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Perforation of the Colon and Rectum—A Newly Recognized Complication of CT Colonography
Perforation of the Colon and Rectum—A Newly Recognized Complication of CT Colonography Jacob Sosna, MD,*,† Tamar Sella, MD,* Jacob Bar-Ziv, MD,* and Eugene Libson, MD* CT colonography (CTC) and conventional colonoscopy may have similar efficacy for detection of polyps >6 mm. Perforation of the colon and rectum is a relatively rare, but potentially morbid complication of CTC, especially in symptomatic patients. Older age and underlying concomitant colon pathology increase the risk of perforation. This review describes the incidence, clinical features, and management of colon perforations at CTC, a study that was considered risk-free until recently. Semin Ultrasound CT MRI 27:161-165 © 2006 Elsevier Inc. All rights reserved.
C
T colonography (CTC) was first described in 19941 as a rapid, noninvasive imaging method to investigate the colon and rectum. Since the advent of CTC, it has been regarded as a potential alternative technique to conventional colonoscopy for the detection of colorectal polyps and cancers.2 Although recent studies have suggested that CTC and conventional colonoscopy have similar sensitivity for detection of polyps ⬎6 mm,3-5 some still question its performance.6 Procedural risks associated with emerging technology such as CTC need to be assessed, ideally before widespread implementation, to permit appropriate risk– benefit analysis. Such assessment should be comparable to earlier ones performed for conventional colonoscopy.7 A better understanding of the relative risk of perforation associated with CTC will facilitate an evidence-based choice for population screening recommendations. This review will describe the incidence, clinical features, and management of colon perforations at CTC, a study that was considered risk-free until recently.
Risk of Perforation at Conventional Colonoscopy and Barium Enema Conventional colonoscopy has been widely used since the 1970s as the primary diagnostic tool to follow-up on positive
*From the Department of Radiology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel; and †Department of Radiology, Beth Israel Deaconess Medical Center, Boston, MA. Address reprint requests to: Jacob Sosna, MD, Department of Radiology, Hadassah Hebrew University Medical Center, POB 12000, Jerusalem, Israel. E-mail: [email protected].
0887-2171/06/$-see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1053/j.sult.2006.01.005
findings from fecal occult blood tests, and on abnormalities found during sigmoidoscopy.8-10 In addition, colonoscopy has been recommended as the initial screening tool for individuals at average-to-high risk for colorectal cancer.8-10 Colon perforation is a well-known risk of conventional colonoscopy, with a reported rate of occurrence of approximately of 0.06 to 0.19%, or 1:400 to 1300 patients in large series.11-18 One in 1246 to 1333 patients requires surgical intervention. Even in skilled hands, colonoscopic perforation is not always avoidable and may occur unexpectedly. The rate of perforation for therapeutic colonoscopy is higher than for diagnostic colonoscopy.11-18 The mortality rate from conventional colonoscopy perforations has been reported from 0 to 0.03%.11-20 Barium enema, another total colon examination, has a colon perforation incidence of 0.004 to 0.04% (1:2500 to 1:25,000).21-24 During a barium enema, colonic perforation or rupture has been shown to occur even with lowpressure insufflation.25 The overall mortality rate from colon perforation has decreased in recent decades from approximately 50 to 35% as the result of advances in intensive and supportive care.26
Risk of Perforation at CTC In the last few years most research regarding CTC has been aimed at assessing its performance compared with conventional colonoscopy. The main limitations for CTC acceptance by patients have been colonic preparation and the need for insufflation. During the first 10 years after its introduction, CTC was considered a risk-free procedure, until two case reports of colon perforation at CTC were published.27,28 The first case reported described an 81-year-old female with ulcerative colitis.27 During CTC the patient experienced pain, and bright red blood was seen per rectum. Free intraperito161
162 neal air was noted on an upright chest radiograph. At surgery a large hematoma was detected on the antimesenteric wall of the cecum, and the patient underwent an emergent right hemicolectomy. The pathologic findings were described as ulcerative colitis with full-thickness perforation of the cecum. The second case report involved a 74-year-old male who underwent two unsuccessful conventional colonoscopies that terminated at a stricture 25 cm from the anal verge.28 Biopsy of the mucosa disclosed inflammatory changes. CTC, performed 2 weeks later, demonstrated a large tumor at the area of the stricture. The patient was asymptomatic; however, free air was noted on CTC images. At surgery a tear was seen distal to the tumor, at the level of the upper rectum. The postoperative course was uneventful. We have recently assessed the incidence of colorectal perforations at CTC in a large population-based multicenter cohort.29 A total of 11,870 CTC studies were included. Seven colorectal perforations, including the second case report mentioned above, were documented. In this series, the incidence of colon perforation was 0.058% or 1:1696 studies; surgical intervention was required in four patients, giving a rate of 1:2967 patients. Three perforations were treated with primary repair or resection and anastomosis, and one was treated with a two-stage procedure. No deaths were recorded. Only one of the seven patients underwent CTC for screening. Common features in this study were older age and male gender (77.8 years and 84%, respectively). Six perforations (84%) occurred in symptomatic patients at high risk for colorectal neoplasia and one (16%) occurred in an asymptomatic average-risk patient. All studies were performed after insufflation of room air. Six (84%) perforations occurred following insufflation with a rectal tube, including five with balloon inflation. Five (71%) perforations occurred in the sigmoid colon and two (29%) occurred in the rectum. Possible factors contributing to the risk of perforation found in this study included a left-sided inguinal hernia containing colon, severe diverticulosis, and an obstructing carcinoma (Fig. 1). Other reports on perforations were gathered from an international survey.30 Three perforations occurred in Australia. Two of these three patients recovered without intervention; the third underwent a right hemicolectomy. Cecal gangrene and perforation were found at surgery. Carbon dioxide insufflation was used in these patients. In a telephone survey of all UK radiology departments offering CTC in routine clinical practice, perforation was reported in 10 patients from six centers of 16,517 examinations, a rate of 1:1651 patients or 0.06%.31 Of these 10 perforations, one occurred prior to insufflation, presumably due to bowel catharsis in a frail patient. Seven of the remaining nine perforations occurred during examinations using an inflated balloon-tipped rectal catheter; in the remaining two patients, a standard rectal catheter was used. Colonic insufflation was achieved using carbon dioxide delivered via an automated insufflator in two patients, while seven underwent manual room air insufflation via a handheld bulb. Four patients were entirely asymptomatic. Only one patient had peri-
J. Sosna et al
Figure 1 Eighty-four-year-old man with perforation of the sigmoid at CT colonography. CTC was performed due to anemia and positive fecal occult blood. Large amount of free air is noted in the peritoneal space (white arrows) surrounding the colon (asterisks) (A). An inguinal hernia on the left containing the sigmoid (white arrow) (B) is the suspected cause of perforation with distention of the sigmoid up to the hernia with proximal collapse. Note the barium enema rectal tube used in this case (curved arrow) (B). At surgery perforation was noted at the level below the strangulated sigmoid at the neck of the hernia.
tonitis and required surgery. There were no associated deaths. The most recent case report of colonic perforation was of a patient without colonic pathology.32 Cumulative published cases with colonic perforation at CTC include a total of 22 patients, with 7 requiring surgery. An additional unpublished three to four cases are known from personal communication to the authors of this review. A comparison of the published reports suggests that the rate of colon perforation at conventional diagnostic colonos-
Perforation of the colon and rectum
Figure 2 Sixty-year-old man with perforation of the colon at the recto-sigmoid junction at CT colonography. Axial CT performed in the supine position demonstrates free peritoneal air (curved arrow) as well as retroperitoneal air (arrows). The patient was treated conservatively.
copy is higher than that for CTC. Thus, there is a potential increase in patient safety using CTC for evaluating the colon compared with conventional diagnostic colonoscopy. If this is verified in additional studies, patients and physicians considering screening for colorectal carcinoma will need to take this fact into account when deciding which screening method to use. The currently published rate of perforation at CTC is, however, higher than that for double-contrast barium enema. One possible explanation is the use of direct fluoroscopic observation at barium enema during catheter positioning and when air and contrast are inserted. At CTC no real-time monitoring for the existence of free air is feasible; if a perforation occurs, it can only be detected after full insufflation, based on patient’s symptoms, on scout films, or on CTC images.
Possible Mechanisms and Contributing Factors In general, five types of colorectal perforations have been described: perforations of the anal canal below the levator muscles, incomplete perforations, retroperitoneal perforations, transmural perforations into adjacent viscera, and perforations into the intraperitoneal cavity (Fig. 2).26 Most incomplete perforations and half of the retroperitoneal perforations have minimal clinical symptoms. Intraperitoneal perforations lead to the most serious complications. Typically rectal bleeding and mild abdominal complaints are the first symptoms, followed by progressive sepsis and peritonitis, potentially resulting in high mortality rates. For intramural or small retroperitoneal perforations, conventional treatment is often sufficient; however, intraperitoneal perfo-
163 rations with extravasation of bowel contents may necessitate immediate aggressive surgical treatment. In most published cases, the suspected mechanism of perforation at CTC was baro-trauma from overzealous air insufflation in colons that were jeopardized by conditions that did not allow free passage of air into more proximal colonic segments.33 This mechanism occurred in patients with severe diverticulosis, annular carcinoma, and left inguinal hernia containing the sigmoid colon. Diverticulosis and obstruction are known risk factors for perforation.20 Pressure in the distal colon, between the rectum and the proximal obstructing pathology, presumably achieved such an elevated level that perforation occurred. A minority of reported perforations occurred in the right and transverse colon. In these locations, preexisting colonic diseases, such as ulcerative colitis, which caused weakening of the bowel wall, are the most probable cause of perforation during insufflation, even at acceptable pressures. An inflated balloon-tipped rectal catheter was used for CTC in most patients with rectal perforation. The use of balloon-tipped catheters in CTC must be approached with caution. Insertion and insufflation of the balloon-tipped catheter should be performed by an experienced physician, especially as insertion at CTC is performed with no fluoroscopic guidance. Although only a minority of perforations occurred in the rectum, we have changed our practice and now use a softer and smaller caliber Foley catheter. However, the use of a larger caliber rectal tube is clearly not the only factor leading to perforation, as perforations also occurred with the use of a Foley catheter. Two patients in the published series underwent conventional colonoscopy immediately prior to CTC.28 Because no images were routinely obtained on CTC prior to air insufflation, the possibility that perforation occurred at conventional colonoscopy cannot be excluded. Therefore, we have changed our practice, and now, as a safety precaution, we perform CT scout films or a few axial images through the abdomen and pelvis before inserting the rectal catheter, if colonoscopy was performed within 24 hours prior to CTC. Of particular interest are perforations that occurred in patients with left inguinal hernias containing the sigmoid colon. One theoretical mechanism is incarceration of bowel loops secondary to the high pressure of the insufflated air. At surgery, perforation was indeed found below the level of strangulation at the hernia neck. Perforation of the large bowel within a hernia is extremely rare, regardless of whether it is associated with benign or malignant disease. Such perforations have been reported in association with sigmoid cancer and iatrogenic causes such as barium enema.25,34 As a precaution, we have changed our practice of CTC insufflation. The supervising physician now pays special attention to the inguinal region during insufflation. If a preexisting hernia seems to increase in size, air insufflation is immediately discontinued. An additional factor that may contribute to perforation at CTC is recent colonic biopsy. Increase in intraluminal pressure at the biopsy site could potentially result in perforation. Barium enema is generally considered safe after colonic bi-
J. Sosna et al
164 opsy24,35; however, it is not clear that the intraluminal pressure achieved at CTC is the same as that used on barium enema. Furthermore, as mentioned above, detecting a perforation during CTC is more difficult and occurs later than with barium enema. Therefore, we have changed our policy and do not perform CTC immediately after incomplete conventional colonoscopy if a biopsy was performed. To increase patient safety, we generally postpone the CTC for at least 2 weeks following biopsy. This issue has not been addressed in the literature, and further studies need be performed. Colonic distention is easily and reliably achieved with atmospheric air, although carbon dioxide is under evaluation as a potentially more comfortable alternative in both conventional colonoscopy and CTC.36-39 Carbon dioxide volume in commercially available pumps is initially limited to 4 liters, with a pressure limit of 25 mmHg. Atmospheric air is limited only by the number of puffs administered by the physician during the study.37 Although most perforations occurred with room air, at least five occurred in patients who were insufflated with carbon dioxide. Further studies are needed to assess the relative safety of air versus carbon dioxide for colon insufflation at CTC. We suspect that radiologist/nurse/technologist experience with insufflation may be related to perforation risk. Some perforations occurred when insufflation was performed by a person with minimal prior CTC experience. Less experienced members of the team may have been less cautious when inserting the rectal catheter, inflating the balloon, or distending the colon. We believe that radiologists and technologists should receive training not only on CTC interpretation, but also on the technical aspects of performing CTC. Such training should include instruction on appropriate insertion of a rectal tube, tips on insufflation, and assessment of the technical adequacy of the examination. Experience with barium enema procedures may not be sufficient for safe performance of CTC, due to lack of real-time monitoring during CTC. Ideally, radiologists or technologists interested in doing CTC examinations should perform supervised studies before introducing CTC into their practices. This may provide the critical knowledge needed to master CTC technique. Low CTC volume at a certain institution may also increase risk, as some perforations occurred in centers with relatively limited CTC experience. However other perforations occurred in very experienced centers. It is not clear whether personal experience at CTC is more important than institutional experience.
Implications for the Future Data on colon perforations at CTC may be used by opponents of this procedure and may hamper its acceptance as a possible screening technique. However, it is one of our primary responsibilities to present data that are relevant to procedurerelated risks and patient safety. We suggest that a central CTC complication registry be established. This will have implications for prospective analysis of screening CTC safety in future years. Future series may report lower CTC perforation rates and may define risk factors, as we and others learn from
our experience. At this relatively early stage, we cannot prospectively stratify the risk of perforation according to the indication for CTC or other presumed risk factors. Such factors cannot be reliably established based on the retrospective studies and case reports published to date. In conclusion, perforation of the colon and rectum is an uncommon but potentially significant complication of CTC, especially in symptomatic patients. Surgical treatment may be required. Older age, male gender, underlying colon pathology, and/or some degree of obstruction may increase the risk of perforation; however, further studies are necessary to better define patients at higher risk.
References 1. Vining DJ, Gelfand DW, Bechtold RE, et al: Technical feasibility of colon imaging with helical CT and virtual reality. Am J Roentgenol 1994;162:S104 2. Sosna J, Morrin MM, Copel L, et al: Computed tomography colonography (virtual colonoscopy): update on technique, applications and further developments. Surg Technol Int 2003;11:102-110 3. Sosna J, Morrin MM, Kruskal JB, et al: CT colonography of colorectal polyps: a metaanalysis. Am J Roentgenol 2003;181:1593-1598 4. Halligan S, Altman DG, Taylor SA, et al: CT colonography in the detection of colorectal polyps and cancer: systematic review, meta-analysis, and proposed minimum data set for study level reporting. Radiology 2005;237:893-904 5. Mulhall BP, Veerappan GR, Jackson JL: Meta-analysis: computed tomographic colonography. Ann Intern Med 2005;142:635-650 6. Cotton PB, Durkalski VL, Pineau BC, et al: Computed tomographic colonography (virtual colonoscopy): a multicenter comparison with standard colonoscopy for detection of colorectal neoplasia. JAMA 2004;14:291:1713-1719 7. Waye JD, Kahn O, Auerbach ME: Complications of colonoscopy and flexible sigmoidoscopy. Gastrointest Endosc Clin N Am 1996;6:343377 8. Winawer SJ, Fletcher RH, Miller L, et al: Colorectal cancer screening: clinical guidelines and rationale. Gastroenterology 1997;112:594-642 9. Markowitz AJ, Winawer SJ: Screening and surveillance for colorectal carcinoma. Hematol Oncol Clin North Am 1997;11:579-608 10. Helm J, Choi J, Sutphen R, et al: Current and evolving strategies for colorectal cancer screening. Cancer Control 2003;10:193-204 11. Nivatvongs S: Complications in colonoscopic polypectomy: lessons to learn from an experience with 1576 polyps. Am Surg 1988;54:61-63 12. Reiertsen O, Skjoto J, Jacobsen CD, et al: Complications of fiberoptic gastrointestinal endoscopy—five years’ experience in a central hospital. Endoscopy 1987;19:1-6 13. Jentschura D, Raute M, Winter J, et al: Complications in endoscopy of the lower gastrointestinal tract. Therapy and prognosis. Surg Endosc 1994;8:672-676 14. Sieg A, Hachmoeller-Eisenbach U, Eisenbach T: Prospective evaluation of complications in outpatient GI endoscopy: a survey among German gastroenterologists. Gastrointest Endosc 2001;53:620-627 15. Anderson ML, Pasha TM, Leighton JA: Endoscopic perforation of the colon: lessons from a 10-year study. Am J Gastroenterol 2000;95:34183422 16. Eckardt VF, Kanzler G, Schmitt T, et al: Complications and adverse effects of colonoscopy with selective sedation. Gastrointest Endosc 1999;49:560-565 17. Waye JD, Lewis BS, Yessayan S: Colonoscopy: a prospective report of complications. J Clin Gastroenterol 1992;15:347-351 18. Tran DQ, Rosen L, Kim R, et al: Actual colonoscopy: what are the risks of perforation? Am Surg 2001;67:845-847 19. Dafnis G, Ekbom A, Pahlman L, et al: Complications of diagnostic and therapeutic colonoscopy within a defined population in Sweden. Gastrointest Endosc 2001;54:302-309 20. Gatto NM, Frucht H, Sundararajan V, et al: Risk of perforation after
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colonoscopy and sigmoidoscopy: a population-based study. J Natl Cancer Inst 2003;95:230-236 Vora P, Chapman A: Complications from radiographer-performed double contrast barium enemas. Clin Radiol 2004;l59:364-368 de Zwart IM, Griffioen G, Shaw MP, et al: Barium enema and endoscopy for the detection of colorectal neoplasia: sensitivity, specificity, complications and its determinants. Clin Radiol 2001;56:401-409 Blakeborough A, Sheridan MB, Chapman AH: Complications of barium enema examinations: a survey of UK Consultant Radiologists 1992 to 1994. Clin Radiol 1997;52:142-148 Williams SM, Harned RK: Recognition and prevention of barium enema complications. Curr Probl Diagn Radiol 1991;20:123-151 Fry RD, Shemesh EL, Kodner IJ, et al: Perforation of the rectum and sigmoid colon during barium-enema examination: management and prevention. Dis Colon Rectum 1989;32:759-764 de Feiter PW, Soeters PB, Dejong CH: Rectal perforations after barium enema: a review. Dis Colon Rectum Nov 23 (Epub), 2005 Coady-Fariborzian L, Angel LP, Procaccino JA: Perforated colon secondary to virtual colonoscopy: report of a case. Dis Colon Rectum 2004;47:1247-1249 Kamar M, Portnoy O, Bar-Dayan A, et al: Actual colonic perforation in virtual colonoscopy: report of a case. Dis Colon Rectum 2004;47:12421244 Sosna J, Blachar A, Amitai M, et al: Assessment of the risk of colonic perforation at CT colonography in a multi-center large cohort. Radiology 2006 (in press) Sosna J, Blachar A, Amitai M, et al: Assessment of the risk of perforation at CT colonography. Eur Radiol 2005;15:16 (abstr) (suppl 3) Burling D, Halligan S, Slater A, et al: Potentially serious adverse events
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associated with CT colonography performed in symptomatic patients: A national survey of the UK. Presented at the 91st Annual Meeting of the Radiological Society of North America, Chicago, IL (oral presentation), 2005 Young BM, Fletcher JG, Earnest F, et al: Colonic perforation at CT colonography in a patient without known colonic disease. Am J Roentgenol 2006;186:119-121 Damore LJ 2nd, Rantis PC, Vernava AM 3rd, et al: Colonoscopic perforations. Etiology, diagnosis, and management. Dis Colon Rectum 1996;39:1308-1314 Kouraklis G, Kouskos E, Glinavou A, et al: Perforated carcinoma of the sigmoid colon in an incarcerated inguinal hernia: report of a case. Surg Today 2003;33:707-708 Culp CE, Carlson HC: Is there a safe interval between diagnostic invasive procedure and the barium enema study of the colorectum? Gastrointest Radiol 1984;9:69-72 Yee J: CT colonography: examination prerequisites. Abdom Imaging 2002;27:244-252 Bretthauer M, Hoff GS, Thiis-Evensen E, et al: Air and carbon dioxide volumes insufflated during colonoscopy. Gastrointest Endosc 2003;58: 203-206 Sumanac K, Zealley I, Fox BM, et al: Minimizing postcolonoscopy abdominal pain by using CO2 insufflation: a prospective, randomized, double blind, controlled trial evaluating a new commercially available CO2 delivery system. Gastrointest Endosc 2002;56:190-194 Burling D, Taylor SA, Halligan S, et al: Automated insufflation of carbon dioxide for MDCT colonography: distension and patient experience compared with manual insufflation. Am J Roentgenol 2006;186:96103
C
T colonography (CTC) was first described in 19941 as a rapid, noninvasive imaging method to investigate the colon and rectum. Since the advent of CTC, it has been regarded as a potential alternative technique to conventional colonoscopy for the detection of colorectal polyps and cancers.2 Although recent studies have suggested that CTC and conventional colonoscopy have similar sensitivity for detection of polyps ⬎6 mm,3-5 some still question its performance.6 Procedural risks associated with emerging technology such as CTC need to be assessed, ideally before widespread implementation, to permit appropriate risk– benefit analysis. Such assessment should be comparable to earlier ones performed for conventional colonoscopy.7 A better understanding of the relative risk of perforation associated with CTC will facilitate an evidence-based choice for population screening recommendations. This review will describe the incidence, clinical features, and management of colon perforations at CTC, a study that was considered risk-free until recently.
Risk of Perforation at Conventional Colonoscopy and Barium Enema Conventional colonoscopy has been widely used since the 1970s as the primary diagnostic tool to follow-up on positive
*From the Department of Radiology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel; and †Department of Radiology, Beth Israel Deaconess Medical Center, Boston, MA. Address reprint requests to: Jacob Sosna, MD, Department of Radiology, Hadassah Hebrew University Medical Center, POB 12000, Jerusalem, Israel. E-mail: [email protected].
0887-2171/06/$-see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1053/j.sult.2006.01.005
findings from fecal occult blood tests, and on abnormalities found during sigmoidoscopy.8-10 In addition, colonoscopy has been recommended as the initial screening tool for individuals at average-to-high risk for colorectal cancer.8-10 Colon perforation is a well-known risk of conventional colonoscopy, with a reported rate of occurrence of approximately of 0.06 to 0.19%, or 1:400 to 1300 patients in large series.11-18 One in 1246 to 1333 patients requires surgical intervention. Even in skilled hands, colonoscopic perforation is not always avoidable and may occur unexpectedly. The rate of perforation for therapeutic colonoscopy is higher than for diagnostic colonoscopy.11-18 The mortality rate from conventional colonoscopy perforations has been reported from 0 to 0.03%.11-20 Barium enema, another total colon examination, has a colon perforation incidence of 0.004 to 0.04% (1:2500 to 1:25,000).21-24 During a barium enema, colonic perforation or rupture has been shown to occur even with lowpressure insufflation.25 The overall mortality rate from colon perforation has decreased in recent decades from approximately 50 to 35% as the result of advances in intensive and supportive care.26
Risk of Perforation at CTC In the last few years most research regarding CTC has been aimed at assessing its performance compared with conventional colonoscopy. The main limitations for CTC acceptance by patients have been colonic preparation and the need for insufflation. During the first 10 years after its introduction, CTC was considered a risk-free procedure, until two case reports of colon perforation at CTC were published.27,28 The first case reported described an 81-year-old female with ulcerative colitis.27 During CTC the patient experienced pain, and bright red blood was seen per rectum. Free intraperito161
162 neal air was noted on an upright chest radiograph. At surgery a large hematoma was detected on the antimesenteric wall of the cecum, and the patient underwent an emergent right hemicolectomy. The pathologic findings were described as ulcerative colitis with full-thickness perforation of the cecum. The second case report involved a 74-year-old male who underwent two unsuccessful conventional colonoscopies that terminated at a stricture 25 cm from the anal verge.28 Biopsy of the mucosa disclosed inflammatory changes. CTC, performed 2 weeks later, demonstrated a large tumor at the area of the stricture. The patient was asymptomatic; however, free air was noted on CTC images. At surgery a tear was seen distal to the tumor, at the level of the upper rectum. The postoperative course was uneventful. We have recently assessed the incidence of colorectal perforations at CTC in a large population-based multicenter cohort.29 A total of 11,870 CTC studies were included. Seven colorectal perforations, including the second case report mentioned above, were documented. In this series, the incidence of colon perforation was 0.058% or 1:1696 studies; surgical intervention was required in four patients, giving a rate of 1:2967 patients. Three perforations were treated with primary repair or resection and anastomosis, and one was treated with a two-stage procedure. No deaths were recorded. Only one of the seven patients underwent CTC for screening. Common features in this study were older age and male gender (77.8 years and 84%, respectively). Six perforations (84%) occurred in symptomatic patients at high risk for colorectal neoplasia and one (16%) occurred in an asymptomatic average-risk patient. All studies were performed after insufflation of room air. Six (84%) perforations occurred following insufflation with a rectal tube, including five with balloon inflation. Five (71%) perforations occurred in the sigmoid colon and two (29%) occurred in the rectum. Possible factors contributing to the risk of perforation found in this study included a left-sided inguinal hernia containing colon, severe diverticulosis, and an obstructing carcinoma (Fig. 1). Other reports on perforations were gathered from an international survey.30 Three perforations occurred in Australia. Two of these three patients recovered without intervention; the third underwent a right hemicolectomy. Cecal gangrene and perforation were found at surgery. Carbon dioxide insufflation was used in these patients. In a telephone survey of all UK radiology departments offering CTC in routine clinical practice, perforation was reported in 10 patients from six centers of 16,517 examinations, a rate of 1:1651 patients or 0.06%.31 Of these 10 perforations, one occurred prior to insufflation, presumably due to bowel catharsis in a frail patient. Seven of the remaining nine perforations occurred during examinations using an inflated balloon-tipped rectal catheter; in the remaining two patients, a standard rectal catheter was used. Colonic insufflation was achieved using carbon dioxide delivered via an automated insufflator in two patients, while seven underwent manual room air insufflation via a handheld bulb. Four patients were entirely asymptomatic. Only one patient had peri-
J. Sosna et al
Figure 1 Eighty-four-year-old man with perforation of the sigmoid at CT colonography. CTC was performed due to anemia and positive fecal occult blood. Large amount of free air is noted in the peritoneal space (white arrows) surrounding the colon (asterisks) (A). An inguinal hernia on the left containing the sigmoid (white arrow) (B) is the suspected cause of perforation with distention of the sigmoid up to the hernia with proximal collapse. Note the barium enema rectal tube used in this case (curved arrow) (B). At surgery perforation was noted at the level below the strangulated sigmoid at the neck of the hernia.
tonitis and required surgery. There were no associated deaths. The most recent case report of colonic perforation was of a patient without colonic pathology.32 Cumulative published cases with colonic perforation at CTC include a total of 22 patients, with 7 requiring surgery. An additional unpublished three to four cases are known from personal communication to the authors of this review. A comparison of the published reports suggests that the rate of colon perforation at conventional diagnostic colonos-
Perforation of the colon and rectum
Figure 2 Sixty-year-old man with perforation of the colon at the recto-sigmoid junction at CT colonography. Axial CT performed in the supine position demonstrates free peritoneal air (curved arrow) as well as retroperitoneal air (arrows). The patient was treated conservatively.
copy is higher than that for CTC. Thus, there is a potential increase in patient safety using CTC for evaluating the colon compared with conventional diagnostic colonoscopy. If this is verified in additional studies, patients and physicians considering screening for colorectal carcinoma will need to take this fact into account when deciding which screening method to use. The currently published rate of perforation at CTC is, however, higher than that for double-contrast barium enema. One possible explanation is the use of direct fluoroscopic observation at barium enema during catheter positioning and when air and contrast are inserted. At CTC no real-time monitoring for the existence of free air is feasible; if a perforation occurs, it can only be detected after full insufflation, based on patient’s symptoms, on scout films, or on CTC images.
Possible Mechanisms and Contributing Factors In general, five types of colorectal perforations have been described: perforations of the anal canal below the levator muscles, incomplete perforations, retroperitoneal perforations, transmural perforations into adjacent viscera, and perforations into the intraperitoneal cavity (Fig. 2).26 Most incomplete perforations and half of the retroperitoneal perforations have minimal clinical symptoms. Intraperitoneal perforations lead to the most serious complications. Typically rectal bleeding and mild abdominal complaints are the first symptoms, followed by progressive sepsis and peritonitis, potentially resulting in high mortality rates. For intramural or small retroperitoneal perforations, conventional treatment is often sufficient; however, intraperitoneal perfo-
163 rations with extravasation of bowel contents may necessitate immediate aggressive surgical treatment. In most published cases, the suspected mechanism of perforation at CTC was baro-trauma from overzealous air insufflation in colons that were jeopardized by conditions that did not allow free passage of air into more proximal colonic segments.33 This mechanism occurred in patients with severe diverticulosis, annular carcinoma, and left inguinal hernia containing the sigmoid colon. Diverticulosis and obstruction are known risk factors for perforation.20 Pressure in the distal colon, between the rectum and the proximal obstructing pathology, presumably achieved such an elevated level that perforation occurred. A minority of reported perforations occurred in the right and transverse colon. In these locations, preexisting colonic diseases, such as ulcerative colitis, which caused weakening of the bowel wall, are the most probable cause of perforation during insufflation, even at acceptable pressures. An inflated balloon-tipped rectal catheter was used for CTC in most patients with rectal perforation. The use of balloon-tipped catheters in CTC must be approached with caution. Insertion and insufflation of the balloon-tipped catheter should be performed by an experienced physician, especially as insertion at CTC is performed with no fluoroscopic guidance. Although only a minority of perforations occurred in the rectum, we have changed our practice and now use a softer and smaller caliber Foley catheter. However, the use of a larger caliber rectal tube is clearly not the only factor leading to perforation, as perforations also occurred with the use of a Foley catheter. Two patients in the published series underwent conventional colonoscopy immediately prior to CTC.28 Because no images were routinely obtained on CTC prior to air insufflation, the possibility that perforation occurred at conventional colonoscopy cannot be excluded. Therefore, we have changed our practice, and now, as a safety precaution, we perform CT scout films or a few axial images through the abdomen and pelvis before inserting the rectal catheter, if colonoscopy was performed within 24 hours prior to CTC. Of particular interest are perforations that occurred in patients with left inguinal hernias containing the sigmoid colon. One theoretical mechanism is incarceration of bowel loops secondary to the high pressure of the insufflated air. At surgery, perforation was indeed found below the level of strangulation at the hernia neck. Perforation of the large bowel within a hernia is extremely rare, regardless of whether it is associated with benign or malignant disease. Such perforations have been reported in association with sigmoid cancer and iatrogenic causes such as barium enema.25,34 As a precaution, we have changed our practice of CTC insufflation. The supervising physician now pays special attention to the inguinal region during insufflation. If a preexisting hernia seems to increase in size, air insufflation is immediately discontinued. An additional factor that may contribute to perforation at CTC is recent colonic biopsy. Increase in intraluminal pressure at the biopsy site could potentially result in perforation. Barium enema is generally considered safe after colonic bi-
J. Sosna et al
164 opsy24,35; however, it is not clear that the intraluminal pressure achieved at CTC is the same as that used on barium enema. Furthermore, as mentioned above, detecting a perforation during CTC is more difficult and occurs later than with barium enema. Therefore, we have changed our policy and do not perform CTC immediately after incomplete conventional colonoscopy if a biopsy was performed. To increase patient safety, we generally postpone the CTC for at least 2 weeks following biopsy. This issue has not been addressed in the literature, and further studies need be performed. Colonic distention is easily and reliably achieved with atmospheric air, although carbon dioxide is under evaluation as a potentially more comfortable alternative in both conventional colonoscopy and CTC.36-39 Carbon dioxide volume in commercially available pumps is initially limited to 4 liters, with a pressure limit of 25 mmHg. Atmospheric air is limited only by the number of puffs administered by the physician during the study.37 Although most perforations occurred with room air, at least five occurred in patients who were insufflated with carbon dioxide. Further studies are needed to assess the relative safety of air versus carbon dioxide for colon insufflation at CTC. We suspect that radiologist/nurse/technologist experience with insufflation may be related to perforation risk. Some perforations occurred when insufflation was performed by a person with minimal prior CTC experience. Less experienced members of the team may have been less cautious when inserting the rectal catheter, inflating the balloon, or distending the colon. We believe that radiologists and technologists should receive training not only on CTC interpretation, but also on the technical aspects of performing CTC. Such training should include instruction on appropriate insertion of a rectal tube, tips on insufflation, and assessment of the technical adequacy of the examination. Experience with barium enema procedures may not be sufficient for safe performance of CTC, due to lack of real-time monitoring during CTC. Ideally, radiologists or technologists interested in doing CTC examinations should perform supervised studies before introducing CTC into their practices. This may provide the critical knowledge needed to master CTC technique. Low CTC volume at a certain institution may also increase risk, as some perforations occurred in centers with relatively limited CTC experience. However other perforations occurred in very experienced centers. It is not clear whether personal experience at CTC is more important than institutional experience.
Implications for the Future Data on colon perforations at CTC may be used by opponents of this procedure and may hamper its acceptance as a possible screening technique. However, it is one of our primary responsibilities to present data that are relevant to procedurerelated risks and patient safety. We suggest that a central CTC complication registry be established. This will have implications for prospective analysis of screening CTC safety in future years. Future series may report lower CTC perforation rates and may define risk factors, as we and others learn from
our experience. At this relatively early stage, we cannot prospectively stratify the risk of perforation according to the indication for CTC or other presumed risk factors. Such factors cannot be reliably established based on the retrospective studies and case reports published to date. In conclusion, perforation of the colon and rectum is an uncommon but potentially significant complication of CTC, especially in symptomatic patients. Surgical treatment may be required. Older age, male gender, underlying colon pathology, and/or some degree of obstruction may increase the risk of perforation; however, further studies are necessary to better define patients at higher risk.
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