Appendicitis frequently begins as an ache around the navel (belly button) that gradually shifts to the lower right abdomen. The pain may become worse as the inflammation spreads to the tissues surrounding the abdomen, such as the peritoneum, or inner lining of the abdomen.

In many cases, the pain eventually settles in an area of the body known as McBurney point, which is halfway between the navel and the top of the right pelvic bone. However, the exact location of the pain will depend on the location of the person’s appendix, which can vary. Wherever the pain settles, the region tends to feel tender when even gentle pressure is applied. If this pressure is released quickly, the pain may worsen. This condition is known as rebound tenderness. Coughing, sneezing, walking, taking deep breaths or performing other jarring movements can also worsen the pain, especially if the appendix is touching the peritoneum.

Other symptoms that may occur with appendicitis include:

• Nausea and vomiting
• Loss of appetite
• Low-grade fever
• Constipation
• Inability to pass gas
• Diarrhea
• Abdominal swelling
• Frequent need to urinate

Appendicitis that is not treated promptly may result in a rupture of the appendix. Initially, this perforation may cause the patient to feel better as the pressure is released. However, a burst appendix allows infectious organisms and the contents of the intestines to rush into the peritoneal cavity. This can cause an extremely dangerous infection of the abdominal-cavity lining known as peritonitis.

If the cavity becomes infected, the patient’s abdomen may become distended with gas and fluid and will likely feel tight, hard and tender to the touch. Widespread abdominal pain (unlike the localized pain of appendicitis) may result, and the patient may find it impossible to pass gas or have a bowel movement. Worsening pain and fever, excessive thirst, and reduced urine output are also associated with peritonitis. Young children with peritonitis may become disoriented or lose  consciousness and pass out if they are not treated promptly. Peritonitis is an emergency situation that requires immediate medical care.

The combination of infection and released intestinal contents can also form an abscess, a walled-off area of infection outside the intestine. Such abscesses may range in size from a walnut to a grapefruit, and are usually removed surgically.

Ruptures can also infect a woman’s ovaries and fallopian tubes, causing infertility. If bacteria from a rupture enter the bloodstream, a life-threatening condition called sepsis may result.

Although many patients experience symptoms commonly associated with appendicitis, others do not. Women who are pregnant often do not experience classic symptoms of appendicitis because of the changes an expanding uterus causes in the abdominal cavity. Therefore, pregnant women should consult a physician if they experience pain on the right side of the abdomen, particularly during their third trimester. Elderly patients also are less likely to experience fever or severe abdominal pain than younger adults. As a result, they should contact a physician if they have even slight fever and abdominal pain on their right side.

In addition, people with certain conditions may not feel symptoms and may instead experience a general feeling of sickness. Such conditions include obesity, cancer, diabetes and HIV infection. People who are undergoing immunosuppressive therapy or who have received a transplanted organ also may not experience specific symptoms.