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SUMMARY

The influence of induced chronic renal failure on 24- hour urinary excretion and fractional excretion of sodium and potassium was studied in cats. Induction of chronic renal failure significantly increased fractional excretion of potassium (P < 0.0001) and sodium (P < 0.05); however, 24-hour urinary excretion of sodium and potassium decreased slightly following induction of chronic renal failure.

Fractional excretion and 24-hour urinary excretion of sodium and potassium were compared by linear regression in clinically normal cats, cats with chronic renal failure, and clinically normal and affected cats combined. In clinically normal cats, linear regression revealed only moderate correlation between fractional excretion and 24- hour urinary excretion for sodium and potassium. Linear regression of these same relationships in cats with chronic renal failure, and in clinically normal cats and cats with chronic renal failure combined, indicated low correlation.

Fractional excretions of sodium and potassium were not reliable indicators of 24-hour urinary excretion of these electrolytes in cats with chronic renal failure or unknown glomerular filtration rate. Fractional excretion of potassium and sodium correlated only moderately with 24-hour urinary excretion in clinically normal cats.

Free access
in American Journal of Veterinary Research

Summary

To determine the effects of long-term dietary protein restriction in cats with chronic renal failure (crf), 4 healthy adult cats and 7 cats with surgically induced crf were fed a high-protein (hp, 51.7% protein) diet and 4 healthy adult cats and 7 cats with surgically induced crf were fed a low-protein (lp, 27.6% protein) diet for 1 year.

Cats with induced crf that were fed the lp diet had reduced serum urea nitrogen concentrations, despite lower glomerular filtration rates, compared with cats with crf fed the hp diet. Despite five-sixths reduction in renal mass, reduced glomerular filtration rate, and azotemia, 13 of the 14 cats with induced crf retained the ability to concentrate urine and produced urine with a specific gravity > 1.035.

Cats fed the hp diet consumed significantly more calories than did cats fed the lp diet, presumably because the hp diet was more palatable. As a result of the lower caloric intake in cats fed the lp diet, these cats were protein and calorie restricted, compared with cats fed the hp diet. Cats fed the hp diet weighed significantly more than did cats fed the lp diet. Mean hematocrit and mean serum albumin concentration were significantly lower in control cats and in cats with crf fed the lp diet, compared with control cats and cats with crf fed the hp diet.

Hypokalemia developed in 4 of 7 cats with crf fed the hp diet (containing 0.3% potassium); hypokalemia did not develop in control cats fed the same diet or in cats with crf fed the lp diet containing 0.4% potassium. Excessive kaliuresis, hypomagnesemia, and metabolic acidosis did not appear to contribute to the hypokalemia. Subsequent supplementation of the hp diet with potassium gluconate prevented hypokalemia in cats with crf.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine whether underfilling blood collection tubes leads to in vitro reduction in serum measured total CO2 concentration ([TCO2]m) in canine and feline blood samples sufficient to create the impression of metabolic acidosis (pseudometabolic acidosis) or high anion gap.

Sample Population

Blood samples from healthy client-owned animals (16 dogs, 17 cats).

Procedure

Venous blood samples were collected in random order for determination of serum [TCO2] and blood gas tensions. Blood gas analysis was performed on iced, capped blood samples. In dogs, serum [TCO2] was measured in 1-, 3-, and 10-ml samples in 10-ml type-B tubes and in a 3-ml sample in 3-ml type-A tubes. In cats, serum [TCO2] was determined in 1-, 2-, and 3-ml samples in 3-ml type-A tubes and in a 3-ml sample in 10-ml type-B tubes.

Results

For dogs, serum [TCO2] in full-tube, 10-ml samples was a mean ± SD, 2.0 ± 1.1 mmol/L greater than that in 3-ml samples and 3.7 ± 1.3 mmol/L greater than the value in 1 -ml samples; both differences were significant at P < 0.0001. The serum [TCO2] in full 3-ml samples was lower by 0.4 ± 0.6 mmol/L than the value in full-tube 10-ml samples (P=0.019). For cats, serum [TCO2] in full-tube, 3-ml samples was 0.5 ± 0.6 mmol/L greater than that in 2-ml samples (P = 0.004) and was 1.5 ± 0.8 mmol/L greater than the value in 1-ml samples (P < 0.0001). Serum [TCO2] in 3-ml samples of feline blood in 10-ml tubes was 0.8 ± 0.8 mmol/L lower than that in samples from full 3-ml tubes (P = 0.0007). In dogs and cats, [TCO2] in fully filled collection tubes was approximately 6 mmol/L higher when calculated from blood gas analysis data than when chemically determined in serum.

Conclusions and Clinical Relevance

Underfilling blood collection tubes results in a false decrease in serum [TCO2], which can contribute in part to descrepancies between blood gas and chemical analyses as estimates of plasma bicarbonate concentration. This, and other in vitro effects of sample handling and collection, may result in a false assessment of metabolic acidosis in dogs and cats, (Am J Vet Res 1997; 58:343-347)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine the potential clinical usefulness of duplex Doppler estimation of arcuate artery resistive index (a measure of intrarenal blood flow impedance) for diagnosis of aminoglycoside-induced nephrotoxicosis.

Animals

30 adult, female, mixed-breed dogs, allotted to 3 groups of 10 dogs each as: toxic dosage of gentamicin, therapeutic dosage of gentamicin, and saline solution sham equivalent in volume to that of the toxic dosage of gentamicin.

Procedure

After baseline screening to establish normalcy (serum biochemical analysis, endogenous creatinine clearance determination, urinalysis, urine protein-to-creatinine ratio, urine culture, gray-scale sonography, and percutaneous ultrasound-guided renal biopsy), results of arcuate artery resistive index determination were compared with serum creatinine and urine specific gravity values on a Monday-Wednesday-Friday data collection schedule for 10 days. Endogenous creatinine clearance determination, ultrasound-guided renal biopsy, and urine culture were repeated at the end of data collection in all 3 groups.

Results

Significant differences in resistive index measurements were not observed, despite clinicopathologic and renal biopsy results compatible with severe acute tubular necrosis in dogs of the toxic dosage group.

Conclusions

Duplex Doppler sonography of arcuate artery blood flow impedance, expressed as the resistive index, appears to have poor clinical usefulness as a diagnostic tool in this disorder.

Clinical Relevance

Normal arcuate artery resistive index values obtained in dogs for which aminoglycoside-induced nephrotoxicosis is suspected do not exclude the disorder. If abnormal arcuate artery resistive index values are obtained for such dogs, further evaluation for nephropathies other than aminoglycoside-induced nephrotoxi-cosis may be considered. (Am J Vet Res 1996;57:1536–1544)

Free access
in American Journal of Veterinary Research

SUMMARY

To evaluate underlying causes of calcium oxalate urolithiasis, 24-hour excretion of urine metabolites was measured in 6 Miniature Schnauzers that formed calcium oxalate (CaOx) uroliths during periods when they were fed a standard diet and during periods when food was withheld. Serum concentrations of parathyroid hormone and 1,25-dihydroxyvitamin D also were evaluated. Serum calcium concentrations were normal in all 6 affected Miniature Schnauzers; however, during diet consumption, mean 24-hour urinary excretion of calcium was significantly (P = 0.025) higher than calcium excretion when food was withheld. In 1 dog, urinary calcium excretion was lower during the period of food consumption, compared with the period when food was withheld. Compared with clinically normal Beagles, Miniature Schnauzers that formed CaOx uroliths excreted significantly greater quantities of calcium when food was consumed (P = 0.0004) and when food was withheld (P = 0.001).

Miniature Schnauzers that formed CaOx uroliths excreted significantly less oxalate than clinically normal Beagles during fed (P = 0.028) and nonfed (P = 0.004) conditions. Affected Miniature Schnauzers also excreted abnormally high quantities of uric acid. Excretion of citrate was not different between Miniature Schnauzers with CaOx urolithiasis and clinically normal Beagles.

In 5 of 6 Miniature Schnauzers with CaOx urolithiasis, concentrations of serum parathyroid hormone were similar to values from age- and gender-matched Miniature Schnauzers without uroliths. The concentration of serum parathyroid hormone in 1 dog was > 4 times the mean concentration of clinically normal Miniature Schnauzers. Mean serum concentrations of 1,25-dihydroxyvitamin D in Miniature Schnauzers with calcium oxalate urolithiasis were similar to concentrations of clinically normal Miniature Schnauzers.

Free access
in American Journal of Veterinary Research

SUMMARY

Twenty-four-hour excretion of urine metabolites was determined in 33 clinically normal Beagles during periods of consumption of a standard diet and when food was withheld. The goal was to determine normal canine values for urine analytes incriminated in the genesis of calcium oxalate uroliths.

During periods when dogs consumed food, dairy urinary excretion of calcium, uric acid, sodium, potassium, magnesium, ammonium, and hydrogen ions were significantly (P = 0.0004, 0.0038, 0.001, 0.0001, 0.0004, 0.0001, and 0.024, respectively) higher than when food was withheld. Urinary excretion of phosphorus, oxalate, and citrate were not significantly different between samples obtained during periods of food consumption and when food was withheld. Male dogs excreted significantly higher quantities of urine oxalate than females during fed (P = 0.003) and nonfed (P = 0.003) conditions. When food was withheld, urinary uric acid excretion was significantly higher in males than females (P = 0.01). Females excreted significantly more urine calcium than males when food was withheld (P = 0.003). Our results indicated that dietary conditions influence the quantity of sodium, potassium, calcium, magnesium, and uric acid excreted in the urine of clinically normal dogs; therefore, dietary conditions should be considered when measuring the concentration of these analytes in urine.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether high systolic blood pressure (SBP) at the time of initial diagnosis of chronic renal failure in dogs was associated with increased risk of uremic crisis, risk of dying, or rate of decline in renal function.

Design—Prospective cohort study.

Animals—45 dogs with spontaneous chronic renal failure.

Procedure—Dogs were assigned to 1 of 3 groups on the basis of initial SBP (high, intermediate, low); Kaplan-Meier and Cox proportional hazards methods were used to estimate the association between SBP and development of a uremic crisis and death. The reciprocal of serum creatinine concentration was used as an estimate of renal function.

Results—Dogs in the high SBP group were more likely to develop a uremic crisis and to die than were dogs in the other groups, and the risks of developing a uremic crisis and of dying increased significantly as SBP increased. A greater decrease in renal function was observed in dogs in the high SBP group. Retinopathy and hypertensive encephalopathy were detected in 3 of 14 dogs with SBP ≥ 180 mm Hg. Systolic blood pressure remained high in 10 of 11 dogs treated with antihypertensive drugs.

Conclusions and Clinical Relevance—Results suggested that initial high SBP in dogs with chronic renal failure was associated with increased risk of developing a uremic crisis and of dying. Further studies are required to determine whether there is a cause-and-effect relationship between high SBP and progressive renal injury and to identify the risks and benefits of antihypertensive drug treatment. (J Am Vet Med Assoc 2003;222:322–329)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine whether nephrolithiasis was associated with an increase in mortality rate or in the rate of disease progression in cats with naturally occurring stage 2 (mild) or 3 (moderate) chronic kidney disease.

Design—Retrospective case-control study.

Animals—14 cats with stage 2 (mild) or 3 (moderate) chronic kidney disease (7 with nephroliths and 7 without).

Procedures—All cats were evaluated every 3 months for up to 24 months. Possible associations between nephrolithiasis and clinicopathologic abnormalities, incidence of uremic crises, death secondary to renal causes, and death secondary to any cause were evaluated.

Results—There were no clinically important differences in biochemical, hematologic, or urinalysis variables between cats with and without nephroliths at baseline or after 12 and 24 months of monitoring. No associations were detected between nephrolithiasis and rate of disease progression, incidence of uremic crises, or death.

Conclusions and Clinical Relevance—Results suggested that in cats with mild or moderate chronic kidney disease, nephrolithiasis was not associated with an increase in mortality rate or in the rate of disease progression. Findings support recommendations that cats with severe kidney disease and nephrolithiasis be managed without surgery.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine whether a renal diet modified in protein, phosphorus, sodium, and lipid content was superior to an adult maintenance diet in minimizing uremic episodes and mortality rate in cats with stage 2 or 3 chronic kidney disease (CKD).

Design—Double-masked, randomized, controlled clinical trial.

Animals—45 client-owned cats with spontaneous stage 2 or 3 CKD.

Procedures—Cats were randomly assigned to an adult maintenance diet (n = 23 cats) or a renal diet (22) and evaluated trimonthly for up to 24 months. Efficacy of the renal diet, compared with the maintenance diet, in minimizing uremia, renal-related deaths, and all causes of death was evaluated.

Results—Serum urea nitrogen concentrations were significantly lower and blood bicarbonate concentrations were significantly higher in the renal diet group at baseline and during the 12- and 24-month intervals. Significant differences were not detected in body weight; Hct; urine protein-to-creatinine ratio; and serum creatinine, potassium, calcium, and parathyroid hormone concentrations. A significantly greater percentage of cats fed the maintenance diet had uremic episodes (26%), compared with cats fed the renal diet (0%). A significant reduction in renal-related deaths but not all causes of death was detected in cats fed the renal diet.

Conclusions and Clinical Relevance—The renal diet evaluated in this study was superior to an adult maintenance diet in minimizing uremic episodes and renalrelated deaths in cats with spontaneous stage 2 or 3 CKD.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine whether a diet used for dogs with renal failure (renal food [RF]) was superior to an adult maintenance food (MF) in minimizing uremic crises and mortality rate in dogs with spontaneous chronic renal failure.

Design—Double-masked, randomized, controlled clinical trial.

Animals—38 dogs with spontaneous chronic renal failure.

Procedure—Dogs were randomly assigned to a group fed adult MF or a group fed RF and evaluated for up to 24 months. The 2 groups were of similar clinical, biochemical, and hematologic status. The effects of diets on uremic crises and mortality rate were compared. Changes in renal function were evaluated by use of serial evaluation of serum creatinine concentrations and reciprocal of serum creatinine concentrations.

Results—Compared with the MF, the RF had a beneficial effect regarding uremic crises and mortality rate in dogs with mild and moderate renal failure. Dogs fed the RF had a slower decline in renal function, compared with dogs fed the MF.

Conclusions and Clinical Relevance—Dietary modifications are beneficial in minimizing extrarenal manifestations of uremia and mortality rate in dogs with mild and moderate spontaneous chronic renal failure. Results are consistent with the hypothesis that delay in development of uremic crises and associated mortality rate in dogs fed RF was associated, at least in part, with reduction in rate of progression of renal failure. (J Am Vet Med Assoc 2002;220: 1163–1170)

Full access
in Journal of the American Veterinary Medical Association