Why Do You Need to Fast Before an Abdominal Ultrasound?
If you're booked in for an abdominal ultrasound, then you'll be given a set of instructions telling you how to prepare for the procedure. These instructions will tell you if you need to fast before the procedure and how long you should fast for.
Why do you need to fast before you have your ultrasound? Can you eat or drink anything at all during this period?
Fasting Makes Abdominal Ultrasounds More Effective
When you have an ultrasound scan on your abdomen, the area needs to be free and clear of any obstructions. Ultrasound scans use sound waves to look at internal areas of the body. These waves can be affected by a working stomach or digestive system.
If you don't fast before your scan, then your digestive system will be processing any food you've recently eaten. This creates pockets of gas and air in your abdomen. Ultrasound waves can't go through or around these pockets; they effectively block the waves.
So, if you have eaten recently, then your scan won't give a full picture of your abdomen. If your stomach is empty after a fast, then the soundwaves work most effectively.
Fasting Rules Before an Ultrasound
Your doctor, clinic or hospital will tell you how long your fasting period needs to be. This may vary depending on the reason why you're having the scan.
During this period, you shouldn't eat anything at all. Food digestion is a major problem that needs to be avoided here. Anything you eat could affect the scan's success. If the scan can't work, you may need to have another one.
However, you may be able to drink some fluids. Generally, you'll be told to only drink clear and still fluids. For example, you can drink still but not sparkling water. You can also drink tea or coffee as long as you don't put milk or sugar in it.
You may also be asked to avoid chewing gum or smoking for a few hours before the scan. When you chew gum or smoke, you chew and suck air into your system. This air can impede the scan too if it hits your abdomen when the scan takes place.
Some people find fasting harder than others; this can also be affected by other medical conditions. For example, if you're diabetic, then not eating for the fasting hours may be more difficult for you.
In this case, you can ask for your ultrasound to be scheduled for early in the day. This way, you do most of your fasting when you're asleep and wouldn't be eating anyway.