Appendicitis

Overview

Definition

Appendicitis is the inflammation of the vermiform appendix.

Epidemiology

• Lifetime risk: approximately 8%
• 6% of the population gets appendicitis.
• Peak incidence: 10–19 years of age
• Males > females
• The most common acute surgical problem in the pediatric population

Etiology

• Obstruction of appendiceal orifice (implicated, but not often proven)
• Cause of obstruction varies with age.
  • Children and young adults: lymphoid follicular hyperplasia secondary to infection
  • Older adults:
    • Fecaliths
    • Calculi
    • Fibrosis
    • Tumors (benign or malignant)
  • Rare: parasites (usually in endemic areas)

Pathophysiology and Clinical Presentation

Pathophysiology

• Obstruction of appendiceal orifice is the 1st step (presumed).
• Mucus accumulation and luminal distention:
  • Bacterial overgrowth (mixed; aerobes and anaerobes):
    • Escherichia coli 
    • Peptostreptococcus
    • Pseudomonas
    • Bacteroides fragilis
  • Increase in transmural pressure → thrombosis and occlusion of small vessels
  • Ischemia and necrosis (gangrene)
  • Eventual perforation

Time course

Early:

• Usually first 24 hours
• Distention of the appendix stimulates T8–10 afferent nerves.
• Vague periumbilical pain develops.

Late:

• Usually after 24 hours
• Invasion of appendiceal wall by bacteria + ischemia
• Propagation of neutrophilic exudate → fibropurulent reaction involving serosal surface
• Peritoneal irritation → localized pain and tenderness

Perforation:

• Affects 13%–20% of cases
• In 65% of cases, symptoms last longer than 48 hours.
• In 20% of cases, symptoms last less than 24 hours.
• More likely with calculus as the obstructing culprit:
  • Walled-off perforation: abscess formation
  • Free perforation: generalized peritonitis

Clinical presentation

Classic:

• Periumbilical pain that later migrates to the right lower quadrant (RLQ)
• Anorexia
• Nausea/vomiting
• Fever

Atypical:

• Indigestion
• Diarrhea
• Generalized malaise

Anatomic factors:

• Anterior appendix (most common): pronounced localized RLQ pain
• Retrocecal: dull abdominal pain
• Pelvic: dysuria, diarrhea, tenesmus (from bladder and rectal irritation)

Diagnosis

History

• Duration of symptoms: typically 24–48 hours
• Abdominal pain:
  • Sudden onset 
  • Constant, becoming progressively worse
  • Exacerbated by movement
• Anorexia, nausea, diarrhea/constipation may or may not be present.
• Symptoms may be vague/atypical in the elderly.
• Adults (eliminate other causes):
  • History of inflammatory bowel disease
  • History of colorectal cancer/previous colonoscopy
  • Reproductive/sexually transmitted diseases in women (rule out pelvic inflammatory disease (PID), ectopic pregnancy)
• Children:
  • Most common in 5–12-year-olds
  • Very rare in neonates
  • Rule out viral illness:
    • History of concurrent or preceding respiratory symptoms
    • History of sick contacts with similar symptoms

Physical exam

General:

• Low-grade fever (up to 38.3°C (101°F))
• High fever may indicate late appendicitis/necrosis/perforation.
• Desire to lie still, with difficulty ambulating (common in children)
• Signs of dehydration if prolonged vomiting/anorexia:
  • Tachycardia
  • Orthostatic hypotension
  • Decreased urinary output

Abdominal exam:

• RLQ tenderness
• Localized rebound tenderness (peritoneal irritation)
• Signs:
  • McBurney’s point tenderness: maximal tenderness at 3.8–5.0 cm (1.5–2 in) from anterior iliac spine on a straight line to the umbilicus 
  • Rovsing’s sign: pain in the RLQ with palpation of the left lower quadrant
  • Psoas sign: RLQ pain with passive hip extension (characteristic of retrocecal appendix)
  • Obturator sign: RLQ pain with internal hip rotation with a flexed knee (pelvic appendix)
• Generalized peritonitis suggests perforation.

Rectal exam:

• Not helpful for establishing appendicitis diagnosis
• May be helpful if an alternative diagnosis is suspected

Pelvic exam:

• May be needed in a female if PID is suspected
• Appendicitis (especially pelvic) may also produce tenderness on pelvic exam.

Laboratory studies

• Complete blood count (CBC): leukocytosis with a left shift
• Inflammatory markers: ↑ erythrocyte sedimentation rate (ESR), C-reactive protein (CRP)
• Chemistry may show dehydration pattern: low K (potassium), low Na (sodium), metabolic alkalosis
• Urinalysis: may show mild pyuria due to proximity of the right ureter
• Pregnancy test: Perform on all females of reproductive age.

Alvarado score

• A numerical scale for predicting the likelihood of appendicitis based on clinical and laboratory findings
• Facilitates decision making
• Mnemonic: MANTRELS

Imaging

Imaging is not required for diagnosis if the Alvarado score is very low (< 3) or high (> 7).

• Computed tomography (CT) scan:
  • Highest diagnostic accuracy
  • Should be performed with intravenous contrast unless contraindicated (renal failure, allergy)
  • Findings of appendicitis:
    • Appendiceal diameter > 6 mm (0.24 in) with occluded lumen
    • Appendiceal wall thickening  > 2 mm (0.08 in)
    • Appendiceal wall enhancement
    • Periappendiceal fat stranding
    • Appendicolith (in about 25% of cases)
• Ultrasound (US):
  • Lower diagnostic accuracy than CT
  • Operator dependent
  • Preferred test in children and pregnant women as it avoids radiation
  • Signs of appendicitis:
    • Non-compressible appendix
    • Appendix diameter > 6 cm (2.4 in)
    • Focal pain with pressure from US probe
    • Increased echogenicity of surrounding fat
    • Fluid in RLQ
    • “Target sign”:
      • Hypoechoic (fluid-filled lumen)
      • Hyperechoic (mucosa/submucosa)
      • Hypoechoic (muscularis layer)
• Magnetic resonance imaging (MRI):
  • Inferior to CT scan
  • An alternative when CT is contraindicated

Management

Initial management

• Intravenous resuscitation (hydrate and replace electrolytes)
• NPO (nothing by mouth)
• Analgesia, nausea control
• Intravenous antibiotics:
  • Cefoxitin
  • Cefazolin + metronidazole
  • Clindamycin + ciprofloxacin/aztreonam

Non-perforated appendicitis

Non-operative management:

• Growing evidence that appendicitis can be managed with antibiotics alone
• 90% will initially respond to antibiotics.
• Recurrence rate of 20%–30% in the first year

Appendectomy:

• Laparoscopic:
  • Lower rate of wound infections
  • Less pain on postoperative day 1
  • Shorter hospital stay
• Open:
  • Lower rate of intraabdominal infections
  • Shorter operative time

Perforated appendicitis

Initial non-operative management:

• Preferred approach as immediate surgery has high risk of complications:
  • More extensive surgery (ileocecectomy) may be required
  • Risk of postoperative abscess, fistula
• Indicated for contained perforation:
  • Cecal phlegmon or abscess > 3 cm (1.18 in) on CT scan
  • Stable patient without diffuse peritonitis
• Intravenous antibiotics: broad-spectrum enteric coverage
• Intravenous fluids and bowel rest
• Radiologically guided drainage of an abscess
• Successful (patient is discharged home with 7–10-day course of oral antibiotics):
  • ↓ Pain
  • ↓ Fever
  • ↓ Leukocytosis
• Unsuccessful: rescue appendectomy during the same admission

Interval appendectomy:

• Generally recommended 6–8 weeks after successful nonoperative management 
• If not performed:
  • Up to 30% risk of recurrence during the 1st year
  • 10%–29% risk of neoplasm in perforated appendix 
• Colonoscopy should also be considered for patients > 40.

Immediate appendectomy:

• Always indicated for unstable patient with generalized peritonitis/free perforation
• May require more extensive resection (ileocecectomy)
• Requires washout and drainage of peritoneal cavity
• Can also be performed for contained perforation with small phlegmon or abscess (< 3 cm (1.18 in))

Prognosis

• Mortality is low: 0.09%–4%
• Complications of appendectomy:
  • Wound infection: 3.3%–10.3%
  • Pelvic/abdominal abscess: 9.4%
  • Stump appendicitis: if appendix was not completely removed, leaving more than 0.5 cm (0.2 in) stump

Differential Diagnosis

Gastrointestinal

• Gastroenteritis: acute self-limited viral illness presenting with abdominal pain, vomiting, and diarrhea. Imaging and labs may be largely normal. Condition is treated supportively with bowel rest and intravenous hydration.
• Mesenteric lymphadenitis: inflammation of mesenteric lymph nodes associated with acute or chronic abdominal pain. Mesenteric lymphadenitis commonly localizes to RLQ because of a large number of lymph nodes in that area. Computed tomography scan/US will show lymphadenopathy.
• Epiploic appendagitis: ischemia/infarction of the colonic fatty appendages. Epiploic appendagitis presents with acute or subacute lower abdominal pain. Computed tomography scan can confirm the diagnosis. Usually, this self-limited illness is treated with oral anti-inflammatory medications.
• Meckel’s diverticulitis: inflammation of Meckel’s diverticulum. The condition may be impossible to clinically distinguish from acute appendicitis as the pain is similar; however, it may be more central or left-sided. Occasionally, there is a history of intermittent lower gastrointestinal bleeding. Computed tomography scan may or may not be diagnostic. Sometimes, diagnosis is made during surgery.
• Right-sided diverticulitis: inflammation of colonic diverticula. Usually left-sided, but right-sided presentation can also occur, especially in young patients and in Asian populations. Patients present with RLQ pain, fever, and change in bowel habits. Diagnosis is made by CT scan.
• Terminal ileitis: inflammation of the terminal ileum that can have an antecedent history of abdominal cramping, weight loss, and diarrhea. The ileitis may be non-specific, due to Crohn’s disease or Yersinia infection. Diagnosis is made acutely by CT scan. Colonoscopy (Crohn’s) and serum antibody titers (Yersinia) can help establish the etiology.

Genitourinary

• Right ureteric colic: obstructive stone in the right ureter that presents as intermittent (colicky) pain of the right flank/groin. Urinalysis will show the presence of red blood cells. Diagnosis is established by non-contrast CT scan.
• Urinary tract infection: bacterial infection of the urinary tract in the form of cystitis (bladder infection) or right-sided acute pyelonephritis (kidney involvement). Presents with suprapubic pain and dysuria (cystitis) or right costovertebral angle tenderness and fever (pyelonephritis). Diagnosis is made by urinalysis and CT scan.

Gynecologic

• Right-sided ectopic pregnancy: pregnancy in the right fallopian tube. Presents with right-sided abdominal pain. When ruptured, can present with fever, sepsis, and peritonitis. Usually, there is a history of a missed menstrual period. Findings include a positive pregnancy test and pain with cervical manipulation (pelvic exam). Diagnosis is confirmed with pelvic US.
• PID: sexually transmitted infection involving internal reproductive organs, usually in a young adult woman. Pelvic inflammatory disease presents with lower abdominal pain (mostly bilateral), fever, and vaginal discharge. Diagnosis is established with pelvic exam and US.
• Ovarian and fallopian tube torsion: causes acute ischemia of the ovary/fallopian tube. Torsion presents with abdominal pain (RLQ if on the right), fever, and nausea/vomiting. When suspected, a Doppler pelvic US (looking at the blood flow) should be performed. The condition can affect females of both adult and pediatric age.
• Ruptured ovarian cyst (right): fluid or blood released from the cyst causes peritoneal irritation and acute onset of RLQ abdominal pain. Diagnosis is made by pelvic US.