History

First reported in 1735 by Amyand in an appendix within an inguinal hernia sac that had been perforated by a pin!
Classic open appendicectomy first performed 1894 by McBurney
Laparoscopic appendicectomy first performed 1982

Epidemiology

Lifetime risk 8%

Pathophysiology

Appendicitis is caused by luminal obstruction, which rapidly causes a closed loop and greatly increased pressure due to continued mucus secretion and production of gas by bacteria
Progressive distension causes venous outflow obstruction, leading to first mucosal and then full-thickness ischaemia, and then perforation
Perforation usually occurs just beyond the point of obstruction, where pressure is greatest
- It can take anywhere from a few hours to a few days to perforate, but only 20% perforate in the first 24 hours, and 65% perforate after 48 hours
- Leads to either free perforation or formation of an abscess
- Abscess - acute inflammation with walled-off pus
- Phlegmon - acute inflammation in soft tissue with no loculated drainable collection
Bacterial overgrowth due to distal stasis in appendicitis means that the released inoculum of bacteria is large and variable
- Similar bacteria to that within the colon
- Infections should be considered polymicrobial - need to treat primarily gram-negatives and anaerobes

Aetiology

Obstruction can be caused by:
- Mechanical obstruction with faecalith/appendicolith due to stasis
- Lymphoid hyperplasia
- Parasitic infection (ascaris or pinworm)
  - Pinworms (Enterobius vermicularis) are the small white wriggling ones - treat with mebendazole one tablet stat and then repeat dose in two weeks, and also need to treat any household contacts
- Neoplasm (1% of acute appendicitis)
- Fruit and vegetable material
- Ingested barium
However these are not always present. Genetic factors, environmental influences, and infections may play a role.
- Twin studies suggest about 30% of variation in risk for appendicitis is from genes
- Seems to occur more often in summer
- Clusters of presentation occur, suggesting maybe infection.
- Certain bacteria, especially Fusobacterium, seem to increase the risk of perforation when present

Presentation

Classic order of symptoms
- Pain
- Anorexia/nausea/vomiting
- Tenderness
- Fever
- Leucocytosis
Atypical presentations
- Retrocaecal appendix - often subtle signs with more flank tenderness
- Pelvic appendix - suprapubic pain suggestive of UTI
- Chronic appendicitis - plausible for symptoms to wax and wane spontaneously
Pain (migratory)
- Stretch of visceral afferent fibres due to appendiceal distension, resulting in initial vague epigastric or periumbilical pain
- Once inflammation involves appendiceal serosa, the visceral peritoneum becomes involved and pain localises to RIF
Vomiting/nausea/anorexia
- Starting AFTER the pain
Local tenderness
- Can take some time to develop
- However you really do need tenderness to diagnose
- McBurney's point (one third of the distance between ASIS and umbilicus)
- More diffuse tenderness/peritonitis is suggestive of perforation
Hyperesthesia
- T10-T12 on the right
Rigidity
- Can be absent prior to perforation
Fever
- Develops some hours after pain
- If early high fevers are present, consider alternatives
Leucocytosis
Constipation or diarrhoea may or may not be present
Perforation - high fevers, high WCC, diffuse tenderness/peritonitis, systemic sepsis

Examination

Findings depend on position of appendix
Typically lie still with appendicitis
Tachycardia and fever suggest a need for intervention on the same day
Historical signs (note that these simply demonstrate localised peritonitis, not a specific disease process)
- Psoas sign: extension at the hip (for a retrocaecal appendix)
- Obturator sign (for a pelvic appendix): internal rotation at hip to maximum
  - Indicative of irritation of obturator internus - pelvic appendicitis and concerning for abscess
- Rovsing sign - RLQ pain elicited by LLQ palpation
Check for RIF mass with delayed presentations

Investigation

Bloods
- Leucocytosis is present in 90% of cases, often with a left shift (predominance of neutrophils and sometimes an increase in band forms)
  - Therefore 10% of cases have a normal neutrophil count
  - Mean WCC is higher with perforated or gangrenous appendicitis
- Mild elevation of bilirubin is 86% specific for perforation (UTD)
- CRP <10 is 85% sensitive at admission and nearly 100% sensitive at 48 hours after symptom onset
Urine
- Dipstick - trace leucs are found commonly, and presumably secondary to direct irritation of the bladder
- Pregnancy testing mandatory for women of childbearing age
AXR - might see a calcified appendicolith, but not much else (pneumoperitoneum is rare even with perforation)
USS 0.86/0.81 for se/sp
- Primary sign - enlarged, immobile, and non-compressible
- Secondary signs - free fluid, hyperaemia of adjacent bowel loops, induration of mesenteric fat, and regional adenopathy
CT with IV contrast
- Best used for equivocal cases
- Sensitivity 76-100%
- Specificity 83-100%
- Look for an appendix >7mm in diameter with a thickened, inflamed wall and mural enhancement/target sign
- If the appendix is not visualised, the absence of inflammatory findings is also quite sensitive to exclude appendicitis
MRI equivalent to CT
- Typically used for pregnant patients
- No contrast necessary
- Sensitivity 97%, specificity 95%

Scoring systems

Alvarado score is the best
Not particularly specific to rule appendicitis in, but a score <4 is 96% sensitive to rule appendicitis out

Differential diagnosis:

Women:
- Ovarian torsion - simultaneous onset of pain and vomiting, severe pain, non-migratory. Fever and leucocytosis would be a late sign, associated with necrosis.
- Ovarian cyst rupture - free fluid, midcycle sudden onset pain, often during sexual intercourse, vomiting less common
  - Mittelschmerz: almost precisely midcycle. Typically mild and unilateral pain, which lasts for a few hours to a few days.
  - Corpus luteum cyst: at time of menstruation
  - Cysts may not be seen on ultrasound after rupture!
- Tubo-ovarian abscess/PID
  - Less likely to have migratory pain
  - Less association with vomiting
  - Often bilateral
  - Vaginal discharge
  - Cervical motion tenderness may also be seen in appendicitis
- Ruptured ectopic - pain sudden, palpable mass, a/w anaemia and shock
- UTI
- Endometriosis - chronic deep pelvic pain and dyspareunia which typically occurs with menstruation or ovulation.
- Ovarian hyperstimulation syndrome
Crohn's - look for a history of previous attacks, palpable mass, thin patient. Suspect in ongoing post-op pain with a histologically normal appendix.
Pyelonephritis - expect earlier and higher fever, dysuria/frequency, softer abdomen
- Perinephric abscess
- Nephrolithiasis
Mesenteric adenitis - commonly seen in children after an acute viral illness. Shouldn't have much systemic features, not much tenderness/guarding, and not much vomiting. May see evidence of viral infection on blood tests.
- Also discussed under 'mesenteric diseases'
Gastroenteritis - this is actually somewhat rare - consider if nausea/vomiting/diarrhoea predominate, there are sick contacts, and/or there is minimal tenderness
- Most commonly Yersinia, Salmonella or Campylobacter
- Commonly with yersiniosis - will see a normal appendix but surrounding inflammation and lymphadenopathy
Intussusception
Meckel diverticulitis
Testicular torsion
Diabetic ketoacidosis
Right-sided diverticulitis
- Past history diverticulitis, longer onset to presentation (2 days), lower WCC, higher CRP, less n/v and anorexia
Colon cancer
Typhlitis (right-sided colitis in neutropaenic patient)

Management

Approach

Alvarado score <5: discharge and monitor at home
Score 5-8: Admit for imaging or observation
- If remaining equivocal after imaging/observation, diagnostic laparoscopy
Score 9-10: operate

Acute uncomplicated appendicitis = appendicitis without clinical or radiological evidence of perforation (i.e. phlegmon, inflammatory mass, abscess)

Gold standard - laparoscopic appendicectomy
- Can be safely delayed 24 hours with no increase in perf rate
- Should happen in first 48 hours of presentation
- Lap vs open - lap has lower rates of wound infection and faster mobilisation
Antibiotics - cease at operation
- However, some evidence suggests continuing for two doses post-op, which has reduced SSI in an RCT (Are Postoperative Intravenous Antibiotics Indicated After Laparoscopic Appendicectomy for Simple Appendicitis? A Prospective Double-blinded Randomized Controlled Trial)
- Evidence for 24 hours IV Abx in gangrenous appendicitis, but probably don't need more (UTD 2024)
Non-operative management
- There is some evidence for non-op management with ABx, but unconvincing currently. Questions around patient selection, recurrent attacks, missed neoplasm.
- Most patients respond clinically (improved symptoms and bloods)
- 10% require rescue appendicectomy
  - No way to predict this 10%
- One-year recurrence rate of 25%
- Five-year recurrence rate of 40% (APPAC trial, Finland, 2015), and the presence of appendicolith makes this more likely
- Consider as safe alternative if surgery not possible
  - Prohibitive anaesthetic risk
  - Unable to operate immediately due to anticoagulation
  - Patient does not want operation
  - Improving symptoms already
  - Morbidly obese and mild symptoms
  - Pregnant women in first trimester with mild appendicitis
  - Radiological appendicitis without systemic inflammation and minimal local signs

Acute perforated appendicitis, or delayed presentation with diffuse peritonitis

Emergency appendicectomy after resuscitation
Drainage/irrigation
Probably doesn't need a drain
Beware of wound infection - use interrupted sutures, or consider delayed closure after two days
Post-op antibiotics - total of 5 days IV + oral - use tazocin/IV augmentin with a switch to PO augmentin (or bactrim + metronidazole if allergic)
- Temp < 38 for 24 hours, tolerating diet, mobilising, only PO analgaesia = downgrade to PO Abx
- Gangrenous appendicitis without pus does not require much post-op ABx
Ileus is very likely - start low with diet and upgrade only as needed
Will often need to stay in hospital for 5-7 days until they tolerate regular diet

Delayed presentation

Appendiceal abscess
- IV antibiotics and drainage
  - Radiologic drainage if feasible - leave drain in for 4-7 days
  - Consider trans-rectal or trans-vaginal approaches
  - If radiologic not feasible, may need laparoscopic drainage, depending on progress - suction, wash, leave a drain
Phlegmon or abscess too small to drain
- IV antibiotics 4-7 days
- Surgery will be tough technically - high risk for ileocaecectomy, abscess/fistula, and failure to identify the appendix - better to wait
- Treatment failure necessitates rescue appendicectomy

'Chronic appendicitis'

If any radiographic suggestion of recurrent mild appendicitis, can offer elective appendicectomy
If pain is non-specific and no radiographic evidence, refer to gastroenterology and gynaecology, and typically do not offer elective appendicectomy. However, if a diagnostic lap is performed to investigate or exclude another disease, appendicectomy can be performed at that time.

Incidental appendicectomy (i.e. performed at time of another procedure for an asymptomatic normal appendix)

Not recommended
Increased morbidity and mortality
Appendix may have a role in regulating colonic flora

Follow-up of non-operative cases

Interval appendicectomy
- Controversial - 8% risk of recurrent appendicitis at 8 years in children
- Sabiston suggests only for those who have appendicoliths or those who actually get recurrent appendicitis
Colonoscopy
- Sabiston suggests colonoscopy in all adults managed non-operatively
- UTD says colonoscopy for those >40yo
- Especially with abscess or unusual imaging findings, or high-risk features for cancer
- However this is controversial - some surgeons disagree that it is necessary
- Cancer or IBD will be found in 2%

Unexpected operative findings:

Normal appendix
- Operative steps:
  - Examine terminal 60cm of ileum (Meckel's, ileitis, mesenteric adenitis)
  - Uterine adnexa (TOA, ovarian torsion, endometriosis, ruptured ovarian cyst)
  - Sigmoid colon (diverticulitis)
  - Gallbladder
  - Duodenum
  - Remove the normal appendix if nothing else found (unless the base appears friable because of another disease)
- Potential causes:
  - Meckel's
  - Terminal ileitis
  - Caecal or sigmoid diverticulitis
  - Perforating colon cancer
  - Ovarian/uterine/fallopian pathology
  - Mesenteric adenitis
Appendiceal neoplasm
- See separate topic
- Right hemicolectomy if lesion >2cm, or base of appendix, or mesoappendix is involved

Appendicitis in the elderly

Impaired immunologic and inflammatory response
More likely to present with perf (overall perforation rate is 40-70%), because symptoms are a bit more variable
If diffuse peritonitis is present in an unstable elderly patient, consider laparotomy instead of laparoscopy
Otherwise, laparoscopy is safe
Open appendicectomy can be performed under spinal if the pulmonary risk is prohibitive for GA

Appendicitis in pregnancy

Most common surgical pathology of pregnancy - 1/1500 confirmed appendicitis
Progresses more quickly - immunosuppression of pregnancy
Atypical presentation in 40-50% of patients
- Emesis, migratory RIF pain, rebound tenderness, elevated Alvarado score were all useful indicators
  - Nausea/vomiting common in pregnancy
  - Mild leucocytosis is normal in pregnancy
  - Mild elevation in CRP is normal in pregnancy
- One study from AJ Surgery reported a sensitivity of 100% in 164 patients for left shift and neutrophils >70%
- Uncommon in first and third trimester - 50% of cases occur in second trimester
- DDx UTI/pyelo, hydronephrosis, degenerative uterine fibroids, ligamentous pain, ectopic ruptured, ovarian torsion (most common in first trimester), ovarian hyperstimulation syndrome
Differential diagnosis
- Ectopic
- Torsion
- Ovarian cyst accident
- Placental abruption (generalised pain, PV bleeding)
- Uterine rupture (previous surgery)
- Pre-eclampsia/HELLP (usually RUQ pain)
Routine imaging is recommended
- Use USS/MRI (without contrast) to diagnose
- USS is most useful in first trimester - after that, very rarely able to see it, and se/sp <70%
- MRI:
  - Use T2 phase - will be darkish tubular structure
  - Gradient Echo phase or DWI are the other useful phases
  - Should be able to see oedema and stranding if it's present
  - On DWI, inflammation shows as quite bright
  - Don't mistake the ureter and ovarian vein lying on top of psoas for the appendix
  - MRI sensitivity 92% (maybe a bit more)
Can potentially use low-dose CT, but, uh, hmm
- Theoretically 1 in 500 fetuses will develop cancer because of this dose, and riskiest time is between 8 to 15 weeks
- However in one study it reduced the negative appendicectomy rate from 32% (with USS) to 8%
Management
- Unwell patients with O+G dx excluded can be taken to OT without confirmatory imaging
- Well and likely appendicitis with O+G dx excluded can also go to OT without imaging confirmation if there are delays - constantly reassess timing
- If well, and unlikely/possible appendicitis, image
- Laparoscopic is the preferred technique, but open can be used
- Cut-down 2cm above uterine fundus is a safe way to do it
- Lowest effective intra-abdo pressure
- Minimise head down
- Indomethacin PR if suggested by O+G
Prognosis
- Uncomplicated appendicitis a/w 3-5% fetal loss
- Complicated appendicitis leads to pre-term labour in 11% and fetal loss in 36%
- Negative appendicectomy also likely leads to risk of pre-term labour and fetal loss, although this risk may be overstated

Appendicitis in the immunocompromised patient

Can fail to mount a proper immune response - no fever, leucocytosis or peritonitis
Consider typhlitis

Appendiceal mucocele (on CT)

Note that mucocoele is an imaging finding, not a histologic finding any more
This finding can occur due to chronic obstruction and distension (due to continued mucin secretion), without any neoplastic findings on histology. Normal epithelium with no dysplasia.
No known risk for transformation to malignancy
Risk factors for neoplasm on CT:
- Larger lesion (diameter >13mm)
- Isolated focal distal dilation with normal appendix proximally
- Mural curvilinear calcifications, especially eggshell in appearance
- Diameter >2cm
- Absence of peri-appendiceal stranding
- Increase in wall thickness is not associated with neoplasm
What to do:
- If operation can be performed laparoscopically and cancer doesn't involve the base of the appendix, go ahead
- Ensure mesoappendix is excised
- Evaluate all regions in the abdomen
- Generous biopsy of one or two peritoneal implants, if present
- If no dysplasia on histology, simple resection is curative and no further follow-up is required