Incidental finding of sacral hemiagenesis on the (99m)Tc-MDP bone scan as a casual regression syndrome type II.

A 69 years old woman with chronic low back pain referred to our Department for bone scintigraphy. Patient did not have any other complaint and his physical examination of the patient was normal. Whole-body scan was acquired 3 h after the intravenous injection of 740 MBq of technetium-99m methylene diphosphonate ((99m)Tc-MDP). Distal sacrococcygeal region could not be observed during the visual analysis of the whole-body scan. Pelvic X-rays radiography and pelvic computed tomography of the patient, demonstrated hemiagenesis of the sacrum, which was consistent with type-2 sacral agenesis. Other structural abnormalities were not detected on the pelvic CT scan of the patient. This case is presented to demonstrate the rare congenital anomaly of sacral hemiagenesis causing empty pelvis appearance in the posterior projection of (99m)Tc-MDP whole body bone scan. This congenital anomaly could be associated with extensive abnormalities of the lower vertebrae, pelvis, and spine.