> Table of Contents > Appendicitis, Acute
Appendicitis, Acute
Anila Khaliq, MD
Komel Safdar, MBBS
Fariah Hanna, MBBS
image BASICS
  • Acute inflammation of the vermiform appendix, first described by Reginald Fitz in 1886
  • Arising from the base of the cecum in right lower quadrant (RLQ); can be localized anterior, posterior, medial, lateral to the cecum, as well as in the pelvis. Vascular supply by appendicular artery, a branch of the ileocolic artery. Nerve supply derived from the superior mesenteric plexus.
  • Most common cause of acute surgical abdomen
  • Predominant age: 10 to 30 years: rare in infancy
  • Predominant sex: slight male predominance:
    • Ages 10 to 30: male > female (3:2)
    • Age >30: male = female
  • 1 case per 1,000 people per year
  • Lifetime incidence 1 in every 15 persons (7%)
Pregnancy Considerations
  • Most common extrauterine surgical emergency
  • No more common in pregnant versus nonpregnant women
  • Higher rate of perforation; more likely to present with peritonitis
The cause is thought to be obstruction of the appendiceal lumen. This leads to distention, ischemia, and bacterial overgrowth. Without intervention, most cases of appendicitis will lead to perforation and subsequently abscess formation or generalized peritonitis. Causes of obstruction:
  • Fecaliths (most common)
  • Lymphoid tissue hyperplasia (in children)
  • Vegetable, fruit seeds, and other foreign bodies
  • Intestinal worms (ascarids)
  • Strictures, fibrosis, neoplasms
First-degree relative with history of appendicitis increases risk, although no direct genetic link has been found.
Adolescent males, familial tendency, intra-abdominal tumors
  • Diagnosis of acute appendicitis relies on the history and physical examination with supporting laboratory studies and imaging.
  • Scoring systems
    • Modified Alvarado Scoring System (MASS): The use of MASS in the diagnosis of acute appendicitis has been reported to improve the diagnostic accuracy and consequently reduces negative appendectomy and complication rates.
    • Use of MASS in for acute appendicitis in female patients should be supplemented by additional investigations like abdominal ultrasound or laparoscopy.
    • A MASS score above 7 should indicate appendectomy without the need for further imaging.
  • A cutoff point of 6 for the MASS score will yield higher sensitivity and a better diagnosis of appendicitis but provides an increase in negative appendectomy.
  • Pediatric Appendicitis Score—this has been developed to help predict the likelihood of acute appendicitis, although diagnosis is still considered a clinical decision.
  • 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 necessary to rule out other causes of lower abdominal pain (e.g., pelvic inflammatory disease, prostatitis).
  • Serial exams can be useful in indeterminate cases.
  • 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
  • Difficult diagnosis
  • Normal response to infection/inflammation is suppressed.
  • Appendix displaced out of pelvis by gravid uterus
Geriatric Considerations
Decreased diagnostic accuracy, more likely to be atypical presentation
Initial Tests (lab, imaging)
  • Leukocytosis: WBC >10,000/mm3 (70%)
  • Polymorphonuclear predominance or “left shift” (>90%)
  • Human chorionic gonadotropin (hCG) (if negative, rule out ectopic pregnancy)
  • Urinalysis: hematuria, pyuria (˜30%)
  • C-reactive protein: nonspecific inflammatory marker. When paired with an elevated WBC can increase the likelihood of appendicitis.
  • Drugs may alter lab results: antibiotics, steroids.
  • Imaging used in cases of suspected appendicitis when the diagnosis is not clear; is helpful to detect complications (abscess, perforation)
  • Plain films: little utility, nonspecific findings, may visualize fecalith
  • CT scan with contrast: sensitivity ˜91-98%; specificity 95-99%; imaging modality of choice. However, growing concern regarding radiation dose, particularly in young patients (1)[A].
  • Ultrasound: alternative in pregnant patients, children, and in women with suspected gynecologic pathology. Sensitivity and specificity vary by report and accuracy depends on the skill of the ultrasonographer. Can rule in appendicitis but cannot reliably exclude the diagnosis. Starting with an ultrasound and, if negative, obtaining a CT scan has been proposed as an effective workup strategy (2)[B].
  • MRI: growing in popularity for diagnosing pregnant patients but also may be useful for patients with contrast allergies and/or patients with 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 study.
Diagnostic Procedures/Other
Exploratory laparotomy/laparoscopy: Acceptable nontherapeutic 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
Surgery (appendectomy) is the standard of care for acute, uncomplicated appendicitis.
First Line
  • Uncomplicated acute appendicitis: perioperative dose of antibiotic (3)[A]: single dose of cefoxitin or ampicillin/sulbactam (Unasyn) or cefazolin plus metronidazole
  • 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
  • Among patients with CT-proven, uncomplicated appendicitis, antibiotic treatment did not meet the prespecified criterion for noninferiority compared with appendectomy. Most patients randomized to antibiotic treatment for uncomplicated appendicitis did not require appendectomy during the 1-year follow-up period, and those who required appendectomy did not experience significant complications.
  • 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 (4)[A].
  • Uncomplicated acute appendicitis: clindamycin plus one of the following: ciprofloxacin, levofloxacin, gentamicin, or aztreonam
  • Gangrenous or perforated appendicitis: ciprofloxacin or levofloxacin plus metronidazole or monotherapy with a carbapenem (imipenem and cilastatin, meropenem, ertapenem)
All cases of appendicitis require emergent surgical consultation.
  • Inpatient surgery is indicated.
  • Patients presenting within 72 hours of onset:
    • Immediate appendectomy; laparoscopic favored unless perforation (5)[A]
    • Drainage of abscess, if present
  • Patients who present late (>4 to 5 days after symptom onset) may be treated initially with antibiotics, bowel rest, and drainage of any abscess. Later (4 to 10 weeks) appendectomy can then be performed in this subgroup only.
Admission Criteria/Initial Stabilization
All patients with appendicitis should be admitted.
IV Fluids
Fluid resuscitation with normal saline (NS) or lactated Ringer (LR) solution. Correct fluid and electrolyte deficits.
Preoperative preparation
Discharge Criteria
Tolerating PO; return of bowel function; afebrile; normal WBC
  • Return to work is usually possible 1 to 2 weeks following most uncomplicated appendicitis.
  • Restrict activity for 4 to 6 weeks after surgery: No heavy lifting (> 10 lb) or strenuous physical activity.
Contact physician for postoperative development of:
  • Anorexia, nausea, vomiting
  • Abdominal pain, fever, chills
  • Signs/symptoms of wound infection
  • Generally uncomplicated course in young adults with unruptured appendicitis
  • Factors increasing morbidity and mortality: extremes of age, presence of appendiceal rupture
  • 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%
1. Hlibczuk V, Dattaro JA, Jin Z, et al. Diagnostic accuracy of noncontrast computed tomography for appendicitis in adults: a systematic review. Ann Emerg Med. 2010;55(1):51.e1-59.e1.
2. Poortman P, Oostvogel HJ, Bosma E, et al. Improving diagnosis of acute appendicitis: results of a diagnostic pathway with standard use of ultrasonography followed by selective use of CT. J Am Coll Surg. 2009;208(3):434-441.
3. Andersen BR, Kallehave FL, Andersen HK. Antibiotics versus placebo for prevention of postoperative infection after appendicectomy. Cochrane Database Syst Rev. 2005;(3):CD001439.
4. Simillis C, Symeonides P, Shorthouse AJ, et al. A meta-analysis comparing conservative treatment versus acute appendectomy for complicated appendicitis (abscess or phlegmon). Surgery. 2010;147(6):818-829.
5. Sauerland S, Lefering R, Neugebauer EA. Laparoscopic versus open surgery for suspected appendicitis. Cochrane Database Syst Rev. 2004;(4):CD001546.
6. Wilms IM, de Hoog DE, de Visser DC, et al. Appendectomy versus antibiotic treatment for acute appendicitis. Cochrane Database Syst Rev. 2011;(11):CD008359.
Additional Reading
  • Kanumba ES, Mabula JB, Rambau P, et al. Modified Alvarado Scoring System as a diagnostic tool for acute appendicitis at Bugando Medical Centre, Mwanza, Tanzania. BMC Surg. 2011;11:4.
  • Nasiri S, Mohebbi F, Sodagari N, et al. Diagnostic values of ultrasound and the Modified Alvarado Scoring System in acute appendicitis. Int J Emerg Med. 2012;5(1):26.
  • Salminen P, Paajanen H, Rautio T, et al. Antibiotic therapy vs appendectomy for treatment of uncomplicated acute appendicitis: the APPAC randomized clinical trial. JAMA. 2015;313(23):2340-2348.
See Also
Algorithm: Abdominal Rigidity
  • K35.80 Unspecified acute appendicitis
  • K35.2 Acute appendicitis with generalized peritonitis
  • K35.3 Acute appendicitis with localized peritonitis
Clinical Pearls
  • Classic history of anorexia with periumbilical pain localizing to RLQ is the cornerstone of diagnosis for acute appendicitis.
  • Diagnosis is much more challenging in children, pregnant patients, and the elderly due to varying symptoms and signs.
  • In equivocal cases, CT of abdomen and pelvis is the diagnostic test of choice, although ultrasound and MRI are useful alternatives.
  • Acute appendicitis is the most common surgical emergency during pregnancy.