DOI: 10.1148/radiol.2413051896
(Radiology 2006;241:780-786.)
© RSNA, 2006
Perforated versus Nonperforated Acute Appendicitis: Accuracy of Multidetector CT Detection1
Sarah D. Bixby, MD,
Brian C. Lucey, MD,
Jorge A. Soto, MD,
Jens M. Theysohn, MD,
Al Ozonoff, PhD and
Jose C. Varghese, MD
1 From the Division of Body Imaging, Department of Radiology, Boston University Medical Center, Boston, Mass (S.D.B., B.C.L., J.A.S., J.M.T., J.C.V.); and Department of Biostatistics, Boston University School of Public Health, Boston, Mass (A.O.). From the 2005 RSNA Annual Meeting. Received November 21, 2005; revision requested January 11, 2006; revision received January 17; accepted February 6; final version accepted March 20.
Address correspondence to S.D.B., Department of Radiology, Children's Hospital Boston, 300 Longwood Ave, Boston, MA 02115 (e-mail: sarah.bixby{at}childrens.harvard.edu).
 |
ABSTRACT
|
|---|
Purpose: To retrospectively evaluate the accuracy of multidetector computed tomography (CT) in the diagnosis of perforated acute appendicitis by using surgery and pathologic examination combined as the reference standard.
Materials and Methods: The study was institutional review board approved and HIPAA compliant. Informed patient consent was waived. The authors retrospectively identified 244 patients (150 male, 94 female; mean age, 32.8 years; age range, 4–83 years) with pathologically proved acute appendicitis who underwent abdominopelvic multidetector CT. Two radiologists reviewed in consensus the multidetector CT images obtained in all patients for various findings that may be associated with appendiceal perforation. For continuous variables, a comparison of means between the perforated and nonperforated groups was performed by using the Wilcoxon rank sum test. For categorical variables, the sensitivity and specificity of each CT finding for the diagnosis of perforated appendicitis were determined.
Results: The CT findings of abscess (99%), extraluminal gas (98%), and ileus (93%) had the highest specificities for appendiceal perforation; however, the sensitivities of these findings were low: 34%, 35%, and 53%, respectively. The appendix was larger in patients with perforated appendicitis: The mean diameter was 15.1 mm compared with a mean diameter of 11.7 mm in patients with nonperforated appendicitis (P < .001). Appendicolith, free fluid, enlarged abdominal lymph nodes, and enhancement defect in the appendiceal wall were neither highly sensitive nor highly specific for the detection of perforation.
Conclusion: Although certain multidetector CT findings are very specific for the diagnosis of perforated appendicitis, overall multidetector CT sensitivity is poor. Unless abscess or extraluminal gas is present, multidetector CT cannot enable the diagnosis of perforation.
© RSNA, 2006
|
INTRODUCTION
|
|---|
Computed tomography (CT) is having an increasing role in the diagnosis of acute appendicitis, with reported sensitivities of 87%–99% and reported specificities of 92%–99% (1–6). The advent of multidetector CT is expected to help improve the diagnostic accuracy of CT owing to the thinner sections, faster imaging, and improved spatial resolution afforded by this technology. An important aspect of the diagnosis of acute appendicitis is the identification of any associated complications, such as perforation. The diagnosis of perforated appendicitis is important because it is associated with increased morbidity and mortality (7). Also, preoperative knowledge of perforated appendicitis may lead to alterations in the technique and/or timing of surgery (8,9).
According to some study results, multidetector CT can be used to accurately differentiate perforated from nonperforated acute appendicitis (10–14). Many CT criteria have been used to diagnose perforation, but direct signs such as extraluminal gas, abscess, and appendiceal wall defect are reportedly the most strongly associated with perforation (13,14). In our routine clinical practice, we frequently have found inconsistencies between the CT findings and the surgical diagnosis of perforated appendicitis. Thus, the purpose of our study was to retrospectively evaluate the accuracy of multidetector CT in the diagnosis of perforated acute appendicitis by using surgery and pathologic examination combined as the reference standard.
|
MATERIALS AND METHODS
|
|---|
Patient Selection
The institutional review board of Boston University Medical Center approved our retrospective study and waived the requirement for informed patient consent. The study was compliant with the Health Insurance Portability and Accountability Act. We obtained from our pathology department a list of all patients who had undergone appendectomy and pathologic examination of the appendix during a 35-month period, from September 2001 through July 2004. Of the 596 patients listed, 338 were eliminated: Preoperative CT was not performed in 249 patients, and CT was performed by using a single–detector row machine in 89 patients. Of the 258 remaining patients, 14 were eliminated because of the finding of a normal appendix at pathologic examination. This elimination resulted in a final study group of 244 patients in whom preoperative multidetector CT of the abdomen had been performed and inflammation of the appendix had been confirmed at pathologic examination. There were 150 male (mean age, 31.1 years; range, 4–83 years) and 94 female (mean age, 30.8 years; range, 6–82 years) patients (Fig 1); their overall mean age was 32.8 years (range, 4–83 years).
Data Collection and Reference Standard
We retrospectively reviewed the patients' medical, surgical, and pathology records (S.D.B., J.C.V.). The peripheral white blood cell count was recorded. Patients were considered to have acute appendicitis if any of the following final diagnoses were described in their pathology or surgical report: acute appendicitis, acute suppurative appendicitis, gangrenous appendicitis, or perforated appendicitis. The surgical and pathology reports combined were considered the reference standard with regard to the presence of appendiceal perforation. Surgery was performed within 24 hours after multidetector CT in all but six patients. These six patients were treated with an extended course of intravenous antibiotics, with or without percutaneous abscess drainage, before elective appendectomy. The mean time to surgery for these patients was 66 days (range, 11–108 days).
Multidetector CT Technique
All multidetector CT examinations were performed by using a four–detector row CT machine (model MX8000; Phillips Medical Systems, Andover, Mass) with a section collimation of 3.2 mm reconstructed at 1.6-mm intervals, 120–140 kVp, and 200–240 mAs. Images were acquired from the dome of the diaphragm through the pubic symphysis. The multidetector CT protocol used in the 244 patients varied as follows: 201 (82.4%) patients received oral and intravenous contrast materials, 33 (13.5%) received oral contrast material only (owing to previous contrast material reaction or renal dysfunction), seven (2.9%) received neither oral nor intravenous contrast material owing to a renal stone protocol, two (0.8%) received rectal and intravenous contrast materials, and one (0.4%) received oral and rectal contrast materials.
In the patients who received an oral preparation, 750 mL of a 2.1% barium sulfate suspension (Redi-Cat; Ez-Em, Westbury, NY) was administered 90–120 minutes before CT scanning. The three patients who received rectal contrast material were placed on the CT table, and 1500 mL of a 3% diatrizoate meglumine solution (Gastrografin; Bristol-Myers Squibb, Wallingford, Conn) was administered by means of gravity drip through a rectal catheter. For all intravenous contrast material–enhanced examinations, 100–120 mL of ioversol (Optiray, 320 mg of iodine per milliliter; Mallinckrodt, St Louis, Mo) was injected at a rate of 2–3 mL/sec through an intravenous catheter placed in the antecubital fossa with a scanning delay of 60 seconds.
Image Interpretation
All multidetector CT images were retrospectively reviewed at a picture archiving and communication system workstation by two radiologists (B.C.L and J.C.V., with 5 and 10 years experience, respectively) in consensus, without prior knowledge of the patients' surgical or pathology results. Coronal and sagittal reconstructions were obtained and reviewed, when required, by using computer software (Voxar 3D; Barco, Framingham, Mass) that was incorporated directly into the picture archiving and communications system. This configuration enabled immediate image reconstruction at the primary interpreting workstation without the imaging data having to be transferred to a separate three-dimensional workstation. These reconstructions were not performed in all cases but rather as a problem-solving tool in some cases.
The images were analyzed for the presence of an appendix, signs of inflammation, and any associated complications. The following findings pertaining to the presence or absence of perforation were recorded: (a) appendicolith, (b) cecal wall thickening, (c) peritonitis, (d) enlarged mesenteric lymph node, (e) free fluid, (f) focal wall enhancement defect, (g) ileus, (h) extraluminal gas, (i) abscess and abscess size, and (j) appendix diameter.
Appendicolith was defined as a well-defined, radiopaque, round or oval structure within the appendix that was well separated from any contrast material that may have been present within the cecum. Cecal wall thickening was determined subjectively to be thickening of the cecal wall such that this wall was thicker than the ascending colon wall. Peritonitis referred to increased attenuation and marked stranding of the mesenteric fat at the right side of the pelvis and/or the lower part of the abdomen. Enlarged mesenteric lymph nodes were nodes with a short axis diameter greater than 5 mm. Free fluid referred to extraluminal fluid attenuation in the abdomen or the pelvis, with no enhancing rim. Focal wall enhancement defect referred to a discontinuity in the ring enhancement of the appendiceal wall after intravenous contrast material administration. Ileus was defined as a fluid-filled dilatation of the small bowel of 3.0 cm or larger. Extraluminal gas referred to focal areas of free gas outside of the bowel lumen. Abscess was defined as a well-defined focal fluid collection with a thick wall that enhanced with intravenous contrast material administration. The appendiceal diameter was the maximal short-axis diameter of the appendix measured by using electronic calipers.
Statistical Analyses
Statistical analyses were performed by using the R statistical package, version 2.0.1 (2005); AccuROC, version 2.5; and AccuCON, version 3.0 (Accumetric, Montreal, Quebec, Canada). A significance level of .05 was used throughout. Measurements of continuous variables—specifically, patient age, white blood cell count, and appendix size—were reported as means, standard deviations, medians, and ranges. Measurements of categorical variables (ie, all other findings) were reported as frequencies and percentages. The Wilcoxon rank sum test was used to compare continuous variable measurements between the two patient groups (perforated vs nonperforated appendicitis).
For all calculations, the surgical and pathologic diagnoses combined formed the reference standard used to determine the presence of appendiceal perforation. The sensitivities and specificities of individual CT findings (with the exception of appendix size) were calculated. Standard 95% confidence intervals were calculated by using an F distribution approximation (15). A comprehensive CT score, calculated as the number of imaging findings present (from 0 to 9), was used as the summary measure for each patient. For example, a patient with enlarged mesenteric lymph nodes, free fluid, and an appendicolith was assigned a score of 3. The sensitivities and specificities of each comprehensive CT score were calculated, and a receiver operating characteristic curve was derived from these data (16). The area under the curve was computed from the empirical receiver operating characteristic curve, and a 95% confidence interval was calculated by using the bootstrap percentile method (17) with 50 000 iterations.
|
RESULTS
|
|---|
Perforated versus Nonperforated Appendicitis
Of the 244 patients, 62 (25.4%) received a diagnosis of perforated appendicitis at surgery, pathologic examination, or both. The ages of the patients in each group (perforated vs nonperforated appendicitis) were not significantly different (P = .24) (Table 1). The mean peripheral white blood cell count was significantly higher in the perforated appendicitis group (P < .001). The appendix was not visualized at CT (most often because of very little abdominal fat) in 10 patients: five in the perforated group and five in the nonperforated group. These 10 patients were still treated surgically because of the overwhelming clinical suspicion of acute appendicitis, which was subsequently confirmed at pathologic examination. The mean appendix diameter was significantly greater in the perforated group (P < .001) (Table 1).
View this table:
[in this window]
[in a new window]
|
Table 1. Age, Appendix Size, and White Blood Cell Count of Patients with Perforated and Nonperforated Appendicitis
|
|
Sensitivity and Specificity of CT Findings
The sensitivities and specificities of the individual multidetector CT findings evaluated (Table 2) indicate that the three findings that were most specific for the diagnosis of perforated appendicitis were extraluminal gas, abscess, and small-bowel ileus, all of which had a specificity higher than 90%. Of these three findings, abscess was the most specific (99%) for perforation. Twenty-three patients had an abscess (mean diameter, 5.6 cm; range, 1.7–14.0 cm). Two diagnoses were false-positive for abscess, and both were made in patients in whom multidetector CT depicted fluid collections adjacent to the appendix; the collections simulated abscesses but were subsequently found at surgery to be simple fluid. Neither of these patients received intravenous contrast material. Extraluminal gas was 98% specific for perforation; however, three diagnoses were false-positive for free gas. These diagnoses were made in thin patients in whom small bubbles of intraluminal bowel gas were incorrectly localized to the peritoneum (Fig 2).
View larger version (137K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 2: Transverse CT image enhanced with oral and intravenous contrast materials and obtained in 33-year-old woman who presented with right lower quadrant pain shows bubble of gas (arrow) close to tip of appendix but thought to lie outside of bowel. This appendix was not perforated at surgery.
|
|
The sensitivity of all multidetector CT findings analyzed was uniformly low (<75%) for the diagnosis of appendiceal perforation (Fig 3, Table 2). The most sensitive (73%) finding was enlarged (5–15-mm short-axis diameter) mesenteric lymph nodes. Interestingly, abscess was the least sensitive (34%) but most specific (99%) indicator of perforation.
View larger version (100K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 3: Transverse CT image enhanced with oral and intravenous contrast materials and obtained in 21-year-old man who presented with right lower quadrant pain shows enhancement defect (arrowhead) in appendiceal wall. This appendix was not perforated at surgery.
|
|
Comprehensive CT Score
Analysis of the effects of the comprehensive CT score on the sensitivity and specificity of multidetector CT (Table 3) revealed that low comprehensive CT scores were associated with high sensitivity and low specificity in the diagnosis of perforation, whereas high scores had low sensitivity and high specificity. The area under the curve for the comprehensive CT score was 0.812 (95% confidence interval: 0.741, 0.875) (Fig 4).
View larger version (8K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 4: Receiver operating characteristic curve derived from sensitivities and specificities of comprehensive CT scores. Dotted line represents curve for a test that is no better than chance. Continuous line represents curve derived from current study data. Area under curve was 0.812 (95% confidence interval: 0.741, 0.875) in current study.
|
|
|
DISCUSSION
|
|---|
Appendiceal perforation alters both the clinical management and the patient outcome of acute appendicitis. Localized perforation with diffuse peritonitis is one of the most frequently reported reasons—second only to dense adhesions—given for changing from laparoscopic appendectomy to an open procedure (9). In patients with complications related to appendiceal perforation, initial conservative management may reduce the extent of subsequent surgery (18,19). These conservative measures include initial treatment with intravenous antibiotics and percutaneous drainage when required (18–20). These strategies allow appendectomy to be performed electively at a later date and thereby obviate the two-stage surgical approach (21). In the surgical literature, perforation is noted to occur in 18%–35% of cases of acute appendicitis (22–25). The rate of appendiceal perforation in our study population (25.4%) was well within this range.
The use of CT to distinguish perforated from nonperforated appendicitis has been assessed by various investigators (10–14). Grading systems and regression models that accurately correlate the inflammatory changes noted at CT with the actual severity of disease have been devised (26). Specific CT findings have been reported to be predictive of perforation. In one study involving 86 patients with appendicitis (12), extraluminal air and moderate to severe periappendiceal inflammatory stranding were found to be important findings in the prediction of perforation. In another study involving the examination of 94 patients with appendicitis (13), the presence of one or more of the findings of extraluminal gas, abscess, extraluminal appendicolith, and/or enhancement defect in the appendiceal wall was found to be 96.4% sensitive and 100% specific for the diagnosis of perforated appendicitis. In that same study, the most sensitive individual CT finding was enhancement defect in the appendiceal wall, which was 64.3% sensitive and 100% specific for the diagnosis of perforation.
The lower sensitivity of the CT findings in our study is largely related to the sample size. Our patient group was nearly three times larger than the patient group in the other study (13). In addition, the increased sensitivity of CT in the detection of perforated appendicitis in that study was heavily influenced by the frequent finding of focal enhancement defect in the appendiceal wall; however, this finding did not have high sensitivity in our study.
By examining the data in a large patient population and limiting our investigation to patients who were imaged with multidetector CT technology, we minimized the observance of volume-averaging artifacts that can confound image interpretation. Not surprisingly, we found that the most specific indicators of perforation were extraluminal abscess (99%), gas (98%), and ileus (93%). These three findings, however, had poor sensitivity. No patients in our study had an extraluminal appendicolith, so we did not include this finding in our analysis. Overall, no combination of imaging findings had both high sensitivity and high specificity (ie, values greater than 80%) for the presence of perforation. The area under the curve for the comprehensive CT score (0.812) suggests that CT is not highly accurate for the diagnosis of perforated appendicitis (16). Although CT yields findings that are helpful in evaluating perforation, it should not be relied on for making a definitive diagnosis.
In our study, the patients with clear evidence of an abscess or extraluminal gas were nearly always found to have perforated appendicitis. However, not all patients with perforation present at a stage when these findings can be depicted. Early perforation or microperforation can be challenging to diagnose with CT, and often there is no abscess or extraluminal gas to indicate that the appendix has become perforated. We did not differentiate perforations on the basis of their size or degree, and the clinical importance of microperforations may be worth evaluating in the future. Peritonitis or free fluid is often a misleading sign of appendiceal perforation. In our evaluations, extraluminal fluid and mesenteric stranding were frequently noted at multidetector CT. At surgery and examination of the resected appendix, the patients with these findings were often found to have an inflamed and perforated appendix as the cause of them. However, in other patients, the appendix was not perforated. Accordingly, fluid outside of the appendix and mesenteric inflammation were not accurate distinguishing features of perforation.
Evaluating the enhancement of the appendiceal wall was not helpful in diagnosing perforation, as both the sensitivity and specificity of wall enhancement defect were low. Technical factors and artifacts such as volume averaging may have accounted for the low sensitivity and specificity of this finding. The tendency to misinterpret this finding and the lack of interobserver agreement due to both volume averaging and the orientation of the appendix within the imaging plane were found in another study also (12). Any diagnosis of appendiceal perforation based on the finding of wall enhancement defect is inherently limited because of the potential for substantial variations in interpretation.
There were limitations to our study: First, it was retrospective; therefore, we relied on the completeness of both the surgical and the pathology reports in our analyses. Second, the wide variety of oral, rectal, and intravenous contrast material enhancement protocols used during the course of the study resulted in a heterogeneous study group. The lack of intravenous contrast material administration may have led to the misdiagnosis of abscess in a small number of patients. Third, there was an inherent review bias in our study because of our knowledge that all patients had undergone appendectomy for acute appendicitis. During the review of images, however, the readers were blinded as to whether each patient had perforated or nonperforated appendicitis; thus, the review bias was reduced. Last, it is conceivable that in some patients, a perforation may have occurred during the interval between CT and surgery and thus caused false-negative results. However, all patients, with the exception of six patients who were treated with percutaneous abscess drainage and/or extended antibiotic regimens before undergoing elective appendectomy, underwent surgery within 24 hours after CT. If any patients developed a perforation during this interval, it was probably a small number of them, and we believe that this would not have substantially affected our results.
In conclusion, although certain multidetector CT findings are highly specific for the diagnosis of perforated appendicitis, poor sensitivity limits their clinical usefulness. Ultimately, the presence of perforation may lead to a change in the decision to perform surgery in a patient, and high diagnostic accuracy is required to alter the treatment of patients with this acute abnormality. Abscess, extraluminal gas, and ileus are highly specific for the diagnosis of perforated appendicitis. Relying on the presence of these three features alone, however, would result in nearly half of all patients with perforation being missed. The appendix was larger in the patients who had perforated appendicitis. Although this is a helpful clue for evaluating perforation, there is no absolute size at which perforation always occurs. The presence of an enhancement defect in the appendiceal wall did not have the specificity for perforation that has been previously reported (13). Free fluid, enlarged mesenteric lymph nodes, appendicolith, and peritonitis were not accurate indicators of perforation according to their sensitivities and specificities. Our analysis results indicate that multidetector CT findings are helpful in diagnosing perforated appendicitis, but they cannot be used to definitively detect this abnormality in all patients.
|
ADVANCES IN KNOWLEDGE
|
|---|
- Although certain multidetector CT findings are very specific for the diagnosis of perforated appendicitis, the overall sensitivity of multidetector CT is poor.
- Unless abscess or extraluminal gas is present, multidetector CT cannot enable the diagnosis of appendiceal perforation.
|
FOOTNOTES
|
|---|
Authors stated no financial relationship to disclose.
Author contributions: Guarantors of integrity of entire study, S.D.B., B.C.L.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; literature research, S.D.B., J.M.T., J.C.V.; clinical studies, S.D.B., J.A.S., J.M.T., J.C.V.; statistical analysis, A.O.; and manuscript editing, all authors
|
References
|
|---|
- Lane MJ, Katz DS, Ross BA, et al. Unenhanced helical CT for suspected acute appendicitis. AJR Am J Roentgenol 1997;168:405–409.[Abstract/Free Full Text]
- 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;213:341–346.[Abstract/Free Full Text]
- Rhea JT, Halpern EF, Ptak T, Lawrason JN, Sacknoff R, Novelline RA. The status of appendiceal CT in an urban medical center 5 years after its introduction: experience with 753 patients. AJR Am J Roentgenol 2005;184:1802–1808.[Abstract/Free Full Text]
- Keyzer C, Zalcman M, De Maertelaer V, et al. Comparison of US and unenhanced multi–detector row CT in patients suspected of having acute appendicitis. Radiology 2005;236:527–534.[Abstract/Free Full Text]
- Rao PM, Novelline RA, McCabe CJ, Lawrason JN, Berger DL, Sacknoff R. Helical CT technique for the diagnosis of appendicitis: prospective evaluation of a focused appendix CT examination. Radiology 1997;202(1):139–144.[Abstract/Free Full Text]
- 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(3):141–146.[Abstract/Free Full Text]
- Velanovich V, Satava R. Balancing the normal appendectomy rate with the perforated appendicitis rate: implications for quality insurance. Am Surg 1992;58(4):264–269.[Medline]
- Siewert B, Raptopoulos V, Liu SI, Hodin RA, Davis RB, Rosen MP. CT predictors of failed laparoscopic appendectomy. Radiology 2003;229:415–420.[Abstract/Free Full Text]
- Liu SI, Siewert B, Raptopoulos V, Hodin RA. Factors associated with conversion to laparotomy in patients undergoing laparoscopic appendectomy. J Am Coll Surg 2002;194(3):298–305.[CrossRef][Medline]
- Lin CJ, Chen JD, Tiu CM, et al. Can ruptured appendicitis be detected preoperatively in the ED? Am J Emerg Med 2005;23(1):60–66.[CrossRef][Medline]
- Oliak D, Sinow R, French S, Udani VM, Stamos MJ. Computed tomography scanning for the diagnosis of perforated appendicitis. Am Surg 1999;65(10):959–964.[Medline]
- Foley TA, Earnest F, Nathan MA, Hough DM, Schiller HJ, Hoskin TL. Differentiation of nonperforated from perforated appendicitis: accuracy of CT diagnosis and relationship of CT findings to length of hospital stay. Radiology 2005;235(1):89–96.[Abstract/Free Full Text]
- Horrow MM, White DS, Horrow JC. Differentiation of perforated from nonperforated appendicitis at CT. Radiology 2003;227:46–51.[Abstract/Free Full Text]
- Yeung KW, Chang MS, Hsiao CP. Evaluation of perforated and nonperforated appendicitis with CT. Clin Imaging 2004;28(6):422–427.[CrossRef][Medline]
- McKenzie DP, Vida S, MacKinnon AJ, Onghena P, Clarke DM. Accurate confidence intervals for measures of test performance. Psychiatry Res 1997;69(2-3):207–209.[CrossRef][Medline]
- Obuchowski NA. Receiver operating characteristic curves and their use in radiology. Radiology 2003;229:3–8.[Abstract/Free Full Text]
- Efron B, Tibshirani R. An introduction to the bootstrap. New York, NY: Chapman & Hall, 2003.
- Brown CV, Abrishami M, Muller M, Velmahos GC. Appendiceal abscess: immediate operation or percutaneous drainage? Am Surg 2003;69(10):829–832.[Medline]
- Yamini D, Vargas H, Bongard F, Klein S, Stamos MJ. Perforated appendicitis: is it truly a surgical urgency? Am Surg 1998;64(10):970–975.[Medline]
- Nadler EP, Reblock KK, Vaughan KG, Meza MP, Ford HR, Gaines BA. Predictors of outcome for children with perforated appendicitis initially treated with non-operative management. Surg Infect (Larchmt) 2004;5(4):349–356.
- Flancbaum L, Nosher JL, Brolin RE. Percutaneous catheter drainage of abdominal abscesses associated with perforated viscus. Am Surg 1990;56(1):52–56.[Medline]
- Korner H, Sondenaa K, Soreide JA, et al. Incidence of acute nonperforated and perforated appendicitis: age-specific and sex-specific analysis. World J Surg 1997;21:313–317.[CrossRef][Medline]
- Addiss DG, Shaffer N, Fowler BS, Tauxe RV. The epidemiology of appendicitis and appendectomy in the United States. Am J Epidemiol 1990;132:910–925.[Abstract/Free Full Text]
- Maxwell JM, Ragland JJ. Appendicitis: improvements in diagnosis and treatment. Am Surg 1991;57(5):282–285.[Medline]
- Hale DA, Molloy M, Pearl RH, Schutt DC, Jaques DP. Appendectomy: a contemporary appraisal. Ann Surg 1997;225(3):252–261.[CrossRef][Medline]
- Hansen AJ, Young SW, De Petris G, Tessier DJ, Hernandez JL, Johnson DJ. Histologic severity of appendicitis can be predicted by computed tomography. Arch Surg 2004;139(12):1304–1308.[Abstract/Free Full Text]
Related Article
-
Radiology 2007 243: 302.
[Full Text]
[PDF]
TOP
ABSTRACT
INTRODUCTION
