Progressive anaemia is common in CRF and appears to contribute to a variety of clinical signs including lethargy, inappetence, weakness and weight loss. Hormone therapy with either androgenic steroids or recombinant human erythropoietin (rHuEPO) is the most widely-used treatment for anaemia of CRF.
However, in some cats, iron deficiency can contribute to the anaemia, both through inadequate dietary intake and intestinal blood loss. Blood tests to check iron and ferritin levels can be helpful, and ferrous sulphate, given orally, may be recommended to correct any deficit. Some vets routinely supplement CRF patients with a low dose of oral iron although this is usually quite unpalatable so may not be popular with the cat! If gastro-intestinal bleeding occurs, this also requires attention and the use of sucralfate and/or H2-receptor antagonists.
Although anabolic steroids (e.g. nandrolone) are used widely in veterinary practice, they are probably not that effective in treating anaemia caused by CRF.
The value of rHuEPO has been established in several studies, and it has the capacity to dramatically reverse the anaemia and, therefore, have a significant impact on the cat's wellbeing. However, possible benefits of treatment have to be weighed against risk of adverse side-effects and cost of the drug. Complications of rHuEPO therapy include poor response due to iron deficiency (routine iron supplementation may be prudent during therapy), hypertension, polycythaemia (an increase in the numbers of red blood cells in the blood). There is also a risk that the cat will produce anti-rHuEPO antibodies. This latter side-effect is potentially the most important, and is thought to occur in approximately 30% of treated cats, necessitating the withdrawal of treatment. Because of the relatively high prevalence of this complication, rHuEPO therapy is usually reserved for cats with moderate to severe anaemia.