What are appendicitis tests?

Appendicitis is an inflammation (swelling) or infection of your appendix. Your appendix is a small finger-like pouch attached to your large intestine. It's located in the lower right side of your abdomen (belly).

The cause of appendicitis isn't always clear. Your appendix may become inflamed or infected if something blocks the opening where it attaches to your intestine. If appendicitis isn't treated promptly, your appendix can burst and spread bacteria in your abdomen. This can lead to a life-threatening bacterial infection. A burst appendix can also cause a pus-filled infection in your appendix called an abscess.

Appendicitis typically causes abdominal (belly) pain in your right side. But some people may have different symptoms because their appendix isn't in the usual place. This can make appendicitis hard to diagnose. Appendicitis tests help your health care provider make an accurate diagnosis quickly so you can get proper care.

Appendicitis tests may include:

• Blood tests to look for signs of infection and inflammation that may mean you have appendicitis. But blood tests can't diagnose appendicitis.
• A urine (pee) test to rule out a urinary tract infection and/or a kidney stone. These conditions can cause symptoms similar to appendicitis.
• Imaging tests to take pictures of your appendix. If your symptoms and other tests suggest that you have appendicitis, imaging tests can confirm the diagnosis.

Appendicitis can happen at any age, but it's more common in people in their teens and twenties. The main treatment for appendicitis is an appendectomy, which is surgery to remove the appendix. Your appendix has no known function, and you don't need it to be healthy.

What are they used for?

Appendicitis tests are used to confirm or rule out a problem with the appendix in people who have appendicitis symptoms.

Why do I need appendicitis testing?

You may need testing if you have abdominal (belly) pain that usually:

• Starts near your belly button and moves lower and to your right
• Hurts more when you move, take deep breaths, cough, or sneeze
• Gets worse within hours

If you have any severe abdominal pain, it's important to get medical help as soon as possible.

Along with pain, other appendicitis symptoms include:

• Nausea and vomiting
• Fever
• Loss of appetite
• Swelling in your abdomen
• Diarrhea or constipation
• Problems passing gas

What happens during appendicitis testing?

Before ordering appendicitis tests, your provider will ask questions about your symptoms and medical history. You'll also have an exam. If your provider thinks you could have appendicitis, you may have one or more tests to help confirm or rule out the diagnosis.

Blood tests can help find out if you have an infection or inflammation in your body, but these tests can't show whether appendicitis is the cause.

To collect a blood sample, a health care professional will insert a small needle into a vein in your arm to collect a small amount of blood into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Urine tests can help rule out a urinary tract conditions that could be causing your symptoms.

To collect your urine sample, a health care professional may give you a cleansing wipe, a small container, and instructions for how to use the "clean catch" method. It's important to follow these instructions so that germs from your skin don't get into the sample.

Imaging tests check to see if your appendix looks normal. These tests can confirm whether you have appendicitis. They include:

• CT scan (computed tomography scan). A CT scan is the most accurate imaging test for diagnosing appendicitis. For this test:
  • A contrast dye may be used to make your tissues and organs show up better in the pictures. The contrast dye may be given as:
    • A drink that you swallow
    • An injection into a vein using an intravenous (IV) line
    • An enema, which is a tube that injects the contrast medium into your intestine through your anus
  • You will lie still on a table that passes slowly through the center of a large donut-shaped x-ray machine. For some scans, the x-ray machine moves around you to take pictures. You may hear whirring sounds from the machine.
• An ultrasound makes pictures using sound waves. For this test:
  • You'll lie on an exam table and a healthcare professional will put a special gel on your abdomen.
  • A handheld wand-like device will be moved across your abdomen and images of your organs will show on a monitor.
• An MRI scan makes pictures using magnets and a computer. For this test:
  • You may be given a dye through an intravenous (IV) line.
  • You'll lie very still on a table that slides into an MRI scanner, which is a tunnel-shaped machine. If you have trouble being in closed-in spaces, talk with your provider about options that may make you more comfortable.
  • You may be given earplugs or headphones to help block loud sounds from the scanner.

If there's a chance you could be pregnant, you will likely have a pregnancy test to rule out an ectopic pregnancy, which can cause pain similar to appendicitis. It's also important to know whether you're pregnant before having a CT scan. That's because the x-rays could harm an unborn baby. A pregnancy test may be done with a blood or a urine test.

Will I need to do anything to prepare for the tests?

Blood and urine tests don't require any special preparations.

For imaging tests, you may have to stop eating and drinking for several hours before the test. Your provider will tell you how to prepare.

Are there any risks to the tests?

A blood test has very little risk. You may have slight pain or bruising at the spot where the needle was put in, but it usually goes away quickly.

A urine test has no risk.

Imaging tests are safe. If your test includes contrast dye, there's a small chance you could have an allergic reaction to it. Reactions can often be managed with medicine. If you get the dye through an IV, it may cause a slight burning feeling.

• CT scans are generally safe. They do use x-rays which are a form of radiation. The small amount of radiation in a CT scan is not considered harmful to most adults. But exposure to radiation can slightly increase the risk of developing cancer later in life. Children and unborn babies are more sensitive to radiation than adults because their bodies are still growing.

  If you're concerned about radiation exposure for yourself, your unborn baby, or your child, ask about other imaging tests to diagnose appendicitis. If your child needs a CT scan, ask if the machine will be adjusted to use the lowest amount of radiation possible.

• An ultrasound has no risk.
  
  
• MRI scans are generally very safe. But if you have certain metals and/or implanted medical devices in your body, ask your provider if you can have an MRI.

What do the results mean?

To confirm or rule out appendicitis, your provider will consider your symptoms, medical history, and the results of your exam and appendicitis tests.

Blood test results:

• A high white blood cell count means you probably have an infection. But the test results don't show what's causing the infection. It's also possible to have appendicitis with a normal white blood cell count.
• A high level of c-reactive protein (CRP) in your blood means that you have inflammation in your body that could be from appendicitis. But this test alone can't diagnose appendicitis.

Urine test results:

• A high level of white blood cells or bacteria in your urine may means that a urinary tract infection is causing your symptoms.
• Blood, crystals or high levels of certain minerals in your urine may mean that kidney stones are causing your symptoms.

Imaging test results:

• An appendix that is blocked, larger than normal, burst, or has an abscess means that you probably have appendicitis.
• If your appendix looks normal, imaging tests may help find other problems that could be causing abdominal pain.

If your provider diagnoses appendicitis, you'll usually have surgery to remove your appendix as soon as possible before it can burst. If your appendix has already burst, you must have surgery right away. The surgeon will remove your appendix and clean the infection from your abdomen.

Learn more about laboratory tests, reference ranges, and understanding results.