Anatomy of the patent ductus venosus in the dog

The biplanar umbilical vein portovenograms of 49 newborn puppies and the biplanar mesenteric vein portovenograms, obtained during surgery, of 42 adult dogs with left divisional intrahepatic portosystemic shunts consistent with a patent ductus venosus (PDV) were reviewed. On the basis of the combined surgical, postmortem and imaging data, the left divisional intrahepatic portosystemic shunts were consistent, each having a straight vessel which drained into a venous ampulla before draining into the caudal vena cava at the level of the diaphragm. The left phrenic vein and the left hepatic vein both entered the ampulla independently of the shunting vessel. The morphology of the ductus venosus in the pups was similar and consistent with the morphology of the left divisional intrahepatic PDV shunt of the adult dogs. It is concluded that this form of left divisional shunt is correctly named a PDV and is the result of the persistence of the fetal ductus venosus. From the surgical records it is concluded that all the shunts described as a PDV were attenuated by the direct manipulation of the ductus venosus before its entry into the ampulla.     

Anatomy of the patent ductus venosus in the cat

The biplanar mesenteric vein portovenograms of 10 cats with left divisional intrahepatic portosystemic shunts consistent with a patent ductus venosus (PDV) were reviewed. A corrosion cast of the hepatic portal vasculature was made post mortem from one individual that died post operatively following surgical attenuation of the shunting vessel. On the basis of the combined surgical, post mortem and imaging data, these left divisional shunts were found to have consistent anatomy, each having a straight vessel which drained into a venous ampulla before draining into the caudal vena cava at the level of the diaphragm. The left phrenic vein and left hepatic vein both entered the ampulla independently of the shunting vessel. The anatomical similarity between these findings in the cat and the PDV in the dog suggest that it is appropriate to describe this particular portosystemic shunt as a PDV.     

Anatomy of the Ductus Venosus in Neonatal Dogs (Canis familiaris)

Anatomical features of the ductus venosus in 84 neonatal dogs are described. The ductus venosus was a straight conduit 1–3 mm wide and 4–12 mm long in pups with a crown-rump length of 80–200 mm. It arose from the left main portal vein branch opposite the umbilical vein, passed between the left lateral liver lobe and the papillary process of the caudate lobe, and terminated in the dorsal aspect of the proximal part of the left hepatic vein. The left hepatic vein was dilated at this point. There was no variation in the location of the ductus venosus in the animals studied.     

INTRAHEPATIC VENOUS COLLATERALS PREVENTING SUCCESSFUL STENT-SUPPORTED COIL EMBOLIZATION OF INTRAHEPATIC SHUNTS IN DOGS

The purpose of the following study was to evaluate stent-supported coil embolization of the hepatic vein in combination with antithrombotic treatment as a method for treatment of intrahepatic shunts, and to describe the complications associated with this procedure. Seven dogs with an intrahepatic shunt were included in a prospective clinical trial. A stepwise procedure was performed. First intervention: transjugular retrograde portography and stent implantation into caudal vena cava; second intervention: hepatic vein embolization combined with an antithrombotic treatment; third intervention in dogs with residual shunting: hepatic vein embolization without antithrombotic treatment. A right shunt was found in one dog and a left shunt in six dogs. Primary intrahepatic venous collaterals were found in one dog and hepatic vein embolization was not performed. Stent implantation into the caudal vena cava was performed in the other six dogs. There was no stent migration or thrombosis. Following the first coil intervention two dogs died due to vessel laceration while removing an oversized or migrated coil. On follow-up the shunt was completely closed in one dog. Secondary intrahepatic venous collaterals developed after the first or second coil intervention in two and one dog, respectively. In conclusion, stent-supported coil embolization of the hepatic vein in combination with an antithrombotic treatment was of limited success because primary or secondary intrahepatic venous collaterals tend to occur.     

Transportal Approach for Attenuating Intrahepatic Portosystemic Shunts in Dogs

A novel surgical approach, using portal venotomy during total hepatic vascular occlusion, was used to locate and attenuate congenital intrahepatic portosystemic shunts in nine dogs. Shunt location was consistent with a persistent ductus venosus in only two dogs. In the remaining seven dogs the shunts were window-like orifices arising from either the left (two dogs) or right portal vein branch (five dogs) and communicating with the ipsilateral hepatic vein or caudal vena cava. The transportal approach using total hepatic vascular occlusion consistently provided good access to the portosystemic shunts, including those with window-like communications. A 7 to 16 minute period of total vascular occlusion was well-tolerated hemodynamically, with few intraoperative complications. Intrahepatic shunts were successfully attenuated in eight dogs, while one dog with portal atresia was euthanatized. The postoperative course was complicated by high protein pulmonary edema (one dog), an encapsulated biliary pseudocyst (one dog) and uncontrollable hemorrhage caused by an uncharacterized coagulopathy (one dog). Three dogs required a second operation to further attenuate their shunts. The clinical condition of all seven surviving dogs was improved after surgery.     

Intracaval Repair of a Persistent Ductus Venosus in a Dog

A persistent ductus venosus was diagnosed in a 4-month-old Old English sheepdog. Total occlusion of blood flow to the liver was achieved through heparinization, hepatic artery occlusion, and placement of bypass cannulas from the portal vein and caudal vena cava to the right atrium. Intracaval closure of the ductus venosus then was accomplished. Despite postoperative complications of continued hemorrhage and acute renal uremia, the animal recovered. The neurologic abnormalities exhibited before surgery resolved, and the dog became more active and gained weight. The dog died due to undetermined causes three months after surgery. The ductus venosus was found to be closed, and the liver was markedly increased in size at necropsy.     

Hepatoencephalopathy associated with situs inversus of abdominal organs and vascular anomalies in a dog.

Throughout its life, a 1-year-old Doberman Pinscher dog had had gastrointestinal disorders and episodes of circling. It was less active than its littermates, and it usually seemed lethargic. When 3 months old, the pup had been anesthetized for ear cropping and it had remained anesthetized for 32 hours. Behavioral problems were apparent when the dog was 11 months old. Two weeks later the behavioral problems accentuated to the point that the dog developed "temper tantrums" and became aggressive toward its owner. On the basis of clinicopathologic and contrast radiographic findings, hepatoencephalopathy due to persistent patent ductus venosus was diagnosed and the dog was euthanatized. Situs inversus abdominalis and multiple vascular anomalies were found at necropsy. Gross and microscopic studies of the viscera were correlated with corrosion casts of the vasculature. In addition to changes in organ position, 3 spleens and malformation of the pancreas were observed. Vascular anomalies were: (1) The portal vein was contiguous with the common hepatic vein by way of a patent ductus venosus; branches of the portal vein were not given off to the liver; (2) the caudal vena cava was continued by the azygos vein, and a cranial segment of the caudal vena cava was absent; (3) the hepatic artery was larger than normal; (4) the left gastric artery arose anomalously from the cranial mesenteric artery; and (5) histologic and radiographic study of the liver did not reveal any interlobular branches of the portal vein; however, hypoplastic branches of the gastroduodenal vein did enter the liver and were demonstrated on a corrosion cast.     

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.     

Left hepatic vein attenuation for treatment of patent ductus venosus in a dog

Patent ductus venosus was identified in a young dog. Surgical attenuation of the anomalous vessel was performed by partial ligation of the left hepatic vein. Clinical signs resolved after surgery, and laboratory values returned to normal. Jejunal venous portography, performed 8 weeks after surgery, revealed complete occlusion of the patent ductus venosus, with normal portal vasculature to the right and central divisions of the liver. Atrophy of the left hepatic division resulted.     

Doppler ultrasonographic assessment of closure of the ductus venosus in neonatal Irish wolfhounds

The normal appearance and closure time of the ductus venosus of 22 neonatal Irish wolfhounds from three unrelated litters were determined by repeated two-dimensional, grey-scale and colour-flow Doppler ultrasound examinations. A left intercostal approach was used to identify the ductus venosus, which appeared as a parallel-sided or cone-shaped vessel connecting a left-sided intrahepatic branch of the portal vein with a confluence of veins on the cranial aspect of the liver. Doppler signals indicative of patent ductus venosus were obtained in nine of nine puppies on day 2, 11 of 17 on day 4, five of 22 on day 6, none of nine on day 9 and none of eight on day 10.     

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.     

Imaging diagnosis--Complex intrahepatic portosystemic shunt in a dog.

An unusual form of congenital intrahepatic portosystemic shunt was identified in a 3 1/2-month-old female Labrador Retriever with neurologic signs. Ultrasonography and contrast-enhanced computed tomography were used to characterize the shunt morphology. An unusual, looping right-divisional shunt connected back to the portal vein that formed an ampula in the right-central portion of the liver. An irregularly shaped window-like opening connected the combined right-divisional loop and aneurysmal portal vein, and the caudal vena cava, while this vascular pool gradually fused more cranially. Imaging features of this complex vascular anomaly, which has not been previously reported, are presented.     

IMAGING DIAGNOSIS—COMPLEX INTRAHEPATIC PORTOSYSTEMIC SHUNT IN A DOG

An unusual form of congenital intrahepatic portosystemic shunt was identified in a 3½-month-old female Labrador Retriever with neurologic signs. Ultrasonography and contrast-enhanced computed tomography were used to characterize the shunt morphology. An unusual, looping right-divisional shunt connected back to the portal vein that formed an ampula in the right-central portion of the liver. An irregularly shaped window-like opening connected the combined right-divisional loop and aneurysmal portal vein, and the caudal vena cava, while this vascular pool gradually fused more cranially. Imaging features of this complex vascular anomaly, which has not been previously reported, are presented.     

ACQUIRED PORTAL COLLATERAL CIRCULATION IN THE DOG AND CAT

We describe patterns of acquired portal collateral circulation in dogs and in a cat using multidetector row computed tomography angiography. Large portosystemic shunts included left splenogonadal shunts in patients with portal hypertension. Small portal collaterals were termed varices; these collaterals had several patterns and were related either to portal vein or cranial vena cava obstruction. Varices were systematized on the basis of the venous drainage pathways and their anatomic location, namely left gastric vein varix, esophageal and paraesophageal varices, gastroesophageal and gastrophrenic varices, gallbladder and choledocal varices, omental varices, duodenal varices, colic varices, and abdominal wall varices. As reported in humans and in experimental dog models, esophageal and paraesophageal varices may result from portal hypertension that generates reversal of flow, which diverts venous blood in a cranial direction through the left gastric vein to the venous plexus of the esophagus. Blood enters the central venous system through the cranial vena cava. Obstructions of the cranial vena cava can lead to esophageal and paraesophageal varices formation as well. In this instance, they drain into the azygos vein, the caudal vena cava, or into the portal system, depending on the site of the obstruction. Gallbladder and choledocal varices, omental varices, duodenal varices, phrenico-abdominal varices, colic varices, abdominal wall varices drain into the caudal vena cava and result from portal hypertension. Imaging plays a pivotal role in determining the origin, course, and termination of these vessels, and the underlying causes of these collaterals as well. Knowledge about these collateral vessels is important before interventional procedures, endosurgery or conventional surgery are performed, so as to avoid uncontrollable bleeding if they are inadvertently disrupted.     

Cellophane banding of congenital intrahepatic portosystemic shunts in two Irish wolfhounds

Two three-month-old, male Irish wolfhound siblings were diagnosed with breed-typical left divisional congenital intrahepatic portosystemic shunts consistent with patent ductus venosus. The shunts were amenable to surgical dissection at a posthepatic location. Both dogs had cellophane banding for shunt attenuation. One dog was euthanased after developing post-ligation neurological dysfunction, which was refractory to treatment. The other dog survived and demonstrated shunt attenuation. Successful surgical management using cellophane banding of a patent ductus venosus has not been previously described in a large-breed dog.     

Complex extrahepatic portocaval shunt with unusual caval features in a cat: computed tomographic characterisation

A two-year-old, neutered male domestic shorthair cat was evaluated for a history of urate calculi, and neurologic signs. Diagnostic imaging revealed an elongated and tortuous single extrahepatic portosystemic shunt which appeared to receive normal tributaries of the caudal vena cava. Surgical correction of the shunt was carried out using cellophane banding. Eight months following surgery, clinical signs had resolved. Computed tomographic angiography allows thorough, rapid imaging of complex vascular anomalies to aid proper surgical correction. Errors in the formation of the portal vein and caudal vena cava can produce complex anomalies of the abdominal vasculature. Persistence of the embryologic left subcardinal vein is proposed to account for the lesion.     

Ultrasonographic evaluation of partially attenuated congenital extrahepatic portosystemic shunts in 14 dogs

Doppler ultrasonography was used to evaluate the portal vein in 14 dogs before, immediately after and four weeks after a partial ligation of a congenital extrahepatic portocaval shunt. By four weeks after the operation, the hepatofugal or zero flow in the portal vein segment cranial to the shunt origin had become a hepatopetal flow in 13 of the dogs, which became clinically healthy. The other dog continued to have a hepatofugal flow in the portal vein cranial to the origin of the shunt and continued to show clinical signs of hepatic encephalopathy. The shunt remained functional in six of the dogs, and three of them developed portosystemic collaterals in addition. In the other eight dogs the patent shunt was non-functional, because a hepatopetal flow was detected in the shunt adjacent to the portal vein. This flow was the result of the splenic vein entering the shunt, and the splenic blood dividing; some flowed via the shunt towards the portal vein, preventing the portal blood from shunting, and the rest flowed via the attenuated shunt segment to the caudal vena cava. Shunting of the splenic venous blood was clinically insignificant.     

Catheterization of the caudal vena cava via the lateral saphenous vein in the ewe, cow, and gilt: an alternative to utero-ovarian and medial coccygeal vein catheters

Current methods for obtaining venous blood from the reproductive organs of livestock often have a low rate of success or involve intensive surgical procedures that may impair ovarian function. Therefore, the caudal vena cava was catheterized via the lateral saphenous vein to determine the feasibility of using this method for chronic sampling of blood draining from the reproductive organs of ewes (n = 6), cows (n = 6), and gilts (n = 7). Blood samples were collected at 2-cm (ewes and gilts) or 5-cm (cows) intervals during insertion of catheters. Correct placement, defined as the position at which plasma concentrations of progesterone or estrogen were at least threefold greater than in jugular venous plasma, varied among species and among animals within species. It seemed, however, that a majority of catheters would be placed correctly if secured at 48 to 52 cm in ewes, 52 cm in gilts, and 90 to 100 cm in cows. Saphenous vein catheters were secured for sequential sampling of vena caval blood during the follicular phase of ewes (n = 25), cows (n = 4), and gilts (n = 5). Catheters remained patent for the duration of sampling in all individuals. Concentrations of estrogen in jugular and vena caval plasma were correlated (ewe P less than .0003; cow P less than .0001; gilt P less than .0001). Profiles of progesterone and estrogen revealed an episodic pattern of secretion in vena caval but not jugular plasma. Catheterization of the vena cava via the saphenous vein is a relatively simple and noninvasive method for obtaining blood containing uterine and ovarian hormones before their metabolism.     

Partial anomalous pulmonary venous connection in a dog

A 2-year-old male intact Belgian Malinois was presented for exercise intolerance. A grade III/VI left basilar systolic murmur was detected. Echocardiography revealed moderate right atrial and ventricular dilation and increased pulmonic outflow velocity. Thoracic radiographs showed right heart enlargement and a dilated caudal vena cava. In addition, on the left lateral projection, an enlarged aberrant right cranial pulmonary lobar vein was suspected to be diverging ventrally from the course of the right cranial lobar bronchus and inserting more ventrally than normal in the region of the right atrium. A left-to-right pulmonary vascular shunt was suspected, and the patient underwent further diagnostics under general anesthesia. An agitated saline study was positive, suggestive of a concurrent right to left shunt. A right heart catheterization was performed. Angiography was inconclusive. Oximetry testing revealed an increase in oxygen saturation within the right atrium at the level of the caudal cava supportive of a left-to-right shunt in this region. Computed tomography angiography revealed a large single pulmonary vein that anomalously entered into the caudolateral aspect of the right atrium (left-to-right shunt) and was suspicious for a small arteriovenous malformation between the right caudal pulmonary artery and the right pulmonary vein returning to the left atrium (right to left shunt). The patient was diagnosed with a partial anomalous pulmonary venous connection and a possible arteriovenous malformation.     

USE OF TRANSSPLENIC INJECTION OF AGITATED SALINE AND HEPARINIZED BLOOD FOR THE ULTRASONOGRAPHIC DIAGNOSIS OF MACROSCOPIC PORTOSYSTEMIC SHUNTS IN DOGS

We describe the use of ultrasonography‐guided percutaneous splenic injection of agitated saline and heparinized blood for the diagnosis of portosystemic shunts (PSS) in 34 dogs. Agitated saline mixed with 1 ml of heparinized autologous blood was injected into the spleen of 34 sedated dogs under sonographic guidance. The transducer was then sequentially repositioned to visualize the portal vein, the caudal vena cava, and the right atrium through different acoustic windows. It was possible to differentiate between intrahepatic and extrahepatic shunts depending on the entry point of the microbubbles into the caudal vena cava. Portoazygos shunts and portocaval shunts could be differentiated based on the presence of microbubbles in the caudal vena cava and/or the right atrium. In one dog, collateral circulation due to portal hypertension was identified. In dogs with a single extrahepatic shunt, the microbubbles helped identify the shunting vessel. The technique was also used postoperatively to assess the efficacy of shunt closure. All abnormal vessels were confirmed by exploratory laparotomy or with ultrasonographic identification of the shunting vessel. Ultrasound‐guided transsplenic injection of agitated saline with heparinized blood should be considered as a valuable technique for the diagnosis of PSS; it is easy to perform, safe, and the results are easily reproducible.