Hosted by Ray Shields, MD

 In the past, the absence of a widely accepted definition of chronic kidney disease (CKD) and the lack of classification of the stages of CKD impaired our ability to communicate with each other.  This also  impaired our efforts to diagnose and treat persons with kidney disease early in the course of their illness.   In response to these problems, the National Kidney Foundation established Clinical Practice Guideline for Chronic Kidney Disease: Evaluation, Classification, and Stratification, which provides a common language for communication among providers, patients and their families.  The IHS DDTP fully supports the application of these principles to people with diabetes.

Terminology

·  Use the term “kidney” instead of “renal.”

·  The term "chronic kidney disease" (CKD) replaces “end stage renal disease,” “pre-dialysis,” or “chronic renal failure.”  ICD-9 codes are now available for these terms and precision can be used with these terms:

585.1    Chronic kidney disease, Stage I

585.2    Chronic kidney disease, Stage II (mild)

585.3    Chronic kidney disease, Stage III (moderate)

585.4    Chronic kidney disease, Stage IV (severe)

585.5    Chronic kidney disease, Stage V (end stage kidney disease)

585.9    Chronic kidney disease, unspecified

Tests Used To Assess Kidney Disease

Screening includes an assessment of glomerular filtration rate (GFR) and measurement of urinary protein excretion.  These tests should be done at diagnosis, and repeated at least annually.  Providers can use these tests to monitor the progression of kidney disease and the effects of therapy.  As such, these tests are continued for the life of the patient regardless of stage of kidney disease or types of treatments provided.  

Assessment of GFR

The kidney is usually described as “a filter” and GFR is a measure of the kidneys’ ability to filter blood, which can be expressed on a continuous scale. Serum creatinine alone does not provide enough information for diagnosis and classification. GFR can be estimated by using the serum creatinine, body weight, and age.   Formulas to calculate GFR include the MDRD (Modification of Diet in Renal Disease Study Group) and Cockcroft-Gault equations.  The RPMS laboratory package with patch 16 will calculate the GFR automatically when you order a serum creatinine test.  You may also use on-line calculators such as the National Kidney Foundation's MDRD GFR calculator.

Measurement of Urinary Protein Excretion

In the past, our ability to measure protein in the urine was limited to semi-quantitative dipstick tests.  Although sensitive dipstick tests were developed that could detect very small amounts of protein (i.e., microalbuminuria), the old, complicated terminologies persisted and were often confusing.  Because urinary protein excretion is a continuous variable, it is better to use a quantitative measurement and to describe the rate of excretion of urinary protein.  We recommend use of the urinary albumin to creatinine ratio (UACR), which can be estimated from a simple spot urine specimen. The UACR is roughly equivalent to the 24-hour protein excretion in grams.  24-hour urine testing is not recommended for routine diabetes nephropathy screening.  We recommend reporting the actual UACR in terms of milligrams of albumin per gram of creatinine.  If you or your colleagues, laboratory, or specialists choose a different test, you should review those test characteristics, expected values, and associated costs.

Because of variability in urinary albumin excretion, at least two specimens, preferably first morning void, collected within a 3 to 6 month period should be abnormal before considering a patient to have crossed one of the diagnostic thresholds.  Exercise within 24 hours, infection, fever, congestive heart failure, marked hyperglycemia, pregnancy, marked hypertension, urinary tract infection, and hematuria may elevate urinary albumin over baseline values.

The IHS Kidney Disease Program suggests that people with 1+ or greater protein on dipstick or UACR >300 mg/g can have their protein excretion ascertained with a urine protein-to-creatinine ratio instead of UACR.

Diagnosis of CKD

CKD is kidney damage for 3 months as defined by structural or functional abnormalities with or without decreased glomerular filtration rate (GFR), or a GFR of 60 mL/min/1.73 m² or less, with or without kidney damage.  So, if there is a UACR of 30 mg/g or greater, or if the GFR is less than 60 for more than 3 months, then CKD is present.

Further Evaluation and Treatment of CKD

In adults with diabetes, the most likely cause of CKD is the diabetes itself.  However, there are other treatable causes of CKD.  Evaluation is appropriate.  If you need assistance in evaluating for other causes of CKD, consultation may be appropriate.  

Once CKD and its cause is established, there are important treatments that can delay progression and improve quality of life.  Of critical importance is the aggressive treatment of blood pressure.  Lower targets for systolic and diastolic blood pressure may be appropriate.  Certain blood pressure medications, such as ACE inhibitors or ARBs, may play an important role.  Treatment of anemia and metabolic bone disease becomes important in people with GFR < 60.