Magic angle effect on low field magnetic resonance images in the superficial digital flexor tendon in the equine proximal pastern region.

Recognition of artefacts is an essential component of the accurate interpretation of diagnostic images. This study aimed to investigate the presence of magic angle effect in the superficial digital flexor tendon (SDFT) in the equine proximal pastern region. The proximal pastern of four cadaver limbs was imaged using a 0.27 Tesla magnet with high-resolution sequences that are commonly utilised in clinical equine practice. The limbs were imaged in a neutral position and positions that simulated the horse 'leaning in', 'leaning out' and having internal and external rotation of the distal limb. Signal intensity changes in the SDFT were described and compared. The simulated 'leaning in' and external rotation positions resulted in increased signal intensity in the axial and middle thirds of the lateral half of the SDFT on sequences with short echo times. The simulated 'leaning out' and internal rotation positions resulted in increased signal intensity in the axial and middle thirds of the medial half of the SDFT on sequences with short echo times. These signal intensity changes did not occur or were only mild and inconsistent on T2 fast spin echo sequences with longer echo times. The increases in signal intensity in the SDFT are consistent with a position-induced magic angle artefact that has been noted in clinical cases. Attention to positioning of the equine distal limb is essential during clinical imaging; radiologists should be aware of position-induced artefacts to ensure accurate image interpretation.

Idiopathic Fibrosis of the Tunica Muscularis of the Large Intestine in Five Horses with Colic.

Histological evidence of fibrosis affecting the outer layer of the large intestinal tunica muscularis was identified in five of 32 horses affected by colic. In three cases, foci of pale eosinophilia and vacuolation of myocytes were observed. These findings are suggestive of a degenerative and fibrotic abnormality in the outer layer of the tunica muscularis of the large intestinal smooth muscle of some horses with colic.

Do low field magnetic resonance imaging abnormalities correlate with macroscopical and histological changes within the equine deep digital flexor tendon?

Correlating magnetic resonance (MR) imaging and histopathological findings is essential to validate low field MR imaging in lame horses. This study aimed to compare signal changes in the deep digital flexor tendon (DDFT) of the distal limb on low field MR imaging with macroscopical and histological findings. Cadaver limbs from lame horses with DDFT lesions were selected. The DDFT MR imaging findings and histopathological results were graded, and macroscopical abnormalities were recorded. There was a strong correlation between MR imaging and histopathology grades (rs = 0.76, p < 0.001) in the foot. There was moderate agreement (Kappa statistic 0.52) between the MR and histopathology grades; agreement was superior further proximal in the foot. The presence and severity of pathology in the DDFT are well represented by the presence and severity of MR imaging signal changes. The study supports the use of low field MR imaging for diagnosis of equine distal limb DDFT lesions.

Effect of N-butylscopolammonium bromide on equine ileal smooth muscle activity in an ex vivo model.

REASONS FOR PERFORMING STUDY: N-butylscopolammonium bromide (NBB) is an anticholinergic agent used to treat spasmodic colic in horses. Intestinal smooth muscle spasm also occurs in horses with intraluminal intestinal obstructions, such as ileal impactions. The antispasmodic effects of NBB may be useful in managing ileal impactions, but the effects of NBB on equine ileal smooth muscle are unknown. OBJECTIVES: To investigate the effects of NBB on spontaneous and induced contraction of the equine ileum in an ex vivo model. STUDY DESIGN: Ex vivo biomechanical study assessing contractile properties in isolate equine ileal smooth muscle with and without exposure to NBB. METHODS: Ileal tissue was collected from 6 healthy horses after euthanasia, and isolated circular and longitudinal smooth muscle strips were connected to isometric force transducers in organ baths. After equilibration, the effect of NBB (1 nmol/l to 100 µmol/l) on spontaneous and carbachol-induced contraction was determined and compared with responses in control tissue. RESULTS: At ≥30 µmol/l, NBB inhibited spontaneous contractions in all muscle strips that exhibited spontaneous activity. N-butylscopolammonium bromide pre-treatment inhibited carbachol-induced contraction in circular (NBB-treated half maximal effective concentration [EC50] 0.530 × 10(-8) mol/l vs. control EC50 41.57 × 10(-8) mol/l) and longitudinal muscle strips (NBB-treated EC50 0.243 × 10(-8) mol/l vs. control EC50 90.84 × 10(-8) mol/l). Abolition of carbachol-induced contraction with NBB was observed at lower concentrations in circular than longitudinal muscle strips. Pretreatment with NBB significantly inhibited carbachol-induced contractions; NBB-treated tissue required greater carbachol concentrations to produce sustained contractions than control muscle strips. Histamine-evoked contraction was not affected by NBB. CONCLUSIONS: N-butylscopolammonium bromide inhibits spontaneous and cholinergically mediated contraction in equine ileal smooth muscle strips ex vivo. Thus, NBB might reduce intestinal spasm in equine ileal impactions and could be useful for medical management of these cases, although further study is needed to confirm these effects in vivo.

Serum cortisol concentrations in horses with colic.

Few studies have evaluated cortisol concentrations in horses with colic. In humans with septic shock, high cortisol levels are associated with an increased risk of death. The objectives of this study were to compare the serum total cortisol concentrations (STCCs) in horses with colic to those without colic, and to assess whether the STCC relates to the pathological nature or outcome of the disease. STCCs were determined at presentation in horses with colic and in systemically healthy 'control' horses. Horses with colic were grouped based on clinical and clinico-pathological parameters at admission, treatment, lesion type and location, and outcome. Univariable and multivariable logistic regression were performed using two different outcome measures: (a) whether the horse had colic or not (yes vs. no), and (b) horse STCC (≥200 nmol/L vs. <200 nmol/L). Horses were more likely to have colic if they presented with high STCCs (≥200 nmol/L compared with <200 nmol/L). Horses with colic and with STCCs ≥200nmol/L were more likely to have moderate or severe colic signs (compared with mild colic) and heart rates >45 beats per min (compared with ≤45 beats per min). It was concluded that colic in horses is associated with elevated STCCs, and increased STCC in horses with colic appears to relate to the severity of the disease. STCCs may provide additional decision-making and prognostic information in horses with colic but further studies are required to avoid misinterpretations associated with the wide variation in STCCs.

The clinical and pathological features of gastric impaction in twelve horses.

REASONS FOR PERFORMING STUDY: Gastric impaction in the horse is poorly described in the veterinary literature. OBJECTIVES: To review the clinical and pathological features of gastric impaction. METHODS: The clinical details of horses presenting with colic over a 7-year period and cases in which gastric impaction was considered to determine the outcome were reviewed. Clinical and clinicopathological data were recorded. RESULTS: Twelve cases of gastric impaction were recorded (1.4% of 857 horses hospitalised for colic). Diagnosis was achieved by ultrasonographic examination, gastroscopy, exploratory celiotomy and/or post mortem examination. Five out of 12 horses were successfully treated, 5/12 were subjected to euthanasia (3 at celiotomy and 2 due to recurrence of impaction) and 2/12 died. Three out of 12 horses had spontaneous gastric rupture despite attempted treatment (one was subjected to euthanasia at celiotomy and 2 died). Post mortem examination (7 horses) revealed gross muscular thickening of the stomach wall in 6/7 horses. Histological examination revealed focal fibrosis of the stomach wall in 4/6 and focal myositis in 1/6 horses. CONCLUSIONS AND PRACTICAL SIGNIFICANCE: Gastric impaction is a rare cause of colic and affected horses can present with acute, chronic or recurrent colic in the presence or absence of other gastrointestinal disease. Spontaneous gastric rupture may occur. A proportion of affected horses have gross thickening of the muscular layers of the stomach wall.

Surgical drainage and post operative lavage of large abdominal abscesses in six mature horses.

Six mature horses with large abdominal abscesses (defined as an abscess >15-20 cm in at least one dimension) were treated by surgical drainage and post operative lavage. The abscess was associated with previous intestinal surgery in one horse, and with Streptococcus equi spp. equi infection in the other 5. A Foley catheter was used to drain and lavage the abscess in all cases. The abscess was accessed by a ventral midline laparotomy in 5 cases and by standing flank laparoscopy in one. Two horses were subjected to euthanasia within 7 days due to persistent or recurrent colic. The other 4 horses survived. Lavage of the abscess was continued for a median time of 19 days. Antibacterial therapy was continued until the plasma fibrinogen concentration was normal (median 47 days). Follow-up information was obtained at a median of 1.8 years. All 4 horses were alive at the time of follow-up; 2 horses had suffered one or more bouts of colic that had responded to medical treatment.

Comparison of high-field and low-field magnetic resonance images of cadaver limbs of horses.

Eleven limbs taken postmortem from 10 lame horses were examined by MRI in a low-field 0.27T system designed for standing horses and a high-field 1.5T system used to examine anaesthetised horses. Nine limbs were examined in the foot/pastern region and two in the fetlock region, and the results were compared with gross pathological examinations and histological examinations of selected tissues. The appearance of normal tissues was similar between the two systems, but the anatomical arrangement of the structures was different due to differences in positioning, and a magic angle artefact was observed at different sites in some imaging sequences. Articular cartilage could be differentiated into two articular surfaces in most joints in the high-field images but could generally be separated only at the joint margins in the low-field images. Abnormalities of tendon, ligament and bone detected by gross examination were detected by both forms of MRI, but some details were clearer on the high-field images. Articular cartilage found to be normal on pathological examination was also classified as normal on MRI, but lesions in articular cartilage detected on pathological examination were identified only by high-field MRI. An abnormality was detected on MRI of all the limbs that had abnormal navicular flexor fibrocartilage on pathological examination.

Evaluation of foot pain in the standing horse by magnetic resonance imaging.

The records of 41 horses with previously undiagnosed foot pain that had been examined by standing magnetic resonance imaging were reviewed and follow-up information was obtained from their owners two years after the examination. A range of soft tissue and osseous abnormalities were identified, with multiple lesions frequently occurring. Deep digital flexor tendonitis was recorded in 12 of the horses, and distension of the distal interphalangeal joint was identified in 15, but it was not always associated with lameness; in contrast, distension of the navicular bursa was always associated with lameness in the seven affected horses. Navicular bone lesions were identified in 13 of the horses, often in the absence of radiographic changes. Follow-up information was obtained for 35 of the horses, 27 of which were alive; of these, 16 had returned to their previous level of performance. Of the five horses with navicular bursal changes, four had been euthanased owing to lameness and the other had returned to work at a reduced level.