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.
Materials and Methods
Case selection—The medical records of horses with signs of abdominal pain that were evaluated at the Equine Medical Center of Ocala between January 2004 and December 2010 that met the inclusion criteria of a diagnosis of NSELC and underwent nonsurgical treatment (exercise [jogging], rolling, or both) were reviewed retrospectively. Each horse was given phenylephrine IV and then exercised or rolled under general anesthesia, or both (if exercised unsuccessfully, then rolled), on the basis of the discretion of the admitting clinician. Only horses that were exercised after IV administration of phenylephrine or rolled via the modified procedure were included in this study. Cases of NSELC that were identified on exploratory celiotomy but were not exercised or rolled before surgery were excluded from the study.
Medical records review—A diagnosis of NSELC was made on the basis of findings on abdominal palpation per rectum, ultrasonographic findings, or findings at surgery. Findings on abdominal palpation per rectum were considered diagnostic for NSELC when it was stated in the record that the taenia of the left colon could be palpated coursing over the nephrosplenic ligament or that the left colon could be palpated in the nephrosplenic space. Horses in which the nephrosplenic space could be palpated normally were considered free of NSELC and not included in the study. Findings on abdominal palpation per rectum were confirmed by a board-certified surgeon or internist. Percutaneous left flank abdominal ultrasonography was used alone for diagnosis only in horses in which large amounts of gas distension precluded palpation of the nephrosplenic space and in horses that were too small for abdominal palpation per rectum. Ultrasonographic examination was performed via a 2.5- to 3.5-mHz variable frequency probe applied to the left 15th to 17th intercostal space parallel to the ground.13,b Percutaneous abdominal ultrasonography that identified a gas echo proximal to the spleen that prohibited imaging the left kidney was considered diagnostic for NSELC.
Administration of phenylephrine—All horses that were treated by exercise or rolling had a jugular catheter placed IV. Each horse received phenylephrinec (20 μg/kg [9.1 μg/lb]) diluted in sterile saline (0.9% NaCl) solution to a final volume of 60 mL and given slowly over 10 minutes. Given the short duration of action of phenylephrine on the spleen,15,18 the rolling or exercise treatment was initiated immediately following the administration of phenylephrine. Horses that underwent multiple forms of nonsurgical treatment (ie, if exercise was attempted and unsuccessful, then the horse was rolled) were given an additional dose of phenylephrine IV prior to each additional form of nonsurgical treatment.
Exercise—Immediately after administration of phenylephrine, the horse was encouraged to trot continuously in a circle for 15 minutes within a 20-m-diameter round pen as described.5,a Immediately after exercise, the horses were reevaluated with a combination of abdominal palpation per rectum, abdominal ultrasonography, or both. If the horse had ongoing signs of abdominal pain and NSELC was not resolved, they subsequently underwent the rolling procedure.
The rolling procedure—Immediately after administration of phenylephrine, horses were sedated with xylazine (1 mg/kg [0.45 mg/lb]) and butorphanol (0.02 mg/kg [0.01 mg/lb]) and then anesthetized by IV administration of ketamine (2.2 to 3.3 mg/kg [1 to 1.5 mg/lb]) and diazepam (50 μg/kg [23 μg/lb]). Horses were positioned in left lateral recumbency.
By use of an overhead hoist, the horse was placed into dorsal recumbency on a bare recovery stall floor with all 4 limbs attached to the hoist at the region between the metatarsophalangeal or metacarpophalangeal joints and the hooves (ie, pasterns). The horse's limbs were in a relaxed position with no tension, and an attendant helped to maintain the horse in dorsal recumbency with the sternum pointing towards the ceiling (Figure 1). One person straddled the neck of the horse and stabilized the flexed forelimbs, and another person stood behind the horse and stabilized the flexed hind limbs. The horse was placed approximately 0.75 m from the wall of the recovery stall. Two adults sat on the recovery stall floor and placed their backs to the recovery stall wall with their feet against the left side of the horse's abdomen (paralumbar fossa and caudally located ribs) and their knees at an approximately 90° angle. The 2 adults then simultaneously extended and relaxed their legs to maintain a rapid piston-like compression and relaxation to the left abdomen. Seven to 10 cycles of piston-like compressions and relaxation were performed at a frequency rate of approximately 30 extensions-relaxations/min for 5 minutes. The hoist was then lowered so the horse was positioned towards a right lateral recumbent position and the sternum made an approximately 30° angle to the floor. The same rapid piston-like action described previously was used for an additional 5 minutes. As a final step, once removed from the hoist, the horse was rotated from left lateral recumbency to right lateral recumbency 3 to 4 times. The total duration of the procedure was approximately 15 minutes.
Modified rolling technique for nonsurgical treatment of NSELC in a horse. A horse was placed in dorsal recumbency positioned 0.75 m from the wall of the recovery stall, and 2 people were aligned between the left paralumbar fossa and caudal ribs with their backs against the stall wall. With their feet on the horse and knees at a 90° angle, the assistants simultaneously employed a rapid piston-like compression to the left abdomen for 5 minutes.
Citation: Journal of the American Veterinary Medical Association 242, 8; 10.2460/javma.242.8.1146
Modified rolling technique for nonsurgical treatment of NSELC in a horse. A horse was placed in dorsal recumbency positioned 0.75 m from the wall of the recovery stall, and 2 people were aligned between the left paralumbar fossa and caudal ribs with their backs against the stall wall. With their feet on the horse and knees at a 90° angle, the assistants simultaneously employed a rapid piston-like compression to the left abdomen for 5 minutes.
Citation: Journal of the American Veterinary Medical Association 242, 8; 10.2460/javma.242.8.1146
Modified rolling technique for nonsurgical treatment of NSELC in a horse. A horse was placed in dorsal recumbency positioned 0.75 m from the wall of the recovery stall, and 2 people were aligned between the left paralumbar fossa and caudal ribs with their backs against the stall wall. With their feet on the horse and knees at a 90° angle, the assistants simultaneously employed a rapid piston-like compression to the left abdomen for 5 minutes.
Citation: Journal of the American Veterinary Medical Association 242, 8; 10.2460/javma.242.8.1146
The horse was lowered into right lateral recumbency on the floor of the recovery stall, and percutaneous abdominal ultrasonography of the left paralumbar fossa was performed. If the kidney-spleen interface was not imaged, the rolling procedure was performed again at the discretion of the clinician. Finally, the horse was lifted with the hoist and placed in left lateral recumbency on a recovery mat. Each of the horses that proceeded to exploratory celiotomy after the rolling procedure was allowed to recover from general anesthesia and return to the stall for 10 to 15 minutes prior to reassessment of clinical signs and election to proceed to exploratory celiotomy. This was to facilitate the possible influence of standing and walking after recovery on correction of the NSELC.
A treatment success was defined as resolution of clinical signs of abdominal pain and resolution of the NSELC as assessed via abdominal palpation per rectum and abdominal ultrasonography. Treatment failures were defined as horses that continued to have signs of abdominal pain shortly upon returning to the stall after treatment (exercise, rolling, or both). Horses with treatment failures had an NSELC that was discovered on exploratory celiotomy (either alone or with coexisting gastrointestinal tract lesions) or continued to have an NSELC as detected on abdominal palpation per rectum and abdominal ultrasonography, indicating ongoing NSELC immediately prior to elective euthanasia.
Data collection—The following variables were recorded for each horse in the study: date of initial examination; breed (warmblood, Thoroughbred, Quarter Horse, Paso Fino, Arabian, or other breed); sex (gelding, sexually intact male, or female); age (years); heart rate (beats/min); net gastrointestinal reflux; findings on abdominal palpation per rectum and abdominal ultrasonography; pain at initial examination (none, dull and lethargic, mild, moderate, or severe); number of analgesics administered during evaluation prior to nonsurgical treatment; PCV and blood concentrations of WBC, total protein, and lactate; peritoneal fluid concentrations of WBC, total protein, and lactate; treatment procedures performed with each exercise or rolling procedure preceded by IV administration of phenylephrine (exercise; rolling; exercise and rolling; rolling and exploratory celiotomy; or exercise, rolling, and exploratory celiotomy); number of times phenylephrine was given IV; trocharization of cecum or ascending colon prior to rolling (yes or no); position of the postrolling ultrasonographic examination (horse recumbent or standing); number of times rolled (if applicable); whether surgery was performed (yes or no); whether NSELC was identified at surgery (yes or no; if applicable); survival (discharged, died, or euthanized); days hospitalized; and cost (in US dollars).
Statistical analysis—Horses were grouped on basis of treatment (exercise vs rolling). Continuous variables were summarized as medians (10th to 90th percentile), and categorical data were summarized as proportions. Normality of the data and equality of variances were assessed via the Shapiro-Wilk and Levene tests, respectively. The Mann-Whitney U test was used to test for differences between treatment groups with regard to continuous variables. The Fisher exact test was used to test for differences between groups for dichotomous variables such as outcome (success or failure) and presence of gastric reflux (yes or no).d,e
Factors possibly associated with treatment failure were initially evaluated for tolerance and variance inflation factor. Factors with tolerance < 0.10 and a variance inflation factor > 10 were deleted to avoid multicollinearity. Initial screening of factors possibly associated with survival was performed by use of univariate logistic regression. Variables for which the screening P value was < 0.20 were included in the multivariate model. The multivariate model was a backward stepwise model, whereby variables were removed sequentially starting with that having the largest P value. Odds ratios and 95% confidences were calculated. An odds ratio > 1 corresponded to a positive association with treatment failure, whereas a ratio < 1 corresponded to a negative association. For all analyses, a value of P < 0.05 was considered significant.
Results
During the study period, 88 horses with NSELC that met the inclusion criteria were identified. Thoroughbred horses comprised the majority of the cases (62/88), and the median age was 2 years. Presumptive diagnosis of NSELC was achieved via abdominal palpation per rectum in 70% (62/88) of cases, with the remaining cases diagnosed via abdominal ultrasonography because gas distension precluded palpation of the nephrosplenic space or the small size of the horse made abdominal palpation per rectum impossible. Seventy-three of the 88 (83%) cases met the ultrasonographic criteria, and both criteria were met in 47 of 88 (53%) of cases.
Admission variables were not significantly different between horses that were rolled and those that were exercised (Table 1). The success rate of rolling under general anesthesia after IV administration of phenylephrine (42/50 [84.0%]) was significantly (P = 0.045) higher than the success rate of exercise after IV administration of phenylephrine (24/38 [63.2%]; Table 2). Fourteen horses that underwent exercise as the initial nonsurgical treatment did not have resolution of clinical signs of abdominal pain and had findings on abdominal palpation per rectum consistent with or ultrasonographic evidence of persistent NSELC. The success rate of the rolling procedure after a failed exercise attempt was 57% (8/14). Duration of hospital stay and hospital cost were not significantly different between groups. The overall success rate of nonsurgical intervention (exercised only, rolled only, or exercised and then rolled) following IV administration of phenylephrine in the resolution of signs of abdominal pain was 85% (75/88).
Comparison of admission variables between horses that were initially exercised and horses that were rolled for correction of NSELC.
| Variables | Exercised (n = 38) | Rolled (n = 50) | P value |
|---|---|---|---|
| Sex (No. of male/No. of female) | 20/18 | 25/25 | 0.833 |
| Age (y)* | 2 (1–12) | 1 (1–11) | 0.882 |
| Heart rate (beats/min)* | 50 (40–66) | 48 (36–72) | 0.993 |
| > 3 L of reflux (No. of horses) | 4 | 10 | 0.248 |
| Pain score (1 = none; 5 = severe)* | 3 (1–4) | 3 (1–4) | 0.098 |
| Blood measurements* | |||
| WBC count (cells/μL) | 9,900 (5,620–14,300) | 9,800 (6,300–14,700) | 0.710 |
| PCV (%) | 39 (31–47) | 37 (29–42) | 0.074 |
| Total protein (g/dL) | 6.8 (6.9–7.5) | 6.5 (6.0–7.5) | 0.380 |
| Lactate (mmol/L) | 2.2 (1.1–4.2) | 2.3 (1.2–4.2) | 0.575 |
| Peritoneal fluid measurements* | |||
| WBC count (cells/μL) | 2,200 (650–8,400) | 1,200 (340–6,920) | 0.032 |
| Total solids (g/dL) | 2.0 (2.0–5.1) | 2.3 (2.0–5.3) | 0.797 |
| Lactate (mmol/L) | 0.9 (0.7–4.6) | 1.1 (0.7–4.3) | 0.767 |
Values are medians (10th to 90th percentile).
Outcome variables in 88 horses with NSELC treated by either exercising or rolling.
| Variable | Exercised (n = 38) | Rolled (n = 50) | P value |
|---|---|---|---|
| Success rate (%) | 63.2 | 84.0 | 0.045 |
| Duration of hospital stay (days)* | 3 (2–6) | 3 (2–5) | 0.476 |
| Total cost (US dollar)* | 2,413 (1,487–6,336) | 2,463 (1,976–5,712) | 0.484 |
Values are median (10th to 90th percentile).
Twelve of the 88 horses required exploratory celiotomy. Each of the 12 horses that had NSELC discovered on exploratory celiotomy were classified as treatment failures. Of the 12 surgical cases that had NSELC, 9 had no additional gastrointestinal lesions found at the time of surgery. The remaining 3 horses had coexisting lesions, including partial nonstrangulating small intestinal volvulus (n = 1), 360° large colon volvulus (1), and splenic mass (1). All of these horses had undergone the rolling procedure prior to exploratory celiotomy, and one of these horses was also exercised prior to exploratory laparotomy.
Factors significantly associated with treatment failure in a multivariate logistic regression model included high peritoneal fluid total solids concentration (> 2.2 g/dL), high WBC count (> 9,500 cells/μL), treatment with IV phenylephrine and exercise, and sex (male; Table 3).
Results of multivariate logistic regression analysis of admission parameters potentially associated with treatment failure in 88 horses with NSELC.
| Treatment failure | ||
|---|---|---|
| VARIABLE* | OR (95% CI) | P value |
| Multivariate model† | ||
| Peritoneal fluid total solids (> 2.2 g/dL) | 23.2 (1.40–383) | 0.028 |
| Blood WBC count (> 9,500 cells/μL) | 268 (4.99–14,300) | 0.006 |
| Treatment (jogged) | 23.3 (1.75–311) | 0.017 |
| Sex (male) | 32.2 (1.97–527) | 0.015 |
All variables were tested. Only values significant in the multivariate model are presented in Table 3. Addition of other variables did not improve the significance of the model.
Overall significance of the multivariate model was P < 0.001
CI = Confidence interval.
Eight horses were rolled more than once during the same hospitalization period (6 were rolled twice and 2 were rolled 3 times). Three of the 8 horses that were rolled multiple times had NSELC found on exploratory celiotomy.
No horses died or were euthanized that received exercise as their only treatment. The overall short-term survival rate for all horses included in the study was 98.9% (87/88). One horse that did not have a surgical option was euthanized after being rolled under general anesthesia because of continued signs of abdominal pain attributed to entrapped colon as seen via percutaneous abdominal ultrasonography. None of the cases in this study had fatal injuries sustained during anesthesia or recovery, and all horses that underwent exploratory laparotomy survived beyond time of discharge. None of the horses given phenylephrine IV were noted to have an adverse reaction or severe hemorrhage during the duration of hospitalization.
Discussion
This study compares exercise (15 minutes of trotting in a round pen) with rolling under general anesthesia after IV administration of phenylephrine for the correction of NSELC. It differs from previous studies because it compares 2 forms of nonsurgical treatment rather than combining nonsurgical treatments into a single group.7,17 The overall success rate of rolling under general anesthesia after IV administration of phenylephrine (84%) was significantly higher than exercise after IV administration of phenylephrine (63.2%). Although these success rates are lower than those in a study18 that used primarily conservative care, they are similar to previous success rates for both exercise7,8 and IV administration of phenylephrine and rolling.3,10–12,16 It is difficult to directly compare these results with results of previous studies of NSELC owing to differences in populations of horses and the inconsistent administration of phenylephrine IV.
A recent study17 reported an overall 91.5% short-term survival rate with conservative nonsurgical management consisting primarily of IV fluid administration and palliative treatment over several days. In contrast, a previous study3 found that the probability of successful nonsurgical management decreased with increasing duration of clinical signs of NSELC. In several studies, most nonsurvivors had complications or concurrent lesions such as large colon volvulus, large colon rupture, or vascular thrombosis.4,10,17,19 Such concurrent lesions or complications are less likely to be corrected surgically if exploratory laparotomy is delayed by attempting prolonged conservative treatment. In the present study, nonsurgical intervention (exercise or rolling) was attempted early during the course of hospitalization. By doing so, there is only a slight delay in surgical intervention for horses that do not respond to exercise or rolling. In the present study, 2 of 12 horses that underwent exploratory laparotomy had an intestinal volvulus in addition to NSELC. A prolonged delay before surgical intervention may have had devastating consequences for these 2 horses. In the present study, the overall short-term survival rate of 98.9% (87/88) following initial nonsurgical treatment that consisted of exercise or rolling after IV administration of phenylephrine was higher than survival rates reported for various other methods of correction for NSELC.4,10,17,19,20 In the present study, all 12 horses that required exploratory laparotomy survived after initial nonsurgical treatments that had failed to resolve the entrapment. This suggests that early nonsurgical interventions can be attempted without adverse effects on surgical outcome or survival rate.
Factors significantly associated with treatment failure in a multivariate logistic regression model included high peritoneal fluid total protein concentration (> 2.2 g/dL), high WBC count (> 9,500 cells/μL), IV administration of phenylephrine and exercise, and sex (male). The high peritoneal fluid total protein concentration and high WBC count may suggest more compromised large intestine, possibly related to a longer or more resistant entrapment,3 which may be difficult to dislodge and therefore necessitate exploratory laparotomy. The association between treatment with phenylephrine and exercise and therapeutic failure is simply due to the fact that this treatment modality was significantly less effective than administration of phenylephrine and rolling.
Although no adverse reactions were noted following IV administration of phenylephrine, potential disadvantages of the administration of phenylephrine prior to exercise and the rolling procedure include the possibility of fatal hemorrhage,21 a predisposition to arrhythmias,22 and potential vasoconstriction of the splanchnic vasculature.23 The disadvantages of both exercise and rolling procedure include the inability to evaluate the integrity of the entrapped large intestine, the possibility of worsening a preexisting surgical lesion, and the possibility of inducing a gastrointestinal rupture.8
The rolling procedure described in the present study has subtle differences, compared with the rolling procedures used in previous reports.3,4,6,10,11,13,14
The horse has all 4 limbs attached to the hoist at all times, and the horse is not rolled into sternal recumbency, which can be difficult to accomplish. Additionally, each horse that proceeded to exploratory celiotomy after the rolling procedure was allowed to recover from general anesthesia prior to the reassessment of clinical signs and election to proceed to celiotomy. It is impossible to conclude whether the details of the rolling procedure itself influenced the success rate since it was not directly compared with other rolling methods.
The diagnostic methods used to diagnose NSELC have limitations. On abdominal palpation per rectum, false-positive diagnoses may occur if the colon assumes a dorsal position within the abdomen for other reasons, such as torsion or gas-induced abdominal pain.24 On percutaneous abdominal ultrasonography, false-negative results can occur if gas is absent from the section of entrapped colon, which eliminates the gas echo separating the kidney and spleen. Alternatively, false-positive results may occur if the colon is dorsal to the left kidney without entrapment.13 However, this limitation should not have affected the comparison between exercise and rolling, as the same inclusion criteria were used for both groups. Primary clinician inexperience may have contributed to potential misdiagnosis; however, a board-certified surgeon or internist consulted and participated in all cases. Overall, it is difficult to correct for clinician differences in a retrospective study design.
Additional limitations of the study include a non-randomized assignment to a treatment group and the lack of a control group. Although admission variables were not significantly different between horses that were exercised and horses that were rolled, the possibility that there was an unintentional bias in case selection cannot be completely ruled out with a retrospective study design. A randomized prospective study may be warranted to further elucidate the potential benefits of each nonsurgical approach.
In conclusion, a rolling procedure involving the use of general anesthesia in conjunction with IV administration of phenylephrine can be used for the correction of abdominal pain due to nephrosplenic entrapment with an increased success rate, compared with IV administration of phenylephrine and exercise.
ABBREVIATION
| NSELC | Nephrosplenic entrapment of the large colon |
Johnston J. The use of phenylephrine in the treatment of large colon displacement in the horse (abstr), in Proceedings. 6th Annu Meet Am Coll Vet Surg 1996;13.
Logic 5 Pro, General Electric, Waukesha, Wis.
Neo-Synephrine HCl, Hospira Inc, Lake Forest, Ill.
Medcalc, version 11.6.1.0, MedCalc Software, Mariakerke, Belgium.
SPSS, version 18.0, IBM, Armonk, NY.
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