Effect of anaesthesia on contrast-enhanced ultrasound of the feline spleen

Computed tomographic heterogeneous enhancement of spleen in healthy cats: comparing with diffuse infiltrative splenic lesions

Introduction

Contrast-enhanced computed tomography (CT) of the spleen in dogs and cats often displays a heterogeneous enhancement pattern. This study aimed to describe the CT appearances and duration of heterogeneous splenic enhancement in clinically healthy cats and to compare those enhancements with diffuse infiltrative splenic lesions (DISL).

Methods

Spleens of 14 healthy cats were imaged using contrast-enhanced CT protocols which were obtained at 10, 25, and 45 s, and then every 40 s thereafter until 245 s had past from the initiation of contrast medium injection. The presence of transient splenic heterogeneity was evaluated. In addition, the relationships of certain variables including age, weight, systolic blood pressure, and splenic volume to the duration and the degree of splenic enhancement were determined. Also, medical records and CT images of five cats with DISL were retrospectively evaluated.

Result

Transient heterogeneous enhancement of the spleen was observed in all 14 healthy cats, and the maximum heterogeneity was observed 25 s after the injection. Splenic heterogeneity lasted more than 5 min in nine of 14 cats (64.3%). No statistically significant relationships were seen between the duration and degree of splenic heterogeneity in the images taken 25 s after the injection and variables including weight, age, systolic blood pressure, and splenic volume.

Discussion

Compared to the healthy group, early homogeneous splenic enhancement along with generalized splenomegaly was observed in all cats with DISL. Transient splenic heterogeneity is highly common in cats undergoing contrast-enhanced CT even in the generally scanned delayed phases, which can help with the interpretation of CT images of feline spleens. In addition, our results suggest that homogeneous splenic enhancement in post-contrast CT scans along with splenomegaly on CT images could be useful as a diagnostic indicator of DISL in cats.

Contrast-enhanced ultrasonography of the thyroid gland in healthy dogs, hypothyroid dogs and dogs with non-thyroidal illness

Diagnosis of canine hypothyroidism remains challenging, as non-thyroidal illness (NTI)-syndrome and medical treatment can influence thyroid hormone concentrations. Conventional ultrasound may give additional hints, however high interobserver variability has been described. Contrast-enhanced ultrasound (CEUS) allows detection of changes in tissue perfusion. The purpose of the present study was to assess the possible diagnostic value of CEUS regarding diagnosis of hypothyroidism. CEUS of the thyroid gland was performed in 52 healthy dogs, 16 hypothyroid dogs, and 20 NTI patients. The following perfusion parameters were calculated: Thyroid/carotid artery (TG/CA) ratios for peak enhancement (PE) and area under the curve (AUC), time to peak (TTP) and wash-in and wash-out rates (WiR, WoR) of the thyroid gland. Impact of sedation on perfusion parameters was investigated in 8 calm healthy dogs which were examined before and after sedation using midazolam and butorphanol. Significantly higher median TG/CA ratios for PE were detected for the left and right thyroid lobe in dogs with hypothyroidism (0.97/0.96) compared to healthy dogs (0.85/0.85) and dogs with NTI (0.84/0.84). AUCs were also significantly increased in hypothyroid dogs when compared to other groups. Dogs with NTI showed significantly lower WiR and WoR compared to other groups. Values for TTP were not significantly different between groups. Sedation had only impact on results of TTP which was significantly prolonged in sedated dogs. In conclusion, CEUS of the thyroid gland can provide an additional tool for diagnosis of hypothyroidism in dogs and support its differentiation from NTI. Sedation has limited impact on CEUS results.

Applications of Contrast-Enhanced Ultrasound in Splenic Studies of Dogs and Cats

Simple Summary

Contrast-enhanced ultrasound (CEUS) is a noninvasive imaging technique that has become a reliable tool for identifying and monitoring lesions in both human and animals. In the last decade, its use in veterinary diagnostic imaging has gained increasing importance, and it can be reliable in everyday clinical practice. However, there is a lack of reviews describing existing CEUS results in the study of splenic lesions, which is of particular importance in dogs and cats. This information is important for validating its efficacy, to facilitate decision making related to sampling procedures and diagnosis, or even as a means to select CEUS as an alternative diagnostic tool in specific cases. Our goal was to review the existing studies of CEUS applications for splenic ultrasound studies in cats and dogs, present these results in a systematic manner, and combine this information into practical guidelines that can be used to help diagnosis and interpretation in both clinical cases and research.

Abstract

Contrast-enhanced ultrasound (CEUS) is an emerging technology in veterinary medicine involving the administration of intravenous contrast agents, and it is increasingly recognized for its high potential as a diagnostic imaging tool for small animals. This exam is easy and quick to perform, safe and reliable, and allows for the differentiation of lesions. It permits the identification of lesions that may require more invasive procedures, from those that can be safely dismissed to those that can be followed-up with ultrasound imaging. Although it has been extensively reviewed for use in human medicine, there is an overall lack of information about the application of this technique for cats and dogs, particularly in splenic studies, which can be particularly important for small animals. The present review describes and summarizes the CEUS applications used for splenic analysis in cats and dogs, providing a basic overview of CEUS technology with examples of common and uncommon features of focal splenic lesions. It also systematically gathers the results obtained for benign and malignant splenic lesions described in the literature, whilst providing guidelines for their interpretation. Furthermore, it presents the advantages of using CEUS for splenic analysis in cats and dogs and the main factors that may influence the quality of the imaging and the accuracy of the diagnosis. This type of knowledge can be used to provide a framework to help veterinarians make informed decisions regarding the use of this emerging technique for splenic lesions, guiding their interpretation of CEUS findings in the splenic ultrasounds of cats and dogs.

Impact of region-of-interest size and location on quantitative contrast-enhanced ultrasound of canine splenic perfusion

Background

During contrast enhanced ultrasound (CEUS), the features of the regions of interest (ROI) can affect the value of the perfusion-related parameters obtained from a time intensity curve (TIC). In veterinary medicine, conflicting have been reported on the influence of ROI size and location on renal CEUS. There are some disagreeing evidences regarding the optimal method for selecting ROI in quantitative analysis of renal perfusion using CEUS.

The aim of this study was to evaluate the effect of the size and location of ROIs in the spleen of conscious dogs on perfusion variables determined using sulphur hexafluoride contrast-enhanced ultrasounds.

Results

A prospective observational study on 15 client-owned mixed-breed adult dogs was performed using a system equipped with contrast-tuned imaging technology. Qualitative and quantitative assessments of the spleen enhancement pattern were carried out. Three square ROIs (0.05 cm²) were manually drawn in a row and spaced 1 mm apart, placing adjacent ROIs at three different depths. Three medium rectangular ROIs (0.3 cm²) include the 3 smallest ROIs in each row, indicated by the letters A, B and C, and a single large square ROI (1 cm²) was drawn containing all previous ROIs. Software analysis of time-intensity curves generated within each ROI allowed us to calculate the perfusion-related parameters: peak enhancement, time to peak, regional blood flow, mean transit time and regional blood volume.

The coefficient of variation for all blood-related parameters was always lower in the larger ROI than in the other smaller ROIs. ROI A and B, positioned proximally and medially, levels respectively, showed similar coefficients of variation to the largest ROI. The analysis of variance model exhibited a significant effect of location and size of the ROIs in the quantitative analysis of canine spleen perfusion, with a reduction of perfusion-related parameters in the distal ROI.

Conclusions

The recommendation for a quantitative CEUS examination of a dog’s spleen is to analyze splenic perfusion by drawing a sufficiently large ROI proximal to the ultrasound beam on the splenic parenchyma. This may be of clinical relevance in the diagnosis of splenic diseases.

Effects of Butorphanol With Alfaxalone or Dexmedetomidine on Feline Splenic Size and Appearance on Ultrasound and Computed Tomography

The purpose of the study was to determine the effects of intramuscular butorphanol with dexmedetomidine or alfaxalone on feline splenic size, echogenicity, and attenuation using ultrasound and computed tomography (CT). Ten healthy research cats underwent ultrasound and CT without sedation (controls), 15 min after protocol AB (alfaxalone 2 mg/kg and butorphanol 0.2 mg/kg) and 10 min after protocol DB (dexmedetomidine 7 μg/kg and butorphanol 0.2 mg/kg), with a one-week wash-out period between each sedation, using a cross-over study design. Images were randomized and anonymized for evaluation by a board-certified radiologist. On ultrasound, the sedative protocols affected splenic thickness, at the body and the tail (p = 0.002 and 0.0003, respectively). Post-hoc tests revealed that mean ± SEM thickness was greater after AB (body: 10.24 ± 0.30 mm; tail: 7.96 ± 0.33 mm) than for the control group (body: 8.71 ± 0.30 mm; tail: 6.78 ± 0.33 mm), while no significant difference was observed following DB. Splenic echogenicity was unchanged between treatments (p = 0.55). On CT, mean ± SEM splenic volume was increased after AB (37.82 ± 1.91 mL) compared to the control group (20.06 ± 1.91 mL) (p < 0.0001), but not after DB (24.04 ± 1.91 mL). Mean splenic attenuation increased after AB (p = 0.0009), but not DB. Protocol DB may be preferable for profound sedation in cats while avoiding changes in feline splenic imaging. When protocol AB is selected, splenomegaly should be expected, though mild on ultrasound. The increased splenic attenuation after AB is unlikely to be clinically relevant.

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.

Effects of size and location of regions of interest examined by use of contrast-enhanced ultrasonography on renal perfusion variables of dogs

OBJECTIVE To determine effects of the size and location of regions of interest (ROIs) in the renal cortex of unsedated dogs on renal perfusion variables determined by use of contrast-enhanced ultrasonography (CEUS). ANIMALS 12 client-owned adult (1.5 to 2 years old) Labrador Retrievers (8 males and 4 females; mean ± SD body weight, 27 ± 1.6 kg). PROCEDURES Each dog received 2 bolus injections of sulfur hexafluoride during CEUS. Three small oval ROIs (area of each ROI, 0.11 cm(2)) located in a row with a distance of 1 mm between adjacent ROIs and 1 large oval ROI (area, 1 cm(2)) that encompassed the 3 smaller ROIs were manually drawn in the renal cortex. The ROIs were located at a depth of 1.5 to 2.0 cm in the near field of the renal cortex. Software analysis of time-intensity curves within each ROI was used to identify peak enhancement, time to peak enhancement, regional blood flow, and mean transit time. RESULTS The location and size of the ROIs of unsedated dogs did not cause significant differences in the mean values of the renal perfusion variables. CONCLUSIONS AND CLINICAL RELEVANCE The development of CEUS has provided a unique means for visually examining and quantifying tissue perfusion. Results of this study indicated that it was possible to use small or large ROIs during renal CEUS to evaluate renal perfusion in dogs.

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/m(2) 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.

Contrast-enhanced ultrasound of both kidneys in healthy, non-anaesthetized cats

Background

Changes in perfusion are considered to play a key role in the pathophysiology of renal disease. Contrast-enhanced ultrasound (CEUS) has shown a promising diagnostic imaging technique to non-invasively and repetitively quantify tissue perfusion. Examination protocols have varied between studies regarding US equipment, quantification software, the use of sedation or anaesthesia, and animals. The purpose of the present study was, to assess the feasibility of a standardized CEUS protocol for perfusion analysis of both kidneys in nine healthy, non-anaesthetized cats.

Results

CEUS was fairly tolerable for all but one cat. In 6/18 kidneys (2 left, 4 right), a second contrast medium injection was needed due to motion artifacts. Perfusion variables such as peak intensity (PI), wash-in slope (WI_S), wash-out slope (WO_S) and mean transit time (MTT) did not significantly differ between left and right renal cortex and medulla nor between the cranial and caudal renal cortex within each kidney. In contrast, for all kidneys, mean PI, WI_S, and MTT were significantly higher in the cortex than in the medulla (P = 0.001, 0.012 and <0.001, respectively).

Conclusions

The herein reported CEUS protocol and the perfusion measurements may serve as a baseline protocol and normal reference values for the evaluation of feline patients. However, the protocol and results may be of limited value in uncooperative animals.

Contrast enhanced ultrasonography of kidney in conscious and anesthetized beagle dogs

Contrast enhanced ultrasound (CEUS) is useful to evaluate tissue perfusion in the kidney. In veterinary medicine, sedation or anesthesia may be required in uncooperative or panting patients. The aim of this study was to evaluate and compare the normal kidney perfusion patterns in conscious and anesthetized dogs using CEUS. Eight healthy beagles were used in this study. Scanning was performed in conscious dogs using manual restraint (conscious group), or under general anesthesia using tiletamine-zolazepam and medetomidine (TZM group) or medetomidine (M group). The contrast agent (Sonovue^®) was administered as an IV bolus. The peak intensity (PI), time to peak enhancement from injection (TTP₀) and the time to peak enhancement from the initial rise (TTP_up), upslope, downslope and area under the curve (AUC) were analyzed. Compared to the cortical values in the conscious group, TTP₀ was significantly delayed in the TZM group, and upslope, TTP₀ and TTP_up were significantly different in the M group. The AUCs in the TZM and M groups were not different from those in the conscious group. The upslope of renal medullary perfusion was significantly decreased in the TZM and M groups. TTP₀ and TTP_up were also significantly delayed in these groups. The AUC of the medulla was significantly decreased in the M group. Therefore, TZM is useful as an anesthetic protocol when performing CEUS, and the obtained data may serve as reference values in the evaluation of renal perfusion using CEUS in dogs under anesthesia.

Contrast-enhanced ultrasonography of the pancreas in healthy cats

BACKGROUND

This study describes the pattern of ultrasonographic contrast enhancement of the pancreatic body and left lobe using a second-generation commercial contrast medium (Sonovue) in 10 clinically healthy cats.

RESULTS

Following contrast medium administration, microbubbles were observed within the splenic artery. This was followed by an inflow of contrast medium into the pancreatic capillary beds, providing a uniformly contrast-enhanced pancreas at peak intensity (PI). At the time of PI, a replenishment of the splenic and portal veins started and increased progressively during the wash-out phase. During the wash-out phase, the echogenicity of the pancreatic parenchyma decreased progressively. Perfusion parameters included arrival time (4.69 ± 1.26 s), time to peak from injection (7.52 ± 1.88 s), time to peak from initial rise (2.84 ± 0.88 s), peak intensity (6.58 ± 2.66 a.u.), and wash-in rate (2.11 ± 1.79 a.u./s).

CONCLUSIONS

This perfusion pattern of normal pancreatic parenchyma may be useful for characterising cats with exocrine pancreatic disorders.

The effect of anesthesia with propofol and sedation with butorphanol on quantitative contrast-enhanced ultrasonography of the healthy feline kidney

Contrast-enhanced ultrasonography of the left kidney was performed using a commercial contrast agent in six healthy adult purpose-bred cats. A cross-over design was used to compare three protocols: (1) awake, (2) butorphanol (0.4 mg/kg IM), and (3) propofol (3.5-7.7 mg/kg IV boluses to effect). Time-intensity curves were created from two regions-of-interest drawn in the renal cortex. The curves were analyzed for blood flow parameters representing blood volume (base intensity, peak intensity, area-under-curve) and blood velocity (arrival time, time-to-peak, wash-in/out). There was no difference in the subjective enhancement pattern between the three protocols. No significant effect of butorphanol was observed in any of the perfusion parameters (P > 0.05). Propofol did not influence the most important perfusion parameter, area-under-the-curve, and is adequate for use in contrast-enhanced ultrasound studies.

Contrast-enhanced ultrasonography of the small bowel in healthy cats

We characterized the pattern of ultrasonographic contrast enhancement of the small intestinal wall using a commercial contrast medium (Sonovue(®) ) in 10 healthy awake cats. Subjectively, a rapid intense enhancement of the serosal and submucosal layers was followed by gradual enhancement of the entire wall section during the early phase. At peak enhancement, there was a subjective loss of demarcation between intestinal wall layers. In the late phase, there was a gradual wash out of signal from the intestinal wall. Submucosal wash out occurred last. Time-intensity curves were generated for selected regions in the intestinal wall and multiple perfusion parameters were calculated for each cat. Perfusion parameters included arrival time (7.64 ± 2.23 s), baseline intensity (1.04 ± 0.04 a.u.), time to peak from injection (10.74 ± 2.08 s), time to peak from initial rise (3.1 ± 1.15), peak intensity (8.92 ± 3.72 a.u.), wash-in rate (2.06 ± 0.70 a.u./s) and wash-out rate (-1.07 ± 0.91 a.u./s). The perfusion pattern of normal feline small bowel may be useful for characterizing feline gastrointestinal disorders that involve the intestinal wall.