ULTRASOUND APPEARANCE OF NORMAL LUNG BORDERS AND ADJACENT VISCERA IN THE HORSE*

B-mode ultrasound was utilized to define the borders of the lungs and surrounding viscera in a normal horse. Characteristic reverberation artifacts produced by the air-filled lung allowed accurate definition of the lung borders. The liver on the right and the spleen on the left were the predominant parenchymal organs identified. These two organs were seen adjacent to the lung and medial to the diaphragm. Recognition of the liver and spleen is important in evaluating equine pleural effusion.     

DETECTION OF PNEUMOTHORAX AND PLEURAL EFFUSION WITH HORIZONTAL BEAM RADIOGRAPHY

Forty‐seven patients with a known history of thoracic trauma or clinical suspicion of pneumothorax were selected for thoracic imaging. The patient population was composed of 42 dogs and five cats. Standard vertical beam (VB) left and right lateral and ventrodorsal/dorsoventral (VD/DV) projections were obtained for each patient, and at least one horizontal beam (HB) projection (VD projection made in lateral recumbency). A total of 240 images were reviewed. Subjective assessment for the presence and degree of pneumothorax and pleural effusion was made more confidently with HB projections. Pneumothorax was identified in at least one projection in 26 patients (26 dogs) and pleural effusion in 21 patients (19 dogs and two cats). Pneumothorax and pleural effusion were present concurrently in 17 dogs. Pneumothorax and pleural effusion were graded for each image as absent, mild, moderate, or severe. Right (P<0.001) and left (P<0.05) lateral HB VD projections and the standard VB left lateral projection (P<0.05) were significantly more likely to detect and grade pneumothorax severely than the VB VD/DV views. The right lateral HB projection had the highest rate of detection and gradation of severity for pneumothorax compared with other views. VD/DV projections had the lowest sensitivity for detection of the pneumothorax and gradation of severity for pneumothorax and pleural effusion. No significant difference in diagnosis (P=0.9149) and grade (P=0.7757) of pleural effusion were seen between views, although the left lateral HB had both the highest rate of detection and grade of severity.     

THE UTILITY OF THORACIC RADIOGRAPHIC MEASUREMENT FOR THE DETECTION OF CARDIOMEGALY IN CATS WITH PLEURAL EFFUSION

Right lateral thoracic radiographs from four groups of age and weight matched cats were evaluated retrospectively to determine the utility of thoracic mensuration in distinguishing the cause of pleural effusion. Group 1 cats had no thoracic abnormalities (n = 40); Group 2 cats had cardiomegaly without pleural effusion (n = 12); Group 3 cats had noncardiogenic pleural effusion (n = 10); Group 4 cats had cardiogenic pleural effusion (n = 18). Measurements obtained from the radiographs demonstrated tracheal elevation in cats with cardiomegaly alone and in cats with pleural effusion, regardless of cause. These data demonstrate that pleural effusion displaces the thoracic viscera dorsally, thereby mimicking cardiomegaly. Similar measurements failed to differentiate cardiogenic from noncardiogenic pleural effusion, with the exception of the lateral thoracic dimension.     

DIAGNOSTIC SENSITIVITY OF SUBJECTIVE AND QUANTITATIVE LARYNGEAL ULTRASONOGRAPHY FOR RECURRENT LARYNGEAL NEUROPATHY IN HORSES

Recurrent laryngeal neuropathy (RLN) is the most common cause of laryngeal hemiplegia in horses and causes neurogenic atrophy of the intrinsic laryngeal muscles, including the cricoarytenoideus lateralis muscle. Recurrent laryngeal neuropathy results in paresis to paralysis of the vocal fold and arytenoid cartilage, which limits performance through respiratory compromise. Ultrasound has previously been reported to be a useful diagnostic technique in horses with RLN. In this report, the diagnostic sensitivity of subjective and quantitative laryngeal ultrasonography was evaluated in 154 horses presented for poor performance due to suspected upper airway disease. Ultrasonographic parameters recorded were: cricoarytenoideus lateralis echogenicity (subjective and quantitative), cricoarytenoideus lateralis thickness, vocal fold movement, and arytenoid cartilage movement. Ultrasonographic parameters were then compared with laryngeal grades based on resting and exercising upper airway endoscopy. Subjectively increased left cricoarytenoideus lateralis echogenicity yielded a sensitivity of 94.59% and specificity of 94.54% for detecting RLN, based on the reference standard of exercising laryngeal endoscopy. Quantitative left cricoarytenoideus lateralis echogenicity values differed among resting laryngeal grades I–IV. Findings from this study support previously published findings and the utility of subjective and quantitative laryngeal ultrasound as diagnostic tools for horses with poor performance.     

COMPARISON OF THORACIC ULTRASONOGRAPHY AND RADIOGRAPHY FOR THE DETECTION OF INDUCED SMALL VOLUME PNEUMOTHORAX IN THE HORSE

Small volume pneumothorax can be challenging to diagnose in horses. The current standard method for diagnosis is standing thoracic radiography. We hypothesized that thoracic ultrasonography would be more sensitive. Objectives of this prospective, experimental study were to describe a thoracic ultrasound method for detection of small volume pneumothorax in horses and to compare results of radiography and ultrasound in a sample of horses with induced small volume pneumothorax. Six mature healthy horses were recruited for this study. For each horse, five 50 ml air boluses were sequentially introduced via a teat cannula into the pleural space. Lateral thoracic radiographs and standardized ultrasound (2D and M‐mode) examinations of both hemithoraces were performed following administration of each 50 ml air bolus. Radiographs and ultrasound images/videos were analyzed for detection of pneumothorax by four independent investigators who were unaware of treatment status. Sensitivity, specificity, positive predictive values, negative predictive values, and agreement among investigators (Kappa test, κ) were calculated for radiography, 2D and M‐mode ultrasound. Comparisons were made using a chi‐squared exact test with significance set at P < 0.05. Two‐dimensional (84%) and M‐mode (80%) ultrasound were more sensitive than radiography (48%) for pneumothorax detection (P = 0.02 and P = 0.04, respectively). Specificity and positive predictive values were similar for all three imaging modalities (P = 1). Agreement between investigators for pneumothorax detection was excellent for 2D ultrasound (κ = 1), very good for M‐mode ultrasound (κ = 0.87), and good for radiography (κ = 0.79). Findings from this experimental study supported the use of thoracic ultrasonography as a diagnostic method for detecting pneumothorax in horses.     

TRANSRECTAL ULTRASONOGRAPHY OF THE LEFT ADRENAL GLAND IN HEALTHY HORSES

Little information is available on medical imaging of the adrenal glands in horses. We investigated the feasibility of transrectal ultrasonography to characterize the normal equine adrenal gland. Transrectal ultrasonography was performed in 25 healthy horses using a 7.5 MHz linear array probe at a displayed depth of 8 cm. Transrectal ultrasonography of the right adrenal gland was not feasible. For the left adrenal gland, the left kidney, the abdominal aorta, the left renal artery, the left renal vein, and the cranial mesenteric artery were used as landmarks. The size of the left adrenal gland was variable, but it generally appeared as a long, flat structure with a hyperechoic medulla surrounded by a hypoechoic cortex. The most cranial part of the gland could not be delineated appropriately in 11 horses (44%). The mean (±SD) thickness of the gland and medulla was 0.66±0.15 cm (n=25) and 0.28±0.09 cm (n=25) near the caudal pole, 0.87±0.25 cm (n=14) and 0.40±0.18 cm (n=12) near the cranial pole, and 0.89±0.18 cm (n=25) and 0.36±0.13 cm (n=25) in the middle of the gland, respectively. The mean (±SD) length of the entire adrenal gland and of the medulla was 6.22±0.77 cm (n=14) and 5.45±0.71 cm (n=6), respectively. Transrectal ultrasonography allowed adequate visualization of the left adrenal gland in horses.     

ULTRASONOGRAPHIC ASSESSMENT OF LARYNGOHYOID POSITION AS A PREDICTOR OF DORSAL DISPLACEMENT OF THE SOFT PALATE IN HORSES

Dorsal displacement of the soft palate is an important cause of poor performance in racehorses, yet its etiology is not fully understood. Diagnosis requires treadmill videoendoscopy, which is not widely available. The relationship of the larynx, the hyoid apparatus, and the remainder of the skull may be important in predisposing horses to dorsal displacement of the soft palate. We hypothesized that this relationship could be accurately assessed in unsedated horses through ultrasonographic examination. Fifty-six racehorses presented for evaluation of poor performance were subjected to treadmill videoendoscopy and resting ultrasonography. Using ultrasound-assisted percutaneous measures of laryngo-hyoid position, the relationship between selected anatomic structures and the occurrence of dorsal displacement of the soft palate was evaluated. A significant relationship was found between the depth of the basihyoid bone at rest and the occurrence of dorsal displacement of the soft palate at exercise ( P =0.03). Other measures of laryngohyoid position were not found to be associated with dorsal displacement of the soft palate. Thus, there is an association between the occurrence of dorsal displacement of the soft palate at exercise and the resting position of the basihyoid bone, whereby on average a more ventral location of the basihyoid bone is present in horses with dorsal displacement of the soft palate. The pathophysiologic implications of this finding are not fully understood but, based on our findings, ultrasound examination is of value in assisting in the diagnosis of dorsal displacement of the soft palate.     

ULTRASONOGRAPHY AS A DIAGNOSTIC TOOL IN SHARK SPECIES

The use of sonography was evaluated in eleven sharks as a potential diagnostic and investigative tool. Individual sharks were anesthetized with MS-222 (Tricane Methane Sulphonate) and sonograms recorded from various planes using a 3 MHZ linear array scanner. Sonographic images were compared with corresponding postmortem cross sections. Heart rate and rhythm were monitored with real time sonography in an attempt to gauge the depth of the anesthesia. Heart rates ranged from 12–46 bpm. Initial results of this study suggest that sonography may be a useful technique in shark species where the application of radiographic techniques is limited by the lack of adipose tissue and the need to maintain the animal in water.     

SONOGRAPHIC ESTIMATION OF PLEURAL FLUID VOLUME IN DOGS

The aim of this study was to find an ultrasonographic method to estimate pleural fluid volume in dogs. Nine canine cadavers of mixed breed were studied. Using a transsternal view, linear measurements from the pleural surface of the midline of the sternebra at the center of the heart to the furthest ventrolateral point of both right and left lung edges were recorded. Isotonic saline was injected using ultrasound guidance into both right and left pleural spaces and the measurements were repeated using standard increments until 1000 ml total volume was reached. No relationship was identified between mean distance and injected volume up to 100 ml. Thereafter, the mean distance increased in an approximately linear relationship with the cube root of fluid volume. There was a high correlation ( r ≥0.899) between the ultrasonographic measurement and fluid volume within individual dogs, but it was not possible to produce a useful equation to calculate absolute pleural fluid volume for new subjects. Nevertheless, ultrasonography may be used to semiquantitatively monitor pleural fluid volume, so that a decrease in the mean linear measurement obtained reflects a decrease in the total fluid volume.     

ULTRASONOGRAPHIC DIAGNOSIS OF DIAPHRAGMATIC RUPTURE IN A HORSE

Real–time ultrasonography was used to confirm diaphragmatic rupture in a horse that developed pleural effusion following a traumatic event. Pleural effusion, a cranially displaced crus, and a cranially positioned sacculated loop of bowel were seen radiographically. The presence of gas–filled intestine cranial and dorsal to the diaphragm was detected by ultrasound imaging. The use of ultrasound and radiography in the diagnosis of diaphragmatic rupture is discussed.     

DIAGNOSTIC PNEUMOPERICARDIOGRAPHY IN DOGS WITH SPONTANEOUS PERICARDIAL EFFUSION

To evaluate the diagnostic accuracy of pneumopericardiography, diagnostic pneumopericardiograms from 39 dogs with spontaneous pericardial effusion of various etiologies were reviewed. Diagnoses were confirmed by surgical biopsy, necropsy, or follow-up evaluation. Thirty-two of 39 studies (82%) were considered diagnostic. There were one false-positive and six false-negative studies. Fifteen of 16 studies (94%) in dogs with idiopathic sanguinous pericardial effusion were negative (i.e., similar to those in normal dogs). Seven of 12 right atrial hemangiosarcomas (58%), six of six heartbase neoplasms (100%), and two of two pericardial cysts (100%) were outlined. Studies in two cases of infective pericarditis revealed abnormal findings, while a negative study was obtained in one patient with pericardial mesothelioma. Lateral positions were most valuable in idiopathic effusions and for outlining heartbase neoplasms. The left lateral recumbent position was particularly important for outlining hemangiosarcomas. Pericardial cysts were profiled best in ventral or dorsal recumbent positions. This study documents the high diagnostic potential of technically adequate pneumopericardiograms in the etiologic diagnosis of pericardial effusion in the dog.     

ULTRASONOGRAPHY AS AN AID IN THE DIAGNOSIS OF RENAL CELL CARCINOMA IN A HORSE

Clinical diagnosis of renal tumors in the horse has been difficult because the traditional diagnostic techniques are inadequate. Because of this shortcoming, early publications rarely reported antemortem diagnosis of primary renal tumors. Conventional radiographic techniques cannot effectively outline kidneys in the adult horse. With the advent of ultrasonography, a new dimension to the evaluation of the large-animal kidney has been introduced. Percutaneous diagnostic ultrasonography provides a noninvasive method of examining both kidneys. This report describes a 15 year-old Tennessee Walking Horse mare presented for evaluation of a mass in the sublumbar region, polyuria and polydipsia. Clinical examination and laboratory test results suggested intra-abdominal neoplasia. Two-dimensional ultrasonographic images of the mass were consistent with renal neoplasia. Histologic diagnosis of ultrasound-guided renal biopsy was renal tubular cell carcinoma.     

DIAGNOSTIC VALUE OF ULTRASONOGRAPHY IN DIFFERENTIATING ENTERITIS FROM INTESTINAL NEOPLASIA IN DOGS

One hundred and fifty dogs with histopathologically confirmed intestinal disease were evaluated retrospectively. Sixty-one dogs had enteritis and 89 dogs had intestinal neoplasia. Ultrasonographic findings including the thickness and distribution of the intestinal lesion, the integrity of intestinal wall layering, regional lymph node thickness, the location of the intestinal segment involved, and regional motility were evaluated. Dogs with intestinal tumor had wall thickness (1.5 cm) significantly greater than dogs with NSE lesions (0.6 cm; p < 0.001). Ninety-nine percent of dogs with intestinal tumor had loss of wall layering while 88% of dogs with NSE had normal or altered wall layering (p < 0.001). Dogs with NSE were significantly more likely to have diffuse lesion (72%) than dogs with intestinal tumor (2%; p < 0.001). Lymph node median thickness in 24/61 dogs with NSE was 1.00 cm. The median thickness of the lymph nodes in 56/89 dogs with intestinal tumors was 1.9 cm. A multivariate analysis showed that loss of wall layering alone was an excellent predictive factor in differentiating intestinal tumor from NSE. In our population, dogs with loss of intestinal wall layering were 50.9 times more likely to have a tumor than enteritis.     

ULTRASONOGRAPHIC APPEARANCE OF THE LOWER URINARY TRACT IN FIFTEEN NORMAL HORSES

The purpose of this study was to describe the normal ultrasonographic appearance of the caudal portion of the equine ureters, pelvic urethra, and urinary bladder and to assess ureteral contractility. Fifteen horses with no evidence of urinary tract disease (five females, five intact males and five geldings) were studied. The lower urinary tract was evaluated ultrasonographically using a transrectal approach. The normal ultrasonographic appearance and anatomic location of structures of the lower urinary tract were evaluated and anatomic relationships described. Both ureters were identified dorsal to the bladder and at their openings into the bladder. Their relationship and different appearance from the male deferent ducts/ampullae and vesicular glands was noted. Ultrasonographic measurements of the diameter of the ureters and urethra were obtained and the ureteral, urethral, and urinary bladder wall thickness recorded. The normal parameters established in this study will be useful during sonographic examination of horses with suspected urinary tract disease. Transrectal ultrasonographic examination is valuable in assessing the presence and frequency of ureteral contractions as well as in detecting structural abnormalities of the lower urinary tract. The use of high-frequency transrectal ultrasound transducers allows for excellent visualization of the structures of the equine lower urinary tract.     

M-MODE ECHOCARDIOGRAPHY AS A DIAGNOSTIC AID FOR FELINE CARDIOMYOPATHY

Normal cats and cats with congestive cardiomyopathy (CCM) and hypertrophic cardiomyopathy (HCM) were examined using M-mode echocardiography to determine its diagnostic capabilities. Sixteen normal cats were examined to verify previously reported data and to add further echocardiographic inforamtion (left atrial/aortic root ratio, left posterior wall thickness at end systole and end diastole, amplitude of mitral valve excursions, and velocity of valve opening and closure) to aid in differential diagnosis. Significant (p<0.05) changes were detected between the normal cats and those with cardiomyopathy. In each type of cardiomyopathy, alterations in left atrial dimension, left atrial/aortic root ratio, left ventricular dimension, left ventricular wall thickness and percentage of ventricular dimensional change were identified. Altered mitral valve motion was found with HCM. Echocardiography was found to be an accurate technique for definitive diagnosis of feline cardiomyopathy.     

ULTRASONOGRAPHY OF THE FEMORAL ARTERY IN SIX NORMAL HORSES AND THREE HORSES WITH THROMBOSIS

Ultrasonography of the femoral artery in the horse, including color, power and spectral Doppler, provides morphologic and dynamic information. This paper describes the use of the techniques in six clinically normal horses and three with femoral artery thrombosis. Useful landmarks for orientation are the saphenous artery and the medial saphenous vein. The lateral circumflex femoral artery can not be visualized. Recognition of the genus descendens artery is complicated due to the presence of multiple distal caudal femoral arteries. The femoral artery feeds a high resistance bed. In normal horses the peak systolic velocity varies between 50–90 cm/sec. Echoic tissue in the femoral artery lumen with stenosis, occlusion and collateral blood flow formation are features encountered in the patients.     

DIAGNOSTIC ACCURACY OF GRAY‐SCALE ULTRASONOGRAPHY FOR THE DETECTION OF HEPATIC AND SPLENIC LYMPHOMA IN DOGS

Gray‐scale ultrasonography is often used to screen for involvement of the liver and spleen in canine lymphoma patients but the utility of sonography for staging lymphoma has not been evaluated quantitatively. We performed abdominal sonography in 28 dogs with a confirmed diagnosis of lymphoma. Needle aspirates were obtained for cytology from three separate sites in the liver and three sites in the spleen and the sonographic appearance was noted at each site. Our hypothesis was that in dogs newly diagnosed with lymphoma, abnormal appearance of the liver or spleen on ultrasound examination is an indication that lymphoma is present in that organ. Cytologic evaluation was used as the gold standard. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of hepatic and splenic abnormalities seen on ultrasound for diagnosis of lymphoma were 72.7%, 80.6%, 77.4%, 76.3%, and 76.8% for the liver, respectively, and 100%, 23.3%, 64.6%, 100%, and 68.1% for the spleen, respectively. Based on these results, we recommend that aspirates be performed for detection of lymphoma in the spleen of dogs only when the spleen appears abnormal ultrasonographically and that cytology of the liver be performed, regardless of ultrasonographic appearance, to determine the presence or absence of lymphoma.     

EVALUATION OF THE EXTIRPATED EQUINE EYE USING B-MODE ULTRASONOGRAPHY

B-mode ultrasonography using a 7.5 megahertz (MH^z) transducer was performed on 95 equine cadaver eyes submerged in a water bath. Identification and measurement of the anterior to posterior diameters of the intraocular structures and of the axis bulbi was done. The dorsal ventral axis of the eye was also measured. The eyes were then frozen, sectioned in a saggital plane and the same measurements were made using calipers. Two sets of measurements were then compared statistically.
With the exception of the cornea and the dorsal ventral axis measurements of male horses there was no statistically significant difference in the measurements obtained by the two methods.
The use of B-mode ultrasonography at a frequency of 7.5 MH^z to examine the architecture of the equine eye is suggested as a valuable clinical tool. Biometry of the intraocular structures at this frequency may be reasonably accurate.