Diagnosing, Staging,  
   and Treating Chronic Kidney 
   Disease in Dogs and Cats
   Chronic kidney disease (CKD) is diagnosed based 
   on evaluation of all available clinical and diagnostic 
   information in a stable patient. Following diagnosis 
   of CKD, the IRIS Board recommends using serum 
   creatinine or SDMA (ideally both) to stage CKD with 
   substaging based on assessment of arterial blood 
   pressure and proteinuria.
        Step 1: Diagnose CKD
        Clinical signs and physical                                          Clinical presentation                                                                         Physical examination findings
        examination findings worsen  Consider age, sex, breed predispositions, and relevant                                                                                Can be normal in early stage CKD.  Findings 
        with increasing severity of                                          historical information, including medication history,                                         may include palpable kidney abnormalities, 
                                                                             toxin/toxicant exposure, and diet.                                                            evidence of weight loss, dehydration, 
        kidney disease                                                       Can be subclinical in early stage CKD. Signs may include                                      pale mucous membranes, uremic ulcers, 
                                                                             polyuria, polydipsia, weight loss, decreased appetite,                                        evidence of hypertension, i.e., retinal 
                                                                             lethargy, dehydration, vomiting, and bad breath.                                              hemorrhages/detachment.
           To diagnose Stage 1 and early Stage 2 CKD                                                                   OR To diagnose more advanced CKD (late Stage 2–4)
           One or more of these diagnostic findings:                                                                                                                   Both of these diagnostic findings:
        1         Creatinine                                             SDMA                                                       Increased creatinine and SDMA concentrations                                                                1
                                                     Creatinine                                                SDMA                 Creatinine
                                          increasing within the                                  increasing within the 
                  reference intervalreference interval where no          reference intervalreference interval where no              SDMA
                                    prerenal cause is apparent                             prerenal cause is apparent
                        Jun ’11           Jun ’12            Jun ’13        June        July        Aug        Sept                                                     Results of both tests should be interpreted 
                                                                                                                                                                                  in light of patient’s hydration status.
               Persistent increased SDMA* >14 µg/dL
        2                                                                                                                          plus
        3 Abnormal kidney imaging
                                                                                                                                                       Urine                                         Urine   
                                                                                                                                             specific gravity                              specific gravity                                     2
                                                                                                                                                                                                                  †
                                                                                                                                                    <1.030                                        <1.035
        4        Persistent renal proteinuria 
                 UPC >0.5 in dogs; UPC >0.4 in cats
                    0.6                       0.7                       1.0                                                           1.030 Canine                                                                           1.008
                   Sept ’15                  Oct ’15                   Nov ’15
                  Urine protein to creatinine (UPC) ratio                                                                             1.035 Feline                                                                           1.008
                                                                                                                                                         † 
                                                                 See www.iris-kidney.com for more detailed staging,                                       Note that some cats can produce hypersthenuric 
                                                                 therapeutic, and management guidelines.                                                  urine in the face of renal azotemia.
       Step 2: Stage CKD
                                                             Stage 1                                     Stage 2                                     Stage 3                                     Stage 4
                                                             No azotemia                                Mild azotemia                          Moderate azotemia                              Severe azotemia
                                                           (Normal creatinine)                          (Normal or mildly  
                                                                                                      elevated creatinine)
       Creatinine in mg/dL                                        Less than                               1.4–2.8                                     2.9–5.0                                       Greater than 
                                                                     1.4                                               µ                                           µ                                     5.0  
       Stage                         Canine                     (125 µmol/L)                            (125–250  mol/L)                            (251–440  mol/L)                                (440 µmol/L)
       based on  
       stable creatinine                                          Less than                               1.6–2.8                                     2.9–5.0                                       Greater than  
                                       Feline                        1.6                                               µ                                           µ                                     5.0 
                                                                (140 µmol/L)                            (140–250  mol/L)                            (251–440  mol/L)                                (440 µmol/L)
       SDMA* in µg/dL                                             Less than                                 18–35                                       36–54                                       Greater than 
       Stage                         Canine                           18                                                                                                                                  54
       based on                                                   Less than                                                                                                                         Greater than 
       stable SDMA                     Feline                         18                                    18–25                                       26–38                                             38
       UPC ratio
       Substage                      Canine                           Nonproteinuric <0.2   Borderline proteinuric 0.2–0.5   Proteinuric >0.5
       based on                        Feline                         Nonproteinuric <0.2   Borderline proteinuric 0.2–0.4   Proteinuric >0.4
       proteinuria
       Systolic blood 
       pressure in mm Hg                                                                    Normotensive <140   Prehypertensive 140–159    
       Substage based on                                                                                                                                                             _
                                                                                        Hypertensive 160–179   Severely hypertensive >180
       blood pressure
        Note:  In the case of staging discrepancy between creatinine                                                                       ®
                                                                                                        *SDMA = IDEXX SDMA  Test                                   See www.iris-kidney.com for more 
       and SDMA, consider patient muscle mass and retesting                                                                                                        detailed staging, therapeutic, and 
       both in 2–4 weeks. If values are persistently discordant,                                                                                                   management guidelines.
       consider assigning the patient to the higher stage.
     Step 3: Treat CKD
                                        Stage 1                     Stage 2                      Stage 3                      Stage 4
      Treatment                    Use nephrotoxic drugs        Same as Stage 1              Same as Stage 2             Same as Stage 3
      recommendations              with caution                 Renal therapeutic diet       Keep phosphorus             Keep phosphorus  
                                   Correct prerenal and         Treat hypokalemia in cats    <5.0 mg/dL                  <6.0 mg/dL 
                                    postrenal  abnormalities                                 (<1.6 mmol/L)               (<1.9 mmol/L)
                                   Fresh water available at                                  Treat metabolic acidosis    Consider feeding tube for 
                                   all times                                                 Consider treatment          nutritional and hydration 
                                   Monitor trends in creatinine                              of anemia                   support and ease of 
                                   and SDMA to document                                                                  medicating
                                   stability or progression                                  Treat vomiting, 
                                                                                             inappetence, and nausea
                                   Investigate for and treat                                 Increased enteral or 
                                   underlying disease and/or                                 subcutaneous fluids may 
                                   complications                                             be required to maintain 
                                   Treat hypertension if systolic                            hydration
                                   blood pressure persistently                               Consider calcitriol therapy 
                                   >160 or evidence of                                       in dogs
                                   end-organ damage
                                   Treat persistent proteinuria 
                                   with renal therapeutic diet 
                                   and medication  
                                   (UPC >0.5 in dogs;  
                                   UPC >0.4 in cats)
                                   Keep phosphorus  
                                   <4.6 mg/dL (<1.5 mmol/L) 
                                   If required, use renal 
                                   therapeutic diet   
                                   plus phosphate binder
                                  See www.iris-kidney.com for more detailed staging, therapeutic, and management guidelines.