When your child’s doctor orders an abdominal ultrasound, we need to look at the liver, gallbladder, pancreas, spleen, and kidneys. If anything has been eaten in the past few hours, we may not be able to see those areas well enough to get an adequate evaluation. When you eat/drink, the stomach and intestines digest those items and air is produced, filling up a large part of the abdomen with a “wall” of air that ultrasound cannot see past. The sound waves that the ultrasound machine uses to create pictures of the abdominal organs can’t see through this air blockade. Sound travels very well through fluid but not air. So, waiting a specific amount of time after eating is very important to be able to get the necessary pictures for your child’s exam.
Believe it or not, chewing gum can also cause air in the abdomen. Because many organs are surrounded by the stomach and intestines, this air can obscure any anatomy within the same area, such as the pancreas. In addition to the increased air, other areas, like the gallbladder, cannot be properly seen after eating. This is because part of the digestive process involves the gallbladder releasing bile through the bile ducts. This process causes the gallbladder walls to collapse making it impossible to see inside. It takes several hours for the gallbladder to fill back up with bile.
Evaluating blood flow to/from the organs in the abdomen can also be affected by eating before the exam. There are guidelines given to you based on age that usually allows enough time for food to be digested so we can get the necessary pictures your child’s doctor needs. When you schedule the ultrasound, you will be told how long your child should not eat/drink before the ultrasound exam.
Pylorus ultrasounds are another type of exam of the abdomen that requires a prep of nothing to eat. This exam is usually done on infants 4-12 weeks of age. A three-hour fasting is needed to reduce air in the abdomen and allow time for the stomach to empty. This aids in visualization of the pylorus (where the stomach empties into the intestines).
Exams such as hips, heads, and spines have a no-eating prep as a method to calm your child. These types of exams are done on infants and involve not feeding him or her 2-3 hours before the exam. Doing so makes your infant hungry enough to take a bottle during the exam, which keeps them distracted and cooperative, allowing us to get the pictures we need.
Questions and concerns can be addressed at any time. Our goal is to make the ultrasound exam a good experience for your child while providing his or her physician with as much information as possible to aid in care.
If you have questions, or would like to request an appointment, please contact our Radiology and Medical Imaging Department.
Contributed by Paula Bennett (RT-US) and edited by Tony Dandino (RT-MR).