Acute appendicitis is a sudden inflammation of the appendix, a small finger-shaped pouch attached to the large intestine in your lower right abdomen. It’s the most common abdominal emergency requiring surgery, and it develops when the opening of the appendix becomes blocked, trapping bacteria inside and triggering a rapid infection. Without treatment, the appendix can rupture within 48 to 72 hours, spreading infection into the abdominal cavity.
What Causes the Appendix to Inflame
Obstruction of the appendix’s narrow opening is the primary trigger. The blockage is most often caused by a fecalith (a small, hardened piece of stool), normal stool, or swelling of the lymph tissue that lines the appendix wall. Lymphoid hyperplasia, where immune tissue inside the appendix enlarges in response to an infection elsewhere in the body, is especially common in children and teenagers.
Once the opening is sealed off, mucus continues to be produced inside with nowhere to go. The appendix swells, pressure builds, and blood flow to the wall decreases. Bacteria that normally live harmlessly inside the appendix begin to multiply and invade the weakened tissue. This cascade from blockage to swelling to infection is what makes the condition “acute,” meaning it comes on fast and escalates quickly.
Who Gets It
Acute appendicitis is most common between the ages of 10 and 19, though it can happen at any age. Roughly 11 in every 10,000 people will experience it in their lifetime. Males have a slightly higher incidence than females. In very young children and older adults, appendicitis can be harder to recognize because the symptoms sometimes present differently, which can delay diagnosis.
How the Pain Typically Progresses
The hallmark of appendicitis is pain that starts in one place and moves to another. Most people first notice a dull, vague ache around the belly button. This happens because the swollen appendix initially irritates nerves that relay sensation from the gut to the central abdomen. Over the next 12 to 18 hours, the inflammation spreads to the outer wall of the appendix and the surrounding abdominal lining, and the pain shifts to the right lower quadrant of the abdomen, becoming sharper and more constant.
Other common symptoms include loss of appetite (often one of the earliest signs), nausea or vomiting that starts after the pain begins, a low-grade fever, and an inability to pass gas. The pain typically worsens with movement, coughing, or sneezing. If the appendix ruptures, the pain may briefly improve before spreading across the entire abdomen as infection moves into the abdominal cavity.
What Happens During a Physical Exam
Doctors use several specific maneuvers to check for signs of appendicitis. The single most important finding is localized tenderness or guarding when the right lower quadrant is pressed, known as the McBurney sign. Other tests involve repositioning your right leg in specific ways to see if certain movements provoke pain. Extending the right thigh backward tests whether the appendix is inflamed behind the colon. Rotating the right thigh inward checks for a pelvic-positioned appendix.
Pressing on the left side of the abdomen and feeling pain on the right side is another telling sign, because the pressure shifts intestinal contents toward the inflamed appendix. Increased pain when you cough also suggests the abdominal lining is irritated. Rebound tenderness, where the pain spikes when pressure is released rather than applied, points to peritoneal inflammation.
How Appendicitis Is Confirmed
A CT scan is the most accurate imaging tool for diagnosing acute appendicitis in adults, with a sensitivity of about 97% and specificity of about 96%. That means it catches nearly all true cases while rarely producing false alarms. CT scans using both intravenous and oral contrast perform best, with sensitivity reaching 99%. Even low-dose CT scans, which use less radiation, still detect appendicitis accurately around 93% of the time.
Ultrasound is the preferred first choice for children and pregnant women because it avoids radiation exposure entirely. Its sensitivity is lower, around 82%, and specificity is about 86%, so a negative ultrasound doesn’t always rule appendicitis out. In those cases, a follow-up CT or MRI may be needed. Blood tests showing elevated white blood cell counts support the diagnosis but aren’t definitive on their own.
Surgery vs. Antibiotics
Surgical removal of the appendix (appendectomy) remains the standard treatment and has a success rate of 99.6%. Most appendectomies today are performed laparoscopically, using a few small incisions rather than one large one, which significantly reduces recovery time and scarring.
For uncomplicated cases where the appendix hasn’t ruptured, antibiotic treatment alone is an option some patients and surgeons consider. In a major clinical trial, about 73% of patients treated with antibiotics alone avoided surgery within the first year. However, roughly 27% ended up needing an appendectomy within that same year due to recurrent appendicitis. This means antibiotics can work as a bridge or an alternative for select patients, but the condition comes back in about one out of four people.
If the appendix has already ruptured or an abscess has formed, the approach changes. Ruptured cases often require open surgery with a larger incision, and recovery is longer because the infection has spread beyond the appendix itself.
What Recovery Looks Like
After a laparoscopic appendectomy, most people go home the same day or the next morning. The small incisions can be gently washed with warm soapy water 24 to 48 hours after surgery. If adhesive strips were placed over the incisions, they’re left in place until they fall off on their own. Open surgery incisions may have staples that are removed 7 to 10 days later.
For about two weeks after surgery, you should avoid lifting anything heavy, including children, large grocery bags, and heavy backpacks. Strenuous exercise like jogging, weight lifting, and cycling is also off limits during this period. Most people return to desk work or school within a week after laparoscopic surgery, though physically demanding jobs take longer.
If the appendix ruptured before removal, recovery is more involved. The incision may be packed with gauze that needs to be changed regularly, and a course of intravenous antibiotics in the hospital is typical before discharge. Full recovery from a ruptured appendix can take several weeks rather than the one to two weeks expected after an uncomplicated case.