This abdominal pain can be unrelated to the Mirena IUD. It can be due to bowel obstruction, ovarian cysts (females) and pelvic inflammatory disease,irritable bowel syndrome , kidney obstruction or pyelonephritis, psoas abscess and volvolus (twisting of the sigmoid part of the large bowel on itself).In case of females it can be due to involvement of the female reproductive organs.
Investigations like ultrasound abdomen, CT abdomen and colonoscopy are required to confirm a diagnosis. My advice is to consult a doctor and discuss these possibilities with him.
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 and please do keep me posted on how you are doing.