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EQUINE VETERINARY EDUCATION


Equine vet. Educ. (2020) 32 (11) 568-570 doi: 10.1111/eve.13126


Clinical Commentary


The use of phenylephrine in the treatment of nephrosplenic entrapment of the large colon in horses


J. Pye*† and J. Nieto‡ †William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California at Davis, and ‡Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California at Davis, Davis, California, USA *Corresponding author email: jlpye@ucdavis.edu


Keywords: horse; nephrosplenic; phenylephrine; colic; displacement


Summary Nephrosplenic entrapment is a commonly diagnosed cause of acute colic that may be corrected using surgical or non- surgical methods and has a good prognosis for survival. Intravenous administration of phenylephrine at doses ranging from 20–60 lg/kg given over 5–15 min often followed by forced exercise, various rolling techniques under general anaesthesia, or a combination of therapies has been reported. Correction of the entrapment via exploratory celiotomy may be challenging in certain cases and is hampered by marked splenic enlargement. The case report by Loomes and Anderson (2020) in this issue described a novel method of reducing the size of the spleen by direct intra-splenic injection of phenylephrine, in a case non- responsive to intravenous phenylephrine administration, which facilitated surgical correction of the nephrosplenic entrapment.


Left dorsal displacement is a commonly diagnosed cause of acute colic which occurs when the left dorsal colon migrates between the spleen and the body wall. The colon may then become entrapped over the nephrosplenic ligament in the space between the spleen and left kidney; a condition referred to as left dorsal displacementwith entrapment, or nephrosplenic entrapment. Horses with nephrosplenic entrapment typically show more pronounced signs of abdominal pain than horses with left dorsal displacement without entrapment, although the level of pain is variable. Diagnosis is based on abdominal palpation per rectum in combination with transabdominal ultrasonographic examination. Upon rectal palpation the colon is often gas distended and may be located lateral to the left kidney and medial to spleen in the nephrosplenic space. Sonographically, the left kidney and the dorsal border of the spleen are obscured by gas in the large colon and not able to be visualised (Le Jeune and Whitcomb 2014). Although sonographic diagnosis of nephrosplenic entrapment is relatively reliable, false positives have been reported (Scharner et al. 2002). Misinterpretation may arise from other conditions resulting in colonic gas accumulation, such as other forms of displacement and even large colon torsion (Le Jeune and Whitcomb2014). Several treatment options exist for non-surgical


management of nephrosplenic entrapment in addition to intravenous fluid therapy and withholding feed. These include intravenous administration of phenylephrine at doses ranging from 20–60 lg/kg given over 5–15 min often followed by


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forced exercise, various rolling techniques under general anaesthesia, or a combination of therapies. The traditional rolling approach involves positioning the anaesthetised horse in left lateral recumbency, hoisting the hindlimbs and rocking the abdomen for several minutes, and then repositioning the horse in right lateral recumbency (Southwood 2019). Up to 75% of horses were reported to have been corrected with rolling in the retrospective study by Hardy et al. (2000). A more recent study describes a specific method of rolling which requires the horse to be anaesthetised and Positioned in dorsal recumbency 0.75 m from the recovery stall wall using a ceiling-mounted hoist (Fultz et al. 2013). Two adults are seated with their backs stabilised against the recovery stall wall and perform a series of piston-like leg extensions followed by repositioning of the horse and repeating the leg extensions in a number of cycles, described in more detail by Fultz et al. (2013). In this study, a higher proportion of horses with nephrosplenic entrapment were corrected with rolling (84%) compared with exercise (63.2%) following phenylephrine administration (Fultz et al. 2013). Surgical correction via laparotomy or laparoscopy should be considered in any horse that does not respond to non- surgical management, with consideration to the fact that horses may have more than one colic lesion. Exploratory celiotomy is a more reliable means of correcting nephrosplenic entrapment than non-surgical management, although this is typically more costly and results in longer hospitalisation. Laparoscopic surgical correction can be performed if the horse is in mild pain, the colon is not overly distended, and the surgeon has ruled out the possibility of a concurrent small intestinal lesions or adhesions between the spleen and body wall (i.e. from previous abdominal surgery)


(Busschers et al. 2007; Munoz and Bussy 2013). A standing left flank laparotomy approach for correction of nephrosplenic entrapment has been described in three horses, which is a potentially useful technique for horses when general anaesthesia and exploratory celiotomy are not an option (Krueger and Klohnen 2013). Correcting a nephrosplenic entrapment via a ventral


midline celiotomy is accomplished by gently pushing the spleen ventrally and medially over the colon to gradually free the entrapped colon, starting at either the cranial or caudal aspect of the spleen. Correction has been noted to be more difficult when the sternal and diaphragmatic flexures are displaced cranially and dorsally, between the stomach and the liver (Hardy et al. 2000). Large colon rupture is an infrequently encountered but devastating complication of


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