Affiliations of authors: N. M. Gatto, J. S. Jacobson, Department of Epidemiology, Joseph L. Mailman School of Public Health, Columbia University, New York, NY; H. Frucht, Department of Medicine and Herbert Irving Comprehensive Cancer Center, College of Physicians and Surgeons, Columbia University: V. Sundararajan, Department of Epidemiology and Preventive Medicine, Monash Medical School, Melbourne, Australia; V. R. Grann, A. I. Neugut, Department of Epidemiology, Joseph L. Mailman School of Public Health, and Department of Medicine and Herbert Irving Comprehensive Cancer Center, College of Physicians and Surgeons, Columbia University.
Correspondence to: Alfred I. Neugut, M.D., Ph.D., Division of Medical Oncology, New York-Presbyterian Hospital, 630 West 168th St., PH 18-127, New York, NY 10032 (e-mail: ain1{at}columbia.edu).
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ABSTRACT |
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INTRODUCTION |
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Colonoscopy has been widely used since the 1970s as the primary diagnostic tool to follow up on positive findings from FOBT and on abnormalities found during sigmoidoscopy. In addition, colonoscopy has been recommended as the initial screening tool for individuals at high risk for colorectal cancer (13,14). Although no controlled trials have assessed the efficacy of colonoscopy in reducing colorectal cancer mortality, its similarity to flexible sigmoidoscopy in sensitivity, specificity, and the ability to biopsy or resect adenomas, and its ability to visualize the entire colon suggest that it may be preferable to sigmoidoscopy for screening asymptomatic individuals with average risk of developing colorectal cancer (1316). Furthermore, many believe that the improved survival associated with screening by FOBT and sigmoidoscopy is actually a result of the colonoscopy that is done because of abnormal findings.
In the absence of a randomized controlled trial to compare these two screening strategies, the relative merits of each have been estimated by costbenefit analysis and other modeling tools (1719). A major deterrent to the widespread use of colonoscopy has been the fear of perforating the intestinal wall; at least one group has referred to perforation of the colon as "the most dreaded complication of colonoscopy" (20). Most previous studies of colon perforation have been limited to a single endoscopy practice or center or had small sample sizes (2129). The observed perforation rates have ranged from 1 in 200 to 1 in 5000 (2129). Perforation rates for sigmoidoscopy are believed to be markedly lower but have not been explored extensively.
In this study, we used a large population-based database to compare the incidence of perforation associated with both of these flexible endoscopic procedures and to investigate what factors predict the occurrence of this complication. A better understanding of the relative risk of perforation associated with colonoscopy and sigmoidoscopy will facilitate an evidence-based choice between these two strategies, both for patients and for individuals who make population screening recommendations.
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PATIENTS AND METHODS |
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For this study, we used the summarized denominator file (SUMDENOM), a random 5% sample of Medicare beneficiaries without cancer who resided within the Surveillance, Epidemiology, and End Results Program (SEER)1 population areas (30). We excluded individuals with any cancer because of a concern that we would not be able to distinguish perforations secondary to the procedure from perforations due to the disease. SEER collects data from tumor registries covering approximately 14% of the U.S. population (30,31). Through an identifier, the SEER and SUMDENOM data files have been linked to outpatient and inpatient Medicare claims files for those aged 65 years or older (30). This linked SEERMedicare database was developed jointly by the National Cancer Institute, the Centers for Medicare and Medicaid Services, and the SEER registries.
Sample Selection
All subjects were selected from the Medicare physician/supplier National Claims History (NCH) database. Subjects were aged 65 years or older and had undergone at least one colonoscopy or sigmoidoscopy billed on NCH from 1991 through 1998 (N = 39 286 for colonoscopy and N = 35 298 for sigmoidoscopy). Colonoscopic procedures were identified from the records as colonoscopy with or without biopsy, polypectomy, control of bleeding, or removal of a foreign body (Healthcare Common Procedure Coding System [HCPCS]/the American Medical Associations Common Procedure Terminology [CPT-4] codes 45378, 45379, 45380, 45382, 45383, 45384, and 45385). Sigmoidoscopies were identified from the records as flexible sigmoidoscopy with or without biopsy, polypectomy, control of bleeding, decompression of volvulus, or removal of a foreign body (HCPCS/CPT-4 codes 45330, 45331, 45332, 45333, 45334, 45337, 45338, and 45339).
Outcomes of Interest
Perforations were identified using the International Classification of Diseases 9th revision (ICD-9) codes for perforation of intestine and accidental puncture or laceration during a procedure (ICD-9 codes 569.83 and 998.2). Diagnosis of a perforation and verified date of death were obtained from the linked NCH and Medicare Analysis and Procedure (MEDPAR) databases. To be included in the study, the perforation had to occur within 7 days of the procedure, which was measured as the difference between the date of the procedure and the date of the perforation. Similarly, mortality after a perforation was measured within 14 days and 30 days of a procedure and was determined as the difference between the date of the procedure and the date of death.
Sociodemographic Variables and Comorbidity
Data on age, race/ethnicity, and sex were obtained from the linked NCH and MEDPAR databases. The presence of comorbidity was assessed using the Klabunde adaptation of the DeyoCharlson comorbidity index, which incorporates Medicare physician claims (part B) and hospital claims (part A) (3234). Subjects were coded as having one or more comorbidities if the relevant ICD-9 codes were identified from their records in the 365 days before the date of the procedure or in the 120 days after the date of the procedure.
Indications for the Procedure
The indications for the endoscopic procedure were obtained from the linked NCH and MEDPAR databases. The indications included hemorrhage, anemia, abdominal pain, diverticulosis, weight loss, obstruction, inflammatory bowel disease, and/or diarrhea occurring 030 days before the procedure. The complete list of ICD-9 codes for these indications is available at the Journals Web site http://jncicancerspectrum.oupjournals.org/jnci/content/vol95/issue3/index.shtml. Where none of the aforementioned indications was identified, the procedure was coded as "screening/other" (N = 20 163 for colonoscopy; N = 25 951 for sigmoidoscopy).
Statistical Analysis
Incidence of perforation from a colonoscopy or sigmoidoscopy was defined as the number of perforations per 1000 procedures. Analogously, the incidence of death after a colonoscopy- or sigmoidoscopy-associated perforation was defined as the number of deaths within 7 days per 1000 perforations.
All crude and adjusted odds ratios (ORs), and 95% Wald confidence intervals (CIs) were obtained by using the LOGISTIC procedure in SAS version 8.12 (SAS Institute, Cary, NC). For both colonoscopy and sigmoidoscopy, the crude association between perforation and each of the demographic and clinical characteristics was estimated by using logistic regression. Multivariate logistic regression analyses, which controlled for the effects of all covariates, were used to obtain the adjusted association between the risk of perforation and each of the demographic and clinical variables. Because the univariate and multivariate results were similar, only the multivariate results are reported.
The crude and adjusted relative risks of death (as estimated with ORs) after a colonoscopic or sigmoidoscopic perforation were obtained by modeling death within 14 days and 30 days of a procedure as a function of perforation. The adjusted association controlled for age at the time of the procedure, year of the procedure, sex, race/ethnicity, comorbid conditions, and indication for the procedure.
Multiple logistic regression modeling was also used to compare the risk of perforation as a function of colonoscopy versus sigmoidoscopy, with age at the time of the procedure, year of the procedure, sex, race/ethnicity, comorbid conditions, and indication for the procedure as covariates. All statistical tests were two-sided.
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RESULTS |
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From 1991 through 1998, a total of 39 286 colonoscopies and 35 298 sigmoidoscopies were performed. During this time period, the number of sigmoidoscopies per year decreased and the number of colonoscopies per year increased; 1994 was the first year when more colonoscopies than sigmoidoscopies were performed (Fig. 1).
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Perforation After Colonoscopy
We identified 77 subjects with an intestinal perforation within 07 days after a colonoscopy, corresponding to an incidence of 1.96 per 1000 procedures. Subjects aged 75 years or older had nearly four times the risk of a perforation (OR = 3.7, 95% CI = 1.7 to 8.2 for those aged 7579 years and OR = 3.5, 95% CI = 1.5 to 7.8 for those aged 80 years or older) than those aged 6569 years (Table 2). In univariate analyses, the risk of perforation was positively associated with increasing age (Ptrend<.001) and number of comorbidities (Ptrend<.001) (Table 1
). Neither sex nor race/ethnicity was related to the risk of perforation after a colonoscopy. Compared with subjects who had a screening colonoscopy, an increased risk of perforation was associated with two indications: diverticulosis (OR = 2.3, 95% CI = 1.3 to 4.0) and obstruction (OR = 2.9, 95% CI = 1.3 to 6.7) (Table 2
). No other indications were statistically significantly associated with an increased risk of perforation.
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We identified 31 subjects with an intestinal perforation within 07 days after a sigmoidoscopy, corresponding to an incidence of perforation of 0.88 per 1000 procedures. In multivariate analyses, the risk of perforation among patients aged 80 years and older was nearly three times that among those aged 6569 years (OR = 2.9, 95% CI = 1.1 to 7.9) (Table 2). The risk of perforation was positively associated with increasing age (Ptrend<.001) and number of comorbidities (Ptrend = .03), but not to sex, race/ethnicity, or year of the procedure (Table 1
). Compared with subjects who had a screening sigmoidoscopy, an increased risk of perforation was associated with two indications: diverticulosis (OR = 5.4, 95% CI = 2.4 to 12.4) and abdominal pain (OR = 2.4, 95% CI = 1.1 to 5.4) (Table 2
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Incidence of Death After a Perforation From a Colonoscopy or Sigmoidoscopy
The incidence of death subsequent to a perforation within 14 days of a procedure was 51.9 per 1000 colonoscopic perforations and 64.5 per 1000 sigmoidoscopic perforations. After adjustment for covariates, mortality among those who had a perforation compared with those who did not was nearly ninefold higher in both the colonoscopy group (OR = 9.0, 95% CI = 3.0 to 27.3) and the sigmoidoscopy group (OR = 8.8, 95% CI = 1.6 to 48.5) (Table 3). The results were similar up to 30 days following the procedure (OR = 7.1, 95% CI = 2.8 to 17.7 for colonoscopy; OR = 6.0, 95% CI = 1.5 to 24.2 for sigmoidoscopy).
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The crude OR for perforation from colonoscopy compared with that from sigmoidoscopy was 2.2 (95% CI = 1.5 to 3.4). After adjusting for covariates, the risk of perforation from colonoscopy was still nearly double the risk of perforation from sigmoidoscopy (OR = 1.8, 95% CI = 1.2 to 2.8). During the study period, the risk of perforation from colonoscopy statistically significantly declined (Ptrend = .002), while that from sigmoidoscopy did not. In 1998, the last year of the study period, the incidence of perforation from colonoscopy was 1.84 per 1000 and from sigmoidoscopy was 1.67 per 1000 (Table 1). Since 1995, the incidence of perforation after colonoscopy in the screening/other group has been less than one per 1000 (Fig. 2
).
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Nearly 30% of the perforations from colonoscopy and sigmoidoscopy were coded with ICD-9 code 998.2, which is defined as "an accidental puncture or laceration during a procedure." Using only this ICD-9 code, we found that the crude and adjusted ORs between perforation from colonoscopy compared with perforation from sigmoidoscopy were 2.0 (95% CI = 0.9 to 4.4) and 1.4 (95% CI = 0.6 to 3.3), respectively.
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DISCUSSION |
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Previous studies (2224,2729,35) have found similar perforation rates but have been limited by several features. Most studies had small sample sizes, were conducted in a single medical center, were based on data from either a single endoscopist or a small number of endoscopists, or included only colonoscopies (2224,2729,35). However, several previous studies deserve special mention because of their large sample sizes. Sieg et al. (25) noted that 94 of 160 invited German gastroenterologists participated in a survey of colonoscopy-associated complications. They reported four perforations among 82 416 diagnostic colonoscopies (.05 per 1000 or one in 20 000 procedures) and nine perforations among 14 249 polypectomies (almost one per 200). This is the lowest reported rate of perforation, probably because the study included only perforations that required surgical intervention and because it depended on physician-reported perforations. In a study by Tran et al. (29), investigators reviewed the results of a series of 16 948 diagnostic colonoscopies and 9214 "therapeutic colonoscopies" from one U.S. center. In this study, only those perforations that required surgery were counted, and 11 perforations among the diagnostic colonoscopies (0.6 per 1000 procedures) and 10 perforations among the therapeutic colonoscopies (1.1 per 1000 procedures) were found. In 1979, Fruhmorgen and Demling (21) surveyed 27 hospitals in Germany and found 1.4 perforations per 1000 diagnostic colonoscopies and 3.4 per 1000 colonoscopies with polypectomy. None of these three studies, however, investigated sigmoidoscopy-associated perforation.
One recent study, Anderson et al. (26) explored the risks of perforation after either sigmoidoscopy or colonoscopy. They reported an incidence of 1.9 perforations per 1000 colonoscopies and 0.4 perforations per 1000 sigmoidoscopies. The study compared 10 486 colonoscopies with 49 501 sigmoidoscopies done over 10 years (1987 through 1996) at the Mayo Clinic. The authors found two deaths secondary to perforation (N = 20) from colonoscopy, corresponding to an overall mortality rate after a colonoscopy of 0.02% and an incidence of death after a perforation of 10%, which was higher than the incidence of death after a perforation from colonoscopy in our study (5.2%). The Mayo study (26) was the only other large study to directly compare colonoscopy with sigmoidoscopy. Although it was similar to our study in sample size, it included only patients from a single institution.
Using a Medicare sample, we have conducted the largest study to date of major complications from colonoscopy and sigmoidoscopy. The study was also population-based, with the procedures performed in major academic and specialized centers, community hospitals, clinics, and private offices. However, the databases we used have several limitations. Findings based on Medicare data may not be directly generalizable to people younger than 65 years. Moreover, a 1997 study by Nattinger et al. (36), found that the counties included in the SEER registry had somewhat higher socioeconomic status and were less rural than most counties in the United States. Although the SEER counties were similar to other counties in the density of physician resources, SEER county hospitals had more beds and were more likely to have approval from the Joint Commission on the Accreditation of Hospitals. Consequently, our findings may slightly underestimate the risk of these complications in the overall U.S. population.
Still another possible limitation is that the accuracy of our identification of comorbidity, indications for colonoscopy and sigmoidoscopy, and the diagnosis of perforation itself are dependent on the precision of the diagnostic coding in the Medicare claims data. However, agreement between claims data and medical record abstracts has been found to be greater than 85% for most of the comorbidities in our index (37). An improvement in such agreement was demonstrated between 1977 and 1985 (37), and this may have improved further in the 1990s.
We were unable to determine with 100% validity whether the perforations were a direct consequence of the procedure. Therefore, we restricted the follow-up time to 7 days after the procedure, because we believe that the vast majority of such complications will be recognized within this time frame. Further follow-up would be more likely to include perforations related to the underlying colorectal pathology or other comorbidities. Moreover, when the analysis was restricted to perforations that were coded as accidental punctures or lacerations during a procedure, we found that the relative risk of perforation from colonoscopy compared with that of perforation from sigmoidoscopy did not differ from the full analysis, which also included those perforations coded as perforation of intestine. Thus, if a small number of the perforations detected within 7 days after colonoscopy or sigmoidoscopy were attributable to causes other than the procedure itself, this difference did not depend on the type of procedure.
The risk of perforation after colonoscopy was statistically significantly increased among patients with diverticulosis and obstruction, whereas the risk of perforation after sigmoidoscopy was increased among patients with diverticulosis and abdominal pain. Because patients with diverticuli and circular muscle hypertrophy have distorted colons, intubation may be more difficult. The consequence of difficult intubation may be an increase in perforation, which may also account for perforations in patients with obstruction. The reasons why there was an increased risk of perforation for patients undergoing sigmoidoscopy for the evaluation of abdominal pain are not apparent.
Overall, we found a perforation incidence of nearly two per 1000 colonoscopies, slightly more than twice the perforation incidence from sigmoidoscopy. Perforation incidence declined over the study period for colonoscopy but not for sigmoidoscopy, with the two procedures being much more similar in overall risk at the end of the study period than they had been at the beginning (Fig. 2). The decrease in the perforation incidence from colonoscopy over time may be a result of improvements in technology and in the training of endoscopists. The lack of a similar decrease in perforation incidence from sigmoidoscopy may reflect billing for a colonoscopy as a sigmoidoscopy when the procedure is aborted because of a complication, or it may reflect a trend toward having less skilled endoscopists perform this less demanding procedure.
Although current consensus guidelines suggest that asymptomatic individuals who are at average risk for colorectal cancer should undergo a yearly FOBT and flexible sigmoidoscopy every 5 years or a colonoscopy every 10 years, these guidelines are being debated (13,38). Observational studies and randomized trials have demonstrated that FOBT and sigmoidoscopy reduce mortality after a diagnosis of colorectal cancer (14,68). However, many believe that mortality may be reduced more by colonoscopy than by sigmoidoscopy (16). Indeed, in this study, we observed a gradual increase over time in the number of colonoscopies performed, with a concomitant decline in the annual number of sigmoidoscopies, partially supporting this belief.
Our findings are population-based, from a large and relatively unselected series of colonoscopies and sigmoidoscopies, and permit a direct comparison of the two procedures for perforation incidence. These results should be useful to clinicians making screening and diagnostic decisions for individual patients and to public health and policy officials setting guidelines for colorectal cancer screening programs.
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NOTES |
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We acknowledge the efforts of the Applied Research Branch, Division of Cancer Prevention and Population Science, NCI; the Office of Information Services and the Office of Strategic Planning, Health Care Financing Administration; Information Management Services, Inc.; and the SEER Program tumor registries in the creation of the SEERMedicare database.
1 Editors note: SEER is a set of geographically defined, population-based, central cancer registries in the United States, operated by local nonprofit organizations under contract to the National Cancer Institute (NCI). Registry data are submitted electronically without personal identifiers to the NCI on a biannual basis, and the NCI makes the data available to the public for scientific research.
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Manuscript received July 9, 2002; revised November 18, 2002; accepted December 2, 2002.
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