Endocrine hypertension in small animals

Circulating renin‐angiotensin‐aldosterone system activity in cats with systemic hypertension or cardiomyopathy

Background

Activity of the circulating renin‐angiotensin‐aldosterone system (RAAS) has not been comprehensively characterized in cats with systemic hypertension (SH) or cardiomyopathy (CM), and the effects of furosemide or amlodipine treatment on the RAAS have not been fully evaluated in cats.

Hypothesis/Objectives

To document RAAS activity in cats with SH or CM compared to healthy cats and determine how RAAS profiles change with furosemide or amlodipine treatment.

Animals

Sixty‐six client‐owned cats: 15 with SH (7 amlodipine‐treated, 8 untreated), 17 with advanced CM (7 furosemide‐treated, 10 not furosemide‐treated), and 34 healthy cats.

Methods

Equilibrium concentrations of RAAS peptides and aldosterone were quantified in serum samples by liquid chromatography‐mass spectrometry. Variables were compared between groups using Kruskal‐Wallis analysis with post hoc Holms‐corrected Dunn's testing.

Results

Compared with healthy cats, cats with CM had higher concentrations of angiotensin I, aldosterone, and plasma renin activity (all P < .01), and these differences remained significant (P < .03) after considering subgroups of untreated or furosemide‐treated cats. Compared with healthy cats, untreated cats with SH showed no differences in RAAS biomarkers, whereas amlodipine‐treated cats had higher concentrations of angiotensins I, II, III, IV, and 1‐7, aldosterone, and plasma renin activity (all P < .03). Multivariable analysis determined that furosemide and amlodipine treatments were independent predictors of increased RAAS biomarker concentrations.

Conclusions and Clinical Importance

Cats with CM had increased RAAS activity, whereas cats with untreated SH did not. Furosemide and amlodipine both led to nonspecific activation of both classical and alternative RAAS pathways in cats.

Metabolic profiling of serum from dogs with pituitary-dependent hyperadrenocorticism

Hyperadrenocorticism (HAC) is one of the most common endocrine diseases in dogs characterized by excessive cortisol production caused by an adrenocorticotropic hormone (ACTH)-secreting tumor, namely pituitary-dependent HAC (PDH) or cortisol-secreting adrenal tumor. Metabolomics presents the ability to identify small molecule metabolites. Thus, the use of metabolomics techniques in canine PDH can provide information about the pathophysiology and metabolic changes in this disease. This study aimed to identify and compare differences in serum metabolites between dogs with PDH and healthy dogs. The metabolomic profile of 20 dogs diagnosed with PDH was compared with 20 healthy dogs using liquid chromatography/mass spectrometry (LC/MS), and metabolite discrimination was performed using partial least squares-discriminant analysis (PLS-DA), the variable important in projection (VIP) and fold changes (FC) group-wise comparisons. The hypergeometric test identified the significantly altered pathways. A total of 21 metabolites were found to be significantly different between the two groups. The major alterations were found in arachidonic and decanoic acid, and phospholipids related to phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI). These metabolites are related to insulin resistance and other complications (i.e. hypertension). Our results indicate that PDH produces changes in serum metabolites of dogs, and the knowledge of these changes can aid to better understanding of pathophysiological processes involved and contribute to potentially detect new biomarkers for this disease.

Ocular fundus abnormalities in cats affected by systemic hypertension: Prevalence, characterization, and outcome of treatment

OBJECTIVES

To determine the prevalence of ocular fundus abnormalities in cats with a diagnosis of systemic hypertension, to characterize the abnormalities observed, and to evaluate ophthalmoscopic evolution during treatment with amlodipine besylate.

ANIMALS STUDIED

Cats diagnosed as affected by SHP in a 2-year period.

PROCEDURES

Systemic hypertension was assessed by oscillometric blood pressure measurement, and its etiology was also established. All the cats received an ophthalmic examination, and ocular lesions were classified with a score from 0 (no abnormalities) to 4 (severe abnormalities). All cats received amlodipine besylate by mouth, and those that showed fundus abnormalities were regularly rechecked from 7 to 365 days after diagnosis. Data were statistically analyzed to compare P_sys and P_dia with all the variables and to correlate P_sys and P_dia with the fundus score.

RESULTS

A total of 225 cats were enrolled in the study, and the prevalence of fundus abnormalities was 58.6% (21.2%: grade 1; 18.2%: grade 2; 36.4%: grade 3; and 24.2%: grade 4). Systemic hypertension was diagnosed concurrently with chronic renal failure (60.4%), hyperthyroidism (28.9%), both chronic renal failure and hyperthyroidism (7.6%), and hypertrophic myocardiopathy (3.1%). A significant effect of P_sys values on the fundus score was detected. Amlodipine therapy improved fundus abnormalities in 50% of cases at the 21-day follow-up.

CONCLUSIONS

This study showed that fundus abnormalities are common in hypertensive cats at the time of the systemic diagnosis, and most of the abnormalities are moderate to severe. Treatment with amlodipine appeared to improve ophthalmic lesions over time.

Prevalence and risk factors associated with systemic hypertension in dogs with spontaneous hyperadrenocorticism

Background

Systemic hypertension (SH) is common in dogs with hyperadrenocorticism (HAC) however there are not many studies assessing its prevalence and risk factors.

Objectives

To determine the prevalence and severity of SH in dogs with HAC and its association with clinical and laboratory findings to identify potential risk factors.

Animals

Sixty‐six client owned dogs with spontaneous HAC.

Methods

Retrospective cross‐sectional study. Medical records of dogs with HAC were reviewed. Systolic blood pressure (SBP) was measured using Doppler ultrasonography. Clinical signs, physical examination findings and clinicopathologic data (CBC, serum biochemistry and electrolytes, urinalysis and urinary culture, and adrenal function tests) were reviewed for analysis.

Results

Prevalence of SH (≥150 mm Hg) was 82% (54/66) and prevalence of severe SH (≥180 mm Hg) was 46% (30/66). All dogs with thrombocytosis had SH (P = .002), and a platelet count ≥438 × 10³/μL was 100% specific and 61.1% sensitive to predict SH (AUC = .802, P = .001). Median potassium levels were lower in hypertensive dogs (4.1 mEq/L, range 3.1‐5.4 mEq/L) than in normotensive ones (4.5 mEq/L, range 4.0‐5.0 mEq/L) (P = .007). Dogs with UPC ≥ 0.5 had higher median SBP than those without proteinuria (P = .03). Dogs with concurrent diabetes mellitus seemed to have a reduced risk of SH (OR = .118, 95%CI = .022‐.626, P = .02).

Conclusions and Clinical Importance

Systemic hypertension is common in dogs with HAC and is frequently severe. Blood pressure should be routinely assessed in these dogs, especially if thrombocytosis, proteinuria or low potassium concentrations are present.

Evaluation of dose-response effects of short-term oral prednisone administration on clinicopathologic and hemodynamic variables in healthy dogs

OBJECTIVE

To determine whether a dose-response relationship exists between short-term oral prednisone administration and common clinicopathologic variables, cardiovascular biomarkers, and systolic arterial blood pressure (SAP) in healthy dogs.

ANIMALS

8 healthy Beagles.

PROCEDURES

Dogs underwent five 5-day experiments (no prednisone treatment [control condition] and prednisone administration at 0.5, 1, 2, and 4 mg/kg, PO, q 24 h), with a 9-day washout period between protocols. Analyses performed before and after treatments included a CBC, serum biochemical analysis, and determination of SAP, fractional excretion of electrolytes, urine protein-to-creatinine ratio, glomerular filtration rate (GFR), serum N-terminal pro B-type natriuretic peptide (NT-proBNP) and plasma cortisol concentrations, and plasma renin activity. Linear mixed-effects modeling was used to compare changes in variables from baseline (day 1 for the same experiment) among treatment conditions.

RESULTS

Changes in serum glucose concentration and GFR were significantly greater after administration of prednisone at 4 mg/kg than for the control condition. Fractional excretion of sodium was decreased from baseline when dogs received 0.5, 1, or 4 mg of prednisone/kg, compared with results for the control condition. Several expected changes in clinicopathologic values were observed after prednisone administration at any dose. Changes in serum NT-proBNP concentration, plasma renin activity, and SAP did not differ from changes for the control condition at any prednisone dose.

CONCLUSIONS AND CLINICAL RELEVANCE

Oral prednisone administration did not affect SAP, NT-proBNP concentration, or measures of renin-angiotensin-aldosterone system activation in healthy laboratory-housed dogs but was associated with relative increases in GFR and serum glucose concentration.

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.

Subconjunctival haemorrhage in 147 dogs

OBJECTIVES

To identify differential diagnoses for subconjunctival haemorrhage in dogs.

MATERIALS AND METHODS

Retrospective case series.

RESULTS

Of 147 dogs with subconjunctival haemorrhage, 119 had a history of trauma. The most common types of injury were vehicular trauma (47/119) and dog attacks (32/119). Confirmed or suspected non-accidental injury was reported for 5/119. Of the 28 dogs without a history of trauma, 13 had a bleeding disorder and of these, immune-mediated thrombocytopenia was the most common diagnosis (9/13). Other causes included seizure disorders (4/28), vasculitis (3/28) and ocular or periocular disease (3/28).

CLINICAL SIGNIFICANCE

Subconjunctival haemorrhage in dogs can be secondary to a wide range of injuries and systemic diseases, bleeding diathesis or ocular disease.

Diagnosis of spontaneous hyperadrenocorticism in dogs. Part 1: Pathophysiology, aetiology, clinical and clinicopathological features

Hyperadrenocorticism is a relatively common endocrine disorder in dogs. It occurs as a result of a functional pituitary or adrenal tumour, although other causes have been rarely reported. Canine hyperadrenocorticism has been extensively described but diagnosing this disease remains challenging. Few studies have investigated the clinical and clinicopathological features helpful in differentiating dogs with hyperadrenocorticism from dogs in which the disease is suspected but eventually excluded. Ultimately the diagnosis is based on a combination of multiple pieces of information emanating from the signalment, history, clinical findings, and a variety of diagnostic tests. The first part of this review aims to critically appraise the available data on epidemiology, clinical and laboratory features of naturally occurring canine hyperadrenocorticism.

Computed Tomographic Angiography of the Pancreas in Cats with Chronic Diabetes Mellitus Compared to Normal Cats

Background

Diabetes mellitus (DM) is a common endocrinopathy in cats. No known diagnostic test or patient characteristic at the time of diagnosis can predict likely disease course, unlike in people in whom computed tomographic angiography (CTA) is used. No published data exist regarding the CTA appearance of the pancreas in cats with DM, and thus, it is unknown what if any CTA variables should be further assessed for associations with pancreatic endocrine function.

Hypothesis/Objectives

A significant difference in pancreatic attenuation, volume, and size will be identified between normal cats and those with chronic DM on CTA.

Animals

Ten healthy control cats and 15 cats with naturally occurring DM present for >12 months.

Methods

Prospective cross‐sectional study comparing pancreatic attenuation, enhancement pattern, size, volume, pancreatic volume‐to‐body weight ratio (V:BW), pancreatic arterial: portal phase ratio (A:P), time‐to‐arterial enhancement, and time‐to‐peak portal enhancement on CTA between sedated healthy control cats and those with chronic DM.

Results

The pancreas in cats with chronic DM was significantly larger, had higher volume, higher V:BW, and shorter time‐to‐peak portal enhancement on CTA when compared to normal cats.

Conclusions and Clinical Importance

Peak portal enhancement time, pancreatic size, pancreatic volume, and V:BW can be used to differentiate normal sedated cats from those with chronic DM by CTA. These variables warrant further investigation to identify possible associations with endocrine function.

Urine protein electrophoresis study in dogs with pituitary dependent hyperadrenocorticism during therapy with trilostane

ABSTRACT: Hyperadrenocorticism is one of the most common endocrine disorders in dogs. Regarding to the kidneys, chronic hypercortisolemia can cause damage to the glomerulus, and evolve into chronic kidney disease. This study evaluated nine normotensive dogs with pituitary dependent hyperadrenocorticism, before and after therapy with trilostane, during the follow-up period of six months, in order to investigate the development of pathological proteinuria by quantitative (urinary protein-to-creatinine ratio) and qualitative (urinary protein electrophoresis) methods, and also to monitor its intensity over the course of the disease and therapy. The main renal lesion detected in dogs with hyperadrenocorticism was in the tubular segment, evidenced by the prevalence of urinary protein bands of lower molecular weight, indicating the lack absorption of these proteins in the proximal segment of the nephron. Low molecular weight proteins persisted throughout the follow-up. Regarding the future of routine veterinary medical clinic in the care of patients with hyperadrenocorticism, the assessments of proteinuria determinations by the urinary protein-to-creatinin ratio and urinary protein electrophoresis, according to the results obtained in this study, can add more information about the renal damage in these animals, and contribute to the prognosis.

ISFM Consensus Guidelines on the Diagnosis and Management of Hypertension in Cats

Practical relevance: Feline hypertension is a common disease in older cats that is frequently diagnosed in association with other diseases such as chronic kidney disease and hyperthyroidism (so-called secondary hypertension), although some cases of apparent primary hypertension are also reported. The clinical consequences of hypertension can be severe, related to 'target organ damage' (eye, heart and vasculature, brain and kidneys), and early diagnosis followed by appropriate therapeutic management should help reduce the morbidity associated with this condition. Clinical challenges: Despite being a common disease, routine blood pressure (BP) monitoring is generally performed infrequently, probably leading to underdiagnosis of feline hypertension in clinical practice. There is a need to: (i) ensure BP is measured as accurately as possible with a reproducible technique; (ii) identify and monitor patients at risk of developing hypertension; (iii) establish appropriate criteria for therapeutic intervention; and (iv) establish appropriate therapeutic targets. Based on current data, amlodipine besylate is the treatment of choice to manage feline hypertension and is effective in the majority of cats, but the dose needed to successfully manage hypertension varies between individuals. Some cats require long-term adjuvant therapy and, occasionally, additional therapy is necessary for emergency management of hypertensive crises. Evidence base: These Guidelines from the International Society of Feline Medicine (ISFM) are based on a comprehensive review of the currently available literature, and are aimed at providing practical recommendations to address the challenges of feline hypertension for veterinarians. There are many areas where more data is required which, in the future, will serve to confirm or modify some of the recommendations in these Guidelines.

Histologic and Immunohistochemical Characterization of Pheochromocytomas in 20 Clouded Leopards ( Neofelis nebulosa)

Clouded leopards in North American zoological institutions have a high frequency of pheochromocytomas and were identified in 32 of 70 (45%) animals necropsied. Archival sections of adrenal gland from 20 adult clouded leopards with unilateral or bilateral pheochromocytomas collected between 1984 and 2011 were examined by light microscopy and immunohistochemistry, and case demographics were reviewed. Affected leopards were older than 10 years of age (mean, 16 years; range, 11-19 years), and males were overrepresented (12 males, 8 females). Pedigree analysis yielded no evidence for heritability. Five clouded leopards had bilateral neoplasms. Pheochromocytoma was the cause of death due to invasion of the caudal vena cava and fatal hemorrhage in 4 cases. Most pheochromocytomas were well-demarcated, nodular, and expansile masses composed of cords and packets of neoplastic polygonal cells. Five pheochromocytomas had vascular invasion, of which 4 resulted in hemorrhage that was the cause of death. One of the latter pheochromocytomas also had pulmonary metastasis. Ultrastructurally, neoplastic cells had cytoplasmic structures consistent with both norepinephrine- and epinephrine-containing granules. In all cases, neoplasms were immunohistochemically positive for chromogranin A, protein gene product 9.5, and synaptophysin. A subset of neoplasms evaluated by tissue microarray were positive for met-enkephalin and β-endorphin and negative for melan-A. Histologically, 7 of 20 (35%) clouded leopards with pheochromocytomas had retinal detachment, retinal degeneration, or intramyocardial muscular arteriosclerosis, suggestive of hypertension. Pheochromocytomas can cause mortality and may be a source of clinically significant hypertension in clouded leopards. These neoplasms share similar histologic, immunohistochemical, and ultrastructural characteristics with those of other species.

Routine kidney variables, glomerular filtration rate and urinary cystatin C in cats with diabetes mellitus, cats with chronic kidney disease and healthy cats

OBJECTIVES

Diabetic kidney disease (DKD) is a frequent and serious complication in human diabetic patients, but data are limited in cats. This study was undertaken to assess whether diabetic cats are susceptible to DKD.

METHODS

Kidney function was compared between 36 cats with diabetes mellitus (DM), 10 cats with chronic kidney disease (CKD) and 10 age-matched healthy cats by measuring routine kidney variables (serum creatinine [sCreat], serum urea [sUrea], urine specific gravity [USG], urinary protein:creatinine ratio [UPC]), urinary cystatin C:creatinine ratio and glomerular filtration rate (GFR). Urinary cystatin C (uCysC) was measured with a human particle-enhanced nephelometric immunoassay, validated to measure feline cystatin C, in all but two diabetic cats. GFR was evaluated by exo-iohexol clearance in 17 diabetic cats, all cats with CKD and all healthy cats.

RESULTS

Diabetic cats had significantly (mean ± SD) lower sCreat (123 ± 38 vs 243 ± 80 µmol/l), sUrea (11 ± 3 vs 18 ± 7 mmol/l) and urinary cystatin C:creatinine ratio (6 ± 31 vs 173 ± 242 mg/mol), and a significantly higher USG (1.033 ± 0.012 vs 1.018 ± 0.006) and GFR (2.0 ± 0.7 vs 0.8 ± 0.3 ml/min/kg) compared with cats with CKD. Compared with healthy cats, diabetic cats only had significantly lower USG (1.033 ± 0.012 vs 1.046 ± 0.008). Proteinuria (UPC >0.4) was present in 39% of diabetic cats, in 30% of cats with CKD and in none of the healthy cats. However, the UPC did not differ statistically between the three groups.

CONCLUSIONS AND RELEVANCE

Based on evaluation of routine kidney variables, GFR and uCysC as a tubular marker at a single time point, a major impact of feline DM on kidney function could not be demonstrated.

Obesity-hypertension and its relation to other diseases in dogs

Obesity is a chronic disease in which adipose tissue accumulates in such a way that it affects the health of the patient and is associated with a myriad of alterations such as systemic hypertension (HTN). The mechanisms by which obesity causes HTN are complex and involve several organic mechanisms. The objective of this study was to determine the correlation between obesity to HTN in dogs in accordance with recent international protocols (systolic blood pressure >160 mmHg) relating to age, genre, gonadal status, breed and other diseases commonly associated with HTN. A total of 244 dogs were studied, 105 non-obese controls and 139 in the obese group. For both groups, healthy and a variety of diseased dogs were observed; the correlations between pathologies and obesity were studied, paying special attention to diseases whose pathophysiologies could lead to HTN. We conclude that obesity is not a risk factor for dogs to develop HTN, and that HTN present in these patients was related to comorbidities such as chronic kidney disease, cardiopathies and endocrinopathies.

Influence of the observer's level of experience on systolic and diastolic arterial blood pressure measurements using Doppler ultrasonography in healthy conscious cats

The objective of this study was to determine the influence of the observer's level of experience on within- and between-day variability, and the percentage of successful systolic (SAP) and diastolic arterial blood pressure (DAP) measurements obtained by Doppler ultrasonography (DU) in awake cats. For this purpose, six healthy conscious cats were used and four observers with different levels of training performed 144 SAP and DAP measurements on 4 days using DU. Measurements were recorded five consecutive times, and mean values were used for statistical analysis. Only the two most skilled observers - a PhD student in cardiology and a Dipl ECVIM-CA (cardiology) - had within- and between-day coefficients of variation (CVs) for SAP ⩽16% (13-16%). Conversely, the two less experienced observers - a fifth-year student and an assistant - had high between-day CVs (61% and 73%). For DAP, only the most experienced observer (Dipl ECVIM-CA) succeeded in 100% of the attempts, with within- and between-day CVs of 11% and 4%, respectively. Conversely, DAP could not be measured by the other three observers in 8%, 19% and 56% of attempts (from the highest to the lowest level of experience); therefore, the corresponding CV values could not be calculated. In conclusion, SAP may be assessed using DU in healthy awake cats with good repeatability and reproducibility by a well-trained observer. Measurement of DAP is more difficult than of SAP, and needs a longer training period, which represents one of the limitations of DU in cats.

Echocardiographic and tissue Doppler imaging alterations associated with spontaneous canine systemic hypertension

BACKGROUND

Feline systemic arterial hypertension (SHT) is associated with a wide spectrum of left ventricular (LV) geometric patterns as well as diastolic, and to a lesser extent, systolic myocardial dysfunction. However, little is known about SHT-related cardiac changes in dogs.

HYPOTHESIS

SHT in dogs is responsible for morphological and functional cardiac alterations.

ANIMALS

Thirty dogs with spontaneous untreated SHT and 28 age- and body weight-matched healthy dogs as controls.

METHODS

Prospective observational study. Conventional echocardiography and 2-dimensional color tissue Doppler imaging were performed in SHT dogs by trained observers and compared with controls.

RESULTS

Forty-seven percent of SHT dogs (14/30) had diffuse concentric hypertrophy. None had left atrial dilatation and 10/30 (33%) had aortic insufficiency (AoI) associated with proximal aortic dilatation. Longitudinal diastolic left ventricular free wall (LVFW) motion was altered in all SHT dogs at the base (early to late diastolic wave ratio, E/A = 0.5 ± 0.1 versus 1.3 ± 0.3 for controls, P < .0001) and the apex (E/A = 1.6 ± 1.7 versus 3.9 ± 3.1, P < .05). Longitudinal motion of the interventricular septum at the base (E/A = 0.7 ± 0.4 versus 1.1 ± 0.1, P < .01) and radial LVFW motion in the subendocardium (E/A = 0.9 ± 0.5 versus 1.6 ± 0.3, P < .01) were also altered in dogs with SHT. Longitudinal LVFW systolic velocities and gradients were also significantly decreased (P < .05) in SHT dogs.

CONCLUSION AND CLINICAL IMPORTANCE

As in SHT in cats, SHT in dogs is associated with myocardial dysfunction independently of the presence of myocardial hypertrophy. However, unlike feline SHT, it results in a homogeneous LV geometric pattern with a relatively high prevalence of AoI.