Here are some disorders contributing to lower right/left abdominal pain in the absence of pathalogical /physiological evidence.
(1) spastic colon - medication available for relief
(2) stress makes diaphragm under rib cage to tighten. So inhale deep breath hold for 5 secs and exhale from mouth, forcing the diaphragm to relax. doing exercises to stretch your spine and relaxation. Along with tightening of diaphragm muscles near rectum, lower abdomen can also tighten and go into spasm.
(3) Pain inside bones of the lower back ( not shown on MRI or X-Ray) like coccyx, sacro-coccygeal joint can also radiate in groin area, lower abdominal area. cured with steroid injections to the bones and/or related physio-therapy exercises.
(4) For severe pain attacks in upper abdomen/chest like for gall bladder infections; test blood for H-Pylori bacteria before removing gall baldder unless absolutely necessary because H-Pylori can cause identical sympthoms.
(5) Internal hernia , pelvic organ pro-lapse, pelvic floor laxity could also create discomfort in lower abdomen.