Arteriovenous Malformation of the Tongue Resulting in Recurrent Severe Hemorrhage in a Young Dog.

An 8 mo old male entire beagle was presented to the emergency and critical care service following several severe bleeding episodes from the oral cavity. Oral examination revealed a purple, spongy, pulsatile lesion on the rostral two-thirds of the tongue. Computed tomography angiography revealed a severely distended right linguofacial vein with numerous, tortuous branching vessels within the tongue, consistent with an arteriovenous (AV) malformation. A cervical surgical approach was performed, and the right lingual artery was isolated and catheterized. A direct arteriogram confirmed this was the main feeder artery to the lesion, and it was ligated. Although the bleeding episodes initially resolved, a moderate bleeding episode occurred 6 days postoperatively, and a partial glossectomy was performed. Histopathology was consistent with an AV malformation. The dog had a good recovery from surgery and remains free of clinical signs 13 mo later. Following extensive review of the veterinary literature, this is the only reported case of a lingual AV malformation in the dog. Partial glossectomy resulted in resolution of the clinical signs and was well tolerated. Although rare, AV malformations should be considered as a differential diagnosis for spontaneous oropharyngeal bleeding.

Canine and feline abdominal arterioportal communications can be classified based on branching patterns in computed tomographic angiography.

Arterioportal vascular anomalies are communications between the splanchnic arteries and the portal system that represent a rare cause of presinusoidal portal hypertension in small animals. There is little information concerning the imaging findings of arterioportal communications in small animals and no classification could be found for radiologists and surgeons. The aims of this retrospective descriptive multicentric study were to describe the computed tomographic characteristics of arterioportal communications in a group of cats and dogs, and to propose a classification based on computed tomography (CT) angiographic anatomy. Computed tomography databases from multiple veterinary hospitals were searched for cats and dogs with a diagnosis of arterioportal communication. A total of 36 animals (33 dogs, three cats) met the inclusion criteria. There were 32 intrahepatic arterioportal malformations and four extrahepatic fistulae. The intrahepatic arterioportal malformations were classified as right divisional (11/32) and left divisional (21/32), and the left divisional were subclassified as left medial (16/21) and left lateral (4/21). One patient showed multiple intrahepatic arterioportal communications with concomitant left medial and left lateral conformations. Two patients with intrahepatic arteriovenous malformation showed concomitant congenital intrahepatic shunts. The proposed anatomical classification based on CT angiography could allow veterinary radiologists to have a more systematic approach and help improve the radiologist-surgeon communication.

Micro-arteriovenous malformation causing spontaneous metacarpal pad hemorrhage in a dog.

A 5-year-old neutered male Labrador retriever dog with a 3-year history of intermittent hemorrhage from the right metacarpal pad was evaluated. A small region of hyperattenuation of the metacarpal pad was evident on computed tomographic angiography. Excisional biopsy of the location of the purported hemorrhage revealed a micro-arteriovenous malformation on histologic examination.

Malformation micro-artérioveneineuse causant une hémorragie spontanée du coussinet métacarpien chez un chien. Un chien Labrador retriever mâle âgé de 5 ans avec une anamnèse de 3 ans d'hémorragie intermittente du coussinet métacarpien droit a été évalué. Une petite région d'hyper-atténuation du coussinet métacarpien était évidente à l'angiographie TDM. L'excision-biopsie de l'emplacement présumé de l'hémorragie a révélé une malformation micro-artérioveineuse à l'examen histologique.(Traduit par Isabelle Vallières).

IMAGING DIAGNOSIS--RADIOGRAPHIC, ULTRASONOGRAPHIC, COMPUTED TOMOGRAPHIC, AND FLUOROSCOPIC APPEARANCE OF A DISTAL PELVIC LIMB ARTERIOVENOUS MALFORMATION IN A YOUNG GERMAN SHEPHERD DOG.

A German shepherd puppy presented for evaluation of a suspected arteriovenous fistula on the distal aspect of the right pelvic limb. Radiographs demonstrated expansion and resorption of the tarsal and metatarsal bones, and ultrasound detected a vascular abnormality. Using computed tomographic angiography, a complex arteriovenous malformation (AVM) involving the distal tibia, tarsus, and the metatarsus and an osteochondritis dissecans (OCD) lesion of the talus were identified. Based on these findings, therapeutic limb amputation was performed. Fluoroscopic angiography, vascular casting, and dissection were then used to further characterize features of this previously unreported AVM with concurrent bony lesions and OCD.

Hepatic arteriovenous malformation in a calf.

A case of hepatic arteriovenous malformation is described in a calf that presented with a marked increase in abdominal volume and died 12 h after birth. At necropsy, the calf had marked abdominal distension and haemoperitoneum. The left hepatic lobe was reduced in size and covered by slightly whitish and intensely vascularized membranous tissue. At the edge of the left lobe there were cystic structures filled with translucent fluid. On cut surface, there were multiple cavitations well delimited by whitish walls and multiple dilated blood vessels that communicated with the cavitations. Histopathology revealed an increase in the number of vascular structures of variable calibre within loose fibrous connective tissue. The diagnosis of hepatic arteriovenous malformation was based on the lesions and confirmed by immunohistochemistry. Hepatic arteriovenous malformations are rare in all species, have not been described in cattle and should be included as a cause of mortality in neonates with post-partum haemoperitoneum.

Jejunal arteriovenous malformation and multiple acquired extrahepatic portosystemic shunts in a juvenile dog, presenting with melena.

A juvenile dog referred with a 1-month history of persistent melena and severe anaemia, was diagnosed with a jejunal arteriovenous malformation, and multiple acquired extrahepatic portosystemic shunts. A midline coeliotomy was performed, the jejunal arteriovenous malformation was localised intraoperatively and was successfully removed via an enterectomy. Histopathology confirmed a true arteriovenous malformation. Despite the initial improvement, the patient developed seizure episodes secondary to hepatic encephalopathy 8 months after surgery. Fifteen months after surgery, the owner opted for euthanasia due to the ongoing seizure episodes. Post-mortem histologic examination of the liver showed features consistent with portal vein hypoplasia. A congenital arteriovenous malformation should be considered as a differential diagnosis in juvenile patients with a chronic history of haemorrhage from the gastrointestinal tract. In addition, acquired portosystemic shunts may occur in patients with portal vein hypoplasia and jejunal arteriovenous malformations.

Pulmonary arteriovenous malformation and a concurrent patent ductus arteriosus in a Doberman.

A 7-week-old male Doberman presented with tachypnea, dyspnea and a VI/VI, left cranial, continuous heart murmur. Thoracic radiographs revealed severe left-sided cardiomegaly, presence of a rounded soft tissue opacity in the caudodorsal aspect of the thoracic cavity and signs of left-sided congestive heart failure. Clinical signs of heart failure were medically controlled. Echocardiography and computed tomography demonstrated a left-to-right shunting patent ductus arteriosus (PDA) in combination with a right-to-left shunting pulmonary arteriovenous malformation (PAVM) between the right main pulmonary artery and the right caudal pulmonary vein. Arterial blood gasses revealed mild hypoxemia. Transcatheter occlusion of the PDA using an Amplatz Canine Duct Occluder was performed. Four months post-operatively, echocardiography showed normal cardiac size and function with complete PDA closure. Thoracic radiographs revealed absence of the rounded opacity and resolution of cardiomegaly and vascular congestion. The PAVM was no longer visualized on repeated computed tomography and the arterial blood gasses were within normal limits. A PAVM connecting a pulmonary artery to a pulmonary vein has only rarely been reported in dogs. This report describes the presence of a congenital PAVM in combination with a PDA in a dog, which has not been previously reported in veterinary medicine.

Dominant outflow vein occlusion in the management of naturally occurring peripheral arteriovenous anomalies in cats and dogs.

Two dogs and 1 cat were referred to a tertiary veterinary center for the consultation and treatment of limb edema, variable dermal sanguineous crusting lesions, and intermittent lameness. A peripheral arteriovenous anomaly (PAA) was diagnosed via computed tomographic angiography (CTA) in each case. Arteriography enabled further evaluation of the PAA with confirmation of a dominant outflow vein. Dominant outflow vein occlusion was achieved by direct ligation in 1 dog and retrograde transvenous glue embolization in the cat and other dog. Repeat arteriography demonstrated resolution of arteriovenous shunting. Presenting clinical signs resolved in all animals. The previously identified aberrant vessels in 1 dog were not identified after CTA 40 days postoperatively. No postoperative complications or recurrence was identified in any case during the 6- to 55-month follow-up period.

Myelopathy secondary to an intramedullary arteriovenous malformation in a mature dog.

A 2-year-old crossbreed dog was presented for evaluation of a 6-week history of progressive paraparesis. Magnetic resonance imaging and computed tomography angiography of the thoracic and lumbar spinal cord disclosed multifocal, anomalous, small, vascular structures, distributed throughout the subarachnoid space of the included section of the spinal cord. An additional focal intramedullary lesion was identified extending from T9 to T10 to T12. Histopathological examination confirmed the presence of an intramedullary arteriovenous malformation affecting the thoracic spinal cord and leading to diffuse congestion and focal hemorrhages into the affected spinal cord.

Use of percutaneous foam sclerotherapy with 1.5% sodium tetradecyl sulfate for treatment of a pelvic limb venous malformation in a dog.

CASE DESCRIPTION: A 6-year-old 17-kg (37.4-lb) spayed female mixed-breed dog was evaluated because of swelling and intermittent lameness of the right pelvic limb and perianal and vulvar bleeding caused by a suspected arteriovenous malformation. CLINICAL FINDINGS: The right pelvic limb had a diffuse, raised, cobblestone-like appearance with lameness, edema, and multifocal ulcerations. The abdominal skin had multifocal circular erythematous lesions, the perianal region was erythematous, and the vestibule had superficial distended vessels. Ultrasonography and CT did not reveal the presence of an arteriovenous malformation; however, digital subtraction venography confirmed the presence of a venous malformation (VM) throughout the limb. TREATMENT AND OUTCOME: A mixture of foam sclerosant (1.5% sodium tetradecyl sulfate) and contrast medium was agitated with air and injected percutaneously into the VM. The dog received an injection of corticosteroid solution, and a soft-padded bandage was applied to the limb for 3 days. Six weeks later, the dog would intermittently hop when running, and the limb was mildly edematous with ecchymotic lesions; the swelling and lameness had improved considerably. Perianal and vulvar bleeding and dilation of the vestibular vessels had resolved. At 21 months after the procedure, examination revealed no right pelvic limb lameness related to the VM; only small cyst-like lesions and edema around the tarsus remained. CLINICAL RELEVANCE: The favorable clinical outcome for this dog for a 21-month period after treatment of a pelvic limb VM with foam sclerotherapy has suggested that foam sclerotherapy may be used to successfully treat limb VMs in some dogs.

Coronary arteriovenous malformation in a dog with a complex arrhythmia and hypothyroidism.

A four-year-old Japanese Akita was referred for investigation of lethargy, exercise intolerance, and an irregular heart rhythm. He was diagnosed with atrial fibrillation, a complex ventricular arrhythmia, and hypothyroidism. Echocardiography identified a nest of anomalous vessels surrounding the heart and shunting into the pulmonary artery. Computed tomography confirmed a coronary arteriovenous malformation consisting of a coronary-to-pulmonary arterial communication and an associated complex nest of tortuous vessels, which was thought to be an incidental finding. Clinical signs improved with levothyroxine and antiarrhythmic treatment. Describing an unusual coronary artery anomaly as well, this case serves as a reminder to critically evaluate the hemodynamic significance of structural cardiac disease and to screen for systemic disease in patients with arrhythmias.

Endovascular treatment of a high-flow hepatic arteriovenous malformation with secondary portal hypertension in a dog.

CASE DESCRIPTION A 17-month-old neutered female Labrador Retriever with a 3- to 4-month history of abdominal distention was referred for evaluation and treatment. CLINICAL FINDINGS Evaluation of a peritoneal fluid specimen collected by the referring veterinarian indicated a pure transudate. At admission, transabdominal ultrasonography revealed microhepatica, dilation of the intrahepatic and mesenteric vasculature, peritoneal effusion, and multiple aberrant blood vessels. A large, high-flow hepatic arteriovenous malformation (HAVM) with secondary portal hypertension, peritoneal effusion, multiple acquired portosystemic shunts, and microhepatica was evident on CT angiography. TREATMENT AND OUTCOME Transfemoral hepatic arteriography and staged coil and glue (n-butyl cyanoacrylate) embolization of the complex arteriovenous malformation nidus and central main left hepatic artery resulted in ablation of the lesion, restoration of arterial blood flow to the contralateral hepatic lobes, and resolution of the peritoneal effusion. The dog remained without clinical signs of hepatic disease until it was euthanized 5 months after treatment for an unrelated condition. CLINICAL RELEVANCE Successful endovascular management of a HAVM was accomplished by means of coil and glue embolization in the patient of this report. Dogs with comparable HAVMs may benefit from similar minimally invasive treatment.

Use of n-butyl cyanoacrylate to reduce left to right shunting of an abdominal arteriovenous malformation in a dog.

A 9-month old castrated male Labradoodle presented to the cardiology service at Purdue University for evaluation of a low-grade murmur. Physical examination, thoracic radiography, and echocardiography were strongly supportive of an extracardiac left-to-right shunt. Subsequent evaluation with nuclear scintigraphy and computed tomography angiography revealed a large, complex arteriovenous malformation within the cranial abdomen. Staged interventional attenuation of the shunt was performed using n-butyl cyanoacrylate that resulted in a reduction in echocardiographic and nuclear scintigraphy derived shunt estimation.

Minimally invasive treatment of mesenteric arterioportal fistulas in two dogs.

CASE DESCRIPTION Two Pembroke Welsh Corgis with gastrointestinal signs including inappetence, diarrhea, lethargy, and hypersalivation were referred for evaluation. CLINICAL FINDINGS Diagnostic testing included abdominal ultrasonography and CT angiography. One patient had a cranial mesenteric artery-to-mesenteric vein fistula with multiple acquired extrahepatic portosystemic shunts. The second patient had both cranial and caudal mesenteric artery-to-mesenteric vein fistulas and multiple acquired extrahepatic portosystemic shunts. TREATMENT AND OUTCOME Both patients underwent minimally invasive coil embolization of the mesenteric arterioportal fistulas, with complete occlusion confirmed by means of angiography at procedure completion. Clinical outcome approximately 1 year after treatment was assessed as fair to good because of recurrence of clinical signs that required medical management in 1 dog and some persistent serum biochemical abnormalities. CLINICAL RELEVANCE Outcome for the 2 patients described suggested that coil embolization may be a feasible and effective minimally invasive technique for the treatment of mesenteric arterioportal fistulas in dogs. However, further investigation of the potential for chronic hepatic disease in patients with a history of acquired portosystemic shunts is warranted.

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.

Diagnostic value of the rectal ammonia tolerance test, fasting plasma ammonia and fasting plasma bile acids for canine portosystemic shunting.

Portosystemic shunting (PSS) often results in hyperammonaemia and, consequently, hepatic encephalopathy. This retrospective study evaluated the sensitivity, specificity, positive and negative predictive values (PPV and NPV, respectively) and other test performance metrics for the ammonia tolerance test (ATT), serum fasting bile acids (FBA), serum fasting ammonia concentration (FA), and combinations of these tests for their association with PSS in dogs. Medical records of 271 dogs suspect for PSS (symptomatic group) and 53 dogs returning for evaluation after surgical closure of a congenital PSS (CPSS post-surgical control group) were analysed. In the symptomatic group, ATT at 40 min (T40), and the FBA had the highest sensitivity (100% and 98%, respectively) and NPV (100% and 96%, respectively) for PSS. The combination of increased FBA and FA had the highest specificity (97%), with a PPV of 97%, and a positive likelihood ratio of 29. In the CPSS post-surgical control group, the specificity and PPV of FA and the combination of increased FBA/FA were both 100%. In purebred populations, the NPV of all tests was 100%. Consequently, PSS would be ruled out in a symptomatic dog with normal FBA or ATT (T40) and would be highly probable when both FBA and FA are increased. Increased FA was conclusive for PSS in dogs evaluated for post-surgical closure of a CPSS. FBA was the most suitable test for screening purposes.

Arteriovenous malformation of the cervical spinal cord in a dog.

An 8-year-old female German Shepherd dog showed first order Horner's syndrome associated with progressive right-sided hemiplegia and mega-oesophagus. Intramedullary and leptomeningeal arteriovenous malformation (AVM) was identified in the cervical spinal cord. The morphological characteristics were arteriovenous shunting, intramedullary multiple thromboses and haemorrhage, non-inflammatory necrosis of white and grey matter around the shunt, and intervening neural gliosis with neovascularization. These findings suggested that the malformation induced a focal circulatory disturbance within the cervical spinal cord and that fatal thrombosis was responsible for the sudden onset of the nervous signs and progressive neurological deterioration. This is the first report of intramedullary spinal AVM in a dog.

Vascular malformations and angiomatous lesions in horses: a review of 10 cases.

Vascular malformations and angiomas are rather uncommon in horses and the literature concerning these lesions is reviewed. The pathology is described in 10 additional cases. These lesions were classified as arteriovenous malformation (one case), haemangiomas (six cases), 'proliferative angiomas' (two cases) and lymphangioma (one case). The haemangiomas and lymphangioma were probably hamartomatous in origin. Both cases of 'proliferative angioma' developed in aged animals and their pathogenesis was uncertain. More information is needed on the natural history and behaviour of lesions of this type.

Postprandial venous ammonia concentrations in the diagnosis of hepatobiliary disease in dogs.

A postprandial ammonia tolerance test (PPATT) was performed on normal dogs and dogs with signs that suggested they may have liver disease. All dogs underwent transcolonic scintigraphy, liver biopsy, or both and were assigned to extrahepatic disease, primary hepatocellular, and congenital portosystemic vascular anomalies (PSVA) groups. Each dog was fed a chicken and rice diet providing 25% of its estimated daily metabolizable energy requirement (MER) as an ammonia challenge. This is practical in patients with liver disease because ammonium chloride administration often causes vomiting or ammonia toxicity. Venous ammonia concentrations were measured before feeding and every 2 hours after feeding for 8 hours. No difference in mean ammonia concentrations between dogs with extrahepatic disease and control dogs was found. Therefore, the specificity of the PPATT was 100%. Dogs with hepatocellular disease showed no change in mean ammonia concentration at any time point, before or after feeding, but sensitivity was greatest when venous ammonia was measured 6 hours after feeding (sensitivity before feeding, 28%, and after feeding, 36%). Among dogs with congenital PSVA, mean ammonia concentrations were higher than the reference range at all time points before and after feeding, and peak mean ammonia concentration occurred 6 hours after feeding. In this group, the sensitivity of the PPATT was 81% before feeding and 91% 6 hours after feeding. This study demonstrates that the measurement of venous ammonia concentration is a useful test to detect congenital PSVA, and the sensitivity of the test may be improved by sampling 6 hours after feeding. The PPATT has poor sensitivity in detecting primary hepatocellular disease.

Evaluation of serum bile acid concentrations for the diagnosis of portosystemic venous anomalies in the dog and cat.

The serum concentration of bile acids was measured in dogs and cats with portosystemic venous anomalies (PSVA). In 14 dogs, the mean serum bile acid concentration after 12 hours of fasting was 61.7 +/- 68.7 mumol/L (normal, 2.3 +/- 0.4 mumol/L (SEM) and when measured 2 hours after a meal in 15 dogs was 229.9 +/- 87.7 mumol/L (normal, 8.3 +/- 2.2 mumol/L). The fasting serum bile acid concentration was within the normal range in 5 of 14 dogs. The postprandial concentration was determined in 3 of the 5 and in each case increased more than tenfold above the fasting value. The mean fasting serum bile acid concentration in 4 cats was 24.4 +/- 10.1 mumol/L (normal, 1.7 +/- 0.3 mumol/L) and in 2 of the cats increased to a mean of 120.6 mumol/L (normal, 8.3 +/- 0.8 mumol/L) 2 hours after feeding. The bile acid values in patients with PSVA were correlated with values for blood ammonia content, sulfobromophthalein (BSP) retention, and results of conventional tests of hepatic function. Bile acid concentrations were more sensitive than abnormalities in serum enzyme activities or BSP retention and equal in sensitivity to the ammonia tolerance test in detecting hepatobiliary insufficiency. Bile acid measurements were accomplished with less inconvenience to the patient and clinician, than tests of BSP excretion or ammonia tolerance. Used in combination with conventional laboratory tests for hepatic disease, pre- and postprandial serum bile acid concentrations appear to be a sensitive and specific indicator of hepatobiliary dysfunction of value in the diagnosis of PSVA in the dog and cat.