Acute Appendicitis

Overview

Acute appendicitis is an acute inflammation of the vermiform (worm-like) appendix. It is mainly caused by obstruction of the lumen of the appendix by stool, infective agents or lymphoid hyperplasia. Acute appendicits is the most common abdominal surgical emergency in the world, with a lifetime risk of 6.9% in females and 8.6% in males. If left untreated, the appendix can perforate resulting in sepsis and even death.^1,2,3,4

Anatomy

• Attached to the cecum
• Intraperitoneal organ
• Midgut structure
• Located in the Right Lower Quadrant of the abdomen
• McBurney’s point: superficial location of appendix – 2/3 of the distance from the navel (belly button) to the Right Anterior Superior Iliac Spine

Arterial supply

• Abdominal aorta -> Superior Mesenteric artery -> Ileocolic artery -> Appendicular artery

Venous drainage

• Appendicular vein -> Ileocolic vein -> Superior Mesenteric vein -> Portal vein

Nervous supply

• Sympathetic – Superior Mesenteric plexus
• Parasympathetic – Vagus (CN X)
• Afferent – T10

Aetiology

Luminal obstruction (primary cause)

• Faecolith (hard mass of faecal matter)
• Normal stool
• Lymphoid hyperplasia
• Tumors
• Foreign bodies

Other emerging mechanisms

• Parasitic infection
• Schistosomal infection
• Neuroimmune

Pathophysiology

Luminal obstruction ➔ Inflammation➔ Enlargement ➔ Obstruction of vessels ➔ Hypoxia ➔ Mucosal ulceration➔ Bacterial invasion ➔ Perforation and sepsis

Clinical manifestation

• Abdominal pain
  • Starts as dull periumbilical pain
  • Progresses to sharp pain in Right Iliac Fossa (RIF)
• Anorexia
• Nausea and vomiting
• Fever
• Constipation or diarrhea

Examination

• Tenderness over McBurney’s point
• Rovsing’s sign: palpation of LLQ induces pain in RLQ
• Psoas sign: extension of right hip while lying on left side induces RLQ pain – due to irritation of the psoas muscle (suggests retrocaecal appendix)
• Obturator sign: RLQ pain on internal rotation of the flexed right hip – due to irritation of the obturator muscle (suggests pelvic appendix)
• Rebound tenderness (Blumberg’s sign) and abdominal guarding – suggest peritonitis due to perforated appendix

Diagnosis 

Alvarado score – for risk stratification

• A score of 7 or higher indicates high likelihood of appendicitis

Alvarado score (TRAMLINE)

• Tenderness in the right iliac fossa
• Rebound tenderness
• Anorexia
• Migration to right iliac fossa
• Leukocytosis
• I dont know –
• Nausea/vomiting
• Elevated temperature

Laboratory findings

• FBC: leukocytosis with neutrophil predominance
• CRP: elevated
• Urinalysis (to rule out genitourinary causes)
• Beta-hCG (always tested in women of childbearing age to exclude pregnancy)

Imaging

• Ultrasound (first-line): appendix >6mm in size; surrounding fat changes; possible appendicolith – appendix may not always be visualised
• CT (if ultrasound inconclusive, as it has higher diagnostic accuracy; can be used as first line in non-pregnant adults): dilated appendix; appendix wall thickness 3mm or more; periappendicular fat stranding; possible appendicolith
• MRI (preferred in pregnancy and children instead of CT to minimise radiation)

IF imaging is inconclusive: monitor WCC and CRP for 48 hours after admission, without giving antibiotics – if levels come down chances of appendicitis are low.³

Differential diagnosis

• GIT
  • Acute mesenteric adenitis
  • Gastroenteritis
  • Meckel’s diverticulitis
  • Gall stone disease
  • Chron’s disease
• Gynaecological
  • Ectopic pregnancy
  • Ovarian torsion
  • Ovarian cyst
• Urological
  • Ureteric stone
  • UTI
  • Pyelonephritis

Treatment

Uncomplicated appendicitis

• IF patient fit for surgery OR appendicolith present: supportive management (IV fluids and analgesia) and laparoscopic appendicectomy
• IF patient unfit for surgery OR no appendicolith present: supportive management and antibiotics (IV ceftriaxone and metronidazole OR IV Augmentin)

Complicated appendicitis

• Supportive management
• Laparoscopic appendicectomy
• Postoperative antibiotics (IV amoxicillin and metronidazole OR IV Pip-Taz OR IV Augmentin)

Complications and Prognosis

Complications

• Perforation (most common)
• Appendicular mass
• Appendicular abscess
• Portal Venous Thrombosis
• Liver abscess
• Bacteremia – sepsis
• Fistula
• Pyelonephritis
• PE/DVT following hospitalisation

Prognosis

• Without surgery or antibiotics: high mortality rate
• With proper management: <1% mortality
• Non-operative management: up to 40% risk of recurrence in first 5 years. ^5,6

References

1. BMJ Best Practice. Acute appendicitis 2025 [Available from: https://bestpractice-bmj-com.ezproxy.newcastle.edu.au/topics/en-gb/290.]

2. Petroianu A, Barroso TVV. Pathophysiology of Acute Appendicitis 2016 [Available from: https://www.jscimedcentral.com/public/assets/articles/article-pdf-1635934050-7440.pdf.]

3. Di Saverio S, Podda M, De Simone B, Ceresoli M, Augustin G, Gori A, et al. Diagnosis and treatment of acute appendicitis: 2020 update of the WSES Jerusalem guidelines. World Journal of Emergency Surgery. 2020;15(1):27. 

4. Körner H, Söndenaa K, Söreide JA, Andersen E, Nysted A, Lende TH, et al. Incidence of acute nonperforated and perforated appendicitis: age-specific and sex-specific analysis. World J Surg. 1997;21(3):313-7. https://doi.org/10.1007/s002689900235 

5. New England Journal of Medicine. Antibiotics versus Appendectomy for Acute Appendicitis — Longer-Term Outcomes. 2021;385(25):2395-7. https://www.nejm.org/doi/full/10.1056/NEJMc2116018?query=recirc_Semantic#ap2 

6. Ansari P. Appendicitis 2024 [Available from: https://www.msdmanuals.com/professional/gastrointestinal-disorders/acute-abdomen-and-surgical-gastroenterology/appendicitis.]