Variability among four refractometers for the measurement of urine specific gravity and comparison with urine osmolality in dogs.

BACKGROUND: Refractometry is often used in clinical veterinary medicine to estimate urine concentration. Variability among commonly-used refractometers has not been critically evaluated. OBJECTIVE: This study aimed to evaluate the variability of urine specific gravity (USG) among four refractometers and compare results of USG measurements with those of urine osmolality (Uosm ), the gold standard for determining urine concentrations. METHODS: USG was determined in 100 dogs using three optical refractometers, the American Optical Abbe refractometer 10450, Reichert TS 400 refractometer, and Heska Veterinary refractometer 2737-E02, and one digital refractometer, the Misco Palm Abbe Digital refractometer #PA203. Results were compared between each pair of refractometers and between each refractometer and urine osmolality determined by freezing point depression using a Multi-Osmette 2430E osmometer. Results were analyzed with Bland-Altman plots and Passing-Bablok regression analysis. RESULTS: The Reichert, Heska, and Misco refractometers provide USG measurements that can be used interchangeably based on small differences, consistently less than 0.002, between the USG measurements. The AO refractometer measured USG values with much larger differences, which were deemed clinically significant by the study parameters. None of the refractometers were able to accurately predict Uosm or vice versa within a clinically acceptable range. CONCLUSIONS: Varying degrees of differences were seen in the USG measurements among the different refractometers. These differences were refractometer-dependent, and the results from one instrument could affect clinical decisions.

A Quick Reference on Hypernatremia.

Hypernatremia most commonly is associated with water loss in excess of sodium or salt gain (typically associated with restriction of access to water). Most of the signs of hypernatremia arise from the central nervous system; the more rapid the development of hypernatremia, the more severe the neurologic signs are likely to be. Anorexia, lethargy, vomiting, muscular weakness, behavioral changes, disorientation, ataxia, seizures, coma, and death have been identified in dogs and cats with hypernatremia and hypertonicity.

A Quick Reference on Hyponatremia.

The article focuses on causes of hyponatremia, including hypovolemia, diabetes mellitus and others. Hypovolemia is a major cause of hyponatremia in veterinary medicine. Hypovolemia causes a decrease in effective circulating volume, triggering antidiuretic hormone (ADH) secretion and free water retention, and develops after gastrointestinal losses, renal losses, hemorrhagic shock, hypoadrenocorticism, and other causes of hypovolemia. The article reviews the clinical approach to diagnosing the cause of hyponatremia in critically ill patients, including recognition of the syndrome of inappropriate ADH secretion (SIADH).

Disorders of Sodium and Water Homeostasis.

This review article discusses normal and abnormal sodium balance in small animals. The terms and concepts central to understanding normal sodium and water balance are presented as well as of the physiology of body fluid compartments and the movement of fluid between those compartments. As dysnatremia is a very common disorder across the spectrum of critically ill patients, the main focus of the article is to present several clinical examples of both acute and chronic hypernatremia and hyponatremia and their practical, clinical management.

Case study in planning revisions to a veterinary professional curriculum: opportunity, motive, and means.

The Ohio State University (OSU) recently responded to a mandate from the state to convert from a quarter-based to a semester-based academic calendar. The OSU College of Veterinary Medicine took this opportunity to review and revise the curriculum leading to the DVM degree. This mandate occurred at a time when the college was motivated to act on recommendations that had been made during a recent reaccreditation process, some of which had been under discussion for several years, and had the personnel in place to initiate the change process. This article describes the means by which the curriculum change was planned. A review of the literature on change in health-sciences-related programs suggested that the ability to conclude the planning of changes in a relatively short time period was facilitated by adopting practices shown to promote successful curricular change. Critical aspects of the process included engaging the faculty, establishing a collective vision that entails agreement on principles, having a clear mandate and time frame for change, providing resources and training to support and sustain the change effort, and managing the effort centrally with groups that are broadly representative of the faculty.

Acid-base and hormonal abnormalities in dogs with naturally occurring diabetes mellitus.

OBJECTIVE: To examine acid-base and hormonal abnormalities in dogs with diabetes mellitus. DESIGN: Cross-sectional study. ANIMALS: 48 dogs with diabetes mellitus and 17 healthy dogs. PROCEDURES: Blood was collected and serum ketone, glucose, lactate, electrolytes, insulin, glucagon, cortisol, epinephrine, norepinephrine, nonesterified fatty acid, and triglyceride concentrations were measured. Indicators of acid-base status were calculated and compared between groups. RESULTS: Serum ketone and glucose concentrations were significantly higher in diabetic than in healthy dogs, but there was no difference in venous blood pH or base excess between groups. Anion gap and strong ion difference were significantly higher and strong ion gap and serum bicarbonate concentration were significantly lower in the diabetic dogs. There were significant linear relationships between measures of acid-base status and serum ketone concentration, but not between measures of acid-base status and serum lactate concentration. Serum insulin concentration did not differ significantly between groups, but diabetic dogs had a wider range of values. All diabetic dogs with a serum ketone concentration > 1,000 micromol/L had a serum insulin concentration < 5 microU/mL. There were strong relationships between serum ketone concentration and serum glucagon-insulin ratio, serum cortisol concentration, and plasma norepinephrine concentration. Serum beta-hydroxybutyrate concentration, expressed as a percentage of serum ketone concentration, decreased as serum ketone concentration increased. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that ketosis in diabetic dogs was related to the glucagon-insulin ratio with only low concentrations of insulin required to prevent ketosis. Acidosis in ketotic dogs was attributable largely to high serum ketone concentrations.

Hypernatremia: a quick reference.

This article serves as a quick reference for hypernatremia. Guidelines for analysis and causes, signs, and a stepwise approach are presented.

Hyponatremia: a quick reference.

This article serves as a quick reference for hyponatremia. Guidelines for analysis and causes, signs, and a stepwise approach are presented.

Metabolic acid-base disorders in the critical care unit.

The recognition and management of acid-base disorders is a commonplace activity in the critical care unit, and the role of weak and strong acids in the genesis of metabolic acid-base disorders is reviewed. The clinical approach to patients with metabolic alkalosis and metabolic acidosis is discussed in this article.

Effect of phenylpropanolamine and pseudoephedrine on the urethral pressure profile and continence scores of incontinent female dogs.

BACKGROUND: Traditionally, treatment of urinary incontinence in spayed female dogs has been to increase urethral sphincter tone with estrogen compounds or alpha-agonists. Phenylpropanolamine (PPA) is the most frequently used alpha-agonist for this condition, but increased cost and decreased availability of PPA as an over-the-counter medication have prompted interest in alternative therapies that may provide the same degree of efficacy. Pseudoephedrine (PD), an alpha-agonist and stereoisomer of ephedrine, is more cost-effective and available without a prescription. HYPOTHESIS: PD will not differ from PPA in its effects on urodynamic variables and owner-reported continence scores or in observed adverse effects. ANIMALS: Nine spayed female dogs with a history of urinary incontinence drawn from the clinical patient population at the Veterinary Teaching Hospital at The Ohio State University. METHODS: A randomized, double-blind crossover study evaluating changes in urodynamic variables, owner-reported continence score, and adverse effects in dogs treated with 1.5 mg/kg PO q8h PPA or PD. RESULTS: Changes in maximum urethral closure pressure and functional area after PPA therapy were significantly higher than after PD therapy. There was no change in the functional profile length after either treatment. There was a significant increase in the continence score after PPA therapy, but not after PD therapy. More adverse effects were observed in dogs treated with PD than with PPA. CONCLUSIONS AND CLINICAL IMPORTANCE: Although some dogs clinically improved, lack of statistically significant changes in urodynamic variables and owner perception of continence as well as the increased incidence of adverse effects make PD a less satisfactory alternative to PPA for the treatment of urinary incontinence in female dogs.

Comparison of the effects of daily and intermittent-dose calcitriol on serum parathyroid hormone and ionized calcium concentrations in normal cats and cats with chronic renal failure.

BACKGROUND: Chronic renal failure is complicated by secondary hyperparathyroidism, which traditionally has been controlled by dietary restriction of phosphorus and administration of phosphorus binders. Early treatment of patients with chronic renal failure with calcitriol may be indicated because once established, parathyroid gland hyperplasia does not readily resolve with therapy. HYPOTHESIS: Daily and intermittent dosing of calcitriol will decrease plasma parathyroid hormone concentration in normal cats and cats with chronic renal failure without causing ionized hypercalcemia. ANIMALS: Ten normal cats; 10 cats with chronic renal failure. METHODS: Phase 1 was daily calcitriol administration (2.5 ng/kg PO q24h) for 14 days. Phase 2 was intermittent calcitriol administration (8.75 ng/kg PO q84h) for 14 days. A 7-day washout period separated phases 1 and 2. Before each phase, calcitriol, parathyroid hormone, and ionized calcium concentrations were measured. On days 1, 2, and 3 of both phases, serum ionized calcium concentrations were measured. On the last day of both phases, calcitriol, parathyroid hormone, and ionized calcium concentrations were measured 0, 2, 4, and 6 hours after calcitriol administration. RESULTS: Overall, serum parathyroid hormone concentrations were significantly higher in cats with chronic renal failure than in normal cats (P = .022), but serum parathyroid hormone concentrations for both normal cats and cats with chronic renal failure were not significantly different before and after 14 days of treatment with calcitriol, regardless of whether calcitriol was administered daily or intermittently. Adverse effects of calcitriol administration (specifically ionized hypercalcemia) were not seen in either feline group during either phase of the study over the 3-day evaluation after calcitriol administration was initiated. CONCLUSIONS AND CLINICAL IMPORTANCE: At the dosages used, calcitriol treatment did not result in significant differences in serum parathyroid hormone concentrations before and after treatment in both normal cats and cats with chronic renal failure. With these dosages, adverse affects of calcitriol administration were not seen. Potential reasons for lack of apparent effect include small sample size, insufficient duration of study, insufficient dosage of calcitriol, problems with formulation or administration of calcitriol, and variable gastrointestinal absorption of calcitriol.

Vestibular, vaginal, and urethral relations in spayed dogs with and without lower urinary tract signs.

The purpose of this study was to evaluate the urogenital anatomy in female spayed dogs with and without signs of lower urinary tract disease by using conventional vaginourethrography, computed tomography (CT) vaginourethrography, and uroendoscopy. Nineteen dogs with lower urinary tract disease and 12 normal dogs were evaluated prospectively. Measurements made included vaginal length, vaginal height, vaginal width, vestibule length, vestibule height, vestibule width, vestibulovaginal ratios, cingulum height, cingulum width, cingulum area, urethral length, urethral height, urethral width, angle of urethra to vestibule, and angle of vaginal to vestibule. Group comparisons were made between dogs with and without lower urinary tract disease. Comparisons between conventional vaginourethrography and CT vaginourethrography were made when the same anatomical measurement was made by the 2 imaging modalities. There was no significant difference in all of the measurements (P > .01), including vestibulovaginal ratios and cingulum areas, between dogs with and without lower urinary tract disease. There was a larger proportion of dogs with a vestibulovaginal ratio <0.33 in normal dogs (8 of 12) compared with the clinical dogs (8 of 16). A significant difference between vestibulovaginal ratios or cingulum areas between dogs with and without lower urinary tract disease could not be identified. This suggests that a vestibulovaginal ratio of <0.33 may only be an incidental finding and the term "vestibulovaginal stenosis" may need to be redefined.

Vestibular, vaginal and urethral relationships in spayed and intact normal dogs.

The purpose of this study was to evaluate the urogenital anatomy in sound spayed and intact dogs. Fourteen intact and 12 spayed sound dogs had their lower urogenital tract evaluated with conventional vaginourethrography, computed tomography (CT) vaginourethrography and uroendoscopy under general anesthesia. Measurements for each of the three imaging modalities were made. Measurements included vaginal length, vaginal height, vaginal width, vestibule length, vestibule height, vestibule width, cingulum height, cingulum width, cingulum area, urethral length, urethral height, urethral width, angle of urethra to vestibule and angle of vagina to vestibule. Group comparisons were made between sound spayed and intact dogs. In general, most measurements were greater in intact dogs compared to spayed dogs regardless of imaging modality utilized. Group-weight interactions (P<0.01) were found on conventional vaginourethrograms (vaginal height and length and vestibule height, length and width) and CT vaginourethrograms (vaginal length, vestibule height, length and width, cingulum area, urethral width and angle of vagina to vestibule). A three-way interaction (P<0.01) for vaginal length, vaginal height and vestibule height was also identified. Vestibule length and height, cingulum height and urethral length were larger (P<0.01) with increasing dog weight and in intact dogs for both conventional and CT vaginourethrograms. No difference in vestibulovaginal ratio was observed between intact dogs and spayed dogs (P=0.0221). One of 14 intact dogs and 8 of 12 spayed dogs had vestibulovaginal ratios <0.33 on conventional vaginourethrograms. Anatomical differences in the lower urogenital tract between spayed and intact dogs emphasizes the need to establish normal reference ranges for spayed and intact dogs.