Appendicitis

Overview

Appendicitis is acute inflammation of the vermiform appendix and represents the most common cause of emergency abdominal surgery worldwide. It affects approximately 7–8% of the population at some point in life, with peak incidence in the second and third decades.

Pathophysiology

The central mechanism is luminal obstruction of the appendix, most commonly by:

Faecolith (hardened stool) — most frequent cause
Lymphoid hyperplasia (especially in children, following viral infections)
Tumours, foreign bodies, or parasites (less common)

Obstruction leads to bacterial overgrowth, mucosal ischaemia, transmural inflammation, and, if untreated, perforation (typically within 24–72 hours of onset).

Clinical Presentation

Feature	Detail
Pain	Classically periumbilical at onset, migrating to right iliac fossa (RIF) over 6–12 hours
Anorexia	Nearly universal — its absence should raise doubt
Nausea/vomiting	Common, usually follows onset of pain
Fever	Low-grade (37.5–38.5°C); high fever suggests perforation
Diarrhoea/urinary symptoms	Possible if appendix is pelvic or retrocaecal

Key Examination Signs (Bailey & Love's, p. 1360)

McBurney's point tenderness — maximum tenderness 1/3 of the way from ASIS to umbilicus
Rovsing's sign — palpation in LIF causes pain in RIF
Psoas sign — extension of right hip causes pain (retrocaecal appendix)
Obturator sign — internal rotation of right hip causes pain (pelvic appendix)
Rebound tenderness / guarding — suggest peritoneal irritation
Pointing sign — patient points to where pain started and migrated

Diagnosis

Laboratory

WBC: Elevated (>10,000/mm³) in ~80% — left shift (neutrophilia) is characteristic
CRP: Elevated; rises later but useful in delayed presentations
Urinalysis: May show mild pyuria/haematuria (do not exclude appendicitis)
β-hCG: Must be checked in women of reproductive age (to exclude ectopic pregnancy)

Clinical Scoring Systems

Score	Components	Interpretation
Alvarado (MANTRELS)	Migration of pain, Anorexia, Nausea/vomiting, Tenderness RIF, Rebound, Elevated temp, Leukocytosis, Shift to left	≥7 = likely appendicitis
Appendicitis Inflammatory Response (AIR)	Similar with CRP added	More validated in adults
pAAS	Paediatric variant

Imaging

Modality	Findings	Use
Ultrasound	Non-compressible appendix >6 mm diameter, faecolith with posterior acoustic shadowing, periappendiceal fluid	First-line (no radiation); operator-dependent
CT abdomen/pelvis	Dilated appendix with wall enhancement, faecolith, periappendiceal fat stranding	Gold standard; sensitivity ~98%
MRI	Similar to CT without radiation	Preferred in pregnancy

CT and Ultrasound findings in acute appendicitis — composite showing POCUS with hypoechoic muscularis and hyperechoic faecolith (left), and axial CT demonstrating dilated enhancing appendix with hyperdense faecolith (right)

Composite image: (A) POCUS showing non-compressible, thickened appendix with intraluminal faecolith and periappendiceal fluid. (B) Axial CT confirming dilated appendix with wall enhancement and hyperdense faecolith anterior to the psoas muscle.

Differential Diagnosis

Women: Ovarian cyst/torsion, ectopic pregnancy, PID, Mittelschmerz
Men/Children: Mesenteric adenitis, Meckel's diverticulitis, intussusception
All ages: Right ureteric colic, Crohn's disease, caecal carcinoma, psoas abscess, right-sided diverticulitis

Management

Preoperative Preparation (Bailey & Love's, p. 1365)

IV fluids (target adequate urine output)
IV antibiotics covering Gram-negative bacilli + anaerobes (e.g., ceftriaxone + metronidazole)
VTE prophylaxis (mechanical ± pharmacological)
Single perioperative dose of antibiotics reduces wound infection in uncomplicated cases

Surgical Treatment

Appendicectomy is the definitive treatment — laparoscopic preferred (shorter hospital stay, less wound infection, faster recovery)
Open appendicectomy remains valid when laparoscopy is unavailable or contraindicated
In perforated appendicitis: therapeutic antibiotics, thorough washout; drain placement controversial

Non-operative Management

Select uncomplicated cases (no perforation, no faecolith, low-risk patients) may be managed with IV antibiotics alone (e.g., ertapenem or ceftriaxone + metronidazole for 24–48h then oral step-down)
Recurrence rate ~20–35% at 5 years; patients must be counselled appropriately
Not appropriate for perforated appendicitis or appendiceal mass

Complicated Appendicitis (Abscess/Phlegmon)

Appendiceal phlegmon: IV antibiotics first; interval appendicectomy at 6–8 weeks (debated)
Appendiceal abscess: Percutaneous drainage + antibiotics; interval appendicectomy

Complications

Complication	Notes
Perforation	~20–30% at presentation; higher in extremes of age
Peritonitis	Local or generalised; requires urgent surgery
Appendiceal abscess/phlegmon	Walled-off infection
Portal pyaemia / liver abscess	Rare but serious
Post-op wound infection	Most common surgical complication
Stump appendicitis	Rare recurrence in residual stump after appendicectomy

Special Populations

Children: Perforation rates higher (thin appendiceal wall, delayed diagnosis); mesenteric adenitis is a common mimic
Elderly: Atypical presentation common; higher perforation and mortality rates
Pregnancy: MRI preferred for imaging; appendix displaced superiorly by gravid uterus; higher risk of preterm labour post-operatively
Immunocompromised: May lack classic inflammatory signs; high index of suspicion required

Prognosis

Uncomplicated appendicitis treated promptly: mortality <0.1%
Perforated appendicitis: mortality rises to 1–5%, higher in elderly
Laparoscopic appendicectomy is associated with faster return to normal activity and lower wound infection rates compared to open surgery

This is a shared conversation. Sign in to Orris to start your own chat.