Table 2.
KDIGO Kidney Function and Disease Glossary: suggested terms to describe kidney function and kidney disease, and criteria and measures defining them
| Preferred term | Suggested abbreviationsa | Rationale/explanation | Terms to avoid | |
|---|---|---|---|---|
| Part 1. Kidney Function and Disease | The term “kidney” should be used preferentially when describing kidney disease and kidney function, with exceptions | “Renal,” the prefix “nephro-” (except in the setting of specific functions, diseases, or syndromes; see below) | ||
| Kidney disease | Reflects the entirety of acute kidney diseases and disorders and chronic kidney disease | Renal disease, nephropathy (except in the setting of specific diseases, e.g., membranous nephropathy) | ||
| Kidney function | Reflects the entirety of different and complex physiological functions of the kidney; should not be equated with glomerular filtration rate (GFR) only | Renal function (except when describing specific functions, e.g., renal acidification, renal concentrating mechanism) | ||
| Normal kidney function | General term applicable to various aspects of kidney function that should be specified | |||
| Abnormal kidney function | General term applicable to various aspects of kidney function that should be specified | Renal/kidney impairment, insufficiency, dysfunction; azotemia | ||
| Residual kidney function | RKF | Kidney function in people with kidney failure receiving KRT; further specification is required, e.g., urine flow rate, solute clearance. Although it is usually used in the setting of dialysis, this term could be used to refer to native kidney function in kidney transplant recipients. | Residual renal function (RRF) | |
| Kidney structure | Reflects the entirety of different and complex structures of the kidney, ascertained by imaging and markers of injury and damage | Renal structure (except when describing specific structures within the kidney, such as artery, vein, capsule, parenchyma, cortex, medulla, glomeruli, tubules, interstitium, cysts, tumors) | ||
| Normal kidney structure | General term applicable to various aspects of kidney structure that should be specified | |||
| Abnormal kidney structure | General term applicable to various aspects of kidney structure that should be specified | |||
| Causes of kidney disease | Cause of AKI, AKD, and CKD should be indicated whenever possible. Cause may be known, presumed, or unknown. Method for ascertainment and attribution of cause should be specified. | Cause should not be inferred only from presence of comorbid condition (such as diabetes) | ||
| Part 2. Kidney Failure | GFR <15 ml/min per 1.73 m2 or treatment by dialysis; further specification is required; see below | Renal failure (RF); end-stage renal disease (ESRD); end-stage kidney disease (ESKD); renal disease; nephropathy; renal/kidney impairment, insufficiency, dysfunction; azotemia | ||
| Duration | Specification preferred | |||
| Acute kidney injury stage 3b | AKI stage 3 | Disease duration ≤3 months | Acute renal failure; renal disease; nephropathy; renal/kidney impairment, insufficiency, dysfunction; azotemia; uremia | |
| Kidney failure | KF | Disease duration >3 months | Chronic renal failure; chronic renal disease; chronic nephropathy; chronic renal/kidney impairment, insufficiency, dysfunction; azotemia; uremia; irreversible kidney failure | |
| Symptoms and signs | Specification preferred (with, without, or unknown symptoms and signs); with symptoms and signs would be synonymous with uremia | |||
| Uremia/uremic syndrome | A syndrome consisting of symptoms and signs associated with kidney failure (does not indicate a causal role for urea) | |||
| Treatment | Specification required | |||
| Kidney replacement therapyc | KRT | Further specification is required; includes dialysis and transplantation | Renal replacement therapy (RRT) | |
| Dialysis | AKI stage 3D CKD G5D | AKI stage 3 treated by dialysis CKD G5 treated by dialysis | AKI-D, dialysis-dependent AKI ESKD, ESKF, ESRD, ESRF, dialysis-dependent CKD | |
| Duration | Long-term vs. short-term: long-term refers to dialysis for CKD, and may also be referred to as maintenance dialysis; short-term refers to dialysis for AKD | Chronic dialysis, acute dialysis (the terms acute and chronic refer to duration of kidney disease rather than duration of dialysis treatment) | ||
| Modality and frequency | Modalities • hemodialysis (HD) • hemofiltration (HF) • hemodiafiltration (HDF) • peritoneal dialysis (PD, ambulatory or automated) Frequency • continuous • intermittent (short or prolonged) |
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| Kidney transplantation Donor source | CKD G1T–G5T | CKD G1–G5 after transplantation Specify living donor kidney transplant/transplantation (LDKT) or deceased donor kidney transplant/transplantation (DDKT) | ESKD, ESKF, ESRD, ESRF | |
| Kidney failure with replacement therapy | KFRT | CKD G5 treated by dialysis or CKD G1–G5 after transplantation; for epidemiologic studies, both should be included | ESKD, ESKF, ESRD, ESRF | |
| Kidney failure without replacement therapy | CKD G5 without KRT | Further specification is preferred: specify whether KRT is not chosen vs. not available | ESKD, ESKF, ESRD, ESRF, untreated kidney failure | |
| With comprehensive conservative care | Further specification is preferred; definition is evolving | |||
| Without comprehensive conservative care | Further specification is preferred: specify whether comprehensive conservative care is not chosen vs. not available | |||
| Part 3. Acute Kidney Diseases and Disorders (AKD) and Acute Kidney Injury (AKI) | Disease duration ≤3 months; conceptually different from initial recognition of CKD | Acute renal failure (ARF); acute renal insufficiency (ARI) | ||
| Acute kidney diseases | AKDc | KDIGO definition: AKI, or GFR <60 ml/min per 1.73 m2, or markers of kidney damage for ≤3 months, or decrease in GFR by ≥35% or increase in SCr by >50% for ≤3 months | ARF, ARI | |
| Acute kidney injury | AKI | KDIGO definition (AKI is a subcategory of AKD): oliguria for >6 hours, rise in SCr by >0.3 mg/dL in 2 days or by >50% in 1 week | ARF, ARI | |
| AKI classification | KDIGO classification by cause and stage preferred rather than stage alone; e.g., a patient with AKI stage 3 due to ATN; classification applies to all AKI stages | Previous classifications, including RIFLE and AKIN (the KDIGO classification harmonized these prior definitions) | ||
| AKI stages | KDIGO definition (applicable only to people with AKI) | |||
| AKI stage 1 | Serum creatinine and/or urine output criteria | |||
| AKI stage 2 | Serum creatinine and/or urine output criteria | |||
| AKI stage 3 | Serum creatinine and/or urine output criteria | |||
| Part 4. Chronic Kidney Disease (CKD) | Disease duration >3 months | Chronic renal failure (CRF); ESRD; renal/kidney impairment, insufficiency, dysfunction | ||
| CKD | KDIGO definition: GFR <60 ml/min per 1.73 m2 or markers of kidney damage for >3 months | CRF; ESRD; renal/kidney impairment, insufficiency, dysfunction | ||
| CKD classification | KDIGO CGA classification by cause, GFR category (G1–G5), and albuminuria category (A1–A3); see below for definitions of G and A categories. For example, a patient with CKD G1, A3 due to diabetes, or a cohort with CKD G4–G5, A1–A3 of any cause. Note that CKD classification is only applicable to people with CKD, so a patient could not be classified as “CKD G2, A1” if there was no other evidence of kidney damage. | Mild, moderate, severe, early, advanced CKD; CKD stage 1–5 (complete description preferred rather than G category alone) | ||
| CKD without KRT | CKD without KRT | CKD G1–G5, A1–A3 of any cause, not receiving dialysis or transplantation | ND-CKD (non-dialysis CKD), NDD-CKD (non–dialysis-dependent CKD), predialysis CKD, pre-ESRD CKD | |
| CKD risk categories | KDIGO definitions (colors refer to heat map in Supplementary Figure S1) unless otherwise defined; risk depends on the outcome being considered | Mild, moderate, severe, early, advanced CKD | ||
| CKD risk category − low | Low risk | Refers to G1A1, G2A1 (green) | ||
| CKD risk category − | ||||
| moderately high | Moderate risk | Refers to G1A2, G2A2, G3aA1 (yellow) | ||
| CKD risk category − high | High risk | Refers to G1A3, G2A3, G3aA2, G3bA1 (orange) | ||
| CKD risk category − very high | Very high risk | Refers to G3aA3, G3bA2, G3bA3, G4A1, G4A2, G4A3, G5A1, G5A2, G5A3 (red) | ||
| CKD progression | Refers to worsening GFR or albuminuria. Other biomarkers not included. There is not yet consensus on use of specific terms to describe the timing (e.g., early, late) or rate (fast, slow) of progression. Use of specific terms should be defined in methods. | Further specification may be required: GFR decline may occur during therapy for other conditions, which may not be considered as CKD progression. | ||
| CKD remission | Refers to improving GFR or albuminuria. Criteria depend on disease. Use of specific terms should be defined in methods. | |||
| Part 5. Kidney Measures | Applies to people with or without kidney disease; consider measurement issues (methods) and variability (multiple measures may improve classification) | |||
| Glomerular filtration rate and clearance | Glomerular filtration rate | GFR | GFR and creatinine clearance are not synonymous Units must be specified (ml/min per 1.73 m2 or ml/min) | |
| Measured glomerular filtration rate | mGFR | Clearance methods and exogenous filtration markers should be noted separately in methods | ||
| Estimated glomerular filtration rate | eGFR | Estimating equations (e.g., CKD-EPI and MDRD Study) and filtration markers (e.g., creatinine and cystatin C) should be noted separately in methods | ||
| Estimated glomerular filtration rate; marker | eGFRcr | eGFR using creatinine | ||
| eGFRcys | eGFR using cystatin C | |||
| eGFRcr-cys | eGFR using creatinine and cystatin C | |||
| Clearance | Cl | Solute must be specified; units must be specified (ml/min per 1.73 m2 or ml/min) | ||
| Measured clearance | mCl | Clearance methods and markers should be noted separately in methods | ||
| Measured clearance; marker | mClUN | mCl using urea nitrogen | ||
| mClcr | mCl using creatinine | |||
| mClUN-cr | mCl using urea nitrogen and creatinine | |||
| Estimated clearance | eCl | Estimating equations (e.g., Cockcroft-Gault) and markers should be noted separately in methods | ||
| Estimated clearance; marker | eClcr | eCl using creatinine | ||
| GFR categories | For use in describing GFR level irrespective of the presence or absence of kidney disease; GFR units are ml/min per 1.73 m2 for these categories; multiple categories can be collapsed (e.g., G3–G5) | |||
| Normal to increased GFR | G1 | GFR ≥90 ml/min per 1.73 m2 | ||
| Mildly reduced GFR | G2 | GFR 60–89 ml/min per 1.73 m2 | ||
| Moderately reduced GFR | G3a | GFR 45–59 ml/min per 1.73 m2 | ||
| G3b | GFR 30–44 ml/min per 1.73 m2 | |||
| Severely reduced GFR | G4 | GFR 15–29 ml/min per 1.73 m2 | ||
| Kidney failure | G5 | GFR <15 ml/min per 1.73 m2 or treated by dialysis | ||
| Hyperfiltration | The concept of hyperfiltration is generally accepted but not consistently defined. If this term is used as an exposure, outcome, or covariate, the GFR threshold must be defined (e.g., >120 ml/min per 1.73 m2). | Renal hyperfiltration | ||
| GFR reserve | The concept of GFR reserve is generally accepted as the difference between stimulated and basal GFR | Renal function reserve | ||
| Albuminuria and proteinuria | Specify measurement conditions (spot vs. timed samples; quantitative vs. dipstick); differentiate non-albumin proteins as clinically indicated | |||
| Albuminuria | Microalbuminuria, macroalbuminuria | |||
| Urinary albumin concentration Urinary albumin excretion rate | AER | Requires timed urine collection; interval for urine collection should be noted separately in methods; unit of time may vary (hour or day) | ||
| Urinary albumin-creatinine ratio | ACR | From timed urine collection or spot urine collection; interval for timed urine collection, or time of day for spot urine collection, should be noted separately in methods | ||
| Proteinuria | Clinical proteinuria, overt proteinuria | |||
| Urinary protein concentration Urinary protein excretion rate | PER | Requires timed urine collection; interval for urine collection should be noted separately in methods; unit of time may vary (hour or day) | ||
| Urinary protein-creatinine ratio | PCR | From timed urine collection or spot urine collection; interval for timed urine collection, or time of day for spot urine collection, should be noted separately in methods | ||
| Albuminuria and proteinuria categories | For use in describing albuminuria or proteinuria level irrespective of the presence or absence of kidney disease | |||
| Normal | AER <10 mg/d; ACR <10 mg/g (<1 mg/mmol) | Normoalbuminuria | ||
| Mildly increased (mild) | AER 10–29 mg/d; ACR 10–29 mg/g (1.0–2.9 mg/mmol) | |||
| Normal to mildly increased (normal to mild) | A1 | AER <30 mg/d; ACR <30 mg/g (<3 mg/mmol) | ||
| PER <150 mg/d; PCR <150 mg/g (<15 mg/mmol) | ||||
| Moderately increased (moderate) | A2 | AER 30–300 mg/d; ACR 30–300 mg/g (3–30 mg/mmol) PER 150–500 mg/d; PCR 150–500 mg/g (15–50 mg/mmol) | Microalbuminuria | |
| Severely increased (severe) | A3 | AER >300 mg/d; ACR >300 mg/g (>30 mg/mmol) | Macroalbuminuria, clinical | |
| PER >500 mg/d; PCR >500 mg/g (>50 mg/mmol) | proteinuria, overt proteinuria | |||
| Nephrotic-range/syndromed | AER >2200 mg/d; ACR >2200 mg/g (>220 mg/mmol) PER >3500 mg/d; PCR >3500 mg/g (>350 mg/mmol) Specify with or without nephrotic syndrome, as noted by the presence of hypoalbuminemia (with edema and hyperlipidemia in most cases) | |||
| Tubular function | ||||
| Tubular secretion | TS | Further specification is required to distinguish rate, clearance, or fraction (compared to filtered load) | ||
| Tubular reabsorption | TR | Further specification is required to distinguish rate, clearance, or fraction (compared to filtered load) | ||
| Fractional excretion, marker | FENa | FE of sodium | ||
| Fractional reabsorption, marker | FRNa | FR of sodium | ||
ACR, albumin-creatinine ratio; AER, albumin excretion rate; AKD, acute kidney diseases and disorders; AKI, acute kidney injury; AKIN, Acute Kidney Injury Network; ARF, acute renal failure; ARI, acute renal insufficiency; ATN, acute tubular necrosis; CGA, cause, GFR category, and albuminuria category; CKD, chronic kidney disease; CKD-EPI, CKD Epidemiology Collaboration; DDKT, deceased donor kidney transplant/transplantation; eGFR, estimated glomerular filtration rate; ESKD, end-stage kidney disease; ESKF, end-stage kidney failure; ESRD, end-stage renal disease; ESRF, end-stage renal failure; FENa, fractional excretion, sodium; FRNa, fractional reabsorption, sodium; GFR, glomerular filtration rate; HD, hemodialysis; HDF, hemodiafiltration; HF, hemofiltration; KDIGO, Kidney Disease: Improving Global Outcomes; KFRT, kidney failure with replacement therapy; KRT, kidney replacement therapy; LDKT, living donor kidney transplant/transplantation; MDRD, Modification of Diet in Renal Disease; mGFR, measured GFR; ND-CKD, non-dialysis CKD; NDD-CKD, non–dialysis-dependent CKD; PCR, protein-creatinine ratio; PD, peritoneal dialysis; PER, protein excretion rate; pre-ESRD, pre–end-stage renal disease; RF, renal failure; RIFLE, Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease; RRT, renal replacement therapy; SCr, serum creatinine; TR, tubular reabsorption; TS, tubular secretion.
a
Journal style will dictate whether and when to abbreviate terms.
b
Ongoing discussion; may be revised by KDIGO AKI guideline update.
c
Ongoing discussion; may be revised by KDIGO AKD consensus conference.
d
Ongoing discussion; may be revised by KDIGO Glomerulonephritis guideline update.