Contrast-enhanced ultrasound analysis of renal perfusion in normal micropigs

Contrast-enhanced ultrasound is one of method for evaluating renal perfusion. The purpose of this project was to assess perfusion patterns and dynamics in normal micropig kidney using ultrasonographic contrast media. Eight young healthy micropigs were included in this study. Micropigs were anesthetized with propofol and received an intravenous bolus of microbubble contrast media through an ear vein. Time/mean pixel value (MPV) curves were generated for selected regions in the right renal cortex and medulla. The parenchyma was enhanced in two phases. The cortex was first enhanced followed by a more gradual enhancement of the medulla. A significant difference in perfusion was detected between the cortex and medulla. Following the bolus injection, the average upslope was 0.68 ± 0.27 MPV/sec, downslope was -0.27 ± 0.13 MPV/sec, baseline was 73.9 ± 16.5 MPV, peak was 84.6 ± 17.2 MPV, and time-to-peak (from injection) was 17.5 ± 6.6 sec for the cortex. For the medulla, the average upslope was 0.50 ± 0.24 MPV/sec, downslope was -0.12 ± 0.06 MPV/sec, baseline was 52.7 ± 7.0 MPV, peak was 65.2 ± 9.3 MPV, and time-to-peak (from injection) was 27.5 ± 5.0 sec. These data can be used as normal reference values for studying young micropigs.     

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.     

ULTRASONOGRAPHIC EXAMINATION OF THE CANINE LIVER BASED ON RECOGNITION OF HEPATIC AND PORTAL VEINS

A method for systematic examination of the livers was developed, based on identification of the hepatic and portal veins in sixteen dogs. The right medial, quadrate, left medial and lateral hepatic veins and the hepatic branches of the portal veins were easily located with the dog in dorsal recumbency. The right lateral and caudate hepatic veins were identified more easily from the right side with the transducer positioned between the ninth to the eleventh intercostal spaces. Visibility was affected by the fullness of the stomach but this effect could be minimized by changing the position of the transducer to select a more suitable anatomical approach. Identification of the two systems depended on their echogenicity, the anatomical position of the main branches and their pattern of distribution. As in humans, the portal veins were in general, more echogenic than the hepatic veins and the hepatic veins could be traced from their junctions with the caudal vena cava. Identification of the branches of the hepatic and portal veins was complicated by the anatomical shape, the nutritional status and respiratory stage of the animal. A systemic approach based on a knowledge of the distribution patterns produced by the hepatic and portal veins ensures that all liver lobes are identified and all important structures are assessed.     

CONTRAST ECHOAORTOGRAPHY AS AN AID IN THE DIAGNOSIS OF RIGHT-TO-LEFT SHUNTING PATENT DUCTUS ARTERIOSUS

Contrast echocardiography has traditionally been used in conjunction with conventional echocardiography to document right-to-left intracardiac shunting congenital anomalies. This technique does not clearly demonstrate shunting of blood in patients with right-to-left patent ductus arteriosus, as the shunt is extracardiac. We used a variation of contrast echocardiography, contrast echoaortography, to confirm the presence of a right-to-left shunting patent ductus arteriosus in two dogs.     

PREPUBIC AND TRANSRECTAL ULTRASONOGRAPHY OF THE CANINE PROSTATE: A COMPARATIVE STUDY

A comparative study was conducted in ten dogs with signs of prostatic disease in order to evaluate the usefulness of the prepubic and transrectal ultrasonography for the examination of the prostate gland and for prostate biopsy guidance. Both techniques were adequate to identify the prostate gland and prostatic urethra. Transrectal ultrasound found 5 occurrencies of parenchymal echogenicity changes whereas the prepubic technique found only 2. Lesions in the cranial prostatic margin (two dogs) were detected only by prepubic ultrasound. Lesions of the caudal prostatic margin (six dogs), prostatic urethra disruption (two dogs) and prostatic capsule abnormalities (five dogs) were only recognized by the transrectal approach. Prepubic ultrasonography was useful for biopsy guidance of cranial prostatic lesions and transrectal ultrasonography was a good means for biopsy guidance of caudal lesions.