Duration of disease influences survival to discharge of Thoroughbred mares with surgically treated large colon volvulus

Dexmedetomidine preconditioning reduces ischaemia-reperfusion injury in equine model of large colon volvulus

BACKGROUND

Large colon volvulus is a cause of colic in horses with high morbidity and mortality when not promptly treated. More treatment options are needed to improve the outcome of these cases by protecting against the damage caused by ischaemia and reperfusion injury.

OBJECTIVES

To determine the effect of preconditioning with dexmedetomidine prior to induction of ischaemia-reperfusion (IR) injury in a large colon volvulus model in the horse.

STUDY DESIGN

Randomised blinded in vivo experiments.

METHODS

Horses received either a dexmedetomidine (DEX) or saline (CON) constant rate infusion (CRI) immediately following induction of anaesthesia. Venous, arterial, and transmural occlusion of a section of the large colon was performed for 3 h, after which the ligatures and clamps were removed to allow for reperfusion for 3 h. Biopsies of the large colon were taken at baseline, 1 and 3 h of ischaemia, and at 1 and 3 h of reperfusion.

RESULTS

The severity of crypt epithelial loss (DEX = 2.1 [0.8-2.8], CON = 3.1 [2.5-4], p = 0.03) and mucosal haemorrhage was decreased (DEX = 2.1 [1.3-3], CON = 3.5 [2.5-4], p = 0.03) in group DEX compared to group CON when graded on a scale of 0-4. Crypt length remained longer (DEX = 369.5 ± 91.7 μm, CON = 238.5 ± 72.6 μm, p = 0.02) and interstitium to crypt (I:C) ratio remained lower (DEX = 1.4 (1-1.7), CON = 2.6 [1.8-5.9], p = 0.03) in group DEX compared to group CON during reperfusion.

MAIN LIMITATIONS

Clinical applicability of pharmacologic preconditioning is limited.

CONCLUSION

Preconditioning with a dexmedetomidine CRI prior to IR injury demonstrated a protective effect histologically on the large colon in the horse. Further investigation into postconditioning with dexmedetomidine is warranted as a possible intervention in colic cases suspected of being large colon volvulus.

Use of multiple admission variables better predicts intestinal strangulation in horses with colic than peritoneal or the ratio of peritoneal:blood l-lactate concentration

BACKGROUND

Early identification of strangulating obstruction (SO) in horses with colic improves outcomes, yet early diagnosis of horses requiring surgery for SO often remains challenging.

OBJECTIVES

To compare blood and peritoneal fluid l-lactate concentrations, peritoneal:blood l-lactate ratio, peritoneal minus blood (peritoneal-blood) l-lactate concentration and other clinical variables for predicting SO and SO in horses with small intestinal lesions (SO-SI) and then to develop a multivariable model to predict SO and SO-SI.

STUDY DESIGN

Retrospective cohort.

METHODS

A total of 197 equids admitted to a referral institution for colic between 2016 and 2019 that had peritoneal fluid analysis performed at admission were included. Twenty-three admission variables were evaluated individually for the prediction of a SO or SO-SI and then using multivariable logistic regression. Odds ratios (ORs) with 95% confidence intervals (CI) and area under the curve of the receiver operator characteristic (AUC ROC) were calculated.

RESULTS

All variables performed better in the model than individually. The final multivariable model for predicting SO included marked abdominal pain (OR 5.31, CI 1.40-20.18), rectal temperature (OR 0.30, CI 0.14-0.64), serosanguineous peritoneal fluid (OR 35.34, CI 10.10-122.94), peritoneal-blood l-lactate (OR 1.77, CI 1.25-2.51), and peritoneal:blood l-lactate ratio (OR 0.36, CI 0.18-0.72). The AUC ROC was 0.91. The final multivariable model for predicting SO-SI included reflux volume (OR 0.69, CI 0.56-0.86), blood l-lactate concentration (OR 0.43, CI 0.22-0.87), serosanguineous peritoneal fluid (OR 4.99, CI 1.26-19.74), and peritoneal l-lactate concentration (OR 3.77, CI 1.82-7.81).

MAIN LIMITATIONS

Retrospective, single-hospital study design.

CONCLUSIONS

Blood and peritoneal fluid l-lactate concentrations should be interpreted in conjunction with other clinical variables. The relationship between peritoneal and blood l-lactate concentration for predicting SO or SO-SI was complex when included in a multivariable model. Models to predict SO probably vary based on lesion location.

Small Colon Faecalith with Large Colon Displacement in Ten Cases (2015-2023): A Detailed Case Description and Literature Review

Small colon impaction can result in accumulation of ingesta, gas, and fluid orally to the impaction site in horses. Large colon tympany, which is caused by ingesta fermentation, can be a predisposing factor for intestinal displacement. The aim of this study is to report the history, clinical, and surgical findings of horses and ponies referred for abdominal pain not responsive to drugs where a right dorsal displacement (RDD) or large colon volvulus (LCV), together with a small colon faecalith (SCF), were diagnosed during surgery. This study included a total of five horses and five ponies. Based on clinical features, ultrasonographic examination, and rectal palpation, an initial suspected diagnosis of RDD, LCV or severe large colon and caecum distension was made in all clinical cases. Due to the lack of response to medical treatment or worsening of colic symptoms, surgery was performed in all horses: diagnosis of RDD or LCV was made and a SCF was incidentally detected in all cases. While exploratory laparotomy was carried out in all the patients for the presence of a large colon issue, it was probably subsequent to an obstruction of the small colon caused by the presence of an SCF, which is generally difficult to diagnose. This study reported the presence of SCF as a possible cause of secondary RDD or LCV in horses and ponies that, to the authors' knowledge, has never been reported.

Epidemiology of Colic: Current Knowledge and Future Directions

Epidemiologic studies are essential for the generation of evidence-based, preventive health care strategies. This includes ways to minimize colic risk and assist informed decision making concerning diagnosis, treatment, and likely outcomes. It is important to consider that colic is not a simple "disease" but is a syndrome of abdominal pain that encompasses multiple different disease processes, and which is multifactorial in nature. This review focuses on prevention and diagnosis of colic, including specific forms of colic, communications with owners/carers concerning colic risk and management, and areas of future research.

Updates on Diagnosis and Management of Colic in the Field and Criteria for Referral

Gastrointestinal colic is the most common primary care equine emergency and affects nearly one of four horses per year. Colic is a significant welfare concern for equine patients and a financial and emotional burden for owners. The primary care practitioner is instrumental in identifying critical cases quickly and making appropriate management recommendations to improve patient outcomes.

Early Identification of Intestinal Strangulation: Why It Is Important and How to Make an Early Diagnosis

Horses with colic caused by intestinal strangulation can have an excellent outcome with early surgical correction of the obstruction. The expense associated with surgery is typically less with early lesion correction. The challenge is making an early diagnosis of intestinal strangulation. Although for some horses with a strangulating obstruction, the need for surgery is made based on severe colic signs or lack of response to analgesia, in other horses, it is less obvious. Signalment, history, and meticulous physical examination, combined with some targeted diagnostic procedures can help with early diagnosis of intestinal strangulation. Improving the outcome of these horses requires diligence and a team-based approach from the owner or caregiver, primary care veterinarian, and specialists.

Large Colon Volvulus in a Neonatal Foal Secondary to Atresia Coli

An 18 hours old foal presented with a suspected meconium impaction. There was no response to treatment and a tentative diagnosis of atresia coli (AC) was made. Surgical intervention was declined and the foal was euthanized 12 hours after admission. Type 3 AC was confirmed on post-mortem examination, with the colon ending at the left ventral colon. A 1,080 large colon volvulus (LCV) at the sternal flexure was present. It is speculated that AC could predispose the foal to LCV. Histopathology was not performed but would be useful in further cases of AC.

Performance of predictive models of survival in horses undergoing emergency exploratory laparotomy for colic

Objective

To evaluate previously published predictive survival models in a population of horses undergoing colic surgery in the midwestern United States.

Study design

Retrospective cohort study; single referral hospital.

Animals

A total of 260 horses met the inclusion criteria.

Methods

Medical records of horses undergoing surgical treatment for colic were reviewed. Previously published models were applied to cohort data to predict outcome. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy for prediction of short‐term survival were calculated.

Results

Single‐variable and multivariable models performed similarly for prediction of survival, with a mean 79% sensitivity (range: 44%–94%), 48% specificity (range: 22%–83%), 63% PPV (range: 56%–72%), 73% NPV (range: 60%–83%), and 64% accuracy (range: 59%–72%). Blood lactate ≤6 mmol/l and the colic severity score (CSS) were highly sensitive for prediction of survival; however, both had poor specificity.

Conclusion

Single‐variable and multivariable predictive models did not perform as well for prediction of survival in the study cohort compared to original reports, suggesting that population‐specific factors contribute to patient survival.

Clinical significance

Predictive models of survival developed in one population may be less reliable when used to predict outcome in horses undergoing colic surgery from an independent population. Additional model testing and refinement using data from multiple surgical centers could be considered to improve prediction of outcome for horses undergoing laparotomy for treatment of colic.

Predictive Models for Equine Emergency Exploratory Laparotomy in Spain: Pre-, Intra-, and Post-Operative-Mortality-Associated Factors

The extrinsic and intrinsic characteristics of an equine population may influence the onset of gastrointestinal lesions and affect the survival rate of patients. The equine population in Spain has been the focus of a small number of studies, none of which have involved more than one surgical center. In this retrospective cohort study, we aimed to analyze the survival rate, identify the variables that influenced death, and generate multivariate models using clinical variables. Data were collected from the clinical records of two surgical referral centers in the same region, and a total of 566 horses met the inclusion criteria. The statistical analysis was divided into three parts: The first and second included logistic analysis, in order to identify the variables most closely associated with survival. The third part assessed all previous variables in terms of survival and hospitalization time, using a COX survival analysis. The main risk factors associated with intra-operative mortality were related to seasonality (winter and summer), patient age (older than 9 years), distance from the hospital, the presence of a strangulating lesion, and the bowel segment affected (small intestine). Furthermore, the main factors associated with mortality during hospitalization were the characteristics of the lesions (strangulating) and the differences between surgical centers. The models generated in this study have good predictive value and use only reliable and easily obtainable variables. The most reliable characteristics are those related to the type of colic and the location of the lesion.

How to perform a percutaneous cecal or colonic trocarization in horses with severe abdominal tympany

BACKGROUND

Cecal or colonic gas tympany of any cause may result in increased intraabdominal pressure, causing a significant decrease in venous return and cardiac output. Trocarization of the large colon or cecum in the event of large intestinal tympany may resolve gas distension and accompanying increased intraabdominal pressures sufficiently enough to promote resolution of a displaced large colon. Furthermore, trocarization of the medical colic may decrease morbidity and mortality associated with severe intraabdominal hypertension.

DESCRIPTION

This how-to description details the technique of transcutaneous trocarization of the large colon and cecum in the standing horse using a 14-gauge catheter.

SUMMARY

Trocarization is not a substitute for surgery in the severely gas-distended painful horse exhibiting signs of colic that require surgery; however, it is a viable medical therapy with minimal risk that alleviates gas distention and may assist with correction of a colonic displacement in the horse.

KEY POINTS

The majority of colic episodes involving the large colon can be managed medically without surgical intervention. Auscultation and percussion of the paralumbar fossa area will solicit an audible "ping" (gas/fluid interface), thus targeting the appropriate site for trocarization. Percutaneous trocarization allows for rapid controlled decompression of colonic or cecal tympany, permitting improvement of both ventilation and perfusion. In situations where a displacement or primary colonic or cecal tympany is suspected, trocarisation is deemed successful if the horse has resolution of colic signs and the physical examination parameters return to normal. Trocarization may be clinically advantageous by requiring less pain medication, decreased time in the hospital, decreased costs, and avoidance of surgical intervention; yet, this therapy should not take place of surgical intervention if deemed necessary.

Managing Reproduction Emergencies in the Field: Part 2: Parturient and Periparturient Conditions

Selected conditions affecting broodmares are discussed, including arterial rupture, dystocia, foal support with ex utero intrapartum treatment, uterine prolapse, postpartum colic, the metritis/sepsis/systemic inflammatory response syndrome complex, and retained fetal membranes. Postpartum colic beyond third-stage labor contractions should prompt comprehensive evaluation for direct injuries to the reproductive tract or indirect injury of the intestinal tract. Mares with perforation or rupture of the uterus are typically recognized 1 to 3 days after foaling, with depression, fever, and leukopenia; laminitis and progression to founder can be fulminant. The same concerns are relevant in mares with retention of fetal membranes.

Expression of Proteinase-Activated Receptor 2 During Colon Volvulus in the Horse

Large colon volvulus in horses is associated with a poor prognosis, especially when ischemic-reperfusion injury of the affected intestinal tract develops. Proteinase-activated receptor 2 (PAR₂) plays an important role in the pathogenesis of inflammation in the gastrointestinal tract. The aim of this study was to evaluate the distribution and expression of PAR₂ in colonic pelvic flexure of horses spontaneously affected by large colon volvulus (CVH group). Eight horses admitted for severe abdominal colon volvolus and which underwent surgery were included. Colon samples were collected after enterotomy. Data previously obtained from healthy horses were used as a control group. Histologic evaluation was carried out to grade the severity of the colon lesions. Immunofluorescence, western blot and quantitative polymerase chain reaction (RT-qPCR) were carried out on colon samples to evaluate PAR₂ expression. In addition, the transcriptional profile of cytokines and chemokines was evaluated using RT² Profiler™ PCR Array Horse Cytokines & Chemokines. Three out of the eight patients were euthanised due to clinical deterioration. Immunostaining for PAR² was observed in the enterocytes, intestinal glands and neurons of the submucosal and myenteric plexi. In the CVH horses, the expression of PAR₂ mesenger RNA (mRNA) did not differ significantly from that of the healthy animals; western blots of the mucosa of the colon tracts showed a clear band of the expected molecular weight for PAR₂ (~44 kDa) and a band smaller than the expected molecular weight for PAR₂ (25kDa), suggesting its activation. The gene expressions for C-X-C motif ligand 1 (CXCL1); interleukin 8 (IL8), macrophage inflammatory protein 2 beta (MIP-2BETA) were upregulated in the colic horses as compared with the colons of the healthy horses. Therefore, in the present study, the expression and activation of PAR₂ in the colons of horses in the presence of an inflammatory reaction like that occurring in those with spontaneous colon volvulus was confirmed.

Comparison of histomorphometric characteristics of dorsal colon and pelvic flexure biopsy specimens obtained from horses with large colon volvulus that underwent resection

OBJECTIVE

To determine the degree of histomorphometric damage in dorsal colon and pelvic flexure biopsy specimens (DCBSs and PFBSs, respectively) obtained from horses with large colon volvulus (LCV) and assess the accuracy of predicting short-term outcome for those horses on the basis of DCBS or PFBS characteristics.

ANIMALS

18 horses with ≥ 360° LCV that underwent large colon resection.

PROCEDURES

During surgery, biopsy specimens from the dorsal colon resection site and the pelvic flexure (when available) were collected from each horse. Interstitial-to-crypt (I:C) ratio (ratio of the lamina propria space occupied by the interstitium to that occupied by crypts), hemorrhage within the lamina propria (mucosal hemorrhage score [MHS] from 0 to 4), and percentage losses of glandular and luminal epithelium were determined in paired biopsy specimens and compared to determine optimal cutoff values for calculating the accuracy of DCBS and PFBS characteristics to predict short-term outcome (survival or nonsurvival after recovery from surgery).

RESULTS

Paired biopsy specimens were obtained from 17 of the 18 horses. The I:C ratio and percentage glandular epithelial loss differed between DCBSs and PFBSs. For DCBSs, an I:C ratio ≥ 0.9 and MHS ≥ 3 each predicted patient nonsurvival with 77.8% accuracy. For PFBSs, an I:C ratio ≥ I and MHS ≥ 3 predicted patient nonsurvival with 70.6% and 82.4% accuracy, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Although different, histomorphometric measurements for either DCBSs or PFBSs could be used to accurately predict short-term outcome for horses with LCV that underwent large colon resection, and arguably PFBSs are easier to collect.

Multicenter Placebo-Controlled Randomized Study of Ethyl Pyruvate in Horses Following Surgical Treatment for ≥ 360° Large Colon Volvulus

Identifying therapies that mitigate ischemic colonic injury and improve mucosal healing and intestinal viability are crucial to improving survival in horses with ≥360° large colon volvulus (LCV). Ethyl pyruvate is the ethyl ester of pyruvate with diverse pharmacologic effects that limit ischemic injury and hasten intestinal mucosal repair in preclinical rodents, sheep and swine models. The objective of this study was to determine the effects of ethyl pyruvate on systemic indices of colon viability, expression of inflammatory genes in whole blood, morbidity and survival after surgical correction of LCV compared to controls. Horses received either 150 mg/kg ethyl pyruvate in 1 liter lactated Ringer's solution (LRS) or 1 liter LRS intravenously (IV) every 6 h for 24 h following surgical recovery for correction of LCV. Colic duration, perioperative heart rate (HR), packed cell volume (PCV), total solids (TS), blood L-lactate concentration, surgical time, intraoperative episodes of hypoxemia and hypotension, expression of inflammatory cytokine genes, fecal consistency and survival to hospital discharge were compared between ethyl pyruvate treated horses and controls. Twenty-two horses, 12 receiving ethyl pyruvate and 10 controls, were enrolled in the study. Ethyl pyruvate was safely administered to horses following surgical correction of LCV. No significant effects of ethyl pyruvate on post-operative variables, including survival, were found. Seven of 12 ethyl pyruvate treated horses and 5/10 controls survived to hospital discharge. Higher HR, PCV and blood L-lactate concentration at the time of hospital admission, P = 0.005, 0.01, 0.04, respectively, 24 h after surgery, P = 0.001, 0.03, 0.02, respectively, were associated with death. Heart rate, P = 0.005, 48 h after surgery was associated with death. Ethyl pyruvate was safely administered to horses following correction of LCV with no apparent adverse events but was not associated with improved post-operative outcomes including survival. A larger, randomized control trial is needed to fully evaluate the effectiveness of ethyl pyruvate. A major limitation of this investigation is the small sample size, making the study underpowered and creating a high possibility of type II error.

Prognostic value of colonic and peripheral venous lactate measurements in horses with large colon volvulus

OBJECTIVE

To determine the prognostic value of (1) colonic venous lactate or peripheral lactate values obtained before and after manual correction of a large colon volvulus and (2) a combination of variables including pelvic flexure biopsy.

STUDY DESIGN

Prospective clinical study.

ANIMALS

Forty adult horses in which large colon volvulus was diagnosed intraoperatively.

METHODS

Colonic venous, peripheral venous, and arterial blood samples were collected to measure lactate values before and after manual correction. Mucosal biopsy samples were obtained in cases that underwent enterotomy or colonic resection and anastomosis. Interstitium to crypt (I:C) ratio and hemorrhage scores were measured. Optimal cutoff values were determined by receiver operator curve analysis, and associations between variables and short-term outcome were determined by univariable regression. Short-term survival was defined as horses being discharged from the hospital. P ≤ .05 was considered significant.

RESULTS

No association was found between colonic venous lactate values before (P = .011) or after (P = .201) manual correction of large colon volvulus and determination of short-term outcome. Peripheral venous lactate at admission ≥3.2 mmol/L and after manual correction ≥5 mmol/L, arterial lactate postmanual correction ≥3.53 mmol/L, and histomorphometric measurements of mucosal hemorrhage ≥3 and I:C ratio > 1 were associated with poor short-term outcome.

CONCLUSION

Peripheral lactate values, histomorphometric measures of I:C ratio, and hemorrhage score provided prognostic information that could help guide recommendations made to owners.

CLINICAL SIGNIFICANCE

Peripheral lactate values after manual correction provide important intraoperative diagnostic information to assist in predicting case outcome in the operative and immediately postoperative period.

A longitudinal study of the faecal microbiome and metabolome of periparturient mares

Background

Periparturient mares are at increased risk of colic including large colon volvulus, which has a high mortality rate. Alterations in colonic microbiota related to either physiological or management changes, or both, that occur at this time have been suggested as potential causes for increased colic risk in this population of horses. Although the effect of management changes on the horse faecal microbiota has been investigated, limited work has been conducted to investigate changes in faecal microbiota structure and function in the periparturient period. The objectives of the current study were to investigate temporal stability of the faecal microbiota and volatile organic compounds (VOCs) of the faecal metabolome in periparturient mares.

Methods

Faecal samples were collected weekly from five pregnant mares from 3 weeks pre-foaling to 7 weeks post-foaling. The microbiome data was generated by PCR amplification and sequencing of the V1–V2 regions of the bacterial 16S rRNA genes, while the VOC profile was characterised using headspace solid phase microextraction gas chromatography mass spectrometry.

Results

The mare faecal microbiota was relatively stable over the periparturient period and most variation was associated with individual mares. A small number of operational taxonomic units were found to be significantly differentially abundant between samples collected before and after foaling. A total of 98 VOCs were identified. The total number of VOCs did not vary significantly between individual mares, weeks of sample collection and feeds available to the mares. Three VOCs (decane, 2-pentylfuran, and oct-2-ene) showed significant increase overtime on linear mixed effects modelling analysis. These results suggest that the mare faecal microbiota is structurally and functionally stable during the periparturient period. The findings also suggest that if changes in the gut microbiota are related to development of colic postpartum, altered risk may be due to inherent differences between individual mares. VOCs offer a cost-effective means of looking at the functional changes in the microbiome and warrant further investigation in mares at risk of colic.

Colic Prevention to Avoid Colic Surgery: A Surgeon's Perspective

Management factors associated with colic, particularly related to stall confinement and nutrition, have been linked to alterations in gastrointestinal mucosal transport, motility, and microbiome, which in turn creates conditions that induce colic. In particular, meal feeding creates large changes in water movement in and out of the colon and alters the microbiome. These conditions may in turn result in colic conditions such as large colon impaction or large colon volvulus. In addition, a range of management and nutritional factors have been found to place horses at risk of select colic conditions such as ileal impaction. Other specific colic conditions, such as strangulating lipomas, may be related to fat metabolism in geldings and ponies, although the association with nutrition and the endocrine system are less well defined. It has long been understood that parasites are associated with colic, and with the advent of highly effective anthelmintics, parasite-induced colic has been markedly reduced. Nonetheless, equine mangers and veterinarians have to be aware of changes in parasite resistance or patterns of activity, such as the resurgence of large strongyles with surveillance-based management of parasites. Overall, understanding management risk factors can lead to recommendations that prevent colic in horses. Additional study of these factors may ultimately lead to reductions in the prevalence of colic by suggesting optimal management practices.

Exploratory Celiotomy in the Horse Secondary to Acute Colic: A Review of Indications and Success Rates

To review indications and risk factors for exploratory celiotomy secondary to acute colic in the horse; decision making for and during surgery; and prognosis for return to function after exploratory celiotomy for the practicing veterinarian. Data sources included scientific reviews and original research publications from veterinary sources, as well as clinical data specifically in regard to underlying disease and survival rates from a tertiary referral hospital where exploratory celiotomy is commonly performed. There is a high positive predictive value of specific clinical preoperative parameters of the equine acute abdomen, many of which rely on techniques available to field practitioners, relative to the need for surgical intervention. Decision making regarding surgical procedure or even intraoperative euthanasia depends on owner expectations. Survival rates following exploratory celiotomy range from fair to excellent (60%-100%) depending on underlying lesion and return to athleticism following celiotomy is good to excellent (76%-90%). A knowledge base of indications for and rates of survival from colic requiring exploratory celiotomy in the horse is of paramount importance to the equine practitioner. Preconceived notions of poor survival rates are rampant among horse owners, and owners rely on their primary veterinarian's advice for continuation to referral center and in further treatment including exploratory celiotomy.

Equine Intestinal Mucosal Pathobiology

The equine intestinal mucosa is intimately involved in maintaining homeostasis both on a systemic level by controlling extracellular fluid movement and at the local level to maintain barrier function. Horses are particularly susceptible to the clinical syndrome of colic, with the most severe cases involving strangulating obstruction that induces ischemia. Because of the mucosal vascular architecture, the mucosal epithelium is particularly susceptible to ischemic injury. The potential for reperfusion injury has been investigated and found to play a minimal role. However, inflammation does affect mucosal repair. Mechanisms of repair, including villus contraction, epithelial restitution, and tight junction closure, are critical to reforming the mucosal barrier. Nonsteroidal anti-inflammatory drugs have an impact on this repair, particularly at the level of the tight junctions. Completion of mucosal regeneration requires proliferation, which is now being actively studied in equine enteroids. All of these aspects of equine mucosal pathobiology are reviewed in depth.