Phoenix CyberKnife · Radiation Oncology
Bladder & Bowel Prep
for Radiation Therapy
Prostate Treatment Patients
TrueBeam Protocol
CyberKnife Protocol
Why this matters
A full bladder helps protect healthy tissue around your prostate
An empty rectum improves treatment accuracy
Doing this the same way every day improves consistency
Bladder prep
Empty your bladder first
Drink 20–24 oz of water
Finish 30–45 min before treatment
Do not urinate after drinking
Bowel prep
Have a bowel movement before your visit
Avoid gas-producing foods
Use an anti-gas aid if recommended by your care team
Before your appointment
Bladder feels comfortably full
No strong urge to urinate
Bowel movement completed (if possible)
Minimal gas or bloating
Common issues
Bladder too full?
Let staff know when you arrive — timing can be adjusted
Not full enough?
You may be asked to drink more water before treatment begins
Gas or discomfort?
Tell your therapist before treatment — don't wait
🔁
Same routine every appointment
⏰
Drink water at the same time daily
🍽️
Keep meals consistent throughout
Why this matters
CyberKnife delivers very precise radiation — consistent prep helps it work as intended
A full bladder helps protect healthy tissue around your prostate
An empty rectum improves treatment accuracy
Your prep starts a couple days before simulation — we'll guide you every step
Pick up before you start
Fleet enemas
Milk of Magnesia
Night before simulation only
Dulcolax
Night before each treatment only — not for simulation
Gas-X (simethicone)
Simulation prep
Leading up to simulation
2 days before simulation
Start low-fiber, low-gas diet
Take Gas-X with every meal
Night before simulation
Take Milk of Magnesia as directed
Continue low-fiber dinner + Gas-X
Day of simulation
Morning of simulation — before leaving home
Use Fleet enema and allow full evacuation
30 minutes before treatment
Drink 20–24 oz of water
Do not urinate after drinking
Treatment day prep
Leading up to each treatment
2 days before treatment
Continue low-fiber, low-gas diet
Take Gas-X with every meal
Night before treatment
Low-fiber dinner + Gas-X with meal
Take Dulcolax as directed (treatment nights only)
Day of each treatment
Morning of treatment — before leaving home
Use Fleet enema and allow full evacuation
30 minutes before treatment
Drink 20–24 oz of water
Do not urinate after drinking
Bladder prep
Empty your bladder first
Drink 20–24 oz of water
Finish 30 minutes before treatment
Do not urinate after drinking
Bowel prep
Fleet enema before every appointment
Gas-X with every meal
Low-fiber diet throughout
Milk of Magnesia — night before simulation only
Dulcolax — night before each treatment only
Low-fiber diet guide
Good choices
White bread or toast
White rice, pasta
Eggs
Chicken, fish
Yogurt
Cooked carrots
Avoid these
Beans, lentils
Broccoli, cabbage
Raw vegetables
Carbonated drinks
High-fiber cereals
Onions, garlic
Gas-X (simethicone) is available at any pharmacy without a prescription. Take it with every meal starting 2 days before your simulation.
Before each appointment
Enema completed before leaving home
Drank 20–24 oz of water 30 minutes before treatment
Bladder feels comfortably full
No strong urge to urinate
Minimal gas or bloating
Common issues
Bladder too full?
Let staff know when you arrive — timing can be adjusted
Not full enough?
You may be asked to drink more water before treatment begins
Gas or discomfort?
Tell your therapist before treatment — don't wait
Trouble with the enema?
Call us before your appointment so we can help you plan
🔁
Same routine every appointment
⏰
Drink water at the same time daily
🍽️
Keep meals consistent throughout