EDLER kidney failure

Recent testing on my 82 year old mother showed H BUN level of 40 Creatinine 1.60 and BUNcreatinine ratio 25.
Her potassium was 5.4 but at the time she was taking a potassium supplement because of her lasix dieretic.
She only has one kindey now and I am wondering about low intake of water and maybe meds that might be causing some bad test results. She was recently taken off the potassium and changed to Lisinopril and bumex instead of
lasix. (She also was taking ALDOMET for about 40 years or more.. No one doctor and she has had many ever mention that Aldomet or Naproxen could be bad for her one kidney.) They took her off the naproxen and put her on
tramadol and replaced the aldomet with the lisinopril. WE are STILL wating for a kidney specialst to take her case.
I am worried about her diet so I cut the salts and am watching potassium intake. We have NOT consulted with any kind of nutrionist yet.. still waiting on the kidney specialist. Becoming concerned at all this time wasted on wating.