The Great Vessels and Tributaries of the Heart of the Ringed Seal (Phoca hispida)

The ringed seal (Phoca hispida), as well as other seals, exhibit some unique anatomical properties when compared to their terrestrial counterparts. In the ringed seal, the most conspicuous adaptation is the aortic bulb, a large dilatation of the ascending aorta, which is comparable to that found in other seal species and marine mammals. Coronary arteries are similar to those of terrestrial mammals. The branches of the ascending aorta (brachiocephalic trunk, left common carotid artery and left subclavian artery) are similar to those of higher primates and man. The pulmonary trunk originates from the right ventricle near the ventral midline of the thorax. The peculiarities of the venous system are three pulmonary veins, a pericardial venous plexus, a caval sphincter, a hepatic sinus with paired caudal vena cavae and a large extradural venous system. Generally, three pulmonary veins (right, left, middle) empty into the left atrium. The right and left pulmonary veins drain the cranial and middle lung lobes of their respective lung, while the middle pulmonary vein drains both caudal lung lobes and the accessory lobe. The pericardial venous plexus lies on the pericardial pleura on the auricular (ventral) surface the heart. The azygous vein is formed from the union of right and left azygous veins near the 5th thoracic vertebra. The caval sphincter surrounds the caudal vena cava as it passes through the diaphragm. Caudal to the diaphragm, the vena cava is dilated excessively (the hepatic sinus) and near the kidneys it is biphid. Cardiovascular physiological studies have shown some of these anatomical variations, especially of the venous system and the ascending aorta, to be modifications for diving.     

Macroscopic Anatomy of the Great Vessels and Structures Associated with the Heart of the Ringed Seal (Pusa hispida)

The ringed seal [Pusa (Phoca) hispida], as well as other seals, exhibits unique anatomical properties when compared to its terrestrial counterparts. In the ringed seal, the most conspicuous marine adaptation is the aortic bulb. This large dilatation of the ascending aorta is comparable to that found in other seal species and marine mammals. The branches of the ascending aorta (brachiocephalic trunk, left common carotid artery and left subclavian artery) are similar to those of higher primates and man. The peculiarities of the venous system are: three pulmonary veins, a pericardial venous plexus, a caval sphincter, a hepatic sinus with paired caudal vena cavae and a large extradural venous plexus. Generally, three common pulmonary veins (right, left and caudal) empty into the left atrium. The pericardial venous plexus lies deep to the mediastinal pericardial pleura (pleura pericardica) on the auricular (ventral) surface of the heart. The caval sphincter surrounds the caudal vena cava as it passes through the diaphragm. Caudal to the diaphragm, the vena cava is dilated (the hepatic sinus), and near the cranial extremity of the kidneys, it becomes biphid. The azygos vein is formed from the union of the right and left azygos veins at the level of the 5th thoracic vertebra. Cardiovascular physiological studies show some of these anatomical variations, especially of the venous system and the ascending aorta, to be modifications for diving. This investigation documents the large blood vessels associated with the heart and related structures in the ringed seal.     

Descriptive anatomic study of the great vessels of the heart in the capuchin monkey Cebus apella (Linnaeus, 1758)

The aim of this study was to describe the anatomy of the great vessels of the heart in capuchin monkey (Cebus apella) and to compare with those of other primates, including humans. The hearts were prepared through fixation in 10% formalin and subsequently dissected using standard techniques and instruments. The arterial and venous systems were perfused with colored latex solution via the femoral vessels. An ascending cylindrical branch with relatively great caliber was identified in the aorta artery, in addition to an aortic arch, from which three great arteries were originated, the brachiocephalic trunk, the left common carotid artery and the left subclavian artery. After a course of variable extension, the pulmonary trunk divided into right and left pulmonary arteries. The caudal vena cava was morphologically similar to that of humans, except for its association with the cardiac lobe of the right lung, whereas the cranial vena cava was formed by the two braquiocephalic veins and received the azygos vein close to right atrium. The pulmonary veins, in number of six, ended at the posterior face of the left atrium, differently from both humans and other primates. In conclusion, the morphology of the great vessels of the heart in Cebus apella was similar to that of humans and other primates, although some differences are evidenced with regards to topography and number of anatomic structures, particularly the relationship of the caudal vena cava with the cardiac lobe of the right lung and the presence of six pulmonary veins in Cebus apella.     

Macroscopic Anatomy of the Ringed Seal [Pusa (Phoca) hispida] Lower Respiratory System

This investigation serves to document the normal anatomical features of the lower respiratory tract of the ringed seal [Pusa (phoca) hispida]. Evaluation of embalmed specimens and tracheobronchial casts showed that the right lung of this seal consists of four lobes while the left has only three lobes. The ventral margins of the lungs do not reach the sternum causing them to form the boundary of the broad recessus costomediastinalis. Lung lobation corresponds with bronchial tree division. Pulmonary venous drainage includes right and left common veins draining ipsilateral cranial and middle lung lobes, and one common caudal vein draining both caudal lobes and the accessory lobe. The right and left pulmonary arteries divide into cranial and caudal branches at the level of the principal bronchus. The ringed seal has three tracheobronchial lymph nodes. The trachea has an average of 87 cartilages that exhibit a pattern of random anastomoses between adjacent rings. The trachea exhibits to a small degree the dorsoventrally flattened pattern that is described in other pinnipeds. The tracheal diameter is smaller than that of the canine.     

Origin of the infrarenal part of the caudal vena cava in the pig

The vascular topography in the lumbar region of pig embryos and young fetuses was three-dimensionally reconstructed to study some controversial aspects of the origin and development of the infrarenal part of the caudal vena cava. Contrary to general belief, it was found that the supracardinal veins, which form the azygos veins in the thorax, do not take part in the construction of the caudal vena cava in the lumbar region. These veins do appear in the abdomen, but they are only involved in the formation of the lumbar and ascending lumbar veins. The infrarenal part of the caudal vena cava arises from the lumbar part of the right caudal cardinal vein. Whilst this venous pattern is established, the lumbar part of the left caudal cardinal vein disappears and its former location is occupied by large lymphatic connections between the cysterna chyli and the retroperitoneal mesenteric lymphatic sac. On the basis of these findings, a number of hypotheses on the development of anatomical variations of the caudal vena cava should be reconsidered.     

Cardiac musculature of the cranial and caudal venae cavae and the pulmonary vein in the fowl.

The cardiac musculature of cranial and caudal venae cavae and pulmonary vein was examined to clarify its distribution pattern in the fowl using both light and electron microscopies. The musculature was distributed from the heart to the root of subclavian vein in the cranial vena cava, to the cranial margin of the liver in the caudal vena cava, and to the left and right distal pulmonary veins in the pulmonary vein, respectively. Judging from the morphology and distribution pattern in the venous wall, the cardiac musculature in the fowl is thought to share the same phylogenic origin with that in mammals. The ultrastructure of cardiac myocytes including transitional cells in the cranial vena cava and the pulmonary vein resembled that of atrial myocytes. While, the typical specialized myocytes such as Purkinje fiber were found in the caudal vena cava of the fowl.     

Symptomatic partial anomalous pulmonary venous connection in a kitten

A 3-month-old intact female American Shorthair cat, with syncope and tachypnea, underwent cardiac examination which identified no heart murmur or gallop. Thoracic radiography disclosed mild generalized enlargement of the cardiac silhouette and a bronchial and interstitial pattern throughout the lungs. Echocardiography identified tubular structures near the left atrium. After agitated saline contrast imaging, persistent left cranial vena cava with unroofed coronary sinus was suspected. Computed tomography angiography showed the right cranial, right caudal and left caudal pulmonary veins draining into the coronary sinus and flowing into the right atrium. The left cranial pulmonary vein drained normally into the left atrium. Partial anomalous pulmonary venous connection (PAPVC) was diagnosed. The kitten was treated with diuretics but died of heart failure 2 months later. Permission for necropsy was not granted. This case represents symptomatic PAPVC in a kitten. Most pulmonary veins were connected abnormally with the coronary sinus. The prognosis was grave because of refractory heart failure.     

Ultrasonographic findings in a cow with ascites due to thrombosis of the caudal vena cava.

This case report describes a three-year-old Swiss Braunvieh cow with ascites due to thrombosis of the caudal vena cava. Ultrasonography verified the ascites and revealed dilatation of the abdominal portion of the caudal vena cava (4.8 cm). It was presumed that the caudal vena cava was occluded by a thrombus or by perivenous compression cranial to the dilatation. Post mortem findings included: a massive accumulation of fluid in the abdominal cavity; a 15 cm long thrombus in the subphrenic region of the caudal vena cava; multiple pulmonary abscesses; severe thrombosis of the pulmonary vasculature; hepatic congestion; oedematous abomasal folds; and severe thrombophlebitis of the left jugular vein and both udder veins, due to poor intravenous injection technique. Ascites caused by thrombosis of the caudal vena cava is rare because collateral routes of venous return, including the udder veins, are usually established. It was therefore concluded that the ascites was attributable to bilateral thrombosis of the udder veins.     

Diagnosis by ultrasonography of congestion of the caudal vena cava secondary to thrombosis in 12 cows

This paper describes the clinical, ultrasonographic, radiographic and postmortem findings in 12 cows with thrombosis of the caudal vena cava. The principal clinical signs were chronic bronchopneumonia and fever in 11 cows; one cow had epistaxis and one cow bled from the mouth; eight cows had anaemia and leucocytosis, and the clotting time for the glutaraldehyde test was markedly decreased in all the cows; in nine of the cows the activity of gamma-glutamyltransferase was high, suggesting chronic hepatic congestion. The most important ultrasonographic finding was congestion of the caudal vena cava attributable to thrombosis of the vein. In all the cows the caudal vena cava was round to oval on cross-section, rather than the normal triangular shape. The hepatic, splenic and portal veins were dilated in five, three and one cow, respectively. The results of radiography and endoscopy supported a diagnosis of bronchopneumonia, but there were radiographic changes in the diaphragmatic lung lobes that supported a diagnosis of vena caval disease in only four cows. Postmortem there was a thrombosis of the caudal vena cava in all the cows, and the thrombi were located in the thoracic, subphrenic and abdominal part of the caudal vena cava at the level of the liver in four, one and seven cows, respectively. In three cows, the thrombus was situated where a hepatic abscess had broken into the caudal vena cava, and in one cow it was at the site of a diaphragmatic abscess. In another cow, there was a fistula between the major bronchus of the right diaphragmatic lung lobe and the caudal vena cava where the thrombus was situated. Three cows had liver abscesses that had not broken into the caudal vena cava. There was severe bronchopneumonia in 11 of the cows, some of which also had multiple pulmonary abscesses.     

PNEUMOPERICARDIOGRAPHY IN THE NORMAL DOG

To define the normal radiographic anatomy of the canine heart and pericardial space as outlined by air, pneumopericardiography was performed in ten normal, anesthetized dogs using a percutaneously introduced pericardial catheter. Room air was injected to produce pneumopericardiums without causing cardiac tamponade, and radiographs were obtained using a vertical beam with the dogs positioned in right lateral (RLAT), left lateral(LLAT), dorsal (VD), and ventral (DV) recumbency. Selective and nonselective angiocardiography was used to confirm the identity of the outlined structures. The RLAT and LLAT positions provided more information than the DV or VD positions. Pericardial air consistently outlined a distinct interventricular sulcus and the recesses around the aorta and pulmonary artery. The right auricle, outlined along the cranial heart border ventral to the ascending aorta in both RLAT and LLAT positions, varied considerably in size. The RLAT position best outlined structures to the left of midline, including the left auricle, interventricular sulcus, outflow region of the right ventricle, and the origin of the pulmonary artery. The LLAT position best demonstrated structures to the right of midline, including the right atrium, proximal part of the cranial and caudal vena cavae, and ascending aorta. The considerable range of normal variation between dogs in this study must be considered in the interpretation of clinical pneumopericardiograms.     

Partial anomalous pulmonary venous connection with portosystemic shunt in a cat

A nine-month-old castrated male domestic shorthair presented for evaluation with a three-month history of hematuria. Portosystemic shunts and calculi within the bladder were suspected, and computed tomography angiography was performed. Computed tomography angiography identified an extrahepatic portosystemic shunt and a partial anomalous pulmonary venous connection, with the lobar vein of the right caudal lobe draining into the caudal vena cava. After anesthesia was administered to the cat, tachypnea and wheezing respiratory sounds were observed, and thoracic radiography revealed the right middle lung lobe atelectasis and an unstructured interstitial pattern in the left cranial lobe. Echocardiography showed left and right atrial enlargement and slight interventricular septal flattening in diastole. Based on these findings, cardiogenic pulmonary edema was suspected, and the cat was treated with furosemide. The clinical symptoms were resolved the next day. Closure of the extrahepatic portosystemic shunt was performed on days 47 and 157. Left atrial enlargement and interventricular septal flattening were attenuated after the procedure. At the time of writing this report (seventeen months after diagnosis), the cat exhibited no clinical signs, but subjective right atrial enlargement remained at approximately the same level. This report represents the first case of a partial anomalous pulmonary venous connection and a portosystemic shunt in a cat.     

Left Cranial Vena Cava in a Horse

A complete left cranial vena cava (LCVC) was found in a normal horse. The LCVC was well developed, but there was a complete absence of the right cranial vena cava. The azygous vein was normally distributed on the right side of the thoracic vertebral bodies but passed ventral to the aortic arch to empty into the cranial vena cava on the left close to the origin of the aortic arch. The LCVC passed over the dorsal aspect of the left atrium to reach the coronary sulcus on the caudal aspect of the heart. The LCVC opened into the right atrium via a 5 cm diameter orifice (orifice of coronary sinus). The vena cordis magna joined the LCVC 6 cm from the orifice of the coronary sinus. Complete dissection of the horse revealed no other developmental abnormalities. This case is compared with similar cases in the literature.     

Congenital Interruption of the Portal Vein and Caudal Vena Cava in Dogs: Six Case Reports and a Review of the Literature

Objective —To describe six dogs with congenital abnormalities involving the portal vein, caudal vena cava, or both.
Animals —Six client-owned dogs with congenital interruption of the portal vein or the caudal vena cava, or both.
Methods —Portal vein and caudal vena cava anatomy was evaluated by contrast radiography and visualization at surgery. Vascular casts or plastinated specimens were obtained in three animals.
Results —Portal blood shunted into the caudal vena cava in four dogs and the left hepatic vein in one. Two of these five dogs also had interruption of the caudal vena cava with continuation as azygous vein, as did an additional dog, in which the portal vein was normally formed. Portal vein interruption was present in 5 of 74 (6.8%) dogs with congenital portosystemic shunts evaluated at the Veterinary Teaching Hospital during the study period.
Conclusions —Serious malformations of the abdominal veins were present in more than 1 in 20 dogs with single congenital portosystemic shunts.
Clinical Relevance —Veterinarians involved in diagnosis and surgery for portosystemic shunts should be aware of these potential malformations, and portal vein continuity should be evaluated in all dogs before attempting shunt attenuation.     

Use of computed tomography and silicon endocasts to identify pulmonary veins with echocardiography

The pulmonary veins were identified from the silicone endocast heart models of 19 dogs. Although variation in the number of the more peripheral veins on each specimen existed, all of the casts had a consistency with regards to the most proximal coalescence of the pulmonary veins as they entered the body of the left atrium. That is, the confluence of the veins formed three ostia at the atrial entry point that consisted of 1) right cranial and right middle pulmonary lobe veins; 2) right caudal, accessory, and left caudal pulmonary lobe veins; and 3) both the left cranial and left caudal pulmonary lobe veins of the left cranial lung lobe. The location of these structures identified by the 3-dimensional endocasts were then used to assist in the identification of the pulmonary veins using computed tomography of 2 dogs. Slices were made that approximated those commonly performed during echocardiographic examination. Understanding which pulmonary veins are seen by echocardiography in the different imaging planes will permit prospective evaluations of pulmonary vein size and abnormal flow patterns.     

IMAGING DIAGNOSIS: AZYGOUS CONTINUATION OF THE CAUDAL VENA CAVA WITH AND WITHOUT PORTOCAVAL SHUNTING

The CT angiographic features of azygous continuation of an interrupted caudal vena cava in dogs with and without portocaval shunting are described. Azygous continuation of a discontinuous caudal vena cava is usually an incidental finding, not associated with portosystemic shunting. Identification of an associated portosystemic shunt will determine the need for surgical intervention. CT angiography provides a means for making this distinction and details the course and size of the anomalous vessels. Focal widening of the caudal vena cava on a VD thoracic radiograph should raise suspicion for azygous vein distension.     

COMPUTED TOMOGRAPHIC CHARACTERISTICS OF COLLATERAL VENOUS PATHWAYS IN DOGS WITH CAUDAL VENA CAVA OBSTRUCTION

Collateral venous pathways develop in dogs with obstruction or increased blood flow resistance at any level of the caudal vena cava in order to maintain venous drainage to the right atrium. The purpose of this retrospective study was to describe the sites, causes of obstruction, and configurations of venous collateral pathways for a group of dogs with caudal vena cava obstruction. Computed tomography databases from two veterinary hospitals were searched for dogs with a diagnosis of caudal vena cava obstruction and multidetector row computed tomographic angiographic (CTA) scans that included the entire caudal vena cava. Images for each included dog were retrieved and collateral venous pathways were characterized using image postprocessing and a classification system previously reported for humans. A total of nine dogs met inclusion criteria and four major collateral venous pathways were identified: deep (n = 2), portal (n = 2), intermediate (n = 7), and superficial (n = 5). More than one collateral venous pathway was present in 5 dogs. An alternative pathway consisting of renal subcapsular collateral veins, arising mainly from the caudal pole of both kidneys, was found in three dogs. In conclusion, findings indicated that collateral venous pathway patterns similar to those described in humans are also present in dogs with caudal vena cava obstruction. These collateral pathways need to be distinguished from other vascular anomalies in dogs. Postprocessing of multidetector‐row CTA images allowed delineation of the course of these complicated venous pathways and may be a helpful adjunct for treatment planning in future cases.     

RADIOGRAPHIC AND ANGIOGRAPHIC EVALUATIONS OF FERRETS EXPERIMENTALLY INFECTED WITH DIROFILARIA IMMITIS

Five ferrets of each sex were each inoculated with 15 third-stage infective larvae of Dirofilaria immitis to study radiographic and angiographic changes in the cardiopulmonary system following heartworm infection; 5 additional ferrets of each sex served as noninfected controls. Prior to inoculation and every 8 weeks thereafter until 40 weeks, the infected and noninfected ferrets were radiographed; angiographic examinations were done prior to necropsy. At necropsy, the worms in the heart, lungs, and associated vessels were counted, and lung histosections were prepared and examined for changes. Radiographic changes were seen in the right side of the heart and associated vessels of infected ferrets as compared with the noninfected ferrets, but changes were less prominent than those seen in heartworm-infected dogs and cats. The changes were primarily an increase in the size of the right side of the heart, especially the right atrium. Radiographically, no changes could be visualized in the pulmonary vascular system. Worms in the enlarged cranial vena cava, azygous vein, and left caudal lobar pulmonary artery of infected animals were delineated by angiography. Histologically, no changes were seen in the pulmonary vascular tissues.     

Budd–Chiari-like syndrome in a dog with a chondrosarcoma of the thoracic wall

Objective: To describe a dog with Budd–Chiari‐like syndrome secondary to caudal vena cava compression from a thoracic wall chondrosarcoma. Case summary: A 9‐year‐old spayed female Shetland Sheepdog cross with a recent history of non‐productive cough developed severe abdominal distension and dyspnea. Marked ascites and enlarged hepatic veins were identified with ultrasonography. At surgery, a right thoracic wall mass was found to be compressing the caudal vena cava. Fluid analysis of the ascites revealed a modified transudate with elevated protein concentration, consistent with Budd–Chiari‐like syndrome. Clinical signs resolved following thoracotomy and complete resection of the mass. New or unique information provided: Obstruction of venous blood flow can result from compression exerted by a space‐occupying thoracic wall mass on the caudal vena cava. Clinical resolution can be achieved with return of adequate venous circulation by removal of the mass and alleviation of the external pressure.     

Extensive venous thrombosis and hind-limb edema associated with adrenocortical carcinoma in a dog.

A 10-year-old, spayed female, mixed-breed dog was referred for evaluation of bilateral hindlimb edema and weakness. Abdominal ultrasonography showed increased echogenicity of the lumen of the caudal vena cava from the level of the urinary bladder to the level of the cranial pole of the right kidney. Bilateral saphenous venograms displayed numerous filling defects in the caudal vena cava, right external iliac vein, right femoral vein, and the right common iliac vein. Extensive venous thrombosis was diagnosed, and the animal was euthanized. Necropsy confirmed the presence of venous thrombosis and revealed a right adrenocortical carcinoma that had invaded the caudal vena cava.