Appendicitis, Acute

Descriptive text is not available for this image Basics

Description

  • Acute inflammation of the appendix
  • Simple or uncomplicated appendicitis occurs when there is no clinical or radiologic sign of perforation. Complicated or perforated appendicitis is defined by a palpable mass and phlegmon, perforation, or abscess on imaging.
  • Arising from the base of the cecum in right lower quadrant (RLQ), the appendix can be anterior, posterior, medial, or lateral to the cecum as well as in the pelvis. Vascular supply provided by appendicular artery, a branch of the ileocolic artery; nerve supply derived from the superior mesenteric plexus
  • Most common cause of acute surgical abdomen worldwide

Epidemiology

  • Predominant age: 10 to 30 years; rare in infancy; although uncommon, can be more challenging to diagnose in elderly
  • Predominant sex: slight male predominance
    • Ages 10 to 30 years: male > female (3:2)
    • Peak incidence in 2nd and 3rd decade of life
    • Age >30 years: men = women

Incidence

  • 1 case per 1,000 people per year
  • Lifetime incidence 1 in every 15 people (7–8%)

Pregnancy Considerations

  • Most common extrauterine surgical emergency
  • Incidence similar in pregnancy
  • Higher rate of perforation; more likely to present with peritonitis

Etiology and Pathophysiology

Obstruction of the appendiceal lumen is thought to lead to distention, ischemia, and bacterial overgrowth. Without intervention, appendicitis can lead to perforation and subsequent abscess formation or generalized peritonitis. Causes of obstruction:

  • Fecaliths (most common)
  • Lymphoid tissue hyperplasia (in children)
  • Vegetables, fruit seeds, and other foreign bodies
  • Intestinal worms (ascarids)
  • Strictures, fibrosis, neoplasms

Genetics

First-degree relative with history of appendicitis increases risk; no direct genetic link found.

Risk Factors

Male adolescents, familial tendency, intra-abdominal tumors

Descriptive text is not available for this image Diagnosis

  • Diagnosis relies on history and physical examination with supporting laboratory studies and imaging.
  • Multiple scoring systems are available to quantify a clinician’s gestalt for acute appendicitis. Traditionally, the modified Alvarado scoring system (sensitivity 89%, specificity 71%) has been used, but currently, the Raja Isteri Pengiran Anak Saleha Appendicitis (RIPASA) scoring system appears to be more effective (sensitivity 96%, specificity 86%) (1)[A].
  • RIPASA scoring system
    • Patient demographics
      • Sex: men (1 point), women (0.5 point)
      • Age: <40 years (1 point), >40 years (0.5 point)
    • Symptoms
      • Right iliac fossa pain (0.5 point)
      • Migration of pain to RLQ (0.5 point)
      • Anorexia (1 point)
      • Nausea and vomiting (1 point)
      • Duration of symptoms: <48 hours (1 point), >48 hours (0.5 point)
    • Signs
      • Right iliac fossa tenderness (1 point)
      • Right iliac fossa guarding (2 points)
      • Rebound tenderness (1 point)
      • Rovsing sign (2 points)
      • Fever >37°C (2 points)
    • Investigations
      • Elevated WBCs (1 point)
      • Negative urinalysis (1 point)
    • Additional criterion: not a Singapore national (1 point)
      • Because it was developed in Singapore, which has many foreign nationals, the “foreign national registration identity card” was included in the score as it was found to have some predictive capacity. This is harder to apply to other populations.
  • RIPASA score >7.5 is very accurate for the diagnosis of acute appendicitis.
  • Pediatric appendicitis score—helps predict the likelihood of acute appendicitis (diagnosis is still clinical).

History

  • Classic history is vague periumbilical pain, followed by anorexia, nausea, and vomiting. Over the next 4 to 48 hours, pain migrates to the RLQ.
  • Only 50% of patients present with a classic history.
  • Pain before vomiting (~100% sensitive), abdominal pain (~100%), pain migration (50%)
  • Anorexia (~100%), nausea (90%), vomiting (75%), obstipation
  • Atypical symptoms and pain suggest a retrocecal or pelvic appendix.

Physical Exam

  • Fever; temperature >100.4°F (may be absent); tachycardia
  • RLQ tenderness; maximal tenderness at McBurney point (1/3 the distance from the anterior superior iliac spine to the umbilicus)
  • Voluntary and involuntary guarding
  • Rovsing sign: RLQ pain with palpation of left lower quadrant
  • Psoas sign: pain with right thigh extension (retrocecal appendix)
  • Obturator sign: pain with internal rotation of flexed right thigh (pelvic appendix); local and suprapubic pain on rectal exam (pelvic appendix)
  • Pelvic and rectal exams are helpful to assess other causes of lower abdominal pain (e.g., pelvic inflammatory disease, prostatitis).
  • Serial exams can be useful in indeterminate cases.

Differential Diagnosis

  • GI
    • Gastroenteritis, inflammatory bowel disease
    • Diverticulitis, ileitis
    • Cholecystitis, pancreatitis
    • Intussusception, volvulus
  • Gynecologic
    • Pelvic inflammatory disease, ectopic pregnancy
    • Ovarian cyst, ovarian torsion, tubo-ovarian abscess
    • Endometriosis
    • Ruptured graafian follicle
  • Urologic
    • Testicular torsion, epididymitis
    • Kidney stones, prostatitis, cystitis, pyelonephritis
  • Systemic: Diabetic ketoacidosis, Henoch-Schönlein purpura, sickle cell crisis, porphyria
  • Other
    • Acute mesenteric lymphadenitis
    • No organic pathologic condition
    • Hernias
    • Psoas abscess
    • Rectus sheath hematoma
    • Epiploic appendagitis
    • Pneumonia (basilar)

Pediatric Considerations

  • Decreased diagnostic accuracy of history and physical exam
  • Higher fever; more vomiting and diarrhea

Pregnancy Considerations

  • Appendicitis is more difficult to diagnose in pregnancy.
  • Normal inflammatory response is suppressed.
  • Appendix displaced out of pelvis by gravid uterus

Geriatric Considerations
Decreased diagnostic accuracy, more likely to be an atypical presentation

Diagnostic Tests & Interpretation

Initial Tests (lab, imaging)

  • Leukocytosis: WBC >10,000/mm3 (70%)
  • Polymorphonuclear predominance—“left shift” (>90%)
  • Urinalysis: hematuria, pyuria (30%)
  • Human chorionic gonadotropin (hCG) (If positive, rule out ectopic pregnancy.)
  • C-reactive protein: nonspecific inflammatory marker; when paired with an elevated WBC, increases predictive value for appendicitis
  • Drugs may alter lab results: antibiotics, steroids
  • Imaging if the diagnosis is not clear; helps to detect complications (abscess, perforation)
  • Plain films: minimal utility, nonspecific findings, may visualize fecalith
  • CT scan with contrast: sensitivity 91–98%; specificity 95–99%; imaging modality of choice; consider radiation dose, particularly in young patients.
  • Ultrasound: alternative in pregnancy, children, and women with suspected gynecologic pathology; sensitivity and specificity vary with skill of the ultrasonographer. Increasing use in adult populations, with positive predictive value approaching 100% in some studies; can rule in appendicitis but cannot reliably exclude the diagnosis; an effective strategy is to start with ultrasound and, if negative, obtain a CT scan if suspicion warrants.
  • MRI: increasing use in pregnant patients; may help in patients with contrast allergies and renal failure; limitations include cost, availability, and time required to complete study.
  • Radioisotope-labeled WBC scans: may be used in patients with indeterminate CT scans and suspected appendicitis as an alternative to observation or surgery; limitations include availability and time required to complete the study.

Diagnostic Procedures/Other

  • Exploratory laparotomy/laparoscopy
  • Acceptable appendectomy rates vary based on age and gender and may be higher for females of childbearing age than males.

Test Interpretation

  • Acute appendiceal inflammation, local vascular congestion, obstruction
  • Gangrene, perforation with abscess (15–30%)
  • Fecalith

Descriptive text is not available for this image Treatment

General Measures

  • Surgery (appendectomy) has been the standard of care for acute, uncomplicated appendicitis. Evidence suggests nonoperative management with antibiotics may be noninferior to appendectomy after 30 days, but carries a 29% rate of recurrence with need for appendectomy within 90 days. Surgical treatment of uncomplicated appendicitis has a higher complication-free success rate (82%) than that of antibiotic treatment alone (67%) in both adult and pediatric patients.
  • Generally, surgery is indicated for complicated or perforated appendicitis with abscess formation. For larger drainable abscesses, percutaneous drainage, and antibiotics are recommended.
  • Studies suggest that antibiotic treatment in adults with imaging confirmed acute appendicitis is a safe alternative to surgery and results in 2/3 of patients avoiding appendicectomy during the first year (2)[A].

Medication

First Line

  • Uncomplicated acute appendicitis: perioperative dose of antibiotic: single dose of cefoxitin or ampicillin/sulbactam (Unasyn) or cefazolin plus metronidazole
  • Nonoperative antibiotic of choice: intravenous ertapenem for 2 days followed by 5 days PO levofloxacin and metronidazole (3)[B]
  • Gangrenous or perforating appendicitis
    • Broadened antibiotic coverage for aerobic and anaerobic enteric pathogens
    • Piperacillin and tazobactam (Zosyn) or ticarcillin and clavulanate (Timentin) or a 3rd-generation cephalosporin plus metronidazole are initial options.
    • Adjust dosage and choice of antibiotic based on intraoperative cultures.
    • Continue antibiotics for at least 7 days postoperatively or until patient becomes afebrile with normal WBC count.

Second Line

  • Uncomplicated acute appendicitis: clindamycin plus one of the following: ciprofloxacin, levofloxacin, gentamicin, or aztreonam
  • In the case of acute appendicitis complicated by abscess formation or phlegmon in pediatric patients, some studies show initial conservative management with antibiotics alone to carry fewer risks and complications than emergent appendectomy.
  • Gangrenous or perforated appendicitis: ciprofloxacin or levofloxacin plus metronidazole or monotherapy with a carbapenem (imipenem and cilastatin, meropenem, ertapenem)

Issues for Referral

All cases of appendicitis require emergent surgical consultation.

Additional Therapies

A newer option for the treatment of acute appendicitis is currently being studied—endoscopic retrograde appendicitis therapy (ERAT). Studies thus far indicate high technical and clinical success rates (>99%), with very low rates of complication (0.19%) and a much lower recurrence rate (6.01%) than treatment with antibiotics only.

Surgery/Other Procedures

  • The American College of Surgeons, Society for Surgery of the Alimentary Tract, and others recommend surgery as the treatment of choice.
  • Antibiotic treatment might be used as an alternative in specific patients or if surgery is contraindicated.
  • Nonoperative management with antibiotics with up to a reported 39% recurrence rate at 5 years for uncomplicated acute appendicitis

Admission, Inpatient, and Nursing Considerations

  • Admit all patients with appendicitis.
  • Fluid resuscitation with normal saline (NS) or lactated Ringer (LR) solution
  • Correct fluid and electrolyte deficits.
  • Discharge when tolerating oral intake, return of bowel function, afebrile, normal WBC

Descriptive text is not available for this image Ongoing Care

Follow-up Recommendations

  • Return to work in 1 to 2 weeks is typical following most cases of uncomplicated appendicitis.
  • Restrict activity for 4 to 6 weeks after surgery: no heavy lifting (>10 lb) or strenuous physical activity.
  • If managed nonoperatively and patient is >40 years, consider colonoscopy to rule out malignancy.

Patient Education

Postoperative warning signs:

  • Anorexia, nausea, vomiting
  • Abdominal pain, fever, chills
  • Signs/symptoms of wound infection

Prognosis

  • Generally uncomplicated course in young adults with unruptured appendicitis
  • Extremes of age and appendiceal rupture increase morbidity and mortality.
  • Morbidity rates
    • Nonperforated appendicitis: 3%
    • Perforated appendicitis: 47%
  • Mortality rates
    • Unruptured appendicitis: 0.1%
    • Ruptured appendicitis: 3%
    • Patients >60 years of age make up 50% of total deaths from appendicitis.
    • Older patients with ruptured appendix: 15%

Pediatric Considerations

  • Rupture earlier
  • Rupture rate: 15–60%

Pregnancy Considerations

  • Rupture rate: 40%
  • Fetal mortality rate: 2–8.5%

Geriatric Considerations
Rupture rate: 67–90%

Complications

  • Intestinal fistulas
  • Intestinal obstruction, paralytic ileus, incisional hernia
  • Liver abscess (rare), pylephlebitis
  • Stump appendicitis: recurrence of appendicitis at appendiceal stump after appendectomy

Authors

Grant Wei, MD, FACEP
Rohail Khan, MD
Chirag N. Shah, MD

References

  1. Alvarez-Lozada LA, Fernandez-Reyes BA, Arrambide-Garza FJ, et al. Clinical scores for acute appendicitis in adults: a systematic review and meta-analysis of diagnostic accuracy studies. Am J Surg. 2025;240:116123.  [PMID:39667296]
  2. Scheijmans JCG, Haijanen J, Flum DR, et al. Antibiotic treatment versus appendicectomy for acute appendicitis in adults: an individual patient data meta-analysis. Lancet Gastroenterol Hepatol. 2025;10(3):222–233.  [PMID:39827891]
  3. Dahiya DS, Akram H, Goyal A, et al. Controversies and future directions in management of acute appendicitis: an updated comprehensive review. J Clin Med. 2024;13(11):3034.  [PMID:38892745]

Descriptive text is not available for this image See Also

Algorithm: Abdominal Rigidity

Descriptive text is not available for this image Codes

ICD-10

  • K35.80 Unspecified acute appendicitis
  • K35.2 Acute appendicitis with generalized peritonitis
  • K35.3 Acute appendicitis with localized peritonitis
  • K35.89 Other acute appendicitis
  • K35 Acute appendicitis
  • K35.8 Other and unspecified acute appendicitis

SNOMED

  • 85189001 Acute appendicitis (disorder)
  • 196781001 Acute appendicitis with peritonitis
  • 51036000 Acute appendicitis with peritoneal abscess (disorder)

Clinical Pearls

  • Anorexia with periumbilical pain localizing to RLQ is the classic history for acute appendicitis.
  • Diagnosis is more challenging in children, pregnant patients, and the elderly due to varying symptoms and signs.
  • In equivocal cases, CT scan is the diagnostic test of choice. Ultrasound and MRI are alternatives.
  • Acute appendicitis is the most common surgical emergency during pregnancy.

Last Updated: 2027

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