General practitioners have a key role in detecting and monitoring kidney health and, together with specialists, in risk reduction. We encourage awareness, regular reviews and monitoring of patients at risk so that CKD can be detected at an early stage thus allowing appropriate treatments to be instigated. Consequently, the progression of established kidney disease can be slowed or even halted and the risk of associated complications reduced.
The International Society of Nephrology (ISN) and KDIGO (Kidney Disease: Improving Global Outcomes) have released the useful Early Identification and Intervention Toolkit aimed at health care professionals (doctors and nurses) working in primary care settings.
It is important to consider the personal risk factors of each patient to assess their kidney health: diabetes mellitus, hypertension, cardiovascular disease, overweight, family history of kidney disease or higher age. According to the IDF Diabetes Atlas (International Diabetes Federation), 1 in 2 adults with diabetes are not diagnosed.
To assess the patients’ risk for kidney damage, the medication history, dietary behaviour, supplements and herbal remedies should be reviewed as well. The frequent or constant use of specific drugs, such as over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) may cause kidney damage in the long term.
An easy to perform and cheap kidney work-up, the so-called kidney test or a kidney check-up consists of two components:
Serum creatinine is the marker to measure kidney function. In kidney disease, due to the decrease of renal filter capacity, waste products as creatinine and urea accumulate in the blood. Higher levels of these metabolic end products denote poor levels of kidney function. Since creatinine is formed in the muscles, the amount of creatinine in the blood depends on muscle mass and muscle work. The normal value is 0.8 – 1.2 mg/dl or 70 – 106 µmol/l.
The glomerular filtration rate (GFR) can be estimated from serum creatinine using an equation. Similarly, it represents an additional value to assess kidney function and the severity of the disease. Glomerular filtration is the volume filtered by the glomeruli of the kidneys in a given time. The normal value is 90 to 130 millilitres per minute. Thus, a healthy kidney filters at least 90 millilitres of primary urine from the blood per minute. The GFR is commonly used in everyday clinical practice and the equation takes age and gender into account.
These lab values allow an easy assessment of kidney function.
In addition to blood values, urine values are also important for examining kidney function and damage. If the filtering capacity of the glomeruli is impaired, protein may no longer be retained in the body and passes increasingly into the urine (proteinuria). One component of the proteins is albumin.
To assess kidney damage, the concentration of albumin in the urine should be checked. In a healthy person, it is less than 30 milligrams per day. A rapid urine test – urinalysis or urine dipstick testing – for high albuminuria (30-300 milligrams of albumin) can provide a first indication of kidney damage. However, the albumin concentration in the urine depends on fluid uptake. To increase the accuracy of the test, the albumin concentration should therefore be related to the concentration of creatinine in the urine in a laboratory test (albumin/creatinine ratio). Individuals with diabetes, in particular, should be tested regularly for albumin in the urine to assess kidney damage.