The equine spleen is fixed in position in the abdomen by 3 ligaments. It is attached to the stomach cranially by the gastrosplenic ligament, to the diaphragm dorsally by the phrenicosplenic ligament, and to the left kidney by the nephrosplenic ligament.1 Nephrosplenic entrapment of the large colon refers to a specific form of left dorsal displacement in which the ascending colon ultimately becomes positioned dorsal to the spleen and entrapped in the space over the nephrosplenic ligament. Many retrospective studies2–4 have shown that it is most common in middle-aged, larger-framed geldings. The exact cause is unknown.
Surgery has been suggested to be the gold standard of diagnosis and treatment.5,6 However, nonsurgical treatment is an alternative to surgery and offers many benefits including decreased cost, shorter convalescence,7 and a likely negligible effect on resale value of the horse, compared with exploratory laparotomy. The interest in nonsurgical treatment as an initial approach is relatively recent.3,8 Various nonsurgical approaches exist for the treatment of NSELC, including conservative palliative care, exercise (jogging), and rolling under general anesthesia. Protocols for exercising the horse as an approach to nonsurgical management of NSELC are similar between studies.6,9,a In contrast, techniques for rolling horses vary substantially.3,4,10–14
Phenylephrine is an α1-adrenergic receptor agonist that causes peripheral vasoconstriction and splenic contraction. One study15 found the splenic area to decrease to 28% of baseline for at least 25 minutes when phenylephrine was given IV at a rate of 3 μg/kg/min (1.36 μg/lb/min). In a small case series, phenylephrine was used with success when administered to correct NSELC both alone and in conjunction with exercise or rolling.8,15,16,a
Success rates for nonsurgical treatment of NSELC vary widely between studies. An overall 91.5% success rate has been recently reported for conservative palliative care.17 Exercise has been reported to successfully correct NSELC at a rate of 33% to 100%,7,8 while success rates of 33% to 90%3,10–12,16 have been reported for phenylephrine administration and rolling. The purpose of the study reported here was to compare the outcome of horses with NSELC that received nonsurgical treatment with IV administration of phenylephrine and exercise with that of horses treated with IV administration of phenylephrine and a rolling procedure under general anesthesia. To our knowledge, a large-scale study comparing the success rate of rolling under general anesthesia with that of exercise after the administration of phenylephrine has not been published. It is our hypothesis that IV administration of phenylephrine followed by a rolling procedure performed while under general anesthesia has a higher success rate than that of IV administration of phenylephrine followed by exercise for the treatment of NSELC in horses.
Nephrosplenic entrapment of the large colon
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