What could cause an abdominal lump that comes and goes?

Sometimes you might notice a lump in your abdomen that isn't always there or seems to change in size. One possible cause is a mesenteric pseudocyst—a fluid-filled sac that forms in the tissues that hold your intestines. Its size may vary depending on how much fluid is inside, making it seem like it appears and disappears. Another possibility is a gas-filled mass; if there is extra gas in a part of your abdomen, the lump might become more noticeable at times and then settle down. In other cases, benign tumors like lipomas (which are noncancerous fatty growths) can also feel like lumps that change with your body's position or the fullness of your stomach. Since the feeling of a lump that comes and goes can have several causes, you can start by using a free symptom checker to better understand what might be causing your symptoms, and then talk with your healthcare provider. They may use tools like an ultrasound or CT scan to get a closer look and determine the cause so they can decide if any treatment is needed.