Ultrasound as an aid for diagnosis of ovarian abscesses in two mares.

This report describes two mares presented for evaluation of anorexia, fever of unknown origin, and weight loss. Clinical examination, laboratory findings, and transrectal ultrasonographic images suggested ovarian abscessation. One mare was successfully treated medically. Because of financial considerations, the second mare was euthanatized and a postmortem examination was performed. At necropsy, there was an enlarged right ovary with an adhesion to the large colon. Microscopic findings were characteristic of an ovarian abscess.

In vitro response of large colon arterial and venous rings to vasodilating drugs in horses.

OBJECTIVE: To determine in vitro vasomotor response of equine large colon arterial and venous rings with and without endothelium to vasodilator drugs, including dopamine (DOP), dopexamine (DPX), acepromazine (ACE), isoxsuprine (ISX), and nifedipine (NFP). ANIMALS: 7 adult horses. PROCEDURE: Relaxation of large colon arteries and veins in response to vasodilating drugs was determined by measuring the change in tension of vessel rings when exposed to a cumulative concentration range (10(-8) to 10(-4)M) of each drug. Vessel rings, with and without endothelium, were mounted in organ baths, attached to a transducer, and contracted with norepinephrine (NE). Cumulative concentration-response relationships, percentage maximal relaxation, and EC50 (concentration of drug required to relax the NE-induced contracted tissue to 50% of its contracted state) values were calculated. RESULTS: There were significant differences among drugs for EC50 (ACE = ISX < NFP) and percentage maximal relaxation (ACE = ISX > NFP = DPX > DOP) values in veins. Endothelium removal from veins had no significant effect. There were no differences in EC50 values for arteries; however, percentage maximal relaxation was significantly different among drugs (ACE = ISX = NFP > DPX = DOP). Endothelial removal resulted in higher EC50 and lower percentage maximal relaxation values, compared with endothelium-intact arteries. CONCLUSION AND CLINICAL RELEVANCE: ACE and ISX were the most potent and efficacious drugs evaluated and could potentially be used to improve blood flow after correction of large-colon volvulus. Dopamine cannot be recommended because of its biphasic response and potential to further decrease blood flow. Endothelium removal altered the vasodilatory responses of colonic arterial rings, but did not affect venous rings.

Biphasic responses of equine colonic vessel rings to vasoactive inflammatory mediators.

1. The role of endothelium in modulating equine colonic vessel responses to histamine (HST), 5-hydroxytryptamine (5-HT), bradykinin (BK) and acetylcholine (ACh) was evaluated in vitro. 2. Segments of mesenteric arteries and veins were collected from the left ventral colon of six adult horses destined for euthanasia for reasons unrelated to cardiovascular or gastrointestinal systems. Vessels were gently cleansed and cut into 4 mm wide rings. 3. Three vessel conditions namely endothelium intact, endothelium removed and N omega-nitro-L-arginine methyl ester (L-NAME)-treated were used for both arterial and venous rings. Each ring was placed in an organ bath with oxygenated Tyrode's solution. One side of the ring was fixed to the floor of the bath and the other side to a force-displacement transducer interfaced with a polygraph. 4. An initial tension of 2 g was applied to rings which were allowed to equilibrate for 45 min. The bath solution was gently replaced every 15 min and tension was readjusted to 2 g each time except following the last wash. 5. Rings were precontracted with a single EC25 dose of noradrenaline and after the response plateaued, cumulative concentration (10(-12)-10(-4) M) response curves were determined for each agent on separate rings. The relaxation from the precontracted level to the baseline was considered as 100% relaxation. Maximal relaxation and maximal contractions were statistically analyzed. 6. All agents induced a relaxation response initially, followed by a contractile phase as the concentrations increased in both arteries and veins, thus, making a biphasic concentration-response curve. In arteries, relaxation produced by ACh was significantly greater than 5-HT. Endothelium removal and L-NAME treatment significantly reduced relaxation in arteries. Only endothelium removal produced a significant reduction of relaxation in veins. 7. In both arteries and veins, HST and 5-HT produced significantly greater contraction than ACh or BK. No significant change in contraction was observed in arteries either by endothelium removal or L-NAME treatment, however, contraction was significantly reduced in veins by endothelium removal. 8. These findings suggest that the endothelium plays a major role in modulating equine colonic arterial relaxation via nitric oxide and venous contraction via endothelium-derived contractile mediators, probably endothelin and/or arachidonates.

In vitro pullout strength of screws inserted in adult equine third metacarpal bone after overdrilling a 4.5-mm threaded insertion hole.

OBJECTIVE: To determine and compare the in vitro pullout strength of 5.5-mm cortical versus 6.5-mm cancellous bone screws inserted in the diaphysis and metaphysis of adult equine third metacarpal (MCIII) bones, in threaded 4.5-mm cortical bone screw insertion holes that were then overdrilled with a 4.5-mm drill bit to provide information relevant to the selection of a replacement screw if a 4.5-mm cortical screw is stripped. STUDY DESIGN: In vitro pullout tests of 5.5-mm cortical and 6.5-mm cancellous screws in equine MCIII bones. SAMPLE POPULATION: Two independent cadaver studies each consisting of 14 adult equine MCIII bones. METHODS: Two 4.5-mm cortical screws were placed either in the middiaphysis (study 1) or distal metaphysis (study 2) of MCIII bones. The holes were then overdrilled with a 4.5-mm drill bit and had either a 5.5-mm cortical or a 6.5-mm cancellous screw inserted; screw pullout tests were performed at a rate of 0.04 mm/second until screw or bone failure occurred. RESULTS: In diaphyseal bone, the screws failed in all tests. Tensile breaking strength for 5.5-mm cortical screws (997.5 +/- 49.3 kg) and 6.5-mm cancellous screws (931.6 +/- 19.5 kg) was not significantly different. In metaphyseal bone, the bone failed in all tests. The holding power for 6.5-mm cancellous screws (39.1 +/- 4.9 kg/mm) was significantly greater than 5.5-mm cortical screws (23.5 +/- 3.5 kg/mm) in the metaphysis. There was no difference in the tensile breaking strength of screws in the diaphysis between proximal and distal screw holes; however, the holding power was significantly greater in the distal, compared with the proximal, metaphyseal holes. CONCLUSIONS: Although tensile breaking strength was not different between 5.5-mm cortical and 6.5-mm cancellous screws in middiaphyseal cortical bone, holding power of 6.5-mm cancellous screws was greater than 5.5-mm cortical screws in metaphyseal bone of adult horses. CLINICAL RELEVANCE: If a 4.5-mm cortical bone screw strips in MCIII diaphyseal bone of adult horses, either a 5.5-mm cortical or 6.5-mm cancellous screw, however, would have equivalent pullout strengths. A 6.5-mm cancellous screw, however, would provide greater holding power than a 5.5-mm cortical screw in metaphyseal bone.

Role of endothelium and nitric oxide in the in vitro response of equine colonic venous rings to vasoconstrictor agents.

OBJECTIVE: To determine in vitro contractile responses of equine colonic veins to various vasoconstrictor agents. ANIMALS: Colonic veins collected from 8 adult horses. PROCEDURE: Veins were cut into 4-mm-wide rings, placed in organ baths at 37 C, and attached to a force-transducer interfaced with a polygraph; 2 g of tension was applied, and rings were allowed to equilibrate for 45 minutes. Bath solution was replaced, and tension was reapplied at 15-minute intervals. Cumulative concentration responses (10(-8) to 10(-4) M) were determined for each agent, using separate rings (n = 8). Three vein groups were evaluated: endothelium-intact, endothelium-denuded, and N omega-nitro-L-arginine methyl ester (L-NAME, 10(-5) M)-treated. Maximal responses by each vein to each agent were considered 100%; responses to lower concentrations were calculated as percentage of maximum. RESULTS: Considering all vein groups, comparison of the doses that caused 50% of the maximal contraction revealed relative sensitivity of colonic veins to be: angiotensin II (ANG) > thromboxane B2 analogue (TXB) > 5-hydoxytryptamine (5HT) > norepinephrine (NE) > histamine (HST) > prostaglandin F2 alpha (PGF) > vasopressin (VP). Compared with ANG, PGF, TXB, and VP, treatment with HST, 5HT, and NE evoked significantly greater responses. Endothelium-denuded and L-NAME-treated colonic veins had significantly greater maximal contractile responses than did endothelium-intact veins. CONCLUSIONS: Response of colonic veins to vasoconstrictor agents was differential; sensitivity was not altered by endothelium removal or L-NAME treatment; maximal responses of endothelium-intact veins were greater than those of endothelium-denuded and L-NAME-treated veins; and responses of endothelium-denuded and L-NAME-treated veins were not different. CLINICAL RELEVANCE: Alterations in colonic veins that mimic conditions associated with large-colon volvulus may contribute to blood flow alterations, edema formation, and vascular responses to hypovolemic and endotoxic shock.

Ovarian torsion associated with granulosa-theca cell tumor in a mare.

A 12-year-old Morgan mare was examined because of stallion-like behavior of 45 days' duration. Palpation per rectum and transrectal ultrasonographic examination revealed a large left ovary with multiple cystic areas and crepitus. A granulosa-theca cell tumor was suspected. During hospitalization for further evaluation of the affected ovary, the mare developed signs of abdominal pain. Exploratory surgery revealed a large left ovary, which was black with a necrotic and friable surface, and a 720 degrees clock-wise torsion of the ovarian pedicle. Torsion was corrected, and oophorectomy was performed. The mare recovered satisfactorily from surgery. Histologic diagnosis was granulosatheca cell tumor with marked diffuse necrosis. To our knowledge, torsion of the ovarian pedicle has not been reported in the veterinary literature. However, it is not uncommon in women. Ovarian torsion seems to develop in association with neoplasia, cysts, and ovarian hyperstimulation syndrome. Ovarian torsion should be considered as a differential diagnosis for mares with a known ovarian pathologic change such as neoplasia or abscess if signs of abdominal pain are evident.

Adjunctive use of a neodymium:yttrium-aluminum garnet laser for treatment of pythiosis granulomas in two horses.

Pythiosis, caused by Pythium insidiosum, is a common cutaneous granulomatous disease in horses. Surgical removal is the most common treatment; however, high rates of recurrence have been reported. Results of examination of 2 horses with pythiosis granulomas in which a neodymium:yttrium-aluminum-garnet laser was used to photoablate the bed after removal are reported. The mass had not recurred in either horse 1 year after surgery. Photoablation results in collateral thermal necrosis and may kill organisms that have infiltrated surrounding tissues, thus reducing the risk of recurrence.

Role of endothelium and nitric oxide in the response of equine colonic arterial rings to vasoconstrictor agents.

OBJECTIVE: To determine the in vitro contractile responses of equine colonic arteries to angiotensin II, histamine, serotonin, norepinephrine, prostaglandin F2 alpha, vasopressin, and a thromboxane-B2-analogue. STUDY DESIGN: The tension generated in colonic arterial rings placed in organ baths with oxygenated Tyrode's solution at 37 degrees C after exposure to the previously mentioned chemical agents was measured using force-transducers interfaced with a polygraph. SAMPLE POPULATION: Large colon arterial rings collected from eight horses. METHODS: The rings were allowed to equilibrate for 45 minutes after applying 2 g tension. Bath solution was replaced and tension reapplied at 15-minute intervals. Cumulative-concentration-responses were determined for concentrations ranging from 10(-8) M to 10(-4) M on three vessel groups namely endothelium intact, endothelium denuded, and L-NAME treated. The maximal response for each vessel was considered as 100%; responses to lower concentrations were calculated as a percentage of the maximum. The EC50 value was determined for each concentration-response relationship of each agent. RESULTS: Vessels with denuded endothelium or those incubated with L-NAME had greater contractile responses. Angiotensin, histamine, serotonin, and norepinephrine produced greater maximal responses than the other agents. Endothelium denuded rings had lower EC50 values. Responses to norepinephrine and serotonin were affected less by denudation. CONCLUSIONS: Endothelium plays an important role in modulating responses of colonic arterial rings to contractile agents. Endothelium-derived vasodilators, other than nitric oxide, may modulate contractile responses of equine colonic arteries. CLINICAL RELEVANCE: Endothelial damage associated with colonic vovulus may be a major factor for sustained reduced perfusion after surgical correction.