Acute appendicitis is an inflammation of the appendix that requires prompt medical attention, often involving surgical removal. The classic presentation typically begins with a vague, dull discomfort localized around the belly button or upper abdomen. As the inflammation progresses, the pain generally migrates and intensifies, settling sharply in the lower right side of the abdomen, usually within 12 to 24 hours. Many other conditions can cause pain in this region, leading to a high rate of misdiagnosis.
Gastrointestinal Conditions That Mimic Symptoms
Acute gastroenteritis, often called the stomach flu, is a frequent culprit because it shares symptoms like nausea, vomiting, abdominal discomfort, and sometimes a low-grade fever. With gastroenteritis, the pain is typically diffuse and generalized, and significant diarrhea or vomiting often precedes the onset of pain. Appendicitis pain, in contrast, is localized to the lower right quadrant, and any vomiting generally follows the start of the abdominal pain.
Diverticulitis involves inflammation of small pouches, known as diverticula, that form in the wall of the colon. While it most commonly affects the left side, right-sided colonic diverticulitis can cause pain directly in the lower right abdominal quadrant, mimicking appendicitis. A key difference is that patients with right-sided diverticulitis are less likely to report the prodromal symptoms, such as loss of appetite, nausea, and vomiting, that are predictive of appendicitis.
Mesenteric adenitis, an inflammation of the lymph nodes in the abdomen, is a frequent cause of misdiagnosis, particularly in children. This condition is usually triggered by a recent viral infection, which causes the abdominal lymph nodes to swell. The resulting pain can be felt around the navel or shift to the lower right side, closely mirroring the pattern of appendicitis. Unlike appendicitis, mesenteric adenitis is generally a self-limiting condition that resolves without intervention, though imaging is often required to rule out an inflamed appendix.
Conditions Related to the Urinary Tract
Kidney stones, or renal colic, cause intense, sharp pain that can be felt in the flank or back but often radiates forward into the abdomen and groin area. This pain is characteristically described as coming in waves or spasms as the stone moves through the ureter.
The presence of other symptoms can help distinguish a kidney stone from appendicitis, such as blood in the urine, a frequent urge to urinate, or a burning sensation during urination. Kidney stone pain rarely follows the classic migratory pattern of appendicitis, instead remaining deep in the flank or radiating downward.
A urinary tract infection (UTI) or a more severe kidney infection, known as pyelonephritis, can also present with lower abdominal pain and fever. If the infection involves the right kidney, the associated flank pain may be felt in the same general area as the appendix. Distinguishing features of pyelonephritis include high fever, chills, and pain that is more pronounced in the back or side, often accompanied by specific urinary symptoms.
Differential Diagnoses Specific to Women
A range of gynecological and obstetric conditions can cause acute pain in the lower abdomen that is almost identical to appendicitis. Ectopic pregnancy, where a fertilized egg implants outside the uterus, is a life-threatening emergency that must be ruled out immediately. Symptoms often include one-sided abdominal or pelvic pain and vaginal bleeding. If the tube ruptures, the pain can become sudden and severe, leading to signs of internal hemorrhage such as fainting or shoulder pain.
Ovarian torsion occurs when an ovary twists around the ligaments that support it, cutting off its blood supply. It presents with sudden, severe lower abdominal pain, often accompanied by nausea and vomiting. Because the pain can be localized to the right side, it is frequently confused with appendicitis, but the pain of torsion is typically more abrupt in onset.
Pelvic inflammatory disease (PID), an infection of the female reproductive organs, is another common mimic that can cause lower abdominal pain, often in the lower right quadrant. Unlike the pain of appendicitis, PID pain is often less severe, may be bilateral, and can persist for weeks. A medical history that includes an abnormal vaginal discharge, tenderness of the cervix upon examination, or a history of prior PID can help point toward this diagnosis.
When Symptoms Require Immediate Medical Attention
Certain combinations of symptoms signal a medical emergency that requires immediate attention. Sudden, rapidly escalating abdominal pain that is intolerable, especially if it wakes a person from sleep, warrants urgent care. Any pain accompanied by signs of severe infection or peritonitis, which is inflammation of the abdominal lining, should be evaluated immediately.
Signs of peritonitis include a rigid, board-like hardness of the abdominal muscles, known as guarding, and severe pain upon the sudden release of pressure, called rebound tenderness. A high fever, above 100.4°F (38°C), combined with persistent vomiting or an inability to keep fluids down are also red flags. If the pain suddenly disappears after being severe, this may indicate a rupture of the inflamed organ, which can lead to shock, characterized by a fast heart rate, low blood pressure, and confusion.