Diagnosis of appendicitis begins by obtaining a patient history to determine the patient’s family history of appendicitis, risk factors, and symptoms. The clinician will evaluate the type and location of the pain, such as lower right abdominal pain while the patient is walking, jumping or engaging in other jarring movements. The practitioner will ask about other symptoms, such as nausea, loss of appetite, fever, or diarrhea.
A medical provider performs a physical examination to assess the patient’s overall health and to rule out other causes of abdominal pain. During the examination, the provider will likely press on the patient’s lower right abdomen, then release quickly; when the doctor releases pressure, pain from appendicitis typically worsens.
The medical provider will then order several diagnostic tests, as there is not one individual test that checks for appendicitis. These tests help the provider look for signs associated with appendicitis and rule out other conditions that cause similar symptoms.
Diagnostic tests include lab tests and imaging tests. Lab tests can check blood and urine samples, and imaging tests create images of the appendix and surrounding tissues to help doctors detect an enlarged or burst appendix, inflammation, blockages, and abscesses from infection. Lab and imaging tests are especially helpful in cases in which the patient’s appendix is in an atypical location or when the patient has symptoms common to a number of conditions.
Diagnostic tests include:
- C-reactive protein (CRP)
- Liver and pancreatic function tests
- Urinary beta-hCG
- Urinary 5-hydroxyindoleacetic acid (5-HIAA)
- Computed tomography (CT)
A complete blood count (CBC) provides medical providers with information about white blood cells (WBCs) that fight infection. A CBC also reveals the levels of neutrophils in a patient’s blood. Neutrophils are a specific type of white blood cell; a high level of neutrophils, a condition known as neutrophilia, can indicate an infection. Between 80 and 85 percent of adults with appendicitis have a high WBC count, and 75 to 78 of patients with appendicitis have neutrophilia. Less than 4 percent of those with appendicitis have low or normal WBC and neutrophil counts.
C-reactive Protein (CRP)
The liver produces C-reactive protein (CRP) in response to inflammation. There are typically low levels of CRP in the bloodstream. CRP levels rise when inflammation, like that associated with appendicitis, is present somewhere in the body but the CRP test does not indicate the cause or location of the inflammation.
Laboratories express CRP levels in terms of milligrams per deciliter, or mg/dL. CRP levels greater than 1 mg/dL are common among patients with appendicitis. Very high CRP levels in patients with appendicitis can indicate death of body tissue, known as gangrene, especially when coupled with neutrophilia and high WBC counts.
Patients who have had symptoms for more than 24 hours but have normal CRP levels probably do not have appendicitis.
Liver and pancreatic function tests
Liver and pancreatic function tests—such as ALT and AST, bilirubin, alkaline phosphatase, serum lipase and amylase—can help doctors rule out other conditions that cause signs and symptoms similar to appendicitis.
Laboratory testing of urine can help medical providers determine if symptoms are the result of appendicitis or a urinary tract condition, such as a urinary tract infection or kidney stone.
Urinary beta-hCG is a urine test that helps clinicians determine if symptoms present in women of childbearing age are from appendicitis or from an early ectopic pregnancy, which is a condition in which the fertilized egg implants outside of the uterus.
Urinary 5-hydroxyindoleacetic Acid
Urinary 5-hydroxyindoleacetic acid (5-HIAA) tests measure the amount of HIAA in the urine. The mucosa cells lining the appendix contain serotonin, a chemical that helps to control inflammation. The liver breaks down serotonin into 5-HIAA, which is a waste product flushed from the body in urine. High levels of 5-HIAA in the urine indicate an increase in serotonin production due to inflammation in the appendix, whereas low levels of 5-HIAA can indicate the death of the mucosa cells that produce serotonin. A sudden decrease in 5-HIAA levels can be an early warning sign of perforation of the appendix.
Abdominal x-rays help providers look for general problems affecting the abdomen. Providers sometimes order chest x-rays, as pneumonia in the lower lobe of the right lung can cause symptoms similar to those caused by appendicitis.
Computed tomography (CT) is a type of computerized x-ray procedure that generates cross-sectional images, known as “slices,” of tissues inside the body. CT scans have a 98 percent accuracy rate when it comes to detecting appendicitis.
Ultrasound uses sound waves and a computer to create images of tissues inside the body. These images can show fluid collecting in the abdomen, so ultrasound can help detect signs of inflammation, abscess, rupture, and other problems that could be causing symptoms.
A healthy appendix does not usually show up on an ultrasound. In patients with appendicitis, the appendix looks like a small tubular structure measuring 7 to 9 mm in diameter.
Ultrasound is safer than CT because ultrasound does not expose patients to radiation, but medical providers may order a CT scan when ultrasound results are inconclusive.
How do you rule out appendicitis?
The best way for patients to rule out this condition is to see a healthcare provider right away if they notice new or worsening pain in the lower right side of the abdomen, especially if they have other symptoms of appendicitis.
Appendicitis can be ruled out using:
- a detailed personal history,
- physical examination,
- laboratory tests, and
- imaging tests.