Diagnosis

Your doctor will assess your signs and symptoms to rule out other causes of skin flushing and diarrhea. If no other causes are found, your doctor may suspect carcinoid syndrome.

To confirm a diagnosis, your doctor may recommend further tests, including:

• Urine test. Your urine may contain a substance made when your body breaks down serotonin. An excess amount of this substance could indicate that your body is processing extra serotonin, the chemical most commonly excreted by carcinoid tumors.
• Blood test. Your blood may contain high levels of certain substances that are released by some carcinoid tumors.
• Imaging tests. Imaging tests may be used to locate the primary carcinoid tumor and determine whether it has spread. Your doctor may start with a CT scan of your abdomen, because most carcinoid tumors are found in the gastrointestinal tract. Other scans, such as MRI or nuclear medicine scans, may be helpful in certain situations.

• A scope or camera to see inside your body. Your doctor may use a long, thin tube equipped with a lens or camera to examine areas inside your body.

An endoscopy, which involves passing a scope down your throat, may help your doctor see inside your gastrointestinal tract. A bronchoscopy, which uses a scope passed down your throat and into your lungs, can help find lung carcinoid tumors. Passing a scope through your rectum (colonoscopy) can help diagnose rectal carcinoid tumors.

• Removing tissue for laboratory testing. A sample of tissue from the tumor (biopsy) may be collected to confirm your diagnosis. What type of biopsy you'll undergo depends on where your tumor is located.