Diagnostics

Acute appendicitis is usually a clinical diagnosis based on history, physical examination, and laboratory studies. Imaging is recommended if the clinical diagnosis is uncertain.

• CBC: mild leukocytosis with left shift

• CRP: elevated (> 10 mg/L) [10]

• BMP: ↑ creatinine, electrolyte abnormalities may be present in patients with severe vomiting and diarrhea

• Urinalysis: typically normal in appendicitis; possible findings of mild pyuria and/or hematuria

Urine/serum β-hCG test: perform in all women of reproductive age to rule out pregnancy (including ectopic pregnancy)

Rupture of ectopic pregnancy may mimic the features of acute appendicitis. Imaging and medication preferences also differ in pregnancy.

Decisions regarding the optimal timing and initial imaging modality should be based on individual patient factors (e.g., demographics, likelihood of appendicitis, risk of alternate diagnoses of concern, comorbidities), available resources, and local specialist preferences and hospital policy.

• Options for first-line imaging in nonpregnant adults

  • CT abdomen

  • Ultrasound abdomen (typically performed in conjunction with an appendicitis scoring system)

• First-line imaging for pregnant adults and children: ultrasound abdomen

Many institutions prefer ultrasound as the initial imaging modality, reserving CT scans for inconclusive ultrasound findings.

• Options

  • Formal ultrasound

  • POCUS [29]

• Supportive findings

  • Distended appendix (diameter > 6 mm)

  • Noncompressible, aperistaltic, distended appendix

  • Target sign: concentric rings of hypo- and hyperechogenicity in the axial/transverse section of the appendix

  • Possible appendiceal fecalith: focal hyperechogenicity with posterior acoustic shadowing

CT abdomen is the most accurate initial imaging modality for appendicitis.

• Supportive findings

  • Distended appendix (diameter > 6 mm)

  • Edematous appendix with periappendiceal fat stranding

  • Possible appendiceal fecalith: focal hyperdensity within the appendiceal lumen

  • Evidence of complications

• Additional considerations

  • Consider low-dose CT scan (with IV contrast) to minimize radiation exposure.

  • Consider CT without contrast in patients with contrast allergy.

• Indications

  • MRI without IV contrast: pregnant patients with inconclusive ultrasound findings

  • MRI with IV contrast: nonpregnant patients with inconclusive ultrasound findings and contraindications for CT scan

• Findings: similar to CT scan findings

• Indications: Consider in the following groups of patients with inconclusive findings on imaging. [14][19][20]

  • Women of reproductive age

  • Patients with obesity

  • Patients > 65 years of age

• Findings [34]

  • Acute uncomplicated appendicitis: inflamed, distended, erythematous appendix

  • Possible signs of complications: perforation, gangrene, pus

• Additional steps based on findings [21][35]

  • Normal appendix on diagnostic laparoscopy: Leave in situ.

  • Appendicitis confirmed: Perform laparoscopic appendectomy.