Evaluation of the effects of nephrotomy on renal function in clinically normal cats

OBJECTIVE: To evaluate the effects of nephrotomy on renal function in clinically normal cats. ANIMALS: 20 specific-pathogen-free, 9- to 11-month-old female mixed-breed cats. PROCEDURE: Serum chemistry analyses, CBC determinations, urinalyses, microbiologic urine cultures, renal ultrasonography, abdominal radiography, and single-kidney and total glomerular filtration rate (GFR) determinations by use of renal scintigraphy and measurements of plasma disappearance of technetium 99m-diethylenetriaminepentaacetic acid were performed before surgery and at 3, 12, 26, 52, and 78 weeks after surgery in 10 cats that underwent unilateral nephrotomy and in 10 control cats that underwent a sham surgical procedure. RESULTS: Two cats (1 from each group) did not complete the study, and their data were eliminated from analyses. Unilateral nephrotomy resulted in a 10% to 20% reduction in mean single-kidney GFR, compared with that of nephrotomy contralateral control kidneys. However, mean total GFR in nephrotomy-group cats was not significantly different from that of sham-group cats. Over the 78 weeks of study, mean total GFR declined 34% and 40% in nephrotomy- and sham-group cats, respectively. Adverse events associated with nephrotomy included persistent microscopic hematuria, renal pelvis hyperechogenicity with distant shadowing on ultrasonographic evaluation, dilatation of renal pelves, and hydronephrosis. CONCLUSIONS AND CLINICAL RELEVANCE: Nephrotomy in normal functioning feline kidneys results in a modest relative reduction in renal function, compared with contralateral kidney controls, but has minimal effect on total GFR when compared with sham-operated control cats. However, any detrimental effects of nephrotomy may be magnified in cats with diseased kidneys, which may have little or no capacity for repair or compensation.     

Influence of phosphate-buffered sucrose solution on early graft function in feline renal autotransplantation

Graft perfusion with cold heparinized saline has known to induce ischemia and reperfusion injury in feline kidney transplantation. In this study, the effects of phosphate-buffered sucrose solution and heparinized saline solution on early kidney graft function were compared in feline kidney autotransplantation. Perfusion of grafts with or without hypothermic storage with chilled phosphate-buffered sucrose solution prevented ischemia and reperfusion injury despite a very short ischemic time. The results of our study suggest that phosphate-buffered sucrose perfusion and storage solution should be effective to reduce ischemia and reperfusion injury despite a very short ischemic time in feline kidney transplantation.     

The influence of a novel organ perfusion solution on early graft function in canine renal autotransplantation

Objective— To evaluate the influence of a kidney perfusion solution on early graft function in dogs.
Study Design— Experimental, randomized study.
Animals— Intact adult male mongrel dogs (n=12).
Methods— Dogs had renal autograft transplantation without ureteroneocystotomy with contralateral nephrectomy. Kidney graft flushing with a novel organ perfusion solution was compared with flushing with saline (0.9% NaCl) solution. Serum creatinine (Cr) and blood urea nitrogen (BUN) concentrations were measured daily posttransplant for 7 days. Ultrasound-guided renal biopsy was performed on postoperative day 1 for electron microscopic evaluation. Dogs were euthanatized on day 7.
Results— All dogs completed the study. Cr and BUN concentrations of the saline group were significantly greater than the organ perfusion solution group on each postoperative day ( P =.01 for S Cr; P =.001 for BUN). Electron micrographs of nuclei and mitochondria from convoluted proximal tubule cells indicated profound ultrastructural disruptions in the saline group and mild ultrastructural disruptions in the organ perfusion solution group.
Conclusion— Flushing solution composition can influence early graft function in live donor kidney transplantation.
Clinical Relevance— Use of a specialized flushing solution can improve early graft function in canine kidney transplantation, independent of antigen-mediated events.     

Evaluation of renal function in cats, using quantitative urinalysis

Two consecutive 24-hour quantitative urinalyses were performed on each of 12 healthy adult cats to evaluate the technique and obtain reference values for measurements of urinary excretion of several substances. Endogenous creatinine clearance (2.31 +/- 0.47 ml/min/kg) and urinary protein excretion (17.43 +/- 9.05 mg/kg/day) were determined. Additionally, clearances and ratios to creatinine clearances were calculated for phosphate, sodium, potassium, and chloride. The endogenous creatinine clearance value was compared with another estimate of glomerular filtration rate that was based on 99mTc(Sn) diethylene-triaminepentaacetic acid clearance (2.52 +/- 0.58 ml/min/kg). Evaluation of feline renal function, using 24-hour quantitative urinalysis techniques, has potential for clinical application, but has several important limitations as well.     

Evaluation of hepatic and renal function in cats with chediak-higashi syndrome

Cats with the Chediak-Higashi Syndrome (CHS) have partial oculocutaneous albinism, a bleeding tendency, and enlarged cytoplasmic granules in many cell types including those in the liver and kidney. Hepatic and renal function was evaluated in six CHS and six age-matched control cats to determine if the functions of these organs were compromised by the CHS trait. Serum concentrations of alanine aminotransferase, alkaline phosphatase, and total bilirubin were determined to assess the status of the liver. Sulfobromophthalein retention tests were also performed. Renal function was evaluated by determination of (14)C-inulin clearance; blood urea nitrogen and serum creatinine concentrations; 24-hour protein/creatinine ratios, percent clearance ratios of calcium, phosphorus, sodium, potassium and chloride; and urinalysis values. The CHS cats were not significantly (P > 0.05) different from the control cats in any of the above tests. Use of a non-parametric statistical test did reveal a mild difference (P = 0.047) in 24-hour protein excretion between CHS and control cats. Complete blood counts were performed, and the packed cell volume and hemoglobin concentrations were significantly lower (P< 0.05) in the CHS cats than in the control cats.     

Retrospective study of the perioperative management and complications of ureteral obstruction in 37 cats

ObjectivesTo describe perioperative management and complications, risk factors and mortality rates in cats anaesthetized for treatment of ureteral obstruction.Study designRetrospective, clinical, cohort study.AnimalsThirty-seven client-owned cats anaesthetized for ureteral surgery.MethodsRecords with sufficient data for cats treated between March 2010 and March 2013 were examined for breed, age, gender, history, concurrent diseases, pre- and post-anaesthetic biochemical and haematological parameters, American Society of Anesthesiologists classification, anaesthetic protocol, surgical technique, surgeon, perioperative complications and mortality within 48 hours after extubation. Associations between risk factors and outcome variables were evaluated using univariable analysis. Odds ratios and 95% confidence intervals were calculated for significant parameters. Sensitivity and specificity using receiving operator characteristic curve analysis were calculated for creatinine, potassium level and standard base excess (SBE) to denote survival or non-survival.ResultsPreoperatively, all cats were azotaemic: mean ± SD urea was 31.6 ± 26.9 mmol L⁻¹ and median (range) creatinine was 562 μmol L⁻¹ (95 μmol L⁻¹ to off scale). Thirteen cats were hyperkalaemic (K⁺ > 6.5 mmol L⁻¹). Anaesthesia-related complications included bradycardia (n = 8, 21.6%), hypotension (n = 15, 40.5%) and hypothermia (n = 32, 86.5%). Seven cats (18.9%) died postoperatively. Non-survivors were significantly (p = 0.011) older (9.8 ± 1.9 years) than survivors (6.4 ± 3.1 years) and had higher potassium concentrations (p = 0.040). Risk factors associated with mortality were ASA classes IV and V (p = 0.022), emergency procedures (p = 0.045) and bicarbonate administration (p = 0.002). Non-survivors had higher creatinine concentrations (p = 0.021) and lower SBE (p = 0.030).Conclusion and clinical relevanceIntraoperative anaesthetic complications were common; increased age, poor health status, preoperative bicarbonate administration, hyperkalaemia and increased creatinine were associated with increased risk for death and can be used to predict risk for complications.     

Scintigraphic, sonographic, and histologic evaluation of renal autotransplantation in cats.

OBJECTIVE: To determine scintigraphic, sonographic, and histologic changes associated with renal autotransplantation in cats. ANIMALS: 7 adult specific-pathogen-free cats: 5 males, 2 females, 1 to 9 years old. PROCEDURE: Renal autotransplantation was performed by moving a kidney (5 left, 2 right) to the left iliac fossa. Before and at multiple times after surgery, for a total of 28 days, cats were evaluated by B-mode and Doppler ultrasonography, scintigraphy, and renal biopsy. RESULTS: By 24 hours after surgery, a significant decrease (42%) in mean glomerular filtration rate (GFR) and an increase in mean renal size (81% increase in cross-sectional area) were evident in the transplanted kidney, compared with preoperative values. By postsurgery day 28, reduction in GFR was 23%. Significant changes in renal blood flow velocity were identified in both kidneys. Consistent changes in resistive index or pulsatility index for either kidney could not be identified. When all postoperative histologic data were combined, the histologic score, indicating degree and numbers of abnormalities detected, for the transplanted kidney was significantly higher than that for the control kidney. CONCLUSIONS: Significant changes in renal function, size, and histologic abnormalities develop secondary to acute tubular necrosis in cats after uncomplicated renal autotransplantation. CLINICAL RELEVANCE: Evaluation of renal size and function may be of benefit for clinical evaluation of feline renal transplant patients, whereas measurement of the resistive index may be of little clinical value.     

Effect of partial ureteral obstruction on results of renal scintigraphy in dogs

OBJECTIVE: To use scintigraphy to determine the effects of partial ureteral obstruction on renal transit time and induction of diuresis in dogs. ANIMALS: 8 adult dogs. PROCEDURE: Scintigraphy was performed, using technetium Tc 99m diethylenetriaminepentacetic acid (Tc 99m-DTPA), before and within 2 weeks after surgical induction of unilateral partial ureteral obstruction. Time of peak (TOP) for the parenchyma (pTOP) and whole kidney (wTOP) and mean-transit time (MTT) for the parenchyma (pMTT) and whole kidney (wMTT) were determined by evaluation of renal time-activity curves before and after deconvolution analysis. Percentage uptake for each kidney between 1 and 3 minutes after injection of Tc 99m-DTPA was determined and used to indicate glomerular filtration rate. The effect of diuresis was determined by measuring the slope of decrease in activity after i.v. administration of furosemide. Obstruction was documented by direct inspection of the ureter. RESULTS: There was a concomitant increase in pTOP, wTOP, pMTT, and wMTT of the kidney with the partially obstructed ureter in all dogs at various times between 2 and 9 days after surgery. Concurrently, renal time-activity curves changed shape. Percentage renal uptake of the affected kidney was decreased in 2 dogs. Response to furosemide injection was inconsistent for kidneys before surgery and for kidneys with obstructed and nonobstructed ureters after surgery. CONCLUSIONS AND CLINICAL RELEVANCE: Scintigraphy may be a useful procedure for the evaluation of renal function in dogs with ureteral obstruction. Induction of diuresis appears to be of little value for differentiating renal function in dogs with obstructed and nonobstructed ureters.     

Evaluation of erythropoiesis and changes in serum erythropoietin concentration in cats after renal transplantation

OBJECTIVE: To investigate the clinicopathologic patterns of the erythropoietic response after renal transplantation in cats with chronic renal failure (CRF). ANIMALS: 14 cats with CRF undergoing renal transplantation. PROCEDURE: Before and at intervals during a 6-month period after transplantation, serum creatinine and erythropoietin concentrations, Hct, erythrocyte indices, aggregate reticulocyte percentage, and iron variables were measured. Additionally, the number of transfusions administered to and any complications that developed in each cat were recorded. RESULTS: In all cats, preoperative azotemia resolved within 6 days after renal transplantation. Two cats had a temporary increase in serum creatinine concentration secondary to an acute graft rejection episode. Anemia (defined as Hct < 28%) resolved in 10 cats 3 to 49 days after surgery. Resolution of anemia was delayed in 2 cats that had acute rejection episodes. Serum erythropoietin concentration and reticulocyte percentage were low preoperatively; values after surgery were highly variable. Compared with preoperative values, serum erythropoietin concentration increased 1 to 4 days after surgery in 11 cats; between days 5 and 58, another increase was detected in 9 cats. Serum iron concentrations were generally low before and 14 days after transplantation. CONCLUSION AND CLINICAL RELEVANCE: The erythropoietic response was highly variable in cats after renal transplantation, but anemia typically resolved within 1 month after surgery. A delay in resolution of anemia in cats may indicate poor graft function and inadequate iron stores, suggesting the need for further evaluation for concurrent illness.     

Effect of nephrotomy on renal function and morphology in normal cats

OBJECTIVE: To assess effects over 12 weeks of bisection nephrotomy on renal function, size, and morphology in cats. STUDY DESIGN: Controlled, randomized, blinded experiment. SAMPLE POPULATION: Ten adult female cats. METHODS: Glomerular filtration rate (GFR), determined by quantitative renal scintigraphy using (99m)Technetium-diethylenetriamine-pentaacetic acid, urinalysis, urine culture, and ultrasonographic measurement of renal size were performed preoperatively. Left or right nephrotomy (5 cats/group) was performed. Total and individual kidney GFRs were determined at 2, 28, and 84 days, ultrasonographic measurements at 28 and 86 days, and ultrasound-guided biopsy at 86 days. RESULTS: No significant differences in mean GFR and kidney size of operated versus unoperated kidneys were observed. Individual GFR and renal size of all except 1 cat remained within normal limits. Two cats had evidence of transient ureteral obstruction in the immediate postoperative period. No significant, generalized histologic abnormalities were observed. CONCLUSIONS: Bisection nephrotomy in normal cats does not adversely affect renal function or morphology during the initial 12 weeks. CLINICAL RELEVANCE: Bisection nephrotomy can be safely performed in normal feline kidneys without causing a significant deleterious effect on renal function. Studies in cats with pre-existing renal insufficiency are needed to ensure adverse effects would not occur in clinical cases where this surgical procedure is warranted.     

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.     

Evaluation of the effects of premedication on gastroduodenoscopy in cats

OBJECTIVE: To evaluate the effects of hydromorphone, hydromorphone and glycopyrrolate, medetomidine, and butorphanol premedication on the difficulty and time required to pass an endoscope into the stomach and duodenum of cats anesthetized with ketamine and isoflurane. DESIGN: Randomized complete block crossover study. ANIMALS: 8 purpose-bred adult female cats. PROCEDURES: Each cat was premedicated and anesthetized 4 times with an interval of at least 7 days between procedures. Cats were premedicated with hydromorphone, hydromorphone and glycopyrrolate, medetomidine, or butorphanol administered IM. Twenty minutes after premedication, sedation was assessed by use of a subjective ordinal scale. Cats received ketamine administered IM, and 10 minutes later a cuffed orotracheal tube was placed and anesthesia maintained with isoflurane. Cats breathed spontaneously throughout the procedure. When end-tidal isoflurane concentration was stable at 1.4% for 15 minutes, endoscopy was begun. The times required to pass the endoscope through the cardiac and pyloric sphincters were recorded, and the difficulty of endoscope passage was scored by use of a subjective ordinal scale. RESULTS: No significant differences in difficulty or time required to pass the endoscope through the cardiac and pyloric sphincters were found among premedicant groups. Premedication with medetomidine resulted in the greatest degree of sedation and longest time to return to sternal recumbency. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that hydromorphone, hydromorphone and glycopyrrolate, medetomidine, and butorphanol at the doses tested can be used satisfactorily to premedicate cats prior to general anesthesia for gastroduodenoscopy.     

Characterization and treatment of acid-base and renal defects due to urethral obstruction in cats

In 23 cats, urinary obstruction of 24 to 48 hours' duration caused marked azotemia, hyperphosphatemia, hyperkalemia, and metabolic acidosis. The metabolic acidosis was a consistent finding and was severe in all cats (venous pH, 7.11 +/- 0.09). Serum sodium and chloride were normal. Glycosuria was found in 17 (74%) of the cats. There was no clear difference in blood pH, serum chemical values, or electrolyte concentrations between cats obstructed 24 hours and those obstructed 48 hours or longer. At a mean of 8.4 hours after relief of obstruction, acid-base status was corrected to normal, using fluid replacement and sodium bicarbonate therapy. Blood urea nitrogen serum creatinine, and serum inorganic phosphorus improved significantly (P less than 0.01) at a mean of 19.5 hours after treatment. Variation in azotemia after fluid replacement suggested variable decreases in glomerular filtration rate after relief of obstruction. Hypokalemia occasionally developed after relief of obstruction during the postobstructive diuresis. It was concluded that fluid and electrolyte therapy must be regulated in response to the postobstructive diuresis, to ensure proper medical management.     

Effects of dietary sodium chloride intake on renal function and blood pressure in cats with normal and reduced renal function

OBJECTIVE: To determine effects of variations in dietary intake of sodium chloride (NaCl) on systemic arterial blood pressure (ABP) in cats with normal and reduced renal function. ANIMALS: 21 adult cats (7 with intact kidneys [control cats; group C], 7 with unilateral renal infarction with contralateral nephrectomy [remnant-kidney model; group RK], and 7 with unilateral renal infarction and contralateral renal wrapping and concurrent oral administration of amlodipine [remnant-wrap model; group WA]). PROCEDURE: All cats were sequentially fed 3 diets that differed only in NaCl content (50, 100, or 200 mg of Na/kg); each diet was fed for 7 days. The ABP was recorded continuously by radiotelemetry, and renal function (glomerular filtration rate [GFR]) was determined on the sixth day of each feeding period. RESULTS: Dietary supplementation with NaCl did not affect ABP, but it increased GFR in groups C and WA. The renin-angiotensin-aldosterone axis was activated in groups RK and WA at the lowest NaCl intake, but supplementation with NaCl suppressed this activation in group WA. The lowest NaCl intake was associated with hypokalemia and a high fractional excretion of potassium that decreased in response to supplementation with NaCl. Arterial baroreceptor resetting was evident after chronic hypertension but was not modified by dietary supplementation with NaCl. CONCLUSIONS AND CLINICAL RELEVANCE: Low NaCl intake was associated with inappropriate kaliuresis, reduced GFR, and activation of the renin-angiotensin-aldosterone axis without evidence of a beneficial effect on ABP. Therefore, this common dietary maneuver could contribute to hypokalemic nephropathy and progressive renal injury in cats.