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1
Department of Radiology, University of Würzburg,
Josef-Schneider-Str. 2, D-97080 Würzburg,
Germany.
2
Department of Otorhinolaryngology, Head and Neck Surgery, University of
Würzburg, D-97080
Würzburg, Germany.
Received February 23, 2000;
accepted after revision May 3, 2000.
Address correspondence to M. Keberle.
Abstract
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SUBJECTS AND METHODS. Visual and objective in vitro comparisons of an iodinated aqueous contrast agent, a 50% weight/volume barium suspension, and a 100% weight/volume barium suspension were performed. Moreover, to exclude pharyngeal perforation after surgery, we prospectively examined 109 patients by pharyngography, using the aqueous contrast agent and the 100% weight/volume barium suspension. All patients with a pharyngeal perforation were followed up clinically to exclude complications due to barium application.
RESULTS. As opposed to the 100% weight/volume barium suspension, in vitro comparison between the aqueous contrast agent and the 50% weight/volume barium suspension yielded no substantial differences. Seventeen perforations could be detected with the aqueous contrast agent. Although 10 of 17 perforations could be slightly better visualized with the 100% weight/volume barium suspension, two perforations were missed with this agent. Five perforations were equally well detected with both.
CONCLUSION. Because of a higher radiopacity, 100% weight/volume barium suspensions may more sharply delineate perforations. However, in contrast to aqueous contrast media, narrow pharyngeal perforations can be missed. Thus, the use of a 100% weight/volume barium suspension does not improve the detection of pharyngeal perforation.
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For an objective comparison, the respective CT densities were determined. Syringes filled with 1:10 watery dilutions of the iodinated aqueous contrast agent, the 50% wt/vol, and the 100% wt/vol barium suspension were scanned separately. Three regions of interest (1.9 cm2) were placed within each of the contrast agents. This procedure was repeated twice after renewal of the dilutions for the determination of mean values.
Pharyngography
This study was performed according to the ethical standards of the
institutional committee on human experimentation. During a 13-month period,
118 patients, 18 women and 100 men (median age, 64 years; range, 35-86 years)
were routinely seen 5-10 days after pharyngeal surgery, such as pharyngotomy
or partial pharyngectomy, and underwent pharyngography at our institution
after informed consent was obtained. Indications for pharyngography were
exclusion of leakage after surgery and exclusion of aspiration before oral
feeding began.
Before starting the pharyngography study, we initially administered a swallow of a 30-50% watery dilution of the iodinated aqueous contrast agent (Telebrix) to detect aspiration. Because of this procedure, nine of 118 patients were excluded from the study to avoid aspiration of undiluted Telebrix (1889 mOsm/kg), bearing the risk of lung edema. No adverse effects were noted in these patients after aspiration of the diluted iodinated contrast agent.
The pharyngography study (n = 109) was performed with the undiluted aqueous contrast agent (Telebrix). After a short period of 1-15 min, when no or only faint remnants of the diffused aqueous contrast agent were noticeable, we repeated the examination in all patients, using the 100% wt/vol barium suspension. Because of technical and ethical aspects, we did not perform a third examination using 50% wt/vol barium suspensions such as that done in vitro. Technically, a 50% wt/vol barium suspension does not diffuse, and, therefore, an in vivo comparison with a 100% wt/vol barium suspension is difficult to perform.
Pharyngography was performed with a digital fluoroscopy unit (Diagnost 92; Philips, Eindhoven, The Netherlands) under the auspices of an experienced radiologist. The pharynx was recorded dynamically (four to eight images per second) in the anteroposterior, lateral, and oblique projections with the patient in an upright position (diameter of field of view of the intensifier, 36 cm). For the best achievable spatial resolution, all regions of the pharynx were consecutively examined with the smallest field of view of 17 cm. The same exposure parameters as those used for the in vitro test were used (automatic exposure, 70 kV; small focal spot).
Two radiologists, who were not aware of the results, analyzed first the images obtained with the aqueous contrast agent and then the images obtained with 100% wt/vol barium suspension. Perforation was diagnosed when an extravasation of contrast agent achieved a length of at least 1 cm. In case of faint remnants of the iodinated aqueous contrast agent, the perforation had to be newly filled with the 100% wt/vol barium suspension to be considered detected by this agent as well. The Wilcoxon's test was performed to evaluate a statistically significant difference between both contrast agents regarding the detection of perforations. Moreover, both contrast agents were directly compared regarding the differences in the delineation of the lesions. A consensus was reached in all cases. After either conservative or surgical treatment, patients with perforations were followed up clinically (clinical examinations, basic laboratory examinations, and indirect laryngoscopy) for at least 6 months.
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Pharyngography
Totally, 17 perforations were detected with the aqueous contrast agent and
clearly visualized regarding contrast and length. In 10 of these perforations,
the 100% wt/vol barium suspension visually yielded a slightly better contrast
than the aqueous contrast agent; in five perforations, the 100% wt/vol barium
suspension and the iodinated aqueous contrast agent presented equally.
However, two (11.8%; p = 0.16) of 17 perforations (with lengths of 1
and 5 cm) could not be detected after the administration of the 100% wt/vol
barium suspension (Fig.
2A,2B).
During the follow-up period, no apparent clinical complications related to the
use of barium were noted in the patients with perforations.
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In Vitro Experiments
Both in vitro tests in our study did not show a substantial difference in
contrast between the aqueous contrast agent and the 50% wt/vol barium
suspension. However, another group of researchers noted a visual difference of
the latter contrast media in a similar in vitro experiment, also underlining
this observation with a report of six cases of upper gastrointestinal
perforation that were better detected with a 50% wt/vol barium suspension
[3]. On the basis of our in
vitro observations (and because of technical and ethical aspects), we did not
use a 50% wt/vol barium suspension as a third contrast agent for
pharyngographies in this study. Here, a comparison of an iodinated aqueous
contrast agent with a 100% wt/vol barium suspension similar to that used in a
recent study on esophageal perforations was performed
[4].
Pharyngography
Before comparison of the diagnostic benefits of the respective contrast
media, safety aspects must be addressed. The assumption that barium sulfate
has the same low risk of serious adverse effects in the parapharyngeal space
as it does in the mediastinum was confirmed by clinical follow-ups: no
complications occurred in any case of parapharyngeal perforation (n =
17). During this period, no fever or any other apparent clinical sign of
inflammatory reactions that needed treatment with antibiotics or surgical
intervention was seen. Nevertheless, we have no histologic proof of a lack of
inflammation. Pulmonary edema after aspiration of aqueous contrast media can
be avoided by the initial use of a 30-50% watery dilution of an iodinated
aqueous contrast agent, such as the one used in this study, or by the use of
ready-to-use iodinated contrast agents with low osmolality
[4,
6].
Our results show that the 100% wt/vol barium suspension may more sharply delineate pharyngeal perforations because of its higher radiographic density [1] and may eventually result in an improved conspicuity in particular individual patients. On the other hand, with the aqueous contrast agent all perforations were clearly visualized. In none of the patients was an interpretation difficult with the aqueous contrast agent alone. Thus, the 100% wt/vol barium suspension did not give any additional information regarding pharyngeal perforations in this study. Moreover, two narrow fistulous tracts were detected only with the aqueous contrast agent, but not with the 100% wt/vol barium suspension (Fig. 2A,2B). Because of the small number of patients with perforations, the difference between both contrast agents regarding the detection of perforation is not statistically significant. Nevertheless, our results do not support the growing tendency toward the use of barium suspensions for the detection of small tears in the esophagus [3,4,5]. The reasons for our results are probably a combination of narrow fistulous tracts, the consistency of the barium suspension with its higher viscosity, and a different swallow physiology in the pharynx compared with the esophagus. Higher viscosity and narrow fistulous tracts are likely but, on the other hand, another group showed that 100% wt/vol barium suspension may well delineate small tears with volumes of less than 1 cm3 [5]. However, no comments were given on how narrow these tears were. Our belief is that a 100% wt/vol barium suspension might be too viscous to fill a narrow fistula. Our results might also be explained by the distinct swallow physiology of the pharynx, which in contrast to the esophagus, is characterized by the absence of a concentric muscle contraction for an active bolus transportation. However, the significance of each of these particular reasons remains unknown until proven by future studies.
In conclusion, the 100% wt/vol barium suspension did not detect pharyngeal perforations as often as the aqueous contrast agent, in spite of its gaining acceptance as an additional [3, 4] or sole [5] contrast agent in the detection of esophageal tears. Thus, we recommend the use of iodinated aqueous contrast media to exclude pharyngeal perforation after surgery. In consultation with our ear, nose, and throat surgeons, we decided to forgo additional use of 100% wt/vol barium suspension in this subset of patients. Further studies regarding differences in viscosity and rates of resorption or diffusion are needed to test various dilutions of barium suspensions in the detection of pharyngeal perforations. But these dilutions will result in a lower radiopacity comparable to iodinated aqueous contrast media and, nevertheless, pose the potential risk of granulomatous inflammatory reactions, especially with radiologists' predisposition to use barium sulfate and its potential contact with the pleural membranes [1, 2].
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