Abdominal vascular sonography

Imaging of experimental venous thrombus by means of Doppler and CEUS techniques in dogs

Venous thrombosis has been widely studied in humans, but not in dogs. This study was designed to evaluate a venous thrombus in dogs, from creation to solution, by means of various ultrasonographic techniques. Nine healthy Beagle dogs were included in the study. The venous thrombus was formatted by puncturing the lumen of the external jugular veins and then, the veins were examined with B-mode, color Doppler, pulsed-wave Doppler, and contrast-enhanced ultrasound (CEUS) techniques, at regular intervals, within 210-270 min after venipuncture. Haemodynamic parameters were calculated at two different locations, before and after the site of the thrombus formation. The existence of a thrombus was confirmed by CEUS technique. Thrombus volume and echogenicity were evaluated. The results showed that the visualization of the venous thrombus by color Doppler modality was not feasible in some veins. The blood volume was the parameter that could more precisely indicate the presence or absence of a thrombus. In cases where thrombus volume was less than 0.001 cm3, it was impossible to detect its presence using haemodynamic parameters. The CEUS imaging depicted accurately the size and shape of an anechoic venous thrombus, even when its volume was 0.001cm3.

Ultrasonographic findings of abdominal thrombosis in dogs

ABSTRACT This retrospective case series study describes the clinical and vascular ultrasound findings of 26 dogs diagnosed with abdominal thrombosis. Images were selected based on the detection of intravascular echogenic thrombus or the absence of vascular flow on color Doppler, confirmed by surgery or necropsy. Images were acquired using the Mylab 40 model, with linear and microconvex multifrequency probes. All the reports were evaluated along with the corresponding images by a veterinary diagnostic imaging radiologist. The ultrasonographic aspects evaluated were echogenicity (92.3%), anechogenicity (7.7%), vascularization (11.5%), mineralization (15.4%), and recanalization (7.7%) of the thrombosis. The vascular and hemodynamic findings were dilation of the affected vein (57.7%), total occlusion of blood flow (30.8%), presence of turbulent flow (65.38%), and visualization of smoke signal (blood flow detected as moving echogenic points in dynamic bidimensional mode) (11.5%). Neoplasms (19 cases) and nephropathies (13 cases) were the most common clinical conditions in the affected dogs. Eleven cases of vascular invasion due to adrenal neoplasms were identified. The results indicate that the vascular ultrasound examination is an important method for diagnosis, as 23 of the 26 cases did not show any clinical signs of thrombosis.

Caudal vena cava collapsibility index in healthy cats by ultrasonography

ABSTRACT The objective of this study was to calculate the collapsibility index (CI) in a group of 15 healthy adult mixed breed cats via right hepatic intercostal ultrasound view. The minimal and the maximal diameters of the caudal vena cava (CVC) were obtained during inspiration and expiration, respectively, then CI was calculated. The mean diameter of the CVC was 0.5cm. The mean CI was 28±3% and CI was not significantly associated with gender. As in human medicine, there is a growing need for less invasive monitoring in small animal practice. The CI enables the assessment of estimated volemia without the need for a central venous catheter. This is the first reported study investigating CI in cats.

Aortic to caudal vena cava ratio measurements using abdominal ultrasound are increased in dogs with confirmed systemic hypertension

Chronically sustained systemic hypertension in dogs can damage the kidneys, eye, brain, heart, and vessels. In human medicine, systemic hypertension has been implicated as the most common risk factor for aorta dilation, which can progress to an aneurysm. Abdominal ultrasound has been commonly used to monitor the size of the abdominal aorta in people with systemic hypertension. In this retrospective cross-sectional abdominal ultrasound study, evaluation of the size of the abdominal aorta relative to the caudal vena cava was performed in 18 control dogs and 128 dogs with confirmed systemic hypertension. Preexisting conditions contributing to systemic hypertension in these dogs were renal disease, hyperadrenocorticism, diabetes mellitus, adrenal tumors, and previous administration of phenylpropanolamine or palladia. The abdominal aorta and caudal vena cava were assessed from longitudinal images cranial to the trifurcation with measurements made from outer border to outer border of the walls, being careful not to compress the caudal vena cava that would alter its size. Our hypothesis was the ratio of the diameter of the abdominal aorta to caudal vena cava would be higher in dogs with systemic hypertension compared to dogs with normal blood pressure. The mean abdominal aorta-caudal vena cava ratio was 1.028 in control dogs with a normal blood pressure and 1.515 in dogs with systemic hypertension. In dogs with confirmed systemic hypertension, the abdominal aorta was dilated compared to the caudal vena cava in the caudal abdomen. An increase in the abdominal aorta-caudal vena cava ratio in a dog should raise suspicion for the presence of systemic hypertension and prompt evaluation of blood pressure.

Vascular ultrasonographic findings in canine patients with clinically diagnosed phlebitis

Peripheral vein phlebitis (inflammation) is a relatively frequent complication in dogs, however, published information on the ultrasonographic characteristics is currently lacking. This prospective, observational study describes the ultrasound (US) characteristics of normal canine cephalic veins, and veins with clinical phlebitis. Correlations among US findings and between US findings versus time that the intravenous catheter was in place were investigated. Safety of the US procedure was evaluated. Fifty patients were prospectively recruited for the study and 18 met the final inclusion criteria. Each patient underwent daily US examinations and was assessed for multiple criteria (vascular wall appearance, compressibility, spontaneity of flow, color fill, and presence/absence of filling defects, flow contour, direction, non‐pulsatility). Characteristics of normal canine cephalic veins were as follows: smooth and thin wall, complete compressibility, no flow disturbances, no filling defects, smooth flow contours, and unidirectional, non‐pulsatile flow with no turbulence. Characteristics of cephalic veins with clinical phlebitis were as follows: wall thickening (83%), decreased compressibility (55%), filling defects consistent with intraluminal thrombus (55%), vessel wall hyperechogenicity (44%), and abnormal color Doppler flow (39%). Significant correlations were found between Doppler filling defects and compressibility, Doppler filling defects and presumed thrombosis, and compressibility and presumed thrombosis (P = .001, P = .001, P = .000, respectively). No correlation was found between the US findings and time the intravenous catheter was in place. Findings indicated that duplex and compressibility US are feasible and safe methods for characterizing and monitoring cephalic veins in dogs with clinical phlebitis.

Influence of immune-mediated hemolytic anemia on flow velocities in the portal vein and caudal vena cava measured by use of pulsed-wave Doppler ultrasonography in dogs

OBJECTIVE To compare blood flow velocities of the portal vein (PV) and caudal vena cava (CVC) measured by use of pulsed-wave Doppler ultrasonography in clinically normal dogs and dogs with primary immune-mediated hemolytic anemia (IMHA). ANIMALS 11 client-owned dogs admitted to a veterinary teaching hospital for management of primary IMHA and 21 staff- or student-owned clinically normal dogs. PROCEDURES Flow velocities in the PV and CVC at the porta hepatis were evaluated in conscious unsedated dogs with concurrent ECG monitoring; evaluations were performed before dogs with IMHA received heparin or blood transfusions. Three measurements of peak velocity at end expiration were obtained for each vessel, and the mean was calculated. Results were compared between IMHA and control groups. RESULTS Mean ± SD blood flow velocity in the CVC differed between control (63.0 ± 18.6 cm/s) and IMHA (104 ± 36.9 cm/s) groups. Variance in dogs with IMHA was significantly greater than that for the clinically normal dogs. No significant difference in blood flow velocity in the PV was detected between IMHA and control dogs. CONCLUSIONS AND CLINICAL RELEVANCE Higher blood flow velocities were detected by use of pulsed-wave Doppler ultrasonography in the CVC of dogs with naturally occurring IMHA and may be used to predict anemia in patients suspected of having IMHA.

Ultrasonographic Examination of Some Vessels in Dogs and the Characteristics of Blood Flow in These Vessels

The examination by Doppler ultrasonography provides haemodynamic information about blood flow velocity in a respective vessel. It specifies high- and lowresistance flow patterns. The aim of our study was to record the flow in a. carotis communis, a. femoralis and aa. renales in 16 adult clinically healthy dogs of small and medium size; characterize the types of vessels and also determine the pulsatility index (PI) and the resistive index (RI) of these vessels. The a. femoralis is a high-resistance vessel with a pronounced three-peak waveform. The aa. renales gives a typical picture of a low-resistance flow pattern. The characteristics of a. carotis communis involves different images of its branches a. carotis interna and a. carotis externa. In the investigated groups we observed a medium degree of pulsatility (atypical highresistance flow pattern with an absence of reverse flow). The mean measured values of indices for a. carotis communis were: left side PI 1.824 and RI 0.742; right side PI 1.891 and RI 0.746, and for aa. renales: PI 1.366 ± 0.04 and RI 0.684 ± 0.05.

Pulsed-wave Doppler ultrasonographic evaluation of hepatic vein in dogs with tricuspid regurgitation

This study was performed to identify the relationships between hepatic vein (HV) measurements, including flow velocity and waveform, using pulsed-wave (PW) Doppler ultrasonography, and the severity of tricuspid regurgitation (TR) in dogs. The study included 22 dogs with TR and 7 healthy dogs. The TR group was subdivided into 3 groups according to TR jet profile obtained by echocardiography. The hepatic venous waveform was obtained and classified into 3 types. A variety of HV measurements, including the maximal velocities of the atrial systolic, systolic (S), end ventricular systolic, and diastolic (D) waves and the ratio of the S- and D- wave velocities (S/D ratio), were acquired. TR severity was significantly correlated with the S- (r = −0.380, p = 0.042) and D- (r = 0.468, p = 0.011) wave velocities and the S/D ratio (r = −0.747, p < 0.001). Receiver operating characteristic curve analysis revealed the highest sensitivity and specificity for the S/D ratio (89% and 75%, respectively) at a threshold of 0.97 with excellent accuracy (AUC = 0.911, p < 0.001). In conclusion, PW Doppler ultrasonography of the HV can be used to identify the presence of significant TR and to classify TR severity in dogs.

B-Mode and pulsed Doppler sonography of kidney in healthy sheep according to age

Abstract: There is no standardization in the literature of kidney length in sheep at different ages, as there are few studies about the access with the Doppler triplex ultrasound for the renal vascularization in this species. Eighty healthy sheep of three age groups of Ile de France and White Dorper breed were used: 20 lambs, 30 yearlings and 30 adults (8 rams and 22 ewes). Renal healthiness of the animals was confirmed by serum biochemical tests of urea and creatinine, and by observation of renal architecture with conventional ultrasound, besides measurement of vital parameters. A portable ultrasound (My LabTM30 Vet Gold Esaote®, Esaote Healthcare) device was used, with a convex transducer with 3.5MHz frequency. After identification of the kidneys in two-dimensional mode, the measurement of length in the sagittal section was performed in all sheep (n=80). Then color Doppler was activated for visualization of renal and interlobar arteries of the right kidney, and the resistivity index (RI) of the yearlings (n=30) and ewes (n=22) was measured. Biochemical tests remained within normal limits and renal architecture was preserved. The values of the right and left renal length were different between the groups, increasing with age (4.34cm and 4.31cm in lambs; 6.08cm and 6.23cm in yearlings; 7.57cm and 7.37cm in adults, respectively). Median values of RI of the renal artery were statistically different (p<0.05) between the groups of yearlings (0.57) and ewes (0.52). The median RI of the interlobar artery was similar in yearlings (0.58) and ewes (0.54).

Testicular perfusion after standing laparoscopic peritoneal flap hernioplasty in stallions

Acquired inguinal herniation is a very common condition in stallions, usually leading to unilateral or bilateral castration to prevent future recurrence. Recently, several surgical techniques such as the standing laparoscopic peritoneal flap hernioplasty (SLPFH) have been developed to avoid herniation recurrence and also preserve the breeding activity of high economic value stallions. However, studies on SLPFH lack more comprehensive and systematic data about reproductive-related adverse effects and outcomes. The aim of this study was to evaluate whether SLPFH of the internal inguinal rings produces changes in the testicular blood flow in a 1-year follow-up. For that purpose, six healthy stallions were used and testicular blood flow was assessed before, 3, 6, and 12 months (T0, T3, T6, and T12) after the procedure. Blood flow was evaluated ultrasonographically, using the pulsed-wave color Doppler mode. Peak systolic velocity, end-diastolic velocity, the time-averaged maximum velocity, and the derived indexes (resistive index) and pulsatility index) of the testicular artery were measured in two localizations: in the spermatic cord and on the caudal epididymal edge of the testicle. On the spermatic cord, the peak systolic velocity of the testicular artery increased significantly at T12. However, on the epididymal edge location of the artery, the pulsatility and resistive indexes were decreased at T12 (P < 0.05). This pattern of blood flow was related to a hyperemic process. Furthermore, SLPFH might have compressed the spermatic cord, causing a slight occlusion of the testicular artery and triggering a compensatory hyperemia to compensate the deficit of blood flow that supplies the testes. The SLPFH of the internal inguinal ring affected the testicular perfusion in stallions in a 1 year follow-up, although there was no effect on sperm production during this time. The spectral Doppler ultrasound is a useful tool to asses the testicular perfusion after reproductive surgical procedure and provides information which anticipates vascular supply compromise of the stallion testicles.

Spectral analysis of femoral artery blood flow waveforms of conscious domestic cats

The qualitative and quantitative aspects of femoral artery blood flow waveform spectra were evaluated in 15 male and 15 female Persian and mixed breed domestic cats (Felis catus), which were healthy and not sedated, using duplex Doppler ultrasonography (DDU). Spectral Doppler demonstrated a biphasic characteristic in 16 (53.34%) of the animals evaluated, and a triphasic characteristic in the 14 (46.66%) remaining animals. The systolic blood pressure and heart rate values were within the normal range for the species. The quantitative parameters evaluated, based on the spectral Doppler, were as follows: systolic velocity peak (SVP), recent diastolic velocity peak (RDVP), end diastolic velocity peak (EDVP), mean velocity (MV), integral velocity time (ITV), artery diameter (AD), femoral flow volume (FFV), pulsatility index (PI), resistive index (RI), systolic peak acceleration time (AT) and deceleration time (DT). The respective mean values were: 36.41 ± 7.33 cm/s, 4.69 ± 0.90 cm/s, 10.74 ± 2.74 cm/s, 23.06 ± 4.86 cm/s, 3.91 ± 1.05 cm, 0.17 ± 0.04 cm, 0.11 ± 0.08 cm(3), 3.85 ± 0.19, 1.40 ± 0.20, 39.84 ± 7.38 ms, and 114.0 ± 22.15 ms. No significant differences were found between males and females. The analyses carried out on the femoral artery flow spectrum obtained by DDU showed that it is easy to use and highly tolerated in non-sedated, healthy cats. It appears that DDU may be a useful diagnostic technique, but further studies are needed to evaluate how it compares with invasive telemetric methodology or high-definition oscillometric waveform analytic techniques.

Gastrointestinal hemodynamics in dogs with nonfood induced atopic dermatitis

BACKGROUND

Canine atopic dermatitis can be a result of exposure to aeroallergens or trophallergens. Hemodynamic alterations occur in dogs with food hypersensitivity.

HYPOTHESIS/OBJECTIVES

To evaluate if hemodynamic alterations occur in dogs with NFICAD with lowered resistance to diastolic flow at fasting, after feeding, or both.

ANIMALS

Ten healthy dogs and 22 dogs with NFICAD were included from the hospital population.

METHODS

Blinded prospective study. Peak systolic velocity (PSV), end diastolic velocity (EDV), mean velocity (MV), pulsatility index (PI), resistive index (RI) and PSV/EDV ratio were measured at fasting for both arteries (cranial mesenteric artery [CMA], celiac artery [CA]) and at 40 minutes after feeding in CMA and at 60 minutes in CA. The results were analyzed statistically with a mixed model.

RESULTS

There was no difference detected between groups of dogs for any variable except EDV during fasting (P = .01).

CONCLUSIONS AND CLINICAL IMPORTANCE

There is no decrease in resistance in NFICAD to diastolic flow. This observation could be explained by the absence intestinal inflammation in NFICAD.

Normal Doppler velocimetry of renal vasculature in Persian cats

Renal diseases are common in older cats. Decreased renal blood flow may be the first sign of dysfunction and can be evaluated by Doppler ultrasound. But previous studies suggest that the resistive index (RI) has a low sensitivity for detecting renal disease. Doppler waveforms of renal and intrarenal arteries demonstrate decreased blood flow before there are any changes in the RI. The purpose of this study was to evaluate the normal Doppler flowmetrics parameters of renal arteries (RAs), interlobar arteries (IAs) and abdominal aorta (AO) in adult healthy, Persian cats. Twenty-five Persian cats (13 females and 12 males with mean age of 30 months and an age range 12-60 months) with normal clinical examinations and biochemical tests and normal systemic blood pressure were given B-mode ultrasonographies in order to exclude all nephropathies, including polycystic kidney disease. All measurements were performed on both kidneys. Both kidneys (n=50) were examined by color mapping of the renal vasculature. Pulsed Doppler was used to examine both RAs, the IAs at cranial, middle and caudal sites, and the AO. The RI was calculated for all of the vessels. Early systolic acceleration (ESA) of RA and IA was obtained with Doppler spectral analysis. Furthermore, the ratio indices between RA/AO, and IA/RA velocities were calculated. The mean values of peak systolic velocity (PSV) and the diameter for AO were 53.17±13.46 cm/s and 0.38±0.08 cm, respectively. The mean RA diameter for all 50 kidneys was 0.15±0.02 cm. Considering the velocimetric values in both RAs, the mean PSV and RI that were obtained were 41.17±9.40 cm/s and 0.54±0.07. The RA had a mean ESA of 1.12±1.14 m/s(2) and the calculated upper limit of the reference value was 3.40 m/s(2). The mean renal-aortic ratio was 0.828±0.296. The IA showed PSV and RI values of 32.16±9.33 cm/s and 0.52±0.06, respectively. The mean ESA of all IAs was 0.73±0.61 m/s(2). The calculated upper limit of the reference value was 2.0m/s(2). The mean renal-interlobar artery ratio was 1.45±0.57. The RI values obtained in this study were similar to values reported in the literature. Some conditions that lead to a decrease in compliance and to an increase in vascular resistance can affect the Doppler spectral waveforms without changes in RI. To our knowledge, there are no studies that were directed toward to the normal ESA values of the renal vasculature in Persian cats. This study introduced a new ratio between the PSV of the RA and the IA. This index was developed based on the well-known effects of Doppler on the detection of stenosis, regardless of the cause. Further studies are necessary to verify the hemodynamic behavior of this index under pathological conditions in cats as well as the effect of aging, nephropathies and systemic pressure on Doppler velocimetric parameters.

Spectral Doppler ultrasound in the major arteries of normal conscious immature micropigs

Spectral waveform analysis of blood flow velocity in the major arteries of six healthy, conscious immature micropigs was determined using Doppler ultrasonography. Doppler spectral tracings were recorded from the external iliac artery, femoral artery, and renal arcuate artery. Tracings were also taken from three parts of the common carotid artery and two parts of the abdominal aorta. Spectral Doppler parameters included peak systolic velocity, early diastolic velocity, peak systolic velocity-to-end diastolic velocity ratio, resistive index, and pulsatility index. In addition, the diameter of major arteries and indirect blood pressure were measured. These results from spectral Doppler analysis in major arteries may be useful as reference ranges in the future studies of vascular hemodynamics in immature micropigs.

Evaluation of Doppler ultrasonography for the measurement of blood flow in young loggerhead sea turtles (Caretta caretta)

The aim of this study was to identify ultrasound accessible blood vessels in the loggerhead sea turtle (Caretta caretta) and describe their Doppler waveform patterns, peak systolic velocity, mean velocity, systolic/diastolic ratio as well as pulsatility and resistive indices. B-mode, colour and pulsed-wave Doppler examinations were performed on 10 turtles. Flow measurements were recorded for the left and right aorta, epigastric and internal iliac arteries, and right hepatic vein. Additionally, the large blood vessels of three dead turtles were injected with latex and dissected for anatomical support. A parabolic flow velocity profile was observed in all arteries. The waveforms of the right and left aortic arteries showed an unusual pattern when compared with mammals. The hepatic vein flow velocity waveform of the loggerhead sea turtle was found to be similar to that in the dog, although the flow velocity in the C-wave was higher than that in the A-wave. The low resistance flow pattern observed suggests that the loggerhead sea turtle's organs require a continuous blood supply.

The sonographic search for portosystemic shunts

The diagnostic investigation of portosystemic shunts (PSS) has evolved over the last few decades, helping to understand and identify these vascular anomalies that affect many dogs and cats. Ultrasonography has become an important tool in small animals and high-resolution systems are now widely available. Several sonographic features are observed with the different types of congenital and acquired PSS. A systematic, stepwise approach is described to facilitate ultrasound diagnosis of PSS in small animals.

Effects of medetomidine on Doppler variables of major abdominal arteries in normal dogs

The purpose of this study was to evaluate the effects of medetomidine administration on the Doppler variables of abdominal arteries. The study population consisted of 20 healthy dogs. The haemodynamic effects of the medetomidine were defined using Doppler variables of the abdominal aorta, renal arteries, cranial mesenteric artery and celiac artery. The dogs were monitored continuously and different measurements were performed before medetomidine injection, at 10, 40 and 80 minutes after medetomidine medication and after atipamezole administration. Changes in the characteristic Doppler spectra of different vessels were more marked in the abdominal aorta, in which a greater reverse flow was found. There was a significant decrease in peak systolic velocity (PSV), end diastolic velocity (EDV), and mean velocity (MV) at ten minutes in every vessel studied and this effect persisted until atipamezole administration. Pulsatility index (PI) increased significantly in the abdominal aorta at ten minutes and persisted during the study until atipamezole administration. Resistive index (RI) did not vary significantly in any vessel. A significant decrease was found in flow volume of the abdominal aorta, the cranial mesenteric artery and the celiac artery at ten minutes, persisting until atipamezole administration. We conclude that medetomidine can be a good sedative in aiding sonographic evaluation of RI in all the abdominal vessels studied. On the other hand, the changes in other Doppler variables suggest that medetomidine administration causes significant hemodynamic differences between sedated and non-sedated dogs.

Pattern recognition and feature extraction of canine celiac and cranial mesenteric arterial waveforms: normal versus chronic enteropathy--a pilot study

In this pilot study, we hypothesize that waveform patterns of the celiac and cranial mesenteric arteries differ pre- and post-prandially in normal dogs compared to those with chronic enteropathy. We further suggest that it is possible to classify these findings according to the type of disease present. Eleven dogs with chronic enteropathy and eight normal dogs were examined. Doppler examinations were performed at times 0 (fasted), and at 20, 40, 60 and 90 min post-prandially. The waveform shapes were described and the following features were extracted: resistive and pulsatility index, mean maximum velocity, mean diastolic velocity, peak systolic velocity, early diastolic notch ratio and the deceleration time interval. Dogs with inflammatory bowel disease had either lower or absent flow at fasting in early diastole compared to the other groups. Resistive and pulsatility indices decreased during digestion in all groups except those with protein losing enteropathy. The increase in mean diastolic flow during digestion in affected dogs was either lacking (protein-losing enteropathy) or significantly lower (inflammatory bowel disease, P<0.05) compared to normal dogs. Dogs with chronic enteropathies had abnormal arterial waveform shapes and suboptimal increases in diastolic blood flow during digestion and these findings worsened with the severity of the histological lesions present. Doppler ultrasound of the celiac and mesenteric arteries has great potential to enhance our understanding of intestinal disease in conscious dogs.

Doppler sonography of the medial arterial blood supply to the coxofemoral joints of 36 medium to large breed dogs and its relationship with radiographic signs of joint disease

The medial arterial supply to 68 of the 72 coxofemoral joints of 36 medium to large breed dogs was examined ultrasonographically. The medial circumflex femoral artery and three branches were identified; the artery and its transverse branch were identified in all 68 joints, and the deep branch was identified in 61 joints, and the ascending branch was identified in 63. However, the acetabular and obturator branches were not identified. The pulsatility index, the mean velocity and the peak systolic velocity of the medial circumflex femoral artery were determined and associated with a radiographic score of degenerative coxofemoral joint disease and a lath distraction index (LDI). In joints with a LDI greater than 0.35, the pulsatility index was significantly lower (P=0.023) and its mean velocity was higher (P=0.005). However, no significant associations were observed in individual dogs when the measurements in both joints were taken into account.

ULTRASONOGRAPHIC DIAGNOSIS OF PORTOSYSTEMIC SHUNTING IN DOGS AND CATS

The value of ultrasonography was evaluated in 85 dogs and 17 cats presented with a clinically suspected portosystemic shunt (PSS). A PSS was confirmed in 50 dogs and nine cats (single congenital extrahepatic in 42, single congenital intrahepatic in 11, and multiple acquired in six). Six dogs and one cat had hepatic microvascular dysplasia, and 29 dogs and seven cats had a normal portal system. Ultrasonography was 92% sensitive, 98% specific, and had positive and negative predictive values of 98% and 89%, respectively, in identifying PSS, with an overall accuracy of 95%. When a PSS was identified with ultrasonography, extrahepatic, intrahepatic, and multiple acquired PSS could be correctly differentiated in 53/54 patients (98%). The combination of a small liver, large kidneys, and uroliths had positive and negative predictive values of 100% and 51% for the presence of a congenital PSS in dogs. The portal vein/aorta (PV/Ao) and portal vein/caudal vena cava (PV/ CVC) ratios were smaller in animals with extrahepatic PSSs compared with animals with microvascular dysplasia, intrahepatic PSSs and those without portal venous anomalies (P<0.001). All dogs and cats with a PV/Ao ratio of < or = 0.65 had an extrahepatic PSS or idiopathic noncirrhotic portal hypertension. Dogs and cats with PV/Ao and PV/CVC ratios of > or = 0.8 and > or = 0.75, respectively, did not have an extrahepatic PSS. Reduced or reversed portal flow was seen in four of four patients with multiple acquired PSSs secondary to portal hypertension. The presence of turbulence in the caudal vena cava of dogs had positive and negative predictive values of 91% and 84%, respectively, for the presence of any PSS terminating into that vein.

Pulsed-wave Doppler ultrasonographic evaluation of hepatic veins during variable hemodynamic states in healthy anesthetized dogs

OBJECTIVES

To quantify direction and velocity of blood flow in hepatic veins in dogs under different hemodynamic conditions by use of pulsed-wave Doppler ultrasonography.

ANIMALS

10 healthy dogs.

PROCEDURE

Dogs were anesthetized, and venous flow velocities in the quadrate lobe were measured. Arterial blood pressure, right atrial pressure, pulmonary artery pressure, and cardiac output were measured simultaneously. The timing of each waveform during the cardiac cycle was used to identify velocity profiles. Peak waveform velocities were measured during conditions of light anesthesia with isoflurane (baseline; period 1), cardiovascular depression following administration of high-dose isoflurane and esmolol i.v. (period 2), cardiovascular depression with crystalloid volume expansion (period 3), and high cardiac output induced with dobutamine (period 4). Hemodynamic measurements and maximum waveform velocities were compared among the 4 periods by use of an ANOVA and univariate and multivariate linear regression.

RESULTS

During each study period, 4 distinct, low-velocity waves were identified. Mean velocities recorded during period 1 were as follows: retrograde atrial contraction a-wave, 7.3 cm/s; antegrade systolic S-wave, 15.0 cm/s; retrograde venous return v-wave, 2.7 cm/s; and antegrade diastolic D-wave, 11.4 cm/s. Mean S:D ratio was 1.27. During periods 3 and 4, S-wave velocity increased; D-wave velocity was highest during period 4.

CONCLUSIONS AND CLINICAL RELEVANCE

Consistent hepatic venous velocity profiles were observed in healthy dogs under different hemodynamic conditions. These findings provide baseline values that may be useful in evaluating clinical cases, but further study involving healthy, awake dogs and dogs with cardiac and hepatic diseases is required.

Ultrasonographic findings in dogs with hyperammonemia: 90 cases (2000–2002)

OBJECTIVE

To determine ultrasonographic abnormalities in dogs with hyperammonemia.

DESIGN

Retrospective study.

ANIMALS

90 client-owned dogs with hyperammonemia.

PROCEDURE

Ultrasonography of the abdominal vessels and organs was performed in a systematic way. Dogs in which the ultrasonographic diagnosis was a congenital portosystemic shunt were included only if they underwent laparotomy or necropsy. Dogs in which the abdominal vasculature appeared normal and dogs in which the ultrasonographic diagnosis was acquired portosystemic shunts and portal hypertension were included only if liver biopsy specimens were submitted for histologic examination.

RESULTS

Ultrasonography excluded portosystemic shunting in 11 dogs. Acquired portosystemic shunts were found in 17 dogs, of which 3 had arterioportal fistulae and 14 had other hepatic abnormalities. Congenital portosystemic shunts were found in 61 dogs, of which 19 had intrahepatic shunts and 42 had extrahepatic shunts. Intrahepatic shunts originated from the left portal branch in 14 dogs and the right portal branch in 5. Extrahepatic shunts originated from the splenic vein, the right gastric vein, or both and entered the caudal vena cava or the thorax. Ultrasonography revealed splenic-caval shunts in 24 dogs, right gastric-caval shunts in 9 dogs, splenic-azygos shunts in 8 dogs, and a right gastric-azygos shunt in 1 dog.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that ultrasonography is a reliable diagnostic method to noninvasively characterize the underlying disease in dogs with hyperammonemia. A dilated left testicular or ovarian vein was a reliable indicator of acquired portosystemic shunts.

Simultaneous use of bilateral caudal superficial epigastric axial pattern flaps for wound closure in a dog

A neutered male German shorthaired pointer sustained severe bite wounds to the left caudal flank and thigh area. Thorough wound lavage and debridement was performed immediately and also three days after presentation. Daily wound dressing resulted in the production of a mature granulation tissue bed. Prior to wound closure, colour flow Doppler ultrasonography was used to confirm blood flow through the right and left caudal superficial epigastric arteries and veins. Sixteen days after presentation, right and left caudal superficial epigastric axial pattern flaps were simultaneously elevated to cover the defect. The right flap was elevated as an island flap, rotated 120 degrees and used to cover the caudodorsal aspect of the defect. The left flap was elevated and rotated dorsally to cover the cranioventral aspect of the defect. Ninety per cent wound coverage was achieved and flap survival was total. The donor site defect was closed primarily and no dehiscence occurred. Three months postsurgery, the entire defect was closed and limb function was normal.

Intraoperative ultrasonography of the portal vein during attenuation of intrahepatic portocaval shunts in dogs

A method for intraoperative measurement of portal blood flow velocity with duplex Doppler ultrasonography in 7 dogs with congenital intrahepatic portosystemic shunts is described. The aims of the study were to determine whether intraoperative ultrasonography was an acceptable alternative to mesenteric portography in such dogs and to identify quantitative portal hemodynamic variables that might correlate with clinical outcome better than portal pressure does. Ultrasonographic measurements did not influence decision-making by the surgeon, who attenuated the shunt on the basis of appearance of the viscera and change in mean systemic arterial blood pressure. All dogs recovered without complications, and surgery was considered to be successful in all 7. Intraoperative B-mode ultrasonography provided real-time information about the anatomy of the shunt and the portal branches, suggesting that it may be a useful alternative to mesenteric portography. The time-averaged mean portal blood velocity ranged from 6.5 to 33.7 cm/s before shunt attenuation and from 5.0 to 9.5 cm/s after shunt attenuation. This narrow range of postligation velocities suggested that intraoperative ultrasonography might be an alternative to intraoperative portal pressure measurement.

Changes in the Doppler waveform of the ovine femoral artery following infusion of vasoactive agents: a preliminary study

The aim of this study was to investigate whether femoral artery pulsatility index (PI) can be used as an indicator of vasomotor tone in the digit of an ungulate species by measuring the change in PI induced by infusion of vasoactive agents in halothane-anaesthetised sheep. Intra-arterial infusion of the vasoconstrictor phenylephrine (9 microg min(-1)) tended to increase waveform PI (3.89-6.24, n=4, P=0.100). Infusion of a low dose (3 microg min(-1)) of the vasodilator sodium nitroprusside did not alter femoral artery PI, however infusion of a higher dose (30 microg min(-1)) tended to increase PI (5.39-6.70, n=5, P=0.059). During these studies heart rate, mean ABP and p(a)CO(2) did not change significantly. The tendency for PI to increase in response to vasodilation was unexpected and the mechanism involved is unclear. It appears that femoral artery PI cannot be used to predict vasomotor tone in the digit of the anaesthetised sheep.

Portal hypertension in a dog due to circumscribed fibrosis of the wall of the extrahepatic portal vein

A two-and-a-half-year-old German shepherd dog with ascites and a high concentration of blood ammonia was investigated. Sonographically, its liver was normal but the portal vein was dilated and the flow of blood within it was slow. A liver biopsy showed that the liver was normal, and did not reveal any possible cause of portal hypertension or ascites. Postmortem, the cranial part of the portal vein was dilated with a cross-striped internal surface, but the caudal part looked normal; there was a stenotic ring between the normal and dilated parts. Histology of the dilated segment revealed marked hypertrophy of both the internal circular and the external longitudinal smooth muscle layers. At the site of the stenosis, the longitudinal muscular layer was replaced by connective tissue. Circumscribed fibrosis in the wall of the portal vein was responsible for the stenosis and the subsequent prehepatic portal hypertension. The cross-striped pattern in the dilated part of the vein was the result of hypertrophy of the inner circular smooth muscle layer.

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-ultrasonographic detection of retrograde pulsatile flow in the caudal vena cava of a puppy with cor triatriatum dexter

A three-month-old puppy had ascites, but its heart was normal by auscultation. Abdominal ultrasonography revealed an enlarged liver, distended hepatic veins and a distended caudal vena cava. Doppler ultrasonography detected retrograde flow in the caudal vena cava and abnormally pulsatile flow in the hepatic veins and caudal vena cava. A non-selective venogram was used to detect the path of the blood from the caudal vena cava. A postmortem examination showed that the puppy had cor triatriatum dexter and a defect in the atrial septum.

Doppler ultrasonographic diagnosis and anatomy of congenital intrahepatic arterioportal fistula in a puppy

A dilated, tortuous blood vessel was identified sonographically in the right medial liver lobe in a puppy with severe ascites. This vessel was thought to represent the dilated right medial portal vein branch. Using pulsed wave Doppler ultrasonography, retrograde, abnormally pulsatile flow was detected in both the dilated right medial portal vein branch and the main portal vein. The right medial liver lobe was surgically resected then fixed in formalin. Silicon rubber was injected and outlined the connection between the portal vein and hepatic artery.