Diagnosing gastrinoma

You have some tests to diagnose a gastrinoma. This might include blood tests and a test to look at the inside of your food pipe, stomach and small bowel. Your GP can refer you to see a specialist.

Gastrinoma is a type of neuroendocrine tumour (NET) that starts in neuroendocrine cells that make the hormone gastrin. Gastrinomas produce gastrin, which increases the amount of acid in your stomach. So you might see your GP because of symptoms caused by having too much acid in your stomach. 

Seeing your GP

You usually start by seeing your GP. They will ask you about your general health, symptoms and may also examine you. 

Your GP might check your blood pressure, heart rate and temperature. They may arrange for you to have some tests such as:

• blood tests
• a camera test to look into your food pipe and stomach (endoscopy)

Your doctor will then decide if you need to see a specialist.

Referral to a specialist

Your GP looks at your symptoms and decides what specialist to refer you to. For example, they might refer you to the gastrointestinal (GI) team if you have symptoms of acid reflux or stomach ulcers. 

The specialist might ask you to have more tests. If tests show that you have a gastrinoma, your specialist will refer you to a team of doctors and specialist nurses who have expertise in treating NETs. 

Tests

You have tests to check:

• whether you have a NET
• the type of NET you have
• the size of the tumour
• whether it has spread 

Your doctor might have prescribed you drugs such as omeprazole and lansoprazole to reduce the amount of stomach acid. These drugs affect the results of some of the tests. So your doctor might ask you to stop taking them between 1 and 2 weeks before. 

Some of the tests you might have include:

A test to check the amount of gastrin

The first test you have measures the amount of gastrin in your blood. This is called a fasting serum gastrin (FSG) test. You must not eat anything between 8 and 12 hours before you have this test. 

Blood tests

Blood tests can check your general health. They can also check the levels of certain substances in the blood which are sometimes raised with NETs. 

You may also have a blood test to check for a rare inherited condition called multiple endocrine neoplasia 1 (MEN1). This test is usually only requested by specialist doctors (genetic doctors). 

Endoscopy

This test looks at the inside of your food pipe, stomach and bowel. Your doctor uses a long flexible tube which has a tiny camera and a light on the end of it. Doctors can take samples of any abnormal areas (biopsies).

Endoscopic ultrasound scan (EUS)

This test combines an ultrasound and endoscopy to look at the inside of your food pipe, stomach, pancreas and bile ducts. 

Your doctor uses a long flexible tube (endoscope) with a tiny camera and light on the end. It also has an ultrasound probe. The ultrasound helps the doctor find areas that might be cancer. They then can take samples (biopsies) of any abnormal areas.

CT scan

This scan can show up a NET and see whether it has spread anywhere else in your body.

Radioactive scan

These are octreotide scans (or octreoscans) or gallium PET scans. You have an injection of a low dose radioactive substance, which is taken up by some NET cells. The cells then show up on the scan.

MRI scan

An MRI scan takes detailed pictures of your body. You might have an MRI scan to check if the gastrinoma has spread to other parts of the body such as the liver. 

Gastric pH test

A gastric pH test measures the amount of acid in your stomach. This helps to tell whether the high levels of gastrin are caused by the gastrinoma or by something else. 

You might have this test when you’re having a test to look at the inside of your food pipe and stomach (endoscopy). Or you may need to have a tube put into your stomach to get a sample of the acid. Your doctor passes a tube called a nasogastric tube from your nose, down the food pipe, into your stomach. They attach a syringe to the tube and take some fluid out before removing the tube.

Selective angiography with secretin stimulation

This test combines an x-ray of your blood vessels (angiography) and a test which makes gastrinomas produce gastrin. 

Your doctor gives an injection of calcium into each one of the main blood vessels (arteries) in the gut. This makes gastrinomas produce gastrin and release it into the bloodstream. After 30 seconds, your doctor takes blood samples from each artery to measure the amount of gastrin. 

This test can show the position of the gastrinoma based on which blood vessel it is close to.