Diagnosis overview
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As clinical signs are often not visible until late stages of the disease, it is recommended to routinely screen patients that are at risk of developing chronic kidney disease (CKD), for example geriatric patients or those with other conditions that predispose them to CKD. For screening purposes only a few simple tests are normally carried out:
This may be followed up with:
A thorough physical examination of all body systems is performed, including:
Assessment of the kidneys
- Renal palpation may reveal small irregular or enlarged kidneys
Assessment of general condition
- Bodyweight and condition
- Hydration status
Other signs associated with CKD
- Mouth ulcers
- Pale mucous membranes (anaemia)
- Signs associated with hypertension (retinal haemorrhage, retinal detachment)
As many patients suffering from CKD are also likely to have systemic hypertension, it is important to measure blood pressure regularly in these patients. Hypertension causes progression of kidney disease and will eventually lead to other end-organ damage. Blood pressure can be measured using a Doppler or oscillometric blood pressure monitor. Both methods measure the strength of blood flow through a peripheral artery, for example, in the leg or tail. Doppler is most commonly used as it is considered more accurate for small animals. It is quick, non-invasive, cheap and can easily be done in the consulting room. See diagnosis for further information on measuring blood pressure.
A complete urinalysis should be performed on every animal that is suspected of having renal disease. This is also a useful screening test as it is quick, easy and cheap to carry out.
The three main purposes of urinalysis are:
- To measure the concentration of urine (specific gravity). As kidney function deteriorates, the kidney loses its ability to concentrate urine.
- To measure the amount of protein in the urine (proteinuria). As the kidney starts to fail, the deteriorating glomerular membrane allows more protein to leak through into the plasma filtrate.
- To examine the urine under the microscope to look for the presence of bacteria or abnormal cells (sediment), which suggests lower urinary tract disease such as an infection, inflammation or a tumour.
See diagnosis for further information on urinalysis.
The main changes in blood tests are elevated urea and creatinine (called azotaemia). These changes are only detectable once there is a significant loss of kidney function. If azotaemia is detected, urinalysis (specific gravity) must be carried out at the same time to differentiate between prerenal (dehydration) and renal azotaemia. See diagnosis for further information on renal blood tests.
Radiographs and ultrasound can be used to assess the structure of the kidneys, but cannot assess kidney function and, hence, are a less useful diagnostic tool, unless a disease such as a tumour or PKD is suspected.
Staging of CKD
Once a diagnosis of CKD has been reached, patients are staged to indicate the severity of their disease and identify appropriate management. The staging system has been developed by IRIS (International Renal Interest Society), which is an independent group of nephrologists supported by Novartis Animal Health. Staging is done initially based on fasting blood creatinine levels, assessed on at least two occasions, in the stable patient. The patient is then substaged based on proteinuria and blood pressure. Click here to see the IRIS staging guidelines.