[Ultrasonography of the parathyroid glands in dogs--a review]

The purpose of the study was to give an overview over the usefulness of ultrasonographic examination of parathyroid glands in dogs. By means of a 10 MHz high-resolution linear transducer it was possible to visualize parathyroid glands in healthy dogs. There was a positive correlation between body weight and size of the parathyroid glands, additionally the likelihood to detect 4 glands increased with an increase in body weight. Dogs with chronic renal failure had significantly larger parathyroid glands than healthy dogs and dogs with acute renal failure. In dogs with hypercalcemia of malignancy either none or parathyroids which were small in relation to body weight were detected. In contrast visualisation of parathyroid masses in dogs with primary hyperparathyroidism was easy due to their increased size and anechoic appearance. In dogs with severe azotemia the ultrasonographic examination of the parathyroid glands is helpful to differentiate between acute and chronic renal failure, in dogs with hypercalcemia to differentiate between hypercalcemia of malignancy and hypercalcemia due to primary hyperparathyroidism.

Ultrasound evaluation of the parathyroid glands in two hypercalcemic cats

Two parathyroid masses were identified using ultrasound in two hypercalcemic cats. The masses were identified as parathyroid adenomas on surgical biopsy. Both parathyroid masses contained hypoechoic regions with distal acoustic enhancement. Both masses were greater than 1.0 cm in diameter.

Survival of cats with naturally occurring chronic renal failure: effect of dietary management

Fifty cats with naturally occurring stable chronic renal failure (CRF) were entered into a prospective study on the effect of feeding a veterinary diet restricted in phosphorus and protein with or without an intestinal phosphate binding agent on their survival from initial diagnosis. Twenty-nine cats accepted the veterinary diet, whereas compliance (due to limited intake by the cats or owner resistance to diet change) was not achieved in the remaining 21. At diagnosis, both groups of cats were matched in terms of age, bodyweight, plasma creatinine, phosphate, potassium and parathyroid hormone (PTH) concentrations, packed cell volume and urine specific gravity. Feeding the veterinary diet was associated with a reduction in plasma phosphate and urea concentrations and prevented the increase in plasma PTH concentrations seen in cats not receiving the diet. Cats fed the veterinary diet survived for longer when compared with those that were not (median survival times of 633 versus 264 days). These data suggest that feeding a diet specifically formulated to meet the needs of cats with CRF, together with phosphate binding drugs if required, controls hyperphosphataemia and secondary renal hyperparathyroidism, and is associated with an increased survival time.

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

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

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.

Rat hypoplastic kidney (hpk/hpk) induces renal anemia, hyperparathyroidism, and osteodystrophy at the end stage of renal failure

In rats with genetically hypoplastic kidneys (hpk/hpk) and associated hypogonadism (hgn/hgn), their kidneys contain only one-quarter the number of nephrons that are found in those of normal rats [26]. Not surprisingly, therefore, renal excretive function has been shown to be depressed in hpk/hpk rats [26]. In the study presented here, we have examined the process of the progression of renal failure and the development of renal secondary disease in hpk/hpk rats. The plasma concentrations of urea-nitrogen and creatinine were significantly higher in adult hpk/hpk rats than in normal rats. These values elevated gradually and the degree of renal histological damage also progressed with advancing age in the hpk/hpk rats. In addition, renal anemia appeared at 140 days of age or later in these rats, and hyperplasia of the parathyroid glands was visible macroscopically at 280 days of age. In the hpk/hpk rats plasma levels of calcium and phosphorus were significantly lower and higher than in normal rats, respectively, at 280 days of age. Pathologically, the left femora of hpk/hpk rats exhibited fibrous osteodystrophy at 280 days of age and the calcium content of the right femora (as a percentage of the dry weight of bone) was significantly lower than in normal rats at both 210 and 280 days of age. These results indicate that the reduced nephrogenesis of the hpk/hpk rats causes progressive renal failure, secondarily inducing anemia, hyperparathyroidism, and osteodystrophy.

Resolution of metastatic calcification in the paws of a cat with successful dietary management of renal hyperparathyroidism

A 10-year-old ovariohysterectomised domestic shorthaired cat was presented with multiple nodular calcifications of the footpads and interdigital spaces. Renal insufficiency was diagnosed by routine biochemistry and urinalysis. Additionally, the cat had a calcium and phosphorus solubility product greater than 70 mg/dl and elevated circulating parathyroid hormone. Dietary management of the renal disease resulted in a reduction in the mineral solubility product and normalisation of the concentration of parathyroid hormone accompanied by concurrent resolution of the pedal lesions.

Primary hyperparathyroidism caused by a functional parathyroid adenoma in a horse

A 14-year-old Arabian gelding had weight loss and anorexia of 3 weeks' duration. Results of repeated laboratory tests revealed persistent hypercalcemia and serum phosphorus concentration that was within or less than the reference range. Parathyroid hormone concentration was high. Histologic examination of specimens obtained at necropsy revealed parathyroid adenoma. A diagnosis of primary hyperparathyroidism attributable to a functional parathyroid adenoma was made. Abnormalities in calcium and phosphorus concentrations were similar to those seen with primary hyperparathyroidism in dogs, in which this syndrome is best described. Primary hyperparathyroidism should be considered to be a potential cause of hypercalcemia in horses in which other more common causes of hypercalcemia, such as humoral hypercalcemia of malignancy, nutritional secondary hyperparathyroidism, chronic renal failure, vitamin D toxicosis, and bony or granulomatous disease, are ruled out.

[Differential diagnosis of hypercalcemia--a retrospective study of 46 dogs]

The case records of 46 dogs with hypercalcemia were studied retrospectively. The most common cause of hypercalcemia was malignancy, of which the majority were diagnosed as having lymphosarcoma (LSA, n = 23). Interestingly only 15 had palpable lymphadenopathy. Other neoplasia were apocrine adenocarcinoma of the anal sac (n = 4), mammary adenocarcinoma (n = 2), anaplastic carcinoma (n = 1), and malignant histiocytosis (n = 1). Non-neoplastic reasons for hypercalcemia were hypoadrenocorticism (n = 5), acute renal failure (n = 2), chronic renal failure (n = 2), hypervitaminosis D (n = 1), and primary hyperparathyroidism (n = 1). In 4 cases no definitive diagnosis could be obtained. Moderate to marked hyperphosphatemia and azotemia was found in all dogs with primary renal failure and in 4 of 5 dogs with hypoadrenocorticism. In contrast only 4 of 31 dogs with neoplasia showed (mild) hyperphosphatemia and 20 showed mild to moderate azotemia. Elevated PTH levels were found in dogs with primary chronic renal failure and with primary hyperparathyroidism, but also in one dog with neoplasia. Low PTH concentrations were measured in the dog with hypervitaminosis D and in 8 cases with neoplasia. Additional three cases with neoplasia had values in the reference range.

CONCLUSIONS

1. The most common cause of hypercalcemia is LSA. Absence of palpable lymphadenopathy does not exclude LSA and further diagnostic steps may be necessary 2. The combination of moderate to marked hyperphosphatemia suggests primary renal failure or hypoadrenocorticism. 3. An elevated PTH level is consistent with primary hyperparathyroidism, but does not exclude other causes of hypercalcemia.

Feline chronic renal failure: calcium homeostasis in 80 cases diagnosed between 1992 and 1995

Eighty cats with chronic renal failure (CRF) were evaluated in a prospective study to investigate the prevalence and aetiopathogenesis of renal secondary hyperparathyroidism (RHPTH), using routine plasma biochemistry and assays of parathyroid hormone (PTH), blood ionised calcium and 1,25 dihydroxycholecalciferol (1,25[OH]2D3). Hyperparathyroidism was a frequent sequela of CRF, affecting 84 per cent of cats with CRF, the severity and prevalence of RHPTH increasing with the degree of renal dysfunction. Compared with an age-matched control population, plasma concentrations of phosphate and PTH were significantly higher and 1,25(OH)2D3 concentrations were significantly lower in the two groups of cats presenting with clinical signs of CRF. Significant ionised hypocalcaemia was present only in cats with end-stage renal failure. However, a number of cats were hyperparathyroid in the absence of abnormalities in the parameters of calcium homeostasis measured in this study. There was a significant correlation between plasma phosphate and PTH concentrations.

Primary hyperparathyroidism with osteodystrophia fibrosa of the facial bones in a pony

A 17-year-old pony mare was admitted for evaluation of progressive enlargement of the facial bones during the preceding 9 months. Laboratory testing revealed that the pony had hypercalcemia, hypophosphatemia, high urinary fractional excretion of phosphorus, and high serum concentration of intact parathyroid hormone (185.1 pmol/L; reference range, 0.25 to 2.0 pmol/L). On the basis of these findings, a diagnosis of primary hyperparathyroidism was made by ruling out nutritional secondary hyperparathyroidism, chronic renal disease, and pseudohyperparathyroidism resulting from neoplasia. Although primary hyperparathyroidism is best treated by surgical removal of the affected parathyroid gland, the owners declined surgical exploration of the neck in this pony. Because of the poor prognosis, the pony was euthanatized. A functional lesion of the parathyroid tissue was not located on necropsy or histologic examination. Difficulty localizing and grossly identifying parathyroid tissue in horses complicates definitive diagnosis and treatment of primary hyperparathyroidism.

Comparison of results of hormonal analysis of samples obtained from selected venous sites versus cervical ultrasonography for localizing parathyroid masses in dogs

OBJECTIVE

To compare a technique in which samples obtained from selected venous sites are analyzed for parathyroid hormone (PTH) concentration versus usefulness of cervical ultrasonography for localizing primary hyperparathyroidism (PHP) in dogs.

DESIGN

Prospective study.

ANIMALS

12 dogs with PHP.

PROCEDURE

For each dog, blood samples were collected from the left and right jugular veins and 1 cephalic vein for determination of serum PTH concentration. Ultrasonography of the neck was performed in each dog. Each dog underwent exploratory surgery of the neck. Abnormal appearing parathyroid tissue was removed. Dogs were included in the study if serum calcium concentration decreased within 12 hours after surgery, hypercalcemia completely resolved within 96 hours after surgery, and serum calcium concentration was maintained within the reference range for at least 6 months after surgery.

RESULTS

Serum PTH concentrations from the 3 veins were similar in 11 of 12 dogs with PHP. In 1 dog, the serum PTH concentration from the jugular vein ipsilateral to a parathyroid adenoma was greater than that from the contralateral jugular or cephalic vein. Ultrasonography correctly identified a parathyroid mass and its location in 10 of 11 dogs with a solitary abnormal parathyroid gland and in 1 dog in which both parathyroid glands were enlarged.

CLINICAL IMPLICATIONS

Surgeons may benefit from knowing the location of abnormal parathyroid tissue in dogs with PHP before surgical exploration. Ultrasonography has potential value for identifying and localizing abnormal parathyroid tissue, whereas sample collection from selected sites for PTH analysis is not likely to be helpful.

Primary hyperparathyroidism in two cats

Primary hyperparathyroidism (PHP) is an infrequently diagnosed disorder in cats. In this report the signs and symptoms of two cats with hypercalcaemia due to PHP are described, together with diagnostic approach, results of treatment, and immunohistochemical findings. A 9-year-old and a 13-year-old neutered male domestic shorthair cat were presented with signs of lethargy, anorexia, and vomiting. Both cats had persistent hypercalcaemia and normo- to hypophosphataemia. Cytological examination of a fine-needle aspiration biopsy sample of a palpable cervical mass revealed groups of benign glandular-epithelial cells in one cat. In the other cat no cervical mass was palpable. In this cat plasma parathyroid hormone (PTH) levels were measured repeatedly and these values exceeded the maximum reference value on two occasions. Following exclusion of other causes of hypercalcaemia both cats were subjected to neck surgery and in both a solitary parathyroid adenoma was removed. The adenomas contained an abundance of PTH, as demonstrated by immunohistochemical techniques. Plasma calcium and phosphate concentrations returned to within, reference ranges postoperatively. Recovery was uncomplicated and there were no signs of recurrence on follow-up examinations.

Use of technetium Tc 99m sestamibi for detection of a parathyroid adenoma in a dog with primary hyperparathyroidism

Double-phase parathyroid gland scintigraphy, using technetium Tc 99m sestamibi, correctly identified the existence and location of a parathyroid adenoma in a dog with primary hyperparathyroidism. The parathyroid adenoma was removed surgically 2 days after scintigraphy. An area of focal radionuclide uptake persisted in the region corresponding to the left external parathyroid gland in the delayed-phase image. Delayed-phase images from 3 healthy dogs and a dog with hypercalcemia of malignancy caused by lymphoma did not reveal an area of persistent radiotracer uptake. Double-phase parathyroid gland scintigraphy, using 99mTc-sestamibi, is a simple, rapid, noninvasive test, which can be used for detection and localization of parathyroid adenomas in hypercalcemic dogs. It also can help to differentiate these dogs from dogs with hypercalcemia of malignancy.

Nasal obstruction caused by nutritional osteodystrophia fibrosa in a group of Ethiopian horses

A severe, advanced case of nutritional osteodystrophia fibrosa is described in a 10-year-old gelding with primary upper respiratory obstruction and chronic weight loss, which was one of a group of similarly affected horses in Ethiopia. The diagnosis was based on the clinical signs, gross lesions, histopathology and management history. The affected bones had suffered severe mineral depletion.

Calcium oxalate urolithiasis in a cat with a functional parathyroid adenocarcinoma

A 9-year-old castrated male domestic shorthair cat with dysuria, anorexia, vomiting, and lethargy was admitted to the veterinary teaching hospital. A large, firm mass was palpable in the ventral cervical region. Hypercalcemia, azotemia, and nonregenerative anemia were evident on serum biochemical analysis and CBC, and multiple uroliths were detected by abdominal radiography. At necropsy, light microscopy of the ventral cervical mass revealed a parathyroid adenocarcinoma. Light microscopy of sections of the kidneys revealed multifocal, chronic, lymphocytic/plasmacytic, tubulointerstitial nephritis, as well as moderate multifocal acute tubular necrosis. On quantitative analysis, the uroliths were composed of calcium oxalate. Determination of serum calcium concentration is indicated in cats with calcium oxalate urolithiasis to aid in detection of primary hyperparathyroidism.

Diagnostic and therapeutic considerations in a hypercalcemic dog with multiple endocrine neoplasia

Hypercalcemia was found in a dog examined for episodic weakness and disorientation. A right adrenal mass identified on abdominal ultrasonographic examination was diagnosed as a pheochromocytoma based on increased 1231-metaiodobenzylguanidine uptake and characteristic histopathological features. Serum intact parathyroid hormone (iPTH), total serum calcium, and ionized serum calcium were increased prior to surgery. Although both total and ionized serum calcium concentrations decreased to within normal reference ranges following surgery through postoperative day 17, subsequent high concentrations with increased serum iPTH concentrations confirmed concurrent primary hyperparathyroidism. A right parathyroid tumor was suspected based on a technetium-99m-sestamibi (99mTc-sestamibi) scan.

Surgical therapy of the thyroid

The surgical treatment of thyroid cancer in the cat involves excision of one or both thyroid glands while sparing at least one parathyroid gland. The most common postoperative complication of bilateral thyroidectomy is transient hypocalcemia. Most feline thyroid tumors are benign, hyperfunctional thyroid adenomas. Surgical excision is usually curative. Canine thyroid cancer is most commonly malignant and nonfunctional. Successful surgical treatment of canine thyroid cancer depends on histologic and early diagnosis prior to metastasis or invasion of the cancer into adjacent structures within the neck.

Primary parathyroid gland hyperplasia in dogs: six cases (1982-1991)

Persistent hypercalcemia attributable to parathyroid gland hyperplasia was identified in 6 dogs with primary hyperparathyroidism. Clinical signs included polydipsia (n = 4), polyuria (n = 4), and signs caused by cystic calculi (n = 3). Abnormal clinical pathologic findings included hypercalcemia (mean, 13.6 mg/dl; range, 12.6 to 14.7 mg/dl; n = 6), hypophosphatemia (mean, 2.2 mg/dl; range, 1.4 to 2.9 mg/dl; n = 6), high serum alkaline phosphatase activity (mean, 222 IU/L; range, 161 to 286 IU/L; n = 3), and isosthenuria (mean, 1.012; range, 1.006 to 1.017; n = 6). Serum parathyroid hormone concentration was within the reference range or high (mean, 23 pmol/L; range, 7 to 119 pmol/L; reference range, 1.5 to 13 pmol/L) in all dogs. At surgery, the number of large parathyroid glands was variable, being limited to 1 gland in 3 dogs, 2 glands in 2 dogs, and 4 glands in 1 dog. All visibly large parathyroid glands were surgically removed from each dog. Serum calcium concentration decreased into or below the reference range within 72 hours of surgery in all dogs, confirming the diagnosis of primary parathyroid disease. Multiple nodules of adenomatous hyperplasia were identified in each dog. All 6 dogs were treated with vitamin D and calcium carbonate following surgery. The dog from which all 4 parathyroid glands were removed has remained eucalcemic for more than 1 year with vitamin D supplementation. Vitamin D and calcium administration was discontinued within 4 to 12 weeks of surgery in the remaining 5 dogs. These dogs remained eucalcemic without vitamin D supplementation.(ABSTRACT TRUNCATED AT 250 WORDS)

Nephrocalcinosis caused by hyperparathyroidism in progression of renal failure: treatment with calcitriol

Nephrocalcinosis is accepted to contribute to the progression of renal failure. We have reviewed evidence that nephrocalcinosis is caused directly by the excess parathyroid hormone produced in renal disease. Evidence that hyperparathyroidism in uremic patients results from calcitriol deficiency and the mechanisms by which this comes about have been discussed. We have shown that renal secondary hyperparathyroidism can be eliminated or substantially reduced without increasing blood calcium using a low-dosage regimen of calcitriol. Decreasing PTH concentrations to or near normal alleviates this hormone's toxicity to many organs, including the kidneys. Potential benefits for the uremic patient include an increase in the quality and length of life. Calcitriol treatment provides a powerful means to reduce PTH concentration in uremic patients that may not be achieved with other methods. Further prospective clinical studies of uremic dogs and cats are warranted to document preservation of renal function and histology during calcitriol treatments.

Primary hyperparathyroidism in cats: seven cases (1984-1989)

The medical records of 7 hypercalcemic cats with primary hyperparathyroidism were evaluated. Mean age was 12.9 years, with ages ranging from 8 to 15 years; 5 were female; 5 were Siamese, and 2 were of mixed breed. The most common clinical signs detected by owners were anorexia and lethargy. A cervical mass was palpable in 4 cats. Serum calcium concentrations were 11.1 to 22.8 mg/dl, with a mean of 15.8 mg/dl calculated from each cat's highest preoperative value. The serum phosphorus concentration was low in 2 cats, within reference limits in 4, and slightly high in 1 cat. The BUN concentration was greater than 60 mg/dl in 2 cats, 31 to 35 mg/dl in 2 cats, and less than 30 mg/dl in 3 cats. Abnormalities were detected in serum alanine transaminase, aspartate transaminase, and alkaline phosphatase activities from 2 or 3 cats. Parathormone (PTH) concentrations were measured in 2 cats before and after surgery. The preoperative PTH concentration was within reference limits in 1 cat and was high in 1 cat. The PTH concentrations were lower after surgery in both cats tested. A solitary parathyroid adenoma was surgically removed from 5 cats, bilateral parathyroid cystadenomas were surgically resected in 1 cat, and a parathyroid carcinoma was diagnosed at necropsy in 1 cat. None of the cats had clinical problems with hypocalcemia after surgery, although 2 cats developed hypocalcemia without tetany, one of which was controlled with oral administration of dihydrotachysterol and the other with oral administration of 1,25 dihydroxyvitamin D. All 5 of the cta that underwent removal of an adenoma were alive at least 240 days after surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Surgical management of collapsed pelvis in a jaguar

An immature jaguar was surgically treated for severe constipation caused by a narrow pelvic canal. This narrowing was attributed to nutritional secondary hyperparathyroidism. The ventral floor of the pelvis was widened by placing a piece of high density polyethylene between the 2 sides of the pubis after symphysiotomy and stabilizing the implant with orthopedic wires. This procedure provided stable fixation and permanent enlargement of the pelvic canal. The technique was easy to perform and could be used to treat pelvic collapse in other species.

Intact parathyroid hormone assay and total calcium concentration in the diagnosis of disorders of calcium metabolism in dogs

Serum samples from eight dogs with primary hyperparathyroidism, seven dogs with hypercalcemic lymphosarcoma (hypercalcemia of malignancy), and four dogs with primary hypoparathyroidism were submitted to the Animal Health Diagnostic Laboratory at Michigan State University for intact parathyroid hormone (PTH) assay. When compared with the adjusted total serum calcium concentration, the intact PTH concentration was consistent with the correct diagnosis in all cases. Two dogs with hypercalcemic lymphosarcoma were mildly azotemic. In both of these cases the intact PTH concentration was consistent with hypercalcemia of malignancy despite the presence of azotemia. These data support a significant role for intact serum PTH assay in the differential diagnosis of disorders of calcium metabolism.

Seizures as a manifestation of primary hyperparathyroidism in a dog

Hypercalcemia caused by primary hyperparathyroidism was believed to be responsible for seizures in a dog. A diagnostic evaluation showed no primary causes of seizures. After surgical excision of the adenomatous parathyroid gland, phenobarbital treatment was discontinued, without recurrence of seizures.