Dad learned at his doctor appointment this week that his kidneys are stable.  Meaning that he's not suffered any more damage to them since their function was first measured post-stroke.  He has 29% of his kidney function which puts him just inside stage 4 of Chronic Kidney Disease (CKD).  Doctors don't usually recommend dialysis until you're in the 10-15% range or have severe symptoms.  From what I can tell, Dad doesn't appear to have any noticeable symptoms yet, which is great.  The doctor did say that Dad is anemic, and they are having some additional blood work done.

The nephrologist continues to look for the root cause of his CKD.  High blood pressure is the chief contributor, but the fact that he lost so much function so quickly seems to indicate that something else was at work as well.  He suspects it might be a blood cancer Multiple Myeloma, but isn't sure yet.  The blood tests will tell if he has an elevated amount of protein in his blood which can indicate the condition. If the blood tests come back positive, he may have to have a bone marrow biopsy to confirm. The the size of his kidneys is L=11.3 cm  R=11.8 cm which is about normal.  His vitamin D level is very good.

UPDATE: the blood work came back a few days later and showed that Dad did NOT have an elevated level of protein in his blood.  That means that he apparently doesn't have the Multiple Myeloma condition.  We're all so thankful.