Appendicitis
Appendicitis is inflammation of the appendix, a small fingerlike pouch attached to the beginning of the large intestine (colon) in the right lower abdomen. It is one of the most common causes of severe abdominal pain requiring surgery and can affect people of any age, though it is most common in older children and young adults. Appendicitis typically develops when the appendix becomes blocked, allowing bacteria to multiply and inflammation to progress. If untreated, an inflamed appendix can rupture (perforate), leading to serious infection within the abdomen. Symptoms typically develop over hours to a day or two and include abdominal pain, nausea, and low-grade fever. Prompt evaluation is important because appendicitis is a time-sensitive diagnosis, and treatment—typically surgery, and in selected cases antibiotics alone—should be started promptly.
What is it?
The appendix is a narrow, fingerlike pouch that projects from the cecum, the first portion of the large intestine (colon) in the right lower abdomen. In adults, the appendix is typically 6 to 10 centimeters long and about 5 to 10 millimeters in diameter. It has lymphoid tissue in its wall and may play a role in immune function and the maintenance of gut bacteria, though people can live entirely normally without an appendix.
Appendicitis is inflammation of the appendix. It typically develops when the appendix’s small opening (lumen) becomes blocked, allowing bacteria that normally live in the intestine to multiply and inflammation to progress. Common causes of blockage include hardened stool material (fecalith), enlarged lymphoid tissue in the wall of the appendix (particularly in children and young adults), and, less commonly, foreign bodies, parasites, or tumors. As inflammation progresses, pressure inside the appendix increases, blood flow to the wall of the appendix decreases, bacteria can invade the wall, and, if untreated, the appendix wall can weaken and rupture. Rupture releases infected material into the abdominal cavity and can lead to abscess formation, generalized inflammation of the abdominal lining (peritonitis), and severe illness.
Appendicitis is broadly categorized as uncomplicated or complicated. Uncomplicated appendicitis is inflammation without rupture, abscess, or gangrene of the appendix and typically presents at a relatively early stage. Complicated appendicitis includes rupture with abscess formation, gangrene of the appendix, generalized peritonitis, or other complications, and typically presents at a later stage or in patients with delayed diagnosis.
Appendicitis can affect people of any age but is most common between ages 10 and 30. The lifetime risk is roughly 7–9% in the general population, making it one of the most common conditions requiring urgent abdominal surgery. It is slightly more common in males. Incidence has decreased somewhat in developed countries over recent decades, though the reasons for this are not entirely clear.
Symptoms of appendicitis typically develop over hours to a day or two. The classic presentation involves a specific sequence of symptoms. Abdominal pain typically begins around the belly button (periumbilical or central abdominal pain) and is often described as vague, crampy, or dull. Over hours (typically 6 to 24 hours), the pain shifts to the right lower abdomen and becomes more localized, sharper, and more constant. This pain is caused by inflammation involving the outer lining of the appendix, which is more sensitive to precise localization than the inner appendix tissue. The location of maximal tenderness is often at a specific point called McBurney’s point, located about one-third of the way from the top of the right hip bone (the anterior superior iliac spine) to the belly button.
Other common symptoms include loss of appetite (which is present in the majority of patients), nausea and vomiting (usually developing after the abdominal pain), low-grade fever (typically 99–101°F or 37–38°C, though higher fevers can occur, particularly with rupture), and worsening of pain with movement, coughing, or bumps in the road (indicating inflammation of the outer lining of the abdomen).
Presentation can be atypical in specific groups. In young children, symptoms may be less specific, and children may present with generalized abdominal pain, irritability, refusal to eat, or vomiting. In older adults, symptoms are often less pronounced and may include vague abdominal pain, low-grade fever, and, in some cases, presentation only when rupture has already occurred. In pregnant patients, the growing uterus can displace the appendix upward, causing pain in atypical locations (higher in the abdomen or on the right side). Because presentation can be atypical in these groups, the diagnosis is often more challenging and, historically, has been associated with higher rates of delayed diagnosis and complications.
The physical examination typically shows tenderness in the right lower abdomen, often maximally at McBurney’s point. Additional findings may include rebound tenderness (worsened pain when the examiner releases pressure), guarding (involuntary tightening of the abdominal muscles), and, when peritonitis has developed, generalized tenderness. Several classic physical examination signs may support the diagnosis, including Rovsing’s sign (pain in the right lower abdomen when pressure is applied to the left lower abdomen), the psoas sign (pain with extension of the right hip, suggesting inflammation near the psoas muscle), and the obturator sign (pain with internal rotation of the right hip). However, these signs are neither highly sensitive nor specific.
Laboratory testing typically shows elevated white blood cell count (usually mildly elevated in early appendicitis and more significantly elevated with progression or rupture) and elevated inflammatory markers such as C-reactive protein (CRP). Blood tests may also identify signs of dehydration or, in more severe cases, signs of infection spread. Urinalysis is often performed to help exclude urinary tract causes of abdominal pain but may show minor changes in appendicitis.
Imaging plays a central role in diagnosis in most modern practice. CT of the abdomen and pelvis with intravenous contrast is highly accurate for appendicitis, with sensitivity and specificity both above 90% in most studies. On CT, findings suggestive of appendicitis include an enlarged appendix (typically greater than about 6–7 mm in diameter), thickening of the appendix wall, inflammatory changes in the surrounding fat, and, in complicated cases, findings of rupture such as free air, abscess, or peritonitis. CT can also identify alternative diagnoses.
Ultrasound is often the first-line imaging test in children and pregnant patients to avoid the radiation exposure of CT. Ultrasound is highly operator-dependent, and its sensitivity is lower than CT in some settings. It typically shows an enlarged, non-compressible appendix with wall thickening and, sometimes, associated fluid or inflammation.
MRI is used in specific circumstances, particularly in pregnancy, and provides excellent evaluation of the appendix without ionizing radiation. It is not always readily available, particularly on an urgent basis.
Clinical scoring systems (such as the Alvarado score and the pediatric appendicitis score) combine symptoms, examination findings, and laboratory results to estimate the likelihood of appendicitis and can help guide the need for imaging. They are useful adjuncts but do not replace clinical judgment or imaging when needed.
Several conditions can mimic appendicitis and should be considered during evaluation. These include mesenteric adenitis (particularly in children), gastroenteritis, ovarian pathology (such as ovarian cyst rupture or torsion) in women, ectopic pregnancy in women of reproductive age, Meckel’s diverticulitis, kidney stones or other urinary tract conditions, inflammatory bowel disease (particularly Crohn’s disease affecting the terminal ileum), and other conditions.
Important to Know
Management of appendicitis has traditionally involved surgical removal of the appendix (appendectomy), though the field has evolved in recent years to include antibiotic-only treatment for selected patients with uncomplicated appendicitis. Care is typically coordinated by emergency medicine clinicians (in initial evaluation), general surgeons, and, when needed, gastroenterologists, radiologists, obstetricians (in pregnancy), and pediatric specialists (in children).
Appendectomy (surgical removal of the appendix) remains the most common treatment for appendicitis. It is typically performed using laparoscopic or robotic-assisted techniques through several small incisions rather than a single larger open incision, which offers advantages including less pain, shorter hospital stay, faster return to normal activities, and reduced risk of some complications compared with open surgery. Open appendectomy is used in specific circumstances, such as with certain complications or when laparoscopic surgery is not feasible.
Antibiotic-only treatment (without appendectomy) has emerged as an alternative for selected patients with uncomplicated appendicitis based on evidence from clinical trials. This approach involves treatment with antibiotics for a period of days, either as an inpatient (with intravenous antibiotics initially) or as an outpatient in some settings. Studies have shown that a proportion of patients treated with antibiotics alone can avoid surgery, at least in the short term, though a notable proportion (roughly 30–40% or more within a year in various studies) eventually develop recurrent appendicitis or require surgery. The choice between surgery and antibiotic-only treatment is individualized and involves shared decision-making, considering patient preferences, comorbidities, and specific clinical features. Antibiotic-only treatment is generally not appropriate for complicated appendicitis (with abscess, perforation, or peritonitis) or for patients with specific features (such as an appendicolith, which is associated with higher failure rates).
For patients with complicated appendicitis (particularly with abscess formation), management may involve initial percutaneous drainage of the abscess by an interventional radiologist, along with intravenous antibiotics, and delayed appendectomy several weeks later once the acute inflammation has resolved (called interval appendectomy). This approach can be less morbid than emergency surgery in the presence of extensive inflammation. Whether interval appendectomy is always necessary after successful drainage is an area of ongoing discussion, with some patients doing well without it.
For patients with generalized peritonitis or severe illness, urgent surgery is generally needed, along with resuscitation and antibiotics.
Antibiotic choice for appendicitis is guided by likely organisms (typically enteric gram-negative bacteria and anaerobes) and local resistance patterns. Common regimens include cephalosporins with metronidazole, or newer broader-spectrum agents. Antibiotic duration is guided by clinical response and the specific circumstances (typically shorter for uncomplicated cases and longer for complicated cases).
Care during pregnancy in patients with appendicitis requires special attention because of the potential impact on both mother and fetus. Diagnosis can be more challenging due to the atypical presentation. Treatment is typically surgical, and laparoscopic appendectomy is often used, particularly in the first and second trimesters, though open appendectomy may be preferred in some cases. Coordination with obstetrics and, when appropriate, maternal-fetal medicine is important. MRI is often preferred for diagnostic imaging to avoid radiation.
Care of children with appendicitis is typically coordinated by pediatric surgeons or general surgeons with pediatric experience. Presentation can be more variable in young children, and complications (such as rupture) are more common at the time of diagnosis. Laparoscopic appendectomy is the standard surgical approach in most centers.
For patients with unusual or atypical presentations, additional evaluation may be needed to distinguish appendicitis from other conditions.
For patients with a normal-appearing appendix on imaging or at surgery, evaluation for alternative diagnoses is important. In some cases of laparoscopic exploration for suspected appendicitis, a normal appendix is removed (incidental appendectomy) to prevent future confusion.
Recovery after appendectomy is generally good, particularly for uncomplicated cases. Most patients return to normal activities within a few days to weeks, depending on the complexity of the surgery and any complications. Complications of appendectomy are uncommon but can include wound infection, bleeding, and, less commonly, injury to nearby structures or intra-abdominal complications.
Following successful treatment of appendicitis, most patients require no long-term follow-up related specifically to the appendicitis, though standard postoperative follow-up is typical.
Care is typically coordinated by emergency medicine clinicians, surgeons, and, when needed, other specialists. Imaging and clinical findings are interpreted alongside the patient’s symptoms, examination, past medical history, and broader clinical context rather than in isolation.
Patient education plays an important role, particularly around understanding when to seek urgent medical evaluation for possible appendicitis (such as new severe abdominal pain), recognizing the classic pattern of symptoms, understanding the treatment plan and its rationale, and, when relevant, understanding the options and tradeoffs between surgical and antibiotic-only treatment.
Red flag symptoms include severe abdominal pain that is worsening or spreading, high fever with chills, signs of sepsis (severe illness, low blood pressure, rapid heart rate, confusion), significant vomiting (particularly with blood or bile-stained material), abdominal distension, inability to pass gas or stool, generalized abdominal tenderness, difficulty breathing, or rapid clinical deterioration. These warrant immediate emergency evaluation, as they may indicate rupture, peritonitis, sepsis, or other serious complications.