I am not aware of an abdominal mass being related to bladder spasms.
Before attributing it to this, you may want to consider imaging studies (i.e. a abdominal or pelvic CT scan) to ensure it isn't anything more than spasms.
You may also want to inquire about a urinalysis to ensure there is no infection - which would be the most common reason for bladder spasms.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
Medical Weblog:
kevinmd_b