Diagnosis and treatment of naturally occurring hypoadrenocorticism in 42 dogs

Hypothalamic-pituitary-adrenal axis recovery after intermediate-acting glucocorticoid treatment in client-owned dogs

BACKGROUND

In dogs, duration of hypothalamic-pituitary-adrenal (HPA) axis suppression after systemic glucocorticoid treatment is reported to vary from a few days to up to 7 weeks after glucocorticoid discontinuation. These data are derived mainly from experimental studies in healthy dogs and not from animals with spontaneous disease.

HYPOTHESIS AND OBJECTIVE

To determine the timeline for recovery of the HPA axis in a group of ill dogs treated with intermediate-acting glucocorticoids (IAGCs).

ANIMALS

Twenty client-owned dogs that received IAGC for at least 1 week.

METHODS

Single-center prospective observational study. An ACTH stimulation test, endogenous ACTH concentration, serum biochemistry profile, and urinalysis were performed at T0 (2-6 days after IAGC discontinuation) and then every 2 weeks (eg, T1, T2, T3) until HPA axis recovery was documented (post-ACTH cortisol concentration > 6 μg/dL).

RESULTS

The median time of HPA axis recovery was 3 days (range, 2-133 days). Eleven of 20 dogs showed recovery of the HPA axis at T0, 6/20 at T1, and 1 dog each at T2, T5, and T9. Dose and duration of treatment were not correlated with timing of HPA axis recovery. Activities of ALT and ALP were significantly correlated with the post-ACTH cortisol concentration (rs = -0.34, P = .03; rs = -0.31, P = .05). Endogenous ACTH concentration was significantly correlated with pre (r = 0.72; P < .0001) and post-ACTH cortisol concentrations (r = 0.35; P = .02). The timing of HPA axis recovery of the dogs undergoing an alternate-day tapering dose was not different compared to dogs that did not (3.5 vs 3 days, P = .89).

CONCLUSION AND CLINICAL IMPORTANCE

Most dogs experienced HPA axis recovery within a few days after IAGC discontinuation. However, 2/20 dogs required >8 weeks.

A retrospective study of hydrocortisone continuous rate infusion compared with administration of dexamethasone boluses in dogs with adrenal crisis

BACKGROUND

Evidence indicating the optimal treatment protocol for dogs in adrenal crisis is lacking.

OBJECTIVES

Compare outcomes of dogs presented in adrenal crisis treated with either hydrocortisone (HC) continuous rate infusion (CRI) or intermittent dexamethasone (DEX) administration.

ANIMALS

Thirty-nine client-owned dogs.

METHODS

Multi-institutional retrospective observational study (July 2016-May 2022) including dogs diagnosed with adrenal crisis and with available sequential blood work during hospitalization. Dogs were excluded if already on treatment with exogenous corticosteroids. Outcomes assessed included duration of hospitalization, survival, number of repeat measurements of electrolyte concentrations, and time to normalization of electrolyte and acid-base status.

RESULTS

No significant difference was found between the groups for hospitalization time (P = .41; HC median [range] 48 h [19-105 h]; DEX 57 h [17-167 h]) nor case fatality rate 2/28 in the DEX group and 0/11 in the HC group (P = 1), nor in number of measurements of electrolyte concentrations (P = .90; HC 4 [2-10]; DEX 4.5 [2-15]). No significant differences were found between the 2 treatment groups in time to normalization of serum Na (P = .30; HC 33 h [7-66 h]; DEX 16 h [1.5-48 h]), K (P = .92; HC 17 h [4-48 h]; DEX 16 h [1.25-60 h]) or Na/K ratio (P = .08; HC 17 h [8-48 h]; DEX 26 h [1.5-60 h]).

CONCLUSIONS

This study detected no difference in outcomes for dogs in adrenal crisis treated with either DEX boluses or HC CRIs.

Diagnosis of canine spontaneous hypoadrenocorticism

Hypoadrenocorticism is characterized by a reduction in mineralocorticoid and/or glucocorticoid production by the adrenal glands. Several subtypes have been described with different clinical and clinicopathological consequences. Most affected dogs have vague and non-specific signs that precede an eventual life-threatening crisis. This review aims to appraise classification, the available data on epidemiology and the clinical and laboratory features of naturally occurring canine hypoadrenocorticism.

Canine hypoadrenocorticism is a relatively uncommon endocrine disease that can present with a wide variety of clinical signs resulting from cortisol or aldosterone deficiency or both. Hypoadrenocorticism should be considered in all dogs with severe illness and typical electrolyte abnormalities but also in those with waxing and waning clinical signs. Multiple clinical and laboratory features are suggestive of the disease and should prompt evaluation of adrenal function. The ACTH stimulation test is the best test for diagnosing hypoadrenocorticism but, in those cases without the typical presentation, evaluation of aldosterone secretory capacity and endogenous ACTH concentrations should be performed to distinguish primary from secondary disease. In this review we discuss the pathophysiology of the disease, the clinical signs and laboratory features that should raise suspicion of hypoadrenocorticism and the performance of the different diagnostic tests.

Metabolomic Abnormalities in Serum from Untreated and Treated Dogs with Hyper- and Hypoadrenocorticism

The adrenal glands play a major role in metabolic processes, and both excess and insufficient serum cortisol concentrations can lead to serious metabolic consequences. Hyper- and hypoadrenocorticism represent a diagnostic and therapeutic challenge. Serum samples from dogs with untreated hyperadrenocorticism (n = 27), hyperadrenocorticism undergoing treatment (n = 28), as well as with untreated (n = 35) and treated hypoadrenocorticism (n = 23) were analyzed and compared to apparently healthy dogs (n = 40). A validated targeted proton nuclear magnetic resonance (¹H NMR) platform was used to quantify 123 parameters. Principal component analysis separated the untreated endocrinopathies. The serum samples of dogs with untreated endocrinopathies showed various metabolic abnormalities with often contrasting results particularly in serum concentrations of fatty acids, and high- and low-density lipoproteins and their constituents, which were predominantly increased in hyperadrenocorticism and decreased in hypoadrenocorticism, while amino acid concentrations changed in various directions. Many observed serum metabolic abnormalities tended to normalize with medical treatment, but normalization was incomplete when compared to levels in apparently healthy dogs. Application of machine learning models based on the metabolomics data showed good classification, with misclassifications primarily observed in treated groups. Characterization of metabolic changes enhances our understanding of these endocrinopathies. Further assessment of the recognized incomplete reversal of metabolic alterations during medical treatment may improve disease management.

Urinary cortisol-creatinine ratio in dogs with hypoadrenocorticism

Background

Basal serum cortisol (BSC) ≥2 μg/dL (>55 nmol/L) has high sensitivity but low specificity for hypoadrenocorticism (HA).

Objective

To determine whether the urinary corticoid:creatinine ratio (UCCR) can be used to differentiate dogs with HA from healthy dogs and those with diseases mimicking HA (DMHA).

Animals

Nineteen healthy dogs, 18 dogs with DMHA, and 10 dogs with HA.

Methods

Retrospective study. The UCCR was determined on urine samples from healthy dogs, dogs with DMHA, and dogs with HA. The diagnostic performance of the UCCR was assessed based on receiver operating characteristics (ROC) curves, calculating the area under the ROC curve.

Results

The UCCR was significantly lower in dogs with HA (0.65 × 10⁻⁶; range, 0.33‐1.22 × 10⁻⁶) as compared to healthy dogs (3.38 × 10⁻⁶; range, 1.11‐17.32 × 10⁻⁶) and those with DMHA (10.28 × 10⁻⁶; range, 2.46‐78.65 × 10⁻⁶) (P < .0001). There was no overlap between dogs with HA and dogs with DMHA. In contrast, 1 healthy dog had a UCCR value in the range of dogs with HA. The area under the ROC curve was 0.99. A UCCR cut‐off value of <1.4 yielded 100% sensitivity and 97.3% specificity in diagnosing HA.

Conclusions and Clinical Importance

The UCCR seems to be a valuable and reliable screening test for HA in dogs. The greatest advantage of this test is the need for only a single urine sample.

Evaluation of resting cortisol concentration testing in dogs with chronic gastrointestinal signs

Background

Resting cortisol concentrations are routinely measured in dogs with chronic gastrointestinal signs to rule out hypoadrenocorticism based on a concentration >2 μg/dL (>55 nmol/L).

Hypothesis/Objectives

To assess the cross‐sectional prevalence of hypoadrenocorticism in a group of dogs with chronic gastrointestinal signs presented to a referral internal medicine service.

Animals

Two‐hundred and eighty‐two client‐owned dogs with chronic gastrointestinal signs and with resting cortisol concentration testing performed.

Methods

Retrospective review of medical records (final diagnosis, resting cortisol concentration, and adenocorticotropic hormone [ACTH] stimulation test results) of a referral population of dogs between May 2013 and September 2017.

Results

Resting cortisol concentration was <2 μg/dL (<55 nmol/L) in 79 patients (28%). Repeated resting cortisol concentration measurements were performed in 28 dogs, and in 8, resting cortisol concentrations remained <2 μg/dL (<55 nmol/L). Post‐ACTH cortisol concentration was <2 μg/dL (<55 nmol/L) in 1 dog, consistent with a diagnosis of hypoadrenocorticism and giving a prevalence estimate of hypoadrenocorticism in this population of dogs of 0.3% (95% confidence interval [95CI], 0.03‐1.5%). In 19 dogs with an initial resting cortisol concentration <2 μg/dL (<55 nmol/L), hypoadrenocorticism was excluded based on a repeat resting cortisol concentration >2 μg/dL (>55 nmol/L). Overall, the most common diagnosis was chronic primary inflammatory enteropathy (176/282, 62.4%), followed by extragastrointestinal neoplasia (17/282, 6%), protein‐losing enteropathy, pancreatitis and megaesophagus (10/282, 3.5% each).

Conclusions and Clinical Importance

Although dogs with hypoadrenocorticism can present with chronic gastrointestinal signs, it was the final diagnosis in only 1 of 282 dogs presenting to a referral internal medicine service for signs of chronic enteropathy. Repeated resting cortisol concentration may be considered as a test to try and exclude hypoadrenocorticism.

Comparison of Hydrocortisone Continuous Rate Infusion and Prednisolone or Dexamethasone Administration for Treatment of Acute Hypoadrenocortical (Addisonian) Crisis in Dogs

Objectives

To determine whether administration of intravenous hydrocortisone is a safe and effective alternative treatment in comparison to the traditional treatment with prednisolone/dexamethasone in dogs presenting with Addisonian crisis; and to assess if there is any advantage of the former over the latter in normalisation of electrolyte imbalances and in hospitalisation length in these dogs.

Methods

Medical records of client-owned dogs with hypoadrenocorticism were retrospectively reviewed. Time until normalisation of sodium and potassium concentration, intravenous fluid needs over the first 24 h and hospitalisation length were compared between hydrocortisone and prednisolone/dexamethasone treated dogs.

Results

Twenty-five dogs met the inclusion criteria; 13 received hydrocortisone and 12 prednisolone/dexamethasone. Intravenous hydrocortisone was well-tolerated but failed to prove superiority in terms of time to normalisation of sodium and potassium concentration. Interestingly, potassium normalised in all dogs prior to discharge, but sodium did not in 1/11 hydrocortisone and 5/9 prednisolone/dexamethasone treated dogs with initial hyponatraemia (p = 0.05). Hydrocortisone treated dogs, however, had more electrolyte re-checks [hydrocortisone treated dogs, median (range): 4 (2–16); prednisolone/dexamethasone treated dogs: 2 (0–6); p = 0.001]. There was no difference in intravenous fluid needs over the first 24 h but hydrocortisone treated dogs had longer hospitalisation [hydrocortisone: 81 (45–309) h; prednisolone/dexamethasone: 52 (22–138) h; p = 0.01].

Clinical Significance

Intravenous hydrocortisone is well-tolerated and safe, but no clear additional benefit over traditional glucocorticoid replacement could be identified. Also, it might result in longer hospitalisation time and more intensive monitoring.

Hypoadrenocorticism in dogs under UK primary veterinary care: frequency, clinical approaches and risk factors

Objectives

To estimate the frequency, clinical approaches and risk factors of hypoadrenocorticism in dogs under UK primary veterinary care.

Materials and Methods

Dogs diagnosed with hypoadrenocorticism were identified from the UK VetCompass™ programme by searching anonymised electronic patient records. Pre‐existing and newly diagnosed cases of disease during 2016 were included. Cases were further sub‐categorised as having a laboratory‐confirmed or presumed diagnosis of hypoadrenocorticism based on the information recorded in the electronic patient records. Descriptive data were manually extracted. Multivariable logistic regression methods were used to identify demographic risk factors.

Results

There were 177 hypoadrenocorticism cases identified from 905,543 dogs in 2016; 72 laboratory‐confirmed and 105 presumed. The 1‐year period prevalence for hypoadrenocorticism in all dogs was 0.06% (95% confidence interval: 0.05‐0.07%). The most common presenting clinical signs in laboratory‐confirmed dogs were lethargy (51/66, 77.3%), anorexia (48/66, 66.7%) and vomiting (48/66, 66.7%). Hyperkalaemia was reported in 47 of 53 (88.7%), hyponatraemia in 46 of 53 (86.8%). Median sodium: potassium ratio was 19.00 (interquartile range: 16.20‐20.60). Breed, age, neuter status and insurance status were associated with a laboratory‐confirmed diagnosis of hypoadrenocorticism. No sex association with hypoadrenocorticism was observed in the multivariable model. The standard poodle had 51.38 times the odds (95% CI: 14.49‐182.18) of hypoadrenocorticism compared with crossbreeds. The labradoodle and West Highland white terrier also had increased odds.

Clinical Significance

This is the first epidemiological study to report on hypoadrenocorticism in dogs within the UK primary‐care population. These results provide benchmark data of current veterinary activity relating to hypoadrenocorticism in primary‐care practices.

Semiquantitative acid-base analysis in dogs with typical hypoadrenocorticism

OBJECTIVE

To describe the semiquantitative acid-base status of dogs with untreated naturally occurring typical hypoadrenocorticism and to compare this to the status determined by traditional acid-base analysis.

DESIGN

Retrospective study.

SETTING

University teaching hospital.

ANIMALS

Thirty-three dogs with newly diagnosed typical hypoadrenocorticism between 2000 and 2017.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Dogs were included if they had newly diagnosed hypoadrenocorticism, post-ACTH stimulation serum cortisol concentration <2 μg/dL, and blood collected within 6 hours of presentation for acid-base, electrolyte, and serum biochemical assays. Dogs were excluded if the Na⁺ :K⁺ ratio was ≥28 or the dog had received a mineralocorticoid-containing corticosteroid medication within the preceding month. Traditional acid-base analysis identified normal acid-base status in 1 dog, simple respiratory acid-base abnormalities in 2 of 33 dogs, and simple metabolic acidosis in 14 of 33 dogs. A mixed disorder was most common, noted in 16 of 33 dogs. The semiquantitative approach identified metabolic abnormalities in all cases. All dogs had ≥1 acidifying process, and 29 of 33 had both acidifying and alkalinizing processes. Acidosis attributable to excess free water was present in all dogs, and an acidifying phosphate effect was present in 27 of 33. Hyperlactatemia contributed to the acidosis in 8 of 33 dogs, with a median (range) lactate concentration of 1.5 mmol/L (13.5 mg/dL) (0.3-4.2 mmol/L [2.7-37.8 mg/dL]).

CONCLUSIONS

Dogs with untreated Addison's disease have complex acid-base derangements. The semiquantitative approach to acid-base analysis provides greater insight into the underlying mechanisms of metabolic acid-base abnormalities in these dogs, particularly because lactic acidosis appears to be a minor influence in most cases.

Randomised clinical non-inferiority trial comparing two formulations of desoxycortone pivalate for the treatment of canine primary hypoadrenocorticism

BACKGROUND

This clinical trial compared two formulations of desoxycortone pivalate (DOCP) for treating the mineralocorticoid deficit in dogs with primary hypoadrenocorticism (PH).

METHODS

At veterinary clinics in the USA and France, dogs with PH (n=152) were randomised (3:1) to receive approximately monthly treatments with either the test product, Zycortal (Dechra), administered subcutaneously (n=113), or the control product, Percorten-V (Novartis Animal Health), administered intramuscularly (n=39), both at an initial dose of 2.2 mg/kg DOCP. Treatment administrators were unblinded; veterinarians assessing clinical signs were blinded; owners were blinded until at least day 90, the primary end point. Veterinarians assessed treatment outcome based on all of the following: clinical signs; sodium concentrations; potassium concentrations. Dogs received concurrent glucocorticoid therapy throughout the trial. Non-inferiority was assessed using a generalised linear mixed model to compare success rates between groups.

RESULTS

Success rates at day 90 were similar between groups (per-protocol population at day 90: Zycortal 87/101, 86.2 per cent, Percorten-V 29/34, 85.1 per cent). Zycortal was non-inferior to Percorten-V as the upper limit of the 95 per cent CI for the difference between groups was 13.6 per cent. Polydipsia and polyuria were the most common clinical observations.

CONCLUSION

Both products, in combination with glucocorticoid therapy, were safe and effective in treating PH.

Analytic performance evaluation of a veterinary-specific ELISA for measurement of serum cortisol concentrations of dogs

OBJECTIVE To investigate the precision of an ELISA for measurement of serum cortisol concentration (SCC) in dogs, assess agreement between this ELISA and 2 validated chemiluminescence assays (CLAs), and evaluate the clinical implications of any bias associated with this ELISA when measuring SCC in dogs. DESIGN Evaluation study. SAMPLE 75 stored, frozen serum samples from client-owned dogs. PROCEDURES Enzyme-linked immunosorbent assay precision was evaluated by measuring SCC of pooled serum samples. Agreement with standard methods was evaluated with Spearman rank correlation, Passing-Bablok regression, and Bland-Altman analysis to compare SCCs obtained with the ELISA and the 2 CLAs. An error grid was used to evaluate identified bias. RESULTS Within-laboratory coefficients of variation for pooled serum samples with low, medium, and high SCCs were 21.4%, 28.9%, and 13.0%, respectively. There was a high correlation between ELISA results (for all samples combined) and results of the 2 CLAs (CLA 1, r = 0.96; CLA 2, r = 0.97), but constant and proportional biases between the ELISA and CLAs were present at all concentrations. Clinically important disagreement between ELISA results and CLA results occurred in 16 of 63 (25%) samples, particularly with low and high SCCs. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that the rate of clinical disagreement between the ELISA and CLAs was sufficiently high to recommend that equivocal results obtained with the ELISA be confirmed by a reference laboratory. Further evaluation of analytic performance of the ELISA should focus on samples with very high and very low SCCs.

Pathophysiology and aetiology of hypoglycaemic crises

Hypoglycaemia is a common, life-threatening complication that occurs as a component of a wide variety of disease processes. Despite its frequent occurrence, information concerning the aetiology, characteristics and outcomes of hypoglycaemic crises in veterinary medicine is limited. This review summarises the current understanding of the pathophysiology of hypoglycaemia, the body's counter-regulatory response, underlying aetiologies, diagnosis and treatment. Disease mechanisms are discussed and published evidence in veterinary literature regarding prognostic indicators, prevalence, diagnosis and treatment is examined for hypoglycaemia-related disease processes including insulinoma, glucose-lowering toxins and medications.

Management of hypoadrenocorticism (Addison's disease) in dogs

Hypoadrenocorticism (HOAC; Addison’s disease) is an endocrine condition seen in small animal practice. Dogs with this disease can present in a variety of ways from acute hypovolemic collapse to vague, chronic, waxing, and waning clinical signs. In the most common form of this disease, animals have both mineralocorticoid and glucocorticoid deficiency, resulting in hyponatremia and hyperkalemia, and signs of cortisol deficiency. The etiology may be immune-mediated destruction of the adrenal cortex, drug-induced adrenocortical necrosis (mitotane), enzyme inhibition (trilostane), or infiltrative processes such as neoplastic or fungal disease. Much less commonly, dogs have signs of cortisol deficiency, but no electrolyte changes. This is referred to as atypical HOAC. The veterinarian needs to have a clinical suspicion for HOAC to make a diagnosis in a timely manner. Treatment of dogs with an acute presentation prioritizes correcting the hypovolemia, hyperkalemia, acidosis, and hypoglycemia. Fluid therapy addresses most of these issues, but other directed therapies may be required in the most severe cases. For chronic management, all patients with Addison’s disease will require replacement of glucocorticoids (usually prednisone), and most patients require replacement of mineralocorticoids with either desoxycorticosterone pivalate or fludrocortisone. Atypical Addisonians do not require mineralocorticoid supplementation, but electrolytes should be monitored in case the need arises in the future. The prognosis for dogs treated for HOAC promptly and appropriately is excellent; most patients die from other diseases. However, if the diagnosis is missed, patients may die as a consequence of HOAC. Thus, knowledge of the hallmarks of Addison’s disease is imperative.

Urine sodium concentrations are predictive of hypoadrenocorticism in hyponatraemic dogs: a retrospective pilot study

OBJECTIVES

To determine if a urine sodium concentration could be used to rule out hypoadrenocorticism in hyponatraemic dogs.

MATERIALS AND METHODS

Medical records were reviewed for hyponatraemic dogs (serum sodium<135 mmol/L) that had recorded urine sodium concentrations. Twenty hyponatraemic dogs were included: 11 diagnosed with classical hypoadrenocorticism and nine with non-adrenal causes of hyponatraemia. A Wilcoxon rank-sum test was used to compare results between groups.

RESULTS

No dog with hypoadrenocorticism had a urine sodium concentration less than 30 mmol/L. Urine sodium concentration in dogs with hypoadrenocorticism was significantly higher (median 103 mmol/L, range: 41 to 225) than in dogs with non-adrenal illness (median 10 mmol/L, range: 2 to 86) (P<0·0005). Serum sodium concentrations were not significantly different between dogs with hypoadrenocorticism and dogs with non-adrenal illness.

CLINICAL SIGNIFICANCE

These results suggest that urine sodium concentrations can be used to prioritise a differential diagnosis of hypoadrenocorticism in hyponatraemic dogs. A urine sodium concentration less than 30 mmol/L in a hyponatraemic dog makes classical hypoadrenocorticism an unlikely cause of the hyponatraemia. Nevertheless, because of the small sample size our results should be interpreted with caution and a larger follow-up study would be valuable.

Altered Serum Thyrotropin Concentrations in Dogs with Primary Hypoadrenocorticism before and during Treatment

Background

Thyrotropin (TSH) can be increased in humans with primary hypoadrenocorticism (HA) before glucocorticoid treatment. Increase in TSH is a typical finding of primary hypothyroidism and both diseases can occur concurrently (Schmidt's syndrome); therefore, care must be taken in assessing thyroid function in untreated human patients with HA.

Objective

Evaluate whether alterations in cTSH can be observed in dogs with HA in absence of primary hypothyroidism.

Animals

Thirty dogs with newly diagnosed HA, and 30 dogs in which HA was suspected but excluded based on a normal ACTH stimulation test (controls) were prospectively enrolled.

Methods

cTSH and T4 concentrations were determined in all dogs and at selected time points during treatment (prednisolone, fludrocortisone, or DOCP) in dogs with HA.

Results

cTSH concentrations ranged from 0.01 to 2.6 ng/mL (median 0.29) and were increased in 11/30 dogs with HA; values in controls were all within the reference interval (range: 0.01–0.2 ng/dL; median 0.06). There was no difference in T4 between dogs with increased cTSH (T4 range 1.0‐2.1; median 1.3 μg/dL) compared to those with normal cTSH (T4 range 0.5‐3.4, median 1.4 μg/dL; P=0.69) and controls (T4 range 0.3‐3.8, median 1.8 μg/dL; P=0.35). After starting treatment, cTSH normalized after 2–4 weeks in 9 dogs and after 3 and 4 months in 2 without thyroxine supplementation.

Conclusions and Clinical Relevance

Evaluation of thyroid function in untreated dogs with HA can lead to misdiagnosis of hypothyroidism; treatment with glucocorticoids for up to 4 months can be necessary to normalize cTSH.

Canine pancytopoenia in a Mediterranean region: a retrospective study of 119 cases (2005 to 2013)

OBJECTIVES

To further clarify the causes of pancytopoenia and to investigate whether underlying cause or severity were associated with survival in an area endemic for vector-borne pathogens.

METHODS

Retrospective review of medical records of 119 dogs with and 238 dogs without pancytopoenia.

RESULTS

Mixed-breed dogs and dogs younger than one year had higher odds of being pancytopoenic. The most common diagnoses included monocytic ehrlichiosis (n=42), leishmaniasis (n=28) and parvoviral enteritis (n=19). The mean white blood cell counts were lower in dogs with ehrlichiosis and parvoviral enteritis compared to dogs with leishmaniasis, while platelet counts were lower in ehrlichiosis compared to leishmaniasis or parvoviral enteritis. Total protein concentrations were lower in dogs with parvoviral enteritis compared to ehrlichiosis and leishmaniasis. Higher haematocrit, platelet and white cell counts were associated with better odds of survival.

CLINICAL SIGNIFICANCE

Infectious diseases appear to be the leading causes of canine pancytopoenia in endemic areas; severe leukopoenia (ehrlichiosis, parvoviral enteritis), thrombocytopoenia (ehrlichiosis) and hypoproteinaemia (parvoviral enteritis), represented potentially useful disease-specific diagnostic determinants. The severity of pancytopoenia significantly affects the clinical outcome.

Factors that affect stabilisation times of canine spontaneous hypoadrenocorticism

The objective of this retrospective study was to examine factors that may have affected the stabilisation times of 50 dogs with spontaneous hypoadrenocorticism that were being treated with fludrocortisone acetate, with particular emphasis on dosing frequency and the concurrent use of prednisolone. Stabilisation was defined as an absence of clinical signs with a sodium:potassium ratio >27:1 and both electrolyte concentrations within a laboratory reference range. It was found that the median time till stabilisation was three months. The frequency of fludrocortisone treatment (once, twice or changed from once to twice a day) had no effect on the stabilisation time. The two groups of dogs that were started and stabilised on once a day or twice a day dosing had a median stabilisation time of two months. However, dogs that failed to stabilise on once a day dosing of fludrocortisone and were then changed onto twice a day dosing then stabilised a median of one month later. Concurrent use of prednisolone resulted in significantly faster stabilisation times. It was concluded that dogs with hypoadrenocorticism should be continued on prednisolone therapy until they are stabilised. If a dog is failing to stabilise on once a day fludrocortisone acetate, a change to twice a day administration could be considered.

Hydrocortisone in the management of acute hypoadrenocorticism in dogs: a retrospective series of 30 cases

OBJECTIVES

The objectives of this study were to describe the efficacy, outcome and adverse effects of intravenous hydrocortisone and fluid therapy for the management of acute hypoadrenocorticism in dogs.

METHODS

A retrospective review of dogs with primary hypoadrenocorticism receiving intravenous hydrocortisone and fluid therapy was performed.

RESULTS

Thirty newly-diagnosed dogs were included. There was an excellent clinical response, with all dogs surviving to discharge within a median of 2 days. In 23 cases with complete data, the mean rate of change of sodium over 24 hours was 0·48 (±0·28) mmol/L/hour, while the mean rate of change of potassium was -0·12 (±0·06) mmol/L/hour. Circulating potassium concentration normalised in 68·4% and 100% of cases of by 12 and 24 hours, respectively. Additional treatment for hyperkalaemia was not found necessary. Plasma sodium concentration increased by >12 mmol/L/24 hours on 7 of 23 (30·4%) occasions. One dog exhibited associated temporary neurological signs.

CLINICAL SIGNIFICANCE

Intravenous hydrocortisone infusion and fluid therapy for the management of acute hypoadrenocorticism is associated with a rapid resolution of hyperkalaemia and is well tolerated with few adverse effects. Regular electrolyte monitoring is required to ensure that rapid increases in sodium concentration are avoided.

Evaluation of the Cortisol-to-ACTH Ratio in Dogs with Hypoadrenocorticism, Dogs with Diseases Mimicking Hypoadrenocorticism and in Healthy Dogs

Background

The adrenocorticotropic hormone (ACTH) stimulation test is the gold standard for diagnosing hypoadrenocorticism (HA) in dogs. However, problems with the availability of synthetic ACTH (tetracosactrin/cosyntropin) and increased costs have prompted the need for alternative methods.

Objectives

To prospectively evaluate the cortisol‐to‐ACTH ratio (CAR) as a screening test for diagnosing canine HA.

Animals

Twenty three dogs with newly diagnosed HA; 79 dogs with diseases mimicking HA; 30 healthy dogs.

Methods

Plasma ACTH and baseline cortisol concentrations were measured before IV administration of 5 μg/kg ACTH in all dogs. CAR was calculated and the diagnostic performance of ACTH, baseline cortisol, CAR and sodium‐to‐potassium ratios (SPRs) was assessed based on receiver operating characteristics (ROC) curves calculating the area under the ROC curve.

Results

The CAR was significantly lower in dogs with HA compared to that in healthy dogs and in those with diseases mimicking HA (P < .0001). There was an overlap between HA dogs and those with HA mimicking diseases, but CAR still was the best parameter for diagnosing HA (ROC AUC 0.998), followed by the ACTH concentration (ROC AUC 0.97), baseline cortisol concentration (ROC AUC 0.96), and SPR (ROC AUC 0.86). With a CAR of >0.01 the diagnostic sensitivity and specificity were 100% and 99%, respectively.

Conclusion and Clinical Importance

Calculation of the CAR is a useful screening test for diagnosing primary HA. As a consequence of the observed overlap between the groups, however, misdiagnosis cannot be completely excluded. Moreover, additional studies are needed to evaluate the diagnostic reliability of CAR in more dogs with secondary HA.

Use of plasma renin activity to monitor mineralocorticoid treatment in dogs with primary hypoadrenocorticism: desoxycorticosterone versus fludrocortisone

Background

Measurement of plasma renin activity (PRA) is the gold standard for monitoring mineralocorticoid treatment in humans with primary hypoadrenocorticism (PH).

Objectives

To compare PRA in dogs with newly diagnosed PH, dogs with diseases mimicking PH, and healthy dogs, and evaluate measurement of PRA to monitor therapeutic effects in dogs with PH treated with different mineralocorticoids.

Animals

Eleven dogs with newly diagnosed PH (group 1), 10 dogs with diseases mimicking PH (group 2), 21 healthy dogs (group 3), 17 dogs with treated PH (group 4).

Methods

In group 1, PRA was measured before treatment and at different times after initiating treatment. In groups 2 and 3, PRA was measured at initial presentation only. In group 4, no baseline PRA was obtained but PRA was measured once or every 1–6 months during treatment. Mineralocorticoid treatment consisted of fludrocortisone acetate (FC) or desoxycorticosterone pivalate (DOCP).

Results

Plasma renin activity before treatment was increased in dogs with PH compared to normal dogs and dogs with diseases mimicking PH with median activity of 27, 0.8, and 1.0 ng/mL/h, respectively. In dogs with PH, PRA decreased and normalized with mineralocorticoid treatment using DOCP but not with FC. In dogs treated with DOCP, PRA was lower than in dogs treated with FC. Plasma sodium concentrations were higher and potassium concentrations were lower with DOCP treatment compared to FC treatment.

Conclusion and Clinical Importance

Plasma renin activity is a reliable tool for monitoring mineralocorticoid treatment. DOCP treatment more effectively suppresses PRA compared to FC in dogs with PH.

Diagnosis and treatment of chronic lymphocytic leukemia in a bat-eared fox (Otocyon megalotis)

CASE DESCRIPTION

Severe lymphocytosis and leukocytosis were detected during examination of a 10-year-old sexually intact male bat-eared fox (Otocyon megalotis) with regionally extensive alopecia.

CLINICAL FINDINGS

A CBC revealed severe leukocytosis (39,100 leukocytes/μL) and marked lymphocytosis (90%). A blood smear consisted predominantly of intermediate-sized lymphocytes and few large lymphocytes, with mild to moderate nuclear atypia. These findings were highly suggestive of chronic lymphocytic leukemia (CLL). Cytologic evaluation of bone marrow aspirates revealed no evidence of overt malignancy, with 10% of all cells identified as small to intermediate-sized mature lymphocytes.

TREATMENT AND OUTCOME

Treatment with chlorambucil and prednisone administered orally over a 1.8-year period decreased the leukocyte and lymphocyte counts to within reference intervals with no adverse effects. Although repeated flow cytometry revealed evidence of residual disease, the fox remained free of clinical disease, and WBC counts were within reference intervals for this species. At 22 months after initial evaluation, the fox was euthanized because of debilitating arthritis. No evidence of CLL was detected grossly or histologically during necropsy.

CLINICAL RELEVANCE

To the authors' knowledge, this was the first report of CLL in a bat-eared fox and first successful treatment in a nondomestic carnivore. Treatment in accordance with a chemotherapeutic protocol successfully resolved the leukocytosis and lymphocytosis with no serious adverse effects. Description of this fox and the treatment protocol should provide a valuable reference for future cases in this and other nondomestic canine species.

A candidate gene analysis of canine hypoadrenocorticism in 3 dog breeds

Canine hypoadrenocorticism is believed to be an immune-related condition. It is rare in the overall dog population but shows a breed-related predisposition with Standard poodles and Portuguese water dogs having a greater prevalence of the condition. It shares many similarities with human primary adrenal insufficiency and is believed to be a naturally occurring, spontaneous model for the human condition. Short haplotype blocks and low levels of linkage disequilibrium in the human genome mean that the identification of genetic contributors to the condition requires large sample numbers. Pedigree dogs have high linkage disequilibrium and long haplotypes within a breed, increasing the potential of identifying novel genes that contribute to canine genetic disease. We investigated 222 SNPs from 42 genes that have been associated or may be implicated in human Addison's disease. We conducted case-control analyses in 3 pedigree dog breeds (Labrador retriever: affected n = 30, unaffected = 76; Cocker Spaniel: affected n = 19, unaffected = 53; Springer spaniel: affected n = 26, unaffected = 46) and identified 8 associated alleles in genes COL4A4, OSBPL9, CTLA4, PTPN22, and STXBP5 in 3 pedigree breeds. Association with immune response genes PTPN22 and CTLA4 in certain breeds suggests an underlying immunopathogenesis of the disease. These results suggest that canine hypoadrenocorticism could be a useful model for studying comparative genetics relevant to human Addison's disease.

Lower initial dose desoxycorticosterone pivalate for treatment of canine primary hypoadrenocorticism

OBJECTIVE

To evaluate the efficacy of initial doses of desoxycorticosterone pivalate (DOCP) that are lower and less expensive than the presently recommended initial dose of 2.2 mg/kg for treating dogs with primary hypoadrenocorticism.

METHODS

A retrospective study was performed on 49 dogs with primary hypoadrenocorticism, including 36 with initial DOCP doses less than 2.2 mg/kg. Medical records were reviewed for clinical data. All study dogs were followed up with telephone calls to owners or veterinarians to determine the date of death or last follow-up. Data were analysed to investigate relationships between initial DOCP dose and survival and serum Na, K and their ratio.

RESULTS

Regardless of their initial DOCP dose, none of the dogs developed uncontrolled hypoadrenocorticism or severe electrolyte abnormalities or clinical problems that would have made an increase in the DOCP dose necessary. Over time, most dogs had a decrease in their DOCP dose in mg/kg, because of weight gain during treatment. No statistically significant relationships were found between initial DOCP dose and survival or post-treatment serum Na, K or Na : K, with the exception of one statistically significant result that suggested lower efficacy for higher doses.

CONCLUSION

Initial DOCP doses less than 2.2 mg/kg may be effective in controlling serum electrolyte concentrations in dogs with primary hypoadrenocorticism without adversely affecting survival. If confirmed by additional research, these findings would enable practitioners to reduce the cost of DOCP treatment by using lower initial doses, potentially saving the lives of dogs that would otherwise be euthanased because of treatment expense.

Severe hypoglycaemia in a cat with primary hypoadrenocorticism

This case report describes a 3-year-old, castrated male, mixed-breed cat with historical, clinical and laboratory findings compatible with primary hypoadrenocorticism, confirmed by adrenocorticotropic hormone stimulation test. Severe but asymptomatic hypoglycaemia was an unexpected biochemical finding and resolved after fludrocortisone acetate and prednisolone treatment. This case demonstrates that hypoadrenocorticism should be included in the differentials list of severe hypoglycaemia in cats.

White blood cell count and the sodium to potassium ratio to screen for hypoadrenocorticism in dogs

BACKGROUND

Abnormal sodium to potassium (Na:K) ratios can raise suspicion for hypoadrenocorticism (HA). Although dogs with HA usually have normal leukograms, their white blood cell counts may be useful in screening for HA.

OBJECTIVES

To examine the utility of combining the Na:K ratio with white blood cell counts to screen for HA in hospitalized dogs requiring fluid treatment administered i.v..

ANIMALS

Fifty-three dogs with confirmed HA and 110 sick dogs confirmed not to have HA.

METHODS

Retrospective, case-control study. Dogs were included if they were hospitalized and administered fluids i.v., had a complete blood count and measurement of serum Na and K concentrations. HA was diagnosed using an ACTH stimulation test, or ruled out by measurement of basal serum cortisol concentration.

RESULTS

The receiver operating characteristic (ROC) curve for the lymphocyte count was not significantly different from the ROC curve of the Na:K ratio (P = .55). The ROC curve for the model combining the Na:K ratio and lymphocyte count was superior for identifying dogs with HA compared to the Na:K ratio (P = .02) or lymphocyte count (P = .005) alone. At the 100% sensitivity cutoff, lymphocyte count was more specific for detection of HA than Na:K (P < .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

A combination of the Na:K ratio and lymphocyte count provides a better screening test for HA compared to the Na:K ratio or lymphocyte count alone. At 100% sensitivity, the lymphocyte count is a more specific test for HA than the Na:K.

Emesis in dogs: a review

Emesis is a common presenting sign in small animal practice. It requires a rational approach to management that is based upon a sound understanding of pathophysiology combined with logical decision making. This review, which assesses the weight of available evidence, outlines the physiology of the vomiting reflex, causes of emesis, the consequences of emesis and the approach to clinical management of the vomiting dog. The applicability of diagnostic testing modalities and the merit of traditional approaches to management, such as dietary changes, are discussed. The role and usefulness of both traditional and novel anti-emetic drugs is examined, including in specific circumstances such as following cytotoxic drug treatment. The review also examines areas in which common clinical practice is not necessarily supported by objective evidence and, as such, highlights questions worthy of further clinical research.

Use of basal serum or plasma cortisol concentrations to rule out a diagnosis of hypoadrenocorticism in dogs: 123 cases (2000-2005)

OBJECTIVE

To determine whether basal serum or plasma cortisol concentration can be used as a screening test to rule out hypoadrenocorticism in dogs.

DESIGN

Retrospective case-control study.

ANIMALS

110 dogs with nonadrenal gland illnesses and 13 dogs with hypoadrenocorticism.

PROCEDURES

Sensitivity and specificity of basal serum or plasma cortisol concentrations of either <or= 1 microg/dL or <or= 2 microg/dL to detect dogs with hypoadrenocorticism were estimated by use of the ACTH stimulation test as the gold standard.

RESULTS

Basal cortisol concentrations of <or= 1 microg/dL had excellent sensitivity (100%) and specificity (98.2%) for detecting dogs with hypoadrenocorticism. For basal cortisol concentrations of <or= 2 microg/dL, sensitivity was 100% but specificity was 78.2%.

CONCLUSIONS AND CLINICAL RELEVANCE

On the basis of sensitivity and specificity, basal serum or plasma cortisol concentrations had high negative predictive values over a wide range of prevalence rates and can be used to rule out a diagnosis of hypoadrenocorticism. Dogs with basal cortisol concentrations > 2 microg/dL that are not receiving corticosteroids, mitotane, or ketoconazole are highly unlikely to have hypoadrenocorticism. However, if the basal cortisol concentration is <or= 2 microg/dL, little to no information regarding adrenal gland function can be obtained and an ACTH stimulation test should be performed.

Determining the Significance of Persistent Lymphocytosis

The authors provide a review of current knowledge of lymphocytosis in nonneoplastic conditions. They conclude that the list of major differentials for persistent nonneoplastic lymphocyte expansion in dogs and cats is short and that most of these conditions are relatively uncommon. Persistent lymphocytosis of small, mature, or reactive lymphocytes is most commonly the result of chronic lymphocytic leukemia or lymphoma. The first step in distinguishing nonneoplastic from neoplastic lymphocytosis is immunophenotyping by flow cytometry to determine the phenotypic diversity of the circulating cells. Clonality testing using the polymerase chain reaction for antigen receptor rearrangements assay is a useful second step in cases in which the phenotype data are equivocal. Once the diagnosis of malignancy has been established, the immunophenotype also provides prognostic information in dogs.

Hypocortisolaemia in a Labrador retriever

A four-year-old Labrador retriever was presented with lethargy and exercise intolerance. Clinical examination was unremarkable. A subnormal cortisol response to adrenocorticotrophin hormone (ACTH) was demonstrated (plasma cortisol concentrations before and after administration of ACTH were both below the detection limit of the assay) but plasma aldosterone concentrations were within the normal range. Endogenous plasma ACTH concentrations were high, indicating primary adrenocortical disease. Following glucocorticoid supplementation at a replacement dose (prednisolone 0.1 mg/kg) the dog made a full clinical recovery.

Treatment and long-term follow-up of 205 dogs with hypoadrenocorticism

Results of long-term treatment were evaluated in 200 dogs with primary hypoadrenocorticism and 5 dogs with spontaneous secondary hypoadrenocorticism. Fludrocortisone acetate initially was used for mineralocorticoid replacement in 190 of the dogs with primary hypoadrenocorticism. The daily dose of fludrocortisone required in these dogs increased significantly during the treatment period (median, 2.6 years) from an initial median dose of 13.1 micrograms/kg to a final dose of 22.6 micrograms/kg. In 27 of the 200 dogs, mineralocorticoid therapy was changed from fludrocortisone to desoxycorticosterone pivalate (DOCP) because of adverse effects,poor response, or financial considerations. The dose of DOCP required in the 33 dogs (27 dogs plus 6 dogs initially given DOCP) increased significantly during the treatment period (median, 3.5 years) from an initial median dose of 1.56 mg/kg to a final dose of 1.69 mg/kg; the interval between DOCP injections ranged from 14 to 35 days (median, 30 days). The dose of prednisone administered to the dogs with primary hypoadrenocorticism decreased significantly from an initial median dose of 0.3 mg/kg to a final dose of 0.2 mg/kg; the drug was discontinued in 22 dogs due to adverse effects. The 5 dogs with secondary hypoadrenocorticism received only glucocorticoid replacement therapy (prednisone) at initial and final daily dosages of 0.41 mg/kg and 0.25 mg/kg, respectively, during a median treatment period of 4.4 years. More than 80% of the dogs were considered to have a good to excellent response to therapy. The median survival time of all 205 dogs was 4.7 years. There were no differences in response to treatment or survival between dogs treated with fludrocortisone and those receiving DOCP, or between dogs with primary hypoadrenocorticism and those with secondary hypoadrenocorticism.

Primary and secondary canine hypoadrenocorticism

Hypoadrenocorticism (primary or secondary) is an uncommon endocrine disorder seen most commonly in young-to-middle-aged female dogs. This article reviews the various clinical manifestations of this disorder, recommended testing protocols for definitive diagnosis, and current therapeutic protocols. The long-term prognosis is good-to-excellent for most dogs receiving appropriate replacement therapy.