Nonsteroidal antiinflammatory drugs reduce anion secretion and increase apoptosis in equine colonic mucosa ex vivo

OBJECTIVE

Right dorsal colitis causes chronic colic associated with long-term treatment with nonsteroidal antiinflammatory drugs (NSAIDs). This study was designed to determine if NSAIDs could inhibit anion transporters that protect against intestinal mucosal injury in other species.

ANIMALS

20 healthy horses.

METHODS

The effects of indomethacin (INDO) and firocoxib (FIR), on short-circuit current (Isc) in mucosa from the right dorsal colon (RDC) and right ventral colon (RVC) were measured in Ussing chambers by standard electrophysiological techniques. Immunohistochemical methods were used to detect apoptosis (caspase-3) with these NSAIDs and phenylbutazone (PBZ) and to locate the NKCC1 transporter.

RESULTS

The Isc in RDC and RVC incubated with INDO or FIR was increased almost 3-fold (P < .0001) by prostaglandin E2 (PGE2) through a system inhibited by loop diuretics (P < .0001). Although these findings and anion replacement studies were consistent with anion secretion, the RDC also displayed an Isc response suggestive of a unique transporter apparently absent in RVC or NSAID-free solutions. In RDC, FIR, INDO, and PBZ induced apoptosis in the lower half of crypts. However, significant differences in apoptotic index were recorded in the RDC between NSAID-treated and control tissues (no NSAID).

CLINICAL RELEVANCE

The effects of NSAIDs on Isc were consistent with reduced anion secretion, which could represent the pharmacological equivalent of the transport failure responsible for Cystic Fibrosis (CF) in other species. Failure of anion secretion could interfere with buffering acid from intraluminal fermentation, which could suggest a treatment target for right dorsal colitis.

Endoscope-assisted three-wire technique for extensive nasal septum resection in horses

OBJECTIVE

To describe a 3-wire method with endoscopic guidance for extensive nasal septum resection.

STUDY DESIGN

Retrospective study.

SAMPLE POPULATION

Thirteen horses with nasal septum diseases.

METHODS

In anesthetized horses in left lateral recumbency, endoscopic guidance was used to place obstetrical wires for the ventral and caudal incisions in the nasal septum and a trephine opening was used to place the dorsal wire. The rostral aspect of the septum was incised with a scalpel, followed by incisions with the preplaced wires, and the nasal passages were packed with gauze. Horses were recovered with a temporary tracheotomy.

RESULTS

Conversion to intraoral placement of wires was required in two horses, one to correct entangled wires and the other because hemorrhage obscured the endoscopic view. Exercise tolerance was improved postoperatively, abnormal respiratory noise was decreased or eliminated by surgery in all horses, and all owners were satisfied. One Thoroughbred racehorse performed with modest success.

CONCLUSIONS

Modification of the 3-wire method was effective and safe for extensive nasal septum removal. Technical complications of the procedure include entangling of wires and intraoperative hemorrhage.

CLINICAL SIGNIFICANCE

Endoscopic guidance can be used to place obstetrical wires for nasal septum resection in small horses and precludes use of a large tracheotomy for anesthetic delivery. Reasons for athletic failures were difficult to establish retrospectively, although assessment of postoperative noise at speed might be more relevant to recovery of athletic potential than assessment at slower gaits.

Three-dimensional models of the equine larynx can be used to perform traditional measures of arytenoid abduction and permit the positioning of modeled implants to demonstrate the anatomic feasibility of placing a rigid implant across the cricoarytenoid joint

OBJECTIVE

To develop 3D models of larynges to compare arytenoid abduction measurements between specimens and models, and to investigate the anatomic feasibility of placing an implant across the cricoarytenoid joint (CAJ) with or without arthrotomy.

SAMPLES

Cadaveric equine larynges (n = 9).

PROCEDURES

Equine larynges underwent sequential CT scans in a neutral position and with 2 arytenoid treatments: bilateral arytenoid abduction (ABD) and bilateral arytenoid abduction after left cricoarytenoid joint arthrotomy (ARTH). Soft tissue, cartilage, and luminal volume 3-dimensional models were generated. Rima glottidis cross-sectional area (CSA) and left-to-right quotient (LRQ) angles were measured on laryngeal specimens and models. Arytenoid translation, articular contact area, and length of modeled implants placed across the CAJ were measured on models. Data were analyzed using paired t test or ANOVA and Tukey's post hoc test or non-parametric equivalents (P < .05).

RESULTS

ARTH CSA was larger for laryngeal specimens than models (P = .0096). There was no difference in all other measures of CSA and LRQ angle between treatment groups or between specimens and models. There was no difference between ABD and ARTH groups for arytenoid cartilage translation, contact area, and implant length. The articular contact area was sufficient for modeled implant placement across the CAJ with a narrow range of implant lengths (17.59 mm to 23.87 mm) across larynges with or without arthrotomy.

CLINICAL RELEVANCE

These results support further investigation of a CT-guided, minimally invasive surgical procedure. Future studies will evaluate the outcomes of the new procedure for technical precision, biomechanical stability, and post-operative success rates for horses with recurrent laryngeal neuropathy (RLN).

Repeat Celiotomy-Current Status

Repeat celiotomy can be lifesaving in horses with a surgically treatable postoperative obstruction, although guidelines for its use are lacking, except for uncontrollable postoperative pain. Overdiagnosis of ileus as the cause of postoperative obstruction could delay a second surgery so the disease progresses beyond a manageable level of severity. Although many horses respond favorably to repeat celiotomy, complications can be severe and life threatening, such as incisional infection and adhesions. Repeat celiotomy does not seem to exacerbate postoperative ileus, despite additional surgical manipulation. An important benefit of repeat celiotomy is termination of hopeless cases, thereby reducing cost and suffering.

Ex vivo and in vivo evaluation of a modified interrupted Lembert pattern for small intestinal anastomoses in horses

OBJECTIVE

To compare single-layer anastomoses (modified continuous Lembert [mod-CL] and modified-interrupted Lembert [mod-IL]) and a 2-layer simple continuous anastomosis (2 L; seromuscular and mucosal) for jejunojejunal anastomoses in equine cadavers and to compare ex vivo to in vivo time to complete the anastomosis and stoma size with a mod-IL pattern.

STUDY DESIGN

Measurements in jejunum from cadaver and anesthetized horses.

ANIMALS

Ten live horses and 18 equine cadavers.

METHODS

Time to complete anastomosis, bursting pressures (BP), leakage sites, and anastomotic index (size ratio of anastomotic lumen to control lumen) were recorded. Time to completion and lumen size were compared between in vivo and ex vivo mod-IL patterns.

RESULTS

The mod-CL pattern was fastest (8.44 ± 1.30 min, p < .05), and the 2 L pattern was slower (17.07 ± 2.0 min) than the mod-CL and mod-IL (p < .05). The anastomotic index exceeded 100 and did not differ between patterns. Segments reached higher bursting pressures when anastomosed with mod-IL (145.94 ± 24.18 mm Hg) than mod-CL (p < .05). In vivo closure was approximately 8 minutes slower than ex vivo, and with a smaller anastomotic index.

CONCLUSIONS

All anastomoses increased lumen size over control segments ex vivo. Lumen size after placement of a mod-IL was greater ex vivo than in vivo, and completion was slower in vivo than ex vivo. [Corrections added on 26 Dec 2022, after online publication: added "ex vivo" to the first line of Conclusions in the Abstract.] CLINICAL SIGNIFICANCE: Slower and smaller anastomoses should be anticipated in vivo compared to ex vivo results. Anastomoses with a mod-IL pattern appear clinically advantageous, producing a comparable lumen size in less time than 2 L.

Surgical enlargement of the epiploic foramen in horses

OBJECTIVE

To assess the safety and efficacy of a method for digitally enlarging the caudal aspect of the epiploic foramen (EF).

STUDY DESIGN

Healthy horses and clinical cases of EF entrapment (EFE).

ANIMALS

Fourteen healthy horses and three clinical cases.

METHODS

Through a ventral midline celiotomy under general anesthesia, the EF was enlarged by digital separation of the caudal attachments of the caudate lobe of the liver from right dorsal colon, right kidney, gastropancreatic fold, and pancreas. Healthy horses were euthanized under anesthesia, and the enlarged EF was measured at necropsy.

RESULTS

The method used for enlarging the EF did not cause clinically relevant hemorrhage, as determined by visual inspection of the EF in 14 horses at necropsy and by vital parameters under anesthesia in all horses. In clinical cases, EFE was reduced following enlargement of the EF, and no intraoperative complications were encountered. In one clinical case, necropsy at 30 days confirmed partial closure of the enlarged EF.

CONCLUSION

The method proposed enlarged the EF safely and effectively. Limitations of the study include the small number of clinical cases and the lack of postoperative follow-up on the healthy horses.

CLINICAL SIGNIFICANCE

Enlargement of the EF at its caudal extent should be considered in selected cases of EFE in which manual reduction is difficult or protracted. Although the procedure was safe in this study, knowledge of the anatomy, practice on cadavers, and careful selection of cases with greatest need are recommended before clinical use.

Mechanisms of bicarbonate secretion in the equine colon ex vivo

OBJECTIVE

To examine bicarbonate (HCO3−) secretion ex vivo in the equine large colon to determine any differences between the right dorsal colon (RDC) and right ventral colon (RVC). The effect of phenylbutazone (PBZ) on HCO3− secretion was examined in the RDC.

ANIMALS

14 healthy horses.

PROCEDURES

In anesthetized horses (n = 10), segments of mucosa from RDC and RVC were harvested to measure HCO3− secretion ex vivo with the pH Stat method. The effect of PBZ on HCO3− secretion in the RDC was studied in 4 additional horses.

RESULTS

Three distinct mechanisms of HCO3− secretion previously described in a murine model were confirmed in the equine colon. The RDC had a greater capacity for electrogenic, Cl−-independent HCO3− secretion than the RVC (P = 0.04). In the RDC, all HCO3− secretion was decreased by PBZ (P < 0.02) but was not studied in the RVC because of low baseline secretion.

CLINICAL RELEVANCE

Secretion of HCO3− by the RDC could play a pivotal role in equine colon physiology, because intense microbial fermentation in this site could require HCO3− secretion to buffer short-chain fatty acids. Inhibition of this secretion by PBZ could interfere with mucosal buffering and predispose to changes associated with right dorsal colitis.

Effects of age, disease, and anastomosis on short- and long-term survival after surgical correction of small intestinal strangulating diseases in 89 horses

BACKGROUND

Although survival rates have been reported after small intestinal surgery for strangulating diseases in horses, none have followed survival for periods relevant to the long lifespan of horses and none have described effect of age, disease and surgical treatments over such long survival periods.

OBJECTIVES

To examine effects of age, disease, and type of surgery on long-term survival in horses after surgical treatment of small intestinal strangulating diseases over periods relevant to the expected lifespan of a horse.

STUDY DESIGN

Retrospective clinical study.

METHODS

Post-operative data were gathered from medical records and owner contact for 89 horses with small intestinal strangulation. Survival times from surgery to date of death or date of last follow-up were analysed by Kaplan-Meier statistics. Variables of interest were age, type of strangulating disease, and surgical correction. Cox proportional hazards regression was used to evaluate these variables.

RESULTS

Short-term survival was not affected by any of the variables measured. For long-term survival with Kaplan-Meier statistics, horses ≥16 years old had significantly shorter (P=0.002) median survival times (72 months; 95% C.I. 32.0-96.0) than younger horses (121.7 months; 95% C.I. 90.0-162), horses without resection had significantly longer (P=0.02) survival times (120 months; 95% C.I. 86-212) than horses that had jejunocecostomy (76.8 months; 95% C.I. 24-125), and horses with miscellaneous diseases had significantly longer (P=0.02) median survival times (161.9 months (95% C.I. 72.0-M) than horses with strangulating lipoma (79.8 months; 95% C.I. 32.0-120.0). In the multivariable Cox Proportional Hazard model, age (HR=2.67; 1.49-4.75, p<0.001) and anastomosis (HR=0.65; 0.46-0.92, P=0.02) had the most significant effect on median survival time.

MAIN LIMITATIONS

Limitations were small numbers in some categories, loss of cases to follow-up, owner recall failures, and lack of a control group.

CONCLUSIONS

The remaining lifespan of older horses at the time of surgery had the greatest effect on survival. Age could influence long-term survival studies after colic surgery, and therefore needs to be considered for survival analyses. Horses that did not require resection and anastomosis had favourable outcomes, underscoring the potential importance of early intervention to reduce the need for resection.

Endoscopic-guided Esophageal Foreign Body Removal in a Donkey

Esophageal obstruction is a common disorder in equids usually caused by intraluminal impaction with roughage and/or other feed material. Esophageal obstructions can also be caused by foreign bodies, but they are rarely reported and information regarding diagnosis and management is lacking. This report describes an esophageal obstruction in a donkey caused by a metallic foreign body removed using endoscopic guidance. Recognition of the foreign body facilitated treatment and underscores the importance of imaging in such cases to prevent dislodgement of the object to more aboral sites where access would be limited, or gastrointestinal tract injury could be fatal.

Effect of Feed Intake on Water Consumption in Horses: Relevance to Maintenance Fluid Therapy

Maintenance fluid therapy is challenging in horses that cannot drink or are denied feed and water because of concerns about gastrointestinal tract function and patency. Intravenous fluid delivery to meet water needs based on current recommendations for maintenance requirements were obtained in fed horses and therefore might not apply to horses that are not being fed. This is a critical flaw because of the interdependence between intestinal tract water and extracellular water to support digestion while preserving water balance, a concept explained by the enterosystemic cycle. Because horses drink less when they are not eating and hence have lower water needs than fed horses, maintenance water requirements need to be adjusted accordingly. This article reviews this topic and identifies benefits of adjusting maintenance fluid therapy to meet lower demands from gastrointestinal function, such as reduced volumes, lower cost, avoidance of overhydration.

J-incision to approach the cranial abdomen in the adult horse

OBJECTIVE

To describe a modified celiotomy to improve access to cranial abdominal structures in horses.

ANIMALS

Four horses.

STUDY DESIGN

Short case series.

METHODS

Three horses with gastric impactions were treated with gastrotomies. One horse was treated for a diaphragmatic hernia with herniorrhaphy and mesh augmentation. In all horses, the ventral midline celiotomy was modified cranially with a J-incision through the body wall, along the paracostal arch.

RESULTS

The only surgical complications were midline incisional infections in all horses. Three of the four horses had good long-term outcomes; the remaining horse underwent euthanasia for reasons likely unrelated to incisional complications.

CONCLUSION

The J-incision improved access to the stomach and diaphragm in these horses. The paracostal component healed in all cases without evidence of infection or dehiscence.

CLINICAL SIGNIFICANCE

This modified celiotomy may be considered to improve access during gastrotomy and repair of dorsally located diaphragmatic hernias.

Effect of feed deprivation on daily water consumption in healthy horses

BACKGROUND

Measurements of water consumed by fed healthy horses might not apply to horses that are unwilling or unable to drink or are not fed for any reason.

OBJECTIVE

To examine the effects of feed deprivation on voluntary water consumption compared with fed conditions.

STUDY DESIGN

In vivo experiment.

METHODS

Eight healthy adult Thoroughbred geldings were used in a randomised crossover design so that each horse served as its own control for fed vs feed-deprived conditions. Water intake, bodyweight, physical findings and vital signs were measured during 4 days of feeding and 4 days of feed deprivation. Daily measurements during the trial periods were PCV, TPP, electrolytes, osmolality and triglycerides. Plasma and extracellular fluid volumes were measured in the last 8 hours of the trial periods. Data were analysed with a two-way analysis of variance with repeated measures, and statistical significance was P ≤ .05.

RESULTS

Feed deprivation immediately and persistently reduced water consumption to ~16% of fed values, with laboratory evidence of mild dehydration on day 4.

MAIN LIMITATIONS

Changes in total body water and in water and electrolyte excretion or conservation through faeces and urine were not measured.

CONCLUSIONS

Feed consumption has a marked effect on water requirements in healthy horses. Because current guidelines for water needs were obtained in the fed state, they might not apply to horses that are denied feed for any reason or have reduced feed intake. This study provides new information on water consumption in horses that should apply to this essential nutrient in health and disease.

Is There Still a Place for Lidocaine in the (Postoperative) Management of Colics?

Intravenous lidocaine is widely used to prevent or treat postoperative ileus in horses. Clinical studies that support this approach are flawed and contradicted by others. Also, physical obstruction could be more important in causing postoperative reflux than postoperative ileus in the horse. The antiinflammatory properties of lidocaine and the role of inflammation from intestinal handling in the genesis of postoperative reflux are questionable. Because of cost and questionable efficacy of lidocaine, a well-designed clinical trial is required to support its continued use. However, lidocaine could be given to provide or enhance analgesia in selected cases with postoperative colic.

Characterization of equine vitamin D-binding protein, development of an assay, and assessment of plasma concentrations of the protein in healthy horses and horses with gastrointestinal disease

OBJECTIVE To purify and characterize equine vitamin D-binding protein (VDBP) from equine serum and to evaluate plasma concentrations of VDBP in healthy horses and horses with gastrointestinal injury or disease. ANIMALS 13 healthy laboratory animals (8 mice and 5 rabbits), 61 healthy horses, 12 horses with experimentally induced intestinal ischemia and reperfusion (IR), and 59 horses with acute gastrointestinal diseases. PROCEDURES VDBP was purified from serum of 2 healthy horses, and recombinant equine VDBP was obtained through a commercial service. Equine VDBP was characterized by mass spectrometry. Monoclonal and polyclonal antibodies were raised against equine VDBP, and a rocket immunoelectrophoresis assay for equine VDBP was established. Plasma samples from 61 healthy horses were used to establish working VDBP reference values for study purposes. Plasma VDBP concentrations were assessed at predetermined time points in horses with IR and in horses with naturally occurring gastrointestinal diseases. RESULTS The working reference range for plasma VDBP concentration in healthy horses was 531 to 1,382 mg/L. Plasma VDBP concentrations were significantly decreased after 1 hour of ischemia in horses with IR, compared with values prior to induction of ischemia, and were significantly lower in horses with naturally occurring gastrointestinal diseases with a colic duration of < 12 hours than in healthy horses. CONCLUSIONS AND CLINICAL RELEVANCE Plasma VDBP concentrations were significantly decreased in horses with acute gastrointestinal injury or disease. Further studies and the development of a clinically relevant assay are needed to establish the reliability of VDBP as a diagnostic and prognostic marker in horses.

Effects of ischemia and reperfusion on eosinophilic accumulation and distribution in mucosa of equine jejunum and colon

OBJECTIVE To evaluate the eosinophilic response in intestinal mucosa of horses with intestinal ischemia and reperfusion or with strangulation of the jejunum or colon. SAMPLE Mucosal samples from horses with naturally occurring strangulation (n = 24 horses) or distention (n = 6) of the jejunum or colon (11), with experimentally induced ischemia and reperfusion of the jejunum (6) or colon (15), or that were euthanized for reasons other than gastrointestinal tract disease (13). PROCEDURES Mucosal samples were collected and grouped by type of intestinal injury. Slides were stained with Luna eosinophil stain and histologically examined to determine eosinophil accumulation and distribution. Number of eosinophils per mm(2) of mucosa was calculated as a measure of eosinophil accumulation. Additionally, mucosa was categorized into 5 regions; the percentage of eosinophils in each of the 5 regions, relative to the total eosinophil count in all regions, was determined. RESULTS Eosinophil migration toward and onto the luminal surface was evident in tissues after ischemia and reperfusion and after naturally occurring strangulating disease of the jejunum and colon, as indicated by a decrease in the number of eosinophils near the muscularis mucosa and an increase in the number of eosinophils on or near the luminal surface. Ischemia alone did not change eosinophil distribution in the jejunum or colon. CONCLUSIONS AND CLINICAL RELEVANCE Eosinophils responded to mucosal damage evoked by ischemia and reperfusion by migration toward and onto the luminal surface. This migration could represent an important component of the inflammatory response to injury in equine gastrointestinal mucosa.

Update on disorders and treatment of the guttural pouch

The most common disorders of the equine guttural pouches are empyema, tympany, mycosis, and temporohyoid osteoarthropathy. Diagnosis of these conditions is made primarily by imaging with endoscopy, radiographs, computed tomography, and/or MRI. Medical treatment with anti-inflammatories, antimicrobials, and/or antifungals may be successful in some cases, but many of these disorders necessitate surgical intervention. Direct surgical approaches to the guttural pouch are difficult because of their complex anatomy and relationship with important structures, thus precipitating a move toward minimally invasive procedures when possible.

Effects of experimental mechanical manipulations on local inflammation in the jejunum of horses

OBJECTIVE

To determine characteristics of the inflammatory reaction in the jejunum of horses in response to various mechanical manipulations.

ANIMALS

12 adult warm blood horses without gastrointestinal tract disorders.

PROCEDURES

The proximal aspect of the jejunum in each horse was divided into 5 segments, and the following manipulations were performed: manual emptying, placement of Doyen forceps, enterotomy alone, enterotomy with mucosal abrasion, and serosal abrasion. Jejunum samples were collected before (control), immediately after, and 30 minutes after the end of manipulations and histologically evaluated to determine distribution of neutrophils and eosinophils.

RESULTS

Macroscopically, all manipulations resulted in jejunal hemorrhage and edema. Compared with control samples, neutrophil numbers were significantly higher after manipulations in the serosa (after all manipulation types), circular muscle layer (after manual emptying), submucosa (after placement of Doyen forceps), and mucosa (after all manipulations except enterotomy alone). Eosinophil numbers were significantly higher in the submucosa after mechanical abrasion of the serosa and manual emptying versus control samples.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated mechanical manipulation of the jejunum resulted in local inflammatory reactions characterized predominantly by infiltration of neutrophils. This could contribute to the development of postoperative ileus or adhesions in horses without macroscopically detectable injury of the jejunum during surgery.

Effect of large colon ischemia and reperfusion on concentrations of calprotectin and other clinicopathologic variables in jugular and colonic venous blood in horses

OBJECTIVE

To determine the effect of large colon ischemia and reperfusion on concentrations of the inflammatory neutrophilic protein calprotectin and other clinicopathologic variables in jugular and colonic venous blood in horses.

ANIMALS

6 healthy horses.

PROCEDURES

Horses were anesthetized, and ischemia was induced for 1 hour followed by 4 hours of reperfusion in a segment of the pelvic flexure of the large colon. Blood samples were obtained before anesthesia, before induction of ischemia, 1 hour after the start of ischemia, and 1, 2, and 4 hours after the start of reperfusion from jugular veins and veins of the segment of the large colon that underwent ischemia and reperfusion. A sandwich ELISA was developed for detection of equine calprotectin. Serum calprotectin concentrations and values of blood gas, hematologic, and biochemical analysis variables were determined.

RESULTS

Large colon ischemia caused metabolic acidosis, a significant increase in lactate and potassium concentrations and creatine kinase activities, and a nonsignificant decrease in glucose concentrations in colonic venous blood samples. Values of these variables after reperfusion were similar to values before ischemia. Ischemia and reperfusion induced activation of an inflammatory response characterized by an increase in neutrophil cell turnover rate in jugular and colonic venous blood samples and calprotectin concentrations in colonic venous blood samples.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of this study suggested that large colon ischemia and reperfusion caused local and systemic inflammation in horses. Serum calprotectin concentration may be useful as a marker of this inflammatory response.

Long-term survival in horses with strangulating obstruction of the small intestine managed without resection

REASONS FOR PERFORMING STUDY

Although many studies have described results after small intestinal resection and anastomosis in horses, few have described the outcome in horses with strangulating lesions managed without resection.

OBJECTIVES

To examine short- and long-term recoveries in horses with strangulated small intestine that was judged to be viable during surgery and not resected.

STUDY DESIGN

Retrospective analysis of case records.

METHODS

Data were reviewed from all cases (35 horses) with colic caused by small intestinal strangulation that underwent surgery between 1996 and 2011 at 2 university hospitals and that were managed without resection by 2 surgeons who used a clinical grading system to assess intestinal viability. Kaplan-Meier analyses were used to examine long-term survival.

RESULTS

Survival to discharge from the hospital was 100%, and post operative complications developed in 11 horses (31%). Three horses (8.6%) required repeat coeliotomy because of persistent pain with or without reflux, and they responded favourably to decompression of distended intestine. Ten horses died after discharge, and 12 were still alive at follow-up from 20 to 192 months after surgery. Information was available on 13 horses after discharge, but these were eventually lost to follow-up. Kaplan-Meier analyses yielded a median survival probability of 120 months.

CONCLUSIONS

A subjective method of assessing small intestinal viability in strangulated small intestine in horses, as used in this study, could reduce the need for resection and anastomosis, with the associated complications and costs. Also, the favourable post operative course in these horses provides strong evidence that early referral could avoid the need for resection and improve survival. The numbers of horses with the most severe changes that were not resected were too small to allow a conclusion that such segments should be left in place, and additional criteria might be needed to guide that decision in such cases.

New ways to diagnose and treat equine dental-related sinus disease

The diagnosis and treatment of equine dental-related sinus disease is often challenging. Dental-related sinus disease is common and knowledge of these diseases is becoming increasingly important in veterinary medicine. Diagnostic capabilities are continually improving, leading to early diagnostic and therapeutic successes. With advanced imaging modalities, such as computed tomography and magnetic resonance imaging, understanding of the intimate anatomic relationship between teeth and the paranasal sinuses continues to progress. There are many therapeutic options available for the treatment of these common and challenging disorders. A complete understanding of the disease, therapeutic options, and potential complications is vital to overall successful resolution of clinical signs in equine dental-related sinus disorders.

A single caudally based frontonasal bone flap for treatment of bilateral mucocele in the paranasal sinuses of an American miniature horse

OBJECTIVE

To describe successful surgical treatment of bilateral mucocele in an American Miniature horse using a single bone flap to approach right and left paranasal sinuses simultaneously.

STUDY DESIGN

Clinical report.

ANIMAL

A castrated 6-year-old American Miniature Horse with a bilateral mucocele of the paranasal sinuses.

METHODS

A single bilateral frontonasal sinus flap was used in a standing procedure to access the left and right conchofrontal sinuses simultaneously to remove the mucous contents and to establish permanent drainage into the nasal cavities.

RESULTS

The novel procedure used in this horse allowed excellent access to right and left paranasal sinuses simultaneously and completely resolved nasal discharge and difficulty breathing.

CONCLUSIONS

A single, bilateral frontonasal sinus flap can be used successfully as a standing procedure to treat bilateral sinonasal disease in horses.

Liver lobe torsion in six horses

CASE DESCRIPTION

6 horses were determined to have torsion of a liver lobe at 4 referral institutions over a 21-year period.

CLINICAL FINDINGS

Clinical findings were nonspecific but often included signs of marked inflammation. Two of the 6 horses were examined because of colic, and 2 were assessed because of peritonitis that failed to respond to treatment; the remaining 2 horses were examined because of nonspecific clinical signs that included inappetence, lethargy, and weight loss. The results of laboratory tests were widely variable, and values for liver enzyme activities were typically within reference limits or only mildly increased. Most affected horses had markedly increased peritoneal nucleated cell counts.

TREATMENT AND OUTCOME

Exploratory laparotomy and resection of the affected liver lobe was performed in 5 horses. Three of those patients survived to discharge.

CLINICAL RELEVANCE

Results suggested that diagnosis of liver lobe torsion in horses may be difficult because clinical signs and results of laboratory testing are nonspecific and variable. Most affected horses had markedly abnormal peritoneal fluid. The prognosis for hepatic lobe torsion can be good, and early surgical correction is expected to improve outcome.

Effects of ischemia and reperfusion on production of nitrotyrosine, activation of eosinophils, and apoptosis in the large colonic mucosa of horses

OBJECTIVE

To assess the effects of ischemia and reperfusion on indicators of oxidative stress, activation of eosinophils, and apoptosis in the large colonic mucosa of horses.

ANIMALS

40 horses.

PROCEDURES

In 1 or two 20-cm-long segments of the pelvic flexure, ischemia was induced for 1 or 2 hours followed by no reperfusion or 30 minutes and 18 hours of reperfusion in anesthetized horses. Mucosal specimens were collected before (controls; n = 20 horses) and after each period of ischemia, and full-thickness tissue samples were collected after each period of reperfusion. Sections of colonic tissues were stained for histomorphometric analysis or assessment of eosinophil accumulation. Nitrotyrosine was identified immunohistochemically, and severity of apoptosis was determined via the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling method.

RESULTS

Numbers of mucosal eosinophils were similar before induction of ischemia, after ischemia, and after ischemia-reperfusion. Eosinophil nitrotyrosine production increased significantly during ischemia and continued through 30 minutes of reperfusion; production was decreased at 18 hours of reperfusion but remained greater than that of the controls. In other leukocytes, nitrotyrosine generation peaked at 1 hour of ischemia and again at 18 hours of reperfusion. Compared with control findings, epithelial apoptosis increased gradually at 1 through 2 hours of ischemia with no further progression after reperfusion.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that resident eosinophils in the large colon of horses react to mucosal injury from ischemia and reperfusion and may undergo oxidative stress under those conditions. Epithelial apoptosis could contribute to tissue damage.

Mucosal injury and inflammatory cells in response to brief ischaemia and reperfusion in the equine large colon

REASON FOR PERFORMING STUDY

Intestinal ischaemia and reperfusion (I/R) can activate inflammatory cells in the equine colon, although effects on different types of inflammatory cells have received little attention.

OBJECTIVES

To assess early mucosal injury, the reaction of mucosal neutrophils, eosinophils, mast cells and macrophages, and cyclooxygenase (COX)-1 and -2 expression in response to I/R in the equine large colon.

METHODS

Large colon ischaemia was induced for 1 h (1hI) followed by 4 h of reperfusion in 6 horses, and mucosal biopsies were sampled before and after ischaemia, and after 1, 2 and 4 h of reperfusion. Semithin sections (500 nm) of epon-embedded biopsies were stained with toluidine blue for histomorphometric evaluation. The number and distribution of mucosal macrophages (CD163), neutrophils (calprotectin), eosinophils (LUNA) and mast cells (toluidine blue) were determined, and mucosal COX-1 and -2 expression was identified.

RESULTS

Ischaemia caused epithelial cell and nuclear swelling (mean ± s.e. nuclear width; control: 2.7 ± 0.2 µm vs. 1hI: 4.2 ± 0.2 µm; P<0.01), subepithelial oedema (control: 0.2 ± 0.1 µm vs. 1hI: 3.2 ± 0.2 µm; P<0.01) and increased epithelial apoptosis (control: 14.3 ± 4.1 apoptotic cells/mm mucosa vs. 1hI: 60.4 ± 14.0 apoptotic cells/mm mucosa; P<0.01). COX-2 expression (P<0.01) was evident after ischaemia. Reperfusion caused paracellular fluid accumulation (control: 0.9 ± 0.1 µm vs. 1hI: 0.6 ± 0.6 µm vs. 1hI + 4hR: 1.6 ± 0.2 µm; P<0.05). Epithelial repair started at 1 h of reperfusion (P<0.001), followed by migration of neutrophils into the mucosa after 2 h (control: 72.3 ± 18.4 cells/mm(2) mucosa vs. 1hI + 2hR: 1149.9 ± 220.6 cells/mm(2) mucosa; P<0.01). Mucosal eosinophils, mast cells and macrophages did not increase in numbers but were activated.

CONCLUSIONS

Epithelial injury and COX-2 expression caused by short-term hypoxia were followed by intense inflammation associated with epithelial repair during reperfusion.

POTENTIAL RELEVANCE

Equine colonic mucosa subjected to a brief period of ischaemia can repair during reperfusion, despite increased mucosal inflammation.

Ultrastructural changes in the equine colonic mucosa after ischaemia and reperfusion

REASON FOR PERFORMING STUDY

Ultrastructural changes in the epithelium can provide information on early changes in barrier properties, repair and inflammation in equine colon after ischaemia and reperfusion (I/R).

OBJECTIVES

To describe the morphology and ultrastructure of the epithelium in equine large colonic mucosa after I/R, and the response of inflammatory cells to injury.

METHODS

Ischaemia was induced for 1 h followed by 4 h of reperfusion in a 40 cm segment of the pelvic flexure in 6 horses. Mucosal biopsies before and after ischaemia, and after 1, 2 and 4 h of reperfusion were fixed in glutaraldehyde/paraformaldehyde and osmium tetroxide, and embedded in epon. Morphological and ultrastructural changes were evaluated in toluidine blue-stained semithin sections by light microscopy and in thin sections stained with uranyl acetate/lead citrate by transmission electron microscopy.

RESULTS

Ischaemia caused swelling of epithelial cells and their organelles, opening of tight junctions, detachment from the basement membrane, early apoptosis and single cell necrosis. Autophagy was a prominent feature in epithelial cells after ischaemia. Reperfusion was characterised by apoptosis, epithelial regeneration and restoration of apical cell junctions. Phagocytic-like vacuoles containing cellular debris and bacteria were evident in epithelial cells after reperfusion. Paracellular and subepithelial clefts formed, accompanied by infiltration of neutrophils, lymphocytes and eosinophils into the epithelium. Subepithelial macrophages and luminal neutrophils had increased phagocytic activity.

CONCLUSIONS

Ischaemia caused ultrastructural damage to the colonic epithelium, but epithelial cells recovered during reperfusion.

POTENTIAL RELEVANCE

Transmission electron microscopy can demonstrate subtle ultrastructural damage to epithelial cells and evidence of recovery after I/R in equine colon.

Expression of cyclooxygenase-1 and -2 in the left dorsal colon after different durations of ischemia and reperfusion in horses

OBJECTIVE-To identify expression and localization of cyclooxygenase (COX)-1 and COX-2 in healthy and ischemic-injured left dorsal colon of horses. SAMPLE POPULATION-Left dorsal colon tissue samples from 40 horses. PROCEDURES-Tissue samples that were used in several related studies on ischemia and reperfusion were evaluated. Samples were collected during anesthesia, before induction of ischemia, and following 1 hour of ischemia, 1 hour of ischemia and 30 minutes of reperfusion, 2 hours of ischemia, 2 hours of ischemia and 30 minutes of reperfusion, and 2 hours of ischemia and 18 hours of reperfusion. Histomorphometric analyses were performed to characterize morphological injury. Immunohistochemical analyses were performed to characterize expression and localization of COX-1 and COX-2. RESULTS-COX-1 and COX-2 were expressed in control tissues before ischemia was induced, predominantly in cells in the lamina propria. Ischemic injury significantly increased expression of COX-2 in epithelial cells on the colonic surface and in crypts. A similar significant increase of COX-1 expression was seen in the epithelial cells. CONCLUSIONS AND CLINICAL RELEVANCE-On the basis of information on the role of COX-2, upregulation of COX-2 in surface epithelium and crypt cells following ischemic injury in equine colon may represent an early step in the repair process.

Total and partial ovariohysterectomy in seven mares

REASONS FOR PERFORMING STUDY

Ovariohysterectomy appears to have a low mortality rate in mares, but the procedure needs to be reviewed because of the high risk of life-threatening complications.

HYPOTHESIS

That ovariohysterectomy can be effective treatment for a variety of uterine diseases in mares and carries a good prognosis.

METHODS

Diagnosis, clinical data, surgical technique, post operative care, complications and outcome were recorded from medical records of 7 mares that underwent total (6) and partial (1) ovariohysterectomy at the University of Illinois from 1994 to 2001.

RESULTS

The indications for ovariohysterectomy were chronic pyometra (4 mares), chronic uterine torsion (n = 2) and chronic intramural haematoma (n = 1). Surgical exposure was difficult but was improved by traction on stay sutures and right-angled clamps. In some cases, application of the TA-90 autosuture instrument as a right-angled clamp to the caudal part of the uterus improved access to the uterine stump. The most common post operative complications were decreased faecal output, decreased intestinal sounds (4 mares) and mild abdominal pain (2). Two mares had mild to moderate incisional infections. Other previously reported complications, such as haemorrhage, septic peritonitis, uterine stump infection or necrosis, and diarrhoea, did not occur. All mares survived over follow-up periods of 6 months to 5 years and were used for riding (6 mares) and embryo transfer (1 mare, after partial ovariohysterectomy).

CONCLUSIONS AND POTENTIAL RELEVANCE

According to this study, the prognosis for mares after ovariohysterectomy appears to be good, despite the technical difficulties of the procedure. The prevalence of life-threatening complications can be lower than reported.

Short-term survival after surgery for epiploic foramen entrapment compared with other strangulating diseases of the small intestine in horses

REASONS FOR PERFORMING STUDY

Epiploic foramen entrapment (EFE) is one of the more common causes of colic in horses, but recent reports suggest a poor prognosis after surgical treatment.

HYPOTHESIS

That EFE has a good prognosis compared with other small intestinal strangulating lesions.

METHODS

Surgical findings, surgical procedures and short-term outcome were recorded for 157 horses that underwent surgery for strangulating lesions of the small intestine at the University of Illinois from 1994 to 2003. Horses were assigned to 3 groups for comparison; those with EFE, strangulation by lipoma and miscellaneous strangulating lesions. A logistic regression model and Monte Carlo tests of the binomial proportions were used to examine survival rates. The Kruskal-Wallis test was used to determine differences in usage of surgical treatments. Measurements of length and viability indices were analysed using a one-way analysis of variance followed by Tukey's HSD test, and viability scores were analysed using an exact Kruskal-Wallis test. Significance was set at P < 0.05.

RESULTS

Horses with EFE were significantly more likely to be discharged (95%) than those with the other conditions (P < 0.05). The proportion of horses with ileal involvement was greater in horses with EFE than in the other 2 groups (P < 0.05), although this did not affect outcome. The distributions of viability grades for EFE and lipoma differed significantly (P < 0.05).

CONCLUSIONS

The prognosis for horses that had surgery at this hospital for EFE was better than for those with the other conditions, although the greater proportion of horses with EFE with ileal involvement could influence outcome. Therefore, surgeons must consider ways of improving jejunocaecostomy and determining when bowel is viable, the latter to avoid jejunocaecostomy.

Effects of flunixin meglumine on recovery of colonic mucosa from ischemia in horses

OBJECTIVE

To examine the effects of flunixin meglumine (FM) on recovery of colonic mucosa from experimentally induced ischemia in horses.

ANIMALS

14 research horses.

PROCEDURES

Ischemia was induced in the colons of anesthetized horses for 2 hours. Afterward, horses received saline (0.9% NaCl) solution (12 mL, IV, q 12 h; n = 7) or FM (1.1 mg/kg, IV, q 12 h; 7) and were allowed to recover for 18 hours after termination of the ischemic event. Postoperative pain scores were recorded every 4 hours throughout the recovery period. At the end of the recovery period, horses were anesthetized, and ischemic and nonischemic segments of colonic mucosa were harvested for histologic evaluation, western blot analysis, and in vitro assessment of transepithelial electric resistance (TER) and transmucosal flux of tritium-labeled (3H-) mannitol. Horses were then euthanatized.

RESULTS

Flunixin meglumine significantly lowered pain scores at the first postoperative recording. There were no significant differences between treatment with saline solution and FM in any of the measurements for TER, 3H-mannitol flux, histomorphometric variables, neutrophil infiltration (detected via calprotectin immunostaining), and expressions of cyclooxygenase-1 and -2. After both treatments, TER declined significantly in nonischemic tissues in vitro, whereas it increased significantly in ischemic-injured tissues.

CONCLUSIONS AND CLINICAL RELEVANCE

Flunixin meglumine did not affect recovery of equine colonic mucosa from ischemic injury, and continued use in horses with colonic ischemia is therefore justified.

Epidemiologic analysis of nosocomial Salmonella infections in hospitalized horses

OBJECTIVE

To examine the relationship between abdominal surgery and nosocomial Salmonella infections and the relationship between high caseload in combination with abdominal surgery and nosocomial Salmonella infections in hospitalized horses with signs of gastrointestinal tract disease.

ANIMALS

140 horses.

DESIGN

Case-control study.

PROCEDURES

To accomplish the first objective, 1 to 4 control horses were matched with each nosocomial case horse on the basis of admission date of a primary case horse. The frequency of abdominal surgery and other investigated exposure factors were compared between nosocomial case horses and control horses. For the second objective, 4 control horses were matched with each nosocomial case horse on the basis of year of admission. The frequency of high caseload (>or=26 inpatients), abdominal surgery, and other factors was compared between nosocomial case horses and control horses.

RESULTS

The odds of nosocomial Salmonella infection were 8 times as high (odds ratio=8.2; 95% confidence interval=1.11, 60.24) in horses that underwent abdominal surgery, compared with the odds for horses that did not undergo surgery. High caseload alone or in combination with abdominal surgery was not associated with increased risk of nosocomial Salmonella infection.

CONCLUSIONS AND CLINICAL RELEVANCE

Abdominal surgery was identified as a risk factor for nosocomial Salmonella infections in horses. Horses that undergo abdominal surgery require enhanced infection control and preventative care. Risk of nosocomial Salmonella infections may be reduced by implementation of biosecurity measures (such as the use of plastic boots, gloves, and footbaths) immediately after surgery.

Immunohistochemical characterization and quantitative analysis of neurons in the myenteric plexus of the equine intestine

The present study was performed on whole-mount preparations to investigate the chemical neuroanatomy of the equine myenteric plexus throughout its distribution in the intestinal wall. The objective was to quantify neurons of the myenteric plexus, especially the predominant cholinergic and nitrergic subpopulations. Furthermore, we investigated the distribution of vasoactive intestinal polypeptide and the calcium-binding protein calretinin. Samples from different defined areas of the small intestine and the flexura pelvina were taken from 15 adult horses. After fixation and preparation of the tissue, immunofluorescence labeling was performed on free floating whole-mounts. Additionally, samples used for neuropeptide staining were incubated with colchicine to reveal the neuropeptide distribution within the neuronal soma. The evaluation was routinely accomplished using confocal laser-scanning microscopy. For quantitative and qualitative analysis, the pan-neuronal marker anti-HuC/D was applied in combination with the detection of the marker enzymes for cholinergic neurons and nitrergic nerve cells. Quantitative data revealed that the cholinergic subpopulation is larger than the nitrergic one in several different locations of the small intestine. On the contrary, the nitrergic neurons outnumber the cholinergic neurons in the flexura pelvina of the large colon. Furthermore, ganglia are more numerous in the small intestine compared with the large colon, but ganglion sizes are bigger in the large colon. However, comparison of the entire population of neurons in the different locations of the gut showed no difference. The present study adds further data on the chemoarchitecture of the myenteric plexus which might facilitate the understanding of several gastrointestinal disorders in the horse.

The effects of Strongylus vulgaris parasitism on eosinophil distribution and accumulation in equine large intestinal mucosa

REASONS FOR PERFORMING STUDY

Eosinophilic granulocytes have been associated with parasite or immune-mediated diseases, but their functions in other disease processes remain unclear. Cause and timing of eosinophil migration into the equine gastrointestinal mucosa are also unknown.

OBJECTIVE

To determine the effects of intestinal parasitism on eosinophils in equine large intestinal mucosa.

METHODS

Large intestinal mucosal samples were collected from horses and ponies (n = 16) from the general veterinary hospital population, ponies (n = 3) raised in a parasite-free environment, ponies experimentally infected with 500 infective Strongylus vulgaris larvae and treated with a proprietary anthelmintic drug (n = 14), and a similar group of ponies (n = 7) that received no anthelmintic treatment. Total eosinophil counts and eosinophil distribution in the mucosa were determined by histological examination. A mixed model analysis was performed and appropriate Bonferroni adjusted P values used for each family of comparisons. P<0.05 was considered significant.

RESULTS

There was no difference in large intestinal mucosal eosinophil counts and eosinophil distribution between ponies infected with S. vulgaris and those raised in a parasite-free environment. Experimental infection with S. vulgaris, with or without subsequent anthelmintic treatment, did not change eosinophil counts, and counts were similar to those for horses from the general population.

CONCLUSIONS

Migration of eosinophils to the equine large intestinal mucosa appears to be independent of exposure to parasites. Large intestinal mucosal eosinophils may have more functions in addition to their role in defence against parasites.

Effect of suckling an isotonic solution of sodium acetate, sodium bicarbonate, or sodium chloride on abomasal emptying rate and luminal pH in calves

OBJECTIVES

To compare abomasal emptying rates in calves after suckling milk replacer or 3 common orally administered electrolyte solution components.

ANIMALS

5 male calves < 35 days of age.

PROCEDURES

Calves with a cannula fitted in the abomasal body were fed 2 L of milk replacer with or without parenteral administration of atropine (0.01 mg/kg, i.v., then 0.02 mg/ kg, s.c., q 30 min) or isotonic (150 mM) solutions of sodium acetate, NaHCO(3), or NaCl in a randomized crossover design. Abomasal emptying rates were determined via scintigraphy, acetaminophen absorption, ultrasonography, and change in abomasal luminal pH.

RESULTS

Scintigraphic half-emptying time, time of maximal plasma acetaminophen concentration, ultrasonographic half-emptying time, and pH return time indicated similar abomasal emptying rates following suckling of isotonic sodium acetate, NaHCO(3), and NaCl solutions, whereas the emptying rate of milk replacer was significantly slower. Mean maximal abomasal luminal pH was highest following suckling of NaHCO(3) (pH(max)=7.85) and lowest following suckling of NaCl (pH(max)=4.52); sodium acetate (pH(max)=6.59) and milk replacer (pH(max)=5.84) yielded intermediate pH values.

CONCLUSIONS AND CLINICAL RELEVANCE

Isotonic solutions of sodium acetate, NaHCO(3), and NaCl were rapidly emptied from the abomasum but varied markedly in their ability to alkalinize the abomasum. Sodium bicarbonate-containing orally administered electrolyte solution might increase the frequency of infection or severity of clinical disease in diarrheic calves treated for dehydration by causing prolonged abomasal alkalinization.

Glucosamine promotes chondrogenic phenotype in both chondrocytes and mesenchymal stem cells and inhibits MMP-13 expression and matrix degradation

OBJECTIVES

Glucosamine (GlcN), a natural amino monosaccharide, is a constituent of glycosaminoglycans (GAGs) found in hyaline cartilage. GlcN salts constitute a new class of nutraceutical components with putative chondroprotective activity, which may target chondrocytes as well as chondroprogenitors cells, such as mesenchymal stem cells (MSCs), during cartilage turnover and repair. In the present study, we examined the effects of GlcN on chondrogenesis of human MSCs (hMSCs) and the phenotype of normal and osteoarthritic human articular chondrocytes, using an in vitro pellet culture model maintained in a defined medium.

METHODS

hMSCs and normal and osteoarthritic human chondrocytes grown as pellet cultures, stimulated or not with interleukin-1beta (IL-1beta), were treated with varying doses of GlcN. Expression of cartilage matrix genes and cartilage degrading enzymes was determined by semiquantitative and quantitative real-time reverse transcription polymerase chain reaction (RT-PCR), and by histological staining of cartilage markers, as well as sulfated GAG (sGAG) analysis and Western blotting.

RESULTS

Chondrocytes grown in the presence of serum for 11 days showed decreased expression of the cartilage matrix genes, collagen type II (collagen II) and aggrecan, as early as day 3, which was reversed with GlcN treatment by day 11. Both hMSCs and chondrocytes grown as pellet cultures in defined medium and treated with 100 microM GlcN exhibited enhanced expression of collagen II and aggrecan as well as increased content of sGAG, when compared to control untreated pellets. However, high doses of GlcN (10-20mM) were inhibitory. GlcN treatment partially blocked IL-1beta mediated downregulation of collagen II and aggrecan expression and inhibited expression of the matrix degrading enzyme, matrix metalloproteinase 13 (MMP-13), in both chondrocytes and hMSCs undergoing chondrogenesis.

CONCLUSIONS

These observations suggest that GlcN treatment enhances hMSC chondrogenesis and maintains cartilage matrix gene expression in chondrocytes, which may account for some of the reported chondroprotective properties of GlcN on cartilage.