Acute Appendicitis

Acute appendicitis is inflammation of the vermiform appendix. It is the commonest cause of acute surgical abdomen, with a lifetime risk of about 7 to 9% and a peak incidence between ages 10 and 30 (in the second and third decades).

Luminal obstruction is the usual cause: faecolith, lymphoid hyperplasia, tumour, parasites, or foreign body. Bacterial overgrowth and raised intraluminal pressure follow, then venous and arterial compromise, ischaemia, necrosis, and perforation.

Perforation rates are about 15 to 20% overall, rising to 50 to 70% in the elderly and in infants. Mortality is below 0.1% in uncomplicated disease and 1 to 5% or higher with perforation in the elderly.

Pathology: obstruction, distension, and mucosal ischaemia in 24 to 36 hours, with perforation typically after 36 to 72 hours of symptoms. Microbiology is polymicrobial: Escherichia coli, Bacteroides fragilis, Streptococcus milleri group, Enterococcus, Pseudomonas, and Klebsiella.

Classification:

• Uncomplicated (simple) appendicitis: inflamed but not perforated, without abscess or phlegmon
• Complicated appendicitis: gangrenous, perforated, with periappendiceal abscess or phlegmon, or generalised peritonitis

Anatomical variation (retrocaecal about 65%, pelvic about 30%, and others such as pre-ileal, post-ileal, subcaecal and paracolic) changes the presentation.

Classic sequence (about 50% of patients): vague periumbilical (visceral) pain, followed by anorexia, nausea and vomiting, then migration of pain to the right iliac fossa (parietal peritoneal irritation) within 6 to 24 hours, with low grade fever (37.5 to 38.5 degrees C). Pain is aggravated by movement, coughing, and walking.

Signs:

• Tenderness maximal at McBurney point (one third of the way from the anterior superior iliac spine to the umbilicus), guarding, and rebound tenderness
• Rovsing sign (palpation of the left iliac fossa causes right iliac fossa pain), psoas sign (pain on extending the right hip, retrocaecal), obturator sign (pain on internal rotation of the flexed hip, pelvic), and Dunphy sign (pain on coughing)
• Rectal examination: pelvic tenderness; peritoneal irritation in pelvic appendicitis
• Generalised peritonitis, rigidity and shock after perforation; palpable mass with phlegmon or abscess (usually after 3 to 5 days)

Atypical presentations: retrocaecal (flank pain, minimal peritonism, haematuria or pyuria from ureter irritation), pelvic (diarrhoea, urinary frequency, suprapubic pain), pregnancy (upward and lateral displacement of the appendix; pain may be in the right flank), elderly (vague symptoms, late presentation, high perforation), and immunosuppressed (muted signs).

Differential diagnosis: mesenteric adenitis (more common in children), terminal ileitis (Crohn disease, Yersinia), caecal diverticulitis, right sided colonic pathologies, ovarian pathology (cyst rupture, torsion), ectopic pregnancy, pelvic inflammatory disease, renal colic, urinary tract infection, testicular torsion, and gastroenteritis.

Scores help stratify risk: Alvarado (migration of pain, anorexia, nausea or vomiting, tenderness in the right iliac fossa, rebound, elevated temperature, leukocytosis, and left shift; score of 7 or more suggests appendicitis, 5 to 6 equivocal, 4 or below low risk) and the Appendicitis Inflammatory Response (AIR) score, with higher specificity.

Laboratory: leucocytosis (above 10,000 to 12,000 per microlitre) in about 80 to 85%, neutrophilia, and C-reactive protein (a combination of normal white cell count and CRP has a negative predictive value above 95%). Urinalysis to exclude urinary tract infection and stones (though pyuria can occur in appendicitis). Pregnancy test in women.

Imaging:

• Ultrasound (graded compression): non-compressible blind ending tubular structure, diameter at least 6 mm, wall thickening, appendicolith, peri appendiceal fluid and echogenic fat; sensitivity 75 to 90%, operator dependent. First line in children, young women, and pregnancy
• CT abdomen and pelvis with intravenous contrast: sensitivity and specificity about 95% and 94%. Findings: appendix over 6 mm, wall enhancement, periappendiceal fat stranding, appendicolith, abscess, phlegmon, and free fluid. Low dose CT is acceptable in adults and recommended in adults with equivocal presentation
• MRI: for pregnant women (sensitivity and specificity above 90%), after inconclusive ultrasound
• Diagnostic laparoscopy: can be diagnostic and therapeutic, particularly in women of reproductive age with uncertain diagnosis

Resuscitation. Fluids (balanced crystalloid), analgesia (IV paracetamol, NSAID, morphine as needed; analgesia does not mask the diagnosis), antiemetics, nil by mouth.

Antibiotic strategy.

• Preoperative single dose for uncomplicated appendicitis: cefazolin 2 g IV (3 g if over 120 kg) with metronidazole 500 mg IV, or cefoxitin 2 g IV, or ceftriaxone 2 g with metronidazole. Give within 60 minutes before incision. No postoperative antibiotics are required after appendicectomy for simple (non-perforated) appendicitis
• Perforated or gangrenous appendicitis: piperacillin tazobactam 4.5 g IV every 6 to 8 hours, or ceftriaxone 2 g daily with metronidazole 500 mg every 8 hours. Continue for 3 to 5 days postoperatively. Four days with adequate source control is non-inferior to longer courses; stop when afebrile with normal white cell count and tolerating diet. Ertapenem 1 g daily is an alternative
• Penicillin allergic patients: ciprofloxacin 400 mg IV twice daily plus metronidazole, or gentamicin 5 mg/kg daily with metronidazole

Appendicectomy. This is the standard treatment for most patients. Perform it as soon as practical, typically within 12 to 24 hours of diagnosis for uncomplicated disease. Delays up to 24 hours do not increase perforation significantly.

Laparoscopic appendicectomy is preferred over open. It brings lower wound infection, less pain, faster return to activity, and a diagnostic advantage in uncertain cases and women. Open surgery is used for conversion, large abscess, or limited resources.

Technique: three port laparoscopy, mesoappendix ligation with energy device or clips, stapler or endoloop to the appendix base, and retrieval in a bag. In perforation, irrigate or aspirate purulent fluid (routine lavage has no advantage).

Remove a normal looking appendix when no other pathology is found in a patient with right iliac fossa pain. This is conventional practice, since up to 20 to 30% of macroscopically normal appendices are inflamed on histology.

Non-operative management (antibiotics only). In uncomplicated appendicitis confirmed on CT, antibiotic therapy alone has a success rate of about 70 to 75% at 1 year. About 25 to 30% need appendicectomy within 1 year, and a minority of these have complicated disease. Overall complication rates are lower, but recurrence is a risk.

It is appropriate for selected motivated patients without appendicolith, perforation or abscess. A typical regimen:

• Ertapenem 1 g IV daily (or cefoxitin or ceftriaxone with metronidazole) for 24 to 48 hours
• Then oral antibiotics to complete 10 days: amoxicillin clavulanate 875/125 mg twice daily or moxifloxacin 400 mg daily (or ciprofloxacin with metronidazole)

Appendicolith presence increases failure rates (about 40 to 50%). Counsel patients about recurrence and the small risk of missed neoplasm. Interval appendicectomy is not routine after successful non-operative treatment of an uncomplicated case. Older patients (over 40 to 50) should be considered for colonoscopy or imaging.

Appendiceal mass (phlegmon) or abscess.

• Phlegmon without a drainable collection: conservative management with IV antibiotics, fluids, bowel rest, and serial examination (the Ochsner-Sherren regimen). Failure shows as rising fever, spreading pain, or increasing mass
• Abscess: percutaneous drainage under ultrasound or CT guidance (for collections over 3 to 4 cm) with antibiotics, or surgical drainage if inaccessible. Interval appendicectomy at 6 to 12 weeks is selective. In patients over 40 years, colonoscopy and CT exclude neoplasia (caecal carcinoma, appendiceal neoplasm, Crohn disease)

Perforation with generalised peritonitis. Resuscitate, give broad spectrum antibiotics, and perform emergency laparoscopic or open appendicectomy with peritoneal toilet. Leave a drain only for a localised, residual abscess.

Special populations.

• Pregnancy: ultrasound and MRI. Laparoscopic appendicectomy has acceptable fetal outcomes in all trimesters, with fetal loss about 3 to 5% in simple and about 20 to 35% in perforated disease. Early surgery is important
• Elderly: lower threshold for CT, because delay and perforation are common; consider carcinoma
• HIV and immunosuppression: higher complication rates; consider neutropenic enterocolitis

Complications. Surgical site infection (about 3 to 10% in open surgery, 1 to 3% in laparoscopic surgery), intra abdominal abscess (up to 15 to 20% after perforation), ileus, stump leak or appendiceal stump appendicitis, adhesive obstruction, pylephlebitis, incisional hernia, and, rarely, faecal fistula.

Histology. Always send the specimen for histology, because 1 to 2% have neoplasms (carcinoid or neuroendocrine tumour, mucinous neoplasm, adenocarcinoma). Tumours over 2 cm, at the base, or with high risk features need right hemicolectomy.