Reasons for performing study: Previous studies indicate similar overall survival of horses with nephrosplenic entrapment of the large colon (NSE), regardless of treatment strategy. Short-term survival of a primarily conservative treatment strategy without rolling under general anaesthesia (GA) and a low proportion of surgical intervention as well as indicators of short-term nonsurvival has not been documented.
Objectives: To document short-term survival of horses with NSE treated in a university referral hospital with a low rate of surgical interventions and to determine factors associated with the decision of treatment and short-term nonsurvival.
Methods: A retrospective review of medical records of 142 horses diagnosed with NSE between January 2000 and October 2009 was undertaken. Case details and clinical parameters from the initial examination, treatment and outcome were recorded. Factors associated with decision of treatment and short-term survival were identified by multiple logistic regression analysis.
Results: Warmblood breeds were over-represented in comparison to the general colic population. Overall short-term survival was 91.5% (130/142) which is similar to previous studies. Three horses considered to be in need of surgery were subjected to euthanasia for economical reasons before treatment. Of 114 conservatively treated horses, 110 (96.5%) survived, as did 20/25 (80%) of surgically treated horses. Nine conservatively managed horses were treated with phenylephrine. Gastric reflux (P = 0.0077), pain (P = 0.024) and abdominal distension (P = 0.05) were associated with the decision to treat surgically. Increased heart rate (P<0.001), and surgery (P = 0.032) were associated with reduced likelihood of short-term survival.
Conclusions and potential relevance: Overall short-term survival was similar to that reported in previous studies with higher proportions of surgically managed cases. Consequently, horses with NSE should be managed by a primarily conservative treatment strategy, with the decision to treat surgically based on specific evidence based criteria.
Nephrosplenic entrapment of the left colon (NSE) is a common cause of colic in horses, accounting for up to 9% of all colic cases in equine referral hospitals (Hofmeister et al. 1998; Johnson and Keller 2005; Hassel et al. 2009). Several small and larger retrospective studies have documented that the prognosis for survival to discharge for horses with NSE is generally good, ranging from 84.2–95.9% regardless of the proportions of horses treated medically vs. surgically (Boening and von Saldern 1986; Kalsbeek 1989; Baird et al. 1991; Sivula 1991; Hofmeister et al. 1998; Hardy et al. 2000; Mezerova et al. 2003; Abutarbush and Naylor 2005; Johnson and Keller 2005). This finding is intriguing, since anaesthesia and/or surgery inherently pose a risk of death or various post operative complications (Sivula 1991; Hardy et al. 2000; Johnston et al. 2002; Mezerova et al. 2003; Mair and Smith 2005a,b; Senior 2005; Auckburally and Flaherty 2009). Furthermore, surgery leads to higher economical costs and longer convalescence than medical treatment (Abutarbush and Naylor 2005). Consequently, these observations and considerations are generally believed to have led to a more conservative approach for the treatment of horses with NSE. At the Large Animal Hospital, University of Copenhagen, we have adopted a primarily conservative treatment strategy with a low proportion of surgical intervention including a very low proportion of phenylephrine treatment and no rolling under general anaesthesia (GA) in the conservatively treated group. While it is generally agreed that surgery should be chosen only when clear indications for surgical intervention exist, no large scale study documenting success rates in a hospital setting routinely treating NSE conservatively without rolling under GA, has been published in the English literature.
The aim of the present study is to document short-term survival of horses with NSE treated in a university referral hospital with a primarily conservative treatment strategy as described above and to determine factors associated with the decision of treatment and short-term nonsurvival.
Our hypothesis was that horses with NSE can be managed by this primarily conservative treatment strategy with an overall short-term survival (survival to discharge) comparable to those arising from treatment strategies with higher proportions of surgery and/or rolling under GA.
Materials and methods
Medical records of horses referred to the Large Animal Hospital, University of Copenhagen with acute colic between January 2000 and October 2009 were reviewed and cases of NSE extracted. Inclusion criteria were a definite diagnosis of NSE at rectal palpation and/or ultrasonography and/or at surgery. A definitive diagnosis at rectal palpation implies that is was specifically stated in the record that ‘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’. Excluded were all cases of ‘possible NSE’ (i.e. where it was stated in the record that ‘taenia was palpated coursing towards the nephrosplenic space’ or other similar unclear diagnosis), cases where the left colon was situated between the spleen and the left abdominal wall and cases referred for NSE that did not have this condition at the initial examination.
The following information from the initial clinical examination of the horses was obtained from the records: age (years), gender (gelding, mare, stallion), breed (Warmblood, Icelandic horse, pony breed, others), time to admission (h), rectal findings, heart rate (beats/min), rectal temperature (°C), packed cell volume (PCV, %), degree of pain (no, mild, moderate, severe) abdominal distension (yes, no), gastric reflux (no [<2 l], yes [>2 l]), borborygmi (normal or deviant, none) plasma lactate (mmol/l), plasma glucose (mmol/l), peritoneal fluid parameters (protein [g/l], white blood cell count [WBC x 109/l]), mucous membrane score (0; capillary refill time [CRT]≤2 s and normal colour, 1; CRT = 2–3 s and normal-light hyperaemic colour, 2; CRT ≥3 s and/or severe discolouration), treatment (conservative, surgery), duration of hospitalisation (days), short-term survival (to discharge).
Decision for surgical intervention was based on a subjective evaluation of the combination of all available clinical and paraclinical information available. It should be noted, however, that there were no predetermined criteria to treat horses surgically and the final decision regarding treatment was made solely at the discretion of the attending surgeon.
Conservative treatment consisted of withholding feed combined with palliative treatment at the discretion of the attending clinician. The medical treatment included standard oral (tap water ± electrolytes administered by nasogastric intubation) and/or i.v. rehydration (NaCl and/or acetated Ringer's solution and/or chlorinated Ringer's solution). Fluid type and rates were adjusted according to fluid needs based on appearance of mucous membranes, capillary refill time and skin elasticity in combination with PCV, blood total protein and acid base deficiencies. Horses without net gastric reflux were primarily hydrated by the oral route. Spasmo-analgesics included metamizole (Vetalgin Vet1 10–40 mg/kg bwt i.v.) as needed and/or nonsteroidal anti-inflammatory drugs (primarily flunixin meglumine [Finadyne Vet]2 at 0.25–1.1 mg/kg bwt i.v.). Horses were allowed to roll spontaneously and sometimes medical treatment was supplemented with i.v. administration of phenylephrine (Metaoxedrin2 20 mg diluted in 500 ml 0.9% NaCl infused over 5–10 min) and subsequent jogging on a lunge for approximately 20 min.
Factors associated with the decision to treat the horse surgically and factors associated with short-term survival were both analysed using a logistic regression model, where the covariates heart rate, PCV, plasma glucose, plasma lactate, plasma protein, rectal temperature, protein in peritoneal fluid, mucous membrane score, pain, gas distension, borborygmi, gastric reflux, age, gender and breed were included in the model. A forward selection strategy was used to identify explanatory variables that predict survival and treatment, respectively. After explanatory variables were included in the model by an inclusion criteria of P<0.10, variables were excluded using backwards elimination. Any explanatory variable was initially included as an interaction between treatment and the variable when analysing survival, since treatment has an indirect role as an intermediate variable relative to survival. A likelihood ratio test statistic P<0.05 was considered significant (Ekstrom and Sorensen 2010).
Horses determined to be in need of surgery, but subjected to euthanasia for economic reasons before initiation of treatment, were not included in the reported short-term survival for conservatively or surgically treated horses, nor were they included in the regression analysis of factors associated with short-term nonsurvival. However, these cases were included in the overall short-term survival and in the regression analysis for determination of factors associated with decision for surgical intervention.
The influence of ‘time to admission’ on survival and the difference in ‘duration of hospitalisation’ between the 2 treatments were not included in the logistic regression analysis but analysed separately by t tests.
Distribution of breed, gender (Fisher's exact test) and age (t test) of the included horses were compared to all colic horses (NSE horses excluded) in the same hospital in the period 2004–09 (reference population).
For all statistical analyses, a P value <0.05 was considered significant.
During the study period, 1576 horses were admitted for colic and a total of 142 (9%) horses with a certain diagnosis of NSE were identified. The study population consisted of 9 stallions (6.3%), 72 geldings (50.7%) and 59 mares (41.5%) and 2 horses of unrecorded gender distributed among the following breeds: Warmblood (n = 71), pony breeds (n = 13), Icelandic horses (n = 7), others (n = 40) and horses of unrecorded or unknown breed (n = 11). There were significantly more (P<0.001) Warmblood horses among horses with NSE (50%) than in the reference population (38%). Median age at presentation was 8 years (range 9 months–36 years).
Clinical and demographic data at first examination are shown in Table 1 (survivors vs. nonsurvivors) and Table 2 (conservatively vs. surgically treated).
Table 1. Clinical and demographic findings at initial examination of horses with NSE sorted on short-term survival
|Heart rate (beats/min)||49 ± 1||68 ± 7|
|Packed cell volume (%)||37 ± 1||40 ± 4|
|Plasma glucose (mmol/l)||6.88 ± 0.19||7.74 ± 0.85|
|Plasma lactate (mmol/l)||1.7 ± 0.15||3.67 ± 0.96|
|Plasma protein (g/l)||67 ± 1||68 ± 3|
|Rectal temperature (°C)||37.8 ± 0.1||38.2 ± 0.4|
|Peritoneal fluid protein (g/l)||11 ± 1||31 ± 3|
|Mucous membrane score|| || |
| 0||87 (72.5%)||2 (22.2%)|
| 1||31 (25.8%)||4 (44.4%)|
| 2||2 (1.7%)||3 (33.3%)|
|Pain|| || |
| None||16 (12.5%)||0 (0%)|
| Mild||100 (78.7%)||1 (11.1%)|
| Moderate||6 (4.7%)||4 (44.4%)|
| Severe||5 (3.9%)||4 (44.4%)|
|Gas distension|| || |
| No||91 (70%)||5 (55.5%)|
| Yes||39 (30%)||4 (44.4%)|
|Borborygmi|| || |
| Normal or deviant||90 (69.8%)||3 (33.3%)|
| Absent||39 (30.2%)||6 (66.7%)|
|Gastric reflux (>2 l)|| || |
| No||99 (83.2%)||4 (50%)|
| Yes||20 (16.8%)||4 (50%)|
|Age||9.46 ± 0.47||7.72 ± 2.14|
|Gender|| || |
| Gelding||66 (51.6%)||5 (55.6%)|
| Mare||53 (41.4%)||4 (44.4%)|
| Stallion||9 (7.0%)||0 (0%)|
|Duration of hospitalisation (days)||6.9 ± 0.3||3.9 ± 1.5|
|Time to admission (h)||11.4 ± 1.5||28 ± 10|
Table 2. Clinical and demographic findings at initial examination of horses with NSE sorted on treatment
|Heart rate (beats/min)||50 ± 1||56 ± 3|
|PCV (%)||38 ± 1||38 ± 1|
|Plasma glucose (mmol/l)||6.9 ± 0.2||7.33 ± 0.43|
|Plasma lactate (mmol/l)||1.67 ± 0.15||2.74 ± 0.5|
|Plasma protein (g/l)||67 ± 1||67 ± 2|
|Rectal temperature (°C)||37.8 ± 0.1||38.0 ± 0.1|
|Peritoneal fluid protein (g/l)||6 ± 0||18 ± 3|
|Mucous membrane score|| || |
| 0||77 (70%)||13 (59.1%)|
| 1||30 (27.3%)||7 (31.8%)|
| 2||3 (2.7%)||2 (9.1%)|
|Pain|| || |
| None||15 (13.1%)||1 (4.2%)|
| Mild||89 (77.4%)||14 (58.3%)|
| Moderate||6 (5.2%)||4 (16.7%)|
| Severe||5 (4.3%)||5 (20.8%)|
|Gas distension|| || |
| No||86 (73.5%)||12 (48%)|
| Yes||31 (26.5%)||13 (52%)|
|Borborygmi|| || |
| Normal or deviant||80 (69%)||14 (56%)|
| Absent||36 (31%)||11 (44%)|
|Gastric reflux (>2 l)|| || |
| No||93 (86.1%)||12 (54.5%)|
| Yes||15 (13.9%)||10 (45.5%)|
|Age||9.72 ± 0.5||7.99 ± 0.96|
|Gender|| || |
| Gelding||54 (47%)||18 (72%)|
| Mare||54 (47%)||5 (20%)|
| Stallion||7 (6%)||2 (8%)|
|Duration of hospitalisation (days)||5.7 ± 0.3||11.5 ± 1|
|Time to admission (h)||13.5 ± 1.9||9.4 ± 1.7|
Treatment and survival
Three horses were considered to be in need of surgical intervention but were subjected to euthanasia at the owners' request due to economical constraints before treatment. In total, 114 (82%) were treated conservatively and 25 (18%) surgically. Conservatively treated horses were managed as stated in the materials and methods section. Among the conservatively treated horses, 9 also received i.v. phenylephrine treatment.
Overall, 130/142 (91.5%) of the included cases survived to discharge. Of the conservatively treated cases, 114 (96.5%) survived short term, as did 20/25 (80%) of the surgically treated cases.
Of the surgically treated horses, 2 were subjected to euthanasia due to post operative recurrence of NSE with severe intractable pain, one due to post operative myositis, one due to nonresponsive post operative ileus and one intraoperatively because of poor prognosis (perforated large intestine and diffuse peritonitis). Of the medically treated horses, 2 were subjected to euthanasia because of signs of cardiovascular shock, one because of peritonitis and one because of concurrent suspected lymphosarcoma, which was confirmed at post mortem examination.
Results of statistical analysis
For the selection of treatment, the final model was comprised of gastric reflux (P = 0.0077), pain (P = 0.024) and abdominal distension (P = 0.05) as explanatory variables, meaning that the presence and/or increased severity of these parameters were highly associated with the decision for surgical intervention. For analysis of factors associated with short-term survival the final model included heart rate (P = 0.00062) and treatment (P = 0.032) as explanatory variables, meaning that increased heart rate and surgical treatment were significantly associated with reduced likelihood of short-term survival. Odds ratios (OR) and confidence intervals (CI) for these parameters are presented in Tables 3 and 4. In addition, pain and peritoneal fluid protein were found to show complete separation in the analysis of factors associated with short-term survival. This means that increase of any of these parameters is indicative of reduced likelihood of short-term survival but that the number of events (nonsurvivors) in the data is too small to give an absolute estimate of the relevant parameters.
Table 3. Results of the logistic regression analysis of factors associated with decision for surgical treatment
|Gastric reflux||0.0077|| || |
| No gastric reflux|| ||1.00|| |
| >2 l gastric reflux|| ||4.57||1.52–13.77|
|Gas distension of the abdomen||0.05|| || |
| No distension|| ||1.00|| |
| Gas distension|| ||2.78||0.98–7.92|
|Pain||0.024|| || |
| No pain|| ||1.00|| |
| Mild pain||2.01||0.18–22.03|
| Moderate pain||6.21||0.47–82.94|
| Severe pain||15.67||1.31–187.42|
Table 4. Results of the logistic regression analysis of factors associated with short-term survival
|Heart rate||0.00062|| || |
| 1 beat/min increment|| ||0.922||0.88–0.97|
| 10 beat/min increments|| ||0.444||0.27–0.73|
|Choice of treatment||0.032|| || |
| Medical|| ||1.00|| |
| Surgical|| ||0.18||0.04–0.85|
Surgically treated horses were hospitalised significantly longer than medically treated horses (P<0.001). Time to admission did not differ significantly between survivors and nonsurvivors (P = 0.1383).
Age (P = 0.525) and gender (P = 0.271) distribution did not differ significantly between NSE horses and the reference population.
A definite diagnosis of NSE was based on rectal examination supplemented by transcutaneous ultrasonography in a minority of cases. Although no gold standard exists for the diagnosis of NSE, rectal examination is generally believed to be adequate for making the diagnosis (Boening and von Saldern 1986; Kalsbeek 1989; Baird et al. 1991; Santschi et al. 1993; Leendertse 2006). However, the use of transcutaneous ultrasonography has been advocated for cases where rectal examination is impaired by gas distension or rendered impossible due to the size of the horse (Santschi et al. 1993; Abutarbush and Naylor 2005). In the present study, cases were included only if a definite diagnosis of NSE was made by rectally palpating the taenia of the left colon coursing over the nephrosplenic ligament. In a previous study, 13/13 rectal diagnoses of NSE and 11/13 rectal presumptive diagnoses of NSE were confirmed by ultrasonography, giving rectal diagnosis of NSE a very high specificity (Santschi et al. 1993) and another report stated that that false positive diagnosis of NSE is uncommon (Baird et al. 1991). Based on these observations, in combination with the rigorous inclusion criteria used, it seems fair to state that the present study includes very few cases, if any, with a false positive diagnosis of NSE and hence the results are considered pertinent for the discussion and conclusions regarding case selection and treatment of horses with NSE.
In the present study, the overall short-term survival of horses presented with NSE of the left colon was 91.5%, which is similar to short-term survival reported in previous studies on NSE (Boening and von Saldern 1986; Kalsbeek 1989; Baird et al. 1991; Sivula 1991; Hardy et al. 2000; Mezerova et al. 2003; Abutarbush and Naylor 2005; Johnson and Keller 2005). However, these previous studies included highly variable proportions of conservatively vs. surgically managed patients. Hardy et al. (2000) and Baird et al. (1991) both reported the proportion of surgically treated horses to be 79% with overall short-term survivals of 94.5 and 93%, respectively. In the study by Sivula (1991) 61% of the included cases were treated surgically, resulting in a 90.9% survival to discharge. Furthermore, in the study by Baird et al. (1991) conservative treatment consisted of rolling under GA and in the study by Hardy et al. (2000) conservative treatment consisted of i.v. phenylephrine and/or rolling under GA, and in neither of these studies was conservative treatment without rolling under GA and/or i.v. phenylephrine attempted. In comparison, Hofmeister et al. (1998) treated 85.7% of the cases conservatively, leading to an overall short-term survival of 95.7% and Johnson and Keller (2005) treated 75.7% conservatively with 93% of the conservatively treated cases surviving short term (Hofmeister et al. 1998; Johnson and Keller 2005). Mezerova et al. (2003) treated 62.3% of the NSE cases conservatively without phenylephrine or rolling under GA. Ninety-three percent of the conservatively treated cases survived short term, leading to an overall short-term survival of 88.7% in that study. In these 3 German studies, conservative treatment included none or only very few horses treated with phenylephrine and/or rolling under GA. The present study thereby corroborates and extends the results of these studies, confirming the clinical impression that horses with NSE can be treated by a primarily conservative strategy resulting in a short-term survival similar to that of treatment strategies with significantly more cases subjected to surgery and/or general anaesthesia.
As stated above, several alternatives to surgical correction of NSE exist. These include rolling under GA, withholding feed, oral or i.v. rehydration, administration of spasmolytic agents and/or i.v. administration of phenylephrine.
A few studies have shown that rolling under GA is an effective and safe treatment (Boening and von Saldern 1986; Kalsbeek 1989) that might resolve the problem faster than a more conservative approach. However, GA also poses the risk of death or other serious complications (Johnston et al. 2002; Senior 2005; Auckburally and Flaherty 2009), which should be recognised when considering this treatment.
Intravenous administration of phenylephrine is another treatment option and in the present study 9 horses were initially treated with phenylephrine and subsequent jogging. In 3 of these cases, NSE had resolved immediately after jogging. Of the remaining 6 horses, 5 were cured without surgery or rolling but it was not possible to determine from the records when within the subsequent 48 h correction had occurred. This is comparable to a previous study where i.v. phenylephrine treatment resulted in complete and immediate resolution in only 2/12 cases (van Harreveld et al. 1999), whereas duration to complete resolution was 24–48 h in 9 of the remaining horses and one horse was treated surgically after unsuccessful medical treatment. In another study, NSE resolved immediately after i.v. phenylephrine only in 1/3 horses (Abutarbush and Naylor 2005). Intravenous administration of phenylephrine results in a dose dependent volume reduction of the spleen, which returns to its initial volume within 35 min (Hardy et al. 1994), and hence release of the left colon would be expected to occur within this period if attributable to this treatment per se. As indicated from the present and previous studies not all horses with NSE are cured immediately after i.v. phenylephrine followed by exercise and the observed ‘late effect’ might simply account for cases that resolved automatically due to time and/or palliative treatment. However, some horses are cured immediately and Hardy et al. (2000) also showed significant better results by combining phenylephrine and rolling under GA than rolling without phenylephrine treatment. Consequently, phenylephrine treatment without or in combination with rolling under GA might still be considered when treating cases not requiring surgery. However, a recent study has shown that phenylephrine treatment might cause severe haemorrhage in aged horses (Frederick et al. 2010), so the risks vs. benefits of this treatment should be evaluated carefully, especially in old horses.
In the present study the presence of gastric reflux, increased pain and abdominal distension at the initial examination were shown to be highly associated with the choice of surgical intervention. These parameters have also been identified to be correlated with the need for surgery in previous studies on colic (Ducharme et al. 1989; Reeves et al. 1991, 1992; Thoefner et al. 2003; Ihler et al. 2004). Other parameters previously concluded to be indicative of the need for surgery in colic horses include heart rate, plasma lactate, results of abdominal paracentesis, altered or absent borborygmia, result of rectal examination, appearance of mucous membranes, capillary refill time, rectal temperature, mental status and sweating (Ducharme et al. 1989; Reeves et al. 1991, 1992; Thoefner et al. 2003; Ihler et al. 2004; Johnson and Keller 2005) and these parameters should probably always be included in the evaluation of the need for surgery in any horse presented with gastrointestinal colic.
In the present study, increased heart rate and surgery were associated with reduced likelihood of short-term survival. Furthermore, increased pain and increased peritoneal fluid protein were also indicative of reduced likelihood of short-term survival. Regarding heart rate, pain and protein in peritoneal fluid, this is in agreement with several previous studies (Puotunenreinert 1986; Reeves et al. 1992; Furr et al. 1995; Thoefner et al. 2000; Braun et al. 2002; van der Linden et al. 2003; Ihler et al. 2004). However, none of these parameters can be used as a sole and definitive predictor of nonsurvival, but should be considered when advising owners on treatment options. In the present study, surgery was associated with poorer survival than conservative treatment, which is in accordance with all previous studies on NSE. However, the inclusion of treatment in the logistic regression might be considered somewhat arbitrary since treatment was not randomly assigned. Nevertheless, treatment was included in the model since it was hypothesised to have a potential effect on outcome. Whether the effect of treatment reflects the risk of surgery per se or the fact that horses going to surgery are initially more severely affected by the disease is impossible to determine from the present study. However, this finding should certainly not lead to avoidance of surgery in cases where the need for surgery has been determined, based on findings published in the literature.
Another interesting finding of the present study is a significantly higher proportion of Warmblood breeds among NSE horses compared to the reference population. This was noted by Hofmeister et al. (1998) and, although it was stated in another study that the included horses were representative of the hospital case population, no pony breeds were represented (Hardy et al. 2000). From these findings it might be speculated that NSE is facilitated by larger size of the horse, although this cannot be determined from the present study.
Although it is undisputed that surgical intervention will correct NSE immediately, several other factors should be taken into consideration when deciding between conservative and surgical treatment of these cases. Despite the relatively uncomplicated surgical approach to NSE, the rate of post operative complications after surgical correction of NSE (Sivula 1991; Hardy et al. 2000; Mezerova et al. 2003) is within the range reported for other colic surgeries (Mair and Smith 2005a, 2005b). Furthermore, the costs of colic surgery combined with a significantly longer hospital stay will result in significantly higher economical costs to the owner, as previously shown by Abutarbush and Naylor (2005). Finally, and potentially of most importance to owners or trainers, is the recuperation time: horses treated conservatively will be back in full work within a few weeks, whereas a ventral midline celiotomy will lead to a prolonged convalescence of 4–6 months.
In conclusion, the present case series of horses presented with NSE, where 82% were treated conservatively without rolling under GA, documented an overall survival rate of 91.5%, which does not differ from those reported in previous studies with higher proportions of surgically treated cases. The present study thereby confirms the clinical experience, that horses with NSE can be treated effectively and safely by adhering to a primarily conservative treatment strategy with careful evidence-based selection of horses in need of surgery. Criteria for surgical intervention include the presence of gastric reflux in combination with increased pain and abdominal distension as identified in the present study.
Conflicts of interest
No conflicts of interest have been declared.
Source of funding
No external funding was received for this study.
Jeanne Pilegaard for her invaluable help with retrieving patient records and all veterinarians, technicians and students involved in the treatment of these patients.
1 Intervet Danmark, Ballerup, Denmark.
2 Ophta A/S, Gentofte, Denmark.