Testing for appendicitis involves a combination of physical exams, blood work, and imaging, usually a CT scan. No single test confirms it on its own, so doctors layer several approaches to build confidence in the diagnosis. The whole process can happen within a few hours in an emergency department.
The Physical Exam
The first step is a hands-on examination of your abdomen. The doctor is looking for specific patterns of pain that point toward the appendix rather than other causes of belly pain. Several named maneuvers help narrow things down.
The most well-known is pressing on McBurney’s point, a spot about one-third of the way from your right hip bone toward your belly button. Sharp tenderness there is a classic sign. The doctor will also test for “rebound tenderness” by pressing down on your abdomen and then quickly lifting their hand. If the release hurts more than the pressure itself, it suggests the lining of your abdominal wall is inflamed, which happens when an infected appendix irritates nearby tissue.
Another test, called the Rovsing sign, involves pressing on the left side of your lower abdomen. If that pressure causes pain on the right side, it’s another clue pointing to the appendix. Your doctor may also ask you to lie on your left side while they extend your right leg backward. Pain during this movement suggests the appendix is sitting near a deep hip muscle and irritating it as it swells. Not every test will be positive in every case, but the combination of results helps the doctor decide how urgently to move to imaging.
Blood Tests
A blood draw is standard. Doctors check your white blood cell count, which rises when your body is fighting infection. In most cases of appendicitis, the count is elevated, typically around 12,000 to 13,000 cells per microliter. A count above 16,000 can signal a more severe form where tissue has started to die. That said, a normal white blood cell count doesn’t completely rule appendicitis out. In one study, five out of 35 confirmed appendicitis cases had normal counts.
C-reactive protein (CRP), another inflammation marker, adds useful information. Levels above 40 mg/L tend to appear with active, pus-forming appendicitis. CRP above 100 raises concern for a perforated or gangrenous appendix. Together, these two blood markers help gauge both the likelihood and severity of the problem, but neither is reliable enough to confirm or exclude the diagnosis alone.
The Alvarado Score
Many emergency departments use a simple scoring system called the Alvarado score to decide how aggressively to pursue imaging. It assigns points across eight findings, totaling a maximum of 10:
- Pain migrating to the right lower abdomen: 1 point
- Loss of appetite: 1 point
- Nausea or vomiting: 1 point
- Tenderness in the right lower quadrant: 2 points
- Rebound pain: 1 point
- Elevated temperature: 1 point
- High white blood cell count: 2 points
- Shift in white blood cell types toward infection-fighting cells: 1 point
A low score makes appendicitis unlikely and may spare you further testing. A high score pushes the team toward imaging or even straight to surgical consultation. Scores in the middle range are the ones that typically lead to a CT scan to settle the question.
CT Scans: The Most Accurate Test
A CT scan of your abdomen is the gold standard for confirming appendicitis in adults. A large meta-analysis found CT has a pooled sensitivity of about 97% and specificity of 96%, meaning it catches nearly all true cases and rarely flags a healthy appendix as diseased. When both oral and intravenous contrast dye are used, accuracy climbs even higher: sensitivity reaches 99% and specificity 97%.
Low-dose CT, which reduces your radiation exposure, performs slightly lower but still well, with sensitivity around 93% and specificity around 94%. Some hospitals use non-contrast CT to speed up the process, though its sensitivity drops to roughly 88%. In practice, the decision about contrast and dose depends on your age, kidney function, and how clear the clinical picture already is.
On the scan, radiologists look for a swollen appendix, surrounding fat inflammation, and sometimes a small calcified stone blocking the appendix opening. These findings, combined with your exam and blood work, give a high degree of certainty.
Ultrasound for Children and Young Adults
For children and teenagers, ultrasound is typically the first imaging choice because it avoids radiation entirely. The radiologist or technician presses a probe over the right lower abdomen and measures the appendix. A normal appendix is 6 millimeters or less in diameter. Anything larger is considered abnormal and suspicious for appendicitis.
Ultrasound done at the bedside by emergency physicians (sometimes called point-of-care ultrasound) has an overall sensitivity of about 91% and specificity of 97%. When performed specifically by emergency doctors rather than ultrasound specialists, sensitivity drops to around 80% with specificity of 92%. That gap means a negative bedside ultrasound in a child who still looks clinically suspicious often leads to a follow-up CT or, increasingly, an MRI.
MRI During Pregnancy
Pregnant patients present a unique challenge. The growing uterus shifts the appendix out of its usual position, making physical exam findings less reliable. Ultrasound is still the first test, but it frequently fails to visualize the appendix clearly during pregnancy.
When ultrasound is inconclusive, MRI is the next step. It uses no radiation, making it safe for the fetus. In one study, MRI caught 100% of confirmed appendicitis cases in pregnant patients, with specificity between 96% and 98% depending on the radiologist reading the images. The American College of Radiology now supports MRI as the preferred follow-up after inconclusive ultrasound in pregnancy, and some researchers argue it should be the first imaging test in this population.
Conditions That Mimic Appendicitis
Part of the testing process is ruling out other problems that cause similar right-sided abdominal pain. The most common mimics include inflammatory bowel disease (such as Crohn’s disease flares), kidney stones lodged in the right ureter, kidney infections, and swollen lymph nodes in the abdomen (mesenteric adenitis, which is especially common in children after a viral illness). In some parts of the world, tuberculosis affecting the intestines can also look nearly identical on imaging.
This is one reason doctors rely on the full combination of exam, labs, and imaging rather than any single test. A CT scan that shows a normal appendix but an inflamed bowel or a kidney stone changes the treatment plan entirely, and saves you from an unnecessary surgery.