P.H. Kass

Magnetic resonance imaging and histological classification of intracranial meningiomas in 112 dogs.

BACKGROUND Intracranial meningiomas are the most common primary brain tumors in dogs. Classification of meningiomas by tumor grade and subtype has not been reported, and the value of magnetic resonance imaging (MRI) characteristics for predicting tumor subtype and grade has not been investigated. HYPOTHESIS Canine intracranial meningiomas are a heterogenous group of tumors with differing histological subtypes and grades. Prediction of histopathological classification is possible based on MRI characteristics. ANIMALS One hundred and twelve dogs with a histological diagnosis of intracranial meningioma. METHODS Retrospective observational study. RESULTS Meningiomas were overrepresented in the Golden Retriever and Boxer breeds with no sex predilection. The incidence of specific tumor grades was 56% benign (Grade I), 43% atypical (Grade II), and 1% malignant (Grade III). Grade I histological subtypes included meningothelial (43%), transitional (40%), microcystic (8%), psammomatous (6%), and angiomatous (3%). No statistically significant (P < .05) associations were found among tumor subtype or grade and any of the MRI features studied. CONCLUSIONS AND CLINICAL IMPORTANCE Meningiomas in dogs differ from their counterparts in humans mainly in their higher incidence of atypical (Grade II) tumors observed. MRI characteristics do not allow for prediction of meningioma subtype or grade, emphasizing the necessity of histopathology for antemortem diagnosis. The higher incidence of atypical tumors in dogs may contribute to the poorer therapeutic response in dogs with meningiomas as compared with the response in humans with meningiomas.

Canine Lymphomas Association of Classification Type, Disease Stage, Tumor Subtype, Mitotic Rate, and Treatment With Survival

Canine lymphoma is the neoplasm most often treated by chemotherapy, yet there are few data to correlate response to therapy with its different subtypes. This study is based on biopsy specimens from 992 dogs for which lymphoma was the clinical diagnosis. All cases were phenotyped by immunohistochemistry for CD3 and CD79alpha. Cases with histiocytic proliferation were evaluated immunohistochemically for CD18. Clonality was verified in 12 cases by polymerase chain reaction (PCR). Survival (event time) data and complete survival information (cause of death or time to last follow-up) were available on 456 dogs. Additional covariate information when available included size, age, sex, phenotype, stage and grade of lymphoma, mitotic index, and treatment protocol. Because of the many subtypes of B- and T-cell lymphoma, the cases were grouped into 7 diagnostic categories: (1) benign hyperplasia; (2) low-grade B-cell; (3) high-grade B- and T-cell; (4) low-grade T-cell; (5) centroblastic large B-cell of all mitotic grades (subdivided by clinical stage); (6) immunoblastic large B-cell of all mitotic grades, and (7) high-grade peripheral T-cell. Grouping was determined by histological grade (based on mitotic rate/400× field, with low-grade 0–5, intermediate 6–10, and high-grade >10) and stage for survival function estimation. No association with survival was found for size (based on breed of dog) or sex. All diagnostic categories of indolent or low-grade type had low mitotic rates, whereas those with clinically high grades had high mitotic rates. The diagnostic category with the most cases was centroblastic large B-cell lymphoma. Compared with dogs in this largest represented group of lymphomas, dogs with high-grade lymphomas had significantly higher mortality rates, and dogs with low-grade T-cell lymphomas had significantly lower mortality rates. Treatments for high-, intermediate-, and low-grade lymphomas were divided into 4 groups: absence of treatment, chemotherapy with or without hydroxydaunorubicin, and only prednisone. Dogs with low-grade T-cell (T-zone) lymphomas had the longest median survival (622 days), whereas the shortest median survival was in dogs with T-cell high-grade (peripheral T-cell) subtype (162 days). The dogs with centroblastic large B-cell lymphomas had a median survival of 127 days with low stage, 221 days with intermediate stage, and 215 days with advanced stage. Dogs with T-zone lymphoma were probably diagnosed in later stages of disease because of the lack of signs associated with progression. As with human lymphomas, a histological diagnosis with immunophenotyping is a minimal requirement for diagnosis of a specific subtype.

Choroid Plexus Tumors in 56 Dogs (1985–2007)

BACKGROUND Choroid plexus tumors (CPTs) comprise approximately 10% of all primary brain tumors in dogs. The clinical utility of magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) analysis, or both in the presumptive diagnosis of CPTs has not been determined. OBJECTIVES To report MRI and CSF findings in dogs with CPT and determine if there are distinguishing features that allow clinical discrimination between the tumor grades. ANIMALS Fifty-six client-owned dogs with naturally occurring CPT. METHODS Retrospective case series. The inclusion criterion was histologically confirmed CPT. Blinded review of cranial MRI and cisternal CSF analysis was performed. RESULTS Thirty-six of 56 dogs had a choroid plexus carcinoma (CPC) and 20 had a choroid plexus papilloma (CPP). Golden Retrievers were overrepresented compared with the hospital population (frequency 3.7 times that expected, confidence interval 95%= 2.0-6.7, P< .0002). Median CSF protein concentration in CPCs (108 mg/dL, range 27-380 mg/dL) was significantly higher than in CPPs (34 mg/dL, range 32-80 mg/dL) (P= .002). Only dogs with CPCs had a CSF protein concentration >80 mg/dL. Cytological evidence of malignancy in CSF was seen in 7 of 15 CPCs. Only CPCs had evidence of intraventricular or subarachnoid metastases on MRI. CONCLUSIONS AND CLINICAL IMPORTANCE MRI, CSF analysis or both can help to differentiate between CPPs and CPCs, and may provide valuable prognostic and pretreatment information.

Sensitivity and Specificity of Canine Pancreas‐Specific Lipase (cPL) and Other Markers for Pancreatitis in 70 Dogs with and without Histopathologic Evidence of Pancreatitis

BACKGROUND Pancreatitis is a common disorder in dogs for which the antemortem diagnosis remains challenging. OBJECTIVES To compare the sensitivity and specificity of serum markers for pancreatitis in dogs with histopathologic evidence of pancreatitis or lack thereof. ANIMALS Seventy dogs necropsied for a variety of reasons in which the pancreas was removed within 4 hours of euthanasia and serological markers were evaluated within 24 hours of death. METHODS Prospective study: Serum was analyzed for amylase and lipase activities, and concentrations of canine trypsin-like immunoreactivity (cTLI) and canine pancreas-specific lipase (cPL). Serial transverse sections of the pancreas were made every 2 cm throughout the entire pancreas and reviewed using a semiquantitative histopathologic grading scheme. RESULTS The sensitivity for the Spec cPL (cutoff value 400 μg/L) was 21 and 71% in dogs with mild (n = 56) or moderate-severe pancreatitis (n = 7), and 43 and 71% (cutoff value 200 μg/L), respectively. The sensitivity for the cTLI, serum amylase, and lipase in dogs with mild or moderate-severe pancreatitis was 30 and 29%; 7 and 14%; and 54 and 71%, respectively. The specificity for the Spec cPL based on 7 normal pancreata was 100 and 86% (cutoff value 400 and 200 μg/L, respectively), whereas the specificity for the cTLI, serum amylase, and lipase activity was 100, 100, and 43%, respectively. CONCLUSION AND CLINICAL IMPORTANCE The Spec cPL demonstrated the best overall performance characteristics (sensitivity and specificity) compared to other serum markers for diagnosing histopathologic lesions of pancreatitis in dogs.

A Novel Clinical Scoring System for Outcome Prediction in Dogs with Acute Kidney Injury Managed by Hemodialysis

BACKGROUND No reliable tool to predict outcome of acute kidney injury (AKI) exists. HYPOTHESIS A statistically derived scoring system can accurately predict outcome in dogs with AKI managed with hemodialysis. ANIMALS One hundred and eighty-two client-owned dogs with AKI. METHODS Logistic regression analyses were performed initially on clinical variables available on the 1st day of hospitalization for relevance to outcome. Variables with P< or = .1 were considered for further analyses. Continuous variables outside the reference range were divided into quartiles to yield quartile-specific odds ratios (ORs) for survival. Models were developed by incorporating weighting factors assigned to each quartile based on the OR, using either the integer value of the OR (Model A) or the exact OR (Models B or C, when the etiology was known). A predictive score for each model was calculated for each dog by summing all weighting factors. In Model D, actual values for continuous variables were used in a logistic regression model. Receiver-operating curve analyses were performed to assess sensitivities, specificities, and optimal cutoff points for all models. RESULTS Higher scores were associated with decreased probability of survival (P < .001). Models A, B, C, and D correctly classified outcomes in 81, 83, 87, and 76% of cases, respectively, and optimal sensitivities/specificities were 77/85, 81/85, 83/90 and 92/61%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE The models allowed outcome prediction that corresponded with actual outcome in our cohort. However, each model should be validated further in independent cohorts. The models may also be useful to assess AKI severity.

Expression of receptor tyrosine kinases VEGFR-1 (FLT-1), VEGFR-2 (KDR), EGFR-1, PDGFRa and c-Met in canine primary brain tumours

Inhibition of tumour growth and angiogenesis by targeting key growth factor receptors is a promising therapeutic strategy for central nervous system tumours. Characterization of these growth factor receptors in canine primary brain tumours has not been done. Using quantitative real-time TaqMan polymerase chain reaction (PCR), we evaluated the expression of messenger RNA (mRNA) for five tyrosine kinase growth factor receptors (vascular endothelial growth factor receptor [VEGFR]-1, VEGFR-2, endothelial growth factor receptor [EGFR]-1, platelet-derived growth factor receptor a [PDGFRa], and c-Met) relative to normal cerebral cortex in 66 spontaneous canine primary brain tumours. Increased expression of VEGFR-1 and VEGFR-2 mRNA was greatest in grade IV astrocytomas (glioblastoma multiforme) and grade III (anaplastic) oligodendrogliomas. EGFR-1 mRNA expression was more consistently increased than the other receptors in all tumour types, while increased PDGFRa mRNA expression was mostly restricted to oligodendrogliomas. The similarities in increased expression of these tyrosine kinase growth factor receptors in these canine tumours, as compared to data from their human counterparts, suggest that common molecular mechanisms may be present.

Predictive Factors and the Effect of Phenoxybenzamine on Outcome in Dogs Undergoing Adrenalectomy for Pheochromocytoma

BACKGROUND Some studies in dogs undergoing adrenalectomy for pheochromocytoma suggest that anesthetic complications and perioperative mortality are common. In humans, surgical outcome has improved with the use of phenoxybenzamine (PBZ) before adrenalectomy. HYPOTHESIS Dogs treated with PBZ before adrenalectomy have increased survival compared with untreated dogs. ANIMALS Forty-eight dogs that underwent adrenalectomy for pheochromocytoma. METHODS A retrospective medical record review for dogs that underwent adrenalectomy for pheochromocytoma at a veterinary medical teaching hospital over the period from January 1986 through December 2005. RESULTS Twenty-three of 48 dogs were pretreated with PBZ (median dosage: 0.6 mg/kg PO q12h) for a median duration of 20 days before adrenalectomy. Duration of anesthesia and surgery, percentage of dogs with pheochromocytoma involving the right versus left adrenal gland, size of tumor, and presence of vascular invasion were similar for PBZ-treated and untreated dogs. Thirty-three (69%) of 48 dogs survived adrenalectomy in the perioperative period. PBZ-treated dogs had a significantly (P = .014) decreased mortality rate compared with untreated dogs (13 versus 48%, respectively). Additional significant prognostic factors for improved survival included younger age (P = .028), lack of intraoperative arrhythmias (P = .0075), and decreased surgical time (P = .0089). CONCLUSIONS AND CLINICAL IMPORTANCE Results from this retrospective study support treatment with PBZ before surgical removal of pheochromocytoma in dogs.

Effect of spironolactone on diastolic function and left ventricular mass in Maine coon cats with familial hypertrophic cardiomyopathy

BACKGROUND Myocardial fibrosis occurs in cats with hypertrophic cardiomyopathy (HCM), and is one factor that leads to diastolic dysfunction. Spironolactone (SPIR) reduces myocardial fibrosis in several models of HCM and in humans with cardiac disease. HYPOTHESIS SPIR will improve diastolic function and reduce left ventricular (LV) mass in Maine Coon cats with HCM. METHODS Maine Coon cats with familial HCM were included if there was concentric hypertrophy (> or =6 mm end diastolic wall thickness) and decreased early lateral mitral annular velocity (Em) or summated early and late mitral annular velocity (EAsum) measured by pulsed wave tissue Doppler imaging echocardiography. Cats were paired by Em-EAsum and randomized to receive 2 mg/kg SPIR (n = 13) or placebo (n = 13) PO q12 h for 4 months. Em-EAsum, systolic velocity, LV mass, and the ratio of left atrial to aortic diameter were measured at baseline, 2 months, and 4 months. Statistical analysis included 2-way repeated measures analysis of variance and the Students t-test. RESULTS Plasma aldosterone concentration increased in cats treated with SPIR (235 ng/mL, baseline; 935 ng/mL, 2 months; 1,077 ng/mL, 4 months; P < .001 at 2 and 4 months). No significant treatment effect was identified for early or early-late summated diastolic mitral annular velocity or any other variable except plasma aldosterone concentration. Severe facial ulcerative dermatitis developed in 4 of 13 cats treated with SPIR, requiring discontinuation of the drug. CONCLUSION SPIR did not improve Em or EAsum of the lateral mitral annulus or alter LV mass over 4 months. One third of cats treated with SPIR developed severe ulcerative facial dermatitis.

Canine Intraspinal Meningiomas: Imaging Features, Histopathologic Classification, and Long‐Term Outcome in 34 Dogs

BACKGROUND Meningioma is the most common primary intraspinal nervous system tumor in dogs. Clinical findings, clinicopathologic data, and treatment of these tumors have been reported sporadically, but little information is available regarding cerebrospinal fluid (CSF) analysis, histologic tumor grade, or efficacy of radiation therapy as an adjunct to cytoreductive surgery. ANIMALS Dogs with histologically confirmed intraspinal meningiomas (n = 34). METHODS A retrospective study of dogs with intraspinal meningiomas between 1984 and 2006 was carried out. Signalment, historical information, physical examination, clinicopathologic data, radiation therapy protocols, surgery reports, and all available images were reviewed. All tumors were histologically classified and graded as defined by the international World Health Organization classification scheme for central nervous system tumors. RESULTS Intraspinal mengiomas in dogs are most common in the cervical spinal cord but can be found throughout the neuraxis. Location is correlated with histologic grade, with grade I tumors more likely to be in the cervical region than grade II tumors. Myelography generally shows an intradural extramedullary compressive lesion. On magnetic resonance imaging, the masses are strongly and uniformly contrast enhancing and a dural tail often is present. CSF analysis usually shows increased protein concentration with mild to moderate mixed pleocytosis. Surgical resection is an effective means of improving neurologic status, and adjunctive radiation therapy may lead to an improved outcome. CONCLUSIONS AND CLINICAL IMPORTANCE Biopsy is necessary for definitive diagnosis, but imaging and CSF analysis can suggest a diagnosis of meningioma. Treatment of meningiomas with surgery and radiation therapy can result in a fair to excellent prognosis.

Risk factors for the elimination of endurance horses from competition

OBJECTIVE To identify risk factors such as signalment, previous competition miles completed, ride characteristics, and physical examination variables associated with the elimination of horses during endurance competitions. DESIGN Retrospective observational study. SAMPLE Veterinary records for 3,493 endurance horse competition starts. PROCEDURES Records were requested of all sanctioned 2007 endurance horse competitions in the United States. Only rides that provided data from all horses were included. The horses signalment, previous endurance competition record, specific ride characteristics, weight division (ie, based on riders weight with tack), and physical examination variables throughout the ride were included for analysis. Examination variables were separated into abnormalities occurring prior to the start of the ride, during the first half of the ride, and during the second half of the ride. Multivariate logistic regression was used to identify risk factors for overall elimination and elimination subcategories (lameness and metabolic). RESULTS Specific breeds, the heavyweight division, and distance of the ride were all associated with an increased risk of elimination. A variety of examination variables prior to the start of the ride and during the ride were associated with elimination and included heart rate, cardiac recovery index, and abnormal gastrointestinal sounds. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that specific risk factors were associated with elimination of horses from endurance competitions. These factors may be used to help identify horses at higher risk for elimination and prevent morbidity associated with competition.