Renal failure in a patient with postpolio syndrome and a normal creatinine level.

Patients with renal failure who are taking trimethoprim have an increased risk of developing hyperkalemia, which can cause muscle weakness. In patients with postpolio syndrome, a normal creatinine level could be abnormally high, renal failure is possible because of lack of creatinine production, and the muscle weakness from resultant hyperkalemia could be more severe because of their underlying condition. This abnormally high creatinine level has been termed from this point relative renal failure.