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Summary

Renal mass was surgically reduced in 78 dogs by uninephrectomy or by combined renal infarction and uninephrectomy. Renal clearance of inulin and renal clearance of exogenous creatinine were determined simultaneously, and the creatinine to inulin clearance (c/i) ratio was calculated. Clearance procedures were performed 2 to 3 months after reduction of renal mass, and were repeated at intervals thereafter. Overall, the c/i ratio was 1.008 ± 0.007 for 192 determinations, with a highly significant correlation (R2 = 0.994, P < 0.0001) between creatinine clearance and inulin clearance. There was no significant effect of gender of dogs, time after partial renal ablation, or dietary protein intake on c/i ratios. Degree of renal ablation did not affect c/i ratios. The results indicated that exogenous creatinine clearance is a valid measure of glomerular filtration rate in both male and female dogs with reduced renal mass.

Free access
in American Journal of Veterinary Research

Summary

An Escherichia coli bacterial prostatitis was experimentally induced in dogs to determine the effect of castration on chronic bacterial prostatitis. Two weeks after instillation of bacteria directly into the prostate gland, 17 of 22 adult mixed-breed male dogs had positive urine or prostatic fluid cultures or both. Seven of the 17 dogs were randomly chosen to be castrated, and 10 of the 17 served as sham-operated controls.

At weekly intervals, urine was obtained from 17 dogs for aerobic microbiologic culturing. At each week, dogs with no bacterial growth in the cultured urine had prostatic fluid collected for aerobic microbiologic culture. Dogs with negative urine, prostatic fluid, and prostatic tissue needle biopsy culture results at week 7 were euthanatized. For remaining dogs, weekly cultures were continued until the dogs were euthanatized at week 12. None of the 7 castrated dogs and 6 of the 10 dogs subject to sham operation had prostatic infection at the time of necropsy. The castrated dogs had a mean infection duration of 4.2 weeks, which was statistically shorter than the 9.5 week mean duration of infection in the sham-operated controls.

Cultures of prostatic tissue obtained immediately after euthanasia correlated 100% with urine and prostatic fluid cultures taken before euthanasia. All of the 6 dogs with positive prostatic cultures at termination had moderate to marked lymphoplasmacytic chronic prostatitis. The 11 dogs that were not infected at the end of the study had normal to moderate lymphoplasmacytic chronic prostatitis on histologic examination.

Because castration reduced the duration of infection and resulted in fewer bacterial colony forming units per milliliter of urine, castration appears to be beneficial in the resolution of chronic bacterial prostatitis in this experimental model.

Free access
in Journal of the American Veterinary Medical Association

Summary

Twenty-four dogs with induced, severe chronic renal failure were allotted to 2 groups of 12 each. Group-A dogs were fed a 0.4% phosphorus (P)/0.6% calcium, 32% protein diet, and group-B dogs were fed a 1.4% P/l.9% calcium, 32% protein diet. Dogs were studied over 24 months to determine clinical status, survival, blood biochemical alterations, glomerular filtration rate (gfr), urinary excretion of P and protein, renal morphologic changes, and renal tissue concentrations of calcium, P, and magnesium.

Group-A dogs developed statistically significant differences from group-B dogs in several blood biochemical values (pcv and total solids, calcium, P, potassium, sodium, chlonde, total CO2 (TCO2), anion gap, and parathyroid hormone concentrations) and in urinary P excretion.

Mean ( ± sem) gfr values in group-A and group-B dogs were nearly identical when diets were initiated (group _A = 0.73 ± 0.05 ml/min/kg of body weight; group B = 0.72 ± 0.08 ml/min/kg), but significantly (P = 0.0346) lower gfr developed in group-B than in group-A dogs over time. At 24 months, gfr in survivors was 0.83 ± 0.08 and 0.63 ± 0.15 ml/min/kg for dogs of groups A and B, respectively.

Other measurements favored the hypothesis that P/calcium restriction was beneficial, but values failed to reach statistical significance. Survival was greater at 24 months in group-A than in group-B (7 vs 5) dogs, and renal tissue concentrations of calcium and P were higher in group-B than in group-A dogs.

Differences were not detected between groups in urinary excretion of protein and in the type or severity of renal lesions.

We conclude that P/calcium restriction at 32% protein intake is beneficial to dogs with chronic renal failure, but that the degree of restriction imposed in group-A dogs of this study did not prevent development of abnormalities. Factors other than dietary P/calcium intake may have a role in progression of renal failure to uremia.

Free access
in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine whether the angiotensin converting enzyme inhibitor enalapril would lower systemic arterial and glomerular capillary pressure and reduce the magnitude of renal injury in a canine model of renal insufficiency.

Animals—18 adult dogs that had renal mass reduced by partial nephrectomy.

Procedure—After surgical reduction of renal mass and baseline measurements, dogs in 2 equal groups received either placebo (group 1) or enalapril (0.5 mg/kg, PO, q 12 h; group 2) for 6 months.

Results—Values for systemic mean arterial blood pressure determined by indirect and direct measurement after 3 and 6 months of treatment, respectively, were significantly lower in group 2 than in group 1. During treatment, monthly urine protein-to-creatinine ratios were consistently lower in group 2 than in group 1, although values were significantly different only at 3 months. At 6 months, significant reduction in glomerular capillary pressure in group 2 was detected, compared with group 1, but glomerular filtration rate in group 2 was not compromised. Glomerular hypertrophy, assessed by measurement of planar surface area of glomeruli, was similar in both groups. Glomerular and tubulointerstitial lesions were significantly less in group 2, compared with group 1.

Conclusions and Clinical Relevance—Data suggest that inhibition of angiotensin converting enzyme was effective in modulating progressive renal injury, which was associated with reduction of glomerular and systemic hypertension and proteinuria but not glomerular hypertrophy. Inhibition of angiotensin converting enzyme may be effective for modulating progression of renal disease in dogs. (Am J Vet Res 2003;64:321–327)

Full access
in American Journal of Veterinary Research

Abstract

Objective

To determine effects of dietary protein and calories on progression of induced chronic renal failure in cats.

Animals

28 young adult female cats.

Procedure

Renal mass was reduced surgically, and glomerular filtration rate (GFR) was determined. Cats were allotted to 4 groups of 7 with similar mean GFR (1.52 to 1.55 ml/min/kg of body weight). Diets were formulated to provide: low protein and calorie (diet A), low protein and high calorie (diet B), high protein and low calorie (diet C), and high protein and calorie (diet D) intakes. Cats were fed their prescribed diet for 12 months, then blood and urine biochemical variables were measured, after which kidney specimens were examined microscopically.

Results

Protein intake by cats of groups C and D (9.0 g/d/kg) was substantially greater than that by cats of groups A and B (5.3 and 5.2 g/d/kg, respectively). Caloric intake by cats of groups B and D (73 and 71 calories/d/kg, respectively) was greater than that by cats of groups A and C (58 and 55 calories/d/kg, respectively). Renal glomerular lesions were mild and not affected by protein, calories, or their interactions. Nonglomerular lesions, though mild, were significantly influenced by calorie intake, but not by protein or calorie-protein interactions. The GFR did not decrease in any group. Urine protein-to-creatinine ratio increased significantly in all groups after reduction of renal mass, but values from all groups remained within the reference range (0 to 0.3).

Conclusions and Clinical Relevance

Diets replete in protein were not associated with increased severity of glomerular or nonglomerular renal lesions, increased proteinuria, or decreased GFR. Diets replete in calories were not associated with increased severity of glomerular lesions, but were associated with mild increase of nonglomerular lesions. Factors other than protein and calorie intake must be considered potential causes of progression of renal failure in cats. Results raise questions about the practice of restricting quantity of protein in the diet of cats with chronic renal failure, with the intention of ameliorating development of further renal damage. (Am J Vet Res 1998;59:575–582)

Free access
in American Journal of Veterinary Research

Summary

Six parathyroidectomized (ptx) and 6 control dogs had renal mass reduced by 15/16, and were studied for effects of parathyroid hormone depletion on progression of renal failure. All ptx dogs and 4 of 6 control dogs survived until necropsy after 32 weeks.

Plasma parathyroid hormone concentration was undetectable in ptx dogs throughout the study, but was greater than normal in control dogs. Serum inorganic phosphate (P) concentration was increased in ptx dogs (6.8 ±0.1 mg/dl) and in control dogs (7.5 ± 0.2), but did not differ significantly (P = 0.254) between groups. Ionized blood calcium values (Ca2+) were significantly (P = 0.014) lower in ptx dogs (1.31 ± 0.01 mmol/L) than in control dogs (1.36 ± 0.00 mmol/L), but were more variable in ptx dogs.

Values in ptx dogs were not significantly different from those in control dogs for glomerular filtration rate (P = 0.914), plasma creatinine concentration (P = 0.903), and urine protein to creatinine ratio (P = 0.756) determined at intervals during the study. Terminal glucose tolerance and plasma insulin concentrations, P tolerance, and renal P excretion did not differ between groups.

Histologic comparison of kidneys removed during reduction of renal mass with kidneys removed at necropsy revealed development of lesions in both groups of dogs, and no protective effect from parathyroidectomy.

Mineral analysis of aorta, brain, heart, lungs, and skeletal muscle obtained at necropsy revealed no significant difference between ptx and control groups. Renal cortical calcium concentration was significantly (P < 0.05) greater in kidneys obtained at necropsy than in kidneys obtained during nephrectomy, but ptx did not protect renal cortex from calcium deposition.

Free access
in American Journal of Veterinary Research

Summary

Four diets were formulated to contain: 16% protein and 0.4% phosphorus–diet 1; 16% protein and 1.4% phosphorus– diet 2; 32% protein and 0.4% phosphorus–diet 3; and 32% protein and 1.4% phosphorus–diet 4. Forty-eight dogs were fed diet 1 for 3 months after surgical reduction of renal mass, then were allotted to 4 groups of 12 dogs each, with equal mean values for glomerular filtration rate (gfr). Dog of groups 1–4 were fed diets 1–4, respectively, for 24 months. Data collected from the dogs during and at termination of the study were analyzed statistically for effects of dietary protein, phosphorus (P), time, and interactions between these factors.

During the 24 months of study, 24 dogs developed uremia and were euthanatized for necropsy. Necropsy also was performed on the remaining 24 dogs after they were euthanatized at the end of the study. Dog survival was significantly enhanced by 0.4% P diets (vs 1.4% P diets), but survival was not significantly influenced by amount of dietary protein. The 0.4% P diets (vs 1.4% P diets) significantly increased the period that gfr remained stable before it decreased, but dietary protein did not have significant effect.

Significant blood biochemical changes attributed to P, protein, and time were identified during the study. Terminally, plasma parathyroid hormone concentration was significantly increased from prediet values in all groups of dogs.

Urine protein excretion was not significantly affected by dietary amount of either protein or P, when measured by either timed urine collection or urine protein-to-creatinine ratio. A tendency was seen for increased protein excretion with passage of time.

Histologic and mineral analyses of kidneys removed at necropsy revealed some significant difference attributable to diet, but differences were more marked when diet was ignored, and the 24 surviving dogs were compared with the 24 that developed uremia.

Overall, amount of dietary P was more important than amount of dietary protein for preventing adverse responses. However, because renal damage specifically attributable to either dietary component was not obvious, it is possible that the effects of P were manifested by extrarenal mechanisms.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine the effects of parathyroid hormone (PTH) depletion on dogs with induced chronic renal failure.

Animals

2 groups of 26 mixed-breed dogs of both sexes (13 were parathyroidectomized [PTX] and 13 had sham surgery).

Procedure

After surgical reduction of renal mass and PTX, dogs were selected for a 24-month period of study and monitored for clinical, hematologic, blood biochemical, and organ function status. On development of uremia or after 24 months, dogs were euthanatized, and tissues were examined.

Results

Higher survival rate and smaller decrement in renal function (glomerular filtration rate) were observed in PTX dogs, compared with those that had sham surgery, but values did not reach statistical significance. The PTX dogs remained hypocalcemic during the study and had lower serum Ca2+ × P product values. Regardless of parathyroid state, survivors and fatalities could be separated on the basis of serum Ca2+ × P product values. Parathyroidectomy did not prevent renal deposition of calcium, and renal lesions were poorly correlated with renal cortical calcium concentration. Abnormalities reported in dogs with renal failure, which were attributed to PTH (glucose intolerance, pulmonary hypertension), were not observed in PTX dogs or those that had sham surgery.

Conclusions and Clinical Relevance

PTX had beneficial effects, but these were mediated via changes in mineral homeostasis rather than via direct effects of PTH. Results attributable to PTX were similar to those previously obtained by dietary restriction of phosphate intake. (Am J Vet Res 1997;58:188–195)

Free access
in American Journal of Veterinary Research