Editing Assessment of kidney function (section)

==Kidney function in disease==
A decreased renal function can be caused by many types of [[kidney disease]]. Upon presentation of decreased renal function, it is recommended to perform a [[medical history|history]] and [[physical examination]], as well as performing a [[renal ultrasound]] and a [[urinalysis]].{{citation needed|date=September 2019}} The most relevant items in the history are [[pharmaceutical drug|medications]], [[edema]], [[nocturia]], gross [[hematuria]], [[Family history (medicine)|family history]] of kidney disease, [[diabetes]] and [[polyuria]]. The most important items in a physical examination are signs of [[vasculitis]], [[lupus erythematosus]], [[diabetes]], [[endocarditis]] and [[hypertension]].{{citation needed|date=September 2019}}

A urinalysis is helpful even when not showing any pathology, as this finding suggests an extrarenal etiology. [[Proteinuria]] and/or [[urinary sediment]] usually indicates the presence of [[glomerular disease]]. [[Hematuria]] may be caused by glomerular disease or by a disease along the [[urinary tract]].{{citation needed|date=September 2019}}

The most relevant assessments in a [[renal ultrasound]] are renal sizes, [[echogenicity]] and any signs of [[hydronephrosis]]. Renal enlargement usually indicates diabetic nephropathy, [[focal segmental glomerular sclerosis]] or [[myeloma]]. Renal atrophy suggests longstanding chronic renal disease.{{citation needed|date=September 2019}}

===Chronic kidney disease stages===
{{main|Chronic kidney disease}}
Risk factors for kidney disease include diabetes, high blood pressure, family history, older age, ethnic group and smoking.
For most patients, a GFR over 60 (mL/min)/(1.73 m<sup>2</sup>) is adequate. But significant decline of the GFR from a previous test result can be an early indicator of kidney disease requiring medical intervention. The sooner kidney dysfunction is diagnosed and treated the greater odds of preserving remaining nephrons, and preventing the need for dialysis.

{| class="wikitable" style="float:right; margin-left:5px"
|-
!CKD stage
!GFR level <small>((mL/min)/(1.73 m<sup>2</sup>))</small>
|-
|Stage 1
|style="text-align:center"|≥ 90
|-
|Stage 2
|style="text-align:center"|60–89
|-
|Stage 3
|style="text-align:center"|30–59
|-
|Stage 4
|style="text-align:center"|15–29
|-
|Stage 5
|style="text-align:center"|< 15
|}
The [[chronic kidney disease#Stages|severity of chronic kidney disease]] (CKD) is described by six stages; the most severe three are defined by the MDRD-eGFR value, and first three also depend on whether there is other evidence of kidney disease (e.g., [[proteinuria]]):
:0) Normal kidney function – GFR above 90 (mL/min)/(1.73 m<sup>2</sup>) and no [[proteinuria]]
:1) CKD1 – GFR above 90 (mL/min)/(1.73 m<sup>2</sup>) with evidence of kidney damage
:2) CKD2  (mild) – GFR of 60 to 89 (mL/min)/(1.73 m<sup>2</sup>) with evidence of kidney damage
:3) CKD3 (moderate)  – GFR of 30 to 59 (mL/min)/(1.73 m<sup>2</sup>)
:4) CKD4 (severe) – GFR of 15 to 29 (mL/min)/(1.73 m<sup>2</sup>)
:5) CKD5 kidney failure – GFR less than 15 (mL/min)/(1.73 m<sup>2</sup>)  Some people add CKD5D for those stage 5 patients requiring dialysis; many patients in CKD5 are not yet on dialysis.

Note: others add a "T" to patients who have had a transplant regardless of stage.

Not all clinicians agree with the above classification, suggesting that it may mislabel patients with mildly reduced kidney function, especially the elderly, as having a disease.<ref>{{cite journal |vauthors=Bauer C, Melamed ML, Hostetter TH |year= 2008 |title= Staging of Chronic Kidney Disease: Time for a Course Correction  |journal=  Journal of the American Society of Nephrology |volume= 19 |pages= 844–846 |doi= 10.1681/ASN.2008010110  |pmid= 18385419 |url= http://jasn.asnjournals.org/content/19/5/844.full |issue=5|doi-access= free }}</ref><ref>{{cite journal |vauthors=Eckardt KU, Berns JS, Rocco MV, Kasiske BL |url=http://www.kdigo.org/meetings_events/pdf/KDOQI-KDIGO_Editorial_on_CKD_Classification.pdf |journal=American Journal of Kidney Diseases |volume=53 |issue=6 |pages=915–920 |date=June 2009 |title=Definition and Classification of CKD: The Debate Should Be About Patient Prognosis – A Position Statement From KDOQI and KDIGO |doi=10.1053/j.ajkd.2009.04.001 |pmid=19406541 |url-status=dead |archiveurl=https://web.archive.org/web/20110725131557/http://www.kdigo.org/meetings_events/pdf/KDOQI-KDIGO_Editorial_on_CKD_Classification.pdf |archivedate=2011-07-25 }}</ref> A conference was held in 2009 regarding these controversies by Kidney Disease: Improving Global Outcomes (KDIGO) on CKD: Definition, Classification and Prognosis, gathering data on CKD prognosis to refine the definition and staging of CKD.<ref>{{cite web |year=2009 |url=http://www.kdigo.org/meetings_events/CKD_Controversies_Conference.php |publisher=Kidney Disease: Improving Global Outcomes (KDIGO) |title=KDIGO Controversies Conference: Definition, Classification and Prognosis in CKD, London, October 2009 |url-status=dead |archiveurl=https://web.archive.org/web/20101124202928/http://www.kdigo.org/meetings_events/CKD_Controversies_Conference.php |archivedate=2010-11-24 }}</ref>