One of the first aims of investigation is to rule out any diseases such as cancer as the cause of the pain. This is very unlikely, but it needs to be checked.
This test is very helpful to make certain whether it is really the coccyx that is the source of the pain.
The doctor injects you with a local anesthetic around the coccyx, and asks you to sit down for a while. This is to see if the anesthetic relieves the pain for an hour or two. If it does, then they know that your the tissues around the coccyx are the source of the pain. If the injection does not relieve the pain, even for a while, then it is unlikely that the coccyx is the source of the pain.
The method is described in the paper: Coccydynia/Levator Syndrome, A Therapeutic Test. The paper says: "This test is inexpensive, reliable, minimally painful, without complications and should be performed when a vague rectal pain is not explained by physical findings."
For a dynamic x-ray the radiologist takes two x-rays of the coccyx, with you standing and sitting. Comparing these x-rays shows whether your coccyx moves more than normal when you sit down. If your coccyx moves too much, that shows that it is unstable. The method was developed by by Dr Jean-Yves Maigne, who found that when he used this method, he could give a firm diagnosis of the cause of coccyx pain in 70% of cases. More detail about dynamic x-rays here.
The doctor feels around the coccyx using a gloved finger, pressing gently. This may be done from the outside or the inside, by putting a finger through your anus. If the coccyx is the source of the pain, then normally there will be areas of tenderness in the tissues surrounding the coccyx.
The doctor may also investigate your lower back, to see whether the pain may be referred pain, not caused by the coccyx at all. He or she will get you to bend over, to lie down and lift each leg, and will check your reflexes.
X-rays, CT scans and MRI scans produce images of the coccyx and other tissues, and they may show a dislocation between the bones of the coccyx (often called a fracture, even if no bone is broken). Very rarely, they show a cancer.
Often, the images show nothing abnormal, and other tests like a dynamic x-ray or injection will be needed to find the cause of the pain (see below).
Unfortunately, x-rays taken of patients with coccyx pain often don't include the coccyx at all - instead they cover pelvis. You can see a video about coccyx x-rays from Dr Patrick Foye.
Colonoscopy allows the doctor to examine the inside of your colon, to see if there's anything wrong that might be causing the pain. That includes looking for cancer and other diseases. This technique does not investigate the coccyx at all - it is intended to search for other possible causes of pain, usually when the doctor is unable to identify the cause.
It is done by putting an instrument up your anus. It is, as you would expect, uncomfortable.
Author: Jon Miles