THE INSENSITIVITY OF 99mTc PERTECHNETATE FOR DETECTING METASTASES OF A FUNCTIONAL THYROID CARCINOMA IN A DOG

This report describes the use of ^99mtechnetium pertechnetate (^99mTcO₄⁻) and ¹³¹[for imaging of a metastatic thyroid carcinoma in a dog. The ¹³¹] imaging showed metastatic lesions undetected by the ^99mTcO₄⁻ imaging on 2 separate occasions. The possible mechanisms for the discrepancies between ¹³¹I and ^99mTcO₄⁻ imaging of thyroid carcinomas are discussed. The use of ¹³¹I for the imaging of functional thyroid carcinomas in the dog is recommended.     

TREATMENT OF DIFFERENTIATED THYROID CARCINOMA IN 7 DOGS UTILIZING 131I

Seven dogs with thyroid gland carcinoma were treated with ¹³¹I and hormone suppressive therapy either alone (3 dogs) or in combination with surgery (3 dogs) or ¹³⁷Cs teletherapy and chemotherapy (1 dog). Empirically chosen doses of 75 to 137 mCi of ¹³¹I were given orally (2 dogs) and intravenously (5 dogs). Adverse effects were limited to acute, transient bone marrow hypoplasia and pancytopenia. Nominal objective reduction in tumor volume or size and number of pulmonary metastases was observed in 4 dogs treated with ¹³¹I and thyroxine. Of these 4 dogs, 2 had stable disease for periods of 4 and 12 months while a third dog had stable disease for 27 months following two ¹³¹I treatments at 3 month intervals. The fourth dog had progressive disease. Two dogs with mediastinal metastases showed reduction in localization of ^99mTc pertechnetate and radioiodine following 2 and 3 treatments using ¹³¹I. It appears that relatively high doses of ¹³¹I can be used safely for the treatment of canine thyroid tumors and that further investigation can be justified to define its efficacy.     

131‐I therapy for Advanced, Unresectable Thyroid Tumors in Dogs

Introduction:  Greater than 50% of dogs with thyroid tumors present with surgically unresectable disease for which external beam radiotherapy has been reported to prolong survival. The success of ¹³¹I for control of thyroid tumors in cats and in humans suggests such therapy may also play a role in the management of canine thyroid cancer.
Methods:  Thirty‐nine dogs with WHO stage II/III (invasive or ectopic; n = 32) or IV (metastatic; n = 7) thyroid tumors were treated with ¹³¹I alone. Changes in thyroid function, ^99MTc‐pertechnetate (^99MTc) scintigraphic changes, and tumor response were recorded. Dogs with ventral cervical tumors were evaluated for feasibility of surgical resection following ¹³¹I.
Results:  Median overall survival was 839 days and 366 days for dogs with stage II/III and stage IV tumors, respectively. Thyroid hormone status, site and surgical resection were not associated with outcome in dogs with stage II/III tumors. Three dogs developed severe bone marrow suppression.
Conclusions:  These findings suggest ¹³¹I should be investigated more thoroughly in dogs with thyroid tumors not considered surgical candidates to more clearly characterize the indications for therapy and followup recommendations. ¹³¹I dosimetry in dogs with thyroid tumors remains problematic. Administration of ¹³¹I is currently based on empiric recommendations and, in general, the treatment is well tolerated although additional studies are indicated to optimize response and minimize toxicity.     

Canine Thyroid Carcinomas: Clinical Occurrence, Staging by Means of Scintiscans, and Therapy of 15 Cases

Tumor characteristics and degree of metastatic disease are outlined for 15 cases of canine thyroid carcinoma based on physical, laboratory, and radiographic examinations. Results of thyroid scintiscans using sodium pertechnetate are discussed in relation to clinical staging. Surgical resection was the primary therapy. Adjuvant therapy included thyroid replacement therapy, and ¹³¹I and ⁶⁰Co radiotherapy.     

TECHNETIUM-99M AND IODINE-131 THYROID SCINTIGRAPHY IN NORMAL AND RADIOTHYROIDECTOMIZED COCKATIELS (NYMPHICUS HOLLANDICUS)

Thyroid scintigraphy using sodium ^99mTechnetium pertechnetate (⁹⁹TcO₄-) was performed in normal and radiothyroidectomized cockatiels ( Nymphicus hollandicus ). ¹³¹I scintigraphy was performed in the course of ablating the thyroid glands. The thyroid glands in normal birds were clearly visualized, but were not individually resolvable. Thyroid glands were not visualized in thyroid-ablated birds. With ^99mTcO₄ scans, thyroid (or other region of interest)/body count density ratios were used for comparisons of normal and thyroid-ablated birds. Normal ^99mTcO₄- thyroid/body ratios (mean +/− SD) for the dorsal and lateral views were 1.83 +/− 0.31 and 1.70 +/− 0.34 respectively. Pertechnetate thyroid/body count density ratios decreased (to 0.93 -/−0.14 and 0.88 +/− 0.12 for dorsal and lateral views respectively) after thyroid ablation, while crop/body ratios increased. ^99mTcO₄- thyroid scintigraphy, therefore, was capable of detecting hypofunctional thyroid abnormalities in ¹³¹I radiothyroidectomized cockatiels.     

Retinol-Binding Protein in Serum and Urine of Hyperthyroid Cats before and after Treatment with Radioiodine

Background: Retinol-binding protein (RBP) is suggested as a clinically useful marker of renal function in cats.
Hypothesis: Serum and urinary RBP concentrations in hyperthyroid (HT) cats differ from those in healthy (H) cats; radioiodine (¹³¹I) treatment influences serum and urinary RBP concentrations in HT cats.
Animals: Ten HT and 8 H cats.
Methods: RBP concentration was evaluated in feline serum and urine samples from a prospective study.
Results: There was a significant ( P = .003) difference in the urinary RBP/creatinine (uRBP/c) ratios of H (−) and untreated HT (1.4 ± 1.5 × 10⁻² μg/mg) cats. Serum total thyroxine concentration (1.8 ± 1.9 μg/dL, 24 weeks) and uRBP/c (0.6 ± 1.0 × 10⁻² μg/mg, 24 weeks) decreased significantly ( P < .001) in HT cats at all time points after treatment with ¹³¹I, and these variables were significantly correlated with one another ( r = 0.42, P = .007). Serum RBP concentrations from HT cats (199 ± 86 μg/L) did not differ significantly ( P = .98) from those of H cats (174 ± 60) and did not change after treatment with ¹³¹I (182 ± 124 μg/L, P = .80).
Conclusion and Clinical Importance: The presence of urinary RBP in HT cats is a potential marker of tubular dysfunction that is correlated to thyroid status, although it is independent of circulating RBP concentrations. The decreased uRBP/c combined with the absence of changes in serum RBP after treatment suggests that the suspected tubular dysfunction was partly reversible with treatment of ¹³¹I.     

QUALITATIVE AND QUANTITATIVE THYROID IMAGING IN FELINE HYPERTHYROIDISM USING TECHNETIUM-99M AS PERTECHNETATE

Thyroid imaging using technetium-99m as pertechnetate (^99mTcO₄) was carried out in five healthy, euthyroid and 37 hyperthyroid cats using both pinhole and parallel-hole collimators. Images of greater resolution, necessary to distinguish bilateral lobe involvement, were obtained using the pinhole collimator. Per cent thyriod ^99mTcO₄ - uptake was calculated in each cat and was significanly (P < 0.001) higher in hyperthyroid compared with euthyroid cats. In the hyperthyroid cats, per cent thyroid uptake was significantly correlated with serum total thyroxine (T4) and triiodothyronine (T3) Concentrations. Per cent thyroid ^99mTcO₄ - uptake is increased in feline hyperthyrodism and may be calculated using a pinhole collimator alone at the time of qalitative assessment of the extent of thyroid tissue involvement.     

Systemic Toxicity Associated With Doxorubicin Administration in Cats

The systemic toxicity of doxorubicin, 30 mg/m² body surface area (BSA) every 21 days to a cumulative dose of 300 mg/m², was evaluated in six cats. Appetite, body weight, and the presence of vomiting and/or diarrhea were monitored throughout the study. Renal function was monitored by measuring serum blood urea nitrogen (BUN) and creatinine concentrations, urine specific gravity, and creatinine clearance before each treatment. Electrocardiograms and echocardiograms were also done before each treatment. The cats were killed 3 weeks after the last treatment, and complete necropsies were performed. Partial or complete anorexia occurred in all cats with significant weight loss occurring after a cumulative doxorubicin dose of 150 mg/m² BSA. Mild vomiting and diarrhea that required no treatment also occurred sporadically in all cats. Echocardiographic changes consistent with doxorubicin-induced cardiomyopa-thy occurred in four cats after cumulative doses of 170 to 240 mg/m² BSA. Clinical heart disease and electrocardiographic changes were not observed. Subsequent histological examination revealed myocyte vacuolization and myocytolysis in all six hearts. Renal dysfunction, characterized by increasing azotemia with progressively more dilute urine, was detected in two cats. Mean creatinine clearance values also decreased significantly throughout the study. At necropsy, all cats had histological evidence of renal disease. (Journal of Veterinary Internal Medicine 1993; 7:309–317. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Plasma von Willebrand Factor Antigen Concentration and Buccal Mucosal Bleeding Time in Dogs With Experimental Hypothyroidism

This study was undertaken to investigate the effects of hypothyroidism on buccal mucosal bleeding time and von Willebrand factor antigen (vWf:Ag) concentrations. Hypothyroidism was induced in 8 adult dogs by administration of iodine 131. Four healthy dogs acted as controls. Measurement of plasma vWf:Ag and serum thyroxine and triiodothy-ronine concentrations, and buccal mucosal bleeding time were made before induction of hypothyroidism, for 23 weeks after ¹³¹I administration, and during 5 weeks of levothyroxine supplementation. No significant changes in buccal mucosal bleeding times were noted during the study. After an insignificant increase in vWfAg concentration in hypothyroid dogs, levothyroxine treatment was associated with a significant decrease in vWf:Ag concentration in hypothyroid dogs when compared with controls. Results of this study suggest that hypothyroidism does not induce acquired von Willebrand's disease or significant defects in primary hemo-stasis. J Vet Intern Med 1996;10:60–64. Copyright © 1996 by the American College of Veterinary Internal Medicine .     

Urinary Indices of Horses After Intravenous Administration of Crystalloid Solutions

Saline or glucose solution was infused for approximately 4 hours into six healthy mares in two separate experiments to determine the effect of infusion of crystalloid solutions on fractional excretion (FE) of sodium (Na), chloride (Cl), potassium (K), and phosphorus (P), ratio of urinary creatinine to serum creatinine (U_Cr/S_Cr), and ratio of urinary osmolality to serum osmolality (U_osm/S_osm). After intravenous infusion of either saline or glucose solution, FE_Na, FE_Cl and FE_P were significantly increased, whereas U_Cr/S_Cr and U_osm/S_osm were significantly decreased. In addition, FE_K was significantly increased after infusion of glucose solution. It was concluded that urinary indices were altered by intravenous infusion of crystalloid solutions in healthy mares and that fluid therapy may interfere with the use of these indices for diagnostic purposes. (Journal of Veterinary Internal Medicine 1993; 7:241–246. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Hypophosphatemia and Hemolytic Anemia Associated With Diabetes Mellitus and Hepatic Lipidosis in Cats

Hypophosphatemia associated with hemolytic anemia was diagnosed in five cats with diabetes mellitus and in one cat with idiopathic hepatic lipidosis. The hematocrit began decreasing within 24 to 48 hours after documented hypophosphatemia in each case. The anemia resolved in all five surviving cats. Because of the temporal relationship and lack of other detectable causes, hemolytic anemia was presumed to be caused by hypophosphatemia. There were increased Heinz bodies in three of six hypophosphate-mic cats during episodes of hemolysis. Intravenous potassium phosphate administration corrected the hypophosphatemia in four of five cats. The effective dosages of intravenous phosphate ranged from 0.011 to 0.017 mmol of phosphate/kg/h for 6 to 12 hours. Hypocalcemia (5.4 to 8.7 mg/dL) occurred in four of five cats treated with intravenous phosphate; however, only one cat developed clinical signs attributable to hypocalcemia. Based on this retrospective study, we recommend monitoring serum phosphorus concentration every 6 to 12 hours in cats likely to become hypophosphatemic. Treatment of hypophosphatemia in cats is warranted because of the apparent increased susceptibility of cats to hypophosphatemia-induced hemolysis. Cats with severe hypophosphatemia (≤1.5 mg/dL) should be given oral or parenteral phosphate if contraindications do not exist. (Journal of Veterinary Internal Medicine 1993; 7:266–271. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Evaluation of a Whole Blood Glutaraldehyde Coagulation Test for the Detection of Failure of Passive Transfer in Calves

The accuracy of a commercially available whole blood glutaraldehyde clot test in the detection of failure of passive transfer (serum immunoglobulin [Ig]G₁ < 1,000 mg/dL) in neonatal calves was evaluated. Serum samples were obtained from 242 calves ranging in age from 1 to 8 days, and comparisons were made with serum lgG₁ concentrations determined by radial immunodiffusion. Both the sensitivity and specificity of the currently marketed whole blood glutaraldehyde clot test are inadequate for routine diagnostic use. Concerns regarding test sensitivity are the most problematic. Sensitivity varied from 0.41 to 0.00, depending on the choice of test endpoint. Specificity varied from 0.85 to 1.00, depending on the choice of test endpoint. Regression analysis demonstrated that the relationship between serum lgG₁ concentration and the glutaraldehyde clot results, although significant (P< .10), was of negligible biological relevance ( r ² = .034). J Vet Intern Med 1996; 10:82–84. Copyright © 1996 by the American College of Veterinary Internal Medicine .     

Spontaneous Adult-Onset Hypothyroidism in a Cat

Spontaneous adult-onset hypothyroidism, confirmed by a thyroid-stimulating hormone stimulation test, thyroid biopsy, and response to replacement therapy, is described in a female cat. Clinical signs consisted of profound apathy, hypothermia, poor hair growth, severe seborrhea sicca, and a puffy face. Cutaneous histological changes consisted of epidermal and follicular hyperkeratosis, teloginization of hairs, and dermal mucin deposition. There was no adnexal atrophy. Lymphocytic thyroiditis, equivalent to Hashimoto's thyroiditis, was shown by thyroid biopsy. Clinical signs rapidly responded to thyroxine replacement therapy. Glucose intolerance was coexistent with the hypothyroidism, but was not dramatically influenced by thyroxine therapy and probably was an independently occurring endocrinopathy. (Journal of Veterinary Internal Medicine 1993; 7:272–276. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Concentrations of thyroid hormones and iodothyronine binding proteins in serum of the koala (Phascolarctos cinereus)

Objective To examine circulating total and free thyroid hormone (T₃ and T₄) concentrations, determine serum iodothyronine binding characteristics and estimate thyroid stimulating hormone (TSH) activity in sera of coastal and inland koalas.
Design A prospective study.
Procedure Koala serum T₃ and T₄ were measured by radioimmunoassay. T₄ binding parameters were determined by radioligand binding and electrophoresis. Koala TSH values were determined by bioassay.
Results Mean total T₄ concentrations were 3.2 ± 2.1 nM although values were significantly higher in inland-dwelling females in comparison to coastal-dwelling males. Free T₄ was 3.3 ± 2.1 pM. Total and free T₃ were 0.4 ± 0.2 nM and 1.4 ± 0.9 pM respectively, although these values were at the lower end of the assay detection limit and should be viewed with reservation. Electrophoresis of [¹²⁵I]-T₄-labelled serum revealed only two proteins of electrophoretic mobility similar to human transthyretin (TTR) and albumin. Scatchard analysis of T₄ binding to serum gave a curvilinear plot, which could be resolved into two binding sites with affinities identical to that of TTR and albumin but both of low concentration. The bioactivity of the TSH present in the sera was measured using a cell line (JP09) transfected with the human TSH receptor. The mean level of stimulation found in the sera corresponded to a bovine TSH activity of less than 10 mU/L.
Conclusion These results suggest that the serum concentrations of free and total thyroid hormones in koalas are low compared to other marsupials and very low compared to eutherian mammals. The mechanism of maintenance of euthyroidism in this species remains to be determined.     

Quantitative Aspects of Thyroid Scintigraphy With Pertechnetate (99mTcO4) in Cats

Thyroidal ^99mTcO₄(pertechnetate) uptake percentages were determined in unanesthetized euthyroid (n = 13) and hyperthyroid (n = 18) cats. Maximal uptakes were observed 60 minutes after IV injection of the radionuclide and ranged from 0.3 to 3.9% of the dose in euthyroid cats (median 2.23%) and from 5.2% to 23.9% of the dose in hyperthyroid cats (median 14.8%) ( P < .05). There were no overlaps in pertechnetate uptake percentages during any of the intervals evaluated. It is concluded that the optimal time for visualization of the thyroid by ^99mTcO₄-scanning is 60 minutes after IV injection of the radionuclide. Calculation of the percentage uptake is of additional diagnostic value.     

Bronchointerstitial Pneumonia and Respiratory Distress in Young Horses: Clinical, Clinicopathologic, Radiographic, and Pathological Findings in 23 Cases (1984–1989)

Twenty-three foals, between 1 and 7 months old, with signs of acute respiratory distress, were examined at the Veterinary Medical Teaching Hospital (VMTH), University of California, Davis, between 1984 and 1989. Characteristic features included sudden onset of severe respiratory distress and tachypnea, cyanosis unresponsive to nasal oxygen, pyrexia, hypoxemia, hypercapneic respiratory acidosis, poor response to treatment, and histopathologic lesions of bronchiolitis and bronchointerstitial pneumonia. Seven of the 23 foals were normal before the onset of respiratory distress, 3 foals were found dead, aqd 13 foals were being treated for respiratory tract infections at the time of presentation. Laboratory data obtained for 13 horses showed increased plasma fibrinogen concentration (630.7 ±193 mg/dL), leukocy-tosis (18,607 ± 7,784/μL), and neutrophilia (13,737 ± 8,211/μL). Thoracic radiographs showed a diffuse increase in interstitial and bronchointerstitial pulmonary opacity and, in 5 foals, an alveolar pulmonary pattern of increased density was also seen. In 3 foals heavy interstitial infiltration proceeded to a coalescing nodular radiographic appearance. Microbiological culture of tracheobronchial aspirates (TBA) from 9 foals yielded bacterial growth, but no one bacterial species was consistently isolated. Microbiological culture of postmortem specimens of the lung from 6 foals yielded growth of bacteria that included Escherichia coli, Enterobacter spp., Proteus mirabilis, Klebsiella pneumonias, Rhodococcus equi, or β-hemolytic Streptococcus spp. Tracheobronchial aspirates from 4 foals and lung samples collected from a further 4 foals at necropsy yielded no bacterial growth. Cultures were not taken from two foals premortem or postmortem. Virologic examination of TBA, lung tissue, or pooled organ tissue from 12 foals was negative. Viral culture of TBA from 1 foal showed cytopathic effects and positive immunoflu-orescence for equine herpes virus type II (EHV-II). In addition to the 3 foals that were found dead, 11 foals died or were euthanatized. Pathologic lesions were limited to the lungs in 50% of the foals; the remainder also had bowel lesions suggestive of hypoxic injury. The predominant histopathologic pulmonary lesions included bronchiolitis, bronchiolar and alveolar epithelial hyperplasia, and necrosis. Many bronchioles were filled with mucoid and fibrinocellular exudate. The peribronchiolar interstitium and adjacent alveolar spaces were also infiltrated with inflammatory cells and contained proteinaceous edema fluid. Type II cell hyperplasia and hyaline membrane formation were observed in the majority of foals and in 2 foals alveolar multinucleate giant cells were also present. Nine of 13 foals (69%) on which treatment was attempted at the VMTH survived after aggressive medical care that included external thermoregulatory control, oxygen by nasal insufflation, antimicrobial drugs, bronchodilating agents, nonsteroidal anti-inflammatory drugs, and corticosteroids. Persistent radiographic evidence of increased interstitial density was noted up to 24 months after initial presentation, and one horse remained exercise intolerant for at least 15 months after discharge. The exact etiopathogenesis of this disorder and long-term sequalae in the survivors have yet to be fully determined. However, it is likely that a number of different insults rather than a single agent may initiate the pulmonary damage that leads to severe interstitial pneumonia and subsequent acute respiratory distress or apparent sudden death in foals. (Journal of Veterinary Internal Medicine 1993; 7:277–288. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Tidal Breathing Flow-Volume Loops in Healthy and Bronchitic Cats

Tidal breathing flow-volume loops (TBFVL) were obtained from 19 healthy cats and 7 cats with chronic bronchial disease. Peak inspiratory flow (PIF) occurred late in the inspiratory cycle and was preceded by a gradual but more linear increase in the flow rate. Peak expiratory flow (PEF) occurred early during expiration and was followed by a curvilinear decrease in flow to a point near the end of expiration where flow ceased. The loops obtained were generally reproducible. The mean coefficient of variation (CV) for TBFVL indices of healthy cats ranged from 5.6% to 21.9%. Loop indices from cats with chronic bronchial disease had a mean CV between 6.6% and 28.4%. Significant differences were noted in the bronchitic cats' TBFVLs, including an increased ratio of expiratory time to inspiratory time, lower expiratory flow rates, decreased area under total and peak expiratory flow curves, and decreased tidal breathing expiratory volumes (TBEV) at 0.1 and 0.5 seconds. Selected TBFVL indices were also significantly reduced. TBFVL evaluation in the cat is easy to perform, is reproducible, and has allowed for the detection of changes during tidal breathing in cats with histories and physical findings of chronic lower airway disease. (Journal of Veterinary Internal Medicine 1993; 7:388–393. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Clinical, morphological and immunohistochemical characterization of cutaneous lymphocytosis in 23 cats

Abstract   Clinical, morphological and immunohistochemical features of cutaneous lymphocytosis, an uncommon disease histologically resembling well-differentiated malignant lymphoma, were characterized in 23 cats. Clinical outcome was correlated with histomorphology and immunophenotype in an attempt to predict benign vs. malignant behaviour. The disease mainly affected older cats. Lesions were solitary in 61% of cats and often characterized by alopecia (73.9%), as well as erythema, scaling and ulceration. The lateral thorax was most commonly affected (43.5%). Pruritus was frequent (65.2%). Systemic signs included anorexia and weight loss. Morphologically, lesions were characterized by dermal infiltrations of well-differentiated CD3⁺ T-cells (100%) and aggregates of CD79⁺ B-cells (64.3%). Cutaneous lymphocytosis is slowly progressive and relatively benign, although in some cats systemic signs led to euthanasia. Four of 12 euthanized cats and one live cat also had lymphoid infiltrates in internal organs. Unfortunately, we were unable to predict clinical outcome by histological and immunohistochemical evaluations of skin lesions.     

Acute Pancreatitis in Cats With Hepatic Lipidosis

The purpose of this study was to characterize the incidence, clinical features, and prognosis of acute pancreatitis in cats with hepatic lipidosis. Of 13 cats histologically diagnosed with hepatic lipidosis between July 1988, and November 1989,5 (38%) were also histologically diagnosed with acute pancreatitis. In cats with hepatic lipidosis alone, the signalment, history, physical examination, and clinicopatho-logic findings were generally indistinguishable from those of cats with concurrent acute pancreatitis except that cats with acute pancreatitis were more likely to be cachectic and to have coagulation abnormalities. Hepatomegaly was seen on abdominal radiographs in both groups. Of the 5 cats with concurrent acute pancreatitis, abdominal ultrasonography detected 1 cat with a hypoechoic pancreas and 5 with peritoneal effusion; those abnormalities were not seen in cats without concurrent acute pancreatitis. Cats with concurrent acute pancreatitis had only a 20% recovery rate, compared with a 50% recovery rate in cats with hepatic lipidosis alone. We conclude that cats with hepatic lipidosis should be rigorously evaluated for concurrent acute pancreatitis because of 1) the rate of disease coincidence, 2) the inability of signalment, history, physical examination, and clinicopathologic findings to adequately distinguish between hepatic lipidosis and acute pancreatitis, 3) the worse prognosis associated with concurrent acute pancreatitis, and 4) the opposing nutritional strategies for hepatic lipidosis and acute pancreatitis. (Journal of Veterinary Internal Medicine 1993; 7:205–209. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Evidence for Genetic Involvement in Feline Dilated Cardiomyopathy

Quantitative genetic evaluation of clinical dilated cardiomyopathy (DCM) was conducted in a large cattery with known history. Data showed that clinically affected cats were significantly more interrelated than randomly chosen case-control populations from the same colony. The results of this study suggest that quantitative inheritance, either interactive with or independent of nutrition or presently unknown factors, is involved in feline dilated cardiomyopathy. (Journal of Veterinary Internal Medicine 1993; 7:383–387. Copyright © 1993 by the American College of Veterinary Internal Medicine.)