Because appendicitis in children frequently mimics other processes, diagnosis can be difficult. Although ultrasound examination can improve diagnostic certainty, its success is operator-dependent, and it does not usually show a retrocecal or noninflamed appendix. Peña and colleagues devised a study to see if use of ultrasonography plus computed tomography with rectal contrast (CT-RC) could improve diagnosis of appendicitis and decrease use of resources in children.

Patients with signs and symptoms of acute appendicitis who were between three and 21 years of age were included as long as they were not pregnant, had no contraindications to rectal contrast medium and had not had an appendectomy. Children with unequivocal presentations underwent appendectomy immediately. Patients with equivocal findings were enrolled in the protocol. Each child initially had a pelvic ultrasound examination.

A positive ultrasound result was defined as visualization of a distended, fluid-filled, non-compressible structure that was at least 6 mm in diameter. This mass also had to have no peristalsis, a stable shape and position, and a location consistent with the appendix (anterior to the psoas muscle or retrocecal). A definitive ultrasound result consistent with the clinical presentation led to a laparotomy. An equivocal ultrasound result, or one in which the appendix was not visualized, led to CT-RC, which was performed as follows: a slow, controlled rectal drip of 200 to 1,000 mL of diatrizoate meglumine (Gastrografin) was administered, followed by CT scanning from the tip of L3 to the acetabular roof. Visualization of an abnormal appendix or pericecal inflammation (or abscess) with a fluid-filled tubular structure more than 6 mm in diameter, or inflammatory changes around the appendiceal area (such as fat stranding, abscess or phlegmon) were defined as positive findings.

The likelihood (on a 1 to 10 scale) of each patient's actually having appendicitis was determined by a surgeon after the ultrasound examination and the CT-RC. Each patient was essentially assigned to one of three treatment plans: discharge, observation or surgery. Those who did not have surgery were followed by telephone two weeks after being seen in the emergency department. In those who had an appendectomy, the diagnosis was confirmed by pathologic examination of the appendix.

Of 177 children initially evaluated, 2.3 percent were discharged, and 19.2 percent went directly to surgery. Most of these (88 percent) had pathologically proven appendicitis (30 percent of these were perforated).

This left 139 patients to be evaluated in the study. Thirty-one of these had ultrasonography only; of these, 19 went directly to surgery after the ultrasound examination. All 19 of these patients had confirmed appendicitis after surgery. The other 11 patients in whom the ultrasound result was negative had the following resolutions: 64 percent of these had resolved symptoms, 18 percent had a normal appendix on ultrasound examination, 9 percent had another diagnosis and 9 percent could not tolerate the rectal contrast (this last child subsequently returned to the hospital with a perforated appendix). In the final group, 108 patients had CT-RC after an equivocal or negative ultrasound result. About one third (29 percent) of these had appendectomy after the CT examination. Appendicitis was found in 90 percent of these patients. One fourth (23 percent) of the children were admitted for observation; only one of these children had appendicitis. The remainder of the group (48 percent) were discharged; none had appendicitis.

The authors conclude that use of CT-RC was more beneficial than ultrasonography in the diagnosis of acute appendicitis in children. That is, there was a beneficial change in management decisions in 18.7 percent of children evaluated with ultrasonography, and a 73.1 percent beneficial change in those evaluated with CT-RC in addition. Although the predictive value of a positive ultrasound result is high (and unnecessary radiation could thus be avoided), the authors conclude that CT-RC can be helpful in children whose diagnosis of appendicitis remains unclear after clinical and ultrasound evaluation.