Stricture in the colon

Can anyone tell me what test would be required to diagnose a stricture in the transverse colon or splenic flexure?

I have already had colonoscopy (which found mild diverticular disease in the sigmoid, too mild to cause a problem according to the GI doc). Have also had 3 u/s scans, CT scan and MRI scan of abdomen, as well as barium swallow of small bowel.  But continue to suffer with pain and congestion even though I am not constipated.