Thrombosis of the caudal vena cava presenting as an unusual cause of an abdominal mass and thrombocytopenia in a dog

Thrombosis of the caudal vena cava in a dog secondary to metastatic neoplasia is described. The dog had a palpable abdominal mass and persistent thrombocytopenia due to a thrombosed caudal vena cava that was surgically removed. A few days after its removal, the dog died and neoplastic cells of neural crest origin were identified at the edge of the thrombus. Massive thrombosis can be an unusual cause of platelet consumption, leading to thrombocytopenia and disseminated intravascular coagulation. Deep vein thrombosis of the vena cava can occur in dogs and may mimic an abdominal mass. Multiple mechanisms may be involved in the development of venous thrombosis, including endothelial damage by neoplastic cells and the presence of a hypercoagulable state secondary to neoplasia. Extensive collateral circulation may allow removal of diseased vena cava.     

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.     

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.     

Ultrasonographic measurement of caudal vena cava to aorta ratios for determination of volume depletion in normal beagle dogs

A noninvasive method for quantifying hydration status would be helpful for clinical management and for research applications in dogs. This prospective, experimental, pilot study aimed to assess the feasibility of ultrasonographic measurement of the caudal vena cava to aorta ratio as a method for quantifying volume depletion in dogs. In 12 normal beagle dogs, furosemide was administered intravenously at a dose of 1 mg/kg, every 2 h, for 8 h, to induce consecutive volume depletion. Every 30 min after administration, ultrasonographic images of the caudal vena cava and aorta, and physical and biological parameters related to dehydration were acquired. On transverse and longitudinal planes of caudal vena cava and aorta images, the height and area of the caudal vena cava and aorta were measured to calculate the caudal vena cava/aorta ratios. All images were acquired by approaching from the right intercostal space with the dogs in left lateral recumbency. A negative correlation was present between the percentage of weight loss in dogs and all four investigated caudal vena cava/aorta ratios (transverse plane width of the caudal vena cava [TW]/aorta; transverse plane height of caudal vena cava [TH]/aorta; longitudinal plane area of the caudal vena cava [TA]/aorta; and longitudinal plane maximal height of the caudal vena cava [L]/aorta). Significant differences (P < 0.001) were seen between dogs with and without clinical signs of dehydration for all caudal vena cava/aorta ratios. Findings indicated that ultrasonographic caudal vena cava/aorta ratios are feasible methods for quantifying volume depletion and for use as an adjunct to standard subjective methods for estimating hydration status in dogs.     

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.     

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

O bjective : To describe the computed tomographic and magnetic resonance imaging features of segmental caudal vena cava aplasia and associated vascular anomalies in dogs.
M ethods : A retrospective study was performed reviewing computed tomographic and magnetic resonance imaging archives of eight institutions for dogs with segmental caudal vena cava aplasia. Inclusion criteria included a computed tomographic or magnetic resonance imaging study and supportive diagnostic and follow-up information. Abdominal vessels were reviewed for size, shape, location and course (including tributaries and branches) and classified as normal, abnormal or shunt vessels.
R esults : Ten dogs with segmental caudal vena cava aplasia were identified. In all dogs, postrenal caval blood was shunted to either a right or a left azygos vein, with seven different angiographic patterns. Affected dogs were predominantly female (70 per cent) and young (mean 2·6 years). Additional portocaval and porto-azygos shunt vessels were identified in two cases each. Computed tomographic angiography and magnetic resonance angiography depicted details of abdominal vessels including thrombus formation in one dog.
C linical S ignificance : Segmental caudal vena cava aplasia is a vascular congenital anomaly in the dog that can be associated with thrombosis and portosystemic shunts. Computed tomographic angiography and magnetic resonance angiography are excellent tools to demonstrate the complex vascular anatomy and to guide treatment planning for portosystemic shunts and thrombolytic therapy.     

MULTIDETECTOR ROW COMPUTED TOMOGRAPHY AND ULTRASOUND CHARACTERISTICS OF CAUDAL VENA CAVA DUPLICATION IN DOGS

Caudal vena cava duplication has been rarely reported in small animals. The purpose of this retrospective study was to describe characteristics of duplicated caudal vena cava in a large group of dogs. Computed tomography (CT) and ultrasound databases from two hospitals were searched for canine reports having the diagnosis “double caudal vena cava.” One observer reviewed CT images for 71 dogs and two observers reviewed ultrasound images for 21 dogs. In all CT cases, the duplication comprised two vessels that were bilaterally symmetrical and approximately the same calibre (similar to Type I complete duplication in humans). In all ultrasound cases, the duplicated caudal vena cava appeared as a distinct vessel running on the left side of the abdominal segment of the descending aorta and extending from the left common iliac vein to the left renal vein. The prevalence of caudal vena cava duplication was 0.46% for canine ultrasound studies and 2.08% for canine CT studies performed at these hospitals. Median body weight for affected dogs was significantly lower than that of unaffected dogs (P < 0.0001). Breeds with increased risk for duplicated caudal vena cava were Yorkshire Terrier (odds ratio [OR] = 6.41), Poodle (OR = 7.46), West Highland White Terrier (OR = 6.33), and Maltese (OR = 3.87). Presence of a duplicated caudal vena cava was significantly associated with presence of extrahepatic portosystemic shunt(s) (P < 0.004). While uncommon in dogs, caudal vena cava duplication should be differentiated from other vascular anomalies when planning surgeries and for avoiding misdiagnoses.     

Ultrasonographic identification of vascular invasion by adrenal tumors in dogs

Adrenalectomy is the treatment of choice for adrenal tumors that are producing adverse clinical signs. Surgical planning prior to adrenalectomy is aided by identifying tumors with invasion into adjacent vessels or the presence of a tumor thrombus extending into the caudal vena cava. In this paper, we evaluated the sensitivity and specificity of ultrasound in determining if vascular invasion or tumor thrombus is present. Thirty-four dogs with 36 adrenal tumors were reviewed retrospectively. Overall, 36% of tumors had vascular invasion. Abdominal ultrasound was 100% sensitive and 96% specific in identifying the presence of a tumor thrombus in the caudal vena cava. The sensitivity and specificity was 76% and 96%, respectively, when all forms of vascular invasion were evaluated and included patients with vascular wall invasion without concurrent thrombus. Abdominal ultrasound is a good screening tool for identifying vascular invasion or tumor thrombus associated with adrenal tumors in dogs.     

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.     

Clinical findings and diagnosis of thrombosis of the caudal vena cava in cattle

This paper describes the causes, clinical findings and diagnosis of caudal vena caval thrombosis in cattle. Occlusion of the vein is caused by a 'white' thrombus, and typical clinical signs include chronic weight loss, poor general condition and intermittent fever. Most affected cattle have respiratory signs; in some, pulmonary haemorrhage, ascites and sudden death occur. Haematological analyses, endoscopy of the respiratory tract and ultrasonographic examination of the pleura, liver and abdomen should be carried out in cattle suspected of having thrombosis of the caudal vena cava. The most important diagnostic finding is dilatation of the caudal vena cava seen via ultrasonography. Normally, the caudal vena cava appears triangular in cross section but in cattle with thrombosis it is oval or circular. The prognosis is poor and there is no treatment.     

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.     

Canine leishmaniasis with nephrotic syndrome and aortic and caudal vena cava thromboembolism

Objective – To describe a case of leishmaniasis associated with nephrotic syndrome and aortic and caudal vena cava thrombosis in a dog. Case Summary – A 3‐year‐old male Boxer was referred to the Faculty of Veterinary Medicine, Lisbon, with vomiting, polyuria, polydipsia, lethargy, anorexia, and weight loss. On admission, the dog was thin, quiet, and dehydrated. Initial laboratory abnormalities were compatible with a diagnosis of leishmaniasis (confirmed by serology and bone marrow aspirate), and nephrotic syndrome. Three days later, the animal developed lumbar pain, paraparesis, and absent femoral pulses. Coagulation tests showed a marked reduction in antithrombin (AT) and a mild increase in serum fibrinogen concentration. A diagnosis of thromboembolism was made. In spite of treatment aimed at controlling the primary condition and decreasing further thrombus formation, necrosis developed in the distal right pelvic limb and the nail beds of the left pelvic limb. Against medical advice, medication was stopped and, 15 days later, the dog returned to the hospital, showing extensive necrosis of both pelvic limb extremities. Euthanasia was performed at the owner's request. Necropsy showed a thrombus localized at the distal aorta and extending into the right iliac artery, and an additional thrombus extending from both femoral veins onto the caudal vena cava. New or Unique Information Provided – Thromboembolic disease is rare in dogs with leishmaniasis with nephrotic syndrome. This case suggests that a marked decrease in AT and a mild increase in serum fibrinogen may elicit a hypercoagulable state in these patients.     

Caudal vena cava kinking in dogs with ascites

A 9-year-old dog with spontaneous ascites was found to have hepatic vein distension and a tortuous vena cava on abdominal ultrasound. In right lateral recumbency, the caudal vena cava crossed the diaphragm and became kinked before entering into the right atrium. Following this observation, we performed an experimental study in a normal dog to determine whether kinking of the caudal vena cava could be the result and not the cause of ascites. Ascites was induced using warm saline injected through a needle inserted into the abdominal cavity. Venograms were collected from different body positions, under four conditions: before and after a total of one, two and 3 liters of saline had been injected. Caudal vena cava kinking was observed in the experimental dog after 2 liters of fluid had been injected. Vena cava obstruction may cause ascites, but we found that sometimes caudal vena cava kinking can be the result and not the cause of the peritoneal effusion.     

49-month survival following caval venectomy without nephrectomy in a dog with a pheochromocytoma

An 11 yr old spayed female Labrador retriever was diagnosed with a right adrenal tumor. At surgery, adhesions to the right kidney were dissected, allowing the right kidney to be preserved. The tumor showed extensive invasion into the suprarenal vena cava. It was felt that thrombus removal via venotomy could not be performed. Instead, the vena cava was ligated caudal to the liver and cranial to the right renal vein. The neoplastic gland was then excised en bloc together with the portion of the invaded caudal vena cava. Hind limb edema had developed preoperatively and increased transiently in the first days postoperatively. The animal was discharged 6 days postoperatively with no other clinical disorders, and hind limb edema resolved over time. Histopathology identified a pheochromocytoma. The dog died 49 mo later. A neoplastic thrombus of the vena cava may require venotomy to allow thrombus removal. Occasionally, removal of the thrombus by venotomy may prove impossible. In such a situation, en bloc removal of the concerned portion of the vena cava may be performed with a good long-term outcome provided that gradual occlusion of the vena cava by the thrombus has allowed time for collateral circulation to develop.     

MULTIDETECTOR‐ROW COMPUTED TOMOGRAPHIC CHARACTERISTICS OF PRESUMED PREURETERAL VENA CAVA IN CATS

Preureteral vena cava (circumcaval ureter, retrocaval ureter) occurs in a third of the feline population and has been associated with ureteral strictures in humans. The aim of this retrospective cross‐sectional study was to describe the contrast‐enhanced multidetector row computed tomographic (MDCT) characteristics of presumed preureteral vena cava in a group of cats. Medical records from two institutions located in different continents were searched from 2010–2013 for cases with complete contrast‐enhanced MDCT examinations of the abdomen (i.e. included the entire course of the ureters and prerenal and renal segments of the caudal vena cava) and a diagnosis of preureteral caudal vena cava. For cases meeting inclusion criteria, CT scan data were retrieved and characteristics of the preureteral caudal vena cava were recorded. Presence of concomitant renal or ureteral diseases was also recorded. A total of 272 cats had contrast‐enhanced abdominal CT scans during the study period and of these, 68 cats (22.43 ± 4.96%) had a diagnosis of presumed preureteral vena cava. In all affected cats, a “reverse‐J ureter” was observed, i.e. a ureter running medially at the level of L4–5, passing dorsally to the caudal vena cava and then exiting ventrally between the caudal vena cava and aorta returning to its normal position. Having a preureteral vena cava resulted in an increased risk for concurrent urinary signs (OR = 3.00; CI: 95%; 1.28–6.99; P = 0.01). Findings supported the use of contrast‐enhanced MDCT for characterizing morphology of preureteral vena cava and its relation with ureters in cats.     

A new technique for surgery of the caudal vena cava in dogs using partial venous inflow occlusion

The haemodynamic and metabolic effects of caudal vena cava occlusion were evaluated in six normal anaesthetised dogs. Each animal underwent a single eight minute episode of caudal vena cava occlusion. The procedure was well tolerated by all the dogs. Systolic arterial pressure was reduced by 62 +/- 5 per cent and the heart rate increased by 11 +/- 3 per cent. There was rapid haemodynamic recovery after the release of occlusion, all cardiovascular parameters returning to normal spontaneously within five minutes. Caudal vena cava occlusion is therefore safe for periods of up to eight minutes in normal dogs. This technique allows repair of caudal vena caval lesions without necessitating systemic heparinisation and the use of cavoatrial conduits.     

Surgical correction of cor triatriatum dexter in a dog under extracorporeal circulation

A shiba inu dog with marked abdominal distension was diagnosed with cor triatriatum dexter and surgical correction was performed under extracorporeal circulation. The total duration of cardiac arrest was 11 minutes and total perfusion time was 34 minutes. The dog had an uneventful postoperative recovery. Postoperative contrast radiography of the caudal vena cava revealed normal flow into the right heart. Abdominal distension was no longer observed. Although several methods have been used to treat cor triatriatum dexter in dogs, the authors consider surgical correction under extracorporeal circulation to be a reliable approach.     

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.     

Evaluation of gradual occlusion of the caudal vena cava in clinically normal dogs

OBJECTIVES: To devise a technique for gradual occlusion of the caudal vena cava in dogs and determine effects of complete occlusion of the caudal vena cava. ANIMALS: 8 mixed-breed hounds that weighed between 25 and 30 kg. PROCEDURE: Baseline evaluation of dogs included serum biochemical analyses and determination of glomerular filtration rate (GFR) with dynamic renal scintigraphy and plasma clearance analysis. An occluder was placed around the vena cava in the region cranial to the renal veins. The occluder was attached to a vascular access port. The vena cava was gradually occluded over 2 weeks. The GFR was measured every 2 weeks after surgery, and venograms were performed every 3 weeks after surgery. Blood samples were collected every 48 hours for the first week and then weekly thereafter to measure BUN and creatinine concentrations and activities of alanine transaminase, alkaline phosphatase, and creatinine kinase. Dogs were euthanatized 6 weeks after surgery, and tissues were submitted for histologic examination. The GFR and biochemical data were compared with baseline values. RESULTS: Gradual occlusion of the caudal vena cava was easily and consistently performed with this method, and adverse clinical signs were not detected. Formation of collateral vessels allowed overall GFR to remain constant despite a decrease in function of the left kidney. Measured biochemical values did not deviate from reference ranges. CONCLUSIONS AND CLINICAL RELEVANCE: Gradual occlusion of the caudal vena cava may allow removal of adrenal gland tumors with vascular invasion that would otherwise be difficult or impossible to resect.     

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.