MAGNETIC RESONANCE IMAGING OF THE NORMAL AND DISEASED FELINE MIDDLE EAR

The magnetic resonance imaging appearance of the feline middle ear is described in three healthy cats and in five cats with middle ear disease. Owing to the good spatial resolution, multiplanar slice orientation as well as display high contrast resolution of soft tissue, in particular fluids, MR imaging was helpful prior to surgery. It is superior to radiography which failed to allow identification of the abnormality in two of our five cats. MR imaging for middle ear disease should include dorsal and transverse plane images using T1- and T2-weighted sequences. In the presence of a mass within the bulla or the external ear canal application of contrast medium is helpful.     

EVALUATION OF FATTY INFILTRATION OF THE LIVER IN DAIRY CATTLE THROUGH DIGITAL ANALYSIS OF HEPATIC ULTRASONOGRAMS

Ultrasonography of the liver of 49 Holstein-Friesian cows was performed, liver specimens were taken, examined microscopically and the fatty occupying rate (FOR) was calculated. Echoes from the hepatic B-mode ultrasonograms were quantified as histogram mean (Emean) and histogram mode (Emode) of echo amplitudes within various areas at a depth of 1–9 cm from the hepatic surface. Of the 49 animals, 26 had a normal liver and 23 had fatty infiltration of the liver, diagnosed through histopathological examination. Fatty occupying rate ranged from 1.7 to 64.5%, with 11 animals having 1–15% FOR (mild fatty infiltration), 6 having 15.1–30% FOR (moderate fatty infiltration) and 6 having > 30% FOR (severe fatty infiltration). At 1 cm, severe fatty infiltration had higher Emean and Emode than normal liver (p < 0.05). At 7 cm and 9 cm, moderate and severe fatty infiltration had lower Emeans and Emodes than normal liver (p < 0.001). The results suggest that digital analysis of hepatic ultrasonogram can be useful in the evaluation of the degree of fatty infiltration of the liver in dairy cattle.     

HYPOTHYROIDISM IN A DOG AFTER SURGERY AND RADIATION THERAPY FOR A FUNCTIONAL THYROID ADENOCARCINOMA

Hypothyroidism was diagnosed in a dog which had undergone unilateral thyroid lobectomy and external beam irradiation (48 Gy in 3 Gy fractions) for a functional cystic thyroid adenocarcinoma. Hypothyroidism became biochemically apparent within 4 months of completion of radiation therapy, and clinically apparent within 7 months. Clinical signs resolved after thyroid hormone supplementation. The potential for alterations in thyroid function should be considered in any animal undergoing radiation therapy in which the thyroid gland is included in the radiation field. This potential may be greater if surgery and radiation are combined.     

A BOOST TECHNIQUE FOR IRRADIATION OF MALIGNANT CANINE NASAL TUMORS

Eighteen dogs with malignant nasal cavity tumors were treated with radiation therapy, including a boost technique. Three 3:0 Gy boost doses were added to a treatment protocol consisting of sixteen 3.0 Gy daily fractions, bringing the total dose to 57 Gy. This boost technique was implemented without an associated increase in overall treatment time by giving the boost doses on a twice-a-day basis. Boost doses were given during the first half of the radiation therapy period. The treatment was completed as planned in 16 of the 18 dogs; two dogs received lower doses (51 and 54 Gy). Median survival was 177 days, poorer than in some other reported studies of nasal tumor irradiation. Acute effects were unacceptable, with 11 of the 18 dogs developing severe mucositis, desquamation, edema, swelling, and pruritus. The extensive nature of the acute reactions compromised assessment of the effect of the increased radiation dose on the tumor. Although there is justification for assessing more aggressive radiation protocols in canine nasal tumor patients, total doses approximating 60 Gy can not be given as described because of the inability of acutely responding normal tissues to compensate.     

SUBCLINICAL CT ABNORMALITIES IN THE LUMBOSACRAL SPINE OF OLDER LARGE-BREED DOGS

Computed tomography (CT) of the L5-S3 vertebral levels was performed in six, large-breed dogs presented for problems unrelated to the lumbosacral spine. All dogs were asymptomatic for lumbosacral stenosis on neurologic examination. Breeds included German Shepherd, Golden Retriever, Boxermix and Belgian Malinois. Ages ranged from 5-12 years. Five out of six dogs exhibited CT abnormalities. Among the 18 disc levels examined, the most common findings were idiopathic stenosis, loss of vertebral canal epidural fat, and nerve tissue displacement. Less common abnormalities were vertebral canal or foraminal bone proliferation, loss of intervertebral foramen fat, vertebral canal disc bulging, degenerative articular process joint disease, transitional vertebra, dural ossification, foraminal disc bulging, Schmorl's nodes, calcified extruded disc fragment, and sacroiliac joint osteophytes. Vertebral subluxation was absent in all dogs. Findings indicate that some lumbosacral CT abnormalities may be clinically insignificant, especially in older dogs.