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.     

DETERMINATION OF GLOMERULAR FILTRATION RATE IN DOGS USING CONTRAST-ENHANCED COMPUTED TOMOGRAPHY

The purpose of this project was to establish a procedure and reference values for glomerular filtration rate (GFR) using contrast-enhanced computed tomography (CT) in eight healthy dogs. A single section of the kidney was scanned sequentially after bolus injection (3 ml/s) of iohexol (300 mg/kg). Time-attenuation curves were constructed and the GFR per volume of kidney was calculated using Patlak graphical analysis software. The GFR was then converted from contrast clearance per unit volume (ml/min/ml) to contrast clearance per body weight (ml/min/kg). Individual kidney and global GFR were calculated using both CT and nuclear scintigraphy. Global GFR for each dog was also determined by plasma iohexol clearance. Contrast-enhanced CT underestimated the global GFR compared with the other two methods. The average global GFR was 2.57 +/- 0.33 ml/ min/kg using functional CT and 4.06 +/- 0.37 ml/min/kg using plasma iohexol clearance. There was significant (P < 0.05) interobserver variability of CT GFR of the right kidney and total GFR. There was decreased interobserver variability for the left kidney. There was no difference in the intraobserver variability for CT-determined individual kidney and global GFR. There was no difference between the motion corrected and nonmotion corrected values for individual and global CT GFR. Nuclear scintigraphy produced a slightly higher coefficient of variation than contrast-enhanced CT, 2.9% and 1.0%, respectively. It is hypothesized that altered renal blood flow, hematocrit of the small vessels, and nephrotoxicity play a role in the underestimation of GFR by contrast-enhanced CT.     

Relationship between plasma iohexol clearance and urinary exogenous creatinine clearance in dogs

The objective of this study was to determine if plasma iohexol clearance, computed by a 1-compartment model defined by 3 plasma samples. was an accurate measure of glomerular filtration rate (GFR) in dogs. Twenty-two adult Beagle dogs of both genders were studied. Ten dogs had intact kidneys, and 12 dogs had surgically reduced renal mass. A bolus injection of iohexol was made, and blood was obtained for plasma iohexol assay after 120, 180, and 240 minutes. Plasma was analyzed for iohexol concentration by means of 3 assay methods: chemical, high-performance liquid chromatography (HPLC), and inductively coupled plasma emission spectroscopy (ICP). Urinary clearance of exogenous creatinine was used to measure GFR for three 30-minute periods occurring between 150 and 240 minutes after iohexol injection. Plasma clearance of iohexol and renal clearance of creatinine were compared by linear regression analysis and by limits of agreement techniques. Plasma iohexol clearance and urinary exogenous creatinine clearance were significantly correlated (chemical R2 = .90; HPLC R2 = .96; and ICP R2 = .96). The 1-compartment iohexol clearance:exogenous creatinine clearance ratios were 1.04 +/- 0.17, 1.05 +/- 0.14, and 1.10 +/- 0.15 for the chemical, HPLC, and ICP methods of assay, respectively, indicating that plasma iohexol clearance slightly overestimated GFR. Assuming a +/- 2 standard deviation interval for error, corrected plasma iohexol clearance measured GFR with +/-34% accuracy for the chemical, +/-26% accuracy for the HPLC, and +/-27% accuracy for the ICP method. These results indicate that plasma iohexol clearance should have utility for detection of renal dysfunction earlier in the course of progressive renal disease than is possible with measurement of plasma creatinine or urea concentrations.     

Evaluation of the use of technetium Tc 99m diethylenetriamine pentaacetic acid and technetium Tc 99m dimercaptosuccinic acid for scintigraphic imaging of the kidneys in green iguanas (Iguana iguana)

OBJECTIVE: To evaluate the use of scintigraphy involving technetium Tc 99m diethylenetriamine pentaacetic acid ((99m)Tc-DTPA) or technetium Tc 99m dimercaptosuccinic acid ((99m)Tc-DMSA) for the determination of kidney morphology and function in green iguanas (Iguana iguana). ANIMALS: 10 healthy iguanas weighing >1.6 kg. PROCEDURE: Renal scintigraphy was performed by use of (99m)Tc-DTPA in 6 of the iguanas and by use of (99m)Tc-DMSA in all 10 iguanas. After the injection of (99m)Tc-DMSA, scans were performed for each iguana at intervals during a 20-hour period. Renal biopsies were performed in all 10 iguanas after the final scintigraphic evaluation. RESULTS: In iguanas, the use of (99m)Tc-DTPA for renal scintigraphy was nondiagnostic because of serum protein binding and poor renal uptake of the isotope; mean +/- SD (99m)Tc-DTPA bound to serum proteins was 48.9 +/- 9.9%. Renal uptake of (99m)Tc-DMSA produced distinct visualization of both kidneys. Renal uptake and soft tissue clearance of (99m)Tc-DMSA increased over the 20-hour imaging period; mean +/- SD renal uptake of (99m)Tc-DMSA was 11.31 +/- 3.06% at 20 hours. In each of the 10 iguanas, ultrasonographic and histologic examinations of biopsy specimens from both kidneys revealed no abnormalities. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that the kidneys of iguanas can be evaluated scintigraphically by use of (99m)Tc-DMSA; this technique may be potentially useful for the diagnosis of renal failure in iguanas.     

A Comparison of Inulin, Paraaminohippuric Acid, and Endogenous Creatinine Clearances as Measures of Renal Function in Neonatal Foals

The glomerular filtration rate (GFR) was estimated in eight full-term neonatal foals by the single injection inulin plasma clearance method at two days of age, the continuous infusion plasma and urinary clearance methods at three days of age, and the 12-hour endogenous creatinine clearance method at four days of age. The effective renal plasma flow (ERPF) was estimated simultaneously by the single injection para-aminohippuric acid (PAH) plasma clearance method in the eight two-day old foals and the continuous PAH infusion plasma and urinary clearance method in the eight three-day old foals. The GFR (+/- 1 SEM), as determined from the single injection plasma clearance method, was 2.30 +/- 0.34 mL/kg/min; by continuous infusion plasma clearance 2.56 +/- 0.30 mL/kg/min; by continuous infusion urinary clearance 2.82 +/- 0.32 mL/kg/min; and by 12-hour endogenous creatinine clearance 2.81 +/- 0.55 mL/kg/min. Effective renal plasma flow (+/- 1 SEM) measured by the single injection plasma clearance method was 15.22 +/- 1.5 mL/kg/min, by continuous infusion plasma clearance was 18.21 +/- 2.0 mL/kg/min. and by continuous infusion urinary clearance it was 11.95 +/- 1.9 mL/kg/min. The results of these methods were not statistically different. On a per kilogram body weight basis, the full-term neonatal foal's GFR and ERPF was determined to be comparable with adult equine GFR and ERPF.     

Pharmacokinetics of ketoprofen in the green iguana (Iguana iguana) following single intravenous and intramuscular injections.

The nonsteroidal antiinflammatory drug ketoprofen (KTP) is a commonly used antiinflammatory and analgesic agent in reptile medicine, but no studies documenting its pharmacokinetics in this species have been published. Ketoprofen was administered as a racemic mixture to green iguanas (Iguana iguana) intravenously (i.v.) and intramuscularly (i.m.) at 2 mg/kg. Pharmacokinetic analyses were performed and indicated that ketoprofen in iguanas administered by the intravenous route has a classical two-compartmental distribution pattern, a slow clearance (67 ml/ kg/hr) and a long terminal half-life (31 hr) compared to ketoprofen studies reported in mammals. When delivered by the intramuscular route, bioavailability was 78%. These data indicate the daily dosing that is generally recommended for reptile patients, as an extrapolation from mammalian data, may be more frequent than necessary.     

Estimation of Glomerular Filtration Rate in Normal Sheep by the Disappearance of Iohexol from Serum

Nesje, M., Flåøsyen, A. and Moe, L., 1997. Estimation of glomerular filtration rate in normal sheep by the disappearance of iohexol from serum. Veterinary Research Communications, 21 (1), 29-35. The aim of the study was to establish reference values for glomerular filtration rate (GFR) in healthy sheep from the clearance of iohexol in serum. Fifteen healthy sheep were tested twice with 14 to 21 days between tests. No side-effects were observed after iohexol injections and all the sheep were clinically normal during and after the study. The mean clearance of iohexol estimated by the two-compartment method was 1.8 ml/min per kg (95% CI = 1.6-2.0) in the first trial and 1.7 ml/min per kg (1.5-1.9) in the second trial. The mean GFRiohexol estimated by a one-compartment method was 1.9 ml/min per kg (1.7-2.2) in the first trial and 1.8 ml/min per kg (1.6-2.0) in the second. The GFR values were similar to those reported for the inulin method. The results indicate that the iohexol method is valid for estimating GFR in sheep, and it is easier to perform than the inulin method.     

Green iguana nephrology: a review of diagnostic techniques.

There is still much to learn about renal physiology and pathophysiology in reptiles. In the case of the green iguana, initiating causes are often inferred from poor husbandry and nutrition, or extrapolated from histopathologic interpretations made late in the course of the disease, or at postmortem. The link between parathyroid hormone and renal disease in humans has been well documented and, given the high prevalence of clinical (and subclinical) secondary nutritional hyperparathyroidism in iguanas, this certainly warrants further investigation in saurians [31,32,34,35]. Apart from hyperparathyroidism, chronic water deprivation also appears to be a common historic factor. As a foliovore originating from the high humidity rain forests of central and South America, water recovery is not considered to be an adaptive stress in Iguana iguana, and therefore, renal anatomy and physiology are considered to be non-specialized compared to more arid or aquatic reptiles [21]. These arboreal lizards do not voluntarily drink from open water but instead imbibe rain or dew droplets from foliage [2]. Maintaining such a species in low relative humidity with a water bowl from which to drink is likely to both increase insensible water losses and interfere with normal water intake. Appropriate therapeutic decisions (including euthanasia) can only be made following an accurate diagnosis. To date, our diagnoses are based largely upon the structural evaluations of renal histopathology, and renal biopsy remains our most useful tool. However, in the future it may become possible to evaluate renal function by quantifying glomerular filtration rate, proximal tubular secretion, or functional renal mass. Glomerular filtration rate may be estimated by measuring the rate of glomerular clearance of substances from the blood (e.g., iohexol). Phenolsulphonphthalein assays may offer an insight into proximal tubule secretion and renal blood flow.     

Diagnosis and surgical treatment of thyroid adenoma-induced hyperthyroidism in a green iguana (Iguana iguana).

An adult female green iguana (Iguana iguana) presented with polyphagia, loss of the dorsal spines, hyperactivity, increased aggression, tachycardia, and a bilobate mass palpable anterior to the thoracic inlet. Diagnosis of hyperthyroidism was based on a total T4 (30.0 nmol/L) elevated above that of clinically healthy iguanas (3.81 +/- 0.84 nmol/L), and histopathology confirmed a functional thyroid adenoma. Surgical thyroidectomy safely returned the lizard to a euthyroid state.     

24-hour renal clearance and excretion of endogenous substances in the mare

Urine samples were obtained from 6 healthy mares. During a 2-day acclimation period, mares were kept in stalls, fed sweet feed and mixed grass hay, and allowed free access to water and trace mineral salt. The mares were crosstied in their stalls within reach of hay, salt, and water for 24 hours during which urine was obtained by constant flow via indwelling Foley catheters. Twenty-four-hour urine production was 7,649 to 11,904 ml/day (mean = 9,212 +/- 1,9285) or 14.7 to 25.1 ml?/day. (mean = 19.3 +/- 4.1). Urinary excretion and clearance of electrolytes and protein were determined from aliquots of well-mixed, pooled 24-hour urine samples. These values were sodium (Na) = 0 to 1.7 mEq/kg/day (mean = 0.4 +/- 0.7), chloride (Cl) = 2.0 to 4.2 mEq/kg/day (mean = 3.0 +/- 0.8), phosphorous (P) = 0.03 to 0.12 mg/kg/day (mean = 0.07 +/- 0.3), potassium (K) = 3.7 to 6.5 mEq/kg/day (mean = 5.3 +/- 1.4), and creatinine (Cr) = 32.1 to 53.9 mg/kg/day (mean = 40.3 +/- 8.5). Fractional excretions of electrolytes were Na = 0% to 0.46% (mean = 0.1 +/- 0.2), Cl = 0.48% to 1.64% (mean = 1.14 +/- 0.45), P = 0.04% to 0.16% (mean = 0.08 +/- 0.04), and K = 23.9% to 75.1% (mean = 51.7 +/- 17.3). Average clearances (ml/hr/kg) were Na = 0.12 +/- 0.19, K = 64.1 +/- 17.1, Cl = 1.21 +/- 0.33, and P = 0.09 +/- 0.51. Average endogenous Cr clearance (ml/min/kg) was 1.92 +/- 0.51.(ABSTRACT TRUNCATED AT 250 WORDS)     

Estimation of glomerular filtration rate in healthy cats using single-slice dynamic CT and Patlak plot analysis

Commonly used clinical indicators of renal disease are either insensitive to early dysfunction or have delayed results. Decreased glomerular filtration rate (GFR) indicates renal dysfunction before there is a loss of 50% of functional nephrons. Most tests evaluate global rather than individual kidney function. Dynamic computed tomography (CT) and Patlak plot analysis allows for individual GFR to be tested. Our objectives were to establish a procedure and provide reference values for determination of global GFR in 10 healthy cats using dynamic CT (CTGFR). This method of GFR determination was compared against serum iohexol clearance (SIC). A single CT slice centered on both kidneys and the aorta was acquired every fifth second during and after a bolus injection of iohexol (240 mgI/ml; 300 mgI/kg) for 115 s. Using data from this dynamic acquisition, Patlak plots were obtained, GFR was calculated, and results were compared to global GFR determined by iohexol clearance. The average global CTGFR estimate was 1.84 ml/min x kg (SD = 0.43; range = [1.22, 2.45]). The average global GFR measured using SIC was 2.45 ml/min x kg (SD = 0.58; range = [1.72, 3.69]). GFR measurements estimated by both dynamic CT and SIC were positively associated (estimated Spearman rank correlation coefficient = 0.72; P = 0.0234). The CTGFR method consistently underestimated GFR with a bias of -0.62 (SE = 0.1307) when compared to SIC (P = 0.0011). In healthy cats, CTGFR was capable of determining individual kidney function and appears clinically promising.     

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.     

Measurement of glomerular filtration rate, renal plasma flow, and endogenous creatinine clearance in cheetahs (Acinonyx jubatus jubatus).

Glomerular filtration rate (GFR), renal plasma flow (RPF), and the endogenous creatinine clearance (CCr) rate were determined in 13 captive cheetahs, Acinonyx jubatus jubatus (seven females and six males, 1.5-7.5 yr of age, x = 5.02 yr), during general anesthesia with Telazol and isoflurane by measuring the urinary clearances of inulin, para-aminohipppuric acid, and endogenous creatinine, respectively. Methods to determine GFR, RPF, and endogenous CCr in captive cheetahs were evaluated, and the relationship between GFR and CCr for this species was determined. The GFR and the RPF were stable during the procedure, with mean values of 1.59+/-0.17 ml/min/kg body weight and 5.12+/-1.15 ml/min/kg body weight, respectively. Although the mean value for CCr (1.47+/-0.20 ml/min/kg body weight) was significantly less than the corresponding value for GFR, the mean difference (0.11+/-0.02 ml/min/kg weight) between the two measurements was slight, and the values were highly correlated (R2 = 0.928; P < 0.0001). The measurement of CCr in cheetahs should provide a reliable estimate of GFR, facilitating the early detection of renal disease in this species.     

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.     

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.     

Clinical evaluation of glomerular function: 24-hour creatinine clearance in dogs.

Methods of renal clearance to measure glomerular filtration rate (GFR) were compared with plasma creatinine concentration in clinically normal and partially nephrectomized dogs. Glomerular filtration rate was measured by use of a simple 24-hour creatinine clearance method in 36 normal female Beagles. Mean values were 57.6 +/- 9.3 ml/minute/m2 of body surface or 3.7 +/- 0.77 ml/minute/kg of body weight. Variability of this measurement was considerable, as determined in 4 dogs studied on 4 consecutive days. Glomerular filtration rate was measured in the same 36 dogs while they were under anesthesia, using short clearance periods to compare inulin and endogenous creatinine clearance. Mean values for inulin were 41.8 +/- 13.9 ml/minute/m2 of body surface. A close agreement with creatinine clearance was found (correlation coefficient, 0.998). Mean plasma creatinine concentration was 0.82 (range, 0.5--1.0) mg/100 ml. The value of GFR measurement compared with plasma creatinine concentration was determined in 10 dogs after 75% nephrectomy. Sixty days after partial nephrectomy, GFR was reduced to 61% of normal. Mean plasma creatinine and blood urea nitrogen were 1.2 +/- 0.14 mg/100 ml and 20.4 +/- 7.1 mg/100 ml, respectively. Thus, the detection of reduced renal function may be uncertain when plasma creatinine or blood urea nitrogen are used as a means of evaluating renal function. It was concluded that a simple method of creatinine clearance is a sensitive and useful measurement to detect early or borderline reduction in glomerular function.     

Analysis of aqueous humor obtained from normal eyes of llamas and alpacas.

OBJECTIVE: To evaluate composition of aqueous humor obtained from normal eyes of llamas (Lama glama) and alpacas (Lama pacos). SAMPLE POPULATION: Aqueous humor obtained from 10 male llamas and 10 male alpacas. PROCEDURE: All animals had normal eyes, as determined by ocular examination. Aqueous humor samples were obtained via paracentesis of the anterior chamber of animals that were heavily sedated. Chemical analysis included measurement of concentrations of sodium, potassium, magnesium, chloride, bicarbonate, phosphorus, and glucose as well as osmolality and pH. RESULTS: With the exception of potassium concentrations, values for aqueous humor composition did not differ significantly between llamas and alpacas. Mean +/- SD values for llamas and alpacas, respectively, were: sodium, 154.7 +/- 2.1 and 152.7 +/- 2.1 mEq/L; potassium, 5.3 +/- 0.4 and 4.6 +/- 0.4 mEq/L; magnesium, 1.8 +/- 0.1 and 1.7 +/- 0.1 mg/dl; chloride, 130.0 +/- 1.6 and 127.0 +/- 3.3 mEq/L; bicarbonate, 19.2 +/- 1.5 and 20.2 +/- 2.3 mEq/L; phosphorous, 2.7 +/- 0.3 and 2.5 +/- 0.4 mg/dl; glucose, 80.3 +/- 3.9 and 80.8 +/- 7.3 mg/dl; total protein, 29.0 +/- 8.6 and 31.5 +/- 10.1 mg/dl; and osmolality, 305.8 +/- 11.8 and 306.2 +/- 4.9 mOsm. The pH ranged from 7.5 to 8.0 for both species. Potassium concentrations were significantly higher in llamas than alpacas. CONCLUSIONS AND CLINICAL RELEVANCE: Except for potassium, composition of aqueous humor did not differ significantly between llamas and alpacas. Aqueous humor composition of llamas and alpacas is similar to that of other species that have been examined.     

Plasma biochemistry reference values of wild-caught southern stingrays (Dasyatis americana).

Stingrays are prominent marine animals; however, there are few published reference values for their blood chemistry and hematology. Twenty-eight southern stingrays (Dasyatis americana) were caught using the bottom trawl nets of fishery-independent boats operated by the South Carolina Department of Natural Resources during June and July 2002 from Winyah Bay, South Carolina, to St. Augustine, Florida. Median values of blood and plasma obtained from live animals promptly after capture are as follows: packed cell volume = 0.22 L/L (22%), total solids (TS) = 56.5 g/L (5.65 g/dl), total protein (TP) = 26 g/L (2.6 g/dl), sodium = 315 mmol/L, potassium = 4.95 mmol/L, chloride = 342 mmol/L, calcium = 4.12 mmol/L (16.5 mg/dl), phosphorus = 1.5 mmol/L (4.7 mg/dl), urea nitrogen = 444 mmol/L (1,243 mg/dl), glucose = 1.69 mmol/L (30 mg/dl), aspartate aminotransferase = 14.5 U/L, creatine phosphokinase = 80.5 U/L, osmolality = 1065 mOsm/kg, and lactate = 3.1 mmol/L. Bicarbonate was less than the low end of the instrument range (5 mmol/L) in all but three samples. Anion gap was negative in all samples. Albumin was less than the low end of the instrument range (1 g/dl) in all except one sample. Osmolality was significantly higher in the rays caught in the southern region. TS and TP values were linearly related to each other, and the equation for the fitted line is TS = (11.61 x TP) + 25.4 (in g/L) [or TS = (1.161 x TP) + 2.54 (in g/dl)]. The reference ranges reported in this study can be used to aid in the management of aquarium stingrays and to create a baseline for health monitoring of the wild Dasyatis spp.     

Use of 99mTc diethylenetriaminepentaacetic acid for assessment of renal function in dogs with suspected renal disease

The effectiveness of technetium 99m-labeled diethylenetriaminepentaacetic acid (99mTc DTPA) to assess renal function in 13 dogs with suspected renal disease was evaluated. Glomerular filtration rates (actual GFR) were determined on the basis of endogenous creatinine clearance. Predicted GFR were determined by using 99mTc DTPA within 72 hours after the determination of creatinine clearance. The percentage of an IV administered dose of 99mTc DTPA in the kidneys (percentage dose) was determined. Two equations were used to calculate predicted GFR, which were derived from previously reported linear regression analysis of inulin (In) and creatinine (Cr) GFR vs percentage dose 99mTc DTPA in dog kidneys. The correlations of actual GFR vs predicted GFR (In) and actual GFR vs predicted GFR (Cr) were both r = 0.92. The dogs' mean actual GFR was 1.73 +/- 1.35 ml/min/kg. Their mean predicted GFR (In) and predicted GFR (Cr) were 1.92 +/- 1.42 ml/min/kg and 1.85 +/- 1.27 ml/min/kg, respectively. Therefore, 99mTc DTPA can be used with high accuracy as an agent to predict GFR in dogs with suspected renal disease. The procedure for determining GFR by use of nuclear medicine was rapid and noninvasive and appeared to induce little stress in the animals evaluated.     

The relationship between some plasma clearance methods for estimation of glomerular filtration rate in dogs with pyometra

The purpose of the present study was to compare different pharmacokinetic models for estimation of glomerular filtration rate (GFR) in 50 dogs with pyometra. GFR was estimated by plasma clearance (CLplasma) of iohexol by four 1-compartment methods (CL1c), a 2-compartment method (CL2c), and the trapezoidal method (CLtr). Regression analysis was performed to establish correction formulas for prediction of CLtr from the CL1c values and to find optimal times of sampling. Standardization of clearance values to body weight (kg), body surface area (m2) and extracellular fluid volume (ECFV) was compared by ranking of values. CLtr and CL2c values were similar, whereas CL1c overestimated CLtr. CLtr could be predicted from 2 samples at 2 and 3 hours after injection, using the formula CLtr = 4.52 + 0.84CL1c - 0.00080(CL1c)2 (R2 = .97). Similar relationships were found when sampling at 2 and 4 hours or at 2, 3 and 4 hours after injection, whereas predictions from the 3- and 4-hour estimates were not optimal (R2 = .79). The 2-sample methods for calculating GFR/ECFV generally produced unreliable predictions of the complete curve GFR/ECFV values. For some dogs, the choice of standardization procedure substantially changed the apparent level of renal function relative to other dogs in the study. We conclude that by applying an appropriate correction formula, GFR may be estimated using 2 blood samples at 2 and 3, or 2 and 4 hours after injection of iohexol when renal function is normal or moderately reduced. The method of standardizing the analysis with respect to body size may influence interpretation of the results substantially.