Objective: To compare estimation of glomerular filtration rate determined via conventional methods (ie, scintigraphy and plasma clearance of technetium Tc 99m pentetate) and dynamic single-slice computed tomography (CT). Animals: 8 healthy adult cats. Procedures: Scintigraphy, plasma clearance testing, and dynamic CT were performed on each cat on the same day; order of examinations was randomized. Separate observers performed GFR calculations for scintigraphy, plasma clearance testing, or dynamic CT. Methods were compared via Bland-Altman plots and considered interchangeable and acceptable when the 95% limits of agreement (mean difference between methods ± 1.96 SD of the differences) were ≤ 0.7 mL/min/kg. Results: Global GFR differed < 0.7 mL/min/kg in 5 of 8 cats when comparing plasma clearance testing and dynamic CT; the limits of agreement were 1.4 and −1.7 mL/min/kg. The mean ± SD difference was −0.2 ± 0.8 mL/min/kg, and the maximum difference was 1.6 mL/min/kg. The mean ± SD difference (absolute value) for percentage filtration by individual kidneys was 2.4 ± 10.5% when comparing scintigraphy and dynamic CT; the maximum difference was 20%, and the limits of agreement were 18% and 23% (absolute value). Conclusions and Clinical Relevance: GFR estimation via dynamic CT exceeded the definition for acceptable clinical use, compared with results for conventional methods, which was likely attributable to sample size and preventable technical complications. Because 5 of 8 cats had comparable values between methods, further investigation of dynamic CT in a larger sample population with a wide range of GFR values should be performed.

Objective: To evaluate the effect of several sedation protocols on glomerular filtration rate (GFR) in cats as measured by use of quantitative renal scintigraphy and to analyze interobserver differences in GFR calculation. Animals: 5 cats (1 sexually intact male, 1 neutered male, and 3 sexually intact females). Procedures: Effects on GFR of 3 sedation protocols commonly used at the Iowa State University College of Veterinary Medicine were evaluated. The protocols were medetomidine (11 μg/kg) and butorphanol tartrate (0.22 mg/kg) administered IM; ketamine hydrochloride (10 mg/kg) and midazolam (0.5 mg/kg) administered IV; and ketamine (10 mg/kg), midazolam (0.5 mg/kg), and acepromazine maleate (0.05 mg/kg) administered IM. Results for the 3 protocols were compared with results of GFR measurements obtained in these same cats without sedation (control protocol). Results: No significant difference between GFR measurements was associated with the 3 sedation protocols, compared with GFR measurements for the control protocol. The greatest mean GFR values were for the medetomidine-butorphanol and ketamine-midazolam protocols. There were no significant differences between observers for calculation of GFR. Conclusions and Clinical Relevance: Results suggested that none of the 3 sedation protocols had significant effects on GFR calculated by use of quantitative renal scintigraphy, compared with results for GFR evaluations performed in the cats when they were not sedated. No significant interobserver error was evident. However, the statistical power of this study was low, and the probability of a type II error was high.

Technetium-99m sulfur colloid scintigraphy was used to study alterations of reticuloendothelial function in 7 dogs with experimentally induced biliary cirrhosis and portosystemic shunting. Scintigraphic studies were performed before and 6 weeks after common bile duct ligation. Radiocolloid plasma clearance rate was determined by measuring activity in plasma samples and by analyzing the rate of liver uptake on dynamic scintigraphic image sequences. Percentage of uptake in the liver, spleen, and lungs, as well as the ratio of hepatic-to-extrahepatic uptake, was determined from static equilibrium images. Relative to preoperative values, there were significant decreases in plasma clearance rate, percentage of liver uptake, and ratio of hepatic-to-extrahepatic uptake and significant increases in percentage of spleen and lung uptake on postoperative studies. The mechanism of technetium-99m-labeled sulfur colloid extraction by the liver is different from that of other radiocolloids; it does not require active phagocytosis or pinocytosis. Thus, liver uptake of this tracer principally reflects effective liver blood flow. Portosystemic shunting was documented in these dogs at the time of the postoperative radiocolloid scans, and we believed was responsible for the decrease in liver reticuloendothelial activity. Possible mechanisms for the increased splenic and pulmonary reticuloendothelial activities are discussed.

Effective renal plasma flow (ERPF) was evaluated, using the measurement of p-aminohippurate clearance (CLPAH) and quantitative renal scintigraphy (QRS) with 99mTc-mercaptoacetyltriglycine (99mTc-MAG3). The CLPAH and QRS determinations were made in 6 dogs: 2 determinations for each dog before, and 1 determination after induction of renal failure by administration of amphotericin B. Least-squares regression analysis was used to derive an equation to estimate ERPF from QRS data. The results indicated that QRS, using 99mTc-MAG3, correlated reasonably well (r = 0.82, P < 0.001) with ERPF determined from the CLPAH value. The right kidney contributed 53.3% of global ERPF (P = 0.002). Hepatobiliary excretion of 99mTc-MAG3 was variable within each dog. There was not a consistent pattern with respect to time or renal function. All dogs had nausea or emesis, or both, after IV administration of 99mTc-MAG3. The QRS method with 99mTc-MAG3 provides an adequate means to estimate ERPF in healthy dogs and dogs with renal failure.

Combined blood pool and delayed images produced by use of 99mTc-methylene diphosphonate (99mTcMDP) were evaluated as an objective measurement of the response of equine joints with osteochondral defects to postoperative exercise and intra-articularly administered polysulfated glycosaminoglycan (PSGAG). Osteochondral defects (approx 2.4 X 0.9 cm) were induced arthroscopically in the dorsodistal radial carpal bones of 18 ponies. These ponies were randomized (while balancing for age [range 2 to 15; median, 5.0; mean, 5.1 years]) to 2 treatment groups. Nine ponies were assigned to be exercised, and 9 were stall-rested. Six ponies in each group were administered PSGAG (250 mg) in 1 joint (medicated) and lactated Ringer's solution (LRS) in the contralateral joint. The 3 remaining ponies in each group were administered LRS in both joints (nonmedicated). Medication was given at surgery, then weekly for 4 weeks. The exercise protocol (begun at postoperative day 6 and conducted twice daily) started with 30 minutes walking (approx 0.7 m/s), and, by postoperative month 3, the ponies were being walked for 15 minutes and trotted (approx 1.6 m/s) for 25 minutes. Simultaneous dorsal images of both carpi were made 2 to 3 minutes after IV administration of 99mTcMDP (blood pool image) and 90 to 120 minutes later (delayed image). Scintimetry, in counts per minute per pixel per millicurie, was done before, and at 1, 2, 4, 8, 10, 13, and 17 weeks after surgery, prior to euthanasia. Radionuclide uptake on blood pool images decreased faster than that on delayed images, in which uptake remained high for 17 weeks. This indicated that bone was metabolically active for at least 17 weeks after surgery. Exercise significantly (P < 0.05) decreased uptake on the blood pool images of medicated joints up to 1 month after surgery. Thus, exercise (in the presence of PSGAG) probably had a transient, beneficial effect on soft tissues of the joint. Exercise, without PSGAG, promoted increased bone remodeling, because the highest uptake on delayed images was observed in exercised, nonmedicated ponies up to 3 months after surgery. This was consistent with development of osteoarthritis in these ponies. Medication alone stimulated bone remodeling, and data indicated that an identical effect may take place in contralateral LRS-injected joints, because of systemic circulation of the drug. However, the combination of exercise and medication appeared to moderate the independent effects of each. The combination of exercise and medication in individual joints resulted in notably (P < 0.05) decreased bone remodeling. Medication caused a decrease in bone remodeling in exercised ponies, indicating a protective effect against development of osteoarthritis.

To evaluate the use of technetium pertechnetate (99mTcO4) as a means of estimating gastric mucosal integrity, nuclear images of the empty stomach were obtained from 6 dogs at 20, 40, 60, 120, 180, and 240 minutes after IV administration of the radiopharmaceutical. Blood and gastric secretion samples were collected during the same time intervals. The left lateral-view image of the stomach was used to calculate the relative fraction of the dose in the stomach and the count density ratio. Between 20 and 40 minutes and 40 and 60 minutes, significant differences (P < 0.001) were apparent in the amount of 99mTcO4 in the stomach. Blood concentration of 99mTcO4 decreased significantly (P < 0.001), whereas gastric secretion concentration increased significantly (P < 0.001) over time. Qualitative assessment of the gastric nuclear scans and the statistical analytic results indicated that the optimal time for imaging the canine stomach was between 40 and 60 minutes after radiopharmaceutical administration. In a second study, the same dogs were pretreated with the H2-receptor antagonist cimetidine and the cholinergic antagonist glycopyrrolate to block gastric secretions. Over time, changes in the relative dose fraction in the stomach and the density ratio were the same as values obtained during the experiment performed without use of cimetidine and glycopyrrolate. Results of the study indicate that nuclear imaging with 99mTcO4 outlines normal canine gastric mucosa and that pretreatment with cimetidine and glycopyrrolate has no effect on the quality of the gastric image.

OBJECTIVE To evaluate agreement of 4 methods (Tikhonov gamma variate adaptive regularization of plasma concentration-time curve fitting applied to technetium Tc 99m diethylenetriamine pentaacetic acid [99mTc-DTPA] plasma clearance [Tk-GV], plasma clearance of exogenous creatinine [CrCL], Gates gamma camera-based measurement method with 99mTc-DTPA renal clearance and dynamic scintigraphy [GTS], and iohexol renal clearance assessed with dynamic CT with Patlak plotting [CT-Pp]) for measuring glomerular filtration rates (GFR) in healthy cats. ANIMALS 7 healthy, laboratory-raised cats. PROCEDURES Each method for measuring GFR was performed twice in 7 cats at 24-day intervals. The Wilcoxon signed-rank sum test was used to compare the results obtained from the 14 studies for each method. Results from the 4 methods were assessed for agreement and correlation. RESULTS The median GFR values were 2.75, 2.83, 3.14, and 4.26 mL/min/kg, for Tk-GV, CT-Pp, plasma CrCL, and GTS, respectively. Analysis with Wilcoxon signed-rank sum tests identified significant pairwise differences between results obtained with the Tk-GV versus the plasma CrCL method, the Tk-GV versus the GTS method, and the plasma CrCL versus the GTS method. The least variable method was Tk-GV, with an SD of 1.27 (mL/min/kg). CONCLUSIONS AND CLINICAL RELEVANCE Findings indicated that Tk-GV yielded GFR measurements comparable with those obtained with CT-Pp, plasma CrCL, and GTS; however, the Tk-GV method yielded the tightest range of results among the methods evaluated.

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 99-Tc-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. Therefore, it was concluded that neither gentamicin nor amphotericin B are useful drugs in eliciting losses of feline kidney function that may be measurable through the procedures used in this study. Contrary to all other GFR studies in the cat, this study did not use any form of pharmacologic restraint. Therefore, the findings from this study are expected to reflect accurately the true GFR healthy nonanesthetized cats.

Osseointegration involves anchoring dental implants to stable bone rather than to soft-tissue. Clinical osseointegration is currently defined as the process whereby alloplastic material is asymptomatically and rigidly fixed and maintained in bone during functional loading. Full osseointegration is necessary for the success of long-term dental implants. Recent developments in computer assisted measurement of bone formation have improved maxillofacial examination and osseointegration. Computer assisted examination has also proved effective in dental implantology.

OBJECTIVE To compare ammonia concentrations in arterial blood, venous blood, and CSF samples of dogs with and without extrahepatic portosystemic shunts (EHPSS). ANIMALS 19 dogs with congenital EHPSS and 6 healthy control dogs. PROCEDURES All dogs underwent a physical examination and then were anesthetized for transsplenic portal scintigraphy to confirm the presence or absence of EHPSS. While dogs were anesthetized, arterial and venous blood samples and a CSF sample were simultaneously collected for determination of ammonia concentration, which was measured by use of a portable blood ammonia analyzer (device A) and a nonportable biochemical analyzer (device B). Results were compared between dogs with EHPSS and control dogs. RESULTS Arterial, venous, and CSF ammonia concentrations for dogs with EHPSS were significantly greater than those for control dogs. For dogs with EHPSS, ammonia concentrations in both arterial and venous blood samples were markedly increased from the reference range. There was a strong positive correlation between arterial and venous ammonia concentrations and between blood (arterial or venous) and CSF ammonia concentrations. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that blood and CSF ammonia concentrations in dogs with EHPSS were greater than those for healthy dogs and were strongly and positively correlated, albeit in a nonlinear manner. This suggested that the permeability of the blood-brain barrier to ammonia may be abnormally increased in dogs with EHPSS, but further investigation of the relationship between blood or CSF ammonia concentration and clinical signs of hepatic encephalopathy or the surgical outcome for dogs with EHPSS is warranted.