CONTRAST HARMONIC ULTRASOUND APPEARANCE OF CONSECUTIVE PERCUTANEOUS RENAL BIOPSIES IN DOGS

Ultrasound‐guided percutaneous renal biopsy may be associated with complications, especially when using larger needles. Contrast harmonic ultrasound increases blood pool echo intensity, enhancing parenchymal lesions. Therefore, contrast harmonic ultrasound is a potential alternative screening method for postbiopsy renal lesions. Renal biopsies were performed using 14 G needles in 11 healthy Beagles, at three occasions: 0 (“Baseline Biopsy”; BB), 4 (“Biopsy 2”; B2), and 6 months (“Biopsy 3”; B3). Ultrasound and contrast harmonic ultrasound of biopsied kidneys were performed approximately 30 min after biopsy (week 0) at BB and B2, and repeated once every week (weeks 1–3) until normal appearance. At B3, only contrast harmonic ultrasound was performed, both immediately and 30‐min postbiopsy. Contrast harmonic ultrasound images were reviewed using subjective and semiquantitative methods to describe lesions including number, shape, size, sharpness, echogenicity, and evolution. More renal lesions were detected with contrast harmonic ultrasound (22/22) compared with conventional ultrasound (14/22). The majority appeared at week 0 as hypoechoic tract(s) (27/33), the other (6/33) as ill‐defined areas or area/tract combination, all having variable size, shape, and echogenicity. Seven tracts had a small subcapsular hematoma. In most kidneys, similar or gradual decrease of size and sharpness, and increased echogenicity was observed until normal appearance occurred at week 1 (1/22), week 2 (18/22), or week 3 (22/22). Two Beagles developed complications. At B3, immediately postbiopsy, tracts were hyperechoic in 9/11 kidneys, becoming hypoechoic again 30 min later. Contrast harmonic ultrasound is a valuable method to evaluate postbiopsy renal lesions in dogs.     

CHARACTERIZATION OF CANINE FOCAL LIVER LESIONS WITH CONTRAST-ENHANCED ULTRASOUND USING A NOVEL CONTRAST AGENT—SONAZOID

Contrast-enhanced ultrasound using Sonazoid, a novel contrast medium with a liver-specific Kupffer phase, was evaluated in canine focal liver lesions Twenty-five dogs with a liver mass were given intravenous Sonazoid, and the enhancement pattern in the arterial, portal, and parenchymal phase was characterized. An enhancement defect in the lesion in the parenchymal phase was observed in all malignant lesions, whereas only one of nine benign lesions had a filling defect. The diagnostic value of the presence of a filling defect for malignancy was statistically significant (100% sensitivity, 88.9% specificity, 94.1% positive predictive value, 100% negative predictive value), and was equal to that of hypoenhancement in the portal or delayed phase. The defect pattern (clear or irregular defect) was dependent ( P <0.05) on the types of malignancy (i.e., hepatocellular carcinoma and other types of malignancies). In the arterial phase, five of the six hepatocellular carcinomas had hypervascularity, whereas no other lesion was characterized by hypervascularity. In some dogs, additional lesions that could not be observed with conventional B-mode ultrasonography were detected in the parenchymal phase. The enhancement pattern of Sonazoid, especially in the parenchymal phase, has potential as a diagnostic tool for canine focal liver lesions.     

B‐MODE AND CONTRAST‐ENHANCED SONOGRAPHIC ASSESSMENT OF ACCESSORY SPLEEN IN THE DOG

Four dogs with an accessory spleen are described. The accessory spleens appeared as a round‐to‐triangular structure located in the perisplenic area. They were homogeneous and isoechoic with the adjacent spleen. Contrast‐enhanced ultrasound was performed using a second generation microbubble contrast medium (sulfur hexafluoride). The type and timing of enhancement of the accessory spleen was similar to that of the parent spleen. Contrast‐enhanced ultrasound is a noninvasive modality useful in distinguishing an accessory spleen from a mass of another origin.     

EFFECTS OF FASTING AND INTRALUMINAL CONTRAST ENHANCEMENT ON ULTRASONOGRAPHIC APPEARANCE OF THE EQUINE SMALL INTESTINE

The equine small intestine is challenging to evaluate ultrasonographically. In humans, hydrosonography has been used to improve ultrasonographic images of the small intestine. We hypothesized that fasting horses for 24 h would enhance the ability to image the small intestine transabdominally by separating intestinal loops and reducing intraluminal gas, and that the administration of intragastric contrast agent would further improve that ability. Ten healthy horses were examined ultrasonographically under three treatment conditions: (a) regular diet, (b) after a 24‐h fast, and (c) fasted plus intragastric administration of water and mineral oil. During each phase of the study, 30‐s video clips were obtained from four predetermined abdominal windows, and were examined to determine diagnostic quality. Fasting improved the ability to obtain high‐quality images of the small intestine significantly. The addition of contrast agent resulted in qualitative improvement in image quality, but differences did not result in statistically significant improvement.     

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.     

LESIONS OF THE RENAL PELVIS AND PROXIMAL URETER IN VARIOUS NEPHRO-UROLOGICAL CONDITIONS: AN ULTRASONOGRAPHIC STUDY

The applicability of ultrasonography was studied in the diagnosis of lesions of the renal pelvis and ureter in 10 dogs. Ultrasonographic findings of processes associated with dilatation and concretion formation in the renal pelvis were described and the differential diagnosis of the lesions was discussed. The authors propose a new classification system for judging processes characterized by dilatation of the renal pelvis. Experience suggests that ultrasonography is an effective procedure in the diagnosis of certain diseases of the upper urinary tract in dogs.     

THE EFFECT OF THE SAMPLE SIZE AND LOCATION ON CONTRAST ULTRASOUND MEASUREMENT OF PERFUSION PARAMETERS

Contrast‐enhanced ultrasound can be used to quantify tissue perfusion based on region of interest (ROI) analysis. The effect of the location and size of the ROI on the obtained perfusion parameters has been described in phantom, ex vivo and in vivo studies. We assessed the effects of location and size of the ROI on perfusion parameters in the renal cortex of 10 healthy, anesthetized cats using Definity^® contrast‐enhanced ultrasound to estimate the importance of the ROI on quantification of tissue perfusion with contrast‐enhanced ultrasound. Three separate sets of ROIs were placed in the renal cortex, varying in location, size or depth. There was a significant inverse association between increased depth or increased size of the ROI and peak intensity (P<0.05). There was no statistically significant difference in the peak intensity between the ROIs placed in a row in the near field cortex. There was no significant difference in the ROIs with regard to arrival time, time to peak intensity and wash‐in rate. When comparing two different ROIs in a patient with focal lesions, such as suspected neoplasia or infarction, the ROIs should always be placed at same depth and be as similar in size as possible.     

CONTRAST AGENT Gd‐EOB‐DTPA (EOB·Primovist®) FOR LOW‐FIELD MAGNETIC RESONANCE IMAGING OF CANINE FOCAL LIVER LESIONS

Contrast‐enhanced magnetic resonance (MR) imaging with a new liver‐specific contrast agent gadolinium‐ethoxybenzyl‐diethylenetriamine penta‐acetic acid (Gd‐EOB‐DTPA; EOB·Primovist®) was studied in 14 normal beagles and 9 dogs with focal liver lesions. Gd‐EOB‐DTPA accumulates in normally functioning hepatocytes 20 min after injection. As with Gd‐DTPA, it is also possible to perform a dynamic multiphasic examination of the liver with Gd‐EOB‐DTPA, including an arterial phase and a portal venous phase. First, a reliable protocol was developed and the appropriate timings for the dynamic study and the parenchymal phase in normal dogs using Gd‐EOB‐DTPA were determined. Second, the patterns of these images were evaluated in patient dogs with hepatic masses. The optimal time of arterial imaging was from 15 s after injection, and the optimal time for portal venous imaging was from 40 s after injection. Meanwhile, the optimal time to observe changes during the hepatobiliary phase was from 20 min after injection. In patient dogs, 11 lesions were diagnosed as malignant tumors; all were hypointense to the surrounding normal liver parenchyma during the hepatobiliary phase. Even with a low‐field MR imaging unit, the sequences afforded images adequate to visualize the liver parenchyma and to detect tumors within an appropriate scan time. Contrast‐enhanced MR imaging with Gd‐EOB‐DTPA provides good demarcation on low‐field MR imaging for diagnosing canine focal liver lesions.     

ULTRASONOGRAPHIC DETERMINATION OF RENAL VOLUME IN THE DOG

Ultrasonographic linear and area measurements were performed on both kidneys of 15 clinically healthy dogs. Renal volumes were calculated from linear and area data applying three prolate ellipsoid models. Ultrasonographic volumes were then compared using linear regression analysis with kidney volumes measured in vitro by water displacement. In vivo ultrasonographic volumes had a statistically significant relationship with the in vitro volume. The highest correlation was provided by the single plane area method. There was also a correlation between body weight and ultrasonographically detected renal volume, suggesting that ultrasound imaging may be a useful method for assessment of renal volume changes in dogs with renal disease.     

QUANTITATIVE CONTRAST HARMONIC ULTRASOUND IMAGING OF NORMAL CANINE LIVER

Eight adult dogs with no evidence of liver disease, weighing between 8 and 25 kg were imaged after injection of a microbubble contrast medium using harmonic ultrasound imaging. All dogs received three separate bolus contrast injections, and six dogs also received three separate constant rate infusions each. Time/Mean Pixel Value curves were generated for selected regions of the liver. Upslope, downslope, baseline, peak, change, and time to peak were calculated. For bolus injection (averaging all subjects), upslope was 3.85 +/- 1.50 Mean Pixel Values/s, downslope was -0.71 +/- 0.30 Mean Pixel Values/s, baseline was 72.38 +/- 17.82 Mean Pixel Values, peak was 120.26 +/- 17.44 Mean Pixel Value, change from baseline to peak was 47.88 +/- 6.92 Mean Pixel Values, time to peak (from injection) was 22.88 +/- 6.79 s, and time to peak (from first upslope) was 13.88 +/- 1.55 s. Data acquisition and analysis from constant rate infusions was more cumbersome than for bolus, and results were less repeatable. There were significant differences (p < .005) in upslope, downslope, peak values, and time to peak between the two methods. These baseline data may prove useful in the evaluation of dogs with diffuse hepatic disease.     

CONTRAST HARMONIC IMAGING OF THE NORMAL CANINE SPLEEN

The purpose of this study was to assess the perfusion pattern and perfusion dynamics in the normal canine spleen using contrast harmonic imaging. Twenty-five dogs without clinical or ultrasonographic evidence of splenic disease were studied. Twenty-three dogs were scanned with only manual restraint; two dogs were sedated with buprenorphin. All dogs received an intravenous bolus of a microbubble contrast medium (SonoVue). The perfusion pattern during the blood pool phase represented a skewed bell-shaped curve. A tissue-specific late phase, similar to humans, was not observed. Time/intensity curves were generated for a selected region. Mean average-derived peak intensity (PI) was 6.6dB, mean time to peak intensity calculated from the initial rise (TTP) was 25.6 s and mean area under the curve (AUC) was 523.6 dBs. If dogs were divided into two body weight groups (< or =15 and >15 kg body weight), average derived peak intensity area, time to peak intensity, and area under the curve were lower for the smaller dogs than for the larger animals. However, differences were not statistically significant (P = 0.2, 0.05, and 0.08, respectively). No significant association was found between hematocrit, hemoglobin concentration, red blood cell count, blood pressure, heart rate, age, gender, and the perfusion variables. In conclusion, these baseline data may prove useful in the evaluation of dogs with diffuse or focal splenic disease.     

FEASIBILITY OF PERCUTANEOUS CONTRAST ULTRASOUND‐GUIDED CHOLECYSTOGRAPHY IN DOGS

Differentiating hepatocellular disease versus biliary obstruction can be challenging in dogs presented for icterus. The purpose of this prospective study was to determine the feasibility of percutaneous contrast ultrasound‐guided cholecystography in dogs. Ten normal dogs weighing 7.6–13.0 kg (median 9.8 kg) were recruited. All dogs were considered normal based on complete blood count, serum chemistry profile, ultrasound examination, and percutaneous radiographic cholecystography. Percutaneous contrast ultrasound‐guided cholecystography was performed using 0.5 ml of commercially available contrast agent and two conventional ultrasound machines for simultaneous scanning at two different locations. Two observers independently evaluated the time to initial detection of contrast in the proximal duodenum and duration of contrast enhancement via visual monitoring. Dynamic contrast enhancement was calculated using time‐intensity curves. Mean (±SD) and median (range) of time to initial detection were 8.60 s (± 3.35) and 8.0 s (2.0–11.0), respectively, and mean and median duration were 50.45 s (±23.24) and 53.0 s (20.0 – 70.0), respectively. Mean, median, and range of peak intensity were 114.1 mean pixel value (MPV) (SD ± 30.7), 109.2 MPV, and 79.7–166.7, respectively, and mean, median, and range of time to peak intensity were 26.1 s (SD ± 7.1 s), 24.0 s, and 19.0–41.0 s, respectively. Findings indicated that percutaneous contrast ultrasound‐guided cholecystography is a feasible technique for detecting and quantifying patency of the bile duct in normal dogs. Future studies are needed to assess the diagnostic utility of this technique for dogs with biliary obstruction.     

CONTRAST ENHANCED SONOGRAPHIC ASSESSMENT OF FEEDING VESSELS AS A DISCRIMINATOR BETWEEN MALIGNANT VS. BENIGN FOCAL SPLENIC LESIONS

Contrast‐enhanced sonography was conducted in 17 confirmed focal splenic lesions (five malignant, 12 benign). Relative echogenicity changes were used for subjective interpretation of lesion perfusion. A rapid influx of contrast agent, resulting in an increased relative echogenicity of the lesion, followed by a rapid clearance of contrast agent was referred to as early washin/early washout. There were 6/12 benign, and 3/5 malignant lesions characterized by early washin/early washout. Therefore, sensitivity, specificity, and accuracy for this parameter in differentiating malignant from benign lesions was 60%, 50%, and 53%, respectively. There were 2/12 benign, and 2/5 malignant lesions with persistent hypoperfusion throughout all phases. Therefore, sensitivity, specificity, and accuracy for malignancy using this criterion were 40%, 83%, and 71%, respectively. However, none of the benign and all malignant lesions were characterized by tortuous and persistently visible feeding vessels. This suggests that interpretation of splenic lesions cannot be performed accurately on the basis of echogenicity or persistent hypoperfusion, but that assessment of vascular tortuosity may be helpful in discriminating between a malignant vs. benign focal splenic lesion.     

SONOGRAPHIC APPEARANCE OF RENAL NEOPLASIA IN THE DOG

Eight dogs with renal neoplasia were radiographically and sonographically examined. An enlarged, nonopacified kidney was seen on the excretory urogram in four dogs, but differentiation between a solid mass or severe hydronephrosis was not possible. The excretory urogram suggested an avascular lesion in one kidney, but differentiation between solid or cystic disease was not possible. Renal neoplasia was diagnosed in two dogs by excretory urography. Radiographic examination suggested splenic neoplasia in one dog. Solid masses were sonographically diagnosed in all dogs. A metastatic lesion was sonographically diagnosed in the opposite kidney of one dog that was missed on the radiographic examination. Ultrasonography com-plemented radiography as a diagnostic modality in eliciting additional information on renal disease. Sonograms did not allow determination of tumor cell type or whether the tumor was benign or malignant.     

Contrast‐enhanced ultrasonography characteristics of intrathoracic mass lesions in 36 dogs and 24 cats

Contrast‐enhanced ultrasonography (CEUS) is increasingly available for veterinary patients, however limited studies describe the use of this method for characterizing intrathoracic mass lesions. The aim of this prospective, observational study was to describe CEUS enhancement patterns for intrathoracic mass lesions in a sample of cats and dogs. Sixty patients (36 dogs, 24 cats) were included. Standardized CEUS examinations were performed for 41 pulmonary masses (68%) and 19 mediastinal masses (32%). Final diagnosis was based on cytology and/or histopathology. Absolute time to enhancement (TTE) values were recorded for the intrathoracic mass lesions and spleen. The spleen was used as a reference parenchymal organ to calculate relative TTE (rTTE) values. Absolute TTE of the spleen and intrathoracic mass lesions differed for dogs and cats (P = 0.001). The rTTE values significantly differed between lesions of neoplastic versus non‐neoplastic origin (P = 0.004). The majority of neoplastic pulmonary masses were supplied by bronchial arteries (63%), while most nonneoplastic pulmonary masses were supplied by pulmonary arteries (78%). The sensitivity and specificity for detecting pulmonary neoplastic masses with rTTE were 63% and 78%, respectively. Enhancement patterns for mediastinal thymomas and lymphomas significantly differed (P = 0.002). Thymomas enhanced heterogeneously in a centripetal pattern (86%), whereas lymphomas typically enhanced uniformly in a centrifugal pattern (75%). Findings indicated that CEUS is a feasible method for characterizing intrathoracic mass lesions in dogs and cats, however, the diagnostic sensitivity for detecting neoplastic pulmonary masses was low.     

CONTRAST‐ENHANCED ULTRASONOGRAPHIC FINDINGS IN THREE DOGS WITH PANCREATIC INSULINOMA

Abdominal ultrasonography is one of the most common diagnostic imaging modalities used for dogs with suspected insulinoma; however, pancreatic masses are clearly identified in fewer than half of affected dogs and benign pancreatic nodules can be difficult to differentiate from malignant ones. The purpose of this prospective study was to describe contrast‐enhanced ultrasonography (CEUS) characteristics of confirmed pancreatic insulinoma in a group of dogs. Inclusion criteria were as follows: (1) repeated hypoglycemia (blood glucose levels <60 mg/dl, twice or more); (2) elevated blood insulin levels with hypoglycemia; (3) pancreatic nodules detected with conventional ultrasonography; and (4) histological confirmation of pancreatic islet cell carcinoma. Immediately following conventional ultrasonography of the entire abdomen, CEUS of the pancreatic nodule and adjacent parenchyma was performed using contrast‐specific technology pulse inversion imaging and perflubutane microbubble contrast agent. Three dogs met inclusion criteria. Pancreatic nodules in all the three dogs became more clearly demarcated after injection of the contrast agent. Each nodule showed different enhancement patterns: markedly hyperechoic for 5 s, slightly hyperechoic for 1 s, and clearly hypoechoic for over 30 s. These results were not in complete agreement with previously reported CEUS findings in human patients with insulinoma. All nodules were surgically resected and histopathologically confirmed as malignant insulinomas. Findings from the current study indicated that contrast‐enhanced ultrasound may help to increase conspicuity of pancreatic insulinomas in dogs and that enhancement characteristics may be more variable in dogs than in humans.     

CONTRAST HARMONIC ULTRASOUND OF SPONTANEOUS LIVER NODULES IN 32 DOGS

Thirty-two dogs with spontaneous hepatic nodules were given intravenous ultrasound contrast medium (Definity or Sonovue) and imaged with contrast harmonic software on a conventional ultrasound machine system. Digital video images were initially reviewed to describe the perfusion pattern of malignant nodules. The images were reviewed again to test this pattern against all individual nodules. Subjectively, there was improved conspicuity of malignant nodules after contrast enhancement compared with conventional imaging and increased numbers of malignant nodules were often noted. There was decreased conspicuity of benign nodules and no additional nodules were seen after contrast enhancement. There was a highly significant (P < 0.0001) association of malignancy with a hypoechoic nodule at surrounding normal liver peak contrast enhancement. Benign nodules were isoechoic to the surrounding normal liver at peak contrast enhancement. Only one benign nodule (hepatoma) had regions of hypoechogenicity compared with the surrounding normal liver at peak liver contrast enhancement. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were highly significant (P < 0.0001) (100%, 94.1%, 93.8%, 100%, and 96.9%, respectively). No complications or morbidity was noted throughout the course of the study. Contrast harmonic ultrasound appears to be accurate at discriminating between naturally occurring benign and malignant nodules in the liver of dogs.     

RENAL ULTRASONOGRAPHIC AND COMPUTED TOMOGRAPHIC APPEARANCE, VOLUME, AND FUNCTION OF CATS WITH AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY DISEASE

The purpose of this study was to describe the ultrasonographic (US) and computed tomographic (CT) appearance of autosomal dominant polycystic kidney disease (ADPKD) in cats; to compare renal volume in cats with ADPKD (n = 5; mean age 59 +/- 10 months)) and normal cats (n = 5; mean age 66 +/- 10 months) using 2 imaging modalities, US and CT; and to calculate cyst volume using CT. Glomerular filtration rate (GFR) was determined by 2 methods: 99mTc-diethylene-triaminepentaacetic acid (99mTc-DPTA) scintigraphic uptake and 99-Tc-DTPA plasma clearance. Sonographically, ADPKD affected kidneys were characterized by multiple anechoic to hypoechoic, round to irregularly shaped structures with variation in size. Affected kidneys had indistinct corticomedullary junctions and foci of mineralization. Intravenous (IV) contrast medium administration allowed more definitive identification of cysts with CT, and identification of distortion of renal pelves by cysts. A significant difference (Welch ANOVA, P = 0.05) was detected between the US-estimated renal volumes of normal and affected cats. No statistically significant differences were detected in CT volume (between the normal and affected cats, or between US and CT volume measurements) or the 2 GFR methods. In this group of clinically normal, middle-aged ADPKD cats, renal function was within normal limits and not significantly different than normal.