Appendicitis

Introduction

Lifetime risk 12% for males and 25% for females
Most common at 10-19yo
Most frequent cause of atraumatic abdominal pain in children >1yo
Most common non-obstetric surgical emergency in pregnancy (1/1500 pregnancies)
- However, not more common in pregnancy than non-gravid

Pathophysiology

Causes
- Faecolith obstruction
- Obstruction by lymphatic tissue, gallstone, tumor or parasite
- Raised intraluminal pressure leads to appendiceal vascular insufficiency, bacterial proliferation, inflammation and ultimately perforation
50% of patients have an atypical presentation due in part to anatomic variation
Retrocaecal appendix can cause RUQ or pelvic pain
Malrotation of the colonc results in pain in LUQ
Gravid uterus may lead to RUQ tenderness
- However RIF pain and tenderness is still the most common site in pregnancy

Clinical features

Initial non-specific malaise, fatigue, indigestion or bowel irregularity
Anorexia is common but not universal
Followed by periumbilical abdominal pain
If nausea develops, typically follows the onset of pain
Subjective or objective fever is frequent
Discomfort then migrates to right iliac fossa and flank pain/dysuria/haematuria can all occur
No evidence that PR adds information
Psoas sign – Pain in abdomen with extension of right leg in left lateral position
Obturator sign – Pain with internal rotation of right thigh at the hip

Clinical features

Abdominal rigidity, positive psoas sign, fever or rebound tenderness all increase the likelihood of acute appendicitis
Previous episodes of similar pain, absence of RLQ pain, absence of classic migration make appendicitis less likely
Presence or absence of any exam finding in isolation is not sensitive or specific enough to rule in/out appendicitis
In children <18yo
- Fever +LR 3.4; -LR 0.32
- Rebound and pain migration also strong predictors
In adults
- RLQ pain +LR 7.31; -LR 0.28
- Rigidity and migration of pain next most important
- Fever +LR 1.94 and –LR 0.58

Differential Diagnosis

Caecal/Meckel’s diverticulitis
Cecal volvulus
Colitis/terminal ileitis
Constipation/ileus/bowel obstruction
Crohn’s/UC
Epiploic appendigitis
- Appears as fatty centre (Black) with halo of inflammatory fat stranding
Incarcerated inguinal hernia
Intra-abdominal abscess
Intussusception
Malrotation
Mesenteric lymphadenitis
GU – Ectopic pregnancy, ovarian torsion, ovarian vein thrombosis, pyelonephritis, referred testicular pain, renal colic, tubo-ovarian abscess
Psoas abscess
Abdominal wall haematoma

Diagnosis

Consider in any atraumatic right-sided, periumbilical or flank pain in someone who still has an appendix
Diagnostic imaging should be considered in atypical presentations or if significant diagnostic uncertainty remains
Scoring systems
- Modified Alvarado (MANTRELS)
  - Low-risk score 72% sensitive compared to 93% for clinical judgement
  - Not useful

Alvarado score

Alvarado score

Score of 0-3: Unlikely to have appendicitis
Score of >= 4: Evaluate further (surgical evaluation or imaging)
Low score <4 has more diagnostic utility than high score >= 7 to ’rule in’ diagnosis (specificity only 81%)

Diagnosis

Lab tests
- Acute appendicitis most common diagnosis in children >4 with atraumatic abdominal pain and leukocytosis
- WCC does not distinguish between simple and perforated appendicitis
- Raised WCC and/or CRP has sensitivity as high as 98%
  - Normal values of both with low pre-test probability make acute appendicitis unlikely
  - Not so useful if differential diagnosis is broad
Imaging
- Obtain early surgical consultation before imaging in straightforward cases in adults
- In children, some centres prefer paediatric consult prior to ionising radiation

Ultrasound

Graded compression USS is the initial imaging modality of choice in pregnant females and children
Also can be considered in young, non-obese adults
Normal – Should be compressible with maximal diameter 6mm, absent peristalsis and lack of change in configuration over time
Positive – Typical findings are thickened, non-compressible appendix >6mm in diameter
In children, good to rule in appendicitis but hard to rule out
Perforation may lead to difficult visualisation and loss of specific imaging hallmarks
Pelvic USS can be useful if differential includes pelvic pathologies

Abdominopelvic CT

For most adult males and non-pregnant females in whome diagnosis is not clear
Typically dilated appendix >6mm diameter with thickened wall, periappendiceal inflammation and appendicolith or abscess visualisation
Perforation may make diagnosis difficult on CT
Sensitivity >94% with PPV >95%
vs. US sensitivity 86% with 95% PPV
Contrast
- Non-enhanced CT has excellent performance for diagnosis of appendicitis and can significantly reduce the time of studies and avoid risk of nephrotoxicity
- Sensitivity remains 93% with PPV >92%
- Intra-peritoneal fat serves as an intrinsic contrast medium, so lack of this in skinny individuals may affect imaging interpretation

MRI

Particularly useful in pregnant women
IV gadolinium is not used in pregnancy as crosses placenta and has teratogenic effects in animal studies
- Also not given in renal disease as can cause nephrogenic fibrosing dermopathy

Treatment

NBM, fluids, analgesia, antiemetics
Perioperative antibiotics upon diagnosis or signs of peritonitis
Triple Ab’s
Appendicectomy
CODA Trial
- 1552 patients were randomised to antibiotics vs. appendicitis
- Antibiotics deemed non-inferior to surgery on the basis of 30-day quality of life scores
- 1/3 of patients in the antibiotics group underwent appendectomy at 90 days, 41% of those with appendicolith vs. 25% of those without
- Those with an appendicolith were more likely to suffer serious adverse events with an antibiotics-only approach including perforation at time of appendicectomy and potential for missed cancer diagnoses

Disposition

Extended observation in ED or hospital if not clear
Stable, reliable patients without significant comorbidities can be discharged for follow-up within 12 hours

Complications and pregnancy

Perforation most common in children under 5, the elderly and the pregnant
Rupture is more common in pregnant females (60% risk if gravid vs. 20% risk if not pregnant) – 3x higher
Risk of perforation highest in 2^nd and 3^rd trimesters most likely due to gravid uterus preventing omental walling-off of infection
Frequently delayed diagnosis in pregnancy also as nausea/vomiting/leukocytosis put down to pregnancy + lack of peritoneal signs due to stretch
USS
- Just as sensitive in pregnancy (67-100% vs. 86% in non-pregnant)
- Equally specific at 96%
Pregnancy-specific complications include miscarriage, premature labor and fetal death (1-5% of uncomplicated vs. 30% of complicated cases)

Last Updated on March 27, 2024 by Andrew Crofton

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