Acute Appendicitis

Acute appendicitis is inflammation of the vermiform appendix, usually triggered by luminal obstruction with progressive mural oedema, bacterial proliferation, venous congestion and, in advanced disease, ischaemia, gangrene and perforation.

The clinically useful division is:

• Uncomplicated appendicitis: inflamed appendix without gangrene, perforation, abscess or phlegmon.
• Complicated appendicitis: gangrene, perforation, periappendiceal abscess, inflammatory phlegmon or generalised peritonitis.

Appendicectomy remains definitive treatment. Antibiotic only treatment can be considered in carefully selected uncomplicated disease, particularly when there is no appendicolith, but recurrence and later appendicectomy remain significant. SAGES currently conditionally favours operative treatment for both uncomplicated and complicated appendicitis.

Classically, pain begins centrally or around the umbilicus and migrates to the right iliac fossa as inflammation reaches the parietal peritoneum.

Typical presentation:

• Progressive right lower quadrant pain
• Anorexia, nausea and usually limited vomiting
• Low grade fever
• Localised right iliac fossa tenderness and guarding
• Pain worsened by movement, coughing or percussion

Rovsing, psoas and obturator signs may support the diagnosis but have limited sensitivity and should not determine management in isolation.

Anatomical position alters presentation. A retrocaecal appendix may produce flank or back pain with minimal anterior guarding. A pelvic appendix may cause suprapubic pain, diarrhoea, urinary frequency or tenesmus.

Complicated disease should be suspected with diffuse peritonism, persistent tachycardia, high fever, sepsis, marked inflammatory response, prolonged symptoms, palpable inflammatory mass or haemodynamic deterioration.

Older patients may have little fever or guarding despite perforation. Children, particularly younger children, have higher rates of delayed diagnosis and perforation.

• Diagnosis combines clinical probability, inflammatory markers and selective imaging.
• Obtain full blood count, C reactive protein, renal function and electrolytes. Perform urinalysis and pregnancy testing where applicable. Lactate, blood gas, coagulation profile, group and save and blood cultures are added when sepsis, shock or major physiological disturbance is present.
• Leukocytosis, neutrophilia and elevated C reactive protein support the diagnosis but normal values, particularly early in the illness, do not exclude appendicitis.
• Clinical scores are best used for risk stratification rather than definitive diagnosis.

The Appendicitis Inflammatory Response score incorporates symptoms, examination, white cell count, neutrophil proportion and C reactive protein. Intermediate probability patients benefit most from imaging and serial assessment.

Imaging

Contrast enhanced computed tomography of the abdomen and pelvis is the most definitive practical test in nonpregnant adults when imaging is required. Typical findings are an enlarged noncompressible appendix, mural thickening and enhancement, periappendiceal fat stranding and local fluid. An appendiceal diameter above 6 mm supports the diagnosis only when accompanied by inflammatory changes.

Features suggesting complicated disease include:

• Extraluminal gas or appendicolith
• Periappendiceal abscess
• Wall discontinuity or poor enhancement
• Marked surrounding inflammatory change
• Free fluid with perforation

Ultrasound is preferred first in children and is useful in pregnancy. Failure to visualise the appendix is nondiagnostic rather than negative.

Magnetic resonance imaging is preferred after equivocal ultrasound in pregnancy where available. CT and MRI remain the most definitive imaging modalities.

Imaging should not delay operative source control in a deteriorating patient with convincing generalised peritonitis.

Important mimics include terminal ileitis, Crohn disease, caecal diverticulitis, ureteric colic, pyelonephritis, ectopic pregnancy, ovarian torsion, pelvic inflammatory disease and Meckel diverticulitis.

Initial management is simultaneous with surgical assessment.

• Keep fasting when surgery is likely.
• Establish intravenous access and correct dehydration with isotonic crystalloid, reassessing after each bolus.
• Give early analgesia. Paracetamol 1 g orally or IV every 6 to 8 hours is reasonable in adults, maximum 4 g daily in patients without relevant hepatic risk. Severe pain can be treated with titrated IV morphine approximately 0.05 to 0.1 mg/kg.
• Correct significant electrolyte disturbance.
• Nasogastric decompression is reserved for persistent vomiting, major distension or ileus.

Operative management

Laparoscopic appendicectomy is the preferred definitive operation in most patients where expertise is available.

Stable uncomplicated appendicitis can undergo appendicectomy during the index admission. A short delay for resuscitation or theatre organisation is acceptable, but unnecessary prolonged delay should be avoided. SAGES considers either operation within 12 hours or later operation reasonable in stable uncomplicated disease.

Emergency or expedited source control is required with:

• Generalised peritonitis
• Free perforation with ongoing contamination
• Sepsis with uncontrolled intra abdominal source
• Haemodynamic deterioration
• Progressive peritoneal signs
• Failed nonoperative treatment

At operation, identify the appendiceal base, divide the mesoappendix, securely close the stump and remove contaminated fluid. Routine stump inversion is unnecessary. Routine drain placement after complicated appendicectomy is not recommended.

Antibiotics

For adults undergoing appendicectomy, a practical perioperative regimen is:

Ceftriaxone 2 g IV plus metronidazole 500 mg IV, administered before incision.

After complete appendicectomy for uncomplicated appendicitis, postoperative antibiotics are not routinely required.

For perforation, abscess, gangrene with contamination or generalised peritonitis, continue therapeutic Gram negative and anaerobic coverage.

A practical adult regimen is:

Ceftriaxone 2 g IV every 24 hours plus metronidazole 500 mg IV or orally every 12 hours.

For severe sepsis, major contamination or substantial risk of resistant organisms:

Piperacillin tazobactam 4.5 g IV loading dose, followed by 4.5 g IV every 8 hours as an extended infusion, with renal dose adjustment where required.

After adequate source control, prolonged antibiotic courses add little benefit. Short treatment courses, commonly about 3 to 5 days, are appropriate for complicated appendicitis when the patient is improving.

Persistent fever, pain, ileus or sepsis should prompt investigation for failed source control rather than automatic extension of antibiotics.

Intra abdominal cultures are unnecessary in uncomplicated appendicitis but should be considered during source control for complicated infection, particularly when resistant organisms are possible.

Nonoperative treatment

Antibiotic only treatment may be considered in imaging confirmed uncomplicated appendicitis when the patient is stable, has no generalised peritonitis, abscess or perforation and can return promptly if symptoms recur.

An appendicolith increases treatment failure and recurrence risk and generally strengthens the case for appendicectomy. SAGES currently favours operative treatment, although nonoperative treatment remains a reasonable informed choice in selected patients.

Failure is suggested by increasing pain, new peritonism, persistent fever or vomiting, worsening sepsis, haemodynamic deterioration or failure to improve clinically. These patients require reassessment and usually appendicectomy.

Postoperative care

Resume oral intake as tolerated, mobilise early and use multimodal analgesia. Venous thromboembolism prophylaxis should follow individual risk assessment.

Persistent tachycardia, recurrent fever, increasing abdominal pain, prolonged ileus or rising inflammatory markers after surgery should raise suspicion for intra abdominal abscess, stump leak or another postoperative complication. Contrast enhanced CT is usually the preferred investigation in adults.

All appendicectomy specimens should undergo histopathological examination because unexpected appendiceal neoplasia can alter subsequent management.