Computed tomography scan of the lower abdomen showing a calcified fecolith at the center of an inflamed appendix mass in the right iliac fossa
A number of clinical signs described in the era before widely available cross-sectional imaging are used to assist in clinical diagnosis (Table 21.1). In the modern era these are of more historical interest; however, localized tenderness with rebound (not to be repeated) remains a cardinal feature.
Clinical signs associated with appendicitis
Patient points to the right iliac fossa when asked to locate the maximum point of tenderness
Pain in the right iliac fossa with coughing
Pain in the right iliac fossa in response to palpation of the left iliac fossa
Patient lies with the right hip flexed; pain increases with passive extension of the right hip
Increased pain with flexion and internal rotation of the right hip
21.3.1 Differential Diagnoses
The clinical diagnosis of appendicitis is challenging because of the extensive differential diagnosis, particularly in young children, the elderly, and women of childbearing age or who are pregnant.
In children, the most common differentials are mesenteric lymphadenitis, acute gastroenteritis, and, in those younger than age 2 years, ileocecal intussusception. Henoch-Schönlein purpura is often associated with right iliac fossa pain; an upper respiratory tract infection and a developing ecchymotic or purpuric rash on the limbs or buttocks usually precede this.
In adults, nonspecific ileitis, Yersinia enterocolitica infection, or acute presentation of Crohn’s ileitis may be difficult to distinguish clinically; however, imaging is usually a diagnostic indicator of ileitis rather than appendicitis. Perforation of a duodenal ulcer may result in fluid tracking along the right paracolic gutter, whereas sigmoid diverticulitis is an important differential in patients over 40. Inflammation of a Meckel diverticulum may be indistinguishable from appendicitis.
In women of childbearing age, pelvic inflammatory disease, including salpingitis and tubo-ovarian sepsis, should be considered. Typically the pain is low and central within the abdomen. When suspected, a high vaginal swab should be taken and a gynecological opinion obtained. Treatment is usually a combination of ofloxacin and metronidazole orally for 14 days.
Mittelschmertz or midcycle pain is usually the result of a small intraperitoneal bleed following the rupture of a follicular cyst. A pregnancy test is negative and symptoms usually settle within hours. Pelvic ultrasound may demonstrate a small amount of free fluid in the pouch of Douglas. Rupture or torsion of an ovarian cyst or a right-sided tubal pregnancy may be difficult to distinguish, and pelvic ultrasound is helpful. Laparoscopy may be required as an early recourse for both diagnostic and therapeutic purposes.
Appendicitis is the most common abdominal surgical condition in pregnancy, occurring in approximately 1 in 2,000 pregnancies. Ultrasound and magnetic resonance imaging are helpful in establishing the diagnosis and guiding surgical intervention.
While the diagnosis of appendicitis has traditionally been clinical, appendicectomy based on clinical criteria alone leads to a histologically normal appendix being removed in 15–30 % of cases. A number of clinical and laboratory-based scoring systems have been devised to assist in diagnosis . The two most useful are the Alvarado score  and the Appendicitis Inflammatory Response (AIR) score  (Table 21.2).
Comparison of parameters used in Alvarado and Appendicitis Inflammatory Response (AIR) scores for diagnosis of appendicitis
Alvarado score 
AIR score 
Shift to RIF
>10.0 × 109/l
≥15.0 × 109/l
While scoring systems in general do not sufficiently discriminate predictive values to be used alone to diagnose appendicitis, Kollar et al.  found that the AIR score is accurate in excluding appendicitis in those deemed low risk and more accurate at predicting appendicitis than the Alvarado score in those deemed high risk. They advocate use of the scoring systems for selective CT in those deemed medium risk.
Widespread availability of ultrasound and cross-sectional imaging in modern emergency surgical units has led to the increasing use of and reliance on imaging in supporting a clinical decision to perform appendicectomy. Ultrasound does not expose the patient to ionizing radiation and is highly specific in children and young adults; however, Doria et al.  found in a meta-analysis that CT was more sensitive than ultrasound. Kim et al. , addressing concerns regarding the dosage of ionizing radiation in children and young adults, showed the noninferiority of low-dose CT to conventional CT in a large series of patients with clinical suspicion of appendicitis.