What could cause these symptoms ? Joint and muscle pain , kidney failure , black stools and pain in the toes . I also right hip , both knees and left foot ... also the big toe of the left foot hurts. I have lots of stiffness in the lower back .

Having kidney failure is probable that uric acid levels are high and this can cause gout and arthritis finger , if it took nonsteroidal medications and have kidney failure, you are more prone to suffer from gastritis or ulcer disease peptide , which would cause bleeding and thus the black stools . Depending on the extent of kidney failure, joint pain may also be a side effect or correlate . Of course there are many other possibilities and this is not the only possible case . Need done a good evaluation, define the driving forces behind every problem and get proper treatment.