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Published online before print December 20, 2002, 10.1148/radiol.2262012097
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(Radiology 2003;226:521-526.)
© RSNA, 2003

Gastrointestinal Imaging

Acute Appendicitis: Effect of Increased Use of CT on Selecting Patients Earlier1

Vassilios Raptopoulos, MD, Georgia Katsou, MD, Max P. Rosen, MD, MPH, Bettina Siewert, MD, S. Nahum Goldberg, MD and Jonathan B. Kruskal, MD, PhD

1 From the Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Ave, Boston, MA 02215 (V.R., G.K., M.P.R., B.S., S.N.G., J.B.K.); and the Department of Radiology, Evangelismos Hospital, Leoforos Vassilisis Sofias, Athens, Greece (G.K.). From the 2000 RSNA scientific assembly. Received December 26, 2001; revision requested February 13, 2002; revision received April 18; accepted June 25. Address correspondence to V.R. (e-mail: vraptopo@caregroup.harvard.edu).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
PURPOSE: To explore the possibility of a relationship between increased use of computed tomography (CT) for diagnosis of appendicitis and increased occurrence of minimal or subtle CT and surgical findings.

MATERIALS AND METHODS: Two groups, each with 50 consecutive patients who underwent CT before appendectomy in 1997 and 2000, were compared. CT scans and surgery-pathology reports were evaluated on a six-grade scale from normal to abscess or inflammatory mass. The demographics, surgical techniques, hospital stay, and grade distribution for the two groups were compared, and the CT results were correlated with surgical findings.

RESULTS: In 1997, CT was performed in 33% (50 of 152) of patients undergoing appendectomy, as compared with 59% (50 of 85) 3 years later (P < .001). There was excellent correlation between surgical-pathologic and CT grades (weighted {kappa}, 0.75; P < .001; Spearman rank correlation, 0.83). There was no significant difference in demographics, rate of surgery, or surgical techniques used, but there was a significant decrease in the median surgical-pathologic grades, from 3.0 to 2.5 (P = .05) for all patients and from 3.5 to 2.6 (P = .003) for patients who underwent CT. Similarly, the median CT grade decreased from 4 to 3 (P < .001). Seven patients had subtle CT findings in 1997 compared with 16 in 2000 (P = .004), and there was a significant decrease in mean hospital stay, from 2.8 days ± 4 (SD) to 1.5 days ± 2 (P = .008).

CONCLUSION: With increased CT use, there were less severe imaging findings, including absence of periappendiceal stranding, and a significant decrease in surgical-pathologic severity of appendiceal disease and hospital stay.

© RSNA, 2003

Index terms: Appendicitis, 751.291 • Appendix, CT, 751.12112, 751.12115 • Computed tomography (CT), utilization, 751.12112, 751.12115


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
The widespread use of computed tomography (CT) for the diagnosis of acute appendicitis is relatively new. Early on, the modality was reserved for evaluation of complications of appendicitis or for patients presenting with atypical symptoms (1–5). Currently, however, CT has become popular among emergency department physicians and surgeons because it has evolved into a quick and accurate examination that provides images that are easy to interpret (6–13). This popularity is due in part to improved scanning techniques, which have followed the evolving CT technology from dynamic incremental scanning (14) to helical scanning (15) and, most recently, to multi–detector row scanning (16). This evolution has led to increased patient comfort and increased accuracy in studies, while the increased availability of scanners has led to an increased use of CT in patients with acute abdominal pain (10,17).

The usefulness of CT has been further strengthened by excellent clinical results despite the variety of often controversial scanning techniques used. Some investigators (8,9,14,18) have observed advantages of using intravenously administered contrast material. Others (19–25) have found studies performed without intravenously administered contrast material to be highly accurate. Similarly, some investigators advocate the use of contrast materials administered gastrointestinally (8,9,14,18), orally (14), or rectally (15), while others do not recommend the use of any contrast material (22). Finally, there are those who advocate focused right lower quadrant scanning (15) and those who have observed value in scanning the entire abdomen and pelvis (8,9). Increasing evidence suggests that nonfocused CT performed with intravenously administered contrast material outweighs the advantages of the focused studies and improves accuracy (9).

Irrespective of technique, however, the CT signs of appendicitis have remained constant. These include enlargement of the appendix with or without contrast material enhancement of the appendiceal wall, periappendiceal stranding or fluid, and presence of an inflammatory mass or abscess in the right lower quadrant (8,14,15,26).

In our clinical practice, we saw an increase in the number of CT scans obtained for the evaluation of acute appendicitis in the late 1990s. During the same period, we also observed an increasing number of patients having appendicitis with subtle CT findings, in particular with borderline enlargement of the appendix and no or minimal periappendiceal stranding. We postulated that increased CT use resulted in earlier scanning that depicted less severe disease. The purpose of this study was to explore the possibility of a relationship between increased use of CT for diagnosis of appendicitis and increased occurrence of minimal or subtle CT and surgical findings.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Patients
We selected two groups, each with 50 consecutive patients who underwent CT before appendectomy: one group in 1997 and the other in 2000. These studies were selected from a computerized search of our institutional database to identify patients who underwent appendectomy from July 1, 1997, to October 1, 2000. Within this span, we selected two periods 3 years apart: one ranging from July 1, 1997, to April 10, 1998 (1997 group) and the other ranging from May 24, 2000, to October 1, 2000 (2000 group). Each period was extended until we identified 50 consecutive patients who underwent CT before appendectomy. The 50 patients in each group were selected from a cohort of 237 patients who underwent appendectomy in the two periods: 152 in 1997 and 85 in 2000.

Image and Report Review
Institutional review board approval for the retrospective review of the charts and images was obtained. We were not required by the board to obtain informed consent from the patients. Each patient received a research identification number, which was used for data analysis. The CT scans were reviewed by two radiologists (V.R. and B.S.) together, and a consensus was reached. Each patient’s surgery and pathology reports were reviewed at the same time by another pair of radiologists (V.R. and G.K.) together, and a consensus was reached. One of the reviewers was in both pairs (V.R.) and was blinded to the results of the other assessment as follows: The other member of the pair chose the patient sequence for review independently and also blocked patient identification. Patient identification did not appear on the images or in the reports at the time of the review.

Additional clinical data were collected by means of computerized search in our institutional data bank by another investigator (M.P.R.). The collected data included demographic information (ie, sex and age), number of appendectomies performed per month, proportion of patients who underwent CT before surgery, surgical technique (laparoscopic or open appendectomy), and length of hospital stay of the patients who underwent appendectomy in the two periods studied.

The hard-copy scans obtained in the 1997 group were reviewed. Because of a change in clinical practice, the scans obtained in the 2000 group were reviewed on a picture archiving and communication system. The surgery and pathology reports were reviewed together, and a combined assessment was made on the basis of a six-grade scale from 0 (normal) to 6 (abscess or inflammatory mass), as defined in the Table. Half grades were allowed. The CT scans were also assessed on the basis of a different six-grade scale from 0 (normal) to 6 (complicated appendicitis), as defined in the Table and shown in Figure 1. Half grades were allowed.


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  		Pathology and Surgery and CT Grades for Appendicitis

 


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  		Figure 1a. Six-grade CT scale of acute appendicitis. (a) Example of grade 0, or normal appendiceal findings. Transverse CT image obtained in a 23-year-old woman with lower abdominal pain for 1 day shows that although the appendix (arrow) is long and larger than 6 mm in diameter, it is filled with gas and has a thin nonenhancing wall. At surgical-pathologic examination, the appendix was normal. (b) Example of grade 1, or probable appendicitis. Transverse CT image obtained in a 32-year-old woman with acute onset of periumbilical pain for 6 hours shows the appendix (arrow) is 7 mm in diameter and has no perceptible lumen; the wall is not enhancing. The surgical-pathologic and CT findings correlated as probable appendicitis. (c) Example of grade 2, or appendicitis. Transverse CT image obtained in a 25-year-old man with 8 hours of generalized abdominal pain eventually localized to the right lower quadrant and mild leukocytosis but no tenderness shows the appendix (arrow) is 8 mm in diameter and filled with fluid. There is no gastrointestinally administered contrast material, but the wall is enhanced with intravenously administered contrast material. There is no periappendiceal stranding. (d) Example of grade 3, or appendicitis and periappendicitis. Transverse CT image obtained in a 42-year-old woman with right lower quadrant pain for a few hours and tenderness at physical examination shows the appendix (arrow) is 9 mm in diameter and filled with fluid; it has a thin but enhancing wall. Stranding of the periappendiceal fat is present. (e) Example of grade 4, or appendicitis with rupture. Transverse CT image obtained in a 30-year-old woman with 6 hours of lower abdominal pain and tenderness shows enlargement and enhancement of the base of the appendix (a) and periappendiceal fluid (arrow). (f) Example of grade 5, or complicated appendicitis. Transverse CT image obtained in a 22-year-old woman with 2 days of mild abdominal pain and increasing nausea and vomiting shows a complex mass (arrows) in the pelvis. The mass contained gas and at surgery was a complex inflammatory appendiceal abscess. There was mild abdominal tenderness, normal gynecologic examination results, and moderate leukocytosis.

 


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  		Figure 1b. Six-grade CT scale of acute appendicitis. (a) Example of grade 0, or normal appendiceal findings. Transverse CT image obtained in a 23-year-old woman with lower abdominal pain for 1 day shows that although the appendix (arrow) is long and larger than 6 mm in diameter, it is filled with gas and has a thin nonenhancing wall. At surgical-pathologic examination, the appendix was normal. (b) Example of grade 1, or probable appendicitis. Transverse CT image obtained in a 32-year-old woman with acute onset of periumbilical pain for 6 hours shows the appendix (arrow) is 7 mm in diameter and has no perceptible lumen; the wall is not enhancing. The surgical-pathologic and CT findings correlated as probable appendicitis. (c) Example of grade 2, or appendicitis. Transverse CT image obtained in a 25-year-old man with 8 hours of generalized abdominal pain eventually localized to the right lower quadrant and mild leukocytosis but no tenderness shows the appendix (arrow) is 8 mm in diameter and filled with fluid. There is no gastrointestinally administered contrast material, but the wall is enhanced with intravenously administered contrast material. There is no periappendiceal stranding. (d) Example of grade 3, or appendicitis and periappendicitis. Transverse CT image obtained in a 42-year-old woman with right lower quadrant pain for a few hours and tenderness at physical examination shows the appendix (arrow) is 9 mm in diameter and filled with fluid; it has a thin but enhancing wall. Stranding of the periappendiceal fat is present. (e) Example of grade 4, or appendicitis with rupture. Transverse CT image obtained in a 30-year-old woman with 6 hours of lower abdominal pain and tenderness shows enlargement and enhancement of the base of the appendix (a) and periappendiceal fluid (arrow). (f) Example of grade 5, or complicated appendicitis. Transverse CT image obtained in a 22-year-old woman with 2 days of mild abdominal pain and increasing nausea and vomiting shows a complex mass (arrows) in the pelvis. The mass contained gas and at surgery was a complex inflammatory appendiceal abscess. There was mild abdominal tenderness, normal gynecologic examination results, and moderate leukocytosis.

 


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  		Figure 1c. Six-grade CT scale of acute appendicitis. (a) Example of grade 0, or normal appendiceal findings. Transverse CT image obtained in a 23-year-old woman with lower abdominal pain for 1 day shows that although the appendix (arrow) is long and larger than 6 mm in diameter, it is filled with gas and has a thin nonenhancing wall. At surgical-pathologic examination, the appendix was normal. (b) Example of grade 1, or probable appendicitis. Transverse CT image obtained in a 32-year-old woman with acute onset of periumbilical pain for 6 hours shows the appendix (arrow) is 7 mm in diameter and has no perceptible lumen; the wall is not enhancing. The surgical-pathologic and CT findings correlated as probable appendicitis. (c) Example of grade 2, or appendicitis. Transverse CT image obtained in a 25-year-old man with 8 hours of generalized abdominal pain eventually localized to the right lower quadrant and mild leukocytosis but no tenderness shows the appendix (arrow) is 8 mm in diameter and filled with fluid. There is no gastrointestinally administered contrast material, but the wall is enhanced with intravenously administered contrast material. There is no periappendiceal stranding. (d) Example of grade 3, or appendicitis and periappendicitis. Transverse CT image obtained in a 42-year-old woman with right lower quadrant pain for a few hours and tenderness at physical examination shows the appendix (arrow) is 9 mm in diameter and filled with fluid; it has a thin but enhancing wall. Stranding of the periappendiceal fat is present. (e) Example of grade 4, or appendicitis with rupture. Transverse CT image obtained in a 30-year-old woman with 6 hours of lower abdominal pain and tenderness shows enlargement and enhancement of the base of the appendix (a) and periappendiceal fluid (arrow). (f) Example of grade 5, or complicated appendicitis. Transverse CT image obtained in a 22-year-old woman with 2 days of mild abdominal pain and increasing nausea and vomiting shows a complex mass (arrows) in the pelvis. The mass contained gas and at surgery was a complex inflammatory appendiceal abscess. There was mild abdominal tenderness, normal gynecologic examination results, and moderate leukocytosis.

 


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  		Figure 1d. Six-grade CT scale of acute appendicitis. (a) Example of grade 0, or normal appendiceal findings. Transverse CT image obtained in a 23-year-old woman with lower abdominal pain for 1 day shows that although the appendix (arrow) is long and larger than 6 mm in diameter, it is filled with gas and has a thin nonenhancing wall. At surgical-pathologic examination, the appendix was normal. (b) Example of grade 1, or probable appendicitis. Transverse CT image obtained in a 32-year-old woman with acute onset of periumbilical pain for 6 hours shows the appendix (arrow) is 7 mm in diameter and has no perceptible lumen; the wall is not enhancing. The surgical-pathologic and CT findings correlated as probable appendicitis. (c) Example of grade 2, or appendicitis. Transverse CT image obtained in a 25-year-old man with 8 hours of generalized abdominal pain eventually localized to the right lower quadrant and mild leukocytosis but no tenderness shows the appendix (arrow) is 8 mm in diameter and filled with fluid. There is no gastrointestinally administered contrast material, but the wall is enhanced with intravenously administered contrast material. There is no periappendiceal stranding. (d) Example of grade 3, or appendicitis and periappendicitis. Transverse CT image obtained in a 42-year-old woman with right lower quadrant pain for a few hours and tenderness at physical examination shows the appendix (arrow) is 9 mm in diameter and filled with fluid; it has a thin but enhancing wall. Stranding of the periappendiceal fat is present. (e) Example of grade 4, or appendicitis with rupture. Transverse CT image obtained in a 30-year-old woman with 6 hours of lower abdominal pain and tenderness shows enlargement and enhancement of the base of the appendix (a) and periappendiceal fluid (arrow). (f) Example of grade 5, or complicated appendicitis. Transverse CT image obtained in a 22-year-old woman with 2 days of mild abdominal pain and increasing nausea and vomiting shows a complex mass (arrows) in the pelvis. The mass contained gas and at surgery was a complex inflammatory appendiceal abscess. There was mild abdominal tenderness, normal gynecologic examination results, and moderate leukocytosis.

 


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  		Figure 1e. Six-grade CT scale of acute appendicitis. (a) Example of grade 0, or normal appendiceal findings. Transverse CT image obtained in a 23-year-old woman with lower abdominal pain for 1 day shows that although the appendix (arrow) is long and larger than 6 mm in diameter, it is filled with gas and has a thin nonenhancing wall. At surgical-pathologic examination, the appendix was normal. (b) Example of grade 1, or probable appendicitis. Transverse CT image obtained in a 32-year-old woman with acute onset of periumbilical pain for 6 hours shows the appendix (arrow) is 7 mm in diameter and has no perceptible lumen; the wall is not enhancing. The surgical-pathologic and CT findings correlated as probable appendicitis. (c) Example of grade 2, or appendicitis. Transverse CT image obtained in a 25-year-old man with 8 hours of generalized abdominal pain eventually localized to the right lower quadrant and mild leukocytosis but no tenderness shows the appendix (arrow) is 8 mm in diameter and filled with fluid. There is no gastrointestinally administered contrast material, but the wall is enhanced with intravenously administered contrast material. There is no periappendiceal stranding. (d) Example of grade 3, or appendicitis and periappendicitis. Transverse CT image obtained in a 42-year-old woman with right lower quadrant pain for a few hours and tenderness at physical examination shows the appendix (arrow) is 9 mm in diameter and filled with fluid; it has a thin but enhancing wall. Stranding of the periappendiceal fat is present. (e) Example of grade 4, or appendicitis with rupture. Transverse CT image obtained in a 30-year-old woman with 6 hours of lower abdominal pain and tenderness shows enlargement and enhancement of the base of the appendix (a) and periappendiceal fluid (arrow). (f) Example of grade 5, or complicated appendicitis. Transverse CT image obtained in a 22-year-old woman with 2 days of mild abdominal pain and increasing nausea and vomiting shows a complex mass (arrows) in the pelvis. The mass contained gas and at surgery was a complex inflammatory appendiceal abscess. There was mild abdominal tenderness, normal gynecologic examination results, and moderate leukocytosis.

 


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  		Figure 1f. Six-grade CT scale of acute appendicitis. (a) Example of grade 0, or normal appendiceal findings. Transverse CT image obtained in a 23-year-old woman with lower abdominal pain for 1 day shows that although the appendix (arrow) is long and larger than 6 mm in diameter, it is filled with gas and has a thin nonenhancing wall. At surgical-pathologic examination, the appendix was normal. (b) Example of grade 1, or probable appendicitis. Transverse CT image obtained in a 32-year-old woman with acute onset of periumbilical pain for 6 hours shows the appendix (arrow) is 7 mm in diameter and has no perceptible lumen; the wall is not enhancing. The surgical-pathologic and CT findings correlated as probable appendicitis. (c) Example of grade 2, or appendicitis. Transverse CT image obtained in a 25-year-old man with 8 hours of generalized abdominal pain eventually localized to the right lower quadrant and mild leukocytosis but no tenderness shows the appendix (arrow) is 8 mm in diameter and filled with fluid. There is no gastrointestinally administered contrast material, but the wall is enhanced with intravenously administered contrast material. There is no periappendiceal stranding. (d) Example of grade 3, or appendicitis and periappendicitis. Transverse CT image obtained in a 42-year-old woman with right lower quadrant pain for a few hours and tenderness at physical examination shows the appendix (arrow) is 9 mm in diameter and filled with fluid; it has a thin but enhancing wall. Stranding of the periappendiceal fat is present. (e) Example of grade 4, or appendicitis with rupture. Transverse CT image obtained in a 30-year-old woman with 6 hours of lower abdominal pain and tenderness shows enlargement and enhancement of the base of the appendix (a) and periappendiceal fluid (arrow). (f) Example of grade 5, or complicated appendicitis. Transverse CT image obtained in a 22-year-old woman with 2 days of mild abdominal pain and increasing nausea and vomiting shows a complex mass (arrows) in the pelvis. The mass contained gas and at surgery was a complex inflammatory appendiceal abscess. There was mild abdominal tenderness, normal gynecologic examination results, and moderate leukocytosis.

 
Imaging Procedure
All 50 scans in the 1997 group and 12 of the 50 scans in the 2000 group were obtained with a conventional helical scanner (CTi; GE Medical Systems, Milwaukee, Wis). The other 38 scans in the 2000 group were obtained with a four–detector row scanner (Qxi; GE Medical Systems). Our routine protocol for both groups was similar. Unless clinically contraindicated, a 100-mL bolus of ioversol 68% (Optiray 320; Mallinckrodt, St Louis, Mo) was injected intravenously with a mechanical injector at 2.5 mL/sec, with a 60-second scanning delay. We used 5-mm collimation and a pitch of 1.5 for single-detector helical CT scanning. For multi–detector row scanning, we used 5-mm collimation and a pitch of 3, with a 60-mm table travel per gantry rotation. If tolerated, 800 mL of contrast material (Readi-Cat 2; E-Z-Em, Westbury, NY) was administered orally 1 hour before scanning.

Statistical Analysis
A commercially available computer program (Minitab, State College, Pa) was used for statistical analysis. The {chi}2 test was used to compare differences in proportions between the two groups. The Student t test was used to compare differences in interval values between the two groups. A two-sample Mann-Whitney rank test was used to compare differences in ordinal values between the two groups (eg, CT and pathologic grades). Surgical-pathologic results were correlated with CT results by using {kappa} statistic analysis and Spearman rank correlation. For the {kappa} statistics, the grade numbers were rounded up or down by 0.5, and grades 0 and 1 were combined to grade 1. A P value of <=.05 was considered to indicate a statistically significant difference (27).


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 
The 1997 group consisted of 152 consecutive patients who underwent appendectomy during a 9.3-month period, with an average of 16.3 appendectomies per month. In the 2000 group, 3 years later, 85 consecutive patients underwent appendectomy during a 4.2-month period, with an average of 20.2 appendectomies per month, which was not significantly different from the 1997 group average (P = .96). There was no significant difference in surgical technique (laparoscopic vs conventional open appendectomy) in the two groups. Of 152 appendectomies performed in the 1997 group, 130 (86%) were laparoscopic and 22 (14%) were open appendectomy. In the 2000 group of 85 appendectomies, 76 (89%) were laparoscopic and nine (11%) were conventional (P = .724).

There was also no significant difference in the age or sex of the patients between the two periods. The mean patient age in the 1997 group was 37 years ± 17 (SD), as compared with 34 years ± 15 in the 2000 group (P = .15). Of the 152 patients of the 1997 group, 72 (47%) were men and 80 (53%) were women, while in the 2000 group of 85 patients, 48 (56%) were men and 37 (44%) were women (P = .227). Thus, there was no significant difference in number of appendectomies per month, surgical technique used, or sex or age of patients between the two groups.

There was, however, a significant decrease in mean hospital stay, from 2.8 days ± 4 in the 1997 group to 1.5 days ± 2 in the 2000 group (P = .008). Conversely, the proportion of patients who underwent appendectomy and preoperative CT increased significantly from 1997 (50 [33%] of 152) to 2000 (50 [59%] of 850 (P < .001).

Review of the CT scans revealed a significant decrease in CT grade, from a median of 4 (interquartile range, 3–5) in 1997 to a median of 3 (interquartile range, 2–3) in 2000 (95% CI: 0.5, 1.5; P < .001) (Fig 2). Similarly, there was a significant increase in CT scans with subtle findings (CT grade < 3). Seven patients in 1997 did not have periappendiceal stranding or other periappendiceal abnormality (CT grade < 3), as compared with 16 patients in 2000 (P = .004).



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  		Figure 2a. Graphs illustrate frequency distribution of CT grades for consecutive patients who underwent CT before appendectomy in (a) 1997 (n = 50) and (b) 2000 (n = 50). (a) In 1997, the distribution was skewed, with a peak in higher grades and a mean of 3.6 ± 1.2. The horizontal box plot shows the median CT grade was 4, and the interquartile range was between 3 and 5. (b) In 2000, the distribution shifted to almost normal, with a mean of 2.8 ± 1.0. The horizontal box plot shows that the median CT grade decreased to the middle grade of 3, and the interquartile range was between 2 and 3.

 


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  		Figure 2b. Graphs illustrate frequency distribution of CT grades for consecutive patients who underwent CT before appendectomy in (a) 1997 (n = 50) and (b) 2000 (n = 50). (a) In 1997, the distribution was skewed, with a peak in higher grades and a mean of 3.6 ± 1.2. The horizontal box plot shows the median CT grade was 4, and the interquartile range was between 3 and 5. (b) In 2000, the distribution shifted to almost normal, with a mean of 2.8 ± 1.0. The horizontal box plot shows that the median CT grade decreased to the middle grade of 3, and the interquartile range was between 2 and 3.

 
Chart review revealed a significant decrease in the surgical-pathologic appendicitis grade at surgeries performed in 2000, as compared with those performed in 1997 (Fig 3). This decrease was observed in both the cohort of patients with appendectomy and the subgroup of patients who underwent preoperative CT. Of all 237 patients who underwent appendectomy, the 152 patients in 1997 had a median surgical-pathologic grade of 3 (interquartile range, 2.0–3.8). This was significantly (P = .05) higher than the median grade of 2.5 (interquartile range, 2–3.5) for the 85 patients who underwent appendectomy in 2000 (95% CI: 0.0, 0.5) (Fig 3a). In the subgroups of 100 patients who underwent preoperative CT, the difference was greater (Fig 3b). The median surgical-pathologic grade for the 50 patients who underwent scanning in 1997 was 3.5 (interquartile range, 3.0–4.5), as compared with 2.6 (interquartile range, 2–4) in the 50 who underwent scanning in 2000 (95% CI: 0.3, 1.0; P < .003).



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  		Figure 3a. Box plots of surgical-pathologic grades show the median (thick horizontal line), interquartile range (box), and range (of all grades, vertical lines) for patients who underwent appendectomy in 1997 and 2000. (a) All patients who underwent appendectomy (n = 237) are included. The median surgical-pathologic grade for the 152 patients in the 1997 group was 3.0 (interquartile range, 2.0-3.8). This is significantly (P = .05) higher than the median grade for the 85 patients in the 2000 group, 2.5 (interquartile range, 2.0-3.5). (b) Only those patients who underwent CT before appendectomy (50 in each group) are included. The median grade for 1997 was 3.5 (interquartile range, 3.0-4.5). This is significantly (P < .003) higher than the median grade for 2000, 2.6 (interquartile range, 2-4).

 


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  		Figure 3b. Box plots of surgical-pathologic grades show the median (thick horizontal line), interquartile range (box), and range (of all grades, vertical lines) for patients who underwent appendectomy in 1997 and 2000. (a) All patients who underwent appendectomy (n = 237) are included. The median surgical-pathologic grade for the 152 patients in the 1997 group was 3.0 (interquartile range, 2.0-3.8). This is significantly (P = .05) higher than the median grade for the 85 patients in the 2000 group, 2.5 (interquartile range, 2.0-3.5). (b) Only those patients who underwent CT before appendectomy (50 in each group) are included. The median grade for 1997 was 3.5 (interquartile range, 3.0-4.5). This is significantly (P < .003) higher than the median grade for 2000, 2.6 (interquartile range, 2-4).

 
In both groups, the surgical-pathologic appendicitis grade for those patients who did not undergo CT was significantly lower than the grade for those who did. In 1997, the median grade for the 50 patients who underwent CT preoperatively was 3.5 (interquartile range, 3.0–4.5), which was higher than the median grade of 2.5 (interquartile range, 2–3; 95% CI: 0.5, 1.5; P < .001) for the 102 who did not. In 2000, the difference decreased but remained significantly different: median grade of 2.5 (interquartile range, 2–4) for the 50 patients who underwent CT preoperatively and 2.0 (interquartile range, 2–3) for the 35 who did not undergo CT (95% CI: 0.0, 1.3; P = .006).

Finally, there was a close correlation between the CT and surgical-pathologic grades. The weighted {kappa} statistic was 0.75 (P < .001), which indicates substantial to almost perfect agreement. The Spearman rank correlation between the two series was 0.83 (P < .001) (Fig 4).



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  		Figure 4. Regression plot for patients who underwent CT before appendectomy (n = 100) shows excellent correlation (Spearman rank correlation, 0.83) between the surgical-pathologic (Surg/Path) and CT grades (Y = 0.468 + 0.854X, r2 = 0.7). The solid line is the regression line, the lines of small dashes are the 95% CI, and the lines of long and short dashes are the 95% prediction interval.

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
REFERENCES
 
The use of CT as a diagnostic examination for acute appendicitis has increased during the past few years (17,28). This increased use is attributed to many factors, including the high accuracy, availability, and speed of the examination; patient tolerance; and ease of interpretation. Results from numerous articles (8,9,14,15,17,18,21–24) show CT to have high accuracy irrespective of the protocol used. Interpretation of findings is relatively easy, and clinicians feel comfortable reviewing the images; strong agreement between radiology resident and staff interpretations of CT scans has been shown (13,29). This agreement suggests that it is safe for radiology house staff to make diagnoses after routine clinical hours. Also, the results of CT are available quickly. CT is not only considerably less operator dependent than is ultrasonography but also more accurate (1,21,29).

Finally, the accuracy of CT is far superior to that of conventional radiography of the abdomen (31). Owing to the advent of helical CT and, more recently, multi–detector row CT, the examination is now performed quickly and tolerated well by acutely ill patients, and the improved technology and increased use have raised confidence in diagnoses (20). For all these reasons, the use of CT in the diagnosis of appendicitis is increasing (17,28). Our study results also show increased use of CT before appendectomy. During a 3-year period, we saw a significant (79%) increase in the use of CT for patients undergoing appendectomy—from 33% to 59%.

The increased use of CT for the diagnosis of acute appendicitis parallels the general increased use of CT for the assessment of right lower abdominal pain where nonappendiceal abnormalities are detected frequently, many of which do not necessitate surgical treatment (8,17,24,32). As the use of CT in patients with acute abdominal pain increases and the technology improves, the selection of patients who will undergo CT inevitably will become less stringent. Thus, as the indication for this examination has progressed from problem solving to frontline diagnosis, patients have undergone scanning earlier and with less severe symptoms.

In our study, significantly more patients underwent CT before appendectomy in 2000 than in 1997. In addition, the median surgical-pathologic grade of acute appendicitis was significantly lower, by 0.5 grade, in 2000, as compared with the grade in 1997. This difference was even larger, by 0.9 grade, in the patients who underwent CT before surgery, and these results paralleled those of CT finding grading. This finding suggests that in the 2000 group there was increased use of CT in those patients with less severe changes of acute appendicitis. This sequence of events suggests that, most likely, CT was performed earlier in the course of the disease.

Although there was no difference in age, sex, or surgical technique in the two groups, the increased use of CT coincided with a significant decrease in hospital stay. There was a decrease of more than 1 full day of hospital stay in the patients who underwent CT before appendectomy in 1997, as compared with the number in 2000: from a mean of 2.8 days ± 4 to a mean of 1.5 days ± 2 (P = .008). These findings support the notion that decreasing the threshold for performing CT in patients with acute appendicitis resulted in CT being performed in less ill patients. Whether this was cost-effective was not measured, and we do not know whether increased use was a result of overuse. Others (7,17,33) have shown that increased use of CT in the emergency department not only improves physicians’ confidence but also decreases hospital admissions and leads to more timely surgical intervention while reducing use of resources.

In our study, the surgical-pathologic grade for patients who did not undergo CT was significantly lower than the grade for those who did in both the 1997 and 2000 groups. This finding may suggest that, although CT was used more often, it was not used indiscriminately and was still reserved for sicker patients. This finding also suggests that patients with classic symptoms undergo surgery faster (thus the lower surgical-pathologic grade) than do those with less typical presenting symptoms, in whom the diagnosis may be delayed and often necessitates CT.

Furthermore, the effect of CT on the management of acute appendicitis is considerable. Its use has decreased the rate of negative appendectomies (6,18,28,33). Conversely, use of CT decreased the number of cases of appendiceal perforation (6,33). In addition to enabling accurate diagnoses, CT can be used to guide treatment by helping in the identification of patients with perforation and phlegmonous masses or abscesses, who may be treated with antibiotics or CT-guided abscess drainage and interval appendectomy (34,35).

Although we observed a significant correlation when we compared the surgical-pathologic grades with the CT results, Weyant et al (28) did not. In a multivariate analysis, these investigators reported no correlation between the CT depiction of free air or fluid, the appendix, and/or fat stranding in the mesentery or around the cecum and the pathologic findings, such as acute, gangrenous, or perforated appendicitis. Our study differs in that we did not correlate specific findings. Instead, we used CT imaging findings to grade the severity of diagnosis and surgical-pathologic results to grade the severity of disease. Results of regression plot analysis showed a significant correlation between the CT and surgical-pathologic grades. Furthermore, in contrast to Weyant et al (28), we reviewed the actual CT scans rather than relied on the radiology reports, which can contain inconsistent descriptions of individual findings.

A limitation of this study was the selection of patients who were known to have undergone a specific surgery (appendectomy) and who had a high probability of having a particular final diagnosis (acute appendicitis). These factors lead to test review bias (36), which leads to overestimation of test sensitivity. Since our goal was not to measure the accuracy of the imaging examination, the effects of this bias were less pronounced. Furthermore, to decrease this bias, the reviewers graded the severity of the CT findings without knowledge of the severity of the pathologic findings.

In this study, with the increased use of CT in patients with acute appendicitis, patients underwent scanning earlier, and periappendiceal stranding was not present in a large number of cases. Since there was a good correlation between the pathologic and CT grades of disease severity, the less severe disease observed with the increased use of CT in this study may have indicated the earlier detection of appendicitis and the earlier initiation of treatment, which may explain the significant decrease in hospital stay.


   FOOTNOTES
 
Author contributions: Guarantor of integrity of entire study, V.R.; study concepts, V.R., G.K.; study design, V.R., M.P.R.; literature research, V.R.; clinical studies, V.R., G.K., B.S.; data acquisition, V.R., G.K.; data analysis/interpretation, V.R., S.N.G.; statistical analysis, V.R.; manuscript preparation, V.R., J.B.K.; manuscript definition of intellectual content and editing, V.R., M.P.R., S.N.G., J.B.K.; manuscript revision/review and final version approval, V.R.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 

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