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Technical Innovation |
1 Department of Radiology, University of California, San Francisco, Box 0628,
San Francisco, CA.
2 Department of Radiology, San Francisco General Hospital, 1001 Potrero Ave.,
Rm. 1X 55A, Box 1325, San Francisco, CA 94110.
Received September 11, 2003;
accepted after revision November 11, 2003.
Address correspondence to M. B. Gotway.
Introduction
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Helical CT Esophagography Technique
All patients were initially scanned with helical CT from the thoracic inlet
to the diaphragm using 5-mm collimation and 3-mm reconstruction increments. On
the initial scan, pneumomediastinum was seen in nine patients. This finding
raised suspicion for esophageal perforation and prompted the performance of
helical CT esophagography. Helical CT esophagography was performed to exclude
postsurgical anastomotic leak for the patient who refused fluoroscopic
esophagography. One patient had necrotizing pneumonia in the right upper lobe,
and helical CT esophagography was performed to exclude gastric-pulmonary
fistula.
All patients received approximately 50 mL of an aqueous solution consisting of 10% IV iodinated contrast material (Omnipaque 300 [iohexol], Nycomed), effervescent granules (sodium bicarbonate and tartaric acid), and water either by rapidly drinking the solution or by injection through a nasogastric tube. The granules were dissolved in 50 mL of water before consumption; when the solution was injected via syringe, care was taken not to draw any residual particulate into the syringe. Thoracic helical CT was then performed using the exact same parameters as those used for the initial scan without IV contrast material.
Medical records were reviewed for patients with negative findings on CT esophagography, no fluoroscopic examination with contrast material, and neither surgical nor endoscopic confirmation of esophageal perforation (n = 4).
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None of the patients aspirated the oral contrast solution. The additional CT scans required for CT esophagography added an average of approximately 4 min to the total examination time. Findings from studies were positive for esophageal perforation in five patients (Figs. 1A, 1B and 2A, 2B) and were negative in six patients. Fluoroscopic esophagography confirmed esophageal perforation in two patients with positive CT findings. Four of the five patients with positive CT findings underwent surgery, and esophageal perforation was confirmed in all; in the fifth patient, perforation of the intrathoracic stomach (gastric-pulmonary fistula) was endoscopically confirmed.
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Two patients who had negative results on helical CT esophagography underwent endoscopy, which did not reveal esophageal perforation in either patient.
Medical records were available in three of four patients undergoing CT esophagography who did not undergo fluoroscopic esophagography, endoscopy, or surgery. These patients were alive and without clinical evidence of mediastinitis at hospital discharge at a mean of 11 days (range, 0–30 days) after the CT examination.
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Fluoroscopic esophagography with water-soluble contrast material is the examination of choice for suspected esophageal perforation or rupture [2]. However, fluoroscopic esophagography performed with water-soluble contrast agents may produce false-negative results in 10–38% of patients [1, 4], and aspiration of hypertonic oral contrast solution may precipitate pulmonary edema [7]. Because false-negative results may occur, a second fluoroscopic esophagogram obtained with high-density barium is recommended to definitively exclude esophageal perforation [1]. This second examination results in additional radiation exposure, additional cost, and further delays in clinical management. Finally, although the inert nature of barium generally implies that aspiration of this contrast material is not associated with deleterious effects [7], recent evidence suggests that barium aspiration may produce severe pulmonary inflammation [8].
Many patients suspected of esophageal perforation are critically ill, and numerous physical and practical obstacles are inherent in the transfer of such patients to the fluoroscopy suite. The need for the radiologist to perform fluoroscopic esophagography may create further delay and cost.
Helical CT offers several advantages over fluoroscopic esophagography examinations [2, 4–6]. Helical CT esophagography can be performed after an initial thoracic CT scan is obtained to exclude other causes of chest pain, obviating transport of seriously ill patients to the fluoroscopy suite. The use of diluted low-osmolar IV contrast medium ensures that pulmonary edema will not result if the oral contrast medium is aspirated [7] and low-osmolar IV contrast medium that reaches extraluminal soft tissues through a perforated viscus or ruptured vessel has not been associated with deleterious effects [7]. Helical CT can readily detect the small periesophageal air collections that indicate the presence of esophageal perforation more readily than fluoroscopic esophagography; such air collections may be the most useful finding for suggesting the presence of esophageal rupture [4, 5]. Finally, helical CT esophagography is easy to perform, and CT technicians and nurses can readily be trained in its use. Once trained, CT technologists can perform helical CT esophagography without direct radiologist supervision, allowing the radiologist to attend to other duties or remain off-site and interpret the examination remotely.
The use of effervescent agents for the evaluation of patients with suspected esophageal rupture is controversial. Although effervescent granules contain biologically inert components and the use of these agents has not been associated with reported complications beyond the setting of suspected gastrointestinal obstruction, the effect of these agents—if the solid granules enter the mediastinum—is unknown. However, the granules themselves dissolve quickly before administration, so it is unlikely that solid granules will enter the mediastinum. Nevertheless, the granules should be completely dissolved before administration to avoid the unlikely event of complications related to effervescent granule administration. Alternatively, the examination may be performed without effervescent agents followed by effervescent agent administration if no perforation is seen on the initial scan.
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