21 Mar 2016
Samantha Taylor, in the second of this two-part article, discusses management options relating to complications of CKD, including proteinuria and urinary tract infections.
Samantha Taylor
Job Title
Figure 2. In-clinic examination of urine sediment used in the place of bacterial urine cultures for cats with chronic kidney disease.
As discussed in part one (VT46.09), chronic kidney disease (CKD) is a common diagnosis in cats seen in first opinion practice, with early diagnosis and maximising compliance to feeding a prescription diet important. This article discusses what else can be used to treat cats.
The International Society of Feline Medicine has produced guidelines on the management of CKD, published in the Journal of Feline Medicine and Surgery (Sparkes et al, 2016).
A diagnosis of CKD is never an end point; it is just the start. As clinicians, we now need to consider what consequences of CKD have occurred, and what to look for now and monitor for in the future.
Table 1 summarises some of these complications, including how to detect and manage them, with proteinuria, urinary tract infection (UTI; Panel 1), nausea and inappetence discussed in this article.
Angiotensin converting enzyme inhibitors (ACEis) and angiotensin receptor blockers (ARBs) are used in the management of CKD in cats, both blocking the potentially negative effects of the renin-angiotensin-aldosterone system (RAAS) on the kidney and reducing proteinuria. However, it is not always clear which cases will benefit from this treatment.
In cats, proteinuria is associated with a poorer prognosis, with protein loss into renal tubules promoting tubular inflammation and fibrosis (Ruggenenti et al, 2012).
Proteinuria is associated with a shorter lifespan in cats with CKD. In one study (Syme et al, 2006), cats with a urine protein creatinine ratio (UPC) of less than 0.2 had a median survival of around 1,000 days, dropping to 500 days for a UPC of 0.2 to 0.4 and for the proteinuric group (UPC of more than 0.4) to around 400 days.
However, according to International Renal Interest Society (IRIS) classification, the majority of cats with CKD are non-proteinuric and, importantly, treatment with an ACEi has not been shown to improve survival.
IRIS classifications of proteinuria rate them as:
Figure 1 shows an algorithm to illustrate decision-making in cats with CKD and shows cases will benefit from RAAS inhibition. IRIS recommendations include treatment of cats with a UPC of more than 0.4.
The treatment of cats with borderline proteinuria (UPC between 0.2 and 0.4) is more controversial and the author treats each cat on a case by case basis, prioritising compliance to diet and management of complications, but considering the poorer prognosis shown for cats with a UPC consistently above 0.2.
Adverse effects are possible, so only use in stable patients with normal hydration and monitor for worsening azotaemia and hypotension five to seven days after starting treatment. Increases in creatinine of more than 15% should prompt further evaluation and consideration to reduction or cessation of treatment. Adverse affects are of increasing concern in higher stage cats with CKD.
The circulation of uraemic toxins can result in nausea, vomiting and inappetence in cats with CKD. Inadequate nutritional intake is a concern and they are less likely to accept a renal diet if they are nauseous.
A study by Markovich at al (2015) showed nearly half of cats with CKD had an abnormal appetite, and a reduced calorie intake will result in lean muscle breakdown, weakness and other adverse effects; for example, reduced immune function and slowed recovery from illness. Owners should be encouraged to monitor food intake carefully and, along with regular re-evaluation and weight checks, vets should be able to identify and treat affected cats.
Various medications can be considered for the management of nausea and inappetence. Treatment with maropitant (orally for two weeks) has been shown to reduce vomiting in cats with CKD (Quimby et al, 2015), although, in that study, treated cats did not gain weight or eat more.
Another study by the same authors (Quimby et al, 2013) showed treatment of cats with stage-two CKD with mirtazapine reduced vomiting and increased bodyweight and appetite. The author favours this drug both to aid acceptance of a renal diet and to improve appetite in cats with CKD. Other treatment options include famotidine, omeprazole, ondansetron and dolasetron.
For cats with higher stage CKD, placement of a feeding tube is recommended by some clinicians to allow fluid, food and medications to be administered. This will depend on the individual case and the clients.
Bacterial urinary tract infections (UTIs) are uncommon in healthy young cats, but up to 30% of cats with CKD may be affected, and the majority show no clinical signs (White et al, 2012). These clinically silent UTIs may result in ascending pyelonephritis and progression of CKD, but this is unproven and no effect of treatment of clinically silent UTIs on survival has been demonstrated.
However, these alarming statistics mean we should look for UTIs in all cats with CKD and, ideally, perform bacterial urine cultures every three to six months. If this is not financially possible, at least an in-clinic examination of urine sediment is indicated (Figure 2) and samples with active sediments should be submitted for culture. However, some cats with UTI and CKD will have inactive sediment.
Escherichia coli makes up the majority of the bacterial isolates involved and sensitivity testing guides antibiotic choice. If empirical therapy is used then amoxicillin or potentiated amoxicillin for two to four weeks is appropriate, with repeat sediment exam/culture seven days after cessation of treatment.
Where clients have financial limitations, consider how to include in-clinic sediment examinations and empirical treatment, if indicated in your monitoring protocol for cats with CKD.
The diagnosis of CKD should not be seen negatively, but as an opportunity to improve the lifespan and quality of life of affected cats. Consider the potential complications and how you can look for them routinely in your clinic.
Prioritise the management of proteinuria and hyperphosphataemia, factors we know influence survival, but don’t neglect the management of nausea to maximise food intake or miss the undiagnosed UTI. You can make a real difference to the quality – and, potentially, quantity – of life for older cats.
