An incidental finding is a lesion discovered on an imaging test that is unrelated to the reason for the exam. Incidental findings can be found on any imaging test. Incidental findings range from benign abnormalities which can be ignored to life threatening conditions which must be addressed urgently.
Incidental findings are common because imaging volumes have increased, especially CT and MRI. Advanced imaging allows a detailed look inside the body and often detects findings which are unrelated to the reason for the exam. There are guidelines from radiology societies to address some of these findings and how to follow them. Other findings depend on the radiologist who is reading the exam.
A very common incidental finding is finding a lung nodule on a test. This can be a CT of the chest, abdomen or anything that images a part of the chest. Nodules are mostly benign, especially when smaller than say a centimeter. The risk of a cancer goes up with size. The fleischner society has put out guidelines for following and evaluating these nodules. Solid nodules less than 8 mm are often followed with imaging tests and those above may undergo PET CT or biopsy.
Incidental findings can also be seen on X-rays. For example, a shoulder x ray can uncover a lung mass. Shoulder X-rays often show a portion of the lung on the side being X-rayed. A pelvic X-ray done to look for fractures of the bones can show calcifications in the pelvis which can be seen with fibroid tumors of the uterus. An X-ray of the abdomen done to look for kidney stones may show stones in the gallbladder. Any X-ray that includes the bones may show a bone lesion or tumor.
Incidental findings on CT and MRI are extremely common. For example, a CT done to look for appendicitis may show kidney stones or a mass somewhere. A CT done to look for a bleed after trauma may show a brain abnormality which is unrelated. A CT done to look for clots in the lungs may show nodules in the lungs or enlarged lymph nodes.
MRIs also often show incidental findings. An MRI of the abdomen done to look at the liver may show cysts or masses in other organs. An MRI of the spine done for pain may show something abnormal in the bones or even in organs like the kidneys. An MRI of the brain done for headache may show something in the skull, like a bone lesion.
Incidental findings are unexpected findings. Those which are unrelated to the reason for the test. These findings can be benign such as cysts or calcifications. All the way to deadly findings like tumors, bleeds and clots. The radiologist who reads a study scrutinizes every inch of it for findings. Given the detail on scans, it’s not surprising that all types of findings are often discovered, some of which are life threatening.