I Am Inquiring For My Mom; She Is 86 Years

I am inquiring for my mom; she is 86 years old and has chronic GI issues such as constipation, pain in her left side. She also complains about feeling the urge to do a bm but can't. Her current doctor has diagnosed her with IBS and prescribed numerous medications that have not helped. Could this be IBS and if so, what kind of treatments are available?