Acute Appendicitis
Background Information
Definition
Acute appendicitis refers to the acute inflammation of the appendix
Relevant anatomy: the appendix is a blind-ended, narrow tube attached to the caecum
- A midgut structure
- The tip of the appendix is highly variable in position: retrocecal (most common), pelvic, subcecal, pre-ileal, and post-ileal.
- Arterial blood supply: appendicular artery (branch of the ileocolic artery, branch of the superior mesenteric artery)
Pathophysiology
Inflammation typically occurs secondary to obstruction of the appendiceal lumen, due to: [Ref]
- Faecal obstruction (common in older adults)
- Lymphoid hyperplasia (common in children and young adults)
- Tumour (rare: ~1-2%)
- Most commonly, neuroendocrine tumours
- The risk is higher if the appendicitis is complicated
Risk Factors
Key risk factors: [Ref1][Ref2]
- Young age (peak incidence 15-19 y/o)
- Male
- Family history of appendicitis
- Low dietary fibre intake
- Recent antibiotic / probiotic use
Complications
The most important complication is appendiceal perforation (happens in~20-30% cases), which can lead to: [Ref]
- Faecal peritonitis and sepsis
- Intra-abdominal abscess
- Phlegmon (localised inflammatory mass)
Diagnosis
Clinical Features
Symptoms
Typical presentation: [Ref]
- Abdominal pain
- Worsens by movement (e.g. coughing, driving over uneven roads)
- Course of abdominal pain: initially vague, poorly localised peri-umbilical pain, then migrates to sharp, localised right iliac fossa pain over 24-48 hours (click to see rationale)
- Anorexia (common)
- Nausea (common)
- Vomiting (profuse vomiting is uncommon)
- Low-grade fever
- Constipation
A history of sudden relief of pain may indicate a perforation
Signs
Possible signs: [Ref]
| Sign | Description | Rationale |
|---|---|---|
| McBurney’s point tenderness | McBurney’s point: 1/3 of the distance along a straight line drawn from the right ASIS to the umbilicus | The McBurney’s point corresponds to the anatomical position of the appendix |
| Rovsing sign | Palpation of the left iliac fossa causes pain in the right iliac fossa) | Pressure applied at the left iliac fossa causes colon distention, causing the inflamed appendix to irritate the parietal peritoneum |
| Psoas sign | Pain on passive extension of the right hip / active flexion against resistance | Indicates irritation of the psoas muscle by an inflamed appendix, especially retrocaecal appendix |
| Obturator sign | Pain on internal rotation of a flexed right hip | Indicates irritation of the obturator internus muscle by an inflamed appendix in the pelvis |
A palpable abdominal mass may suggest an appendix mass (abscess or phlegmon)
Investigation and Diagnosis
The use of clinical scores (AIR and AAS) is recommended
- These scores are based on a combination of clinical features and blood test findings (see standard work-up)
- However, clinical scores should not be used alone to diagnose acute appendicitis in children
- Clinical scores help with risk stratification, to inform subsequent imaging and management
Laboratory tests
Perform a pregnancy test in all women of childbearing potential.
Standard work-up:
- FBC (may show neutrophil-predominant leukocytosis)
- Inflammatory markers (CRP may be raised)
- Urine dipstick (to exclude UTI and renal colic)
- Isolated leukocyte +ve is possible
Imaging
Imaging is recommended for all patients with equivocal or unclear clinical presentation where the diagnosis is uncertain after history, examination, and labs.
In young patients with a high clinical probability of appendicitis, imaging may be bypassed or minimised, but is still often done to confirm the diagnosis in practice.
The exact decision algorithm regarding when to and when not to perform imaging is complicated and depends on local protocols.
1st line imaging: ultrasound / CT abdomen [Ref]
- Typical ultrasound findings:
- A distended/enlarged blind-ending tubular structure that cannot be compressed
- Probe tenderness over the appendix (sonographic McBurney sign)
- Appendicolith
- The following inflammatory signs can also be seen:
- Increased periappendicial fat echogenicity
- Periappendicial fluid
- Typical CT finding:
- Enlarged appendix diameter with wall thickening and enhancement
- Peri-appendiceal fat stranding
- Appendicolith
- Presence of free intraperitoneal air suggests perforation
In children and pregnant women:
- 1st line: ultrasound
- 2nd line: MRI
CT should be avoided in these patients.
Management
Uncomplicated Appendicitis
1st line management: [Ref]
- Laparoscopic appendicectomy (to be performed within 24 hours), and
- Single dose of pre-operative broad-spectrum antibiotics
Conservative management (non-operative management) with IV antibiotics is a safe alternative to surgery in selected patients with uncomplicated acute appendicitis and the absence of appendicolith, usually if the patient is unfit for surgery or does not wish to undergo surgery. [Ref]
However, this approach carries the risk of appendicitis recurrence.
Conservative management is NOT appropriate for pregnant patients, they should be offered surgical management.
Laparoscopic appendicectomy offers significant advantages over open appendectomy in terms of patient outcomes. [Ref]
Complicated Appendicitis
Immediate surgical review is necessary for complicated appendicitis [Ref]
- Urgent laparoscopic appendicectomy + pre-operative prophylactic antibiotic is necessary for a perforated appendix
Routine interval appendicectomy is no longer standard practice for appendicitis with phlegmon / abscess.
If possible, early laparoscopic appendicectomy should be performed. Non-operative management with antibiotics is an alternative to surgery. If non-operative management is opted for, routine interval appendectomy is NOT recommended.
References