Issue Seventy August standards of C.A.R.E. CLINICAL CASE MANAGEMENT NEWSLETTER. The Calgary Animal Referral & Emergency Centre Animal Hospital

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1 standards of CLINICAL CASE MANAGEMENT NEWSLETTER The Calgary Animal Referral & Emergency Centre Animal Hospital

2 Staging of Chronic Kidney Disease Lisa Shearer BSc., DVM, DACVIM (SAIM), DVSc. The International Renal Interest Society (IRIS) was formed with the goal of developing a system to stage dogs and cats with chronic kidney disease (CKD). The goal of this staging system is to allow for a more objective means of communication between veterinary professionals regarding CKD and to establish guidelines for diagnosis, prognosis and treatment that can be applied by the individual practitioner. The current IRIS staging system will evolve over time and the most up to date version will be available on the IRIS website ( com). Staging of CKD is based on the patient s level of kidney function. While the accepted best overall measure of kidney function is measuring GFR, measurement of creatinine concentration is the most commonly and readily applied surrogate for GFR. Creatinine concentration is used as the primary criteria for staging CKD with the IRIS system. It is imperative that the IRIS staging system be applied only to dogs and cats with stable CKD that are well hydrated, fasted and several measurement should be obtained over a period of several weeks. If renal azotemia is confirmed, then attempts should be made to classify the kidney disease as either acute, decompensated chronic or chronic, as the IRIS staging system can only be applied to true chronic kidney disease. However, it is possible that both acute and decompensated chronic could stabilize over a 1-2 month period at which time the staging system could be applied. Applying the staging system Stage Dogs Serum Creatinine (umol/l) 1 <125 < >440 >440 Cats Serum Creatinine (umol/l) Stage 1: Non-azotemic This stage of CKD includes patients that are non-azotemic; however, other indices of inadequate renal function are present. Examples of these would include inadequate urine concentrating ability without an identifiable non-renal etiology, persistent proteinuria of renal origin, abnormal renal imaging, abnormal renal palpation, abnormal renal biopsy or progressively increasing creatinine concentration within the reference interval. These patients often display no clinical symptoms of renal dysfunction with the exception of polyuria and polydipsia. p.1

3 Stage 2: Mild azotemia Patients in this category often display no or just mild clinical signs of renal dysfunction again with the exception of polyuria and polydipsia; however, some cats may demonstrate weight loss or decreased appetite. It should be noted that the lower end of this creatinine range might lie within the reference range depending on the laboratory. Given the insensitivity of creatinine concentration as a surrogate for GFR, those patients at the upper end of the reference range may have excretory failure. **Dogs and cats in stage 1 and 2, may display clinical signs secondary to proteinuira and hypertension if present. Additionally, these dogs and cats may also display clinical symptoms directly related to their underlying renal pathology such as pyelonephritis or nephrolithiasis. The renal disease in patients with stage 1 and 2 CKD who are non-hypertensive and nonproteinuric is often stable or only very slowly progressive over an extended period.** Stage 3: Moderate azotemia Dogs and cats will display clinical signs and other hematologic/biochemical deranagements related to their renal injury including decreased appetite, weight loss, dehydration, constipation, hyperphosphtaemia, metabolic acidosis, hypokalemia and anemia. However, with appropriate intervention, these patients often do not display clinical symptoms of uremia. Renal disease of this stage is progressive in nature. At this stage, there may be clinical advantages to targeting therapy at modifying factors that promote CKD, in addition to identifying and treating primary CKD. Stage 4: Marked azotemia Clincial signs of uremia are typically present at this stage. As a result, diagnostic approach and therapeutic interventions are the same as for Stage 3 but also include treatments intended to address the symptoms of uremia. Substages of the IRIS System Substaging of CKD is based on the presence or absence of proteinuria and hypertension as these factors can affect prognosis and are factors that may be influenced by therapeutic intervention. Additionally, presence and severity of proteinuria and hypertension should be regularly monitored as these can worsen with renal disease progression. Proteinuria Unless marked proteinuria is documented, persistence of proteinuria should be documented through repeated UPC ratios performed 2-3 times ideally 2 weeks apart. Patients with borderline proteinuria should be re-evaluated in 2 months to evaluate for any progression. As renal deterioration progresses, proteinuria may decline and therefore may be less common in stages 3 or 4. p.2

4 Classification Dog Urine protein:creatinine ratio (UPC) Cat Urine protein:creatinine ratio (UPC) Proteinuric (P) Borderline proteinuric (BP) Nonproteinuric (NP) >0.5 > <0.2 <0.2 Hypertension Substaging patients with CKD by blood pressure is based on degree of risk for end organ damage (eyes, nervous system, kidneys or heart) and whether there is evidence of endorgan damage or complications. For determination of blood pressure, ideally, patients should be acclimatized to the procedure and multiple measurements obtained (preferably on separate multiple visits to the clinic). Arterial Pressure Substage Systolic BP (mmhg) Diastolic BP (mmhg) 0 - Minimal Risk <150 < Low Risk Moderate Risk Severe Risk > or = 180 > or = 120 No complications (nc) No evidence of end organ damage/ complications Complications (c) Evidence of end organ damage/ complications Risk not determined (RND) Blood pressure not measured Effect of Therapy In patients where treatment of proteinuria and/or hypertension is initiated, repeat substaging is recommended and is based on the current UPC and blood pressure. (T) is used to denote that this represents the effect of therapy. Example: Before treatment: Dog with creatinine of 300umol/L, UPC 0.4, systolic blood pressure 195mmHg and retinal changes IRIS stage 3, BP, AP3c p.3

5 Following treatment: Creatinine 300umol/L, UPC 0.4, systolic blood pressure 160mmHg, retinal changes IRIS stage 3, BP, AP2c (T) p.4