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Diagnosis is based on history and physical examination backed by an elevation of neutrophilic white cells. Atypical histories often requires ultrasound and/or CT scanning (Hobler, K., 1998).
The classical history in appendicitis is diffuse pain in the periumbilical region which then localizes as pain and tenderness at McBurney's point (associated with an inflamed appendix coming in contact with the surrounding parietal peritoneum). This point is located on the right-hand side of the abdomen one-third of the distance between the anterior superior iliac spine and the navel. Here, on gentle palpation, the abdominal muscles often feel firm to rigid because of involuntary spasm, and a cough also produces a localized soreness.
Other physical findings include right-side tenderness on a digital rectal exam. Since the appendix normally lies on the right, if a finger is inserted into the rectum and there is tenderness when pressure is applied toward the right, this indicates an increased likelihood that the patient has a pelvic appendix.
Other signs used in the diagnosis of appendicitis are the psoas sign (useful in retrocecal appendicitis), the obturator sign (specifically the obturator internus muscle), Blumberg's sign, and Rovsing's sign.
Ultrasonography and Doppler sonography also provide useful means to detect appendicitis, especially in children. In some cases (15% approximately), however, ultrasonography of the iliac fossa does not reveal any abnormalities despite the presence of appendicitis. This is especially true of early appendicitis before the appendix has become significantly distended and in adults where larger amounts of fat and bowel gas make actually seeing the appendix technically difficult. Despite these limitations, in experienced hands sonographic imaging can often distinguish between appendicitis and other diseases with very similar symptoms such as inflammation of lymph nodes near the appendix or pain originating from other pelvic organs such as the ovaries or fallopian tubes.
In places where it is readily available, CT scan has become the diagnostic test of choice, especially in adults whose diagnosis is not obvious on history and physical. (The use of CT in pregnant women and children is significantly limited, however, by concerns regarding radiation exposure.) A properly performed CT scan with modern equipment has a detection rate (sensitivity) of over 95% and a similar specificity. Signs of appendicitis on CT scan include lack of contrast (oral dye) in the appendix and direct visualization of appendiceal enlargement (greater than 6 mm in diameter on cross section). The inflammation caused by appendicitis in the surrounding peritoneal fat (so called "fat stranding") can also be observed on CT, providing a mechanism to detect early appendicitis and a clue that appendicitis may be present even when the appendix is not well seen. Thus, diagnosis of appendicitis by CT is made more difficult in very thin patients and in children, both of whom tend to lack significant fat within the abdomen. The utility of CT scanning is made clear, however, by the impact it has had on negative appendectomy rates. For example, use of CT for diagnosis of appendicitis in Boston, MA has decreased the chance of finding a normal appendix at surgery from 20% in the pre-CT era to only 3% according to data from the Massachusetts General Hospital.
According to a systematic review from UC-San Francisco comparing ultrasound vs. CT scan, CT scan is more accurate than ultrasound for the diagnosis of appendicitis in adults and adolescents. CT scan has a sensitivity of 94%, specificity of 95%, a positive likelihood ratio of 13.3 (CI, 9.9 to 17.9), and a negative likelihood ratio of 0.09 (CI, 0.07 to 0.12). Ultrasonography had an overall sensitivity of 86%, a specificity of 81%, a positive likelihood ratio of 5.8 (CI, 3.5 to 9.5), and a negative likelihood ratio of 0.19 (CI, 0.13 to 0.27). PMID 15466771
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