Is is possible to stretch out a small bladder so that I don't have to go to the bathroom as often?

Frequency of urinati. Often referred to as a small bladder, it is a common symptom of many different problems. Training is of limited value. Medications usually help.
No. Having urinary frequency may be caused from an anatomically small bladder from various causes such as radiation. However, the majority of cases are from outflow obstruction to urine or from inflammation. The treatment is medical therapy after a negtaive evaluation has been performed.