A fluid collection is a common finding in the pelvis on CT, especially in reproductive age women. Other causes of fluid in the pelvis can occur from a variety of normal and abnormal causes. The clinical information such as age, sex, and history can help us determine the cause of the fluid collection in the pelvis.
Fluid in the pelvis can be a normal finding
One of the most common causes is related to the menstrual cycle and ovulation. Many reproductive age women have a small amount of fluid in the pelvis. This can also be hemorrhagic fluid. Often times, we see a follicular cyst in the ovary. The finding is often incidental or not related to the reason for the CT.
Abnormal causes of fluid collections in the pelvis on CT
Fluid collection in the pelvis on CT can also occur from a ruptured cyst. This will often lead to symptoms like pain. The quantity of fluid may be small all the way to life threatening bleeding in some cases. These cases will require surgery.
Fluid in the pelvis can occur from generalized ascites. I see this most commonly from liver cirrhosis and cancer. Liver cirrhosis can occur from many causes which lead to scarring and liver failure.
Cancer can sometimes be associated with ascites. This occurs when the cancer spreads to the lining of the abdomen or to the liver. Often we have a history of cancer or other evidence of cancer on the scan.
Fluid collection in the pelvis can be an abscess or collection of pus. This can occur from a variety of reasons such as infections of the fallopian tubes and ovaries. It can occur when patients have inflammatory bowel disease, diverticulitis, or appendicitis to name some of the causes.
Fluid collection in the pelvis can also occur when there is bleeding. Bleeding can occur from a variety of causes, like a ruptured cyst. Sometimes blood settles in the pelvis from bleeding somewhere in the abdomen. Often we scan both the abdomen and pelvis with CT and the cause can be identified.
Fluid collections can occur after surgery in the pelvis. These collections are usually around the site of the surgery and go away with time. Some of these collections can become infected in which case they need treatment.
Fluid collections occur for a variety of reasons in the pelvis. Some are benign like in reproductive age women and others are signs of poor health like cancer. Often the appearance and patient history help us with the cause of a collection in the pelvis on CT.