Three-dimensional CT angiography of the canine hepatic vasculature

Eight Beagle dogs were anesthetized and were imaged using a single channel helical CT scanner. The contrast medium used in this study was iohexol (300 mg I/ml) and doses were 0.5 ml/kg for a cine scan, 3 ml/kg for an enhanced scan. The flow rate for contrast material administration was 2 ml/sec for all scans. This study was divided into three steps, with unenhanced, cine and enhanced scans. The enhanced scan was subdivided into the arterial phase and the venous phase. All of the enhanced scans were reconstructed in 1 mm intervals and the scans were interpreted by the use of reformatted images, a cross sectional histogram, maximum intensity projection and shaded surface display. For the cine scans, optimal times were a 9-sec delay time post IV injection in the arterial phase, and an 18-sec delay time post IV injection in the venous phase. A nine-sec delay time was acceptable for the imaging of the canine hepatic arteries by CT angiography. After completion of arterial phase scanning, venous structures of the liver were well visualized as seen on the venous phase.     

Dual-phase CT Angiography of the Normal Canine Portal and Hepatic Vasculature

A dual-phase computed tomography (CT) angiographic technique was developed to image the hepatic and portal vascular systems using a nonselective peripheral injection of contrast medium. The arterial phase of the dual-phase scan imaged the hepatic arteries and veins, and the portal phase imaged the portal vein as well as its tributaries and branches. There were three steps involved in acquiring the dual-phase scan: a survey helical scan for orientation, a dynamic scan for timing, and finally the dual-phase helical scan. Five normal dogs were imaged using a helical scan technique. The timing of the arterial and portal phases of the scan was calculated using time vs. attenuation graphs generated from a dynamic scan. The median time of appearance of contrast medium in the cranial abdominal aorta was 8.6 s and the median time of appearance of contrast medium in the hepatic artery occurred 0.4 s later. The median time of peak enhancement in the cranial abdominal aorta was 12.0 s. The median time of appearance of contrast medium in the portal vein was 14.6 s and median time of peak enhancement was 33.0 s. The dual-phase scans provided excellent vascular opacification. The hepatic arteries, hepatic veins, cranial and caudal mesenteric veins, splenic vein, gastroduodenal vein, and portal vein branches were all consistently well defined. Dual-phase CT angiography is a minimally invasive technique which provides an excellent three-dimensional representation of portal and hepatic vascular anatomy.     

CONTRAST-ENHANCED ULTRASONOGRAPHY FOR CHARACTERIZATION OF CANINE FOCAL LIVER LESIONS

In six normal beagles and 27 dogs with spontaneous focal or multifocal liver lesions, contrast-enhanced ultrasonography using Sonazoid^® was performed. Sonazoid^® is a newly developed second-generation contrast agent with the ability to be used for real-time contrast imaging along with parenchymal imaging. An appropriate protocol for the evaluation of all three phases (arterial, portal, and parenchymal) was established based on the results for normal beagles. By evaluation of the echogenicity of hepatic nodules during the arterial and parenchymal phases it was possible to differentiate malignant tumors from benign nodules with very high accuracy. In 15 of 16 dogs diagnosed as malignant tumors, nodules were clearly hypoechoic to the surrounding normal liver during the parenchymal phase. Additionally, malignant tumors had different echogenicity compared with the surrounding normal liver during the arterial phase in 14 of 15 dogs. In the portal phase, there were no characteristic findings. Contrast-enhanced ultrasonography with Sonazoid^® appears to improve the characterization of canine focal and multifocal hepatic lesions.     

ASSOCIATIONS BETWEEN DUAL‐PHASE COMPUTED TOMOGRAPHY FEATURES AND HISTOPATHOLOGIC DIAGNOSES IN 52 DOGS WITH HEPATIC OR SPLENIC MASSES

Ability to noninvasively differentiate malignant from nonmalignant abdominal masses would aid clinical decision making. The aim of this retrospective, cross‐sectional study was to identify features in dual‐phase computed tomographic (CT) studies that could be used to distinguish malignant from nonmalignant hepatic and splenic masses in dogs. Medical records were searched for dogs that had an abdominal dual‐phase CT examination, a hepatic or splenic mass, and subsequent histopathologic diagnosis. Computed tomographic images for all included dogs were acquired prior to and <30 s (early phase) and >60 s (delayed phase) after intravenous contrast administration. Fifty‐two dogs with 55 masses were studied: 24 hepatic, including 14 (58%) malignant and 10 (42%) non‐malignant; 31 splenic, including 18 (58%) malignant and 13 (42%) nonmalignant. There was substantial overlap in the pre‐ and postcontrast CT features of malignant and nonmalignant hepatic and splenic masses. Regardless of histologic diagnosis, hepatic masses most frequently showed marked, generalized enhancement in early phase images that persisted in the delayed phase. Splenic hemangiosarcoma and nodular hyperplastic lesions most frequently showed marked, generalized enhancement in early phase images that persisted in delayed images whereas most splenic hematomas had slight enhancement in early phase images. All splenic hematomas and 77% of the hemangiosarcomas had contrast accumulation compatible with active hemorrhage. There were no other significant differences in quantitative or categorical CT data between malignant and nonmalignant hepatic or splenic masses. Dual‐phase CT of dogs with hepatic or splenic masses provides limited specific diagnostic information.     

TRIPLE‐PHASE HELICAL COMPUTED TOMOGRAPHY IN DOGS WITH HEPATIC MASSES

The purpose of this study was to determine the utility of triple‐phase helical computed tomography (CT) for differentiating canine hepatic masses. Seventy dogs with hepatic masses underwent triple‐phase CT followed by surgical removal of the hepatic masses. Triple‐phase helical CT scans for each dog included precontrast, arterial phase, portal venous phase, and delayed phase studies. The removed hepatic masses were histopathologically classified as hepatocellular carcinoma (n = 47), nodular hyperplasia (n = 14), and hepatic metastatic tumors (n = 9) in dogs. Of the 47 hepatocellular carcinomas, the most common CT findings included a heterogeneous pattern with hyper‐, iso‐, and hypoenhancement in both the arterial and portal venous phases (40/47, 85.1%). Of the 14 nodular hyperplasias, the most common CT findings were a homogeneous pattern with hyper‐ and isoenhancement in both the portal venous and delayed phases (13/14, 92.9%). Of nine hepatic metastatic tumors, the most common CT findings included a homogeneous hypoenhancement pattern in both the arterial and portal venous phases (8/9, 88.9%). In addition, 5 (55.6%) showed homogeneous hypoenhancement patterns in the delayed phase. Findings from our study indicated that triple‐phase CT is a useful tool for preoperative differentiation of hepatocellular carcinoma, nodular hyperplasia, and hepatic metastatic tumors in dogs.     

Evaluation of a novel tumor vaccine in dogs with hemangiosarcoma

BACKGROUND: Hemangiosarcoma (HSA) is a highly metastatic and often rapidly fatal tumor of dogs. At present, adjuvant chemotherapy is the only proven effective treatment for dogs with HSA, though the benefits from chemotherapy are modest. Administration of immunotherapy together with chemotherapy has also been reported to improve survival in dogs with HSA. Therefore, we evaluated safety and immunologic responses to a novel tumor vaccine administered together with doxorubicin chemotherapy in dogs with different stages of HSA. HYPOTHESIS: That tumor vaccination could be safely and effectively combined with doxorubicin chemotherapy for treatment of dogs with HSA. ANIMALS: Twenty-eight dogs with various stages of HSA were enrolled in the study. METHODS: The HSA vaccine was prepared with lysates of allogeneic canine HSA cell lines mixed with an adjuvant composed of liposome-DNA complexes. Dogs received a series of 8 immunizations administered over a 22-week period, and most also received chemotherapy. Clinical adverse effects were noted, immune responses were measured by enzyme-linked immunosorbent assay (ELISA) and flow cytometry, and survival times were calculated. RESULTS: The most common adverse effects observed in vaccinated dogs also treated with doxorubicin chemotherapy were diarrhea and anorexia. Vaccinated dogs were found to mount strong humoral immune responses against a control antigen and, most dogs also mounted antibody responses against canine HSA cells. Thirteen dogs with stage II splenic HSA that received the tumor vaccine plus doxorubicin chemotherapy had an overall median survival time of 182 days. CONCLUSIONS: We conclude that an allogeneic tumor lysate vaccine is safe in dogs with HSA and can elicit humoral immune responses in dogs that are receiving concurrent doxorubicin chemotherapy.     

HELICAL COMPUTED TOMOGRAPHIC ANGIOGRAPHY OF THE NORMAL CANINE PANCREAS

Helical abdominal computed tomography (CT) was performed in nine normal beagle-mix dogs. Following cephalic vein injection of ionic iodinated contrast medium via power injector (rate 5 ml/s) dual-phase CT was performed in all dogs. A delayed scan was performed in five dogs between 5 and 13 min after the contrast medium injection. The median time of appearance of contrast medium in the aorta and gastroduodenal artery was 6.3 and 7 s, post start injection and 12 and 12.2 s in the gastroduodenal and portal vein, resulting in a purely arterial pancreatic time window of 5-6s. Pancreatic veins and parenchyma remained enhanced until the end of the dynamic scan (40s). The pancreatic parenchyma showed heterogeneous arterial and homogenous venous contrast enhancement which was slightly hypoattenuating compared to the liver. Delayed scans provided best delineation of the pancreas from the liver. The common bile duct could be identified ventral and to the right of the portal vein joining the dorsomedial aspect of proximal duodenum. Because of the very short time window and variable onset of pure arterial enhancement careful planning of dual-phase studies with previous dynamic CT is recommended. Dual-phase CT angiography enables assessment of the arterial supply, parenchymal perfusion and venous drainage of the canine pancreas.     

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.     

Effect of catheter size and injection rate of contrast agent on enhancement and image quality for triple‐phase helical computed tomography of the liver in small dogs

Rapid contrast injection is recommended for triple‐phase helical computed tomography (CT) of the liver. However, a large‐gauge catheter is needed for faster contrast injection and this is not practical for small breed dogs or cats. The purpose of this crossover group study was to evaluate applicability of a lower injection rate with a small‐gauge (G) catheter for triple‐phase hepatic CT in small dogs. Triple‐phase CT images were acquired for six beagle dogs using three protocols: an injection rate of 1.5 ml/s with a 24 G catheter, 3.0 ml/s with a 22 G catheter, and 4.5 ml/s with a 20 G catheter. Enhancement of the aorta, portal vein, and hepatic parenchyma was measured in each phase (arterial, portal, and delayed) and image quality was scored subjectively by two observers. Injection duration, time to scan delay, and time to peak enhancement were also recorded. Contrast injection duration decreased with a higher injection rate (n = 6, P ≤ 0.01), but time to peak enhancement and time to scan delay were not significantly affected by injection rates and catheter sizes. Contrast injection rate did not significantly affect aortic, portal, and hepatic enhancement. In addition, separation between each phase and quality of images was subjectively scored as good regardless of injection rate. Findings from the current study supported using an injection rate of 1.5 ml/s with a catheter size of 24 G for triple‐phase hepatic CT in small dogs (weight < 12 kg).     

POST-OPERATIVE COMPUTED TOMOGRAPHY IN TWO DOGS WITH CEREBRAL MENINGIOMA

Post-operative computed tomography (CT) has been described as a technique for diagnosing incomplete resection or recurrence of cerebral neoplasms in humans. The characteristics of immediate postoperative CT images in dogs with intracranial pathology are unknown. This report describes findings from preoperative, immediate post-operative, and 4 week to 9 month follow-up CT examinations in two dogs with histologically-confirmed cerebral meningiomas. In images of one dog after surgery there was mild contrast enhancement of the tissue surrounding the surgical site. This enhancement had resolved in later images and was probably the result of surgically induced trauma. In post operative images of the other dog there was significant hyperattenuation of the tissues around the surgical site. In post contrast images there was increased enhancement that was evident in later images. These findings, although not supported by necropsy, probably indicate incomplete excision of the tumor.     

Anatomical evaluation of hepatic vascular system in healthy beagles using X-ray contrast computed tomography

Liver contrast X-ray computed tomography (CT) has been used for evaluation of hepatic vessels for liver transplantation, liver lobectomy, interventional radiology and diagnosis of hepatocellular carcinoma in humans. However, there remains scant available anatomical information on normal hepatic vessels in the veterinary field. In this study, visualization of hepatic vessels was evaluated in 32 normal beagle dogs by X-ray contrast CT using triple phase images. The following hepatic vessels were clearly visualized: arterial, portal and hepatic veins. With regards to the running patterns of the portal vein and hepatic vein, there were no significant differences between the dogs. However, the hepatic artery exhibited some differences in each dog. In particular, the hepatic artery of the quadrate lobe and the right lateral lobe had many running patterns. The results of the present study could be useful for veterinary diagnosis, surgery and interventional radiology.     

Pulmonary Artery Thrombosis in Experimental Angiostrongylus vasorum Infection Does Not Result in Pulmonary Hypertension and Echocardiographic Right Ventricular Changes

Background: Dogs experimentally inoculated with Angiostrongylus vasorum develop severe pulmonary parenchymal lesions and arterial thrombosis at the time of patency. Hypothesis: A. vasorum‐induced thrombosis results in arterial hypoxemia, pulmonary hypertension (PH), and altered cardiac morphology and function. Animals: Six healthy Beagles experimentally inoculated with A. vasorum. Methods: Thoracic radiographs and arterial blood gas analyses were performed 8 and 13 weeks postinoculation (wpi) and 9 weeks posttherapy (wpt). Echocardiography was done before and 2, 5, 8, 13 wpi and 9 wpt. Invasive pulmonary artery pressure (PAP) measurements were obtained 8 wpi. Two untreated dogs were necropsied 13 wpi and 4 treated dogs 9 wpt. Results: All dogs had patent infections at 7 wpi and clinical respiratory signs at 8 wpi. Moderate hypoxemia (median PaO₂ of 73 and 74 mmHg) present at 8 and 13 wpi had resolved by 9 wpt. Echocardiographically, no evidence of PH and no abnormalities in cardiac size and function were discernible at any time point. PAP invasively measured at 8 wpi was not different from that of control dogs. Severe radiographic pulmonary parenchymal and suspected thrombotic lesions at 13 wpi were corroborated by necropsy. Most histopathologic changes had resolved at 9 wpt, but focal inflammatory, thrombotic, and fibrotic changes still were present in all dogs. Conclusion: In experimentally infected Beagles, pulmonary and vascular changes induced by A. vasorum are reflected by marked radiographic changes and arterial hypoxemia. These did not result in PH and echocardiographic changes in cardiac size and function.     

Concentration of lipocalin region of collagen XXVII alpha 1 in the serum of dogs with hemangiosarcoma

Background: Hemangiosarcoma (HSA) is a common malignancy of dogs with characteristic early, aggressive metastasis. Diagnosis of HSA is challenging because of lack of sensitive and specific diagnostic tests. Hypothesis: Specific proteins that are increased in serum of dogs with HSA might represent useful biomarkers of the disease. Animals: Thirty‐four dogs with HSA and 42 healthy dogs from the Ontario Veterinary College Teaching Hospital. Methods: This case‐control study compared serum proteins in dogs with HSA and healthy dogs. Proteins were separated by 2‐dimensional difference gel electrophoresis and identified by liquid chromatography and tandem mass spectrometry. Results: Western blot analysis showed that serum collagen XXVII peptide concentration in serum of dogs with large metastatic HSA burdens (1,488, 231–3,754 DU; median, minimum‐maximum); was, on average, 9.5‐fold higher than in healthy dogs (156; 46–2,101 DU). While concentrations for dogs with osteosarcomas (678; 124–3,251 DU), lymphomas (423; 92–2,777 DU), carcinomas (1,022; 177–3,448 DU), and inflammatory disease were also increased, values were consistently lower than those for HSA. Receiver operating characteristic curves revealed an estimated area under the curve of 83% for HSA cases whereas areas for other neoplastic and nonneoplastic diseases were nondiscriminatory. Serum collagen XXVII peptide concentration before splenectomy (1,350; 1,156–1,929 DU) was reduced after tumor removal (529; 452–562 DU) and chemotherapy but increased in 2 dogs with tumor recurrence (511–945 DU; 493–650 DU). Conclusions and Clinical Importance: Collagen XXVII peptide might be useful for diagnosis and monitoring of advanced HSA.     

THREE-DIMENSIONAL HELICAL COMPUTED TOMOGRAPHIC ANGIOGRAPHY OF THE LIVER IN FIVE DOGS

The objective of this study was to develop a simple, safe, minimally invasive protocol to evaluate the hepatic vasculature. Five purpose-bred Beagle dogs underwent noncontrast-enhanced computed tomographic scan of the entire abdomen. A dynamic, nonincremental computed tomography scan at the level of T11 was then performed using a test bolus of contrast medium to determine time to peak opacification and to aid in the calculation of scan delay. The time to peak arterial enhancement ranged from 2.0 to 7.0 s, with a median of 2.0 s. The time to peak portal venous enhancement ranged from 23.0 to 46.0 s, with a median of 32.0 s. Scan delay for arterial opacification ranged from 0 to 5.0 s, with a median of 0 s. Scan delay for the portal phase of opacification ranged from 6.0 to 21.0 s, with a median of 17.0 s. Using this information, two separate computed tomographic studies were used to image the arterial and portal venous phases of circulatory opacification, respectively. The dogs were hyperventilated to prevent breathing motion during the scan, each of which required approximately 20 s. A power injector was used to inject diatrizoate meglumine (128 mg I/kg) through an 18-gauge cephalic vein catheter at a rate of 5 ml/s. Scanning was initiated after the appropriate scan delay to optimize the specific phase of vascular filling. Maximum intensity projections allowed clear delineation of the hepatic arteries and the portal venous system, while eliminating overlying structures that might interfere with image analysis. Time/density curves were generated, and the time needed for each study was recorded. Hepatic arteries and portal veins were clearly visualized in all dogs. Parenchymal opacification was also observed.     

CT characteristics of primary hepatic mass lesions in dogs

Little information is available on the relationship between computed tomography (CT) imaging findings and the pathologic diagnosis of canine hepatic tumors. Our purpose was to clarify the characteristic features of CT findings in liver tumors in dogs. Data from 33 dogs with either a hepatocellular carcinoma, n = 14, hepatocellular adenoma, n = 14, or nodular hyperplasia, n = 5 were summarized from medical records. CT features for each histologic diagnosis were characterized and analyzed statistically. Common findings in hepatocellular carcinoma included central (79%, P = 0.0030) and marginal enhancement (93%, P = 0.00043) in the arterial phase, cyst-like lesions (93%), capsule formation (93%), and hypoattenuation in the portal (86%), and equilibrium phases (93%). Hepatic adenoma was characterized by a characteristic diffuse enhancement pattern during the arterial phase (57%, P = 0.013), which was also found in nodular hyperplasia (60%), but never in hepatocellular carcinoma. Nodular hyperplasia was less likely to have a capsule structure (20%, P = 0.0087). Mass size was significantly smaller in nodular hyperplasia than in hepatocellular carcinoma and hepatic adenoma (P = 0.0033 and 0.038, respectively). Hyperattenuation in the arterial and the portal phase i.e. contrast retention, was more frequent in hepatic adenoma than in the other groups (P = 0.037 and 0.037, respectively). Nodular hyperplasia was more frequently isoattenuating in the equilibrium phase (P = 0.043).     

Evaluation of hepatosplanchnic circulation and intestinal oxygenation in dogs with a condition that mimicked septic shock induced by continuous infusion of a low dose of lipopolysaccharide

OBJECTIVE: To determine whether continuous infusion of a low dose of lipopolysaccharide (LPS) to induce a condition mimicking septic shock in dogs would affect systemic and hepatosplanchnic circulation and oxygenation. ANIMALS: 12 healthy adult Beagles. PROCEDURE: Dogs received a low dose of LPS (Escherichia coli O55:B5) by continuous IV infusion at a rate of 1 microg/kg/h for 8 hours. Systemic hemodynamics; systemic oxygenation; blood flow in the cranial mesenteric artery, common hepatic artery, and portal vein; intestinal and hepatic tissue blood flow; mesenteric oxygenation; and intramucosal Pco2 were examined before and at selected time points after onset of the LPS infusion. RESULTS: After onset of the LPS infusion, cardiac index increased and mean arterial pressure (MAP) and systemic vascular resistance decreased, which is characteristic of the hyperdynamic state in septic patients. Hepatosplanchnic blood flow increased during the hyperdynamic state. Intestinal Pco2 was increased even when blood flows increased. During the latter half of the experimental period, MAP was maintained but hepatosplanchnic blood flows decreased and intestinal Pco2 increased further. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of the results suggested that hepatosplanchnic blood flow enters the hyperdynamic state during the early stages of sepsis and that intestinal tissue oxygenation is threatened even when hepatosplanchnic blood flow is increased or maintained. Hence, improvement of hepatosplanchnic circulation and intestinal tissue oxygenation is important in dogs with clinical evidence of a septic condition.     

Quantitative evaluation of contrast enhanced transcranial Doppler signal using galactose based echo-contrast agent in dogs

Transcranial Doppler ultrasonography (TCD) is hindered by insufficient ultrasound penetration through the temporal bone. The use of echo-contrast agents to enhance the Doppler signal is an important step toward the solution of this problem. The aim of the present study was to investigate the tolerability and diagnostic value of the intravenous echo-contrast agent, Levovist. Levovist was administered intravenously in 8 dogs with two doses (0.2 and 0.3 ml/kg) at different concentrations (300 and 400 mg/ml). In right middle cerebral artery (RMCA), the duration and degree of the signal enhancement were measured by TCD. All 32 administrations of Levovist produced an increase in TCD signal of the RMCA without complications. The first assessable pulse curve could be seen on the screen after 4 to 7 seconds after injection. There was no significant difference of latency period between different concentration and dosage. The signal amplitude was increased homogeneously by more than 30 dB when 0.3 ml/kg with 300 mg/ml concentration of Levovist and 0.2 and 0.3 ml/kg with 400 mg/ml concentration were administered. There was no significant difference in the duration of optimal contrasting between 0.3 ml/kg with 300 mg/ml concentration of Levovist and 0.2 and 0.3 ml/kg with 400 mg/ml concentration. The duration of the signal enhancement was 144 to 422 seconds, depending on the degree of concentration and dose of administration. Optimal TCD signal enhancement of RMCA was obtained using 0.3 ml/kg with 300 mg/ml concentration of Levovist in dogs, which is considered to provide quality visualization.     

Plasma vascular endothelial growth factor concentrations in healthy dogs and dogs with hemangiosarcoma

Vascular endothelial growth factor (VEGF) is a dimeric glycosylated polypeptide growth factor with potent angiogenic, mitogenic, and vascular permeability-enhancing properties specific for endothelial cells. In humans, VEGF seems to play a major role in tumor growth, and plasma concentrations correlate with tumor burden, response to therapy, and disease progression. This study compared plasma VEGF concentrations in healthy client-owned dogs (n = 17) to dogs with hemangiosarcoma (HSA; n 16). Dogs with HSA were significantly more likely to have detectable concentrations of plasma VEGF (13/17) compared to healthy dogs (1/17; P < .001). The median plasma VEGF concentration for dogs with HSA was 17.2 pg/mL (range, < 1.0-66.7 pg/mL). Plasma VEGF concentrations in dogs with HSA did not correlate with stage of disease or tumor burden, but 1 dog had undetectable VEGF during chemotherapy that subsequently increased with disease progression.     

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.