This page will cover a search pattern that can be used to read an abdominal/pelvis CT scan (specifically an IV contrast enhanced study in the portal venous phase).
Disclaimer: It is important to remember that many different versions of a search pattern for a CT scan of the abdomen and pelvis with IV contrast may exist. Factors that may influence a search pattern may include: the preference of the person interpreting the scan, the amount of time available to read the scan, the study question, the software being used for image interpretation, the amount of monitors being used during the reading, as well as many others.
This page just provides one example in a specific context of how to apply a specific search pattern. The goal is to provide a foundation to learners so that they will be in a better position to craft their own search pattern(s).
BEFORE YOU START BE FAMILIAR WITH WINDOWING
This page, and the associated videos, assume that the reader is familiar with the concept of CT windowing and how to use different types of windowing settings for image interpretation. This page provides a good review of CT windowing if needed.
OUTLINE OF SEARCH PATTERN
This particular search pattern follows the “outside in” approach and the major sections are as follows below:
- Scout Images
- Soft Tissues
- Solid Organs
- GI Tract
- Lymph Nodes
STEP 1 SCOUT IMAGES
It is important to realize that most all CT scans will include scout images that essentially are equivalent to plain film radiographs of the scanned region. It can be useful to look at these scout images first as they can provide some information that may be heard to appreciate on the cross sectional imaging (for example some hardware or fractures may be most easily appreciated on the scout images).
SETTING UP MULTIPLE ORIENTATIONS
After finishing looking at the scout images, it can be very helpful to set up multiple orientations of the scan so you can co-localize findings and anatomy on multiple views easily. The video below shows how this can be done easily and how reference lines can be turned on so that you know on multiple views where exactly you are looking on a scan.
STEP 2 SOFT TISSUES
The first area to look at in the outside in approach (after the scout images, and after you have configured your viewing settings) is the soft tissues. It can be useful to divide the soft tissues into 4 sections: anterior, posterior, right, and left. When scanning up and down the abdomen, one can begin with the anterior soft tissues (as this is where much of the pathology seems to reside) and then alternate between other sections as the scan up and down the scan. Make sure to use an appropriate window like the abdominal window to evaluate the soft tissues.
STEP 3 BONES
After finishing the soft tissues, the bones can be evaluated from the top of the scan to the bottom. The video below shows how to evaluate the bones in multiple planes. Make sure to utilize the bone windows and thinner slices/bone reformats/bone kernels when looking at the bones particularly in the axial orientation (if available).
STEP 4 LUNGS
Upon completing the bones, you can begin to evaluate the portions of the lung parenchyma that you can visualize on your scan. In addition to the lungs themselves, it is useful to look at the airways and the pleural spaces for pathology as well. Make sure to switch to the lung window at this step.
STEP 5 SOLID ORGANS
After looking at the lungs, you can go back to the top of the scan and begin to evaluate the solid organs in the scanned region, beginning with the heart and transitioning down below the diaphragm to the liver, gall bladder, pancreas, etc. Make sure to transition back to the abdominal window when looking at the abdominal organs.
STEP 6 GI TRACT
At the end of looking at the solid organs (in the video above) the last organs that are evaluated are deep in the pelvis (bladder, prostate/uterus) and can seamlessly transition to evaluating the GI tract staring at the rectum and tracing the GI tract back to the terminal ileum and cecum.
STEP 7 ARTERIES
The next step is to trace the arteries. It can be helpful to again start at the top of the scan, with the pulmonary arteries to evaluate for a pulmonary embolism, and then transition to tracing the aorta and its great vessels. Typically one can start with the abdominal window and then manually window to visualize the vessels of interest appropriately.
STEP 8 VEINS
The next step is to trace the veins. After finishing tracing the arteries, the video above ends with tracing the femoral arteries at the bottom of the scan. At this point one can naturally transition to tracing the veins in the opposite direction starting with the femoral veins. Typically one can start with the abdominal window and then manually window to visualize the vessels of interest appropriately.
STEP 9 LYMPH NODES
After finishing all other portions of the search pattern, we can end by going back and quickly looking for lymphadenopathy throughout the scan. Arguably during the other portions of the search pattern one should always be looking out for enlarged or suspicious lymph nodes, however sometimes it is useful to dedicate some time at the end of the scan to specifically look for lymphadenopathy. Often times the abdominal window is used to assess for lymphadenopathy.
Page Updated: 01.05.2020