If I had tenesmes how would the doctor treat that?

Depends. Tenesmus is usually caused by an underlying problem, eg inflammatory bowel disease. By treating the underlying problem, your symptoms should get better.
Check colon. While tenesmus, the sensation of needing to have a bowel movement, can come frmo a few different problems, the most important one to get checked out involves the colon. One of the red flag signs for a colonoscopy is tenesmus. Especially if your stool has changed or you are over 50, you need someone to take a look!