TRIPLE‐PHASE HELICAL COMPUTED TOMOGRAPHY IN DOGS WITH HEPATIC MASSES

The purpose of this study was to determine the utility of triple‐phase helical computed tomography (CT) for differentiating canine hepatic masses. Seventy dogs with hepatic masses underwent triple‐phase CT followed by surgical removal of the hepatic masses. Triple‐phase helical CT scans for each dog included precontrast, arterial phase, portal venous phase, and delayed phase studies. The removed hepatic masses were histopathologically classified as hepatocellular carcinoma (n = 47), nodular hyperplasia (n = 14), and hepatic metastatic tumors (n = 9) in dogs. Of the 47 hepatocellular carcinomas, the most common CT findings included a heterogeneous pattern with hyper‐, iso‐, and hypoenhancement in both the arterial and portal venous phases (40/47, 85.1%). Of the 14 nodular hyperplasias, the most common CT findings were a homogeneous pattern with hyper‐ and isoenhancement in both the portal venous and delayed phases (13/14, 92.9%). Of nine hepatic metastatic tumors, the most common CT findings included a homogeneous hypoenhancement pattern in both the arterial and portal venous phases (8/9, 88.9%). In addition, 5 (55.6%) showed homogeneous hypoenhancement patterns in the delayed phase. Findings from our study indicated that triple‐phase CT is a useful tool for preoperative differentiation of hepatocellular carcinoma, nodular hyperplasia, and hepatic metastatic tumors in dogs.     

Contrast‐enhanced ultrasonography is a feasible technique for quantifying hepatic microvascular perfusion in dogs with extrahepatic congenital portosystemic shunts

Extrahepatic‐congenital portosystemic shunt is a vascular anomaly that connects the portal vein to the systemic circulation and leads to a change in hepatic microvascular perfusion. However, an assessment of hepatic microvascular perfusion is limited by conventional diagnostic modalities. The aim of this prospective, exploratory study was to assess hepatic microvascular perfusion in dogs with extrahepatic‐congenital portosystemic shunt using contrast‐enhanced ultrasonography (CEUS) using perfluorobutane (Sonazoid^®). A total of 17 dogs were included, eight healthy dogs and nine with extrahepatic‐congenital portosystemic shunt. The time‐to‐peak (TTP), rising time (RT), and rising rate (RR) in the hepatic artery, portal vein, and hepatic parenchyma, as well as the portal vein‐to‐hepatic parenchyma transit time (ΔHP‐PV) measured from time‐intensity curve on CEUS were compared between healthy and extrahepatic‐congenital portosystemic shunt dogs. The RT of the hepatic artery in extrahepatic‐congenital portosystemic shunt dogs was significantly earlier than in healthy dogs (P = 0.0153). The TTP and RT of the hepatic parenchyma were significantly earlier in extrahepatic‐congenital portosystemic shunt dogs than in healthy dogs (P = 0.0018 and P = 0.0024, respectively). ΔHP–PV was significantly shorter in extrahepatic‐congenital portosystemic shunt dogs than in healthy dogs (P = 0.0018). CEUS effectively revealed changes in hepatic microvascular perfusion including hepatic artery, portal vein, and hepatic parenchyma simultaneously in extrahepatic‐congenital portosystemic shunt dogs. Rapid hepatic artery and hepatic parenchyma enhancements may reflect a compensatory increase in hepatic artery blood flow (arterialization) caused by a decrease in portal vein blood flow and may be used as an additional diagnostic test to distinguish extrahepatic‐congenital portosystemic shunt dogs from healthy dogs.     

Statistical relevance of ultrasonographic criteria in the assessment of diffuse liver disease in dogs and cats

OBJECTIVE: To determine whether objectively applied ultrasonographic interpretive criteria are statistically useful in differentiating among 7 defined categories of diffuse liver disease in dogs and cats. SAMPLE POPULATION: Ultrasonographic images of 229 dogs and 104 cats. PROCEDURES: Liver parenchymal or related sonographic criteria established by the authors were retrospectively and independently applied by 3 radiologists who were not aware of patient status or patient laboratory data. Seven histologic or cytologic categories of diffuse (infiltrative but not nodular) liver diseases were jointly established by the authors and included normal liver; inflammation; round-cell neoplasia; non-round-cell infiltrative, prenodular (early) metastatic neoplasia; lipidosis; vacuolar hepatopathy; and other. Liver parenchymal sonographic criteria included parenchymal sound attenuation with increasing depth, comparative organ echogenicity (liver, spleen, and kidneys), diffuse or patchy hyperechoic or hypoechoic echotexture, uniform or coarse echotexture, portal venous clarity, and liver lobe geometry. Related extrahepatic criteria included gallbladder wall thickness, bile duct diameter, amount and character of gallbladder precipitate, nondependent shadowing in the gallbladder, hepatic vein diameter versus caudal vena cava diameter, peritoneal fluid, spleen echotexture (normal vs abnormal [characterized]), and kidney echotexture. Ultrasonographic criteria were statistically compared to the 7 categories of diffuse liver disease in search of clinically exploitable relationships. RESULTS: Statistical evaluation of the applied ultrasonographic criteria did not yield clinically acceptable accuracy for discrimination among the 7 categories of diffuse liver diseases (including normal liver) in either species. CONCLUSIONS AND CLINICAL RELEVANCE: Criterion-based ultrasonographic appearance was insufficient to discriminate among canine and feline diffuse infiltrative liver diseases.     

MICRONODULAR ULTRASOUND LESIONS IN THE COLONIC SUBMUCOSA OF 42 DOGS AND 14 CATS

Micronodular ultrasound lesions have been detected in the colonic submucosa of dogs and cats at our hospital. The lesions had rounded/oval shapes, measured 1–3 mm in size, and exhibited a hypo/anechoic ultrasonographic pattern. To our knowledge, these lesions have not been previously reported in human or veterinary patients. The purpose of this retrospective study was to determine whether micronodular lesions were associated with other abdominal ultrasound abnormalities or clinical findings. Medical records of dogs and cats with sonographic reports describing micronodular lesions within the colonic submucosa were reviewed. Concurrent ultrasonographic abnormalities were recorded and compared with clinical sidgns and follow‐up data. A total of 42 dogs and 14 cats met inclusion criteria. Concurrent sonographic abnormalities included the following: increased colon wall thickness (12.5%); small bowel wall thickening, altered layering, and/or hyperechoic mucosa (45%); abdominal effusion (29%); caudal mesenteric lymphadenopathy (46%); mesenteric lymphadenopathy (27%); and pericolic peritoneal fat reactivity (9%). Fifty of 56 animals presented with diarrhea. Twenty‐seven cases had clinical signs of colitis and ultrasonographic lesions were limited to the colonic submucosa. In nine cases, follow‐up examination at 6–8 weeks showed resolution of clinical and ultrasonographic signs. Ultrasonographic and clinical examinations in 17 patients at 12–18 months and in 20 patients at 18–30 months from initial diagnosis showed resolution of submucosal lesions and clinical signs of enteropathy. The authors propose that micronodular submucosal ultrasound lesions may represent reactive intraparietal lymphoid follicles and may be indicators of colonic inflammatory diseases in dogs and cats.     

Canine and feline emphysematous gastritis may be differentiated from gastric emphysema based on clinical and imaging characteristics: Five cases

Gastric pneumatosis is an imaging finding defined as the presence of gas foci in the gastric wall. In humans, this imaging feature can result from one of two separate clinical entities: life‐threatening emphysematous gastritis or clinically benign gastric emphysema. This retrospective case series study describes the clinical and imaging features in five animals diagnosed with spontaneous gastric pneumatosis without gastric dilatation‐volvulus. Three canine and two feline cases of spontaneous gastric pneumatosis were identified on radiographic and ultrasonographic examinations. In addition to gastric pneumatosis, one dog and two cats presented concomitant systemic signs such as lethargy, hematemesis, anemia, or leukocytosis. Two dogs remained asymptomatic or presented mild gastrointestinal signs. Portal gas was described in two dogs and one cat, and pneumoperitoneum in one dog. These features were not considered clinically significant. The dog and two cats with systemic signs were euthanized due to clinical deterioration and diagnosed with emphysematous gastritis. The gastric pneumatosis of both dogs without systemic signs resolved while on medical management without antibiotic therapy. These latter cases were interpreted as consistent with gastric emphysema. Findings from the current study indicated that gastric pneumatosis can occur without gastric dilatation‐volvulus in cats and dogs and that a combination of clinical and imaging characteristics may help to differentiate between potentially life‐threatening emphysematous gastritis and relatively benign gastric emphysema. More studies are needed to determine the etiology and risk factors associated with these conditions.     

QUANTITATIVE HEPATOBILIARY SCINTIGRAPHY USING 99mTC-DISIDA IN THE DOG

Quantitative hepatobiliary scintigraphy using ^99mTc-2,6 diisopropylphenylcarbamoylmethyl iminodiacetic acid (DISIDA) was performed in normal dogs. ^99mTc-DISIDA is excreted by the hepatocyte into the biliary tract. Hepatic blood flow from arterial and portal venous sources was measured as the hepatic perfusion index. The hepatic clearance of the radiopharmaceutical was used to assess hepatocyte function and parenchymal biliary transport. Biliary ejection was evaluated using synthetic cholecystokinin infusion. The procedure should be useful in evaluating dogs with hepatic and biliary disease.     

Retrospective evaluation of the prognostic utility of plasma lactate concentration,base deficit,pH, and anion gap in canine and feline emergency patients

Objective

To determine the association of plasma lactate concentration, pH, base deficit (BD), and anion gap (AG) in dogs and cats on presentation to an emergency room with outcome, and to compare the prognostic significance of hyperlactatemia with a concurrent metabolic acidosis with that of hyperlactatemia and a normal metabolic acid–base balance.

Design

Retrospective study.

Setting

University teaching hospital.

Animals

Five hundred sixty‐six dogs and 185 cats that had venous blood gas analysis performed.

Interventions

None.

Measurements and Main Results

Medical records were reviewed for plasma lactate concentrations, electrolyte concentrations, and acid–base parameters obtained on emergency room admission, clinical diagnosis, and in‐hospital mortality. The primary outcome measure was all‐cause mortality for the hospitalized visit. Median plasma lactate concentration and AG were higher, BD was more negative, and pH was lower, in non‐survivor dogs and cats. The prevalence of hyperlactatemia was 53% in dogs and 30% in cats. Lactic acidosis was present in 42% and 80% of hyperlactatemic dogs and cats, respectively. Multivariate regression analyses revealed that plasma lactate concentration, BD, and pH, but not AG, were independent predictors of mortality in dogs, and that only plasma lactate concentration was an independent predictor of mortality in cats. Mortality was highest for animals with lactic acidosis, at 59.8% in dogs and 49% in cats. Mortality in dogs with lactic acidosis was significantly higher than dogs with hyperlactatemia and a normal acid–base status (P < 0.0001).

Conclusions

The presence and magnitude of hyperlactatemia on presentation to the emergency room may help identify dogs and cats with high likelihood of in‐hospital mortality, and the presence of lactic acidosis specifically may help identify dogs with yet higher risk of in‐hospital mortality.     

Nodules and masses are associated with malignant pleural effusion in dogs and cats but many other intrathoracic CT features are poor predictors of the effusion type

Thoracic CT may be used in the workup of patients with pleural effusion. In humans, certain pleural features on CT aid in diagnosing an underlying cause for pleural effusion, whereas this is not well studied in veterinary medicine. This retrospective cross‐sectional analytical study assessed pleural and other intrathoracic abnormalities on CT in dogs and cats with pleural effusion and explored potential discriminatory features between effusion types. Eighty‐nine dogs and 32 cats with pleural cytology and/or histopathology were categorized into malignant pleural disease (15 dogs and 11 cats), pyothorax (34 dogs and 7 cats), chylothorax (20 dogs and 11 cats), transudative (11 dogs and 2 cats), and hemorrhagic effusion (9 dogs and 1 cat). Multivariable logistic regression analysis comparing malignancy to other effusions found that older patient age (dogs: odds ratio 1.28, P = 0.015; cats: odds ratio 1.53, P = 0.005), nodular diaphragmatic pleural thickening (dogs: odds ratio 7.64, P = 0.021; cats: odds ratio 13.67, P = 0.031), costal pleural masses (dogs: odds ratio 21.50, P = 0.018; cats: odds ratio 32.74, P = 0.019), and pulmonary masses (dogs: odds ratio 44.67, P = 0.002; cats: odds ratio 18.26, P = 0.077) were associated with malignancy. In dogs, any costal pleural abnormality (odds ratio 47.55, P = 0.002) and pulmonary masses (odds ratio 10.05, P = 0.004) were associated with malignancy/pyothorax, whereas any costal pleural abnormality (odds ratio 0.14, P = 0.006) and sternal lymphadenopathy (odds ratio 0.22, P = 0.040) were inversely associated with transudates. There were, however, many overlapping abnormalities between effusion types, so further diagnostic testing remains important for diagnosis.     

Choledochotomy and primary repair of extrahepatic biliary duct rupture in seven dogs and two cats

Objective : To report clinical findings and outcome in dogs and cats undergoing choledochotomy or primary repair of extrahepatic biliary duct rupture. Methods : Retrospective study of dogs (n=7) and cats (n=2) that had choledochotomy or primary bile duct repair. Results : Extrahepatic biliary obstruction was confirmed at surgery in all cases. The underlying cause in four dogs and both cats was choledocholithiasis, two dogs had gall bladder mucocoeles with associated bile duct rupture, and one dog had inspissated bile obstructing the bile duct secondary to gall bladder carcinoid tumour. Three dogs and both cats had choledochotomies performed to relieve extrahepatic biliary obstruction, and four dogs with bile duct rupture underwent primary repair of the defect. One dog with a bile duct rupture was re‐explored four days postoperatively and had suffered dehiscence of the repair; this rupture was re‐repaired. All animals were discharged from the hospital, and did not have clinical recurrence of extrahepatic biliary obstruction. Clinical Significance : Choledochotomy and primary repair of extrahepatic biliary duct rupture were associated with low perioperative morbidity and no mortality in this small cohort of cases. These techniques are reasonable options either alone or in conjunction with other procedures when bile duct patency cannot be re‐established by catheterisation or bile duct discontinuity exists.     

Diagnostic imaging of congenital porto-systemic shunts in dogs and cats: a review

An overview of clinical, laboratory, and diagnostic imaging features of congenital porto-systemic shunt (PSS) in dogs and cats is presented through the analysis of recent literature, and personal case log. Particular emphasis is given to diagnostic accuracy of ultrasonographic examination of PSS in the evaluation of shunt vessel anatomy, and of ancillary findings such as abnormalities of portal vein flow, portal branches, and liver size. Operative mesenteric portography to obtain information on PSS morphology and position, and quantitative hepatic scintigraphy, which allows the calculation of shunt fractions, are also described. Limitations for each diagnostic imaging technique are given.     

Hepatic ultrasonography in three breeds of healthy calves: Nellore,Curraleiro Pe-duro and Pantaneiro

An ultrasonography was performed in 21 healthy male calves of Nellore (n = 8), Curraleiro Pe-duro (n = 7) and Pantaneiro (n = 6) breeds, between 8 and 12 months, with the objective to display information about size, position and ultrasonographic parenchymal patterns of the liver, in addition to the topography of the gallbladder, right kidney and major vessels. The measurements used were dorsal margin distance (DMD) and ventral margin distance (VMD) of the liver, viewable extension (VE) of the liver, the caudal vena cava (CVC), width (CVCW) and depth (CVCD) and the portal vein (PV), width (PVW) and depth (PVD). The measures DMD, VMD and VE were similar, and the organ’s longest visible extension was in 11th ICS. CVC was more frequently observed in the 11th and 10th ICS, despite being visible from the 12th to the 9th ICS in Nellore and still 8th ICS in Curraleiro Pe-duro and Pantaneiro. CVCD was lower in the 10th and 9th ICS in Nellore. The PV presented higher observation frequency in the 10th ICS. The measures PVD and PVW were higher in Nellore in the 11th, 10th and 9th ICS. To our knowledge, this report is the first to document ultrasonographic findings in three healthy calves. Considering the three breeds, the results show no differences in the ultrasonographic features as regard to the measurements and visualization of the position, size and vasculature of the liver and there was no additional information about the topography of the gallbladder and the right kidney.     

Effect of breed on anatomy of portosystemic shunts resulting from congenital diseases in dogs and cats: a review of 242 cases

OBJECTIVE: To evaluate the effect of species and breed on the anatomy of portosystemic vascular anomalies in dogs and cats. DESIGN: Retrospective study of 233 dogs and nine cats presenting to the University Veterinary Centre, Sydney. METHODS: Case records were evaluated for breed, sex, age, anatomical and histological diagnosis. Cases were included when a portosystemic vascular anomaly resulted from a congenital or developmental abnormality of the liver or portal venous system. RESULTS: Disease conditions included single congenital portosystemic shunt with patent portal vasculature (214 dogs, nine cats), portal vein aplasia (nine dogs), multiple acquired shunts resulting from portal vein hypoplasia (seven dogs), biliary atresia (one dog) and microvascular dysplasia (one dog). One Maltese had a single, congenital shunt and multiple acquired shunts resulting from hepatic cirrhosis. Breeds that were significantly over-represented included the Maltese, Silky Terrier, Australian Cattle Dog, Bichon Frise, Shih Tzu, Miniature Schnauzer, Border Collie, Jack Russell Terrier, Irish Wolfhound and Himalayan cat. Bichon Frise with shunts were significantly more likely to be female than male (12:2, P < 0.001). Two hundred and fourteen dogs (91.4%), and all cats, had shunts that were amenable to attenuation. Inoperable shunts occurred in 19 dogs (8.2%). Fifty six of 61 (92%) operable shunts in large breed dogs were intrahepatic, versus 10/153 (7%) in small breeds (P < 0.0001). Breeds that were not predisposed to portosystemic shunts were significantly more likely to have unusual or inoperable shunts than dogs from predisposed breeds (29% versus 7.6%, P < 0.0001). No significant relationship between breed and shunt type could be determined in cats. CONCLUSION: Breed has a significant influence on shunt anatomy in dogs. Animals presenting with signs of portosystemic shunting may suffer from a wide range of operable or inoperable conditions. Veterinarians should be aware that unusual or inoperable shunts are much more likely to occur in breeds that are not predisposed to congenital portosystemic shunts.     

Ultrasonographic and histopathological features in 8 cats with fibrotic small intestinal stricture

Benign stricture is an uncommon cause of chronic small intestinal obstruction in the cat. The purpose of this retrospective case series was to describe the ultrasonographic features, histopathological findings, and clinical presentation in a group of cats with benign small intestinal stricture. Inclusion criteria were cats presenting during the period 2010‐2017, and that had ultrasonography and small intestinal stricture confirmed at surgery. For each cat, clinical data and ultrasonographic findings were retrieved from the medical record, and histopathology, where available, was reviewed. Eight cats met the inclusion criteria. The location of strictures was duodenum (1/8), mid‐ to distal jejunum (4/8), and ileum (3/8). Ultrasonographic findings included gastric distension (8/8) and generalized (3/8) or segmental (5/8) intestinal dilation consistent with mechanical obstruction. Ingesta did not propagate beyond the strictured segment. Wall thickening was mild to moderate (3‐6 mm). Normal wall layering was disrupted in all cats. Strictures were predominantly hypoechoic (7/8) and associated with hyperechoic peri‐intestinal mesentery (6/8). Annular strictures (5/8) were less than 15 mm in length whereas long‐segment strictures (3/8) were greater than 15 mm in length. Histopathology showed transmural disease with fibrosis and inflammation (8/8), often (6/8) extending into the bordering mesentery. The mucosa was the most severely affected layer and epithelial injury accompanied the mucosal fibrosis/inflammation. Clinical presentation reflected delayed diagnosis of chronic bowel obstruction with debilitation (8/8), marked weight loss (8/8), and prerenal azotemia (5/8). Benign fibrostenotic stricture should be considered a differential diagnosis in debilitated young cats presenting with chronic bowel disease and ultrasonographic features of intestinal obstruction.     

Sensitivity and specificity of fasting ammonia and serum bile acids in the diagnosis of portosystemic shunts in dogs and cats

Background: Portosystemic shunt (PSS) is the most common cause of hepatic encephalopathy in dogs and cats. Fasting ammonia and serum bile acids (SBA) are used to diagnose PSS, but their true sensitivity and specificity have not been fully evaluated, especially in cats. Objectives: The purpose of this study was to determine the diagnostic accuracy of fasting ammonia and SBA concentrations in the diagnosis of PSS in dogs and cats and to compare diagnostic accuracy between species. Methods: A retrospective analysis of data from 373 dogs and 85 cats presented to the clinic from 1996 to 2006 was carried out. Based on clinical, laboratory, and imaging findings, animals were grouped as having PSS, parenchymal hepatic disease, or extrahepatic disease. The sensitivity and specificity of ammonia and SBA concentrations for the diagnosis of PSS were calculated and receiver‐operating characteristic analysis was used to optimize cut‐offs. Results: Using the upper limit of laboratory reference intervals (ammonia, 59 μmol/L; SBA, 20 μmol/L), the sensitivity and specificity of ammonia was 85% and 86% in dogs, and 83% and 76% in cats, respectively. The sensitivity and specificity of SBA was 93% and 67% in dogs, and 100% and 71% in cats, respectively. Using optimal cut‐off points for ammonia (dogs, 57 μmol/L; cats, 94 μmol/L) the sensitivity and specificity was 91% and 84% in dogs and 83% and 86% in cats, respectively. Using optimal cut‐off points for SBA (dogs, 58 μmol/L; cats, 34 μmol/L) the sensitivity and specificity was 78% and 87% in dogs and 100% and 84% in cats. Conclusion: Increased fasting ammonia and SBA concentrations are accurate indicators of PSS. An improvement in diagnostic accuracy can be achieved by using defined optimal cut‐off points for the selective diagnosis of PSS.     

Ultrasonographic size of the canine parathyroid gland may not correlate with histopathology

Accurate ultrasonographic differentiation of normal versus abnormal parathyroid glands is important for clinical workup and presurgical screening in dogs with hypercalcemia. In previous published studies, size has been the only ultrasonographic criterion correlated with histologic diagnoses of abnormal parathyroid glands. In this retrospective, cross‐sectional study, the medical records of dogs with ultrasonographic examinations of the parathyroid glands and histologic diagnoses of parathyroid gland hyperplasia, adenoma, and adenocarcinoma were evaluated. Ultrasonographic characteristics were recorded for each gland and compared among histologic diagnosis groups. A total of 49 dogs and 59 parathyroid glands were sampled and assigned to the following groups for analyses: adenoma (n = 24), hyperplastic (n = 20), and adenocarcinoma (n = 15). There were no associations with dog age, sex, weight, breed; or gland laterality, location, ultrasonographic shape, or echogenicity among histologic diagnosis groups (P > .05). Parathyroid gland adenocarcinomas were found to be less likely to have a homogeneous echotexture on ultrasonographic evaluation, with hyperplastic glands being smaller (P = .022) and adenocarcinomas being larger (P = .042). While 3 mm was the optimum cutoff for differentiating hyperplastic and neoplastic parathyroid glands in this sample of dogs, values varied widely within groups and there were overlapping values between groups. Therefore, authors caution against using ultrasonographic size as a sole criterion for differentiating hyperplasia from neoplasia and normal versus abnormal parathyroid glands.     

Suppurative cholangitis in cats

Suppurative cholangitis in 5 aged cats was characterized clinically by weight loss, depression, dehydration, icterus, and fever. The major abnormal laboratory findings were a severe left shift of WBC and a high, conjugated bilirubin concentration consistent with an inflammatory process and cholestasis. Gross pathologic findings included periductal biliary fibrosis (4 cats), periductal pancreatic fibrosis (2 cats), cholelithiasis (2 cats), deformation of the gallbladder (2 cats), and chronic interstitial pancreatitis (2 cats). Histopathologic findings in all cases were portal hepatic fibrosis, biliary hyperplasia, and suppurative exudate within dilated intrahepatic biliary ducts. Weight loss and portal fibrosis were suggestive of chronic, intermittent illness. The pathogenesis appeared to involve invasion of the bile duct by enteric bacteria. Cholangitis was observed to occur in association with pancreatitis, cholelithiasis, or anatomic abnormalities of the biliary tract.     

Hepatic lesions associated with intrahepatic arterioportal fistulae in dogs

Seven cases of hepatic arterioportal fistulae in young dogs (mean age 6 months) are described. All cases were presumed to be congenital in origin. The onset of clinical signs, which frequently included gastrointestinal and neurological disturbances, was usually sudden. All dogs had clinical evidence of portal hypertension in the form of ascites, and all developed multiple extrahepatic portacaval venous shunts consequential to portal hypertension. The neurological disturbances were likely the result of portacaval shunting. The arterial and venous vessels involved in the fistulae had markedly altered wall structure. Hepatic regions adjacent to the fistulae frequently evidenced marked bile duct proliferation. Hepatic parenchymal atrophy, relative collapse of distributing portal veins, dilatation of hepatic arterial branches and proliferation of hepatic arterioles were seen throughout the liver; these changes closely resembled those present with portacaval shunting in the absence of hepatic arterioportal fistulae. The importance of recognizing that hepatic arterioportal fistulae and multiple extrahepatic portacaval shunts usually coexist and separately influence the morphological appearance of the liver is stressed.     

Effect of catheter size and injection rate of contrast agent on enhancement and image quality for triple‐phase helical computed tomography of the liver in small dogs

Rapid contrast injection is recommended for triple‐phase helical computed tomography (CT) of the liver. However, a large‐gauge catheter is needed for faster contrast injection and this is not practical for small breed dogs or cats. The purpose of this crossover group study was to evaluate applicability of a lower injection rate with a small‐gauge (G) catheter for triple‐phase hepatic CT in small dogs. Triple‐phase CT images were acquired for six beagle dogs using three protocols: an injection rate of 1.5 ml/s with a 24 G catheter, 3.0 ml/s with a 22 G catheter, and 4.5 ml/s with a 20 G catheter. Enhancement of the aorta, portal vein, and hepatic parenchyma was measured in each phase (arterial, portal, and delayed) and image quality was scored subjectively by two observers. Injection duration, time to scan delay, and time to peak enhancement were also recorded. Contrast injection duration decreased with a higher injection rate (n = 6, P ≤ 0.01), but time to peak enhancement and time to scan delay were not significantly affected by injection rates and catheter sizes. Contrast injection rate did not significantly affect aortic, portal, and hepatic enhancement. In addition, separation between each phase and quality of images was subjectively scored as good regardless of injection rate. Findings from the current study supported using an injection rate of 1.5 ml/s with a catheter size of 24 G for triple‐phase hepatic CT in small dogs (weight < 12 kg).     

REPEATABILITY OF A PLANNING TARGET VOLUME EXPANSION PROTOCOL FOR RADIATION THERAPY OF REGIONAL LYMPH NODES IN CANINE AND FELINE PATIENTS WITH HEAD TUMORS

For canine and feline patients with head tumors, simultaneous irradiation of the primary tumor and mandibular and retropharyngeal lymph nodes (LNs) is often indicated. The purpose of this study was to assess the repeatability of a planning target volume (PTV) expansion protocol for these LNs. Two CT image sets from 44 dogs and 37 cats that underwent radiation therapy for head tumors were compared to determine LN repositioning accuracy and precision; planning‐CT (for radiation therapy planning) and cone‐beam CT (at the time of actual treatment sessions). Eleven percent of dogs and 65% of cats received treatment to their LNs. In dogs, the mandibular LNs were positioned more caudally (P = 0.0002) and the right mandibular and right retropharyngeal LNs were positioned more to the left side of the patient (P = 0.00015 and P = 0.003, respectively). In cats, left mandibular LN was positioned higher (toward roof) than the planning‐CT (P = 0.028). In conclusion, when the patient immobilization devices and bony anatomy matching are used to align the primary head target and these LNs are treated simultaneously, an asymmetrical PTV expansion that ranges 4–9 mm (dogs) and 2–4 mm (cats), depending on the directions of couch movement, should be used to include the LNs within the PTV at least 95% of the time.     

Ex vivo binding of the immunosuppressant mycophenolic acid to dog and cat plasma proteins and the effect of co‐incubated dexamethasone and prednisolone

Mycophenolic acid (MPA) has been shown to be promising for the treatment of autoimmune diseases in dogs and cats. In humans, MPA is highly bound to plasma proteins (~97%). It has been recommended to monitor free drug plasma concentrations because the free MPA correlates with its immunosuppressive effect. However, it is unknown if MPA is highly bound to plasma proteins in dogs and cats. The objectives of this study were to determine the extent of plasma protein binding of MPA and evaluate the effect of prednisolone and dexamethasone on the extent of protein binding of MPA in dogs and cats. The extent of plasma protein binding of MPA was determined in plasma collected from clinically healthy adult cats (n = 13) and dogs (n = 14) by combining high‐throughput dialysis and ultra‐high‐liquid chromatography. This study reveals that MPA is highly bound to plasma proteins (>90%) in dogs and cats, mean extent of binding of MPA at 15 μg/ml to plasma proteins being 96% (range, 95%–97%) and 92% (range, 90%–93%) for dogs and cats, respectively. In dog plasma, MPA is primarily bound to albumin. In vitro, prednisolone increased the unbound MPA in dogs (p < .01) but not in cats (p = .07) while dexamethasone had no effect on MPA plasma binding in either species (p > .05). Results of this study provide valuable information for designing future pharmacokinetic and pharmacodynamic studies and also therapeutic monitoring programs for dogs and cats.