THE EFFECT OF BARIUM TEMPERATURE ON ESOPHAGEAL AND GASTRIC MOTILITY IN DOGS

The influence of barium temperature on canine esophageal transit time and gastric motility were studied fluoroscopically. Micropulverized barium sulfate (30% wt/vol) at 35°F, 70°F, and 100°F was given orally to each of five dogs with a minimum of two hours between each temperature. Esophageal transit times ranged from 4 to 9.67 seconds, and gastric contractions average four per minute. Barium temperature had no significant effect on either esophageal transit time or gastric motility.     

Diagnostic outcome of contrast videofluoroscopic swallowing studies in 216 dysphagic dogs

Determining the anatomic and functional origin for dysphagia is critical for development of an appropriate therapeutic plan and determination of the prognosis. The purpose of this retrospective study was to report the quantitative and qualitative outcome of contrast videofluoroscopic swallowing studies in a large cohort of dysphagic dogs presenting to a tertiary veterinary care hospital. The videofluoroscopic swallowing studies were reviewed to generate values for pharyngeal constriction ratio, timing of swallowing events (maximum pharyngeal contraction, opening of upper esophageal sphincter, closing of upper esophageal sphincter, and reopening of epiglottis), type of esophageal peristalsis generated, and esophageal transit time. One or more anatomic locations for origin of dysphagia were assigned (pharyngeal, cricopharyngeal, esophageal (primary motility disorder), other esophageal (stricture, vascular ring anomaly, mass), lower esophageal sphincter/hiatus. Sixty‐one of 216 studies (28%) were deemed unremarkable. Twenty‐seven of 216 dogs (13%) had pharyngeal dysphagia, 17/216 dogs (8%) had cricopharyngeal dysphagia, 98/216 dogs (45%) had dysphagia secondary to esophageal dysmotility, 19/216 dogs (9%) had dysphagia secondary to focal esophageal disorders, and 97/216 dogs (45%) had dysphagia of lower esophageal sphincter/hiatus origin. Multiple abnormalities were present in 82/216 (38%) dogs. Elevated pharyngeal constriction ratio was associated with pharyngeal, cricopharyngeal, and esophageal motility disorders, delayed upper esophageal sphincter opening was associated with cricopharyngeal disorders, a lower percentage of primary esophageal peristaltic waves was associated with cricopharyngeal, pharyngeal, or primary esophageal motility disorders. In conclusion, videofluoroscopic swallowing studies was pivotal in the diagnosis of dysphagia with 155/216 (72%) dogs receiving a final diagnosis.     

THE EFFECT OF DEXMEDETOMIDINE ON RADIOGRAPHIC CARDIAC SILHOUETTE SIZE IN HEALTHY CATS

Dexmedetomidine, an alpha₂‐adrenergic agonist, may be used in companion animals for chemical restraint, including cardiac evaluation. Echocardiographic changes associated with alpha₂‐adrenergic agonists have been described; however reports of radiographic changes in cats were not found at the time of this study. Aims of this observational, prospective, experimental study were to describe the effects of dexmedetomidine on the radiographic appearance of the cardiac silhouette in healthy, adult cats. Fourteen healthy adult cats received dexmedetomidine 40 mcg/kg IM. Right lateral, left lateral, ventrodorsal, and dorsoventral thoracic radiographs were obtained for each cat at three time points: presedation, intrasedation, and postsedation (≥ two hours after reversal with atipamezole). Radiographs were evaluated in a blinded, randomized fashion by two independent observers using the vertebral heart score on all four views, the number of intercostal spaces on lateral projections, and the percent width of thorax on ventrodorsal and dorsoventral projections. Median vertebral heart score on right lateral view was significantly increased intrasedation (median = 7.8; range = 7.25–8.25) compared to presedation (median = 7.5; range = 7–8 [P = 0.001]). Median percentage width was significantly higher intrasedation (70% on VD; range 65–80 [P = 0.001], and 75% on DV; range 65–80 [P = 0.006]) compared to presedation (65%; range 65–75 on both projections). Dexmedetomidine was associated with a small but significant increase in cardiac silhouette size on right lateral (vertebral heart score), ventrodorsal (percentage width), and dorsoventral (percentage width) radiographs in healthy adult cats. This effect should be taken into consideration for future interpretation of thoracic radiographs in dexmedetomidine‐sedated cats.     

EFFECT OF SEDATION ON CONTRAST‐ENHANCED ULTRASONOGRAPHY OF THE SPLEEN IN HEALTHY DOGS

Contrast‐enhanced ultrasound of the spleen enables the dynamic assessment of the perfusion of this organ, however, both subjective and quantitative evaluation can be strongly influenced by sedative agent administration. The purpose of this prospective, experimental study was to test effects of two sedative agents on splenic perfusion during contrast‐enhanced ultrasound of the spleen in a sample of healthy dogs. Contrast‐enhanced ultrasound of the spleen was repeated in six healthy Beagles following a cross‐over study design comparing three protocols: awake, butorphanol 0.2 mg/Kg intramuscular (IM), and dexmedetomidine 500 μg/m² IM. After intravenous injection of a phospholipid stabilized sulfur hexafluoride microbubble solution (SonoVue®, Bracco Imaging, Milano, Italy), the enhancement intensity and perfusion pattern of the splenic parenchyma were assessed and perfusion parameters were calculated. Normal spleen was slightly heterogeneous in the early phase, but the parenchyma was homogeneous at a later phase. Sedation with butorphanol did not modify perfusion of the spleen. Dexmedetomidine significantly reduced splenic enhancement, providing diffuse parenchymal hypoechogenicity during the entire examination. Measured parameters were significantly modified, with increased arrival time (AT; (< 0.0001) and time to peak (TTP; P < 0.0001), and decreased peak intensity (PI; P = 0.0108), wash‐in (P = 0.0014), and area under the curve (AUC; P = 0.0421). Findings supported the use of butorphanol and contraindicated the use of dexmedetomidine as sedatives for splenic contrast ultrasound procedures in dogs. Short‐term and diffuse heterogeneity of the spleen in the early venous phase was determined to be a normal finding.     

COMPARISON OF FLUOROSCOPY AND COMPUTED TOMOGRAPHY FOR TRACHEAL LUMEN DIAMETER MEASUREMENT AND DETERMINATION OF INTRALUMINAL STENT SIZE IN HEALTHY DOGS

Tracheal collapse is a progressive airway disease that can ultimately result in complete airway obstruction. Intraluminal tracheal stents are a minimally invasive and viable treatment for tracheal collapse once the disease becomes refractory to medical management. Intraluminal stent size is chosen based on the maximum measured tracheal diameter during maximum inflation. The purpose of this prospective, cross‐sectional study was to compare tracheal lumen diameter measurements and subsequent selected stent size using both fluoroscopy and CT and to evaluate inter‐ and intraobserver variability of the measurements. Seventeen healthy Beagles were anesthetized and imaged with fluoroscopy and CT with positive pressure ventilation to 20 cm H₂O. Fluoroscopic and CT maximum tracheal diameters were measured by three readers. Three individual measurements were made at eight predetermined tracheal sites for dorsoventral (height) and laterolateral (width) dimensions. Tracheal diameters and stent sizes (based on the maximum tracheal diameter + 10%) were analyzed using a linear mixed model. CT tracheal lumen diameters were larger compared to fluoroscopy at all locations (P‐value < 0.0001). When comparing modalities, fluoroscopic and CT stent sizes were statistically different. Greater overall variation in tracheal diameter measurement (height or width) existed for fluoroscopy compared to CT, both within and among observers. The greater tracheal diameter measured with CT and lower measurement variability has clinical significance, as this may be the imaging modality of choice for appropriate stent selection to minimize complications in veterinary patients.     

EFFECTS OF SEDATION WITH MIDAZOLAM AND BUTORPHANOL ON RESISTIVE AND PULSATILITY INDICES IN HEALTHY DOGS

Resistive index (RI) and pulsatility index (PI) are indirect measurements of blood flow resistance that may be measured by pulsed wave Doppler ultrasonography. Chemical restrain may potentially alter the indices although it is required to perform ultrasonography in some patients. The purpose of this study was to describe values for both intrarenal and ocular RI and PI within the same subject in clinically normal dogs sedated with a midazolam and butorphanol combination and evaluate if there are any significant changes between sedated and nonsedated dogs. Fifteen healthy Beagle dogs were studied by Duplex Doppler interrogation in interlobar or arcuate arteries of the kidney and long posterior ciliary artery. Pulse rate and systolic blood pressure were also determined. All measurements were recorded before and after the administration of a sedative combination of midazolam (0.2 mg/kg) and butorphanol (0.2 mg/kg). Mean comparison tests (paired t-tests or Wilcoxon's rank-sum test) were used to determine if any significant differences existed between right and left renal values or right and left ocular values. A correlation study (Pearson or Spearman) was applied between RI, PI, and systolic pressure, and pulse rate. RI and PI were significantly higher in sedated Beagles than in unsedated Beagles. There was neither correlation between index and systolic blood pressure nor pulse rate. In conclusion, provided that normal RI and PI increase in sedated animals, then reference ranges should be higher when sedated--healthy or ill--animals are evaluated.     

QUANTITATIVE VIDEOFLUOROSCOPIC EVALUATION OF PHARYNGEAL FUNCTION IN THE DOG

Videofluoroscopic evaluation of both liquid barium and barium soaked kibble was performed in 11 adult, clinically normal dogs of varying breeds. Each examination was digitized and evaluated frame by frame to establish the normal timing sequence of the pharyngeal phase of swallowing. Closure of the epiglottis was considered the onset of swallowing. The time to each of the following events was recorded: (1) Maximum pharyngeal contraction, (2) Opening of the epiglottis, (3) Opening of the cranial esophageal sphincter, and (4) Closure of the cranial esophageal sphincter. These values were found to be consistent both intra and interpatient. Retrospective analysis of 3 videofluoroscopic examinations from dogs that met the subjective criteria defining cricopharyngeal achalasia was then performed. A statistically significant delay in the time to opening and closure of the cranial esophageal sphincter was found employing both liquid barium and barium soaked kibble in the dogs with cricopharyngeal achalasia.     

IOHEXOL PLASMA CLEARANCE IN HEALTHY DOGS AND CATS

Iohexol plasma clearance as a measure of glomerular filtration was determined in 31 dogs and 19 cats after an intravenous (i.v.) bolus injection. All animals were healthy and privately owned. Serial blood samples were taken before and up to 4 h after tracer injection. Iohexol plasma concentration was determined using X-ray fluorescence. A plasma tracer elimination curve was generated and clearance was calculated by dividing the injected dose by the area under the curve estimated using a two-compartment pharmacological model. Clearance was normalized to body weight (BW), body surface area (BSA), and extracellular fluid volume (ECFV). Mean, SD, and coefficient of variation of plasma clearance, before and after normalization, were calculated. Linear regression analyses were performed between body size and normalized plasma clearances. No significant linear relation was found between BSA and clearance normalized to BSA in dogs, and between BSA, BW, ECFV and clearance normalized to BSA, BW, and ECFV in cats. The optimal method for normalization of iohexol plasma clearance in dogs was by using BSA. In cats, all three methods tested were considered satisfactory. Normalization to BSA appears to be superior to normalization to BW and ECFV in dogs, and can be recommended for clinical use.     

ULTRASONOGRAPHIC CHARACTERISTICS OF THE ABDOMINAL ESOPHAGUS AND CARDIA IN DOGS

Differential diagnoses for regurgitation and vomiting in dogs include diseases of the gastroesophageal junction. The purpose of this cross‐sectional study was to describe ultrasonographic characteristics of the abdominal esophagus and gastric cardia in normal dogs and dogs with clinical disease involving this region. A total of 126 dogs with no clinical signs of gastrointestinal disease and six dogs with clinical diseases involving the gastroesophageal junction were included. For seven euthanized dogs, ultrasonographic features were also compared with gross pathology and histopathology. Cardial and abdominal esophageal wall thicknesses were measured ultrasonographically for all normal dogs and effects of weight, sex, age, and stomach filling were tested. Five layers could be identified in normal esophageal and cardial walls. The inner esophageal layer was echogenic, corresponding to the cornified mucosa and glandular portion of the submucosa. The cardia was characterized by a thick muscularis, and a transitional zone between echogenic esophageal and hypoechoic gastric mucosal layers. Mean (±SD) cardial wall thicknesses for normal dogs were 7.6 mm (±1.6), 9.7 mm (±1.8), 10.8 mm (±1.6), 13.3 mm (±2.5) for dogs in the <10 kg, 10–19.9 kg, 20–29.9 kg and ≥30 kg weight groups, respectively. Mean (±SD) esophageal wall thicknesses were: 4.1 mm (±0.6), 5.1 mm (±1.3), 5.6 mm (±1), and 6.4 mm (±1.1) for the same weight groups, respectively. Measurements of wall thickness were significantly correlated with dog weight group. Ultrasonography assisted diagnosis in all six clinically affected dogs. Findings supported the use of transabdominal ultrasonography as a diagnostic test for dogs with suspected gastroesophageal disease.     

CONTRAST‐ENHANCED ULTRASONOGRAPHY OF THE PANCREAS IN HEALTHY DOGS AND IN DOGS WITH ACUTE PANCREATITIS

Pancreatitis is the most frequent disease affecting the exocrine pancreas in dogs and reliable diagnostic techniques for predicting fatal complications are lacking. Contrast‐enhanced ultrasound (CEUS) improves detection of tissue perfusion as well as organ lesion vascular pattern. Objectives of this prospective case control study were to compare perfusion characteristics and enhancement patterns of the pancreas in healthy dogs and dogs with pancreatitis using CEUS. Ten healthy dogs and eight dogs with pancreatitis were selected based on physical examination, abdominal ultrasound, and blood analysis findings. A CEUS study of the pancreas was performed for each dog and two observers who were aware of clinical status used advanced ultrasound quantification software to analyze time‐intensity curves. Perfusion patterns were compared between healthy and affected dogs. In dogs with acute pancreatitis, mean pixel and peak intensity of the pancreatic parenchyma was significantly higher than that of normal dogs (P = 0.05) in between 6 and 60 s (P = <0.0001–0.046). This corresponds to a 311% increase in mean pixel intensity in dogs with acute pancreatitis compared to healthy dogs. Wash‐in rates were greater and had a consistently steeper slope to peak in dogs with pancreatitis as opposed to healthy dogs. All dogs with pancreatitis showed a decrease in pixel intensity 10–15 days after the initial examination (P = 0.011) and their times to peak values were prolonged compared to the initial exam. Findings from the current study supported the use of CEUS for diagnosing pancreatitis, pancreatic necrosis, and disease monitoring following therapy in dogs.     

EFFECTS OF INTRAVENOUS DEXMEDETOMIDINE ON CARDIAC CHARACTERISTICS MEASURED USING RADIOGRAPHY AND ECHOCARDIOGRAPHY IN SIX HEALTHY DOGS

Dexmedetomidine is a highly specific and selective α2‐adrenergic receptor agonist widely used in dogs for sedation or analgesia. We hypothesized that dexmedetomidine may cause significant changes in radiographic and echocardiographic measurements. The objective of this prospective cross‐sectional study was to test this hypothesis in a sample of six healthy dogs. Staff‐owned dogs were recruited and received a single dose of dexmedetomidine 250 μg/m² intravenously. Thoracic radiography and echocardiography were performed 1 h before treatment, and repeated 10 and 30 min after treatment, respectively. One observer recorded cardiac measurements from radiographs and another observer recorded echocardiographic measurements. Vertebral heart score and cardiac size to thorax ratio on the ventrodorsal projection increased from 9.8 ± 0.6 v to 10.3 ± 0.7 v (P = 0.0007) and 0.61 ± 0.04 to 0.68 ± 0.03 (P = 0.0109), respectively. E point‐to‐septal separation and left ventricle internal diameter in diastole and systole increased from 2.4 ± 1.1 to 6.6 ± 1.9 mm, 32.3 ± 8.1 to 35.5 ± 8.8 mm, and 19.4 ± 6 to 27.0 ± 7.2 mm, respectively (P < 0.05). Fractional shortening and sphericity index decreased from 40.7 ± 5.8 to 24.4 ± 2.9%, and 1.81 ± 0.07 to 1.58 ± 0.04, respectively (P < 0.05). Moderate‐to‐severe mitral regurgitation and mild pulmonic regurgitation occurred in all dogs after dexmedetomidine administration. Findings indicated that dexmedetomidine could cause false‐positive diagnoses of valvular regurgitation and cardiomegaly in dogs undergoing thoracic radiography and echocardiography.     

EFFECT OF METHYLCELLULOSE ON UPPER GASTROINTESTINAL QUALITY IN DOGS

This study was performed to evaluate and optimize a small bowel contrast technique using barium and methylcellulose in dogs. Ten healthy dogs underwent both a conventional upper gastrointestinal study that used only barium and a modified study that used barium and methylcellulose. The control group received 10 mL/kg of 40% barium suspension. Experimental groups were divided into three subgroups given 15 mL/kg of different viscosities (low, moderate, and high viscosity) of 0.5% methylcellulose after 4 mL/kg of 40% barium suspension. Compared with the control group, dogs receiving methylcellulose had higher-quality upper gastrointestinal studies. Moderate viscosity of methylcellulose was superior to the other methylcellulose groups. In conclusion, the use of methylcellulose is a simple and effective method for improving the image quality in an upper GI examination.     

EFFECT OF ANISOTROPY AND SPATIAL COMPOUND IMAGING ON RENAL CORTICAL ECHOGENICITY IN DOGS

The echogenicity of the renal cortex is an important parameter to consider in dogs that are suspected to have renal dysfunction. Focal increases in echogenicity have been attributed to neoplasia, infection, calcification, fibrosis, gas, and infarction. Anisotropic backscatter has been described as a source of focally increased renal cortical echogenicity in several species. The source of anisotropy appears to be the medullary rays, which are oriented perpendicular to the renal capsule. Spatial compound imaging (SCI) is an ultrasound setting that uses beam steering to acquire and average several overlapping scans of an object from different view angles, creating a compound image that is updated in real time. The impact of insonation angle and SCI on renal cortical echogenicity was evaluated ex vivo in eight kidneys from four dogs. Significant angle‐dependent differences in cortical echogenicity were detected with both microconvex and linear transducers (P < 0.0001). Furthermore, the angle‐dependent echogenicity differences persisted when SCI mode was used. Our finding that echogenicity was increased using a perpendicular insonation angle (90°) relative to the tubules, compared to a parallel insonation angle (0°) should assist in the interpretation of ultrasonographic images of the dog kidney.     

COMPARISON OF THE EFFECT OF LAPAROSCOPIC AND CONVENTIONAL PYLORIC SURGERY ON GASTRIC EMPTYING IN DOGS

The effect of a laparoscopic approach and pyloric surgery on canine gastrointestinal activity, particularly gastric emptying time, is not well understood. The purpose of this study was to compare the effect of laparoscopic and conventional pyloric surgery, in Ramstedt pyloromyotomy and Heineke-Mikulicz pyloroplasty, on complete gastric emptying time in 20 clinically normal dogs. Dogs were divided into four groups of five animals: dogs with laparoscopic Ramstedt pyloromyotomy, conventional Ramstedt pyloromyotomy, or laparoscopic Heineke-Mikulicz pyloroplasty, and the conventional Heineke-Mikulicz pyloroplasty group. Gastric emptying time using barium sulfate mixed with dry kibble dog food was measured fluoroscopically before and 1 month after surgery. Gastric emptying of solids was significantly enhanced in the pyloroplasty groups in the postoperative period compared with preoperative emptying. Just as after conventional pyloromyotomy, gastric emptying time after laparoscopic pyloromyotomy was not statistically different as compared with preoperative values. This study indicates that the fluoroscopic test meal is a valuable tool for defining complete gastric emptying time in normal dogs. We conclude that pyloromyotomy was less effective in decreasing complete gastric emptying time than Heineke-Mikulicz pyloroplasty in normal dogs. The possibility of decreasing complete gastric emptying time by laparoscopic surgery suggests a potential clinical application for this technique in small animals.     

MEASUREMENTS OF THE PULMONARY VASCULATURE ON THORACIC RADIOGRAPHS IN HEALTHY DOGS COMPARED TO DOGS WITH MITRAL REGURGITATION

This study reassessed the previously reported radiographic method of comparing pulmonary vessels versus rib diameter for differentiating healthy dogs and dogs with mitral regurgitation. The width of the right cranial pulmonary artery and vein at the fourth rib level, right caudal pulmonary artery and vein at the ninth rib level, and the diameters of the fourth rib and ninth rib were measured in prospectively recruited healthy dogs (n = 40) and retrospectively recruited dogs with mitral regurgitation (n = 58). In healthy dogs, the pulmonary arteries and accompanying veins were similar in size. The cranial lobar vessels were smaller than the fourth rib. However, 67.5% of right caudal pulmonary artery diameters and 65% of vein diameters were larger than the ninth rib in healthy dogs. The right caudal pulmonary vein diameter in dogs with mitral regurgitation, particularly those within moderate and severe grades, was significantly larger than that in healthy dogs (P < 0.001). The comparative method used to detect enlargement of the right caudal pulmonary vein relative to the accompanying pulmonary artery had the highest sensitivity (80.2%) and specificity (82.5%) for predicting mitral regurgitation. A cut‐off of 1.22 when applying the ninth rib criterion had better specificity (73%) than the most used value ≤ 1 (89.7% sensitivity and 63.8% specificity), although it has less sensitivity (73%). We recommend using the accompanying pulmonary artery and 1.22 × the diameter of the ninth rib as a radiographic criterion for assessing the size of the right caudal pulmonary vein and differentiating healthy dogs from those with mitral regurgitation.     

CYSTOGRAPHY: EFFECT OF TECHNIQUE ON DIAGNOSIS OF CYSTITIS IN DOGS

Double-constrast and positive-contrast cystograms were performed in 12 dogs. After cystography, E. coli cystitis was induced in nine of the 12 dogs. The remaining three dogs were used as controls. Double contrast and positive-contrast cystograms were repeated threee, seven and 14 days later. During cystography, bladders were distended to mild, moderate, and complete degrees of distention. Mucosal irregularity decreased with increasing bladder distention and was more likely to be seen on double-contrast than on the positive-contrast cystogram. When seen on both types of studies, mucosal irregularity was more obvious on double-contrast than it was on the positive-contrast custogram. Bladder wall thickness decreased with increasing distention; in some dogs with mild cystitis, abnormal wall thickness was masked by complete bladder distention. Bladder wall thickness could be measured more often on double-contrast than on the positive contrast cystograms. Wall thickness measurments made on both types of studies were similar. It was concluded that lesions of mild to moderate cystitis may be missed when the bladder is completely distended, and that the double-contrast cystogram is more sensetive for evaluating mucosal margivation and bladder wall thickness than is the positive-contrast cystogram     

ULTRASONOGRAPHIC EVALUATION OF THE PROSTATE IN HEALTHY INTACT DOGS

Sagittal and transverse ultrasonographic images of the prostate gland were obtained in 100 healthy adult intact male dogs. Prostatic length, width, and height on transverse and sagittal images as well as the presence of prostatic cysts were determined. Linear regression and correlation analysis were performed between prostatic parameters (length, width, height on sagittal and transverse images, and estimated volume) and parameters related to body size (body weight, body height, left kidney length and aortic diameter) and age of the dogs. Significant positive correlations were found between all prostatic parameters and parameters related to body size and age. Maximum predicted values for prostatic parameters for a given body weight and age were determined based on the upper limit of the 95% confidence interval of the mean predicted values. Such values should represent a useful tool for ultrasonographic evaluation of the prostate in the dog. Prostatic cysts were found in 14% of the dogs.     

GASTRIC EMPTYING OF SOLID RADIOPAQUE MARKERS IN HEALTHY DOGS

The gastric emptying of 1.5 mm diameter (small) and 5.0 mm diameter (large) radiopaque markers (BIPS) was assessed in 20 dogs. The markers were fed to the dogs in a test meal and abdominal radiographs were made hourly thereafter. Studies were repeated three times in each dog. The variation between two veterinarians interpreting the radiographs was low. The sex, age and day of the study did not have a significant effect on the lag phase or the time taken to empty 25%, 50% and 75% of the markers (T₂₅, T₅₀ and T₇₅ respectively). There was a weak but significant positive correlation between the body weight and T₅₀. There was no significant difference in gastric emptying parameters between the large and small markers.
The mean gastric emptying versus time curve of the small markers on day one was chosen to represent the reference curve for healthy dogs. The lag phase of the small markers on day one was 2.45 ± 2.04 hours, the T₂₅ was 4.85 ± 2.15 hours, the T₅₀ was 6.05 ± 2.99 hours and the T₇₅ was 8.32 ± 2.72 hours (mean ± SD).