Appendicitis is a condition in which your appendix becomes inflamed and fills with pus. Your appendix is a finger-shaped pouch that projects out from your colon on the lower right side of your abdomen. This small structure has no known essential purpose, but that doesn’t mean it can’t cause problems.

Appendicitis causes pain that typically begins around your navel and then shifts to your lower right abdomen. Appendicitis pain typically increases over a period of 12 to 18 hours and eventually becomes very severe.

Appendicitis can affect anyone, but it most often occurs in people between the ages of 10 and 30. The standard appendicitis treatment is surgical removal of the appendix.

Signs and symptoms of appendicitis may include:

• Aching pain that begins around your navel and often shifts to your lower right abdomen
• Pain that becomes sharper over several hours
• Tenderness that occurs when you apply pressure to your lower right abdomen
• Sharp pain in your lower right abdomen that occurs when the area is pressed on and then the pressure is quickly released (rebound tenderness)
• Pain that worsens if you cough, walk or make other jarring movements
• Nausea
• Vomiting
• Loss of appetite
• Low-grade fever
• Constipation
• Inability to pass gas
• Diarrhea
• Abdominal swelling

The location of your pain may vary, depending on your age and the position of your appendix. Young children or pregnant women, especially, may have appendicitis pain in different places.

The cause of appendicitis isn’t always clear. Sometimes appendicitis can occur as a result of:

• An obstruction. Food waste or a hard piece of stool (fecal stone) can block the opening of the cavity that runs the length of your appendix.
• An infection. Appendicitis may also follow an infection, such as a gastrointestinal viral infection, or it may result from other types of inflammation.

In both cases, bacteria inside the appendix multiply rapidly, causing the appendix to become inflamed, swollen and filled with pus. If not treated promptly, the appendix can rupture.

Appendicitis can cause serious complications, such as:

• A ruptured appendix. If your appendix ruptures, the contents of your intestines and infectious organisms can leak into your abdominal cavity. This can cause an infection of your abdominal cavity (peritonitis).
• A pocket of pus that forms in the abdomen. If your appendix has burst, infection and the seepage of intestinal contents may form an abscess — a pocket of infection (appendiceal abscess) around the appendix. Appendiceal abscess requires treatment before the abscess tears, causing a more widespread infection of the abdominal cavity.

The pain from appendicitis may change over time, so establishing a diagnosis can sometimes be difficult. In addition, abdominal pain can arise from a number of health problems other than appendicitis. To help diagnose appendicitis, your doctor will likely take a history of your signs and symptoms and perform a thorough physical examination of your abdomen.

Tests and procedures used to diagnose appendicitis include:

• Physical exam to assess your pain. Your doctor may apply gentle pressure on the painful area. When the pressure is suddenly released, appendicitis pain will often feel worse, signaling that the adjacent peritoneum is inflamed. Other signs your doctor may watch for include abdominal rigidity and a tendency to stiffen your abdominal muscles in response to pressure over the inflamed appendix (guarding).
• Blood test. This allows your doctor to check for a high white blood cell count, which may indicate an infection.
• Urine test. Your doctor may want you to have a urinalysis to make sure that a urinary tract infection or a kidney stone isn’t causing your pain. If it is a kidney stone, red blood cells are usually seen during microscopic examination of the urine.
• Imaging tests. Your doctor may also recommend an abdominal X-ray, an ultrasound scan or a computerized tomography (CT) scan to help confirm appendicitis or find other causes for your pain.

Appendicitis treatment usually involves surgery to remove the inflamed appendix. Other treatments may be necessary depending on your situation.

Appendectomy can be performed as open surgery using one abdominal incision that’s about 2 to 4 inches (5 to 10 centimeters) long. Or appendicitis surgery can be done as a laparoscopic operation, which involves a few small abdominal incisions. During a laparoscopic appendectomy, the surgeon inserts special surgical tools and a video camera into your abdomen to remove your appendix.

In general, laparoscopic surgery allows you to recover faster and heal with less scarring. But laparoscopic surgery isn’t appropriate for everyone. If your appendix has ruptured and infection has spread beyond the appendix or if an abscess is present, you may require an open appendectomy. An open appendectomy allows your surgeon to clean the abdominal cavity.

Expect to spend one or two days in the hospital after your appendectomy.

If your appendix has burst and an abscess has formed around it, the abscess may be drained by placing a tube through your skin and into the abscess. Appendectomy can be performed several weeks later after the infection is under control.

Expect a few weeks of recovery from an appendectomy. If your appendix burst, it may take longer to recover. During this recovery time, you can take steps to help your body heal, such as:

• Avoid strenuous activity at first. If your appendectomy was done laparoscopically, limit your activity for the first three to five days after surgery. If you had an open appendectomy, limit your activity for the first 10 to 14 days after surgery. Ask your doctor when you can go back to your normal activity.
• Support your abdomen when you cough. You may feel abdominal pain when you cough, laugh or make other movements. Place a pillow over your abdomen and apply pressure before these movements to brace yourself.
• Call your doctor if your pain medications aren’t helping.Being in pain puts extra stress on your body and slows the healing process. If you’re still in pain despite your pain medications, call your doctor.
• Get up and move when you’re ready. Start slowly and increase your activity as you feel up to it. Start with short walks.
• Sleep when you feel tired. As your body heals, you may find you feel sleepier than usual. Take it easy and rest when you need to.
• Discuss returning to work or school with your doctor. You can return to work when you feel up to it. Children may be able to return to school less than a week after surgery, though strenuous activity, such as gym class or sports, should be limited for two to four weeks after surgery.