Emergency Radiology (2004) 10: 235–237 DOI 10.1007/s10140-003-0319-y

O R I GI N A L A R T IC L E

Vincenzo Giuliano Æ Concetta Giuliano Æ Fabio Pinto Mariano Scaglione

Rapid CT scan visualization of the appendix and early acute non-perforated appendicitis using an improved oral contrast method

Received: 22 August 2003 / Accepted: 5 October 2003 / Published online: 28 January 2004 Ó ASER 2004

Abstract The purpose of this study was to optimize detection of the normal appendix in the clinical exclusion of acute nonperforated appendicitis using an improved and rapid method of bowel opacification in conjunction with the CT examination. A prospective evaluation of 100 consecutive patients, ranging from 13 to 50 years in age, was performed over a 4-month period using water-soluble oral contrast medium consisting of a fixed dose of diatrizoate salts administered as a prepared beverage in the emergency ward 50 min prior to performing a CT scan to evaluate clinical signs and symptoms of early acute appendicitis. The appendix was visualized in 84% (84 of 100) of patients, with a mean transit time of 50 min. The appendix filled with oral contrast medium in 89% (75 of 84) patients, and this sign was reliable in excluding appendicitis. In no instance did a contrast-filled appendix prove to represent appendicitis. The earliest signs of appendicitis were seen in 8% (8 of 100) patients. CT scan findings included absence of a contrast- or air-containing appendix with appendiceal thickening and infiltration of the periappendiceal mesenteric fat. CT scan utilizing a fixed dosage of orally administered water-soluble contrast containing diatrizoate salts, with a mean transit time of 50 min, provides a rapid and efficient means of visualizing the appendix in the clinical exclusion of appendicitis in the emergency setting. Keywords Computed tomography Æ Appendicitis Æ Oral contrast Æ Bowel opacification

Missed or delayed diagnosis of appendicitis ranks high among the list of nontraumatic clinical entities that lead to litigation. Despite a high prevalence in the population, with a lifetime risk between 6% and 9%, appendicitis often evades clinical detection [1, 2, 3, 4]. Appendicitis is a challenging diagnosis for the emergency room physician because delay in diagnosis leads to the increased morbidity and mortality associated with perforation and sepsis; on the other hand, unnecessary laparotomy incurs potential risks related to surgery and anesthesia and considerable cost [5, 6, 7]. CT methods of evaluating appendicitis have improved diagnostic accuracy to 83–98% [8, 9, 10]. However, in approximately 30% of patients, the appendix is not visualized or evades detection whether contrast is administered orally, rectally, or via the intravenous route [11]. Barium suspension still remains the preferred agent of oral contrast administration, but requires a large volume and considerable time, with transit times of 1.5–2.0 h in order adequately to opacify the appendix and cecum [12]. This is not always practicable in the routine clinical setting due to patient noncompliance and scanner availability. The purpose of this study was to provide a more rapid and improved method for visualization of the appendix in the clinical exclusion of appendicitis in the emergency setting, utilizing a fixed dosage of diatrizoate salts administered as a prepared beverage 50 min prior to performing the CT scan.

Materials and methods V. Giuliano (&) Æ C. Giuliano Nova Southeastern University, 5732 Canton Cove, Winter Springs, FL 32708, USA E-mail: [email protected] F. Pinto Æ M. Scaglione Department of Emergency Radiology, Cardarelli Hospital, Piazza Amedeo 15, 80121 Naples, Italy

During an approximately 4-month period, between December 2002 and March 2003, a prospective study of 100 consecutive patients was performed using CT scanning for clinical exclusion of appendicitis. The age range was 13–50 years, with a mean age of 27 years. Written and signed informed consent was documented as part of the patient’s medical record in each case. Pregnancy was excluded in all female patients of childbearing age by measurement of the serum chorionic gonadotropin level and documented as part of the medical record. The study was confined to a selected population of patients with equivocal signs of appendicitis according to the following clinical criteria: a less than 24-h history of right lower quadrant abdominal

236 pain; fever (above 99 °F, 37°C); equivocal focal point tenderness and peritoneal signs on physical examination; and equivocal or borderline leukocytosis. The medical history was independently confirmed by two radiologists (V.G., C.G.) present in the examination room. The patient population and clinical criteria used for case selection were those most representative of the clinical presentation seen in our emergency ward: typically, an older patient (not of pediatric age) with ‘‘equivocal’’ symptoms of appendicitis and felt to be at probably low risk of this condition. Hard copy scans were reviewed by two radiologists (V.G., C.G.), in conjunction, with clinical follow-up and pathologic correlation. Imaging findings were defined as follows: negative for appendicitis, based on the appearance of a contrast- or air-filled appendix; probable appendicitis, based on absence of contrast or air within the appendix, with appendiceal wall thickening and infiltration of the periappendiceal mesenteric fat; and indeterminate for appendicitis, based on inability to visualize an appendix, or on the finding that the appendix was visualized but not contrast- or air-filled or thickened. Interobserver agreement of results was determined according to the j statistic [13]. Once a provisional clinical diagnosis of appendicitis was made according to the defined clinical criteria described above, the patient was prepared in the emergency ward for a CT scan examination, consisting of 240 ml of an oral solution of flavored beverage containing 13.2 g meglumine diatrizoate, 2.0 g sodium diatrizoate, and 1.8 g noncaloric artificial sweetener. Imaging was performed with a conventional single-slice helical CT scanner (Prospeed; GE Medical Systems, Milwaukee, Wis.). A 100-ml bolus of iopromide 62% (Ultravist 300; Berlex Laboratories, Wayne, NJ) was injected intravenously at a rate of 1.5 ml/s, with a 60-s scan delay. Imaging parameters included 7 mm collimation with additional 5-mm thin-section scans through the appendix acquired in the clustered-helical mode (detail mode) at 120 kV, 250 mA, and 1.0 s. CT scans were performed at 50 min following oral administration of contrast. Patients categorized as negative for appendicitis and indeterminate for appendicitis were followed up by their primary care physician at one week, with follow-up laboratory data after CT examination, to exclude missed appendicitis. Pathologic correlation was obtained in positive cases.

Results The appendix was visualized in 84% (84 of 100) of patients with a mean transit time of 50 min. The appendix filled with oral contrast media in 89% (75 of 84) patients and was reliable in excluding appendicitis (Fig. 1). In no instance did a contrast-filled appendix prove to represent appendicitis, indicating a specificity of 100%. The earliest signs of appendicitis were seen in 8% (8 of 100) patients. CT scan findings included absence of a contrast- or aircontaining appendix with appendiceal thickening and infiltration of the periappendiceal mesenteric fat (Fig. 2). Specificity and positive predictive value statistics were not tabulated because of the relatively small number of positive cases. In 8% (8 of 100) patients, the appendix was not identified, which was attributed to a retrocecal position and paucity of mesenteric fat. Interobserver agreement of the findings, as determined by the j statistic, was 0.95 (very good).

Discussion The clinical condition of appendicitis as a cause of acute abdomen often results in bowel distention and fluid-

Fig. 1 Transverse CT scan of the pelvis reported as negative for appendicitis, based on the presence of a normal contrast-opacified appendix with normal thickness (arrow), in a 30-year-old woman

filled bowel loops which respond poorly to oral contrast media containing salts of diatrizoic acid. Commercially available Gastrografin (sold by Bracco Diagnostics, Milan, Italy) and Gastroview (sold by Mallinckrodt, Inc., St. Louis, Mo.) both contain identical amounts of pharmacologically acceptable nontoxic salts of diatrizoic acid comprising approximately 660 mg meglumine diatrizoate and 100 mg sodium diatrizoate per milliliter of solution. The recommended dosage for CT scan examinations is 25 ml (containing 9.17 g iodine) in 1000 ml water administered orally 60 min prior to imaging. Individual dosing can be difficult to administer because of the lack of a measuring tool. Bowel opacification is often scant, dilute, or nonexistent due to a dilutional effect which occurs when this large volume of fluid is mixed with the enteric fluid contained within distended bowel loops. Diarrhea can be a common side effect due to the overload of a large amount of fluid volume in the gastrointestinal tract [4, 12]. Diatrizoate salts are also bitter and unpleasant tasting, further contributing to reduced patient compliance. In cases of perforated appendicitis, diatrizoate salt solutions can permeate freely into the peritoneal cavity without adverse effects. Barium suspension, when free in the peritoneal cavity, has been associated with a rare incidence of peritonitis [14, 15, 16, 17] and should be used cautiously in the setting of acute abdomen. The authors believe that the proposed oral contrast preparation using diatrizoate salts provided a practical means for improved and more rapid gastrointestinal opacification for CT examinations performed to exclude appendicitis. The addition of a flavoring agent resulted in better patient compliance because of the more pleasant taste. However, our method is most practicable in an older, nonpediatric population, in whom oral intake is better tolerated. Some difficulties would be expected in the pediatric population, where greater noncompliance

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smaller volume of oral fluid intake, 240 ml compared to the 1000 ml proposed in the current literature [4, 12]. This theory is supported in part by the fact that the proposed method decreases nonvisualization of the appendix from 30% to 8%, and increases the transit time to contrast opacification of the cecum from the 1.5–2.0 h reported in the literature [12] to 50 min in our series. Our rapid and efficient CT method for evaluation of patients with suspected appendicitis greatly expedited their clinical management and reduced the standard long patient waiting times—typically more than 6 h— in our emergency ward.

References

Fig. 2a–c Transverse CT scans of the pelvis reported as probable appendicitis. a Thickened appendix (arrow) in a 28-year-old man. b Thickened appendix with subtle mesenteric infiltration (arrow) in a 33-year-old woman. c Thickened appendix with more pronounced mesenteric infiltration (arrow), in a 47-year-old man

might be encountered and placement of a nasogastric tube could be necessary. A lower incidence of diarrhea was encountered in our series, attributed to the use of a

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