Appendicitis diagnosis and treatment

Acute Appendicitis: Diagnosis, Risk Stratification & Management

Acute appendicitis is the most common non-trauma general surgical emergency worldwide, with a lifetime incidence of approximately 7% to 8%.

Pathogenesis

The primary initiating event is luminal obstruction of the vermiform appendix. Causes include:

• Faecoliths (appendicoliths): Hardened concretions of faecal matter, calcium salts, and inspissated mucus (predominant in adults).
• Lymphoid Hyperplasia: Submucosal lymphoid follicles expand in response to viral or bacterial infections (predominant in children and adolescents).
• Neoplasms: Carcinoid (neuroendocrine) tumors, adenocarcinoma of the appendix or caecum (critical to exclude in patients $> 50$ years).
• Foreign bodies or parasites: Enterobius vermicularis, gallstones.

Obstruction traps continuous mucosal secretions, causing exponential rise in intraluminal pressure ($> 60\text{ cmH}_2\text{O}$). This exceeds capillary and venous filling pressures, inducing mucosal ischaemia, bacterial invasion of the appendiceal wall (Bacteroides fragilis, Escherichia coli), transmural infarction, gangrene, and perforation (typically within 24 to 36 hours of symptom onset).

Clinical Presentation and Physical Signs

• Classic Symptom Evolution:
  1. Dull, crampy, periumbilical visceral pain (T10 midgut referral) accompanied by anorexia, nausea, and occasional vomiting.
  2. After 6 to 12 hours, transmural inflammation reaches the serosa and irritates the adjacent parietal peritoneum. The pain migrates to the right iliac fossa (RIF), becoming sharp, severe, constant, and precisely localized to McBurney's point (one-third the distance along a line drawn from the anterior superior iliac spine to the umbilicus).
• Physical Signs:
  • McBurney Point Tenderness: Maximal tenderness upon palpation at McBurney's point.
  • Rovsing Sign: Palpation in the left lower quadrant elicits pain in the right lower quadrant, caused by retroflexion of colonic gas or parietal peritoneal shift.
  • Psoas Sign: Pain upon passive extension of the right hip while the patient lies in the left lateral position, or upon active right hip flexion against resistance. Indicates an inflamed retrocaecal appendix lying directly upon the psoas major muscle.
  • Obturator Sign: Pain upon passive internal rotation of the flexed right hip. Indicates an inflamed pelvic appendix abutting the obturator internus muscle.

Clinical Risk Stratification: Alvarado Score

The Alvarado (MANTRELS) score helps guide the diagnostic workup:

• M: Clinical Feature: Migration of pain to the right iliac fossa; Score Value: 1

• A: Clinical Feature: Anorexia (acetone in urine / loss of appetite); Score Value: 1

• N: Clinical Feature: Nausea or vomiting; Score Value: 1

• T: Clinical Feature: Tenderness in the right lower quadrant; Score Value: 2

• R: Clinical Feature: Rebound tenderness; Score Value: 1

• E: Clinical Feature: Elevated temperature ($\ge 37.3^\circ\text{C}$); Score Value: 1

• L: Clinical Feature: Leukocytosis (WCC $> 10.0 \times 10^9\text{/L}$); Score Value: 2

• S: Clinical Feature: Shift of neutrophils to the left (neutrophilia $> 75\%$); Score Value: 1

• Total: Score Value: 10

• Score 1–4 (Low Risk): Appendicitis is highly unlikely. Investigate alternative aetiologies; discharge with clear red-flag return instructions if clinical exam is benign.

• Score 5–6 (Intermediate Risk): Equivocal. Requires diagnostic imaging (ultrasound or CT) or serial clinical evaluation.

• Score 7–10 (High Risk): Highly suggestive of acute appendicitis. Warrant surgical consultation for diagnostic imaging or direct progression to laparoscopy.

Diagnostic Imaging Pathways in Australian Practice

• Imaging selection: In pregnancy, ultrasound is usually first and MRI can resolve uncertainty without radiation. In non-pregnant adults, choose ultrasound or CT according to the suspected condition and diagnostic need; sex alone does not make transvaginal ultrasound mandatory. Suspected pelvic disease needs an appropriate consented pelvic assessment.
• Adult Males and Older Adults (> 50 years): Contrast-enhanced CT of the abdomen and pelvis (IV contrast with oral/rectal contrast if indicated) is the diagnostic imaging modality of choice. CT possesses sensitivity and specificity $> 95\%$, reliably demonstrates appendiceal dilatation ($> 6\text{ mm}$), circumferential wall thickening, periappendiceal fat stranding, appendicoliths, and phlegmon/abscess formation, while excluding caecal carcinoma, diverticulitis, and mesenteric adenitis.
• Pregnancy testing: Assess pregnancy possibility in reproductive-age patients with abdominal pain. Obtain hCG promptly, but do not delay lifesaving resuscitation, imaging or surgery in an unstable patient solely to await it.

Surgical Management and Appendiceal Mass

• Uncomplicated Appendicitis: The gold standard definitive treatment is early laparoscopic appendicectomy (ideally performed within 12 to 24 hours of admission). Early intervention minimizes the risk of progression to gangrene and transmural perforation.
• Appendiceal Phlegmon / Abscess (Appendiceal Mass): Occurs when a walled-off perforation is contained by the greater omentum and adjacent small bowel loops. Presenting 3 to 7 days after symptom onset with a tender, palpable mass in the RIF without generalized peritonitis.
  • Appendiceal abscess or phlegmon: Stable patients may be managed with antibiotics, with drainage for an accessible collection. Experienced surgical teams may also offer early laparoscopy. Generalised peritonitis or deterioration changes the urgency; no historical named regimen is compulsory for every patient.
  • Drainage: Size, safe access, response to antibiotics and local expertise determine whether a collection is drained. A 3–4 cm measurement alone does not mandate a procedure.
  • Follow-up: After non-operative appendicitis treatment, consider age, imaging and recurrence risk. Older adults, particularly those at least 40, need assessment for underlying malignancy; colonoscopy and interval imaging are not compulsory for every young asymptomatic adult. Discuss interval appendicectomy individually.

Primary references (checked 7 October 2026): WSES perforated-ulcer guidance.