nephropathy or Alport syndrome | Both cause persistent glomerular hematuria; IPNA says collagen type IV disease should be kept in mind with a family history of hematuria and chronic kidney disease.IPNA pediatric recommendations |
| Post-infectious glomerulonephritis | IPNA describes post-infectious hematuria starting 1 to 3 weeks after an upper respiratory infection, with low C3 and raised antistreptococcal titers, unlike hematuria during the infection.IPNA pediatric recommendations |
| IgA-dominant infection-related glomerulonephritis | It shows IgA-dominant deposits and must be excluded on clinical or pathologic grounds before primary IgA nephropathy is diagnosed.JAMA review |
| IgA vasculitis | IPNA says kidney biopsy findings are indistinguishable from IgA nephropathy; purpuric rash, abdominal pain and joint pain point to the systemic disease.IPNA pediatric recommendations |
| Lupus nephritis | The JAMA review lists lupus nephritis among other causes of nephritic syndrome to assess when IgA nephropathy is suspected.JAMA review |
| Essential hypertension alone | A 2025 review attributes most hypertension in older adults with IgA nephropathy to comorbid essential hypertension, while noting it could also be caused by IgA nephropathy.Child vs adult narrative review |
Codes patients often carry before this diagnosis
For spotting the pattern in a problem list or registry. Descriptions are checked daily against NLM's ICD-10-CM service; this is not coding advice.
R31.0Visible blood in the urine, often during an infection, is a classic IgA nephropathy presentation.JAMA review
R31.21, R31.29, R31.9Persistent microscopic hematuria is a common finding when IgA nephropathy is first suspected.JAMA review
R80.0, R80.1, R80.8, R80.9KDIGO 2025 ties considering a kidney biopsy to proteinuria of 0.5g/day or more in adults.KDIGO 2025 IgAN guideline
N18.1, N18.2, N18.30, N18.31, N18.32, N18.4, N18.5, N18.9Most patients already have chronic kidney disease when IgA nephropathy is diagnosed.KDIGO 2025 executive summary
What to test, step by step
The testing order the cited guidance describes, by who it applies to. It summarizes published guidance and is not a plan for any one patient.
Adults with blood on a urine dipstick or visible hematuria
- Urinalysis with microscopy
The 2020 AUA/SUFU guideline defines microhematuria as 3 or more red blood cells per high-power field on microscopic evaluation of a single specimen.AUA/SUFU microhematuria guideline
Children suspected of IgA nephropathy, per IPNA
- Urine sediment for red cell count and morphology
IPNA lists urine sediment for erythrocyte count and morphology in the initial workup. It defines persistent microscopic hematuria as 5 or more red cells per high-power field on 2 samples at least 1 month apart.IPNA pediatric recommendations
Anyone with suspected IgA nephropathy
- Quantify proteinuria
The JAMA review says the initial workup should include quantification of proteinuria, along with assessment for other causes of nephritic syndrome.JAMA review
- Serum creatinine and eGFR
IPNA lists creatinine and eGFR in the initial workup, using the Schwartz formula for children.IPNA pediatric recommendations
- Tests to exclude other causes
The JAMA review lists IgA vasculitis, IgA-dominant infection-related glomerulonephritis, and secondary IgA nephropathy from cirrhosis, inflammatory bowel disease, celiac disease, viral hepatitis or autoimmune disease.JAMA review
Children, per IPNA
- First-morning UPCR or 24-hour protein
IPNA and KDIGO 2021 favor a first-morning UPCR over a 24-hour collection in children. A first-morning sample also excludes orthostatic proteinuria.IPNA pediatric recommendations
- Complement, serum IgA and autoimmune serologies
IPNA lists serum IgA and C3 at diagnosis, ANA, dsDNA, ENA and ANCA as appropriate, and hepatitis B, hepatitis C, syphilis and HIV tests before steroids and as appropriate.IPNA pediatric recommendations
Children with hematuria and low-grade proteinuria
- Repeat urine measurements
IPNA bases most thresholds on at least 2 measurements on clear urine 1 to 2 weeks apart, persisting beyond 2 to 3 weeks. Its lowest biopsy band needs 3 measurements.IPNA pediatric recommendations
Children before kidney biopsy, per IPNA
- Kidney ultrasound
IPNA lists kidney ultrasound for echogenicity and size as mandatory before a kidney biopsy.IPNA pediatric recommendations
Adults in whom IgA nephropathy is possible
- Kidney biopsy: who
KDIGO 2025 Practice Point 1.2.1 says a biopsy should be considered in all such adults with proteinuria of 0.5g/day or more, unless biopsy is contraindicated.KDIGO 2025 IgAN guideline
Adults with suspected IgA nephropathy
- Kidney biopsy: the ERA group's reading
The ERA working group adds decreased eGFR as an indication. It says isolated microhematuria with proteinuria under 0.5g/day and normal eGFR is generally not one.ERA working group on KDIGO 2025
Children with persistent or recurrent hematuria
- Kidney biopsy: pediatric thresholds
IPNA recommends prompt biopsy with UPCR above 2mg/mg or eGFR under 90mL/min/1.73m2, and biopsy with UPCR above 0.5mg/mg. It suggests biopsy at 0.2 to 0.5mg/mg on at least 3 measurements.IPNA pediatric recommendations
Anyone biopsied for suspected IgA nephropathy
- What the biopsy must show
Diagnosis needs light microscopy and immunofluorescence showing dominant or co-dominant glomerular IgA, after excluding other causes. IPNA says electron microscopy is helpful but not required.IPNA pediatric recommendations
Every IgA nephropathy biopsy
- Oxford MEST-C score
The 2016 Oxford update scores mesangial and endocapillary hypercellularity, segmental sclerosis, tubular atrophy or interstitial fibrosis, and crescents. The update reports that M, S and T predict outcome in specimens with at least 8 glomeruli, and adds C.Oxford Classification 2016
Clinicians reading the biopsy report
- How guidelines use MEST-C
The ERA group says KDIGO 2021 and 2025 use MEST-C for prognosis, not to choose a treatment regimen. It contrasts this with IPNA's pediatric guidance, which gives MEST-C central weight in therapy decisions.ERA working group on KDIGO 2025
Adults with biopsy-proven IgA nephropathy, at the time of biopsy
- International IgAN Prediction Tool
Built from 3,927 patients in multiethnic cohorts, it combines eGFR, blood pressure and proteinuria at biopsy with MEST, age, medication use and optionally race. It estimates risk of a 50% eGFR decline or kidney failure.International IgAN Prediction Tool paper
Clinicians using the tool
- Limits of the prediction tool
KDIGO 2025 says the tools have not been evaluated for predicting the impact of any treatment and should not be used to choose a specific therapy. Adult and pediatric versions exist, at biopsy and 1 or 2 years after.KDIGO 2025 IgAN guideline
Family history of hematuria and chronic kidney disease, or no response to treatment
- Genetic testing in familial hematuria
IPNA says collagen type IV variants should be kept in mind, with genetic testing or alpha-5(IV) chain staining on a skin or kidney biopsy.IPNA pediatric recommendations
Where testing goes wrong
- The KDIGO 2025 executive summary lowered the 2021 proteinuria goal of under 1g/day to under 0.5g/day, ideally under 0.3g/day, citing risk at lower levels.KDIGO 2025 executive summary
- The Travere-funded RaDaR analysis found high 10-year kidney failure rates in patients with proteinuria under 0.88g/g, a group traditionally regarded as low risk.RaDaR long-term outcomes
- In a Manitoba cohort of 380 adults, time to biopsy differed nearly threefold between physicians for otherwise similar patients.Kidney360 biopsy timing study
- The same study linked lower proteinuria, higher eGFR and rural residence to longer waits, and its authors suggest underestimated lifetime risk may have contributed to deferred evaluation.Kidney360 biopsy timing study
- IPNA separates the two infection patterns by timing: gross hematuria during an upper respiratory infection supports IgA nephropathy, as opposed to hematuria 2 to 3 weeks after it.IPNA pediatric recommendations
- IPNA lists low C3 in post-infectious glomerulonephritis and lupus nephritis, while its criteria for suspecting IgA nephropathy include a normal C3.IPNA pediatric recommendations
- A random urine sample in a child can reflect orthostatic proteinuria; IPNA recommends a first-morning void for all children with proteinuria.IPNA pediatric recommendations
- After a benign genitourinary cause of microhematuria, the 2020 AUA/SUFU guideline says to repeat the urinalysis once that cause resolves.AUA/SUFU microhematuria guideline
- IPNA does not recommend immunosuppression before biopsy unless rapidly progressive disease is suspected, and says RAS blockers should not delay the biopsy.IPNA pediatric recommendations
- A 2024 review says no biomarker is acceptable to diagnose IgA nephropathy; serum galactose-deficient IgA1 is also raised in some healthy first-degree relatives.Contemporary review
- Mesangial IgA is not specific; IgA vasculitis, IgA-dominant infection-related glomerulonephritis and secondary IgA nephropathy must be excluded.JAMA review
- Apparent familial IgA nephropathy may reflect a coexisting genetic kidney disease such as Alport syndrome or ADTKD-HNF1B.Familial IgAN genetics study
- Before FY2024, the ICD-10-CM index sent IgA nephropathy to N02.8; the FY2024 addenda revised that entry to N02.B-.ICD-10-CM FY2024 addenda
- The CDC FY2024 conversion table lists N02.B1 to N02.B9 as effective October 1, 2023, with prior codes N02.0 to N02.8 depending on the lesion.ICD-10-CM FY2024 conversion table
Where to test
- Urinalysis, urine microscopy and urine protein: Routine tests ordered through any clinical laboratory. IPNA lists urine sediment for red cell count and morphology, and a first-morning UPCR or 24-hour protein.IPNA pediatric recommendations
- Blood tests: creatinine, eGFR, complement and serologies: Routine blood tests available through any clinical laboratory. Which serologies apply depends on the clinical picture, as the cited sources describe.IPNA pediatric recommendations
- Kidney biopsy through nephrology: Done through a nephrology service. NIDDK says a kidney biopsy is needed to make the diagnosis and that nephrologists treat most cases.NIDDK
Family screening and referral
Who else in the family
- NIDDK lists a family history of IgA nephropathy or IgA vasculitis as a factor that makes the disease more likely.NIDDK
- NIDDK says IgA nephropathy cannot be prevented, and suggests people with a family history ask their health care professional how to keep their kidneys healthy.NIDDK
- In a single-center Chinese cohort of 348 familial and 1,116 sporadic cases, familial disease carried a 40% higher gender-adjusted lifetime risk of kidney failure.Familial IgAN lifetime risk study
- In that cohort, 57% of familial cases were diagnosed by biopsy; the rest were diagnosed clinically.Familial IgAN lifetime risk study
- The same study reported a median age at kidney failure of 60 years for familial cases and 65 years for sporadic cases.Familial IgAN lifetime risk study
- In a study of 11 families, at least 5 had variants consistent with a coexisting genetic kidney disease. The authors say people from families with IgA nephropathy should be offered genetic testing.Familial IgAN genetics study
- A Clinical Medicine review calls a detailed family history with screening of at-risk relatives important when glomerular hematuria is found.Clinical Medicine hematuria review
Who to refer to
- The KDIGO 2025 executive summary says the guideline now encourages a more liberal kidney biopsy policy than the 2021 version.KDIGO 2025 executive summary
- KDIGO 2025 Practice Point 1.2.1 says a biopsy should be considered in all adults with proteinuria of 0.5g/day or more in whom IgA nephropathy is possible.KDIGO 2025 IgAN guideline
- The ERA working group also names decreased eGFR as a biopsy indication, and says that without a biopsy, close monitoring of proteinuria and eGFR remains mandatory.ERA working group on KDIGO 2025
- The 2026 JAMA review states that adults with suspected IgA nephropathy and proteinuria of 0.5g/day or more should undergo kidney biopsy.JAMA review
- NIDDK says nephrologists treat IgA nephropathy in most cases.NIDDK
- For children, IPNA recommends a kidney biopsy in any child with signs of IgA nephropathy and an unexplained eGFR fall of more than 50% within 3 months.IPNA pediatric recommendations
- IPNA advises genetic testing to explore collagen type IV disease when there is a family history of hematuria and chronic kidney disease.IPNA pediatric recommendations
Find a specialist by state
From the CMS NPI Registry, a public directory of US clinicians by registered specialty. A listing is not an endorsement and says nothing about experience with IgA nephropathy; patient organizations and academic centers can often name experienced clinicians.
ICD-10-CM codes for IgA nephropathy
For orders, referrals and prior authorization. Each code is checked daily against NLM's ICD-10-CM service.
Once the diagnosis is confirmed
For the patient: why your doctor ordered this test
Plain language a patient can read or take home.
Your doctor ordered these tests to check for a kidney disease called IgA nephropathy.
Blood or protein in your urine can be a sign of this disease.
In IgA nephropathy, a germ-fighting protein called IgA builds up in the tiny filters of your kidneys and can hurt them.
A urine test looks for blood cells and checks how much protein is in your urine.
Blood tests show how well your kidneys clean your blood and help rule out other causes.
The only way to know for sure is a kidney biopsy.
A doctor takes a tiny piece of kidney and looks at it under a microscope.
Questions clinicians ask about IgA nephropathy testing
When is a kidney biopsy indicated for suspected IgA nephropathy?
KDIGO 2025 Practice Point 1.2.1 says a biopsy should be considered in all adults with proteinuria of 0.5g/day or more in whom IgA nephropathy is possible. The ERA working group also names decreased eGFR, and calls isolated microhematuria with lower proteinuria and normal eGFR generally not an indication. A 2026 JAMA review states that adults with suspected IgA nephropathy and proteinuria of 0.5g/day or more should undergo biopsy.
Can IgA nephropathy be diagnosed without a kidney biopsy?
No, KDIGO 2025 says IgA nephropathy can be diagnosed only with a kidney biopsy, as there are no validated serum or urine biomarkers. IPNA says the biopsy must show dominant or co-dominant glomerular IgA on immunofluorescence, after other causes are excluded.
What labs should be ordered before referral for suspected IgA nephropathy?
Sources list urinalysis with microscopy, quantified proteinuria by UPCR or 24-hour collection, and serum creatinine with eGFR. IPNA adds serum IgA and C3 at diagnosis and other serologies as appropriate. The JAMA review lists IgA vasculitis, infection-related glomerulonephritis and secondary causes as diagnoses to exclude.
How do you tell synpharyngitic hematuria from post-infectious glomerulonephritis?
Timing and C3 are the main clues IPNA describes: synpharyngitic hematuria occurs during an upper respiratory infection, while post-infectious hematuria starts 1 to 3 weeks after it. IPNA lists low C3 and a raised antistreptococcal titer for post-infectious disease, and a normal C3 among its criteria for suspecting IgA nephropathy.
What is the ICD-10 code for IgA nephropathy?
ICD-10-CM codes IgA nephropathy under N02.B, recurrent and persistent immunoglobulin A nephropathy, per the NLM lookup checked November 8, 2026. Codes N02.B1 to N02.B6 specify the lesion, and N02.B9 covers other forms. The CDC FY2024 addenda added them effective October 1, 2023, moving the index entry from N02.8 to N02.B-.
Sources
- IgA Nephropathy - NIDDK. National Institute of Diabetes and Digestive and Kidney Diseases, NIH, 2022-09.
- Executive summary of the KDIGO 2025 Clinical Practice Guideline for the Management of Immunoglobulin A Nephropathy (IgAN) and Immunoglobulin A Vasculitis (IgAV). Kidney International 2025;108:548-554 (Floege J et al; supported by KDIGO), full text via KDIGO, 2025-10.
- KDIGO 2025 Clinical Practice Guideline for the Management of Immunoglobulin A Nephropathy (IgAN) and Immunoglobulin A Vasculitis (IgAV). Kidney International 2025;108(4S):S1-S71 (KDIGO IgAN and IgAV Work Group; supplement sponsored by KDIGO), full text via KDIGO, 2025-10.
- The 2025 KDIGO IgA nephropathy guideline update: an ERA Immunonephrology Working Group perspective. Clinical Kidney Journal (Stamellou E et al; no funding declared), via PubMed Central, 2025-10-22.
- IgA Nephropathy in Adults: A Review. JAMA (Stoneman S, Teh JW, O'Shaughnessy MM), via PubMed abstract, 2026-03-03.
- IPNA clinical practice recommendations for the diagnosis and management of children with IgA nephropathy and IgA vasculitis nephritis. Pediatric Nephrology 2025;40:533-569 (Vivarelli M et al; funded by the International Pediatric Nephrology Association), via PubMed Central, 2024-09-27.
- Oxford Classification of IgA nephropathy 2016: an update from the IgA Nephropathy Classification Working Group. Kidney International (Trimarchi H et al), via PubMed, 2017-03-22.
- Evaluating a New International Risk-Prediction Tool in IgA Nephropathy. JAMA Internal Medicine (Barbour SJ et al; Canadian Institutes of Health Research funding), via PubMed Central, 2019-04-13.
- Physician Variability in Time to Kidney Biopsy and Glucocorticoid Prescription in IgA Nephropathy: A Population-Based Cohort Study. Kidney360 (Barr B et al; no funding), via PubMed Central, 2026-05-14.
- Is Childhood IgA Nephropathy Different From Adult IgA Nephropathy? A Narrative Review. Canadian Journal of Kidney Health and Disease (Alladin-Karan A et al), via PubMed Central, 2025-03-12.
- Long-Term Outcomes in IgA Nephropathy. Clinical Journal of the American Society of Nephrology (Pitcher D et al; funded by Travere Therapeutics), via PubMed Central, 2023-04-13.
- Contemporary review of IgA nephropathy. Frontiers in Immunology (Filippone EJ, Gulati R, Farber JL), via PubMed Central, 2024-08-12.
- Isolated microscopic haematuria of glomerular origin: clinical significance and diagnosis in the 21st century. Clinical Medicine, Royal College of Physicians (Chan MM, Gale DP), via PubMed Central abstract, 2015-12.
- Coexisting genetic kidney disease explains many cases of 'familial' IgA nephropathy where the proband has biopsy-confirmed mesangial IgA deposits. Frontiers in Medicine (Li et al; no financial support), via PubMed Central, 2026-03-02.
- Increased Lifetime Risk of ESRD in Familial IgA Nephropathy. Kidney International Reports (Shi M et al), via PubMed Central, 2020-10-20.
- Microhematuria: AUA/SUFU Guideline. Journal of Urology (Barocas DA et al; American Urological Association and SUFU), via PubMed abstract, 2020-07-23.
- ICD-10-CM search results for "immunoglobulin A nephropathy" (Clinical Table Search Service). National Library of Medicine, 2026-11-08.
- ICD-10-CM 2024 Addenda (Tabular List and Index to Diseases and Injuries), icd10cm-addendum-2024.zip. National Center for Health Statistics, CDC, 2023-10-01.
- ICD-10-CM-Conversion-Table-FY2024-Effective-10-01-2023-Final (updated 9-21-2023).xlsx. National Center for Health Statistics, CDC, 2023-09-21.
A reference for licensed professionals, checked against its sources on November 8, 2026. It summarizes what the cited guidance says and does not tell anyone how to diagnose or treat a specific patient. Guidelines change; the current guideline and the treating clinician's judgment govern. Trial Friend is an independent information service, not a medical provider.