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DOI:10.2214/AJR.05.1179
AJR 2006; 187:1179-1183
© American Roentgen Ray Society


Original Research

Accuracy of MDCT in Predicting Site of Gastrointestinal Tract Perforation

Bernard Hainaux1,2, Emmanuel Agneessens2, Raphael Bertinotti1, Viviane De Maertelaer3, Erika Rubesova1, Elie Capelluto4 and Constantin Moschopoulos1

1 Department of Radiology, Centre Hospitalier Universitaire St.-Pierre, Université Libre de Bruxelles, 322 Rue Haute, Brussels 1000, Belgium.
2 Department of Radiology, HIS Site Etterbeek-Ixelles, Brussels, Belgium.
3 Statistical Unit, Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, Université Libre de Bruxelles, Brussels, Belgium.
4 Department of Gastrointestinal Surgery, Centre Hospitalier Universitaire St.-Pierre, Université Libre de Bruxelles, Brussels, Belgium.

Received July 8, 2005; accepted after revision September 18, 2005.

 
Address correspondence to B. Hainaux (hainauxb{at}yahoo.fr).


Abstract
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Abstract
Introduction
Subjects and Methods
Results
Discussion
References
 
OBJECTIVE. The purpose of this study was to prospectively evaluate the accuracy of MDCT for preoperative determination of the site of surgically proven gastrointestinal tract perforations and to determine the most predictive findings in this diagnosis.

SUBJECTS AND METHODS. We prospectively studied 85 consecutive patients with extraluminal air on MDCT who had surgically proven gastrointestinal tract perforations. All patients underwent surgery within 12 hours after MDCT was performed. Two experienced radiologists, blinded to the surgical diagnosis, reached a consensus prediction of the site of the perforation using the following eight MDCT findings: concentration of extraluminal air bubbles adjacent to the bowel wall, free air in supramesocolic or inframesocolic compartments, extraluminal air in both abdomen and pelvis, focal defect in the bowel wall, segmental bowel-wall thickening, perivisceral fat stranding, abscess, and extraluminal fluid. MDCT imaging results were compared with surgical and pathologic findings. Logistic regression analyses were performed to assess the significance of the different radiologic criteria.

RESULTS. Analysis of MDCT images was predictive of the site of gastrointestinal tract perforation in 73 (86%) of 85 patients. Logistic regression showed that concentration of extraluminal air bubbles (p < 0.001), segmental bowel wall thickening (p < 0.001), and focal defect of the bowel wall (p = 0.007) were strong predictors of the site of bowel perforation.

CONCLUSION. MDCT is highly accurate for predicting the site of gastrointestinal tract perforations. Three of eight CT findings significantly correlate with surgical diagnosis.

Keywords: abdominal imaging • bowel • CT • gastrointestinal radiology • gastrointestinal tract perforation • MDCT


Introduction
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
 
Free intraperitoneal air in association with acute abdominal pain is a major finding in the diagnosis of gastrointestinal tract perforation, usually leading to surgical treatment [1]. A laparoscopic procedure is currently performed instead of open surgery, even for acute conditions such as gastroduodenal perforated ulcer and acute perforated appendicitis. As a consequence, it is beneficial for surgeons to know in advance where the bowel tract is perforated. During the past few years, numerous investigations have established CT as the imaging technique of choice for diagnosing pneumoperitoneum [2, 3]. However, few authors have studied the accuracy of CT to localize the site of the gastrointestinal tract perforation, and no large prospective series focusing on this point has been reported. Because an accurate preoperative diagnosis is helpful for surgeons, we undertook this prospective study to evaluate the accuracy of MDCT in the identification of the site of bowel perforation and to objectively assess the CT findings that accurately lead to diagnosis.


Subjects and Methods
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Abstract
Introduction
Subjects and Methods
Results
Discussion
References
 
Patients
Between January 2003 and June 2004, we prospectively studied 85 consecutive patients presenting with acute abdominal pain and pneumoperitoneum on CT. All patients had surgically proven gastrointestinal tract perforation. The study included 43 men and 42 women with an age range of 16 to 94 years (mean age, 56 years). Patients younger than 16 years were not included. Surgery was performed on all patients within 12 hours after detection of extraluminal air and provided the exact location of the perforation site. Institutional review board approval was obtained for this study.

CT Examinations
Abdominal examinations were performed on a 4-MDCT scanner (Somatom Plus Volume Zoom, Siemens Medical Solutions) with the following parameters: collimation, 4 x 2.5 mm; table speed, 15 mm per 0.5 second of scanner rotation; 120 kV; and 130 effective milliampere seconds. All the patients underwent scanning in the supine position starting from the diaphragm down to the pubic symphysis. None of the patients received oral or rectal contrast material; unenhanced scanning was performed in all patients. In 46 patients, additional contrast-enhanced images were acquired with the same parameters after injection of 120 mL of a low-osmolarity contrast medium (iobitridol, Xenetix 350 mg I/mL, Guerbet) at a rate of 2.5 mL/s via a power injector. Scanning was started 80 seconds after initiating contrast material injection.

Image Analysis
The images were stored on compact disks and reviewed on a workstation (Wizard, Siemens Medical Solutions). Two experienced abdominal radiologists evaluated axial and multiplanar reconstruction images. They were blinded to all records but were informed that all patients presented with acute abdominal pain and their abdominal CT scans showed pneumoperitoneum. Together, the radiologists completed a questionnaire on the presence or absence of eight CT findings indicative of acute bowel disease and gastrointestinal perforation. The eight CT findings evaluated were few bubbles of extraluminal air concentrated in close proximity to the bowel wall, extraluminal air exclusively in supramesocolic or inframesocolic compartments, extraluminal air in both abdomen and pelvis, focal defect in the bowel wall, segmental bowel-wall thickening, perivisceral inflammatory fat stranding, abscess, and extraluminal fluid. Bowel-wall thickening was a subjective criterion evaluated without measurement of the bowel wall. After reviewing these eight findings, the two radiologists were asked to determine by consensus the site of bowel perforation. The predicted sites of perforation were categorized as follows: stomach and duodenum, jejunum and ileum, appendix, cecum and ascending colon, transverse colon, descending colon, sigmoid colon, and rectum.

Statistical Analysis
For each of the eight CT findings, the percentage of patients with positive results for the finding among the correct diagnoses and the percentage of patients with negative results for the finding among the 12 patients where the perforation site could not be determined—no diagnosis was false—were calculated. The percentage of correct diagnoses when each finding was present and the percentage of correct diagnoses when each finding was absent were also calculated. Logistic regression analyses were performed to evaluate the probability of a correct diagnosis as a function of the presence or absence of any of the eight findings. A first analysis was performed using the enter procedure. Rao's efficient scores [4] for each of the eight findings were calculated to detect which findings were statistically associated with a correct diagnosis. A second analysis was performed with a stepwise forward procedure to detect the successive most relevant findings for correctly predicting the localization of the perforation. Statistical analyses were performed using SPSS version 13.0 (Statistical Package for the Social Sciences) for Windows (Microsoft).

The link between the location of free intraabdominal air and the site of the perforation was assessed with a chi-square test. Exact p values were reported. Statistical analysis software (StatXact version 5.0, Cytel Software) was used.


Results
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Abstract
Introduction
Subjects and Methods
Results
Discussion
References
 
The perforation sites identified by surgery were the following: 37 stomach or duodenum perforations (34 gastroduodenal peptic ulcers, one perforated gastric carcinoma, two anastomotic dehiscences after gastric bypass procedures for morbid obesity), nine perforations of the small intestine (six ischemia, two perforating tumors, one blunt abdominal trauma), six acute perforated appendicitis cases, seven cecum or ascending colon perforations (three ischemia, one cecal volvulus, one diverticulitis, one iatrogenic complication after polypectomy, one idiopathic perforation), two transverse colon perforations (one polypectomy, one postoperative leak), six descending colon perforations (five postoperative leaks, one blunt abdominal trauma), 12 sigmoid colon perforations (10 diverticulitis, one ischemia, one sigmoid volvulus), and six rectum perforations (one carcinoma, one perforation after polypectomy, two perforations after improper cleansing enema, two postoperative leaks).

The prediction of the site of gastrointestinal tract perforation using the eight CT findings was correct in 73 (86%) of 85 patients. The diagnostic values for each CT finding are listed in Table 1. Rao's scores for each finding (Table 2) showed that three findings—concentration of extraluminal air bubbles (Figs. 1A and 1B), focal defect of the bowel wall (Figs. 2A and 2B), and segmental bowel-wall thickening (Fig. 3)—were statistically significant predictors of correct localization of the perforation. The logistical analysis regression with the stepwise procedure also showed that the best predictors for perforation localization were the presence of concentrated extraluminal air bubbles (p < 0.001) followed by the presence of segmental bowel-wall thickening (p = 0.046). The three most predictive findings of the site of perforation were not present in any of the 12 patients for whom the site was undetermined by the radiologists. We also detected a link (p < 0.001) between the location of free intraabdominal air and the site of perforation, which is summarized in Table 3. The 37 patients with upper gastroduodenal perforation all had free intraabdominal air around the liver or stomach. Eight of these patients also had free air in the pelvis. None of them presented with pelvic pneumoperitoneum alone. In contrast, all of the 39 patients with colon perforation had free air in the pelvis. For 15 of these patients, free air was only observed in the pelvis, and no patient had free air only in the supramesocolic compartment. Of the nine patients with small-bowel perforation, six had free air in both the abdomen and pelvis.


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TABLE 1: Diagnostic Values of Eight CT Findings in Predicting Site of Gastrointestinal Perforation

 

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TABLE 2: Rao's Scores for Eight CT Findings

 

Figure 1
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Fig. 1A 69-year-old man presenting with acute abdominal pain few hours after sigmoid polypectomy. Abdominal CT scan obtained at level of liver shows free intraperitoneal air.

 

Figure 2
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Fig. 1B 69-year-old man presenting with acute abdominal pain few hours after sigmoid polypectomy. Image at level of sigmoid shows concentration of extraluminal air bubbles in close proximity to sigmoid wall (arrows).

 

Figure 3
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Fig. 2A 51-year-old woman with perforated gastric ulcer. Transverse CT image shows pneumoperitoneum (asterisks) and focal defect in anterior gastric wall (arrow).

 

Figure 4
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Fig. 2B 51-year-old woman with perforated gastric ulcer. Sagittal reformatted image shows focal defect in anterior wall of gastric fundus (arrow) and pneumoperitoneum (asterisk).

 

Figure 5
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Fig. 3 42-year-old man with perforated sigmoid colon diverticulitis. Transverse CT image shows segmental bowel-wall thickening (arrowheads), mild pericolic fat stranding (asterisk), and few extraluminal bubbles of air adjacent to the bowel wall (arrow).

 

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TABLE 3: Location of Free Air in 85 Patients with Gastrointestinal Tract Perforation

 


Discussion
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Abstract
Introduction
Subjects and Methods
Results
Discussion
References
 
Several authors have shown that CT is the most valuable imaging technique for detecting free intraperitoneal air [2, 3]. However, few authors have investigated the sensitivity of CT in determining the site of gastrointestinal tract perforation. To our knowledge, only retrospective studies have been reported. Previous reports have emphasized the limits of CT for determining the site of perforation. In a retrospective series of 14 patients with perforated peptic ulcers reported by Chen et al. [5], the sensitivity of CT for showing free air was 100%, but the site of perforation could only be determined by CT in five patients (36%). In the series reported by Fultz et al. [6] of 11 patients with perforated peptic ulcers who all received oral contrast material, the site of perforation could be detected only in the three patients who showed extravasation of ingested contrast material. The small number of patients with leakage of oral contrast material was thought to be caused by the rapid sealing of a large percentage of perforated ulcers. In addition, the supine position used for CT provides less chance for contrast material to extravasate with an anterior perforation. As a result, we believe that CT may be better than gastrointestinal opacification for the diagnosis of gastrointestinal tract perforation and the determination of the site of perforation. Moreover, the recent introduction of MDCT has allowed high-speed acquisition, thin-slice collimation, and reformatting of images in any plane with high spatial resolution, making this technique particularly suitable for the assessment of abdominal abnormalities [7].

In our study, multiplanar reconstruction images were routinely performed, which we found to be useful for determining the precise location of bubbles of extraluminal air and defects in the bowel wall. Several articles stress the value of intraluminal gastrointestinal contrast material in the evaluation of patients with blunt abdominal trauma. The detection of free extraluminal contrast material is considered a direct sign of bowel perforation. However, in a literature review, the reported sensitivity of extravasation of oral contrast material varies from 19-42% [8]. The study of Shanmuganathan et al. [9] shows that triple-contrast helical CT (CT with administration of rectal, oral, and IV contrast material) is highly accurate for evaluating patients with penetrating injuries into the thoracoabdominal region. Nevertheless, only 15% of patients with bowel injury showed oral or rectal contrast material extravasation. Our study concerns mainly patients with nontraumatic bowel perforations who present with peritonitis. In these patients, it is often difficult to obtain oral or rectal opacification. One of the aims of our study was to determine the accuracy of CT to diagnose the site of bowel perforation using CT findings other than extravasation of contrast material.

The overall accuracy in predicting the site of bowel perforation was 86% in our study. These results are similar to the three previously published retrospective series [10-12]. Maniatis et al. [10] reported a sensitivity of 85.5% in a series of 76 patients presenting with bowel perforation secondary to various causes. Kim et al. [11] reported an overall accuracy of 82% in a series of 57 patients with gastrointestinal tract perforation after blunt abdominal trauma. The same result, 82%, was also reported by Catalano [12] in a series of 38 patients.

Previous reports have emphasized CT manifestations of bowel perforation secondary to various causes. However, no previous reports have compared CT findings to statistically evaluate the most useful findings. Ongolo-Zogo et al. [13] reported on a series of 10 perforated gastroduodenal peptic ulcers in which two important CT findings were indicative of the site of perforation: discontinuity in the bowel wall in six patients and tiny extraluminal air bubbles in close proximity to the bowel wall in two patients. Miki et al. [14] also reported on the direct visualization of a ruptured colonic wall in four of six patients with colonic perforation. However, these two findings did not occur in the series of 42 proximal and distal gastrointestinal tract perforations reported by Yeung et al. [15]. In our series of 85 perforations, free air bubbles in close proximity to the bowel wall indicated the site of perforation in 65 patients, with segmental bowel-wall thickening observed in 42 patients. Those two findings were strong predictors of the site of perforation (p <0.001). The third predictor of the site of perforation was the direct visualization of a focal defect in the bowel wall, seen in 29 patients (p =0.007). Moreover, in the 12 patients where CT was unable to predict the site of the perforation, none of these three findings was present.

As has been previously reported in other studies, our series also shows a link between the location of free intraabdominal air and the site of perforation [10, 16]. Gastroduodenal and colonic perforation can both appear as massive pneumoperitoneum with free air in the abdomen and in the pelvis. However, if free air is present only around the liver and stomach and not in the pelvis, proximal gastrointestinal perforation is likely. Conversely, if free air is present only in the pelvis, the likely site of perforation is the colon or, less frequently, the small bowel.

In conclusion, MDCT allows physicians not only to detect free intraabdominal air but also to precisely determine the anatomic site of gastrointestinal tract perforation without the use of oral or rectal contrast material. Three CT findings—concentrated bubbles of extraluminal air in close proximity to the bowel wall, focal defect in the bowel wall, and segmental bowel-wall thickening—have a high predictive value for the site of perforation.


Acknowledgments
 
We thank Anne Hepburn for reviewing the manuscript and Catherine Gerard and Johan Grymonprez for editorial assistance.


References
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
 

  1. Jeffrey RB, Federle MP, Wall S. Value of computed tomography in detecting occult gastrointestinal perforation. J Comput Assist Tomogr 1983; 7:825 -827[Medline]
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  4. Rao CR. Linear statistical inference and its applications, 2nd ed. New York, NY: Wiley,1973
  5. Chen CH, Huang HS, Yang CC, Yeh YH. Features of perforated peptic ulcers in conventional computed tomography. Hepatogastroenterology 2001;48 : 1393-1396[Medline]
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  8. Becker CD, Mentha G, Schmidlin F, Terrier F. Blunt abdominal trauma in adults: role of CT in the diagnosis and management of visceral injuries. Eur Radiol 1998;8 : 772-780[CrossRef][Medline]
  9. Shanmuganathan K, Mirvis SE, Chiu WC, Killeen KL, Scalea TM. Triple contrast helical CT in penetrating torso trauma: a prospective study to determine peritoneal violation and the need for laparotomy. AJR 2001; 177:1247 -1256[Abstract/Free Full Text]
  10. Maniatis V, Chryssikopoulos H, Roussakis A, et al. Perforation of the alimentary tract: evaluation with computed tomography. Abdom Imaging 2000; 25:373 -379[CrossRef][Medline]
  11. Kim HC, Shin HC, Park SJ, et al. Traumatic bowel perforation: analysis of CT findings according to the site and the elapsed time since accident. Clin Imaging 2004;28 : 334-339[CrossRef][Medline]
  12. Catalano O. Computed tomography in the study of gastrointestinal perforation. Radiol Med (Torino) 1996;91 : 247-252
  13. Ongolo-Zogo P, Borson O, Garcia P, Gruner L, Valette PJ. Acute gastroduodenal peptic ulcer perforation: contrast-enhanced and thin-section helical CT findings in 10 patients. Abdom Imaging1999; 24:329 -332[CrossRef][Medline]
  14. Miki T, Ogata S, Uto M, et al. Multidetector-row CT findings of colonic perforation: direct visualization of ruptured colonic wall. Abdom Imaging 2004;29 : 658-662[CrossRef][Medline]
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  16. Ghahremani GG. Radiologic evaluation of suspected gastrointestinal perforations. Radiol Clin North Am 1993;31 : 1219-1234[Medline]

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