CONTRAST‐ENHANCED ULTRASOUND OF THE NORMAL CANINE PROSTATE GLAND

Canine prostate gland abnormalities affect a large number of adult male dogs. In veterinary medicine, the commonly used methods to diagnose canine prostate gland disease are digital rectal examination and abdominal ultrasound. We evaluated the ability of ultrasound contrast agent to provide additional information about the vascularity of the canine prostate gland; such information could be useful in detecting early prostate gland disease and in staging disease known to be present. We characterized the ultrasonographic appearance of prostate gland vascularity in 10 healthy dogs before and after the injection of an ultrasound contrast agent (Levovist^?). Before injecting Levovist^?, the prostate gland blood flow was classified as poor in all dogs, whereas after contrast agent injection blood flow was classified as moderate or good, in 3 and 7 dogs respectively. Knowledge of the status of prostate gland vascularity could be useful for the characterization, diagnosis and therapeutic monitoring of canine prostate gland lesions.     

COLOR DOPPLER AND DOPPLER SPECTRAL ANALYSIS IN THE SPINAL CORD OF NORMAL DOGS

Doppler ultrasonography of the spinal cord was performed in 34 normal, anesthetized dogs following hemilaminectomy. This study was part of an investigation to evaluate the efficacy of a 21-aminosteroid compound and high dose methylprednisolone for the treatment of spinal cord trauma. Grey-scale images of the canine spinal cord were similar to those described for the spinal cord of people. Doppler waveforms of intraparenchymal spinal arteries exhibited high end diastolic blood flow velocities, indicating low resistance to flow. Doppler values (mean ± SD) for arteries immediately ventrolateral to the central canal were: Peak Systolic Velocity = 5.78 ± 2.5 cm/sec, Minimum Diastolic Velocity = 3.5 ± 1.62 cm/sec, Mean Velocity = 4.45 ± 1.96 cm/sec, Minimum Diastolic Velocity = 3.5 ± 1.62 cm/sec, Mean Velocity = 4.45 ± 1.96 cm/sec, Systolic/Diastolic ratio = 169 ± 0.19, Pulsatility Index = 0.53 ± 0.09, and Resistance Index = 0.4 ± 0.06.     

CHARACTERIZATION OF LYMPHOMATOUS LYMPH NODES IN DOGS USING CONTRAST HARMONIC AND POWER DOPPLER ULTRASOUND

Doppler ultrasound has been used in humans to determine angioarchitecture of lymph nodes as the criterion for the determination of malignancy. We hypothesized that the vascular and perfusion patterns of a canine malignant lymph node could be characterized with intravenous microbubble ultrasound contrast media and that contrast harmonic ultrasound could provide better conspicuity of the angioarchitecture when compared with Power Doppler ultrasound. In this study, 11 peripheral lymph nodes in dogs with histologically verified malignant lymphoma were imaged with fundamental ultrasound, Power Doppler ultrasound, and three contrast harmonic pulse sequences to characterize the vascular pattern and perfusion. Vascular imaging was greatly enhanced in these nodes with 2.13 times more vessels seen with contrast harmonic ultrasound compared with Power Doppler ultrasound (P < 0.01). The angioarchitecture of lymphomatous lymph nodes of dogs in this study were similar to those previously described in malignant superficial lymph nodes in human patients; 45.5% of the nodes had displacement of the central hilar vessel, 45.5% had aberrant vessels, 63.6% had pericapsular vessels, 36.4% had subcapsular vessels, and 81.8% had loss of the central hyperechoic band in fundamental sonography. Poor perfusion, indicated by a lower mean pixel intensity increase between pre- and postcontrast administration images, was seen in 36.4% of the lymph nodes while 63.6% had fair to good perfusion. The perfusion patterns in nine of the 11 lymph nodes were homogenous and two showed focal hypoperfused regions. We conclude that Power Doppler and contrast harmonic ultrasound are beneficial in accurately depicting angioarchitechture and can provide additional information in determining the presence of malignant vascular characteristics within lymphomatous nodes in dogs.     

QUANTITATIVE CONTRAST ULTRASOUND ANALYSIS OF RENAL PERFUSION IN NORMAL DOGS

Eight normal dogs with no evidence of renal disease, weighing between 8 and 25 kg were imaged using contrast harmonic ultrasound after injection of a microbubble contrast medium. All dogs received three separate bolus injections of 0.05 ml of commercial contrast medium (Definity). Time/mean pixel value (MPV) curves were generated for selected regions in the cortex and medulla of the left kidney in each dog. Upslope, downslope, baseline, peak intensity, and time to peak were calculated for each zone. For a bolus injection, within the renal cortex (averaging all subjects) the upslope was 7.4 +/- 1.5 MPV/s, downslope was -0.4 +/- .2 MPV/s, baseline was 66.8 +/- 9.3 MPV, peak was 103.6 +/- 8.2 MPV, time to peak (from injection) was 12.8 +/- 5.3 s and from time of contrast medium reaching the kidney was 5.1 +/- 2.0 s. Within the renal medulla (averaging all subjects), upslope was 2.8 +/- 1.7 MPV/s, downslope was -0.3 +/- .2 MPV/s, baseline was 39.3 +/- 6.0 MPV, peak was 65.2 +/- 14.3 MPV, time to peak from injection was 20.9 +/- 6.4 s and from time of contrast reaching the kidney was 11.6 +/- 4.1 s. These baseline data may prove useful in the evaluation of dogs with diffuse disease or vascular compromise.     

ULTRASOUND EVALUATION OF SMALL BOWEL THICKNESS COMPARED TO WEIGHT IN NORMAL DOGS

The use of ultrasound to measure small bowel thickness is an important part of any ultrasound examination of the abdomen. Increased thickness of the intestinal wall is a hallmark for the detection of diseases ranging from inflammatory bowel disease to neoplasia. Our subjective impression has been that dogs with no clinical signs of gastrointestinal disease often have sonographic measurements greater than published norms. The purpose of this study was to prospectively reevaluate these norms. The clinical history on all dogs receiving an abdominal ultrasound examination was evaluated for signs of gastrointestinal disease. Those without clinical signs were entered into this study. The documentation of body weight, breed, jejunal thickness, and duodenal thickness was made in 231 dogs. Dogs were placed into five groups based on their weight. Sixty-nine breeds were represented with weight ranging from 2.1 to 64 kg. A statistically significant (P < or = 0.05) correlation between body weight and both jejunal and duodenal thickness was observed. We also found that the maximum thickness in both jejunum and duodenum in healthy dogs was larger than previously reported. These data indicate norms for the jejunum of < or = 4.1 mm for dogs up to 20 kg, < or = 4.4 mm for dogs between 20 and 39.9 kg, and < or = 4.7 mm for dogs over 40 kg. The data indicate norms for the duodenum < or = 5.1 mm for dogs up to 20 kg, < or = 5.3 kg for dogs between 20 and 29.9 kg, and < or = 6.0 mm for dogs over 30 kg.     

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.     

DOPPLER ULTRASONOGRAPHIC ESTIMATION OF RENAL AND OCULAR RESISTIVE AND PULSATILITY INDICES IN NORMAL DOGS AND CATS

Resistive index (RI) and pulsatility index (PI) are indirect measurements of blood flow resistance that may be used to evaluate vascular changes in renal and ophthalmologic diseases. To our knowledge, no reports are available describing values for renal and ocular PI index in the unsedated dog and ocular RI and PI indices in the unsedated cat. The purpose of this study was to measure normal values for both intrarenal and ocular RI and PI within the same subject in unsedated clinically normal dogs and cats. Twenty-seven dogs and 10 cats were considered healthy by means of physical examination, CBC, biochemical profile, urinalysis, and ultrasonography. Systolic blood pressure was measured by Doppler ultrasonography. Intrarenal and ocular arteries were scanned by pulsed Doppler ultrasonography to calculate RI and PI. No significant differences were noted between the values obtained for the right vs. the left kidney and eye. The upper values of these indices were calculated as mean+2 standard deviations resulting in 0.72 and 1.52 for dog renal RI and PI; 0.7 and 1.29 for cat renal RI and PI; 0.76 and 1.68 for dog ocular RI and PI; and 0.72 and 1.02 for cat ocular RI and PI.     

NORMAL DUPLEX DOPPLER WAVEFORMS OF MAJOR ABDOMINAL BLOOD VESSELS IN DOGS: A REVIEW

The normal flow velocity profile and duplex Doppler waveform of the major abdominal blood vessels (aorta, caudal vena cava and the portal vein as well as their major branches) were examined by Doppler ultrasound. The flow velocity profile of an artery is largely determined by its diameter. The pulsatility of the waveform is related to the vascular impedance downstream to the point of measurement. Early systolic peak is present in the Doppler pattern of some vessels in some dogs. The waveform of the veins is mainly affected by the pressure conditions of the right atrium and the intrathoracic and intraabdominal pressure changes due to the respiration. Simultaneous electrocardiogram was used to reveal the effect of the heart beats on the Doppler patterns of the veins.     

DOPPLER MEASUREMENT OF SPLANCHNIC BLOOD FLOW DURING DIGESTION IN UNSEDATED NORMAL DOGS

The purpose of this study was to measure splanchnic blood flow during digestion in unsedated dogs by using duplex Doppler sonography. The study population consisted of 12 healthy dogs. Blood flow in the cranial mesenteric artery, the celiac artery, and the aorta was measured before a test meal and at 20, 60, and 90 minutes after eating. The following measurements were made or calculated: vessel diameter, peak systolic velocity, end diastolic velocity, mean velocity, resistive index, pulsatility index, and flow volume. There was a significant postprandial decrease in the resistive and pulsatility indices in both the cranial mesenteric (preprandial RI = 0.867, postprandial RI = 0.796, preprandial PI = 3.033, postprandial PI = 2.173) and the celiac (preprandial RI = 0.854, postprandial RI = 0.769, preprandial PI = 2.639, postprandial PI = 1.930) arteries. In both vessels the end diastolic velocity, the mean velocity, and the flow volume increased significantly postprandially. These changes occurred significantly earlier in the celiac artery than in the cranial mesenteric artery. The findings most likely correspond to postprandial splanchnic vasodilation. Doppler ultrasound provide a good methode of detecting changes in postprandial splanchnic blood flow in the dog.     

ULTRASONOGRAPHIC APPEARANCE OF THE INTRAVASCULAR TRANSIT OF AGITATED SALINE IN NORMAL DOGS FOLLOWING ULTRASOUND GUIDED PERCUTANEOUS SPLENIC INJECTION

Portosystemic shunts (PSSs) allow portal blood to bypass the liver and enter the systemic circulation. Definitive diagnosis requires surgical identification, positive contrast portography, ultrasonography, or scintigraphy. This study was designed as a preliminary step to developing an alternative/adjuvant protocol to these imaging modalities. The main goals were to establish a technique for ultrasound‐guided percutaneous trans‐splenic injection of agitated saline, to evaluate the feasibility of performing the test to explore the postsplenic portal vasculature highlighted by the microbubbles, and to ascertain whether agitated saline microbubbles cross the sinusoidal barrier. Agitated saline was injected into the spleen of 20 healthy sedated dogs under sonographic guidance. The transducer was then repositioned to visualize the portal vein, the caudal vena cava, and the right atrium through different acoustic windows. Satisfactory results were achieved in all dogs. The microbubbles were visualized in all dogs as small intense echo signals within the portal vein at the level of the porta hepatis immediately after injection. In 18 out of 20 dogs, the echogenic signal of the microbubbles disappeared immediately once within the hepatic parenchyma, whereas in two dogs, the echoes from the microbubbles lasted for several seconds within the intrahepatic portal vasculature. The absence of microbubbles beyond the sinusoidal barrier in all of the healthy dogs included in this study makes trans‐splenic injection of agitated saline a candidate as an adjuvant technique for the diagnosis of PSS, being easy to perform and repeat, as well as safe and technically feasible.     

MICRONODULAR ULTRASOUND LESIONS IN THE COLONIC SUBMUCOSA OF 42 DOGS AND 14 CATS

Micronodular ultrasound lesions have been detected in the colonic submucosa of dogs and cats at our hospital. The lesions had rounded/oval shapes, measured 1–3 mm in size, and exhibited a hypo/anechoic ultrasonographic pattern. To our knowledge, these lesions have not been previously reported in human or veterinary patients. The purpose of this retrospective study was to determine whether micronodular lesions were associated with other abdominal ultrasound abnormalities or clinical findings. Medical records of dogs and cats with sonographic reports describing micronodular lesions within the colonic submucosa were reviewed. Concurrent ultrasonographic abnormalities were recorded and compared with clinical sidgns and follow‐up data. A total of 42 dogs and 14 cats met inclusion criteria. Concurrent sonographic abnormalities included the following: increased colon wall thickness (12.5%); small bowel wall thickening, altered layering, and/or hyperechoic mucosa (45%); abdominal effusion (29%); caudal mesenteric lymphadenopathy (46%); mesenteric lymphadenopathy (27%); and pericolic peritoneal fat reactivity (9%). Fifty of 56 animals presented with diarrhea. Twenty‐seven cases had clinical signs of colitis and ultrasonographic lesions were limited to the colonic submucosa. In nine cases, follow‐up examination at 6–8 weeks showed resolution of clinical and ultrasonographic signs. Ultrasonographic and clinical examinations in 17 patients at 12–18 months and in 20 patients at 18–30 months from initial diagnosis showed resolution of submucosal lesions and clinical signs of enteropathy. The authors propose that micronodular submucosal ultrasound lesions may represent reactive intraparietal lymphoid follicles and may be indicators of colonic inflammatory diseases in dogs and cats.     

ULTRASONOGRAPHIC ELASTOGRAPHY OF THE LIVER,SPLEEN, KIDNEYS,AND PROSTATE IN CLINICALLY NORMAL BEAGLE DOGS

Standard ultrasonography is often insensitive for distinguishing normal vs. diseased states for canine abdominal organs. Ultrasonographic elastography is a new technique that is becoming increasingly available and may help to improve sensitivity. This study evaluated the feasibility, repeatability, and reproducibility of strain elastography of the liver, spleen, kidneys, and prostate in healthy dogs and described the elasticity of each organ using strain values and strain ratios. The reproducibility of strain elastography was excellent, and intraobserver repeatability was moderate to excellent. The strain value of each organ was not significantly different among dogs (liver = 143.38 ± 7.41, spleen = 141.04 ± 9.03, left renal cortex = 141.26 ± 7.50, right renal cortex = 145.80 ± 7.79, and prostate = 135.46 ± 5.80), except for the renal medulla (left = 51.19 ± 4.54 and right = 51.93 ± 5.09) (P < 0.05). The strain ratios for the liver, spleen, renal cortex, and prostate were similar with no significant difference (liver = 10.20 ± 1.47, spleen = 8.40 ± 1.53, left renal cortex = 9.62 ± 1.56, right renal cortex = 8.29 ± 1.63, and prostate = 8.20 ± 1.21), except for the renal medulla (left = 3.48 ± 0.68 and right = 2.95 ± 0.63) (P < 0.05). Our results indicated that strain elastography was feasible for estimating tissue stiffness in the canine liver, spleen, kidneys, and prostate. This study provides basic information for strain values and strain ratios for the liver, spleen, kidneys, and prostate in clinically normal dogs.     

COLOR FLOW DOPPLER IMAGING AND DOPPLER SPECTRAL ANALYSIS OF THE BRAIN OF NEONATAL DOGS

Doppler ultrasonography was performed on the cerebral arteries o f 19 neontal dogs.Vascular structures were identified using anatomic preparations of brains pre-injected with a radiopaque silicone rubber product and cleared using a modified tissue clearing technique. Brain sections were subsequently radiographed of examined under a steromicroscope. Color flow Doppler imagin was used to facilitate positioning of the Doppler calipers for measurement of peak systolic velocity, minimum diastolic velocity, and resistance index. Blood flow velocities in the internal carotid and middle cerebral arteries were lower when measured intransvere images than in sagittal images. The rostral cerebral arteries could be measured using either plane but values obtained from different locations or using different methods of measurement were statistically different. Blood flow velocities generally increased during the first month after birth. Arterial signals were diphasic with flow throughout diastole. Resistance indices most often were between 0.6 and 0.7 and did not exceed 0.86.     

IMPROVED DETECTION OF METASTATIC HEPATIC HEMANGIOSARCOMA NODULES WITH CONTRAST ULTRASOUND IN THREE DOGS

Three dogs with a splenic hemangiosarcoma were imaged with conventional gray-scale ultrasound and no lesions were identified in the liver. After administration of intravenous ultrasound contrast medium (Definity) small, poorly enhanced, hypoechoic nodules were identified in the liver in each dog. The spleen and liver lesions were identified at surgery and the dogs underwent splenectomy and nodule biopsy. All lesions were identified histologically as hemangiosarcoma. These preliminary results suggest that contrast ultrasound may result in improved detectability of metastatic hepatic hemangiosarcoma.     

DOPPLER MEASUREMENT OF HEPATIC ARTERIAL FLOW IN DOGS: TECHNIQUE AND PRELIMINARY FINDINGS

The common hepatic artery in 10 healthy adult beagles, 20 healthy pups (13 Deerhounds and seven Irish Wolfhounds), and seven dogs with either a congenital or acquired hepatic disorder was examined by duplex-Doppler ultrasonography. Peak systolic velocity (Vs), resistive index (RI), pulse rate, angle of insonation, and sample volume depth were recorded. Measurements in Beagles were made after a 24 h fast and repeated 2 h after feeding. The mean Vs and RI in fasted Beagles were 1.5 m/s (range 1.1-2.3 m/s) and 0.68 (range 0.62-0.74), respectively. Postprandially, there were no significant differences in any of these variables. Mean Vs and RI were lower in pups: 1.0 m/s (range 0.8-1.3 m/s) and 0.59 (range 0.46-0.65), respectively (P < .001). Two dogs with congenital arterioportal fistula had higher mean Vs (P < .001) and lower mean RI (P < .05) than normal pups. No significant differences were detected between normal Beagles, three dogs with portal vein thrombosis, and two dogs with acquired hepatic insufficiency. Differences in measured hepatic blood flow in dogs of different age or breed will complicate diagnostic use of hepatic arterial Doppler measurements.     

EVALUATION OF EXPERIMENTALLY INDUCED CANINE HEPATIC CIRRHOSIS USING DUPLEX DOPPLER ULTRASOUND

Portal blood flow was measured with duplex Doppler ultrasound in ten normal dogs and in ten dogs with hepatic cirrhosis induced by common bile duct ligation 4 weeks previously. Mean portal blood flow velocity in the 10 dogs with experimentally induced hepatic cirrhosis was markedly reduced (9.2 ± 1.70 cm/sec vs. normal 18.1 ± 7.6 cm/sec, p < 0.01). Mean portal blood flow was also significantly decreased compared to normal (17.2 ± 4.9 cc/min/kg versus normal 31.06 ± 9.1 cc/min/kg, p < 0.01) while portal vein diameter remained unchanged. The dogs with induced hepatic cirrhosis developed extensive extrahepatic portosystemic shunting that was confirmed at necropsy. It was concluded that decreased portal velocity and portal flow which resulted from hepatic cirrhosis was detectable noninvasively with Doppler ultrasound.     

TRANSTHORACIC LUNG ULTRASOUND IN NORMAL DOGS AND DOGS WITH CARDIOGENIC PULMONARY EDEMA: A PILOT STUDY

Pulmonary edema is the most common complication of left‐sided heart failure in dogs and early detection is important for effective clinical management. In people, pulmonary edema is commonly diagnosed based on transthoracic ultrasonography and detection of B line artifacts (vertical, narrow‐based, well‐defined hyperechoic rays arising from the pleural surface). The purpose of this study was to determine whether B line artifacts could also be useful diagnostic predictors for cardiogenic pulmonary edema in dogs. Thirty‐one normal dogs and nine dogs with cardiogenic pulmonary edema were prospectively recruited. For each dog, presence or absence of cardiogenic pulmonary edema was based on physical examination, heartworm testing, thoracic radiographs, and echocardiography. A single observer performed transthoracic ultrasonography in all dogs and recorded video clips and still images for each of four quadrants in each hemithorax. Distribution, sonographic characteristics, and number of B lines per thoracic quadrant were determined and compared between groups. B lines were detected in 31% of normal dogs (mean 0.9 ± 0.3 SD per dog) and 100% of dogs with cardiogenic pulmonary edema (mean 6.2 ± 3.8 SD per dog). Artifacts were more numerous and widely distributed in dogs with congestive heart failure (P < 0.0001). In severe cases, B lines increased in number and became confluent. The locations of B line artifacts appeared consistent with locations of edema on radiographs. Findings from the current study supported the use of thoracic ultrasonography and detection of B lines as techniques for diagnosing cardiogenic pulmonary edema in dogs.     

DOPPLER ECHOCARDIOGRAPHY IN THE NORMAL DOG: PART I VELOCITY FINDINGS AND FLOW PATTERNS

This study examined the blood flow velocities and flow patterns in the normal dog using pulsed wave spectral Doppler echocardiography in eight areas of the heart. Two breeds of dogs, aged between 8 and 112 weeks and of both sexes, were used. The dogs were fully conscious and no drugs were used. The areas examined were the mitral valve, left atrium, tricuspid valve, right atrium, aorta, left ventricular outflow tract, pulmonary valve and the right ventricular outflow tract. The peak and mean velocities, direction of flow and whether flow was systolic or diastolic was determined for each of these flow areas. Additionally each of these waveforms were described. Aortic flow was also measured from the thoracic inlet by continuous wave Doppler.     

B-MODE AND DOPPLER ULTRASOUND IMAGING OF THE SPLEEN WITH CANINE SPLENIC TORSION: A RETROSPECTIVE EVALUATION

The ultrasonographic appearance of splenic torsion has been described; the splenic parenchyma can be normal, hypoechoic or anechoic with interspersed linear echoes (coarse/"lacy" appearance). The ultrasonographic parenchymal appearance of 15 dogs in this report with splenic torsion varied: mottled hypoechoic regions (n=2), diffusely hypoechoic (n=11) and normal (n=2). Because splenic torsion causes vascular congestion due to splenic vein compression and eventual thrombosis, visible splenic vein intraluminal echogenicities compatible with thrombi were seen in 13 dogs using B-mode. Using spectral Doppler and color Doppler imaging of the splenic veins, no measurable flow velocities were detected in any of the 15 dogs. The varied B-mode ultrasonographic appearance of the splenic veins for intraluminal echoes and spectral or color Doppler evaluation for absent velocity flow.     

COLOR DOPPLER ULTRASONOGRAPHY IN PREDICTION OF THE REDUCIBILITY OF INTUSSUSCEPTED BOWEL IN 15 YOUNG DOGS

Color Doppler ultrasonography was performed in 15 young dogs with intestinal intussusception to test the hypothesis that color Doppler findings can be used as a predictor of the manual reducibility of the intussusception at celiotomy. Color flow Doppler ultrasonography indicated blood flow within mesentery of the intussuscepted bowel in 12 of 15 dogs and reduction was achieved in nine of these 12 dogs (75%). In the remaining three dogs and in three dogs where no color Doppler signal were observed, an irreducible intussusception was confirmed at celiotomy. Color Doppler ultrasonography is a useful method for predicting the reducibility of intussusception in dogs.