How do you manage bladder fullness during cervical T&O brachytherapy to minimize OAR dose?

We usually treat with empty bladder as it is reproducible. But if at first fraction any loop of small bowel close by then for remaining fractions we simulate and treat with full bladder to decrease dose to small bowel (usually 120-180 cc fluid).

We usually end up instilling fluid into the bladder (100-200cc) and clamp Foley at time of CT simulation. At times, patients develop some pressure sensation during the wait between CT sim and treatment, at which point we instruct nursing to unclamp temporarily, as patients are continuing to generate urine.

It makes small bowel anterior to uterus not an issue in regards to OAR dose constraints. Can't say the same for small bowel wrapped or adhered to the uterus at other locations.

We will evaluate at fraction 1, but if MD feels bladder instillation will help (which it does probably 66-80% of the time) we will either re-CT after bladder instillation (for the attending who does not do MRI with every fraction) or contour OARs on MRI (for the at...