Diskography doesn't have many complications associated with it. In a very, very small number of people an infection can develop. This is called diskitis. It's painful but can be cleared up with antibiotics. Newer and better ways of doing diskography have almost eliminated this problem.
Even less often than diskitis headache, nausea, and hematoma can occur. The most common problem is that the back pain gets much worse after the test. This is a temporary but unpleasant drawback. Pain relievers and muscle relaxants may help.
Studies over 20 years' time haven't shown any long-term problems or damage to the disc from this test. It's safe and accurate.