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CLINICAL INVESTIGATIONS Impact of Helical Computed Tomography on the Outcomes of Emergency Department Patients with Suspected Appendicitis Sam S. Torbati, MD, David A. Guss, MD Abstract Objectives: To assess the impact of an emergency department (ED) guideline employing selective use of helical computed tomography (CT) on clinical outcomes of female patients with suspected appendicitis. Methods: All patients presenting with suspected appendicitis were prospectively enrolled and managed in accordance with a guideline incorporating selective use of helical CT. Although not the objective of this investigation, male patients were included for purposes of comparison. Patients with clinically evident appendicitis were referred to the surgical service, and patients with equivocal presentations were studied with helical CT. Patients were followed to final surgical or clinical outcomes. Outcome measures included time from ED presentation to laparotomy and rate of appendiceal perforation. These measures were compared with those of a historical cohort of patients preceding the use of helical CT. Results: A total of 310 consecutive patients with suspected appendicitis were enrolled; 92 had appendicitis. Sixty patients were referred to the surgical service without helical CT, and 41 had appendicitis (68%). Helical CT was
performed on 250 patients; 51 had appendicitis (20%). For males, the mean interval from ED presentation to laparotomy was 559 minutes (95% CI ¼ 444 to 674 minutes) during guideline use and 480 minutes (95% CI ¼ 405 to 555 minutes) before. This interval for females was 433 minutes (95% CI ¼ 326 to 540 minutes) during guideline use and 710 minutes (95% CI ¼ 558 to 862 minutes) before. Appendiceal perforation rate for males was 0.25 (95% CI ¼ 0.14 to 0.36) during guideline use and 0.38 (95% CI ¼ 0.29 to 0.47) before; perforation rate for females was 0.06 (95% CI ¼ 0.05 to 0.17) during guideline use and 0.23 (95% CI ¼ 0.14 to 0.32) before. Helical CT had 92% sensitivity, 97% specificity, and 96% accuracy in diagnosing appendicitis. Conclusions: Helical CT is highly accurate in detecting appendicitis in patients with equivocal ED presentations. The use of a guideline employing selective helical CT was associated with a decline in the time from ED presentation to operative intervention in females. Key words: appendicitis; helical computed tomography (CT); perforated appendix. ACADEMIC EMERGENCY MEDICINE 2003; 10:823–829.
Appendicitis is the most common cause of acute abdominal pain requiring surgical treatment in patients presenting to the emergency department (ED), with an annual incidence of 250,000 cases in the United States.1,2 Delay in diagnosing appendicitis is associated with an increased rate of perforation leading to greater morbidity and mortality.3 The diagnosis of acute appendicitis remains clinically challenging because many nonsurgical disorders have similar clinical presentations, and appendicitis itself can mimic many other conditions. A previous study showed that females presenting to the ED with appendicitis require increased diagnostic resources and
have a longer interval from presentation to operative intervention compared with males.4 In many more recent studies, helical computed tomography (CT) has shown high rates of diagnostic accuracy and has emerged as the diagnostic imaging test of choice in evaluating patients with suspected appendicitis.5–28 Some authors recommend routine use of helical CT for all patients with acute right lower quadrant pain, citing improved clinical accuracy and reduction in hospital resource utilization.8,29–31 We developed and prospectively studied a management guideline using helical CT in the ED evaluation of patients with suspected appendicitis. Our objectives were to assess the impact of this new management guideline on clinical outcomes in females, specifically time from ED presentation to operation and perforation rate, and to assess the diagnostic accuracy of helical CT in the subset of patients with equivocal clinical presentations of appendicitis. We hypothesized that the guideline using helical CT would lead to a reduction in the time from ED presentation to operation and a reduction in the rate of perforation for females presenting to the ED with appendicitis.
From the Department of Emergency Medicine, UCSD Medical Center (SST, DAG), San Diego, and the Department of Emergency Medicine, Cedars–Sinai Medical Center (SST), Los Angeles, CA. Received September 24, 2002; revisions received December 28, 2002, and January 13, 2003; accepted January 21, 2003. Presented at the American College of Emergency Physicians Annual Research Forum, Philadelphia, PA, October 2000. Address for correspondence and reprints: David A. Guss, MD, Department of Emergency Medicine, UCSD Medical Center, 200 West Arbor Drive, San Diego, CA 92103-8676. Fax: 619-543-3115; e-mail:
[email protected].
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METHODS Study Design. This was a prospectively designed consecutive case series study. The study protocol was reviewed and approved by the institution’s Committee on Human Investigation. All patients provided informed consent; in the circumstances of minors, parental consent was obtained. Study Setting and Population. The study was performed at a university medical center ED with an annual census of 35,000 patient visits, staffed by emergency physicians and rotating residents supervised by emergency physicians. All patients presenting to the ED in whom appendicitis was the principal diagnostic consideration of the managing physicians were enrolled in a consecutive manner between September 1998 and March 2000. All males and females were included with no age exclusions. Pregnant patients were excluded. Study Protocol. The practice guideline was developed and instituted employing the selective use of helical CT in patients presenting to the ED with
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suspected appendicitis (Figure 1). Members of the Departments of Emergency Medicine and Radiology crafted the guideline based on available evidence concerning the use of helical CT in appendicitis. After ED attending evaluation, patients with clinically evident appendicitis were referred directly to the surgical service. A case was thought to be clinically evident on the basis of physician assessment of symptoms and physical findings. Patients with equivocal presentations for appendicitis (diagnosis of insufficient certainty to warrant admission to the surgical service) were studied with helical CT. An initial noncontrast helical CT scan of the abdomen and pelvis was performed with 5 mm collimation, 5 mm image spacing, and helical pitch of 1.5:1 from the top of the kidneys to the bottom of the bladder. If the diagnosis remained in doubt, a second contrastenhanced study followed with the use of intravenous, oral, and/or rectal contrast material at the discretion of the radiologist. Intravenous contrast material consisted of 125 mL of ioversol (Optiray 320) at 4 mL/ second. Rectal contrast material consisted of either 10 mL of diatrizoate sodium (Hypaque) or 80 mL of diatrizoate meglumine (Gastrografin) in 1,000 mL of
Figure 1. Guideline using helical computed tomography (CT) in the evaluation of emergency department patients with suspected appendicitis. Dx ¼ diagnosis.
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water. An amount of 700 to 1,000 mL of rectal contrast material was placed by gravity into the rectum as tolerated by the patient. Helical CT scans were interpreted as positive for appendicitis on a nonenhanced study when a dilated appendix ([6 mm in diameter) was seen associated with an appendicolith or periappendiceal inflammatory changes, such as fat stranding, phlegmon, fluid collection, and extraluminal gas. The scan was considered indeterminate if inflammatory changes were seen but the appendix could not be visualized. Enhancement of the appendiceal wall was considered to be a sign of appendicitis in patients receiving intravenous contrast material. Abnormal cecal apical changes, such as focal cecal apical thickening, the arrowhead sign (triangular-shaped space between the thickened wall of the inflamed apical appendix), or the cecal bar (a bar of density between the cecal lumen and appendicolith), were considered highly suggestive of appendicitis in studies with rectal or oral contrast material. Negative diagnostic criteria included an absence of an enlarged appendix and inflammatory changes in the right lower quadrant. Visualization of a normal appendix was not considered necessary for a negative diagnosis. Board certified radiologists interpreted all CT scans. The results of the helical CT scan were conveyed to the surgical service, and the final decision to operate was made by surgical attending staff. Outcomes. Patients were followed to final surgical or clinical outcomes. Surgical outcomes included operative findings and pathologic reports. Clinical outcomes were determined by two-week telephone follow-up of all discharged patients and hospital courses of admitted patients. Outcomes measures included time from ED presentation to operative intervention and rates of gross appendiceal perforation. Outcome measures were compared with those of a previous retrospective study of patients with appendicitis.4 That study included only patients between the ages of 12 and 50 years and was performed at the same institution during a period immediately antedating the application of the new guideline and use of helical CT. The purpose of this earlier retrospective study was to determine if females in the childbearing age range (arbitrarily set at age range 12 to 50 years) with appendicitis required more time and resources than males in the same age range before operative intervention occurred. This previous study included 196 patients (83 females and 113 males).4 The only difference in management approach over the period encompassed by the two studies was the use of helical CT. To create an appropriately matched group, data from a subset of patients in the same age group (12 to 50 years) and gender in the current study were used for comparison and analysis. Data from all patients enrolled in the present study
were used in evaluating the performance of helical CT in the diagnosis of appendicitis. Data Analysis. Sensitivity, specificity, positive and negative predictive values (PPV, NPV), accuracy, positive and negative likelihood ratios, and confidence intervals were calculated for the performance of helical CT in diagnosing appendicitis. Ninety-five percent confidence intervals are shown for proportions, and the mean values are shown for continuous variables.
RESULTS During the 19-month study period, all of the 310 consecutive patients presenting to the ED with suspected appendicitis were enrolled; there were 138 (44.5%) males and 172 (55.5%) females. Age range was 7 to 75 years, mean age was 31 years for men and women, and 37 patients were younger than 18 years of age. Helical CT was obtained in 250 patients, and 60 (43 males, 17 females) others were admitted to the surgical service without imaging. Fifteen patients (8 males, 7 females) in whom helical CT was done were lost to follow-up and were excluded from the statistical analysis. All patients lost to follow-up were in the group discharged from the ED with negative helical CT studies. There were 167 helical CT studies performed without contrast enhancement (71%), and 68 patients received some form of contrast enhancement: 33 (14%) intravenous, 16 (7%) intravenous and oral, 7 (3%) rectal, 6 (2.5%) intravenous and oral and rectal, 4 (1.7%) oral, and 2 (1%) intravenous and rectal. A total of 92 patients had appendicitis (69 males, 23 females), resulting in a prevalence rate of 30% in the study population. Of the 60 patients directly admitted to the surgical service, 49 underwent laparotomy (82%) with 41 cases of appendicitis (68%). Three patients had diverticular disease, of which two cases were perforated; one patient had a Wilms’ tumor; one patient had mesenteric adenitis; and three patients had negative laparotomies. Of the remaining 11 patients not undergoing laparotomy, ten were diagnosed with abdominal pain at discharge, and one patient had a perirectal abscess. Prevalence of appendicitis in the group admitted without helical CT was 68%. Prevalence of appendicitis was 84% in the group undergoing laparotomy with a preoperative diagnosis of acute appendicitis. Negative appendectomy in this group was 16%. Perforated appendix was noted in 13 (32%) patients at the time of operation. Of the 250 patients evaluated with helical CT, 51 had appendicitis (20%). Helical CT was positive in 48 patients, 43 of whom had appendicitis. Helical CT was negative in 170 patients, four of whom had appendicitis, and 15 others were lost to follow-up. Helical CT was equivocal in 17 patients (7%), four of whom had
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appendicitis at laparotomy and four with negative laparotomies. Data from patients with equivocal helical CT results were excluded from the analysis because their helical CT findings could not be considered positive or negative for appendicitis. The helical CT performance in diagnosing appendicitis in the low pretest probability group is shown in Table 1. The negative appendectomy rate in the group having helical CT was 7.8%. Perforated appendix was noted in 12 (24%) patients at the time of operation. Helical CT identified an alternate diagnosis in 46% of patients without appendicitis (Table 2). The mean ages for patients in the prior retrospective study (control group) and the current prospective study (age 12 to 50 subgroup used for comparison) were 26.4 and 25.6 years for females and 26.5 years and 28.6 years for males. Average times from ED presentation to laparotomy and rates of appendiceal perforation for the present study and the former study (control) groups are shown in Table 3. The mean time from ED presentation to operation declined significantly for females but not for males. The decline in perforation rate was not statistically significant. The negative appendectomy rate for all patients enrolled in the present study was 12%.
DISCUSSION Abdominal pain is the most common chief complaint of patients presenting to the ED, representing 5% to 10% of all ED visits.1 Approximately 4% of these patients have acute appendicitis, which is the most common surgical emergency, demanding rapid diagnosis and surgical intervention.32 Although patients with typical presentations of acute appendicitis may be referred directly for surgical intervention, many others have atypical symptoms, examinations, and laboratory findings, posing a diagnostic challenge to the treating physician. In the last decade, graded compression sonography, radiolabeled white blood cell scans, and helical CT have been used in the diagnosis of acute appendicitis.
TABLE 1. Helical Computed Tomography Performance in Diagnosing Appendicitis in Patients without Clinically Evident Appendicitis Sensitivity Specificity Positive predictive value Negative predictive value Accuracy Positive likelihood ratio Negative likelihood ratio Pretest probability Posttest probability Pretest odds Posttest odds
92% 97% 90% 98% 96% 30.7 0.08 22% 2% 0.28 0.02
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TABLE 2. Alternate Diagnoses Found on Helical Computed Tomography Ureteral stone Ovarian cyst with/ without rupture Diverticulitis Colitis SBO TOA (PID) Cholelithiasis Inflammatory bowel disease Pyelonephritis Ileitis
21 13 5 5 4 4 3 3 2 2
CBD dilation Adnexal mass
2 2
Pelvic malignancy Mesenteric adenitis Pancreatitis Pneumoperitoneum LBO Retroperitoneal fluid
2 2 2 1 1 1
Hydronephrosis Abdominal malignancy
1 1
Alternate diagnosis rate: 46%. SBO ¼ small bowel obstruction; TOA ¼ tubo-ovarian abscess; PID ¼ pelvic inflammatory disease; CBD ¼ common bile duct; LBO ¼ large bowel obstruction.
Of these three methods, helical CT has gained the greatest acceptance and experience in academic and private EDs. These studies include adult and pediatric populations, with varying techniques ranging from full abdominal and pelvic study with intravenous, oral, and rectal contrast material to focused nonenhanced scans of the lower abdomen.5–27 This study prospectively evaluated the impact of a practice guideline stipulating the selective use of helical CT for evaluation of patients with suspected appendicitis presenting to a university ED. There was a significant decline in the time from ED presentation to operation for females; however, there was no change for males. This decline is believed to represent a significant benefit of the helical CT guideline. The differential impact in women is likely a consequence of the fact that the diagnosis is made more challenging in this group because of an expanded differential diagnosis with overlapping clinical findings. This fact was shown in our previous retrospective study in which women in the childbearing age group (12 to 50 years) with appendicitis were shown to have a longer interval from presentation to operation than men and required the use of more ancillary tests.4 The mean time from presentation to operation was higher for males in the current study compared with the preguideline group; however, there is major overlap of the confidence intervals for these means, suggesting they are not different. Some consideration is given to the possibility that the trend to longer times for males in the current study was secondary to the use of helical CT because this diagnostic modality takes some time to perform and interpret, and the liberal use of the imaging technique likely fosters its use. Caution should be used in drawing any conclusions, however, given the overlapping confidence intervals. Despite a large decline in the proportion of patients with appendiceal perforation in the group managed in accordance with the helical CT guideline, there was
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TABLE 3. Primary Outcome Measures before and after Initiation of the Guideline Using Helical Computed Tomography (CT) Outcomes Average time to OR (min), males Average time to OR (min), females Perforation rate, males Perforation rate, females
After CT Guideline (n ¼ 76)
Before CT Guideline (n ¼ 196)
559 (95% CI 444, 674) 433 (95% CI 326, 540) 0.25 (95% CI 0.14, 0.36) 0.06 (95% CI –0.05, 0.17)
480 (95% CI 405, 555) 710 (95% CI 558, 862) 0.38 (95% CI 0.29, 0.47) 0.23 (95% CI 0.14, 0.32)
OR ¼ operating room; CI ¼ confidence interval.
overlap of the confidence intervals compared with the former non–helical CT study group. This was likely a consequence of the small sample size making this study underpowered to detect a meaningful decline, and introducing the likelihood of a type II error. A post hoc power analysis indicated that two additional women with nonperforated appendicitis would have yielded nonoverlapping confidence intervals for perforation rates in females. This study has been terminated; it will not be possible to address this concern in the context of the present investigation. Balthazar et al.14 reported no change in the rate of appendiceal perforation (22.1%) when patients were evaluated with helical CT, whereas Rao et al.17 reported a significant reduction in perforation rates (22% versus 14%) after CT was used. Although the trend in our study is impressive, it cannot be concluded from this study that the management guideline incorporating the use of helical CT is associated with a decline in rates of appendiceal perforation. Although this prospective study was not designed to study the effects of the protocol on negative appendectomy rates, other investigators have shown a reduction in negative appendectomy rates with the use of helical CT in the evaluation of patients with suspected appendicitis. Schuler et al.13 found a 5.8% negative appendectomy rate in patients with equivocal presentations who were evaluated with helical CT compared with a historical institutional rate of 13%. Rao et al.17 showed a reduced negative appendectomy rate of 7% with helical CT versus 20% before helical CT was introduced. Peck et al.9 reported a negative appendectomy rate of 5.6% with helical CT versus 19% without helical CT in their community hospital. Mullins et al.24 showed similar results in their pediatric population, in which the use of helical CT led to a reduced rate of negative appendectomies (9% versus 13%). Balthazar et al.14 had a 4% negative appendectomy rate in patients on whom a contrastenhanced helical CT scan was performed. We found a similarly low negative appendectomy rate of 8% in patients with equivocal presentations for appendicitis in whom helical CT was performed compared with 16% for patients referred directly to the surgical service. In developing this protocol, our objective was to minimize the risk of adverse reactions associated with
contrast material and to reduce delays in imaging associated with enteral forms of contrast material. Most (71%) of the patients in whom helical CT was performed had no form of contrast material, allowing for the scan to be performed in an average of 5 minutes in these patients. Despite excellent diagnostic accuracy reported at other centers with nonenhanced helical CT,8,9,12,19,21,25 our radiologists were not as familiar with or comfortable interpreting nonenhanced images. Patients and radiology technical staff at our institution found rectal contrast material to be poorly tolerated; intravenous contrast material was used for additional enhancement of images. As our radiologists gained more experience interpreting nonenhanced images, less contrast material was used, unless alternative diagnoses existed on the initial nonenhanced helical CT scan that required further clarification. Helical CT had an excellent overall performance in diagnosing appendicitis in patients with equivocal presentations. The low percentage (7%) of indeterminate studies further supports the utility of this imaging modality. Our results mirrored those of others in the medical literature, with an overall sensitivity of 92%, specificity of 97%, accuracy of 97%, PPV of 90%, and NPV of 98%.4,5,9,11,18,27 A positive scan was associated with a high positive likelihood ratio of 30.7, and a negative scan was associated with a negative likelihood ratio of 0.08, suggesting that helical CT was an effective test. An additional advantage beyond the diagnosis or exclusion of appendicitis was the provision of an alternative diagnosis in 46% of patients. None of these alternative diagnoses were considered before imaging because the study protocol required appendicitis to be the primary consideration for inclusion in the investigation. Although many of these diagnoses did not have alternative means of confirmation, this additional information still proved valuable in patient management. Despite its high diagnostic accuracy, helical CT, like any other diagnostic test, has its limitations and is not perfect in diagnosing appendicitis. In our CT study population, four patients had false-negative CT scans, and 17 scans were read as equivocal for appendicitis. Clinical judgment cannot be overruled completely by CT findings, and a ‘‘negative’’ study without an
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alternative diagnosis noted on helical CT still might deserve further evaluation.
LIMITATIONS There are several limitations to this study. We chose to eliminate from performance analysis the studies with equivocal interpretation because it was not apparent whether to categorize an equivocal study as positive or negative. It was thought that a truly nondiagnostic study should have a neutral influence on the clinical diagnosis. To assess the impact of the helical CT guideline, we compared two outcome measures—time from presentation to operation and appendiceal perforation rate—with a prior retrospective study. This is not an ideal control population; however, it was not possible to randomize the use of helical CT in our prospective study. Although all patients in both studies were from the same institution, there was a significant time interval between investigations. The use of helical CT was the most prominent single variable in the two studies because it was not available in the preguideline era. It is possible, however, that other factors, such as different physicians or other diagnostic modalities, may have affected these outcome measures. Although there was some variation in faculty composition, helical CT represented the only difference in available diagnostic modalities during the time span encompassed by the two studies. The failure to see any significant change in the time from presentation to operation for males between the two studies suggests that factors such as general institutional efficiency were not responsible for the decline in this interval encountered in females. Finally, we purposely left the criteria for consideration of appendicitis undefined. If we had attempted to create specific diagnostic criteria, we would have had to ensure interobserver reliability and would have been evaluating the performance of those unproven criteria rather than the utility of helical CT. We believe the design of this study, although perhaps uniquely characteristic of the clinical attitudes of the emergency physicians in the study institution, is more likely to be representative of the approach of most emergency physicians. There seem to be ample data in the medical literature to conclude that helical CT has good sensitivity, specificity, PPV, NPV, and accuracy in assessing patients with possible appendicitis. Although this study does help establish a positive clinical impact of helical CT, this area still requires further investigation. It cannot be concluded that because a test has favorable performance characteristics, it should be used. It is incumbent on future investigators to provide additional data to support the notion that the use of helical CT improves the management of patients with appendicitis.
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CONCLUSIONS Helical CT is a highly sensitive and specific imaging tool in the evaluation of patients with the possible diagnosis of appendicitis. A positive scan is associated with a high likelihood of disease, whereas a negative scan dramatically diminishes the likelihood of appendicitis. The use of a guideline incorporating selective use of HCT in patients presenting to an ED with an equivocal clinical picture for appendicitis is associated with a significant decline in time from ED presentation to operation for women and may be associated with a decline in perforation rates for women. This study adds to the growing body of literature supporting the use of helical CT in patients with suspected appendicitis. References 1. Graffeo CS, Counselman FL. Appendicitis. Emerg Med Clin North Am. 1996; 14:653–71. 2. Addiss DG, Shaffer N, Fowler BS, Tauxe RV. The epidemiology of appendicitis and appendectomy in the United States. Am J Epidemiol. 1990; 132:910–25. 3. Hale DA, Molloy M, Pearl RH, Schutt DC, Jaques DP. Appendectomy: a contemporary appraisal. Ann Surg. 1997; 225:252–61. 4. Guss DA, Richards C. Comparison of men and women presenting to an ED with acute appendicitis. Am J Emerg Med. 2000; 18:372–5. 5. Walker S, Haun W, Clark J, McMillin K, Zeren F, Gilliland T. The value of limited computed tomography with rectal contrast in the diagnosis of acute appendicitis. Am J Surg. 2000; 180:450–4. 6. Wilson EB, Cole JC, Nipper ML, Cooney DR, Smith RW. Computed tomography and ultrasonography in the diagnosis of appendicitis: when are they indicated? Arch Surg. 2001; 136:670–5. 7. Kamel IR, Goldberg SN, Keogan MT, Rosen MP, Raptopoulos V. Right lower quadrant pain and suspected appendicitis: nonfocused appendiceal CT—review of 100 cases. Radiology. 2000; 217:159–63. 8. Horton MD, Counter SF, Florence MG, Hart MJ. A prospective trial of computed tomography and ultrasonography for diagnosing appendicitis in the atypical patient. Am J Surg. 2000; 179:379–81. 9. Peck J, Peck A, Peck C, Peck J. The clinical role of noncontrast helical computed tomography in the diagnosis of acute appendicitis. Am J Surg. 2000; 180:133–6. 10. Stroman DL, Bayouth CV, Kuhn JA, et al. The role of computed tomography in the diagnosis of acute appendicitis. Am J Surg. 1999; 178:485–9. 11. Rao PM, Feltmate CM, Rhea JT, Schulick AH, Novelline RA. Helical computed tomography in differentiating appendicitis and acute gynecologic conditions. Obstet Gynecol. 1999; 93:417–21. 12. Lane MJ, Liu DM, Huynh MD, Jeffrey RB Jr, Mindelzun RE, Katz DS. Suspected acute appendicitis: nonenhanced helical CT in 300 consecutive patients. Radiology. 1999; 213:341–6. 13. Schuler JG, Shortsleeve MJ, Goldenson RS, Perez-Rossello JM, Perlmutter RA, Thorsen A. Is there a role for abdominal computed tomographic scans in appendicitis? Arch Surg. 1998; 133:373–7. 14. Balthazar EJ, Rofsky NM, Zucker R. Appendicitis: the impact of computed tomography imaging on negative appendectomy and perforation rates. Am J Gastroenterol. 1998; 93:768–71.
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15. Funaki B, Grosskreutz SR, Funaki CN. Using unenhanced helical CT with enteric contrast material for suspected appendicitis in patients treated at a community hospital. AJR Am J Roentgenol. 1998; 171:997–1001. 16. Rao PM, Rhea JT, Novelline RA, Mostafavi AA, Lawrason JN, McCabe CJ. Helical CT combined with contrast material administered only through the colon for imaging of suspected appendicitis. AJR Am J Roentgenol. 1997; 169:1275–80. 17. Rao PM, Rhea JT, Rattner DW, Venus LG, Novelline RA. Introduction of appendiceal CT: impact on negative appendectomy and appendiceal perforation rates. Ann Surg. 1999; 229:344–9. 18. Rao PM, Rhea JT, Novelline RA, et al. Helical CT technique for the diagnosis of appendicitis: prospective evaluation of a focused appendix CT examination. Radiology. 1997; 202:139–44. 19. Lane MJ, Katz DS, Ross BA, Clautice-Engel TL, Mindelzun RE, Jeffrey RB Jr. Unenhanced helical CT for suspected acute appendicitis. AJR Am J Roentgenol. 1997; 168:405–9. 20. Balthazar EJ, Birnbaum BA, Yee J, Megibow AJ, Roshkow J, Gray C. Acute appendicitis: CT and US correlation in 100 patients. Radiology. 1994; 190:31–5. 21. Malone AJ Jr, Wolf CR, Malmed AS, Melliere BF. Diagnosis of acute appendicitis: value of unenhanced CT. AJR Am J Roentgenol. 1993; 160:763–6. 22. Balthazar EJ, Megibow AJ, Siegel SE, Birnbaum BA. Appendicitis: prospective evaluation with high-resolution CT. Radiology. 1991; 180:21–4. 23. Malone AJ. Unenhanced CT in the evaluation of the acute abdomen: the community hospital experience. Semin Ultrasound CT MR. 1999; 20:68–76. 24. Mullins ME, Kircher MF, Ryan DP, et al. Evaluation of suspected appendicitis in children using limited helical
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CT and colonic contrast material. AJR Am J Roentgenol. 2001; 176:37–41. Lowe LH, Penney MW, Stein SM, et al. Unenhanced limited CT of the abdomen in the diagnosis of appendicitis in children: comparison with sonography. AJR Am J Roentgenol. 2001; 176:31–5. Sivit CJ, Applegate KE, Stallion A, et al. Imaging evaluation of suspected appendicitis in a pediatric population: effectiveness of sonography versus CT. AJR Am J Roentgenol. 2000; 175:977–80. Sivit CJ, Applegate KE, Berlin SC, et al. Evaluation of suspected appendicitis in children and young adults: helical CT. Radiology. 2000; 216:430–3. Garcia Pena BM, Mandl KD, Kraus SJ, et al. Ultrasonography and limited computed tomography in the diagnosis and management of appendicitis in children. JAMA. 1999; 282:1041–6. Rao PM, Rhea JT, Novelline RA, Mostafavi AA, McCabe CJ. Effect of computed tomography of the appendix on treatment of patients and use of hospital resources. N Engl J Med. 1998; 338:141–6. Pena BM, Taylor GA, Lund DP, Mandl KD. Effect of computed tomography on patient management and costs in children with suspected appendicitis. Pediatrics. 1999; 104:440–6. Rhea JT, Rao PM, Novelline RA, McCabe CJ. A focused appendiceal CT technique to reduce the cost of caring for patients with clinically suspected appendicitis. AJR Am J Roentgenol. 1997; 169:113–8. Brewer BJ, Golden GT, Hitch DC, Rudolf LE, Wangensteen SL. Abdominal pain: an analysis of 1000 consecutive cases in a university hospital emergency room. Am J Surg. 1976; 131:219–23.
