Hello,
Welcome to the ehealthforum and I am really glad to help you out.
As far as side effects of acai berry are concerned, it does not effect the kidneys which can compromise the kidney functions. Borderline kidney functions are caused by many conditions including long term high blood pressure or diabetes, medications, or severe blockage by an enlarged prostate. Kidney function also declines with age. Other conditions other than kidney conditions may also cause borderline kidney functions.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care.