First on my list is acidifying diets becuase these could contribute to hypokalemia (low serum potassium, which further injures the kidney) and metabolic acidosis.
http://www.walthamusa.com/articles/wf83bro.pdfHypokalemia is most often observed in polyuric cats (2). In feline
patients it may indicate inadequate potassium intake and/or the
effects of an acidifying diet to promote kaliuresis. Hyperkalemia is
uncommon except in the terminal phases of CRF and is often
associated with oliguria or anuria.
Hypokalemia has a variety of adverse effects, including a
reduction in renal function. In hypokalemic cats, the first step is to
switch to a diet with a high-potassium, low-acid content such as
those formulated for the treatment of feline CRF.
...
Proteins, particularly those of animal origin, are rich in sulfurcontaining
amino acids; metabolism of these leads to hydrogen ion
generation. Consequently, many diets fed to cats provide a net load
of acid, which must be excreted by the kidney if acid–base balance is
to be achieved. Unfortunately, cats with reduced renal mass are less
able to excrete acid, potentially resulting in metabolic acidosis from
acid retention. This is generally associated with an increased anion
gap due to the accumulation of unmeasured anions, and the acidosis
may cause lethargy and inappetence.
