Fat stranding on CT means that the fat which is ordinarily dark and uniform becomes dirty looking with brighter patchy areas. This can happen for many reasons including infection. Fat stranding on CT brings the radiologist attention to an area indicating a possible abnormality.
What can cause fat stranding on CT?
Fat stranding is commonly seen when a a patient has an infection or inflammatory process. It can also be seen from edema or excess fluid. Fat stranding on CT can occur after a patient has surgery. It can also be seen within or around a cancerous mass.
Infection and inflammation
Most commonly, fat stranding occurs when something in the body is inflamed. An example of this would be appendicitis. The appendix is a blind ending wormlike structure attached to the cecum or start of the colon. When the appendix becomes inflamed we have appendicitis. Appendicitis often has fat stranding around it. The fat on CT becomes dirty looking and the appendix is abnormal.
Another example is when we get an infection of the kidney or bladder. We can see fat stranding on CT around the kidney and bladder. Often, a test of the urine and physical exam findings will help confirm the diagnosis.
Fat stranding can also be seen around an abscess or collection of pus. This will often be drained and treated with antibiotics. Fat stranding on CT is also commonly seen around inflamed pockets or diverticula arising from the colon. This is called diverticulitis.
Edema or fluid
Fat stranding on CT can simply mean there is edema or fluid in the body. This commonly occurs when a patient is overloaded with fluids because of heart or kidney failure or because too much fluid was given to the patient through an intravenous line. This will often be more diffuse and not isolated to one small area or organ.
Fat stranding on CT is common after surgery. This is reaction to the surgery itself. Following hysterectomy for example, there is often stranding and pockets of fluid in the pelvis. Same with gallbladder surgery and many other surgeries. Fat stranding can also be seen with infections following surgery. It is therefore important for the clinical doctors to correlate what’s going on with you outside of imaging tests.
Fat stranding on CT can also occur around cancers. This may mean that the cancer is spreading to the surrounding tissues. It may also be seen after a tumor is treated with radiation therapy or surgery. Some cancers look infiltrative. This means they are not round balls but extend through the tissues in an irregular pattern. This can sometimes look like fat stranding on CT.
Fat stranding on CT can mean many things as outlined above. It can be benign fluid, infection, following procedures or surgery or even cancer related. Often CT will give clues as to the importance of fat stranding. Whether this is related to a benign abnormality like fluid or one which needs surgery like appendicitis.
It is therefore important for your doctors to use all the available information outside of the imaging test to determine the best diagnosis and to see if the finding is relevant. Not every imaging test finding is clinically important. The radiologist who interprets the exam will also use all the information available to arrive at the most appropriate diagnosis.