Investigation of the effects of hyperthyroidism on renal function in the cat.

This study evaluated the effects of thyroxine on renal function in the cat. Baseline serum thyroxine (T4) concentrations, clinicopathologic data (complete blood count [CBC], serum chemistry panel, urinalysis), and nuclear medicine determinations of glomerular filtration rate (GFR), effective renal plasma flow (ERPF), and effective renal blood flow (ERBF) were measured in 10 normal adult cats. Cats were then injected with thyroxine (T4) (50 micrograms/kg SQ) daily for 30 d to induce hyperthyroidism. Clinicopathologic and nuclear medicine studies were repeated at 30 d. Cats injected with thyroxine had significant increases in T4, GFR, and ERBF and significant declines in serum creatinine and blood urea nitrogen (BUN) values. Administration of high doses of exogenous thyroxine to cats results in significant stimulation of renal function.     

Effects of methimazole on renal function in cats with hyperthyroidism

The purpose of this study was to investigate the effects of methimazole on renal function in cats with hyperthyroidism. Twelve cats with naturally occurring hyperthyroidism and 10 clinically normal (i.e., control) cats were included in this study. All cats initially were evaluated with a history, physical examination, complete blood count, serum biochemistry profile, basal serum total thyroxine concentration, complete urinalysis, and urine bacterial culture. Glomerular filtration rate (GFR) was estimated by a plasma iohexol clearance (PIC) test. After initial evaluation, hyperthyroid cats were treated with methimazole until euthyroidism was achieved. Both groups of cats were then reevaluated by repeating the initial tests four to six weeks later. The mean (+/-standard deviation) pretreatment estimated GFR for the hyperthyroid cats was significantly higher (3.83+/-1.82 ml/kg per min) than that of the control cats (1.83+/-0.56 ml/kg per min). Control of the hyperthyroidism resulted in a significantly decreased mean GFR of 2.02+/-0.81 ml/kg per minute when compared to pretreatment values. In the hyperthyroid group, the mean increases in serum urea nitrogen (SUN) and creatinine concentrations and the mean decrease in the urine specific gravity after treatment were not statistically significant when compared to pretreatment values. Two of the 12 hyperthyroid cats developed abnormally high serum creatinine concentrations following treatment. These results provide evidence that cats with hyperthyroidism have increased GFR compared to normal cats, and that treatment of feline hyperthyroidism with methimazole results in decreased GFR.     

QUANTITATIVE AND QUALITATIVE SCINTIGRAPHIC MEASUREMENT OF RENAL FUNCTION IN DOGS EXPOSED TO TOXIC DOSES OF GENTAMICIN

Five, 3-month-old mongrel dogs weighing between 4.5 to 5.5 kg were studied to evaluate and compare the efficiency of 99mTc-DTPA, 99mTc-MAG3, and 99mTc-DMSA in detecting gentamicin-induced renal tubular injury. After baseline renograms using all three methods, all dogs received daily intramuscular injections of gentamicin at a dose of 30-45 mg/kg. Additional studies were obtained after a cumulative dose of 450, 1,575, and 2,250 mg of gentamicin was reached. Glomerular filtration rate (GFR), effective renal plasma flow (ERPF), and percentage of total renal uptake measurements were calculated. Baseline and post-gentamicin injection blood urea nitrogen (BUN) and serum creatinine values were determined. A Duncan test revealed significant renal function impairment at 450 mgs of cumulated gentamicin with 99mTc-DMSA and at 1,575 mgs of cumulated gentamicin for 99mTc-DTPA and 99mTc-MAG3. There was no correlation between BUN and serum creatinine values when compared to gentamicin (p > 0.05). The images obtained with 99mTc-MAG3 were of better quality than those obtained with 99mTc-DTPA even under severe renal dysfunction. Percentage of 99mTc-DMSA uptake indicated renal damage, before than GFR and ERPF. BUN and serum creatinine measurements were poor indicators of gentamicin-induced renal failure.     

Clinical application of plasma clearance of iohexol on feline patients

Glomerular filtration rate (GFR) was estimated by plasma clearance of iohexol (PCio) in 52 conscious cats presented for a variety of reasons to Angel Animal Hospital over a 2-year period. Cats were divided into four groups according to their clinical conditions and reasons for measuring PCio. The median PCio (ml/min/kg) was 3.68 in normal cats (NM), 2.39 in cats with suspected renal disease (SP), 1.35 in cats referred to confirm renal dysfunction (RD), and 0.84 in cats with apparent clinical signs of renal failure (RF). There was a significant difference between the results for each group. The respective medians of blood urea nitrogen (BUN) and plasma creatinine concentration (Pcr) (mg/dl) were 15 and 1.40 in NM cats, 21 and 1.71 in SP cats, 30 and 2.20 in RD cats, and 48 and 3.30 in RF cats. The reference values of BUN and Pcr were 21 +/- 7 mg/dl and 1.5 +/- 0.4 mg/dl (mean +/- SD). Diminished renal function could not be detected in SP cats by either BUN or Pcr, while a marked decrease of GFR was demonstrated before BUN and Pcr increased, indicating the insensitivity of BUN and Pcr in detecting renal dysfunction in cats. PCio can be performed non-invasively in conscious cats, which improves the veterinarian's ability to detect early stages of chronic renal disease.     

Acute intrinsic renal failure in cats: 32 cases (1997-2004)

OBJECTIVE: To determine patient demographics, clinicopathologic findings, and outcome associated with naturally acquired acute intrinsic renal failure (ARF) in cats. DESIGN: Retrospective case series. ANIMALS: 32 cats with ARF. PROCEDURES: Cats were considered to have ARF if they had acute onset of clinical signs (< 7 days), serum creatinine concentration > 2.5 mg/dL (reference range, 0.8 to 2.3 mg/dL) and BUN > 35 mg/dL (reference range, 15 to 34 mg/dL) in conjunction with urine specific gravity < 1.025 or with anuria or increasing serum creatinine concentration despite fluid therapy and normal hydration status, and no signs of chronic renal disease. Cases were excluded if cats had renal calculi or renal neoplasia. RESULTS: Causes of ARF included nephrotoxins (n = 18 cats), ischemia (4), and other causes (10). Eighteen cats were oliguric. For each unit (mEq/L) increase in initial potassium concentration, there was a 57% decrease in chance of survival. Low serum albumin or bicarbonate concentration at initial diagnosis was a negative prognostic indicator for survival. Initial concentrations of BUN, serum creatinine, and other variables were not prognostic. Seventeen (53%) cats survived, of which 8 cats had resolution of azotemia and 9 cats were discharged from the hospital with persistent azotemia. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that survival rates of cats with ARF were similar to survival rates in dogs and that residual renal damage persisted in approximately half of cats surviving the initial hospitalization.     

Renal effects of carprofen administered to healthy dogs anesthetized with propofol and isoflurane

OBJECTIVE: To evaluate renal effects of carprofen in healthy dogs following general anesthesia. DESIGN: Randomized clinical trial. ANIMALS: 10 English hound dogs (6 females and 4 males). PROCEDURE: Dogs were randomly assigned to control (n = 5) or carprofen (5) groups. Anesthesia was induced with propofol (6 to 8 mg/kg [2.7 to 3.6 mg/lb] of body weight, i.v.) and maintained with isoflurane (end-tidal concentration, 2.0%). Each dog underwent two 60-minute anesthetic episodes with 1 week between episodes, and mean arterial blood pressure was maintained between 60 and 90 mm Hg during each episode. Dogs in the carprofen group received carprofen (2.2 mg/kg [1 mg/lb], p.o.) at 9:00 AM and 6:00 PM the day before and at 7:00 AM the day of the second anesthetic episode. Glomerular filtration rates (GFR) were determined during each anesthetic episode by use of renal scintigraphy. Serum creatinine and BUN concentrations and the urine gamma-glutamyltransferase-to-creatinine concentration (urine GGT:creatinine) ratio were determined daily for 2 days before and 5 days after general anesthesia. RESULTS: Significant differences were not detected in BUN and serum creatinine concentrations, urine GGT:creatinine ratio, and GFR either between or within treatment groups over time. CONCLUSIONS AND CLINICAL RELEVANCE: Carprofen did not significantly alter renal function in healthy dogs anesthetized with propofol and isoflurane. These results suggest that carprofen may be safe to use for preemptive perioperative analgesia, provided that normal cardiorespiratory function is maintained.     

Systemic Toxicity Associated With Doxorubicin Administration in Cats

The systemic toxicity of doxorubicin, 30 mg/m² body surface area (BSA) every 21 days to a cumulative dose of 300 mg/m², was evaluated in six cats. Appetite, body weight, and the presence of vomiting and/or diarrhea were monitored throughout the study. Renal function was monitored by measuring serum blood urea nitrogen (BUN) and creatinine concentrations, urine specific gravity, and creatinine clearance before each treatment. Electrocardiograms and echocardiograms were also done before each treatment. The cats were killed 3 weeks after the last treatment, and complete necropsies were performed. Partial or complete anorexia occurred in all cats with significant weight loss occurring after a cumulative doxorubicin dose of 150 mg/m² BSA. Mild vomiting and diarrhea that required no treatment also occurred sporadically in all cats. Echocardiographic changes consistent with doxorubicin-induced cardiomyopa-thy occurred in four cats after cumulative doses of 170 to 240 mg/m² BSA. Clinical heart disease and electrocardiographic changes were not observed. Subsequent histological examination revealed myocyte vacuolization and myocytolysis in all six hearts. Renal dysfunction, characterized by increasing azotemia with progressively more dilute urine, was detected in two cats. Mean creatinine clearance values also decreased significantly throughout the study. At necropsy, all cats had histological evidence of renal disease. (Journal of Veterinary Internal Medicine 1993; 7:309–317. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Association of laboratory data and death within one month in cats with chronic renal failure

OBJECTIVES: To retrospectively compare the data taken at the first visit of 34 cats with chronic renal failure surviving more than one month (surviving group) and 16 cats dying within one month (non-surviving group). METHODS: Records were collected on cats with chronic renal failure presented to a private veterinary practice in Nagoya, Japan, from March 1996 to March 2005. All cats with chronic renal failure diagnosed on the basis of case histories, clinical signs (such as, lethargy, anorexia, loss of bodyweight and vomiting) and a high plasma creatinine (>180 micromol/l) were included in the study. RESULTS: Plasma creatinine, urea nitrogen, inorganic phosphate, packed cell volume and urine protein/creatinine ratio were significantly different between cats of the surviving and non-surviving groups. In the surviving group, survival statuses were recorded, and laboratory data was obtained within one month before death in 13 cats. In the 13 cats, plasma creatinine, packed cell volume and urine protein/creatinine ratio showed significant differences between the data taken within one month before death and that taken at first visit, and only urine protein/creatinine ratio exhibited a consistent alteration (increase) in relation to first visit data. CLINICAL SIGNIFICANCE: These results indicated that plasma creatinine, urea nitrogen, inorganic phosphate, packed cell volume and urine protein/creatinine ratio were associated with death within one month and urine protein/creatinine ratio was most likely to be associated with mortality in cats with chronic renal failure.     

Effects of benazepril hydrochloride in cats with experimentally induced or spontaneously occurring chronic renal failure

We examined effects of an angiotensin converting-enzyme inhibitor, benazepril hydrochloride (BH), on renal hypertension and chronic renal failure (CRF) in cats. For experimental CRF, healthy cats (n=5) underwent 7/8 renal ablation. After renal insufficiency and hypertension were confirmed by blood urea nitrogen (BUN), serum creatinine, creatinine clearance and telemetric recording of systemic blood pressure, BH was administered orally once daily at 0.9 to 2.0 mg/kg/day for 2 to 3 weeks. Within 2 months after renal ablation, renal failure and hypertension developed as evidenced by significant increases in BUN, serum creatinine and systemic blood pressure (p<0.01 or 0.05) and significantly decreased creatinine clearance accompanied by elevated plasma renin activity, angiotensin I and II, and aldosterone (p<0.01 or 0.05). BH administration corrected systemic hypertension (p<0.05) and significantly reduced angiotensin II and aldosterone (p<0.05). Upon discontinuation of BH, these values returned to the pre-administration levels. Studies on spontaneous CRF enrolled 11 cats with spontaneously occurring CRF. BH was administered orally to 6 cats once daily for 24 weeks at a final dose of 1.0 mg/kg/day, while 5 cats served as control. BH administration reduced serum creatinine and urinary protein concentration in every cat. Results demonstrate that in cats, loss of renal mass leads to activation of the renin-angiotensin-aldosterone system and associated renal hypertension, and indicate that BH is effective in correcting renal hypertension and may provide renal benefits to cats with CRF.     

CLINICAL APPLICATION OF PATLAK PLOT CT‐GFR IN ANIMALS WITH UPPER URINARY TRACT DISEASE

Glomerular filtration rate (GFR), an important parameter of renal function, is difficult to assess clinically. Serum creatinine and blood urea nitrogen measurements lack sensitivity, whereas radionuclide determination of GFR is not always available and requires postinjection patient isolation. GFR can be determined using computed tomography (CT), most commonly via Patlak plot analysis. Four adult cats, two adult dogs, and a foal underwent abdominal CT under general anesthesia for various diseases of the upper urinary tract. CT‐GFR was measured with a single‐slice dynamic acquisition and Patlak plot analysis. In five animals, the total CT‐GFR appeared to be below normal, corresponding with mild (two animals) and moderate (two animals) increases of serum creatinine in four. In the two animals with normal or increased CT‐GFR, serum creatinine was within the reference values. A significant negative logarithmic relationship was found between CT‐GFR and serum creatinine values (P=0.008; r²=0.75). No complications occurred during or following CT‐GFR. CT examination provided clinically relevant information in 3/5 patients with possible ureteral obstruction and in 3/3 patients with suspected ureteral calculi. Single‐slice dynamic CT‐GFR was practical and provided clinically useful information in this small series of patients undergoing CT of the upper urinary tract. There was a significant relationship between CT‐GFR and serum creatinine values, which supports the clinical potential of CT‐GFR and justifies further investigation of this technique.     

Quantitative renal scintigraphic determination of the glomerular filtration rate in cats with normal and abnormal kidney function, using 99mTc-diethylenetriaminepentaacetic acid.

The nuclear imaging technique known as quantitative renal scintigraphy was validated as a means to assess the kidney function of cats. Renal function tests were performed in 6 healthy cats and 3 cats with clinical manifestations of kidney failure. In addition, the nephrotoxic drugs, gentamicin sulfate, or amphotericin B were used in an attempt to induce renal failure in 4 cats. Using linear regression analysis, equations were derived to estimate the glomerular filtration rate (GFR) on the basis of the renal percent uptake of 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA). One-way ANOVA and Student's t test were used to evaluate treatment effects on clearances of inulin and creatinine, percent uptake of 99mTc-DTPA, and serum creatinine concentrations. The results show that the percent uptake of 99mTc-DTPA by the kidneys correlated well with the GFR obtained through the clearance of inulin. Thus, it was concluded that quantitative renal scintigraphy, using 99mTc-DTPA as a marker of kidney function, is an adequate technique to estimate the kidney function of healthy cats and cats with functional renal impairment. The best estimate of the GFR of cats, using the percentage dose of 99mTc-DTPA, was obtained on the 1- to 3-minute postinjection interval of the marker, using data that was background-subtracted, but not corrected for tissue absorption of gamma rays or binding of 99mTc-DTPA to plasma proteins. There was no significant difference in the mean inulin clearance, creatinine clearance, or percent uptake of 99mTc-DTPA between the 3 treatment groups of this study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of fenoldopam on renal function after nephrotomy in normal dogs

OBJECTIVE: To evaluate effects of fenoldopam on renal function in normal dogs subjected to bisection nephrotomy. In addition, effects of bisection nephrotomy on renal function in normal dogs were evaluated. STUDY DESIGN: Controlled, randomized, blinded experiment. SAMPLE POPULATION: Sixteen mixed-breed adult dogs. METHODS: Dogs were paired for sex, body weight, and approximate age and assigned to 1 of 2 groups: fenoldopam (F) or placebo (P). Baseline glomerular filtration rate (GFR) based on quantitative renal scintigraphy using (99m)Tc-DTPA, blood urea nitrogen (BUN), serum creatinine (SCr), urinalysis, and urine culture were performed before surgery. Left nephrotomy was performed via median celiotomy. Group F dogs were administered intravenous (IV) fenoldopam (0.1 microg/kg/min) for 90 minutes, whereas group P dogs were administered an equivalent volume of saline (0.9 % NaCl) solution for 90 minutes. Temperature, heart rate, respiration, direct arterial blood pressure, and urine volume were recorded during anesthesia. Renal function was assessed by measuring SCr, BUN, and GFR at 1, 21, and 42 days after surgery. RESULTS: There was no significant difference between groups in measured physiologic variables. No significant difference in GFR, BUN, or SCr between groups or between operated or control kidneys was detected. CONCLUSIONS: Bisection nephrotomy in normal dogs with renal arterial occlusion of 15 minutes and using a simple continuous capsular closure does not adversely affect renal function. CLINICAL RELEVANCE: Bisection nephrotomy, as described in this study, does not decrease renal function; perioperative administration of renoprotective agents is not necessary in normal dogs.     

Urinary excretion of N-acetyl-beta-D-glucosaminidase and its isoenzymes in cats with urinary disease

The present study was designed to assess the clinical usefulness of measurement of urinary N-acetyl-beta-D-glucosaminidase (NAG) activity and its isoenzymes in cats with urinary disease. Thirty-five healthy cats and 9 cats with renal disease were used. Furthermore, a 5-year-old female cat was administered a large amount of sulfonamide in order to induce acute renal failure, and urine samples were collected for the assay of NAG activity and its isoenzymes. Urinary NAG activity was measured using p-nitrophenyl N-acetyl-beta-D-glucosaminide, and expressed as units per gram of urinary creatinine (NAG index). Urinary NAG isoenzymes were assayed by use of the mini-column method and electrophoresis. The overall mean value of urinary NAG index in healthy cats was 1.6+/-1.5 U/g. Urinary NAG index varied from 6.2 to 35.5 U/g in cats with chronic renal failure. There was no significant correlation between BUN, serum creatinine concentration and urinary NAG index. In cats with feline lower urinary tract disease, normal values of urinary NAG index were observed. In the urine samples of healthy cats, the proportions of NAG isoenzyme A (NAG-A) and isoenzyme B (NAG-B) were 79.1+/-4.4% and 21.0+/-4.4%, respectively, as assayed by the mini-column method. In the assay of NAG isoenzymes by electrophoresis, the proportions of NAG-A and NAG-B in healthy cats were 66.6+/-5.8% and 33.4+/-5.8%, respectively. The proportion of NAG-B as measured by electrophoresis was significantly larger (p<0.05) than that obtained with the mini column method. A feline case of acute renal failure experimentally-induced by sulfonamide showed elevation of urinary NAG index, NAG-A and NAG-B after injection of sulfonamide. The increase in NAG-B was larger than that of NAG-A. From the results reported here, measurement of urinary NAG and its isoenzymes seems to yield information about tubular damage at an early stage in cats with urinary disease.     

Single-injection inulin clearance for routine measurement of glomerular filtration rate in cats

Glomerular filtration rate (GFR) was determined in 53 cats using an inulin single-injection method. Thirty healthy young adult cats were used to establish normal values. The procedure was also used in 23 cats that were either older than 10 years or had borderline serum creatinine levels. The total clearance was calculated from the decay of the serum inulin concentration after injection of 3000 mg/m(2)body surface area using a two-compartment model. Concomitant inulin and iohexol clearance in nine cats showed excellent correlation between the two methods. Calculated normal values for GFR in 30 healthy cats were 35.9-58.5 (median 46.0) ml/min/m(2)or 2.07-3.69 (median 2.72) ml/min/kg. A few cats with normal creatinine or blood urea nitrogen levels were detected as having reduced GFR and therefore being in a state of early renal dysfunction. The study indicates that single-injection inulin clearance is a valuable tool for routine GFR measurement in cats. An "inulin excretion test" using only one blood sample 3h after the administration of 3000 mg/m(2)body surface area could prove an attractive alternative for the assessment of renal function in daily practice.     

Use of continuous-flow peritoneal dialysis for the treatment of acute renal failure in an adult horse

A 15-year-old Paso Fino gelding was evaluated because of acute renal failure following an episode of exertional rhabdomyolysis. The horse was azotemic and treated conservatively at another referral practice with no improvement in the azotemia. With conservative treatment and intermittent peritoneal dialysis, the horse had minimal improvement. Continuous-flow peritoneal dialysis (CFPD) was instituted on day 7 and continued for 3 consecutive days. Dramatic changes in the horse's attitude and serum creatinine concentration were detected within the first 24 hours of CFPD treatment. The horse remained hospitalized for 23 days; within 3 months of discharge, serum BUN and creatinine concentrations had returned to within the reference ranges and the horse had resumed normal activity. In adult horses, it appears that CFPD can be used to successfully treat acute renal failure that is refractory to conventional treatments.     

Effects of the angiotensin converting enzyme inhibitor benazepril in cats with induced renal insufficiency

OBJECTIVE: To determine effects of the angiotensin converting enzyme inhibitor benazepril in cats with induced renal insufficiency. ANIMALS: 32 cats. PROCEDURE: Renal mass was surgically reduced, and cats were assigned to 1 of 4 eight-cat groups. Group 1 received placebo, whereas groups 2, 3, and 4 received benazepril hydrochloride orally once daily for approximately 6.5 months at the following doses: group 2, 0.25 to 0.50 mg/kg of body weight; group 3, 0.50 to 1.00 mg/kg; and group 4, 1.00 to 2.00 mg/kg. Arterial blood pressures, glomerular filtration rate (GFR), and renal plasma flow were determined before treatment and during the treatment period. Other determinants of renal hemodynamics were measured by use of micropuncture techniques. Renal biopsy specimens were examined microscopically. RESULTS: Compared with cats that received placebo, mean systolic arterial blood pressure was significantly less and GFR significantly greater in cats that received benazepril. Glomerular capillary pressure and the ratio of efferent to afferent arteriolar vascular resistance were also significantly less in treated cats. However, histologic differences in renal specimens were not detected. CONCLUSIONS AND CLINICAL RELEVANCE: Treatment with benazepril sustained single nephron GFR in remnant nephrons of cats with induced renal insufficiency. Administration of benazepril was also associated with a small but significant reduction in degree of systemic hypertension and an increase in whole kidney GFR. Benazepril may be an effective treatment to slow the rate of progression of renal failure in cats with renal disease.     

Use of plasma clearance of iohexol for estimating glomerular filtration rate in cats

OBJECTIVE: To determine whether plasma clearance of iohexol (PCio) can be used to estimate glomerular filtration rate (GFR) in cats. ANIMALS: 4 renal-intact and 6 partially nephrectomized adult cats. PROCEDURE: Plasma clearance of iohexol was determined after IV administration of iohexol; plasma concentrations of iodine were measured by use of a colorimetric assay. Results for PCio were compared with simultaneously obtained values for urinary clearance of creatinine (CCr). RESULTS: The colorimetric assay used to measure plasma iodine concentrations was extremely precise. Results of PCio for all cats, renal-intact cats, and partially nephrectomized cats were closely associated with results of CCr. Mean difference between CCr and PCio determined for all cats was 0.95 ml/min/kg, which was < 30% of mean CCr for renal-intact cats. Coefficients of variance for PCio (5%) and CCr (8%) in renal-intact cats were similar. CONCLUSIONS AND CLINICAL RELEVANCE: Plasma clearance of iohexol determined by use of a simple colorimetric assay provided an estimation of GFR in cats that was not significantly different from that provided by CCr. Moreover, PCio more reliably estimates renal function than BUN and plasma creatinine concentrations. Because determination of PCio is less labor intensive and invasive, compared with CCr, it may be easier to perform in a clinical setting.     

Effect of renal insufficiency on the pharmacokinetics and pharmacodynamics of benazepril in cats

The effect of renal insufficiency was studied on the pharmacokinetics (PK) and pharmacodynamics (PD) of the angiotensin-converting enzyme (ACE) inhibitor benazepril in cats. The active metabolite of benazepril, benazeprilat, is eliminated principally ( approximately 85%) via biliary excretion in cats. A total of 20 control animals and 32 cats with moderate renal insufficiency induced by partial nephrectomy were used. Assessments were made at steady state after treatment with placebo or benazepril (0.25-2 mg/kg) once daily for a minimum of 10 days. The PK endpoint was the AUC (0-->24 h) of total plasma benazeprilat. The PD endpoints were systolic, diastolic and mean blood pressures (respectively SBP, DBP and MBP) measured by telemetry, and plasma ACE activity, assessed by an ex vivo assay. Renal function was assessed by glomerular filtration rate (GFR), measured by inulin clearance, and plasma creatinine concentrations (1/PCr). As compared with control animals, the renal insufficient cats had a 78% reduction in GFR (0.57 +/- 0.41 mL/min kg), increased plasma creatinine (2.7 +/- 1.0 mg/dL), urea (44.0 +/- 11.9 mg/dL) and ACE activity, and moderately increased blood pressure (SBP 171.8 +/- 5.1 mmHg) (all parameters P < 0.05). Renal insufficient cats receiving benazepril had significantly (P < 0.05) lower SBP, DBP, MBP and ACE, and higher GFR values as compared with placebo-treated animals. There were no significant differences in SBP, DBP, MBP, benazeprilat or ACE values according to the degree of renal insufficiency in cats receiving benazepril. It is concluded that no dose adjustment of benazepril is necessary in cats with moderate renal insufficiency.     

Bilateral renal ischemia as a model of acute kidney injury in cats

The objective of this study was to evaluate the effect of 1h, bilateral, warm ischemia-reperfusion kidney injury as a model of acute kidney injury in the cat. Four adult healthy cats underwent 60 min of bilateral, in vivo renal warm ischemia; three cats were sham operated controls. Kidney function was evaluated with creatinine and BUN concentration, urine protein: creatinine, and glomerular filtration rate. Post-reperfusion endothelin and renin was measured by ELISA and RT-qPCR. Blood pressure (BP), platelet count, and platelet aggregation were monitored. Renal biopsy specimens were evaluated histopathologically. There was significant reduction in renal function characterized by severe azotemia and proximal tubular brush border loss. Changes in renin or endothelin gene expression or serum concentration were not detected. No changes were detected in BP. Platelet count and hematocrit decreased markedly after ischemia and reperfusion. Sixty minutes bilateral renal ischemia is an effective model for acute renal injury.     

Hypercalcemia in cats: a retrospective study of 71 cases (1991-1997)

A retrospective study was conducted to characterize the diseases, clinical findings, and clinicopathologic and ultrasonographic findings associated with hypercalcemia (serum calcium concentration >11 mg/dL) in 71 cats presented to North Carolina State University Veterinary Teaching Hospital. The 3 most common diagnoses were neoplasia (n = 21), renal failure (n = 18), and urolithiasis (n = 11). Primary hyperparathyroidism was diagnosed in 4 cats. Lymphoma and squamous cell carcinoma were the most frequently diagnosed tumors. Calcium oxalate uroliths were diagnosed in 8 of 11 cats with urolithiasis. Cats with neoplasia had a higher serum calcium concentration (13.5 ± 2.5 mg/dL) than cats with renal failure or urolithiasis and renal failure (11.5 ± 0.4 mg/dL; P <.03). Serum phosphorus concentration was higher in cats with renal failure than in cats with neoplasia ( P < .004). Despite the fact that the majority of cats with uroliths were azotemic, their serum urea nitrogen and creatinine concentrations and urine specific gravity differed from that of cats with renal failure. Additional studies are warranted to determine the underlying disease mechanism in the cats we identified with hypercalcemia and urolithiasis. We also identified a small number of cats with diseases that are not commonly reported with hypercalcemia. Further studies are needed to determine whether an association exists between these diseases and hypercalcemia, as well as to characterize the underlying pathophysiologic mechanism for each disease process.