Computed tomographic and magnetic resonance imaging features of canine segmental caudal vena cava aplasia

Computed tomographic reference ranges of intrathoracic caudal vena cava ratios in sedated adult dogs without cardiac, pulmonary, or hypovolemic disease

BACKGROUND

Radiographic assessment of the intrathoracic caudal vena cava (CVC) is commonly used to evaluate hemodynamic status in veterinary patients without and with pulmonary, pericardial, or right-sided cardiac diseases. Many of these patients are now commonly evaluated with computed tomography (CT) in both emergency and referral settings. Traditional radiographic ratios in dogs, particularly the CVC height/aorta height (CVC/Ao) ratio, are often extrapolated to CT in order to determine if the CVC is normal in size.

OBJECTIVES

The first goal of this retrospective study was to create an objective measurement method to evaluate the size of the CVC via CT. The second goal was to report normal CVC ratio values in both sagittal and transverse CT images.

METHODS

The traditional lateral radiographic CVC ratios were extrapolated to similar ratios obtained from sagittal CT images in stable, sedated adult canine patients without known cardiac or pulmonary disease. Additionally, new methods of canine CVC ratios using transverse CT images were defined using vessel height and area. Mean, standard deviation, and 95% confidence intervals (CIs) of the CVC ratios in transverse and sagittal CT images were calculated to determine normal reference ranges.

RESULTS

Ratio agreement from observers of different skill levels was moderate to excellent. Sagittal CT CVC/Ao mean was 1.07 ± 0.17 with a CI of 0.71.42. The mean and CI of transverse CT CVC/Ao height and area were 1.14 ± 0.27 and 0.781.44 and 1.36 ± 0.59 and 0.641.94, respectively.

CONCLUSIONS

Application of normal sagittal and transverse CT ratio values in canine patients with and without hypotension, pulmonary, pericardial, or right-sided cardiac diseases is necessary to determine the clinical usefulness of these ratios.

Case report: Application of three-dimensional technologies for surgical treatment of portosystemic shunt with segmental caudal vena cava aplasia in two dogs

This case report describes the application of three-dimensional (3D) technologies for the surgical treatment of portosystemic shunt (PSS) with segmental caudal vena cava (CVC) aplasia. Two client-owned dogs were diagnosed with PSS along with segmental CVC aplasia using computed tomography. Through 3D volume and surface rendering, the vascular anatomic anomaly of each patient was identified in detail. A patient-specific 3D vascular model was used for preoperative planning. According to the plan established based on the 3D rendered image and printed model, shunt occlusion was performed using cellophane banding in the first case. An ameroid constrictor was used in the second case. Both patients showed good recovery without any clinical symptoms or complications. The use of 3D technologies in small animals has many advantages, and its use in vascular surgery, as in these cases, is also a therapeutic option worth considering.

Dynamic Obstruction of an Anomalous Cavoazygos Vessel Associated with Interrupted Caudal Vena Cava in a Boxer Dog

•

A young boxer dog presented for intermittent weakness associated with exercise.

•

Dynamic physical exam findings and echocardiographic study were dependent on recumbency.

•

A diagnosis of interrupted caudal vena cava was made by computed tomography.

•

Positional obstruction of anomalous cavoazygos vessel by the diaphragm was noted.

•

Obstruction of anomalous vessel was associated with clinical signs.

Computed tomography diagnosis of a caval-azygos communication in a dog with cor triatriatum dexter

An 18-month-old Springer Spaniel was presented for investigation of ascites, exercise intolerance and suspected cor triatriatum dexter. Division of the right atrium into two separate chambers by an anomalous perforated membrane consistent with cor triatriatum dexter was confirmed during echocardiography. However, a routine agitated saline contrast (bubble) study yielded results that could not be explained by the congenital heart defect alone. Computed tomography angiography was performed and revealed a dilated ventral internal vertebral venous plexus and a short, dilated vessel in the midlumbar region redirecting blood flow away from the caudal vena cava and into the azygos vein. Balloon dilatation of the orifice within the cor triatriatum dexter membrane successfully reduced pressure within the caudal chamber of the right atrium and enhanced return via the caudal vena cava with subsequent resolution of clinical signs. This case report highlights the use of cross-sectional imaging in dogs with cor triatriatum dexter and unexpected contrast study results, as a means by which concurrent vascular anomalies may be identified.

Surgical treatment of an abnormally positioned right adrenal tumor on segmental caudal vena cava aplasia in two dogs

Segmental caudal vena cava (CVC) aplasia is a rare congenital vascular anomaly in dogs. Two dogs were diagnosed by CT imaging to have right adrenal tumors with concomitant segmental CVC aplasia. During surgery, a firm connection between the right adrenal gland and CVC was observed in both cases. The adrenal glands were found ventral to the CVC and the adrenal tumor was resected including the vascular wall. CVC venectomy for tumor removal will be required if the right adrenal gland is displaced in dogs with segmental CVC aplasia, even if there is no intravascular invasion.

Percutaneous Cava Stenting in a Dog with Symptomatic Azygos Continuation of the Caudal Vena Cava

This report describes the successful placement of a nitinol stent within the azygos continuation of the caudal vena cava in a 2-year-old, neutered female, English Bulldog with clinical and imaging signs related to venous return chronic obstruction, renal venous thrombi, and chronic renal insufficiency. This noninvasive, interventional radiology procedure was safe and clinically effective for the patient. The clinical signs were rapidly eliminated, and three years later, the patient is still in good clinical condition, with normal renal function. Venous stenting appears to be a useful, new, minimally invasive treatment option for symptomatic cavo-azygos vascular connection.

Case report - azygos vein drainage into the left atrium in a dog with cor triatriatum dexter and a patent foramen ovale

A 2-year-old Airedale terrier was presented with exercise intolerance since birth and newly developed chylous pleural effusion. Imaging procedures including echocardiography, cardiac magnetic resonance imaging, computed tomography, and selective angiography revealed an aberrant connection of the azygos vein and the left atrium, a membrane in the right atrium consistent with cor triatriatum dexter, and a patent foramen ovale with right-to-left shunt. Balloon dilation of the membrane in the right atrium seemed to result in transient improvement of exercise tolerance compared with the previous 2 years. When chylothorax relapsed after three months, the dog was euthanized. Necropsy confirmed the azygos vein to left atrial connection, the patent foramen ovale, and the cor triatriatum dexter.

CT variants of the caudal vena cava in 121 small breed dogs

Computed tomography is increasingly used as a treatment planning method in canine patients with diseases of the retroperitoneum, however, published information on normal variations in the caudal vena cava (CVC) are currently lacking. The objectives of this retrospective descriptive study were to characterize CVC variants using CT angiography in a sample of small breed dogs and localize the CVC bifurcations for each variant. Inclusion criteria were small breed dogs (weight ≤ 15) that underwent contrast-enhanced CT scans of the CVC, abdominal aorta, and CVC tributaries. A total of 121 small breed dogs were sampled. Four right-sided and one left-sided CVC variations were identified: normal (88/121, 72.7%), caudal-partial split (17/121, 14.0%), partial duplication (8/121, 6.6%), complete duplication (7/121, 5.8%), and left-sidedness (1/121, 0.8%). The mean lumbar vertebral levels of the CVC bifurcation were L6.39 ± 0.41, L5.70 ± 0.35, L4.39 ± 0.42, L2.74 ± 0.38, and L6.4 in the normal, caudal-partial split, partial duplication, complete duplication, and left-sidedness types, respectively. The location of the CVC bifurcation, the relationship between the aortic trifurcation and the CVC bifurcation, and the location of the bilateral deep circumflex iliac veins with respect to the CVC bifurcation were significantly different among the right-sided types (P ≤ .001). Bilateral deep circumflex iliac veins joined to the ipsilateral common iliac veins and the CVC in the caudal-partial split and duplication types, respectively. The results of this study indicated that canine CVC variants may be frequent and should be considered during surgery or diagnostic imaging of the retroperitoneum.

Diagnostic imaging for the assessment of acquired abdominal vascular diseases in small animals: A pictorial review

Advances in interventional radiology and surgical techniques now allow complex abdominal diseases to be more successfully treated in small animals. Abdominal vascular alterations, acquired as individual process or as complication of other lesions such as neoplasia, can be life-threatening or at least greatly limit curative interventions of underlying diseases. Computed tomography (CT) and high-definition ultrasonography are now readily available in veterinary referral centers. Yet, there is little information currently available on the use of these modalities for the diagnosis and characterization of these vascular alterations. The purpose of this article is to review the CT and ultrasonographic findings of acquired vascular diseases in the abdomen of dogs and cats, using both the veterinary and human medicine literature as references, and highlighting essential concepts through figures.

Common venous renal trunk in two dogs: Multidetector computed tomographic imaging findings

In dogs, variation in the branching pattern of renal veins is rare with only few patterns reported. This report describes two unusual anomalies of the renal vein branching patterns in two dogs. In dog 1, a common renal trunk drained both kidneys, in a T-shape pattern, in the caudal vena cava after a long right perirenal course. In dog 2, a common venous trunk branched cranially from the pre-renal segment of an azygos-caudal vena cava venous trunk and divided into the renal veins in a Y-shape pattern. Proper knowledge of the possible anatomical variations in renal venous drainage may be helpful during imaging assessment and surgical planning of several canine diseases involving the abdominal vasculature and retroperitoneal space.

Azygos continuation of the caudal vena cava with segmental aneurysm, lung lobe torsion and pulmonary thromboembolism in a dog

This case highlights the management and diagnostic evaluation of a dog with two individually rare conditions (lung lobe torsion and vena cava aneurysm) that ultimately resulted in fatal pulmonary thromboembolism.

Estimation of time to peak contrast enhancement of the aorta and liver for dual-phase computed tomography on the basis of contrast medium arrival time, injection duration, and injection technique in dogs

OBJECTIVE To evaluate the accuracy of estimating time to peak enhancement (TPE) of the aorta and liver parenchyma on the basis of contrast medium arrival time in the aorta, injection duration, and injection technique in dogs. ANIMALS 18 dogs of specific body weight categories (≥ 2 dogs/category) with no liver abnormalities detected via CT. PROCEDURES Dogs were randomly assigned within weight categories to receive contrast medium IV at a fixed injection rate (5 mL/s) or fixed injection duration (20 seconds). Time-contrast attenuation curves were generated from dynamic CT scans acquired at the hepatic hilus. Data collected for contrast medium arrival time and injection duration were used to estimate TPEs of the aorta and liver, and results were compared with the observed TPEs for the aorta and liver. RESULTS Contrast medium arrival time, injection duration, and injection technique were significantly associated with observed values for aortic TPE and explained 96.1% of variation in TPE. For the fixed rate technique, the regression equation for estimating aortic TPE was 0.8 × (injection duration + contrast medium arrival time) + 1.6. For the fixed duration technique, the regression equation changed by only the constant (-2.6). However, the hepatic TPE estimated from the 3 predictor variables was not significantly different from the mean of observed TPEs. CONCLUSIONS AND CLINICAL RELEVANCE Aortic TPE could be accurately estimated from contrast medium arrival time, injection duration, and injection technique in dogs with apparently healthy livers. The regression equations derived from this relationship can be used to improve the efficiency of dual-phase CT of the liver in dogs.

Computed tomography angiography of situs inversus, portosystemic shunt and multiple vena cava anomalies in a dog

A 5-year-old Shih Tzu was presented with intermittent vomiting and anorexia. Microhepatica and reversed position of the abdominal organs were observed on radiography. Ultrasonographically, portosystemic shunt (PSS) was tentatively diagnosed. Computed tomography (CT) revealed that the distended portal vein drained into the left hepatic vein. The caudal vena cava (CdVC) split postrenally and converged at the renal level. Cranial to this, the azygos continuation of the CdVC was confirmed. In the thorax, a persistent left cranial vena cava (CrVC) was found along with right CrVC. This is the first report of a dog with persistent left CrVC and multiple abdominal malformations. CT angiography was useful in evaluating the characteristics of each vascular anomaly and determining the required surgical correction in this complex case.

Comparison between bolus tracking and timing-bolus techniques for renal computed tomographic angiography in normal cats

Renal dual-phase computed tomograpic angiography (CTA) is used to assess suitability of feline donors prior to transplantation. A prerequisite for successful CTA is optimal synchronization between the arterial passage of contrast material and CT data acquisition. This retrospective study was conducted to compare quality of renal vascular enhancement at dual-phase CTA in normal cats between two techniques of timing of data acquisition: the timing-bolus and the bolus tracking method. Nine cats were scanned using the timing-bolus technique and 14 with the bolus tracking technique using otherwise similar scanning parameters in a 16-slice multidetector row CT scanner. The quality of enhancement of the renal vessels at the scanned arterial phase and venous phase was assessed both subjectively and objectively by three board-certified radiologists. Arterial enhancement was not observed at the scanned arterial phase in three of the nine cats with the timing-bolus technique but only 1 of the 14 cats with the bolus tracking technique. Early venous enhancement at the scanned arterial phase was common with the bolus tracking technique. Data acquisition was significantly faster with the bolus tracking technique. We conclude that the bolus tracking technique is a valid technique that could be integrated into the routine protocol for 16-detector row CT renal angiography in cats.

Computed tomography findings in portal vein aneurysm of dogs

In this retrospective study, the appearances of extrahepatic and intrahepatic portal vein aneurysms (PVAs) in dogs were evaluated using multidetector computed tomography (CT). Data from 3060 dogs that underwent abdominal CT were reviewed for focal portal vein dilatation. PVAs were detected in 15/3060 (0.49%) dogs. The bodyweights of dogs with PVAs were significantly higher than the bodyweights of dogs without aneurysms (P=0.0001). Male sex was also significantly associated with PVAs (OR=6.23). Boxers were predisposed to the development of PVA (OR=11.88). Extrahepatic PVAs were always located in the portal vein at the level of the gastroduodenal vein insertion and were saccular in 10/15 dogs and fusiform in 5/15 dogs. One dog had an additional intrahepatic aneurysm of the umbilical part of the left intrahepatic portal branch. No dogs had clinical signs related to the PVA(s), although one dog developed a portal vein thrombosis in the site of the aneurysm.

Imaging diagnosis-portal vein aplasia and interruption of the caudal vena cava in three dogs

Severe portal vascular anomalies have been reported previously accompanying azygos continuation of the caudal vena cava, polysplenia, and situs anomalies in dogs and people. Three dogs with portal vascular anomalies were identified by means of CT angiography as having portal vein aplasia with portal insertion into the caudal vena cava, azygos continuation of the caudal vena cava, and interruption of the pre-hepatic caudal vena cava. This information confirms that complex embryological defects may occur in patients presenting for congenital portosystemic shunt, and that CT angiography is a non-invasive method of completely evaluating these potentially non-surgical portal vascular anomalies.