Acute Appendicitis

Disclaimer: This information is intended for educational purposes and as a general clinical reference. It is not a substitute for professional medical advice, diagnosis, or treatment. Clinical decisions must always be made by a qualified healthcare professional based on the individual patient's condition, available evidence, and clinical judgment. Always consult with a healthcare provider for any health concerns or before making any decisions related to patient care.

Overview

• Definition: Acute appendicitis is the acute inflammation of the vermiform appendix, a finger-like blind-ended tube projecting from the posteromedial wall of the cecum. It is the most common cause of acute abdominal pain requiring surgical intervention.
• Epidemiology:
  • Incidence: Approximately 100 cases per 100,000 population per year in Western countries, with a lifetime risk of 7-8%.
  • Age: Most common in the second and third decades of life (peak incidence between 10-30 years), but can occur at any age, including infancy and elderly.
  • Sex: Slightly more common in males than females (male-to-female ratio 1.4:1), but the incidence is equal in the pediatric age group.
• Classification:
  • Uncomplicated Appendicitis: Inflammation without gross perforation, gangrene, or significant periappendiceal abscess.
    • Simple/Catarrhal: Early inflammation, hyperemia, and edema.
    • Phlegmonous/Suppurative: More severe inflammation with pus formation in the lumen and wall.
  • Complicated Appendicitis: Associated with perforation, gangrene, or periappendiceal abscess/phlegmon.
    • Gangrenous: Ischemic necrosis of the appendiceal wall.
    • Perforated: Rupture of the appendiceal wall, leading to spillage of contents into the peritoneal cavity.
    • Appendiceal Abscess: Localized collection of pus around the inflamed appendix, often walled off by omentum and adjacent bowel loops.
    • Appendiceal Phlegmon: An inflammatory mass involving the appendix, omentum, and adjacent bowel loops, without a well-defined abscess cavity.

Pathophysiology

• Mechanism: The primary mechanism is thought to be luminal obstruction of the appendix. This obstruction leads to:
  1. Increased Intraluminal Pressure: Distal obstruction (e.g., by a fecalith, lymphoid hyperplasia, foreign body, stricture, or tumor) prevents drainage of normal appendiceal secretions and mucus.
  2. Stasis and Bacterial Overgrowth: The stagnant lumen promotes bacterial proliferation (e.g., E. coli, Bacteroides fragilis, Pseudomonas, enterococci, streptococci).
  3. Inflammation: The inflamed mucosa and increased pressure compromise lymphatic and venous drainage, leading to mucosal ischemia and bacterial invasion of the appendiceal wall.
  4. Ischemia and Necrosis: Persistent inflammation and vascular compromise lead to arterial insufficiency, necrosis, and gangrene of the appendiceal wall.
  5. Perforation: As the wall integrity deteriorates, perforation occurs, spilling luminal contents and bacteria into the peritoneal cavity, leading to localized or generalized peritonitis.
• Risk Factors:
  • Fecalith: The most common cause of obstruction (30-50% of cases).
  • Lymphoid Hyperplasia: Enlarged lymphoid follicles, especially in children and young adults, often triggered by viral infections (e.g., adenovirus, measles).
  • Foreign Bodies: Less common (e.g., fruit seeds, parasites, barium, indigestible food residues).
  • Tumors: Rare, but can cause obstruction, especially in older adults (e.g., carcinoid, adenocarcinoma, mucinous cystadenoma).
  • Diet: Low-fiber diets may be associated with increased risk, possibly due to slower transit time and increased fecalith formation.
  • Family History: Some evidence suggests a familial predisposition.
• Protective Factors:
  • High-fiber diet: May reduce the risk by promoting regular bowel movements and preventing fecalith formation, though evidence is not definitive for prevention.

Clinical Presentation

Signs and Symptoms

• Cardinal Features:
  • Periumbilical/Epigastric Pain (Visceral Pain): Vague, dull, poorly localized pain, typically the first symptom.
  • Migration of Pain (Somatic Pain): Within 1-12 hours, the pain typically shifts to the right lower quadrant (RLQ) as inflammation spreads to the parietal peritoneum (somatic innervation), becoming sharp, localized, and constant. This is a highly characteristic symptom (occurs in ~50-60% of cases).
  • Anorexia: Loss of appetite, almost universally present (occurs in ~90% of cases). Absence of anorexia should raise suspicion for alternative diagnoses.
  • Nausea and Vomiting: Usually follows the onset of pain; vomiting is typically not profuse and occurs in 50-60% of patients.
  • Fever: Low-grade fever (oral temperature 37.5-38.5°C) is common. High fever (>39°C) suggests perforation or other complications.
• Early Signs:
  • Vague periumbilical or epigastric discomfort.
  • Mild anorexia, nausea.
  • Mild constipation or diarrhea (especially in children, due to irritation of adjacent bowel).
• Advanced Signs:
  • Intensified, localized RLQ pain.
  • Guarding and rebound tenderness.
  • Increasing fever.
  • Signs of peritonitis (e.g., board-like rigidity, absent bowel sounds) if perforation has occurred.
• Atypical Presentations:
  • Retrocecal Appendix: Pain may be less localized, duller, or referred to the flank or back. Rebound tenderness may be absent. Psoas sign may be positive.
  • Pelvic Appendix: Pain may be localized to the hypogastrium or left lower quadrant. Urinary frequency/dysuria or tenesmus may be present due to bladder or rectal irritation. Obturator sign may be positive.
  • Pregnancy: The appendix shifts upward and laterally due to the enlarging uterus; pain may be in the RLQ, right flank, or even right upper quadrant (RUQ). Symptoms may be masked by common pregnancy discomforts (nausea, vomiting).
  • Pediatric Patients: Variable and non-specific symptoms, including irritability, lethargy, poor feeding, diffuse abdominal pain. Higher incidence of diarrhea and vomiting. Higher rate of perforation due to delayed diagnosis.
  • Geriatric Patients: Atypical or blunted symptoms (less severe pain, lower fever, less pronounced leukocytosis). Delayed presentation and higher perforation rates are common. Pain may be diffuse.
  • Immunocompromised Patients: Symptoms may be blunted or absent, leading to delayed diagnosis and increased perforation rates.

Physical Examination

• Inspection:
  • Patient often lies still, avoiding movement (peritonitis).
  • Abdominal distension (rare in early stages, suggests advanced peritonitis).
  • Observation for surgical scars.
• Palpation:
  • McBurney's Point Tenderness: Point of maximal tenderness located 1/3 of the way from the anterior superior iliac spine (ASIS) to the umbilicus. Highly suggestive of appendicitis.
  • Guarding: Involuntary contraction of abdominal muscles on palpation, indicating peritoneal irritation.
  • Rebound Tenderness: Pain elicited upon rapid withdrawal of the palpating hand, indicating parietal peritoneal inflammation.
  • Rigidity: Board-like hardening of the abdominal wall, a severe sign of peritonitis.
  • Rovsing's Sign: Palpation of the left lower quadrant causes pain in the right lower quadrant, due to retrograde distension of the colon, pushing inflamed appendiceal contents.
  • Psoas Sign (Cope's Psoas Test): Pain elicited in the RLQ with passive extension of the right hip or active flexion of the right hip against resistance. Suggests inflammation of a retrocecal appendix irritating the psoas muscle.
  • Obturator Sign: Pain in the RLQ with passive internal rotation of the flexed right hip. Suggests inflammation of a pelvic appendix irritating the obturator internus muscle.
  • Dunphy's Sign: Increased pain in the RLQ with coughing.
  • Heel Drop/Markle Sign: Pain in the RLQ when the patient drops from standing on toes to heels, jarring the peritoneum.
  • Rectal Exam: May reveal tenderness or a palpable mass (pelvic abscess), especially in children or if a pelvic appendix is suspected. Not routinely performed unless specific indications.
  • Pelvic Exam: In females, indicated to rule out gynecological causes (e.g., PID, ruptured ovarian cyst, ectopic pregnancy). May reveal cervical motion tenderness, adnexal tenderness.

Diagnostic Approach

History Taking

• Key Questions:
  • Pain characteristics: Onset (sudden vs. gradual), location (initial periumbilical/epigastric, then migration to RLQ), character (dull, aching vs. sharp, stabbing), severity (0-10 scale), aggravating/alleviating factors (movement, coughing, eating).
  • Associated symptoms: Anorexia (timing relative to pain), nausea, vomiting (timing relative to pain), fever/chills, changes in bowel habits (constipation, diarrhea), urinary symptoms (dysuria, frequency).
  • Last menstrual period (LMP) and possibility of pregnancy in females of childbearing age.
  • Past medical/surgical history: Previous abdominal surgeries, chronic medical conditions.
  • Medications: Especially recent antibiotic use.
• Red Flags:
  • High fever (>39°C).
  • Severe, diffuse abdominal pain with board-like rigidity and absent bowel sounds (suggests generalized peritonitis).
  • Hemodynamic instability (tachycardia, hypotension, altered mental status) suggests sepsis/shock.
  • Progressive worsening of symptoms despite initial management.

Laboratory Tests

• First-Line:
  • Complete Blood Count (CBC) with differential:
    • Leukocytosis: White blood cell (WBC) count often elevated, typically 10,000-18,000 cells/µL. Values >20,000 cells/µL may suggest perforation or abscess.
    • Neutrophilic Predominance with Left Shift: Increased percentage of neutrophils (>75%) and immature neutrophils (bands >5%). Normal WBC does not rule out appendicitis.
  • C-Reactive Protein (CRP): Often elevated (>10 mg/L) within 12-24 hours of symptom onset. Normal CRP, especially after 24 hours, makes appendicitis less likely but does not exclude it.
  • Urinalysis: To rule out urinary tract infection (UTI), kidney stones. May show a few RBCs or WBCs due to irritation of the ureter or bladder by an inflamed appendix.
  • Human Chorionic Gonadotropin (hCG): Essential for all females of childbearing potential to rule out pregnancy (especially ectopic pregnancy).
  • Electrolytes, BUN, Creatinine: Assess hydration status and renal function.
• Confirmatory: No single lab test is confirmatory for appendicitis; they support the clinical suspicion. Imaging is typically used for confirmation.
• Monitoring: Repeat CBC/CRP may be used to monitor response to non-operative management if chosen, or to track progression of infection.

Imaging

• Recommended: Imaging is crucial, especially in equivocal cases, to confirm diagnosis and rule out other conditions.
  • Ultrasonography (US):
    • Initial choice for children, thin adults, and pregnant women. Non-ionizing radiation.
    • Findings: Non-compressible, blind-ended, tubular structure in the RLQ with a diameter of >6 mm, wall thickening (>2 mm), presence of an appendicolith (echogenic focus with shadowing), periappendiceal fluid collection, and/or surrounding hyperechoic fat (stranding).
    • Sensitivity: 85-95% (operator dependent). Specificity: 90-95%.
    • Limitations: Bowel gas, obesity, retrocecal appendix can limit visualization. Non-diagnostic US requires further imaging or close observation.
  • Computed Tomography (CT) Scan:
    • Gold standard for adults and often preferred in the emergency setting due to high accuracy and rapid results. Typically performed with intravenous (IV) contrast; oral contrast may or may not be used. Low-dose CT protocols are increasingly used to reduce radiation exposure.
    • Findings: Enlarged appendix (>6 mm diameter), thickened appendiceal wall with enhancement, periappendiceal fat stranding, appendicolith (present in ~30% of cases), fluid collection, abscess formation, or phlegmon. The "target sign" or "cockade sign" is characteristic (concentric rings of attenuation).
    • Sensitivity: 92-98%. Specificity: 90-97%.
• Advanced:
  • Magnetic Resonance Imaging (MRI):
    • Preferred imaging modality for pregnant women (if US is equivocal) and increasingly used in children (if US is equivocal) due to absence of ionizing radiation.
    • Findings: Similar to CT, demonstrating an enlarged appendix, mural thickening, periappendiceal inflammation, and fluid collections.
    • Sensitivity: 96%. Specificity: 92%.
    • Limitations: Cost, availability, longer scan time, patient cooperation.

Management

Acute Management

• Immediate:
  • NPO (Nil per os): Patient should be NPO in anticipation of surgery.
  • Intravenous (IV) Access: Establish at least one large-bore IV line.
  • IV Fluids: Initiate crystalloid IV fluids (e.g., Lactated Ringer's or Normal Saline) to correct dehydration and maintain hemodynamic stability.
  • Pain Control: Administer analgesics (e.g., opioids like morphine or hydromorphone) for pain relief. Note: Pain medication does not mask the diagnosis or prevent accurate assessment; it improves patient comfort and allows for a more thorough examination.
  • Antiemetics: Administer antiemetics (e.g., ondansetron) for nausea/vomiting.
• Stabilization:
  • Antibiotic Prophylaxis: Administer broad-spectrum antibiotics pre-operatively for all suspected cases of appendicitis, or therapeutically for complicated appendicitis. This reduces the risk of post-operative wound infection and intra-abdominal abscess.
    • Common regimens:
      • Cefoxitin 1-2 g IV single dose (for uncomplicated, pre-op prophylaxis).
      • Cefazolin 1-2 g IV + Metronidazole 500 mg IV single dose.
      • Ampicillin-Sulbactam 3 g IV single dose.
      • For complicated appendicitis (perforation, abscess), antibiotics are continued for 3-5 days or until afebrile and leukocytosis resolves: e.g., Piperacillin-Tazobactam 3.375-4.5 g IV q6-8h, Meropenem 1 g IV q8h, or Ceftriaxone 1-2 g IV q24h + Metronidazole 500 mg IV q8h.
• Emergency:
  • Surgical Consultation: Urgent surgical consultation is paramount for confirmed or highly suspected acute appendicitis.
  • Preparation for Surgery: Type and cross-match for blood products, obtain informed consent.

Chronic Management

• Acute appendicitis is an acute condition and typically does not involve chronic management after successful treatment.
• For patients managed non-operatively for appendiceal phlegmon/abscess, follow-up imaging and monitoring for recurrence or complications (e.g., interval appendectomy) are part of the management.

Treatment Algorithms

• First-Line:
  • Laparoscopic Appendectomy: This is the standard of care for acute appendicitis in most cases.
    • Advantages: Smaller incisions, less pain, shorter hospital stay, faster recovery, reduced wound complications.
    • Procedure: Three small incisions are typically made. The abdomen is insufflated with CO2, a camera is inserted, and instruments are used to identify, ligate, and remove the appendix.
    • Conversion to Open: May be necessary if extensive inflammation, adhesions, or complications make laparoscopic approach difficult or unsafe.
• Second-Line:
  • Open Appendectomy: Performed through a small incision in the RLQ (e.g., McBurney or Rocky-Davis incision).
    • Indications: Contraindications to laparoscopy (e.g., severe cardiopulmonary disease, extensive prior abdominal surgeries with dense adhesions), perforated appendicitis with diffuse peritonitis, large phlegmon/abscess, or surgeon's preference/lack of laparoscopic expertise.
• Refractory Cases / Non-Operative Management (NOM):
  • Uncomplicated Appendicitis: In highly selected cases of uncomplicated appendicitis (no evidence of perforation, abscess, or appendicolith on imaging), non-operative management with antibiotics has been studied as an alternative to surgery, particularly in adults and children.
    • Regimen: IV antibiotics (e.g., Ceftriaxone + Metronidazole) initially, followed by oral antibiotics for 7-10 days.
    • Success Rate: ~70-80% at 1 year.
    • Recurrence Rate: ~10-30% within 1 year, requiring appendectomy.
    • Patient Selection: Close monitoring is crucial; patients must be compliant and have no signs of peritonitis or systemic toxicity. Contraindicated if appendicolith is present or if complicated appendicitis is suspected.
  • Appendiceal Phlegmon or Abscess:
    • Initial Management: Often treated non-operatively with IV antibiotics (e.g., Piperacillin-Tazobactam, Carbapenem, or Ceftriaxone/Cefepime + Metronidazole) to allow inflammation to subside.
    • Percutaneous Drainage: If a well-defined abscess >3-4 cm is present, image-guided percutaneous drainage is often performed in conjunction with antibiotics.
    • Interval Appendectomy: After successful non-operative management of a phlegmon or abscess, an interval appendectomy (elective appendectomy 6-12 weeks later) is often recommended, particularly in older patients or if an appendicolith was present, to prevent recurrence and rule out underlying malignancy (e.g., carcinoid, adenocarcinoma). The need for routine interval appendectomy is debated, especially in younger patients without an appendicolith.

Complications

• Common:
  • Wound Infection: Occurs in 5-10% of cases, higher in perforated appendicitis.
  • Intra-abdominal Abscess: Localized collection of pus within the abdomen (e.g., pelvic, subphrenic).
• Serious:
  • Perforation: Occurs in 15-30% of cases, especially in children and elderly, leading to peritonitis.
  • Generalized Peritonitis: Widespread inflammation of the peritoneum, a life-threatening condition.
  • Sepsis and Septic Shock: Systemic inflammatory response to severe infection, leading to organ dysfunction.
  • Pylephlebitis: Suppurative thrombophlebitis of the portal vein, a rare but severe complication, leading to liver abscesses.
  • Small Bowel Obstruction (SBO): Due to adhesions formed after inflammation or surgery.
• Long-term:
  • Adhesions: Can cause chronic abdominal pain or recurrent SBO.
  • Stump Appendicitis: Rare inflammation of the remnant appendiceal stump if not completely removed during the initial appendectomy.
  • Infertility (in females): If severe peritonitis causes tubal damage, though rare.

Prognosis

• Factors:
  • Stage at presentation: Uncomplicated appendicitis has an excellent prognosis. Perforated appendicitis carries higher morbidity and mortality.
  • Age: Extremes of age (very young and very old) have worse outcomes due to delayed diagnosis and higher perforation rates.
  • Comorbidities: Patients with underlying chronic diseases (e.g., diabetes, immunocompromised status) have an increased risk of complications.
  • Time to treatment: Shorter duration from symptom onset to surgery is associated with lower perforation rates.
• Survival:
  • Uncomplicated Appendicitis: Mortality rate is extremely low, generally <0.1%.
  • Perforated Appendicitis: Mortality rate is higher, ranging from 0.6% in the general population to 5-10% in the very young, elderly, or immunocompromised.
• Quality of Life:
  • Following successful appendectomy, most patients make a full recovery with no long-term sequelae and return to normal quality of life within a few weeks.
  • Post-operative pain and minor complications usually resolve quickly.

Prevention

• Primary: There are no definitive primary prevention strategies for acute appendicitis. Dietary fiber intake has been inconsistently linked to a reduced risk.
• Secondary: Early recognition of symptoms and prompt medical evaluation are crucial for early diagnosis, which prevents progression to complicated appendicitis (perforation).
• Tertiary: Prompt and appropriate surgical or non-operative management of acute appendicitis is essential to prevent severe complications (e.g., peritonitis, sepsis, abscess formation) and optimize patient outcomes.

Special Populations

• Pediatric:
  • Presentation: Often atypical and non-specific (irritability, lethargy, poor feeding, diffuse pain, diarrhea, vomiting). Rapid progression to perforation is common.
  • Diagnosis: Clinical suspicion is high; US is the preferred initial imaging. MRI if US is equivocal. CT is used judiciously due to radiation concerns.
  • Management: Prompt surgical intervention; non-operative management is being studied for very selected cases of uncomplicated appendicitis without appendicolith.
• Geriatric:
  • Presentation: Atypical and often subtle (less severe pain, less fever, blunted leukocytosis, diffuse abdominal pain). Delayed diagnosis is common.
  • Diagnosis: Higher threshold for suspicion. CT scan is generally preferred due to higher diagnostic accuracy in this population.
  • Management: Higher risk of perforation, complications, and mortality. Aggressive resuscitation and prompt surgical intervention are critical. Non-operative management of phlegmon/abscess is common, often followed by interval appendectomy due to increased risk of underlying malignancy (e.g., carcinoma of the cecum mimicking appendicitis) or recurrence.
• Pregnancy:
  • Incidence: Approximately 1 in 1,500 pregnancies. Most common non-obstetric surgical emergency during pregnancy.
  • Presentation: RLQ pain may shift upwards (to RUQ) or laterally due to uterine displacement. Nausea and vomiting are common in pregnancy, potentially masking symptoms.
  • Diagnosis: US is the first-line imaging. If inconclusive, MRI without gadolinium is the preferred second-line modality. CT is reserved for specific cases where MRI is unavailable or non-diagnostic due to radiation exposure to the fetus.
  • Management: Prompt appendectomy is crucial to minimize maternal and fetal morbidity. Laparoscopic appendectomy is generally safe throughout pregnancy, especially in the first two trimesters. Risk of preterm labor or fetal loss increases significantly with perforation.
• Comorbidities:
  • Immunocompromised Patients: (e.g., HIV/AIDS, transplant recipients, chemotherapy patients) have blunted inflammatory responses, leading to delayed diagnosis and higher perforation rates. May present with unusual pathogens (e.g., CMV, fungal).
  • Diabetic Patients: Increased risk of complications, wound infections, and potentially slower recovery.
  • Inflammatory Bowel Disease (IBD): Can mimic appendicitis. Appendicitis in IBD patients can complicate their underlying condition.

Clinical Pearls

• "Pain first, then vomit": The typical sequence of symptoms (periumbilical pain migrating to RLQ, followed by nausea/vomiting) is highly suggestive of appendicitis. Vomiting before pain suggests other diagnoses (e.g., gastroenteritis).
• Anorexia is key: Anorexia is present in almost all patients with acute appendicitis. Its absence should make one seriously reconsider the diagnosis.
• Don't delay pain control: Administering analgesia does not mask clinical signs of peritonitis and can facilitate a more thorough physical examination.
• Consider alternatives: Always keep a broad differential diagnosis, especially in women (GYN pathology: ectopic pregnancy, PID, ovarian torsion, ovarian cyst rupture) and children (mesenteric adenitis, gastroenteritis, Meckel's diverticulitis).
• The "normal" appendix: Up to 15-20% of appendectomies yield a histologically normal appendix. This is acceptable to avoid missing complicated appendicitis, but the aim is to minimize negative appendectomy rates with accurate imaging.
• Role of appendicolith: The presence of an appendicolith on imaging significantly increases the likelihood of appendicitis and suggests a higher risk of perforation and recurrence if managed non-operatively.

Recent Updates

• Non-Operative Management (NOM): Increasing evidence supports the use of antibiotic therapy alone for uncomplicated acute appendicitis in selected patients. While effective for initial resolution, recurrence rates are noted, leading to ongoing debate about routine interval appendectomy. Current guidelines suggest shared decision-making with patients regarding NOM vs. appendectomy for uncomplicated cases.
• Imaging Prioritization: Growing emphasis on judicious use of imaging to reduce radiation exposure, especially in children and young adults. Ultrasound is increasingly used as the first-line imaging, with MRI as a second-line option when US is inconclusive, reserving CT for definitive cases or when other modalities are unavailable.
• Enhanced Recovery After Surgery (ERAS) Protocols: Application of ERAS principles to appendectomy, including pre-operative carbohydrate loading, multimodal pain management, early ambulation, and judicious use of drains and nasogastric tubes, to optimize patient recovery and reduce hospital stay.
• Optimal Duration of Antibiotics for Complicated Appendicitis: Recent studies suggest shorter courses (e.g., 3-5 days) of antibiotics may be sufficient for complicated appendicitis after source control, rather than prolonged courses.

Key References

• Guidelines:
  • American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) Guidelines.
  • World Society of Emergency Surgery (WSES) Guidelines for the Management of Acute Appendicitis (2020 Update).
  • Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) Guidelines for the Clinical Application of Laparoscopic Bariatric Surgery (Relevant for surgical aspects).
  • American College of Radiology (ACR) Appropriateness Criteria for Acute Abdominal Pain.
• Studies:
  • Meta-analyses and randomized controlled trials comparing non-operative management vs. appendectomy for uncomplicated appendicitis (e.g., APPAC trial, CODA trial).
  • Large prospective cohort studies on diagnostic accuracy of imaging modalities (US, CT, MRI) in different patient populations.
• Reviews:
  • Recent reviews on acute appendicitis in major surgical journals (e.g., Annals of Surgery, JAMA Surgery, British Journal of Surgery) and comprehensive clinical references (e.g., UpToDate, Harrison's Principles of Internal Medicine, Schwartz's Principles of Surgery).