EVALUATION OF THE CANINE TYMPANIC MEMBRANE BY POSITIVE CONTRAST EAR CANALOGRAPHY

Positive contrast ear canalography was described briefly in 1973 as a method for detecting rupture of the tympanic membrane in dogs with oti tis media. The purpose of this study was to evaluate the sensitivity a nd usefulness of the technique, The ears of 10 normal canine cadavers and 31 dogs with clinical signs of ear disease were examined using oto scopy, radiography and contrast radiography after infusing 2 to 5 ml o f positive contrast medium into the ear canals, These examinations wer e repeated in the cadavers after the tympanic membrane had been punctu red with a Spreull needle, In the cadavers 14 of 19 (74 per cent) of t he tympanic membranes were visible otoscopically; contrast medium did not enter the tympanic bulla of any of the ears before the tympanic me mbrane was ruptured, but was visible in the bulla in every ear after r upture, In the clinical study, 40 of 61 (66 per cent) of the tympanic membranes were visible otoscopically, and 12 appeared to be ruptured, Radiographic signs of otitis media (increased opacity and/or thickenin g of the tympanic bulla) were identified in seven ears, Canalography w as positive for rupture of the tympanic membrane in 13 ears, including four in which it appeared to be intact otoscopically, In normal canin e ears, canalography was a more accurate method for detecting iatrogen ic tympanic membrane rupture than otoscopy, In dogs with ear disease, canalography may be more sensitive for otitis media than either otosco py or survey radiography.