Radiographic changes in Thoroughbred yearlings. Part 1: Prevalence at the time of the yearling sales.

REASONS FOR PERFORMING STUDY: Radiography in presale examinations of TB yearlings has become standard practice in recent years. OBJECTIVES: To describe the prevalence and distribution of radiographic changes in the fetlocks, carpi, tarsi, stifles and fore feet of Thoroughbred yearlings in central Kentucky when these joints were examined as part of routine pre- and post sale evaluations. METHODS: Horses subjected to radiographs included the fore (n = 1127) and hind (n = 1102) fetlocks, carpi (n = 1130), tarsi (n = 1101), stifles (n = 660) and fore feet (n = 300). Radiographic changes were categorised by location and type of change present (e.g. lucency, fragment) for each series. RESULTS: In the fore fetlocks 1.6% had fragmentation of the proximal dorsal first phalanx and 0.5% fragmentation of the proximal palmar aspect. In the hind fetlocks 5.9% had fragmentation at the plantar aspect and 3.3% fragmentation dorsally. Lucencies, fragments or loose bodies were detected at the dorsal aspect of the distal third metacarpus in 2.8% and, at the same location on the third metatarsus, 3.2%. Most yearlings (98%) had vascular channels in the proximal sesamoid bones and irregular vascular channels (> 2 mm wide or with nonparallel sides) were more common (79%) than regular vascular channels (56%). The intermediate ridge of the distal tibia was the most common location for fragmentation in the tarsus (4.4%). CONCLUSIONS: While some radiographic changes, e.g. vascular channels in proximal sesamoid bones, are very common in Thoroughbred yearlings, others, e.g. fragmentation or subchondral lucency within joints are quite rare usually affecting less than 5% of the population. POTENTIAL RELEVANCE: Veterinarians should expect to find radiographic changes in Thoroughbreds presented for examination prior to the yearling sales. The rarity of some changes thought to affect soundness or racing performance will make further invesigation of these conditions in horses without clinical signs more difficult.

Radiographic changes in Thoroughbred yearlings. Part 2: Associations with racing performance.

REASONS FOR PERFORMING STUDY: Although the radiographic examination of yearlings has become commonplace at some large Thoroughbred sales, there are few data to support the decisions facing veterinarians who are asked to evaluate future racing potential. OBJECTIVES: To identify radiographic changes in the fetlocks, proximal sesamoid bones, carpi, tarsi, stifles and fore feet of Thoroughbred yearlings associated with future racing performance during ages 2 and 3 years. METHODS: Radiographs from routine pre- and post sale examinations of 1162 yearlings were used to identify individual radiographic changes in sale yearlings. Starting a race, the percent of starts placed, money earned and earnings per start were used to assess racing performanceand examined for associations with the radiographic changes observed. RESULTS: Overall 946 (81%) yearlings started at least one race during ages 2 or 3 years. Fourteen of 24 (58%) yearlings with moderate or extreme palmar supracondylar lysis of the third metacarpus, 8 of 14 (57%) of those with enthesophyte formation on the proximal sesamoid bones and 19 of 30 (63%) of those with dorsal medial intercarpal joint disease started a race. The odds of starting a race when age 2 or 3 years were 3 times lower for yearlings with these changes (P < 0.01) compared with yearlings that did not have these changes. Twenty-five of 36 (69%) yearlings with proximal dorsal fragmentation of the first phalanx in the hind fetlock started a race and these yearlings were also less likely (OR = 0.51, P = 0.07) to start a race. Yearlings with enthesophyte formation on hind proximal sesamoid bones placed in a smaller percentage of starts (16%, P = 0.01) earned less money (987 US dollars, P = 0.02) and had lower earnings per start (252 US dollars, P = 0.03) compared to starters without this change. CONCLUSIONS: Although many of the changes observed on radiographs of sale yearlings do not appear to influence future racing performance, some are associated with reduced performance. POTENTIAL RELEVANCE: The results of this study are best applied in parallel with the clinical impressions of veterinarians experienced in examining radiographs of sale yearlings. Some findings support those established in the literature as incidental findings and others suggest new areas for concern not previously reported as a problem in Thoroughbred sale yearlings.

Spontaneous echocardiographic contrast in the thoroughbred: high prevalence in racehorses and a characteristic abnormality in bleeders.

Spontaneous echocardiographic contrast is the term used by ultrasonographers to describe particulate material visible in intracardiac blood by ultrasound. The purpose of the present study was to determine the prevalence of spontaneous contrast in a farm population of Thoroughbreds and in the farm's racehorses. The results showed that spontaneous echocardiographic contrast is common in Thoroughbreds, and that the prevalence of contrast is affected by age, male gender, racing and pregnancy. The amount of right-sided cardiac contrast was quantitated by videodensitometry and was increased in horses with a history of exercise-induced pulmonary haemorrhage, in comparison with racehorses without a history of bleeding. Since circulating platelet aggregates are known to produce pulmonary haemorrhage in experimental animals and their presence has been associated with echocardiographic contrast, additional studies evaluating platelet aggregates as the aetiologic agent for exercise-induced pulmonary haemorrhage are warranted.

Cranial thoracic masses in the horse: a sequel to pleuropneumonia.

The formation of cranial thoracic masses (CTM) as a sequel to infectious pleuropneumonia is described. Using ultrasound, masses were diagnosed subjectively as abscesses or loculations. Eight of 99 cases with pleuropneumonia had CTM. Clinical signs associated with the presence of a CTM included increased heart rate, jugular distention, forelimb 'pointing' and caudal displacement of the heart. Techniques used for diagnostic ultrasonographic examination of the cranial thorax are described. Five of the eight horses with CTM responded to conservative medical management; the other three required percutaneous drainage of the mass to relieve worsening signs of cardiac decompensation. Improvements in cardiovascular parameters were evident within 12 h of drainage. The indications for and limitations of invasive drainage of cranial thoracic masses are discussed.

Clinical experience with quantitative analysis of superficial digital flexor tendon injuries in Thoroughbred and Standardbred racehorses.

A method to quantitate as well as to document SDFT pathology has been described. This report indicates that computer-assisted evaluation of SDFT damage can improve the accuracy of prognosis in clinical practice. It would appear that a 3.8 severity rating is a limit past which prognosis for successful racing starts to worsen rapidly.

Percutaneous nephrostomy in short-term management of ureterolithiasis and renal dysfunction in a filly.

Percutaneous nephrostomy was used to provide urine output in a 3-year-old Thoroughbred filly with azotemia and obstructive ureterolithiasis. Previous left ureteral surgery had failed to provide clinical improvement, and the filly became more azotemic. Nephrostomy was performed in the standing patient, with ultrasonographic guidance and local anesthesia. Continuing IV fluid therapy and diuresis through the nephrostomy tube resulted in a decrease in clinical signs of azotemia. However, the filly developed a cecal impaction, which ruptured during surgery because of colic, and was euthanatized.

Inheritance of diabetes mellitus in Keeshond dogs.

The genetic aspects of inherited, insulin-dependent diabetes mellitus of Keeshond dogs were studied retrospectively and in a prospective mating program. The symbol dm was used to designate the gene that causes hypoplasia of the islets of Langerhans. The retrospective study disclosed 4 diabetic dogs; prospective outcross, backcross, and inbred matings disclosed 49 diabetic dogs. Outcrossing demonstrated that the diabetic phenotype was displayed readily against a genetic background of a breed other than the Keeshond. In dogs with the dm/dm genotype, onset of diabetes was most frequent before the dog was 6 months old, but did occur in some older dogs. The dm genotype was best described as autosomal recessive.

Diseases of the liver.

The ability to image the liver in horses can add valuable diagnostic information or aid in guided biopsy procedures. Anytime the size, shape, position, and texture of the liver can be determined, additional information about the horse's condition is gained. Conditions such as cholelithiasis, neoplasia, fibrosis can be detected ultrasonographically.

Diagnostic ultrasonography of equine limbs.

In our 3 years of clinical experience, we have found that diagnostic ultrasound provides the veterinarian with a valuable diagnostic tool. It allows the clinician to quantify morphologic change that has occurred as a result of soft-tissue injuries, even when the clinical findings are ambiguous or insufficient. In cases in which aggressive postinjury therapy has been instituted prior to presentation, diagnostic ultrasound is often the only noninvasive method that can ascertain the extent of the horse's injury. Diagnostic ultrasound provides the technology to detect injuries before they become permanently debilitating, because lesions as small as 1 mm in diameter can be detected. Prior to diagnostic ultrasound, the severity of many injuries was underestimated. In such cases, if the horse responded favorably to symptomatic therapy, the client would resume training. The result was often debilitation. Diagnostic ultrasound also enables the clinician to demonstrate visually to the client the location, size, and extent of lesions in the limb. One of the more gratifying effects of a sonographic study is the client's acceptance of the presence and extent of the injury after visualizing it. We have found that the old adage "a picture is worth a thousand words" is generally the rule in obtaining the proper course of therapy for the horse. The ability to make hard copies of sonograms enables the clinician to morphologically evaluate the rate of healing. He can accurately determine the effectiveness of a therapeutic regimen and ascertain when optimal healing has occurred. Diagnostic ultrasound can provide the researcher with an invaluable tool to document and quantify soft-tissue disease. We anticipate that, in the future, the sonographic appearance of recovered tissues will be correlated with new data on the healing process and the effectiveness of various therapies. The material presented above has covered the value of diagnostic ultrasound in major clinical situations related to equine lameness. Other applications, the discussion of which is beyond the scope of this article, include evaluation of the pastern for injuries to the SDF, DDF, and oblique sesamoidean ligament, and evaluation of the navicular bursae. Examination of muscles for hematomas, abscessations, and tears has also been accomplished ultrasonographically. Diagnostic ultrasound has facilitated study of the trochanteric and bicipital bursae, blood flow through arteries, and structures above the carpus and hock. Obviously, the clinical potential of diagnostic ultrasound is limitless.(ABSTRACT TRUNCATED AT 400 WORDS)

General considerations for ultrasound examinations.

Patient preparation and restraint, instrumentation, and methods of retaining records of ultrasound images are discussed.

Diseases of the heart.

Diagnostic ultrasound has allowed significant findings to be made in the investigation of cardiac disease in the horse. Because of the limited value of thoracic radiography in the adult horse with cardiac disease, ultrasound is the method of choice to document chamber enlargement, pericardial effusion, valvular abnormalities, and decreased contractility of the myocardium. The apparent changes in the flow characteristics and suspicion of abnormality in the right heart of racehorses need further investigation to fully document the etiopathogenesis of spontaneous contrast.

Diseases of the thorax.

Diagnostic ultrasound is an important adjunct to existing methods in the diagnosis of thoracic disease in the horse. This article discusses scanning techniques, anatomy of the thoracic cavity, and how diagnosis of pleural effusion, pulmonary abscessation, pneumothorax, and vegetative endocarditis may be facilitated by ultrasound.

Diseases of the abdomen.

Because the abdomen of the adult horse is too thick to obtain good-quality radiographs, diagnostic ultrasound is a particularly valuable imaging modality in the diagnosis of abdominal disease. The size, shape, position, and texture of the liver, spleen, kidneys, urinary bladder, gravid uterus, and gut wall can be determined by scanning the abdominal surface. The presence or absence of abdominal fluid can be determined efficiently. Gut motility as well as ileus secondary to peritonitis or obstruction can be assessed. Suspected adhesions of the bowel can often be documented, and primary or secondary neoplastic processes can be identified and biopsied.

Diseases of the kidneys.

Ultrasound examination offers important diagnostic and prognostic information in renal disease of the horse. Differentiation between acute nephrosis and chronic renal disease can usually be made because of the advanced degree of morphologic change usually prevalent in chronic conditions. Dilatations of the recesses and pelvis (hydronephrosis) as well as the relative thickness of the renal cortex and medulla are readily determined. Mineral densities (calculi) are recognizable by their characteristic acoustic shadowing.

Transrectal real-time ultrasound scanning of the cow reproductive tract.

A transrectal real-time ultrasound scanning of the cow reproductive tract allows the operator to view images of structures which normally can be only palpated. The device used in these studies allowed exact evaluation of the cow reproductive tract for position, size and consistency of ovaries, uterus and fetuses; these parameters cannot be described to this level of exactness even by the most skilled palpators. This paper describes real-time ultrasound scanning of an ovary containing a cystic corpus luteum and several follicles and ofa nonpregnant and a pregnant tract at different stages of gestation. The device may be expected to aid both the researcher and the practicing veterinarian considerably in the future.

Biometric study of the canine eye, using A-mode ultrasonography.

A biometric study, using A-mode ultrasonography, was done on 32 eyes in 17 clinically normal dogs in vivo. A ringstand technique, using a saline bath supported by a plastic membrane, was used for applying ultrasound to the eye. Four intraocular dimensions were measured, including the distance from the anterior cornea to the anterior lens surface, the lens thickness, the distance from the posterior lens surface to the retina, and the distance from the anterior cornea to the retina. Statistical difference was not found between the total axial length of the right eye compared with the length of the left eye. There was, however, a significant increase of the total axial length of the eye in the male over that in the eye in the female dog (P less than 0.05). Tissue velocities for ultrasound in the canine aqueous and vitreous were equated to the velocity of ultrasound in distilled water at 38.6 C. The tissue velocity of the canine lens was determined experimentally to be 1,710 m/s and was shown to be greater than was the lens velocities in other species. Seemingly, adverse effects from ultrasound exposure were not seen.