Did you have a stool test to check for pathogenic causes to your symptoms (things like Clostridium difficile, Colitis, or Proctitis)? Stuff like Small intestinal bacterial overgrowth (SIBO) can occur as well.
Often the biggest reason patients seek out an Ulcerative Colitis diagnosis is blood in stool, which you do not mention. As an example, I had bright red toilet water after every, single BM for a series of weeks.
Certainly they can do various xrays with a radioactive dye you swallow to see where within your digestive system there is inflammation. As you said you were unable to complete the colonoscopy.
There's also a Prometheus Labs blood test, IBD sgi Diagnosticâ„¢, that can help determine what you have. It's fairly new, but might be helpful.
/www.prometheuslabs.com/Products/Default.aspx?section=GIDiagnostics