08 Jun

The role of radiological imaging in the diagnosis of acute appendicitis: COLOUR DOPPLER SONOGRAPHY Part 3

COLOUR DOPPLER SONOGRAPHYAccuracy in evaluating the appendix can be enhanced if 5 mm instead of 10 mm sections are taken during scanning — a procedure known as thin collimation. Scanning times can be reduced by narrowing the field to the area of the appendix alone. This technique, called focused appendiceal CT (FACT), may, however, miss disease elsewhere in the abdomen or pelvis, or even atypically situated appendices. Therefore, quick preliminary scanning of the abdomen and pelvis is recommended, together with rectal instillation of contrast material. The best results have been obtained using helical CT, a technique that is costly and is available at only a small minority of radiology facilities. Advantages include the high speed of the technique, which allows rapid scanning of relatively large areas (even with thin collimation) and a reduction in image distortion due to respiration, but the images are somewhat less sharp than those obtained with conventional techniques.

Some of the largest and most well designed prospective studies of CT in acute appendicitis are summarized in Table 5. Most have employed helical CT with thin collima-tion, enhanced by rectal and/or oral contrast agents. Only one of the studies described in Table 5 did not use helical CT. Retrospective studies have yielded similar results. It is difficult to find differences between performance characteristics of helical and conventional CT in these studies. A study that directly compared these techniques seemed to reveal a significant advantage for helical CT, but there was wide and uncontrolled variation in other aspects of the scanning technique. It has been claimed that CT is more accurate than clinical assessment, and that it reduces the negative laparotomy rate without increasing the perforation rate. It also seems to have a greater positive impact on clinical care than does ultrasonography. Another study, however, found that CT scanning significantly prolonged the diagnostic evaluation and increased the perforation rate. Best quality drugs available at best online pharmacy at prices that you are going to enjoy every time: get your proventil inhaler dosage with no problems and no prescription of any kind any time you need some treatment that works 100%.

TABLE 5
Prospective studies of computed tomography scans in the diagnosis of acute appendicitis

Author,year Contrastagent n Acute appendicitis (%) Sensitivity(%) Specificity(%) PPV(%) NPV(%) Accuracy(%)
Balthazar et al, 1991 Oral, intravenous 100 64 98 83 91 97 93
Malone et al, 1993 None 211 36 87 97 94 93 93
Balthazar et al, 1994 Oral 100 54 96 89 96 95 94
Rao et al, 1997 Oral, rectal 100 56 100 95 97 100 98
Rao et al, 1997 Rectal 100 53 98 98 98 98 98
Lane et al, 1997 None 109 38 90 97 95 95 94
Funaki et al, 1998 Oral, rectal 100 30 97 94 88 99 95
Lane et al, 1999 None 300 38 96 99 98 97 97
Pickuth et al, 2000 None 120 78 95 89 97 83 93
Sivit et al, 2000 Oral, rectal 153 40 95 93 91 97 94
Weltman et al, 2000 Oral, intravenous 100 48 99 98 98 99 99
Stroman et al, 2001 Oral, intravenous 107 37 92 85 75 95 90
Jacobs et al, 2001 Oral, intravenous 228 22 94 95 84 98 95

NPV Negative predictive value; PPV Positive predictive value

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