Percutaneous ultrasonographically guided radiofrequency heat ablation for treatment of primary hyperparathyroidism in dogs

OBJECTIVE: To evaluate the efficacy and safety of ultrasonographically guided radiofrequency heat ablation of parathyroid masses in dogs with primary hyperparathyroidism. DESIGN: Clinical trial. ANIMALS: 11 dogs. PROCEDURE: In all dogs, either 1 or 2 parathyroid masses were evident ultrasonographically. Dogs were anesthetized, and a 20-gauge over-the-needle catheter was directed into the parathyroid mass via ultrasonographic guidance. Radiofrequency heat was applied to the stylet of the catheter until there was sonographically apparent change to the entire parenchyma of the mass. Serum total and ionized calcium and parathyroid hormone concentrations were monitored daily for 5 days after the ablation procedure and again at 1, 2, and 3-month intervals, if possible. Dogs were monitored for adverse effects. RESULTS: One treatment was required in 6 dogs, 2 treatments were required in 2 dogs, and treatment was unsuccessful in 3 dogs. Serum total and ionized calcium concentrations were within reference ranges within 2 days of the last procedure in all 8 successfully treated dogs. Serum parathyroid hormone concentration was decreased 24 hours after treatment in all 8 dogs. Hypocalcemia developed in 5 of the 8 successfully treated dogs, all of which required treatment. One dog had a transient voice change. Other adverse effects were not reported. CONCLUSIONS AND CLINICAL RELEVANCE: Ultrasonographically guided radiofrequency heat ablation of parathyroid masses is a safe and effective alternative to surgery in dogs with primary hyperparathyroidism.     

Percutaneous ultrasound-guided cholecystocentesis in healthy cats

Percutaneous ultrasound-guided cholecystocentesis (PUC) is a minimally invasive technique for bile collection that is used successfully in human patients with cholecystitis. Its use in veterinary medicine for evaluation of hepatobiliary disorders has been limited because of the perceived unacceptable risk of bile peritonitis. An experimental study was conducted to evaluate the safety and efficacy of PUC, to collect data on bile cytology and bacteriologic culture, and to attempt to isolate Helicobacter spp. from the bile of healthy cats. In fasted and sedated cats, PUC was performed with a 22-gauge 1.5-in. (3.81 cm) needle with an attached 12-mL syringe via a right-sided transhepatic approach (n = 1) or into the fundus of the gallbladder (n = 11) via a right ventral abdominal approach. An attempt was made to completely empty the gallbladder. A small amount of abdominal effusion, consistent with bile or blood, was seen ultrasonographically immediately after aspiration in the 1st cat. Ultrasonographic complications with the 2nd technique were not observed in the remaining 11 cats. Decreased appetite and evidence of mild abdominal pain were detected in 4 cats within 2 days after PUC. The mean neutrophil count increased 2 days after PUC (P < .01) but remained within the reference range. The bile was acellular in 11 of 12 cats, and aerobic, anaerobic, and Helicobacter spp. cultures yielded no growth in 12 of 12 cats. There were no remarkable gross or histologic lesions of abdominal organs at the postmortem examination (8 cats) performed 7-8 days after the procedure. PUC appears to be a safe and technically simple procedure. Further studies are warranted to determine the use and safety of PUC in cats with hepatobiliary diseases.     

Percutaneous ultrasound-guided chemical parathyroid ablation for treatment of primary hyperparathyroidism in dogs.

OBJECTIVE: To evaluate the efficacy, feasibility, and safety of ultrasound-guided chemical ablation of parathyroid masses in dogs with primary hyperparathyroidism. DESIGN: Prospective clinical trial. ANIMALS: 8 dogs. PROCEDURE: In all dogs, a solitary parathyroid mass was evident ultrasonographically. Dogs were anesthetized with propofol, and a 27-gauge needle was directed into the parathyroid mass under ultrasound guidance. Ethanol (96%) was injected into the mass until there was evidence of diffusion of fluid throughout the mass. Serum total calcium, ionized calcium, phosphorus, and parathyroid hormone (PTH) concentrations were monitored daily for 5 to 7 days after the ablation procedure and again 1, 3, and 6 months after the procedure. Dogs were also monitored for adverse effects. Follow-up ultrasonography was performed 5 days and 1 month after the ablation procedure. RESULTS: One injection was required in 7 dogs, and 2 injections were required in 1. Serum total and ionized calcium concentrations were within reference ranges within 24 hours after treatment in 7 dogs and within 5 days in 1 dog. Serum PTH concentration decreased and serum phosphorus concentration increased within 24 hours after treatment in all 8 dogs. Transient hypocalcemia developed in 4 dogs during the first 5 days after treatment, but only 1 dog required treatment for hypocalcemic tetany. Hypercalcemia recurred in 1 dog 1 month after the procedure and surgical removal of the parathyroid mass was required. Other adverse effects were not reported. CONCLUSIONS AND CLINICAL RELEVANCE: Ultrasound-guided chemical ablation of parathyroid masses is a safe and effective alternative to surgery for dogs with primary hyperparathyroidism.     

Transdermal methimazole treatment in cats with hyperthyroidism

The objectives of this study were to assess serum thyroxine concentrations and clinical response in hyperthyroid cats to treatment with transdermal methimazole, and to determine if further investigation is indicated.Clinical and laboratory data from 13 cats with hyperthyroidism were retrospectively evaluated. Methimazole (Tapazole, Eli Lilly) was formulated in a pleuronic lecithin organogel (PLO)-based vehicle and was applied to the inner pinna of the ear at a dosage ranging from 2.5mg/cat q 24h to 10.0mg/cat q 12h. During the treatment period, cats were re-evaluated at a mean of 4.3 weeks (recheck-1), and again at a mean of 5.4 months (recheck-2).Clinical improvement was observed, and significant decreases in thyroxine concentrations were measured at recheck-1 (mean: 39.57nmol/L, SEM: 14.4, SD: 41.2) and recheck-2 (mean: 36.71nmol/L, SEM: 13.9, SD: 45.56) compared to pretreatment concentrations (mean: 97.5nmol/L, SEM: 11.42, SD: 39.5). No adverse effects were reported.     

Efficacy of iopanoic acid for treatment of spontaneous hyperthyroidism in cats

Iopanoic acid is an iodine containing oral cholecystographic agent that has been used to treat hyperthyroidism in humans and has recently been evaluated in an experimental model of feline hyperthyroidism. The aim of this study was to evaluate the efficacy of iopanoic acid in cats with spontaneous hyperthyroidism. Eleven cats were included in the study. Eight were treated initially with 50mg orally q 12h and three were treated with 100mg orally q 12h. Prior to treatment (baseline) and at 2, 4, and 12 weeks of treatment, owner questionnaires, physical exams, complete blood count, biochemistry analyses, and T(3) and T(4) concentrations were evaluated. The mean serum T(3) concentration decreased with treatment at all time periods compared to baseline. Mean T(4) concentrations were increased at weeks 4 and 12 compared to baseline. Five cats had a partial response during the initial 4 weeks of therapy, but the effects were transient and no significant improvements in clinical signs or physical exam findings were noted at any time period. Results suggest that iopanoic acid may be beneficial for acute management of thyrotoxicosis in some cats, but is not suitable for long-term management.     

Testing for hyperthyroidism in cats.

Hyperthyroidism remains a common endocrine disorder of cats. Although relatively easy to diagnose in classically presenting cats, the increased frequency of testing cats with early or mild disease has had significant implications for the diagnostic performance of many of the routine tests currently used. Further advances in the etiopathogenesis and earlier diagnosis are only likely with the advent of a species specific feline thyroid-stimulating hormone assay.     

Diagnostic tests for hyperthyroidism in cats

The diagnosis of hyperthyroidism, one of the most common disorders affecting elderly cats, is usually straightforward and considered routine by most practitioners. Nowadays, however, most cats suffering from hyperthyroidism tend to be diagnosed earlier and at a milder stage of the disease than those cats diagnosed 10 to 25 years ago. There are, in fact, a growing number of cats with clinical signs of hyperthyroidism and palpably large thyroid glands whose baseline serum total thyroid hormone concentrations are within the normal or borderline range, making diagnosis problematic. This paper reviews the available tests used to confirm a diagnosis of hyperthyroidism in cats and discusses their overall usefulness.     

Percutaneous ultrasound-guided cholecystocentesis in dogs

Percutaneous ultrasound-guided cholecystocentesis was performed on 13 healthy beagle dogs to determine whether percutaneous ultrasound-guided cholecystocentesis in the dog was a feasible and safe procedure. Clinical, laboratory and ultrasonographic examinations were done at 0 and 10 minutes, in the 2nd and 16th hour, and on the 7th day. They included a detailed physical examination of the mucous membranes, cardiorespiratory system and abdominal organs. Laboratory examinations of the blood consisted of a complete blood count, determination of packed cell volume (PCV), haemoglobin (Hb), total plasma protein (TPP), parameters of haemostasis including prothrombin time (PT), activated partial thromboplastin time (APTT), and enzyme activities reflecting hepatobiliary function, i.e. aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyltransferase (GGT). Ultrasonographic findings of the gallbladder (size, shape, wall, content) and appearance of the biliary tract and the surrounding cranial intraabdominal organs were also evaluated. Percutaneous ultrasound-guided cholecystocentesis was performed easily during the study, and dogs tolerated well the procedure performed without anaesthesia. All laboratory parameters of the blood remained within normal limits throughout the study. However, some follow-up values, i.e. PCV, TPP, APTT and ALT, demonstrated statistically significant differences when compared to baseline measurements, which might reflect the effect of 24-hour fasting before the experiment, as well as day-to-day metabolic fluctuations due to feeding and water supply during the study. There were no visible signs of bleeding from the liver, bile leakage from the gallbladder or accumulation of free peritoneal fluid during repeated ultrasonographic examinations. Percutaneous ultrasound-guided cholecystocentesis seems to be an important diagnostic procedure in canine gallbladder diseases and can be used safely and easily to gain gallbladder bile for diagnosis of bacterial cholecystitis or for investigating hepatobiliary function in the dog.     

Pharmacokinetics of methimazole in normal cats and cats with hyperthyroidism

The intravenous and oral disposition of the antithyroid drug methimazole was determined in 10 clinically normal cats and nine cats with naturally occurring hyperthyroidism. After intravenous administration of 5 mg methimazole, the mean residence time was significantly (P less than 0.05) shorter in the cats with hyperthyroidism than in the normal cats, but there was no significant difference between the mean values for total body clearance (CL), steady state volume of distribution (Vdss), terminal elimination rate constant (ke), or serum terminal half-life (t1/2) in the two groups of cats. After oral administration, the mean bioavailability of methimazole was high in both the normal cats (77.6 per cent) and cats with hyperthyroidism (79.5 per cent). The values for mean residence time, ke and serum terminal t1/2 after oral dosing were significantly shorter in the cats with hyperthyroidism than in the normal cats. However, after oral administration of methimazole there were no significant differences between the mean values for CL, Vdss, bioavailability and maximum serum concentrations or the time for maximal concentrations to be reached in the two groups of cats. Overall, most pharmacokinetic parameters for methimazole were not altered by the hyperthyroid state. However, the cats with hyperthyroidism did show a trend toward faster elimination of the drug compared with the normal cats, similar to what has been previously described for the antithyroid drug propylthiouracil in cats. These results also indicate that methimazole is well absorbed when administered orally and has a higher bioavailability than that of propylthiouracil in cats with hyperthyroidism.(ABSTRACT TRUNCATED AT 250 WORDS)     

Adrenal function in cats with hyperthyroidism

Adrenal function may be altered in animals with hyperthyroidism. The aim of the study was to assess adrenal function of hyperthyroid cats (n = 17) compared to healthy cats (n = 18) and cats with chronic diseases (n = 18). Adrenal function was evaluated by adrenocorticotropic hormone (ACTH) stimulation test and the urinary cortisol to creatinine ratio (UCCR) was determined. Length and width of both adrenal glands were measured via ultrasound. Hyperthyroid cats had significantly higher cortisol levels before and after stimulation with ACTH than the other groups. However, the UCCR was not elevated in hyperthyroid cats. The size of the adrenal glands of hyperthyroid cats was not significantly different from the size of those of healthy cats. The results indicate that cats with hyperthyroidism have a higher cortisol secretory capacity in a hospital setting. The normal size of the adrenal glands suggests that cortisol levels may not be increased permanently.     

Local current field radiofrequency hyperthermia for the treatment of superficial skin tumours in cats

Local current field radiofrequency (LCF-RF) hyperthermia was used to treat 38 superficial skin tumours (predominantly squamous cell carcinomas) of the nose, face and ears in 35 cats. LCF-RF hyperthermia was applied at 50°C for 60 seconds at single or multiple sites depending on the tumour size. Each cat was observed over a four-month period after treatment and 14 out of 35 cases were also available for re-evaluation eight months after treatment. Tumours which had not resolved completely within one month after the initial treatment were re-treated.

LCF-RF hyperthermia is most suited for the treatment of superficial skin tumours (<5 mm diameter). Ninety-two per cent (12/13) of tumours of this dimension showed some regression and 69% (9/13) completely resolved. Larger tumours >5 mm diameter) were also successfully treated. 54% (8/14) regressed but only 14% (2/14) completely resolved. LCF-RF hyperthermia is not recommmended for the treatment of tumours of the pinnae as 5 of the 6 tumours at this site failed to respond.     

An investigation of predictors of renal insufficiency following treatment of hyperthyroidism in cats

To determine if routine pre-treatment clinical data can be used to predict the development of overt renal insufficiency following treatment of feline hyperthyroidism, we studied retrospectively all non-azotemic cats undergoing treatment for hyperthyroidism at our hospital. Medical records were reviewed for signalment, clinical signs, and serum biochemical, hematologic and urinalysis parameters before and after treatment for hyperthyroidism. Two groups - cats that developed post-treatment renal insufficiency, and those that did not - were compared. No significant differences could be detected between the groups with respect to the parameters measured. Our study suggests that the results of routine pre-treatment clinical data cannot be used to reliably predict renal function after treatment for hyperthyroidism, validating the necessity of a methimazole trial prior to definitive therapy. The widely held belief that cats with pre-treatment urine specific gravity>1.035 are at less risk for development of renal azotemia after treatment of hyperthyroidism seems unwarranted.     

Efficacy and safety of transdermal methimazole in the treatment of cats with hyperthyroidism

The objective of this study was to determine whether transdermal methimazole was as safe and effective as oral methimazole for the control of hyperthyroidism in cats. Forty-seven cats with newly diagnosed hyperthyroidism were randomized to receive either transdermal methimazole in pluronic lecithin organogel (PLO; applied to the inner pinna), or oral methimazole (2.5 mg q12h for either route). Cats were evaluated at weeks 0, 2, and 4 with a physical exam, body weight determination, CBC, biochemical panel, urinalysis, measurement of total levothyroxine (T4) concentration, indirect Doppler blood pressure determinaiton, and completion of an owner questionnaire. Data between the 2 groups and over time were compared by nonparametric methods. Forty-four cats followed the protocol (17 oral and 27 transdermal). Significantly more cats treated with oral methimazole had serum T4 concentrations within the reference range after 2 weeks (14 of 16 cats) compared to those treated by the transdermal route (14 of 25; P = .027). This difference was no longer significant by 4 weeks of treatment (9 of 11 for oral versus 14 of 21 for transdermal), possibly because of inadequate numbers evaluated by 4 weeks. Cats treated with oral methimazole had a higher incidence of gastrointestinal (GI) adverse effects (4 of 17 cats) compared to the cats treated with transdermal methimazole (1 of 27; P = .04), but no differences were found between groups in the incidence of neutropenia, hepatotoxicity, or facial excoriations. Although the overall efficacy of transdermal methimazole is not as high as that of oral methimazole at 2 weeks of treatment, it is associated with fewer GI adverse effects compared to the oral route.     

Percutaneous ultrasound-guided cholecystocentesis in cows.

A method was developed for percutaneous ultrasound-guided cholecystocentesis in cattle. The procedure was performed on the right side in the 9th, 10th, or 11th intercostal space of 30 cows. Of the 30 cows, 20 were slaughtered 24 hours after cholecystocentesis and the remaining 10 cows were slaughtered after a 10-day observation period. Changes in the peritoneum and gallbladder wall, observed at slaughter, were minimal. During the 10-day observation period, general behavior, attitude, and appetite of the 10 cows were normal. A transient, slight increase in rectal temperature was observed in 6 cows at 4, 5, or 8 days after cholecystocentesis. Total and differential WBC counts and total protein and fibrinogen concentrations, determined daily, were all within normal ranges. Bile samples from 20 cows were examined microscopically and biochemically. Fasciola hepatica and Dicrocoelium dendriticum eggs were observed in bile from 7 and 12 cows, respectively. Fecal examination revealed F hepatica eggs in 4 cows; D dendriticum eggs were not identified in any of the fecal samples. In 1 cow, F hepatica eggs were observed in the feces, but not in the bile. Bile acids concentration in bile varied from 12.5 to 68.5 mmol/L (mean +/- SD, 45.3 +/- 3.05 mmol/L) and in serum from 3.8 to 281.0 mumol/L (41.6 +/- 17.24 mumol/L). Negative correlation was obtained between bile acids concentration in bile and that in serum (r = -0.60, P less than 0.01). It was concluded that percutaneous ultrasound-guided cholecystocentesis in cows is a safe procedure and that microscopic and biochemical examinations of obtained bile can be useful diagnostic aids.     

Echocardiographic findings in 103 cats with hyperthyroidism

Using M-mode echocardiography, cardiac abnormalities were studied in 103 cats with untreated hyperthyroidism. In addition, follow-up echocardiography was performed on 24 of these cats to assess the long-term (4 to 21 months) effect of treatment (thyroidectomy or radioiodine) on thyrotoxic cardiac disease. The most common echocardiographic abnormality in the 103 untreated hyperthyroid cats was hypertrophy of the left ventricular caudal wall (71.9%). Hypertrophy of the interventricular septum also was documented in 39.8% of the 103 cats. Other abnormalities included high values for left atrial diameter (70.0%), aortic root diameter (18.5%), and left ventricular diameter at end diastole (45.6%). In some of these cats, indices of contractility were enhanced; in 21.4% and 14.6% of the cats, values for shortening fraction and velocity of circumferential fiber shortening, respectively, were greater than those values measured in clinically normal cats. After treatment of the hyperthyroidism, left ventricular hypertrophy resolved or improved in many of the cats, as indicated by decreases in left ventricular caudal wall and interventricular septum thicknesses. Hyperdynamic wall motion resolved in all cats after treatment, as evidenced by consistent decreases in shortening fraction and velocity of circumferential fiber shortening. Despite these improvements, some cats had one or more persistently abnormal echocardiographic values after treatment. These results suggested that in cats, hyperthyroidism commonly is associated with largely reversible cardiomyopathy. In those cats in which cardiomyopathy persists or worsens after treatment, underlying primary cardiomyopathy or thyroid hormone-induced cardiac structural damage may exist.     

Altered disposition of propylthiouracil in cats with hyperthyroidism

The oral and intravenous disposition of the anti-thyroid drug propylthiouracil (PTU) was determined in six clinically healthy cats and four cats with naturally occurring hyperthyroidism. Compared with the normal cats, the mean plasma elimination half-life of PTU was significantly (P less than 0.001) shorter in the hyperthyroid cats (77.5 +/- 5.8 minutes compared with 125.5 +/- 3.7 minutes) and the total body clearance of PTU was significantly (P less than 0.05) more rapid in the cats with hyperthyroidism (5.1 +/- 0.8 ml kg-1 min-1 compared with 2.7 +/- 0.2 ml kg-1 min-1). Following oral administration, both the bioavailability (59.7 +/- 4.9 per cent compared with 73.3 +/- 3.7 per cent) and peak plasma concentrations (14.5 +/- 1.6 micrograms ml-1 compared with 18.9 +/- 0.9 micrograms ml-1) of PTU were significantly (P less than 0.05) lower in the hyperthyroid cats than in the control cats. No difference was noted, however, between the apparent volume of distribution for PTU in the two groups of cats. Overall, results of this study indicate that the oral bioavailability of PTU is decreased and PTU disposition is accelerated in cats with hyperthyroidism.     

Prevalence of ocular abnormalities in cats with hyperthyroidism

The purpose of this study was to investigate the occurrence of ocular abnormalities in hyperthyroid cats. One hundred hyperthyroid cats and 30 clinically normal, geriatric cats were studied. In both groups, ophthalmic examination was performed by use of slit-lamp biomicroscopy and indirect ophthalmoscopy after application of 1% tropicamide to dilate the pupil. Ocular abnormalities were common in both the hyperthyroid and euthyroid cats. Approximately 75% of all eyes were affected with 1 or more abnormalities, and the range of abnormalities involved all structures of the eye. Significant differences between the euthyroid and hyperthyroid cats were found in the prevalence of prominent suture lines, nonpigmented deposits on the posterior lens capsule, hyperreflective ring around the optic nerve, and hyperpigmentation of the area centralis, but all of these abnormalities were more common in the euthyroid cats than in the cats with hyperthyroidism. Active retinal lesions were only observed in 3 hyperthyroid cats (3%). The results of this study indicate that hyperthyroidism does not seem to be a frequent cause of abnormalities in the eyes of cats.