28 May

The role of radiological imaging in the diagnosis of acute appendicitis

AppendicitisAppendicitis is a common and important clinical problem that afflicts 8.6% of male and 6.7% of female Americans. There are 250,000 to 300,000 appendectomies, including 60,000 to 80,000 involving children, and more than one million patient-days of hospitalization for appendicitis, each year in the United States.

There are problems with the current methods of diagnosis, which are based mainly on the clinical history, physical examination and simple laboratory tests. The classic presentation includes vague midabdominal pain, anorexia and nausea, followed by localized right lower quadrant (RLQ) abdominal pain and guarding, and leukocytosis. Up to 45% of cases, however, have atypical symptoms and/or signs.

The clinical diagnosis of acute appendicitis is accurate only 70% to 80% of the time. Delays in diagnosis often lead to perforation, which occurs in 8% to 39% of cases. To prevent perforation, the surgeon may adopt liberal criteria for surgery, which results in negative appendectomy rates of 15% to 22%. Unnecessary surgery causes pain and inconvenience for patients, wastes precious health care resources and can lead to serious complications. Appendicitis is especially difficult to diagnose, and the consequences of error are greater in children, pregnant women and elderly patients. These difficulties are due to physiological factors, variations in clinical presentation and, in some cases, problems with communication.

Most surveys have found an inverse relationship between rates of perforation and rates of negative appendectomy. Therefore, attempts to reduce the rate of unnecessary surgery often lead to unacceptable perforation rates, while a reduction in the latter is generally achieved at the expense of diagnostic accuracy. For example, Law et al reviewed 216 patients with a preoperative diagnosis of appendicitis, and reported a high rate of diagnostic accuracy (89%), together with a high perforation rate (29%). In contrast, Andersen et al reviewed 454 patients and reported a much lower perforation rate (8%) at the expense of a lower accuracy rate (67%). You are always offered finest quality birth control mircette at the pharmacy you can fully trust and enjoy being its customer. Why wouldn’t you, if it offers lowest prices in the industry and fast delivery that can be free for some orders?

This dilemma has been addressed in four ways:

• adoption of standardized diagnostic criteria;

• observation in hospital of patients with equivocal clinical presentations;

• application of diagnostic tests, including radiological imaging; and

• use of diagnostic laparoscopy.

Of the many standardized scoring systems for the diagnosis of acute appendicitis, the Alvarado criteria, which generate the MANTRELS score (Table 1), appear to be the most effective. A score of more than seven points has a relatively high sensitivity (88% to 90%), but the specificity is generally no better than 80%, and is especially low in women. Modifications have included removing the leukocyte count criteria or reducing the threshold to five points, but these modifications further impair the specificity of the system, particularly in pediatric patients. While these and other criteria may assist junior staff and nonsurgical personnel in identifying patients with appendicitis, they are not likely to be helpful for experienced surgeons who possess astute clinical judgement.

TABLE 1
Alvarado scoring system

Clinical or laboratory feature Points
Migration of pain from the midabdomen to right lower quadrant 1
Anorexia or acetonuria (a surrogate marker of food avoidance) 1
Nausea and vomiting 1
Tenderness in the right lower quadrant 2
Rebound tenderness 1
Elevated temperature (>38°C) 1
Leukocytosis (>10,400 cells/mm3) 2
Shifted white blood cell count (>75% neutrophils) 1
Total possible points 10

Several authorities have suggested that close observation of patients with atypical presentations improves diagnostic accuracy without causing inordinate delays in treatment. Early, appropriate referral to a surgeon appears to be the most important way of producing a successful outcome.

With the exception of leukocytosis, laboratory markers of inflammation have not proved to be of much value in early diagnosis. The use of radiological imaging techniques — plain x-rays, barium enema, ultrasonography, computed tomography (CT), nuclear imaging (scintigraphy) and magnetic resonance imaging (MRI) — is the subject of this review.

Several groups advocate the use of diagnostic laparoscopy. It has a high sensitivity and specificity, and may be especially valuable in women of child-bearing age, because gynecological diseases that might be confused with appendicitis can be readily diagnosed. Appendectomy can be carried out safely and quickly with this technique. The normal-appearing appendix can be left in situ, thus reducing the rate of negative appendectomy. Some authorities recommend that the appendix be removed in all cases, however, because a normal macroscopic appearance does not exclude the presence of histological appendicitis with certainty. Moreover, it has been suggested that recurrent pain can arise from appendices that have neurochemical or immunological abnormalities even in the absence of overt inflammation.

A substantial proportion of patients report a history of recurrent episodes of pain before appendectomy (recurrent appendicitis) or of prolonged pain, which may or may not be accompanied by histological evidence of fibrosis or of chronic inflammation (chronic appendicitis).

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