Single-incision drilling technique to achieve hemiepiphysiodesis of the distal metacarpus - complications and outcome in 207 foals with metacarpophalangeal varus deformities.

OBJECTIVE: To report the outcome of foals treated for metacarpophalangeal varus deformity with a single-incision drilling technique for hemiepiphysiodesis of the distal lateral metacarpal physis. STUDY DESIGN: Retrospective case-control cohort study. ANIMALS: Thoroughbred foals (n = 207), 171 age- and sex-matched maternal siblings. METHODS: Medical records (2017-2020) were reviewed for signalment, limb(s) treated, location of the surgery, and any reported complications. Follow-up radiographs obtained for the yearling sale were assessed for abnormalities. Horses were matched to maternal siblings using an online database. Sales and racing performance data were compared between cohorts. RESULTS: The average age at the time of surgery was 97 days. The treated limb was the left front in 52, right front in 31, both fronts in 119, unknown in 5. Three horses developed calcinosis circumscripta lesions adjacent to the physis, which were removed successfully. No radiographic abnormalities associated with the surgery site were detected on yearling prepurchase radiographs. There were no differences in sales and racing performance data between treated horses and maternal controls. CONCLUSION: Hemiepiphysiodesis is a safe and effective treatment for metacarpophalangeal varus deformities in foals. No negative effect on sales or racing performance was identified. CLINICAL SIGNIFICANCE: This technique avoids risks, costs, and the need for second surgery associated with an orthopedic implant. The surgeon should be aware of the potential for development of a calcinosis circumscripta lesion with this technique.

Arthroscopic removal of osteochondral fragments located within the condylar fossa of the third metacarpus/metatarsus in Thoroughbred yearlings.

OBJECTIVE: To describe an arthroscopic technique for the removal of osteochondral fragments located within the condylar fossa of the third metacarpal/tarsal bone. STUDY DESIGN: Retrospective study. ANIMALS: Thoroughbred yearlings (n = 11). METHODS: Osteochondral fragments located within the condylar fossa of the third metacarpal/tarsal bone identified during presale radiographic examination were removed via arthroscopy, assisted with ultrasonography in select cases. Complete fragment removal was confirmed by intraoperative radiography. RESULTS: Fragments were successfully removed using rongeurs following dissection of soft tissue attachments using a bipolar radiofrequency probe. No postoperative complications occurred. CONCLUSIONS: An ipsilateral arthroscopic and instrument portal coupled with ultrasound assistance and a radiofrequency probe allowed for successful removal of fragments located within the condylar fossa of the third metacarpal/tarsal bone. The technique allowed for the removal of the unstable osteochondral fragment and associated physical debris. CLINICAL SIGNIFICANCE: The described surgical technique enables the removal of osteochondral fragments located within the condylar fossa of the third metacarpal/tarsal bone with minimal disruption to the surrounding soft tissues.

Survival and racing performance after surgical treatment of rib fractures in foals.

OBJECTIVE: To evaluate the short and long-term outcomes of foals treated surgically for fractured ribs and variables that may affect outcome. STUDY DESIGN: Retrospective. ANIMALS: Seventy-three equine neonates with surgically repaired fractured ribs. METHODS: Medical records were reviewed to include sex, breed, the side of thorax affected, number of ribs fractured, co-morbidities directly associated with rib fracture, and surgical technique used. Short-term outcome was defined as survival to discharge. Long-term outcome was whether or not they started a race. Race records of maternal siblings were obtained for comparison. RESULTS: Seventy-three neonates underwent surgery for fractured ribs. Fifty-seven neonates (78%) survived to discharge from the hospital. Rib fractures were more commonly observed in colts and in the left hemithorax (61% and 57%, respectively). Sex, side affected, number of ribs fractured, co-morbidities, number of ribs repaired, and surgical technique did not affect the short- or long-term outcomes. Thirty-five of 57 (61%) foals treated surgically for rib fractures that survived to discharge started a race compared to 173 of 257 (67%) of maternal siblings that raced. CONCLUSIONS: Short- and long-term outcome were not affected by co-morbidities, surgical technique, or number of fractured ribs. CLINICAL SIGNIFICANCE: Neonates with surgically repaired fractured ribs had a good prognosis for survival and and those that survived had a similar chances of starting a race compared to maternal siblings.

Hand-assisted laparoscopic cystotomy for cystic calculus removal in male horses (3 cases).

A technique for hand-assisted laparoscopic removal of cystic calculi in male horses is described. Three cystic calculi ranging from 5 to 10 cm in diameter were removed successfully using bilateral para-inguinal laparoscopic portals assisted by a human hand within the abdomen, effectively sealing the midline incision. Long-term follow-up information obtained from referring veterinarians and owners indicated that the patients returned to their previous activity level and had no recurrence of clinical signs in the following 6 to 12 months. Key clinical message: Hand-assisted recumbent laparoscopy is a satisfactory surgical technique for removal of cystic calculi in horses which cannot be operated on standing or whose body condition would make the parainguinal approach difficult.

Cystotomie laparoscopique aidée de mains pour le retrait de calculs cystiques chez des chevaux mâles (3 cas). Une technique pour le retrait de calculs cystiques par laparoscopie aidée de mains chez des chevaux mâles est décrite. Trois calculs cystiques variant de 5 à 10 cm de diamètre furent retirés avec succès en utilisant des entrées laparoscopiques bilatérales para-inguinales aidées d'une main humaine à l'intérieur de l'abdomen, scellant avec succès l'incision sur la ligne médiane. Les informations sur le suivi à long terme obtenues des vétérinaires référant et des propriétaires indiquaient que les patients étaient retournés à leur niveau d'activité antérieur et qu'aucune récurrence des signes cliniques ne fut notée dans les 6 à 12 mois suivants.Message clinique clé:La laparoscopie couchée aidée de mains est une technique chirurgicale satisfaisante pour le retrait de calculs cystiques chez des chevaux qui ne peuvent être opérés debout ou dont la condition corporelle rendrait l'approche parainguinale difficile.(Traduit par Dr Serge Messier).

Macrophage Activation in the Synovium of Healthy and Osteoarthritic Equine Joints.

Synovitis is a major component of osteoarthritis and is driven primarily by macrophages. Synovial macrophages are crucial for joint homeostasis (M2-like phenotype), but induce inflammation (M1-like) when regulatory functions become overwhelmed. Macrophage phenotypes in synovium from osteoarthritic and healthy joints are poorly characterized; however, comparative knowledge of their phenotypes during health and disease is paramount for developing targeted treatments. This study compared patterns of macrophage activation in healthy and osteoarthritic equine synovium and correlated histology with cytokine/chemokine profiles in synovial fluid. Synovial histology and immunohistochemistry for M1-like (CD86), M2-like (CD206, IL-10), and pan macrophage (CD14) markers were performed on biopsies from 29 healthy and 26 osteoarthritic equine joints. Synovial fluid cytokines (MCP-1, IL-10, PGE2, IL-1ß, IL-6, TNF-α, IL-1ra) and growth factors (GM-CSF, SDF-1α+ß, IGF-1, and FGF-2) were quantified. Macrophage phenotypes were not as clearly defined in vivo as they are in vitro. All macrophage markers were expressed with minimal differences between OA and normal joints. Expression for all markers increased proportionate to synovial inflammation, especially CD86. Synovial fluid MCP-1 was higher in osteoarthritic joints while SDF-1 and IL-10 were lower, and PGE2 concentrations did not differ between groups. Increased CD14/CD86/CD206/IL-10 expression was associated with synovial hyperplasia, consistent with macrophage recruitment and activation in response to injury. Lower synovial fluid IL-10 could suggest that homeostatic mechanisms from synovial macrophages became overwhelmed preventing inflammation resolution, resulting in chronic inflammation and OA. Further investigations into mechanisms of arthritis resolution are warranted. Developing pro-resolving therapies may provide superior results in the treatment of OA.

Radiographic Description of a Bone Exostosis Lesion on the Caudal Aspect of the Proximal Tibia in Three Thoroughbred Yearlings (2014-2019).

This manuscript describes exostosis lesions originating from the caudal aspect of the proximal tibia identified in three Thoroughbred yearlings as part of the routine review of presale radiographic images. These lesions are hypothesized to be osteochondromas. The identification of bony exostoses on the proximal tibia has not been reported before in current literature. As they have not been described, the future effect on performance or soundness is unknown. Although these cases were not lame at the time of detection, the future growth of the lesion and its impact on surrounding soft tissues is unknown.

Single-incision percutaneous drilling technique to achieve hemiepiphysiodesis of the distal metacarpus in foals with metacarpophalangeal varus deformities.

OBJECTIVE: To describe a drilling technique for hemiepiphysiodesis of the distal lateral metacarpal physis and report the outcome of treated foals. STUDY DESIGN: Retrospective case series. SAMPLE POPULATION: Eleven thoroughbred foals. METHODS: While horses were under general anesthesia, the lateral aspect of the distal metacarpal physis was approached through a single small incision by using a power drill. The drill bit was placed at the level of the physis under radiographic guidance. A 4.5-mm drill bit was passed several times through the lateral growth plate to remove the cartilage in a fan-like pattern. Postoperative outcomes consisted of clinical assessment and farm manager/owner satisfaction. Cosmetics and radiographic appearance of the surgical site were assessed when the horses were yearlings. RESULTS: The procedure was performed in 16 limbs of 11 thoroughbred foals with a median age of 113.5 days (range, 90-129). Median age at postoperative follow-up was 422 days (range, 366 to 452). The procedure stopped the progression of a metacarpophalangeal varus deformity in all the limbs treated, determined by visual clinical evaluation and farm manager's satisfaction with subjectively excellent radiographic images and cosmetic outcomes at yearling age. CONCLUSION: Physis ablation was consistently achieved in these 11 foals with developing growth deformities of the distal metacarpus. CLINICAL SIGNIFICANCE: This drilling technique may offer a minimally invasive, safe, and simple technique to manage distal limb conformation in foals without placement of implants. Additional quantitative data are required to assess its effectiveness relative to other options.

Description of a rare osteochondrosis lesion of the medial aspect of the distal intermediate ridge of the tibia in seven Thoroughbred horses (2008-2018).

Osteochondritis dissecans (OCD) of the distal intermediate ridge of the tibia (DIRT) is commonly identified on either the lateral to medial (LM) or dorso45°medial-plantarolateral oblique (D45M-PLO) projection of the tarsus. This manuscript describes a retrospective case series out of Hagyard Equine Medical Institute, for which medical records and radiographic projections of the tarsus were reviewed, consistent with Keeneland's repository requirements. This original investigation identified seven yearling Thoroughbred horses between 2008 and 2018 with radiographic signs of atypical osteochondrosis lesions within the tarsus. The atypical lesions, originating along the medial margin of the distal intermediate ridge of the tibia, were initially only diagnosed on the dorso10°lateral-plantaromedial (D10L-PMO) projection and were overlooked on the LM and D45M-PLO views. Following the diagnosis of osteochondrosis in these seven cases, the radiographs were reviewed and re-evaluated, but osteochondrosis and/or fragmentation could not be definitively diagnosed on the LM and/or D45M-PLO projections alone. Our findings highlight the importance of a complete radiographic study of the equine tarsus when screening horses for OCD lesions of the distal intermediate ridge of the tibia and that atypical DIRT lesions may go undetected if the D10L-PMO projection is not performed.

Ceratohyoidectomy in standing sedated horses.

OBJECTIVE: To investigate the feasibility and complications associated with ceratohyoidectomy (CHE) in standing sedated horses unaffected (experimental horses) and standing sedated horses affected (clinical cases) with temporohyoid osteoarthropathy (THO). STUDY DESIGN: Case series. ANIMALS: Six experimental horses and four clinical cases. METHODS: Standing CHE was performed in six experimental horses euthanized 30 minutes (n = 3) and 7 days (n = 3) postoperatively. The four clinical cases were presented because of central facial nerve paralysis (n = 3), vestibular ataxia (n = 3), auricular hemorrhage (n = 2), quidding (n = 1), and oesophageal impaction (n = 1). Evolution was assessed by clinical examination during hospitalization and later by telephone interviews for the clinical cases. RESULTS: The procedure was successfully performed in all horses. Experimental horses did not show any short-term postoperative complications. Hemorrhage was experienced intraoperatively in one of the clinical cases and was successfully managed with placement of hemostatic forceps. Vestibular ataxia and other symptoms of THO improved within days, but facial nerve paralysis did not improve until 9 days to 6 months after surgery. Follow-up ranged from 9 to 24 months. All clinical cases returned to performance, and client satisfaction was excellent. CONCLUSION: Ceratohyoidectomy was consistently feasible in standing sedated horses. The method did not result in postoperative complications and led to resolution of clinical signs associated with THO. CLINICAL SIGNIFICANCE: Standing CHE should be considered in horses affected with THO, especially when horses present with marked vestibular deficits and ataxia, to reduce risks associated with recovery from general anesthesia.

Cecal entrapment within the epiploic foramen in a mare.

An 11-year-old Thoroughbred mare with colic unresponsive to medical treatment underwent exploratory laparotomy. During surgery the cecum was found entrapped within the epiploic foramen from left to right. The entrapped cecum was reduced through the foramen by gentle traction. After reduction of the cecum, rupture of the portal vein was detected. Loss of a large amount of blood prompted euthanasia during surgery.

Encapsulation du cæcum dans le foramen omental chez une jument. Une jument Thoroughbred âgée de 11 ans atteinte de coliques ne répondant pas au traitement médical a subi une laparatomie exploratoire. Durant la chirurgie, le cæcum a été trouvé encapsulé dans le foramen omental de gauche à droite. Le cæcum encapsulé a été réduit par le foramen à l'aide d'une légère traction. Après la réduction du cæcum, la rupture de la veine porte a été détectée. La perte d'une grande quantité de sang a entraîné l'euthanasie durant la chirurgie.(Traduit par Isabelle Vallières).

Internal fixation of fractured ribs in neonatal foals with nylon cable tie using a modified technique.

Nylon cable tie has been shown to be an effective and economical method for fixing fractured ribs in the neonatal foal. This article describes a modification of the previously described technique. Under general anesthesia, the fractured ribs were exposed and a hole was drilled in the dorsal and ventral fragments. The fracture was not reduced, leaving the fragments overriding each other. The nylon cable tie was passed through the hole in the dorsal fragment from the external surface of the rib. The free end of the cable tie was then passed through the hole in the ventral fragment from the external surface of the rib and the tie was tightened. This technique was used in 4 neonatal foals with no complications. The modification of the original technique represents a method to minimize soft tissue trauma, implant failure, and complications.

Technique modifiée pour la fixation interne de fractures de côtes chez le poulain nouveau-né avec des attaches de câbles en nylon. Cet article décrit une technique pour réparer les fractures de côtes chez le poulain nouveau-né en utilisant des attaches de câbles en nylon. Sous anesthésie générale, une incision verticale a été faite et les côtes fracturées ont été exposées. Une mèche de perceuse a été utilisée pour faire des trous dans les fragments dorsaux et ventraux des côtes fracturées, approximativement 5 à 10 mm de la ligne de fracture. Le câble a été introduit dans le trou du fragment dorsal et ensuite dans le trou du fragment ventral. Les attaches de câbles ont été resserrées. Les fractures n'ont pas été réduites et les fragments dorsaux chevauchaient les fragments ventraux. Cette technique a été utilisée sans complications chez quatre poulains nouveau-nés.(Traduit par les auteurs).

Standing placement of transphyseal screw in the distal radius in 8 Thoroughbred yearlings.

This retrospective study describes placement of distal radial transphyseal screws in Thoroughbred yearlings with carpal varus deformities while standing, and identifes short- and long-term complications following the procedure. Data gathered from 2009 to 2013 identified 8 yearlings that met the inclusion criteria. Horses were sedated intravenously and a single 4.5-mm cortical screw was placed in the distal lateral radial physis following application of local anesthetic and surgical preparation of a pre-placed hole. All horses were evaluated weekly after surgery and screw removal was performed standing and under sedation when correction of the angular limb deformity was achieved. The mean time for screw removal was 46 days. No short- or long-term complications were identified. Findings indicate that placing a single transphyseal screw in the lateral aspect of the distal radial physis with the horse standing is a viable option to treat varus angular limb deformity of the carpus in horses.

Placement debout d'une vis transphysaire dans le radius distal chez 8 Thoroughbred âgés d'un an. Cette étude rétrospective décrit le placement d'une vis transphysaire dans le radius distal de chevaux Thoroughbred âgés d'un an ayant des difformités du varus carpien, lorsqu'ils sont debout, et elle identifie les complications à court et à long terme après l'intervention. Les données recueillies de 2009 à 2013 ont identifié 8 chevaux âgés d'un an qui satisfaisaient aux critères d'inclusion. Les chevaux ont été mis sous sédation par intraveineuse et une seule vis corticale de 4,5 mm a été placée dans le cartilage diaphyso-éphysaire après l'application d'anesthésie locale et de la préparation chirurgicale d'un trou pratiqué au préalable. Tous les chevaux ont été évalués une fois par semaine après la chirurgie et l'enlèvement de la vis a été réalisé debout et sous sédation lorsque la correction de la difformité angulaire du membre a été obtenue. Le temps moyen de l'enlèvement des vis était de 46 jours. Aucune complication à court ou à long terme n'a été identifiée. Les résultats indiquent que le placement d'une seule vis transphysaire dans l'aspect latéral du cartilage diaphyso-éphysaire distal radial, lorsque le cheval se tient debout, est une option viable pour traiter la difformité angulaire de type varus du carpe chez les chevaux.(Traduit par Isabelle Vallières).

Endoscopic, transoral, reduction of epiglottic entrapment via wire snare technique.

OBJECTIVE: To describe the use of a wire snare technique for epiglottic entrapment. STUDY DESIGN: Case series. ANIMALS: Eight adult horses. METHODS: Under general anesthesia, a modified mouth gag was placed in the oropharynx. An endoscope was passed through the gag until there was adequate visualization of the entrapped epiglottis. The entrapping mucosa was grasped with bronchoesophageal forceps and pulled rostrally, releasing the epiglottis. A custom snare was passed down the bronchoesophageal forceps to encircle the redundant subepiglottic mucosa. Tension was applied to the entrapping mucosa via the forceps as the obstetric wire was tightened at the base and the redundant mucosa (aryepiglottic fold) was excised. RESULTS: The procedure was performed on 8 adult thoroughbred horses. Re-evaluation by endoscopy did not show entrapment in any horse and no horse developed complications or has had problems with performance. CONCLUSIONS: This technique is a minimally invasive, competitively priced and straightforward method for resection of entrapping subepiglottic mucosa in adult horses.

Ultrasound assisted arthroscopic approach for removal of basilar sesamoid fragments of the proximal sesamoid bones in horses.

OBJECTIVE: To describe an ultrasound assisted arthroscopic approach for removal of non-articular basilar sesamoid fragments in Thoroughbred yearlings. ANIMALS: Thoroughbred yearlings (n = 7). METHODS: Basilar sesamoid fragments identified during pre-sale radiographic examination were removed using a palmar/plantar arthroscopic approach to the fetlock joint and ultrasonographic guidance. Complete fragment removal was confirmed by ultrasonography and radiography. RESULTS: Basilar sesamoid fracture fragments were localized and removed successfully using rongeurs and a radiofrequency probe for soft tissue dissection of the fragment. Complete fragment removal was confirmed by ultrasonography and radiography. No intra- or postoperative complications occurred. At 6-8 months follow-up, no fragments or bony proliferation at the base of the sesamoid was observed. CONCLUSIONS: Ultrasonographic guidance can be used to facilitate localization, dissection, and confirmation of removal of basilar fragments of the proximal sesamoid bone.

Osteomyelitis of the patella in eight foals.

OBJECTIVE: To describe the characteristics of osteomyelitis lesions of the patella and to report short- and long-term outcome after treatment in 8 foals. STUDY DESIGN: Retrospective case series. ANIMALS: Foals (n = 8). METHODS: Medical records (2003-2007) and radiographs of foals that had osteomyelitis of the patella were reviewed. Inclusion criteria included clinical, radiographic, and surgical findings consistent with osteomyelitis of the patella, and a long-term follow-up of >15 months. Information acquired included signalment, hematologic and serum biochemical profile results, clinical and radiographic signs, surgical technique and perioperative treatment. Follow-up radiographs were evaluated and outcome was determined from veterinary examination, race records, and telephone questionnaire. RESULTS: Six foals survived long term (15 months-4 years); all had intralesional and systemic antimicrobial therapy, along with synovial lavage and antimicrobial medication. All were sound and achieved either yearling sales (n=3), show hunter or racing (2). Two foals died in the short term from renal failure and suppurative peritonitis secondary to cecal perforation, 1 remaining lame with suppurative osteonecrosis confirmed at necropsy. This foal was not administered intralesional antimicrobial therapy. CONCLUSIONS: Prompt medical and surgical therapy for osteomyelitis of the patella can result in a good prognosis for soundness and a potential athletic career. Concurrent septicemia or other systemic perinatal disease can result in prolonged therapy and delayed recovery.

Standing hand-assisted laparoscopic ovariectomy in 65 mares.

OBJECTIVE: To review the efficacy and safety of unilateral ovariectomy by use of a standing hand-assisted laparoscopic approach and evaluate the effect of ovary size on posttransection hemorrhage after application of a linear stapling device. STUDY DESIGN: Case series. ANIMALS: Horses (n=65) aged 2-20 years. METHODS: Medical records of mares that had ovariectomy performed by use of a standing hand-assisted laparoscopic approach were reviewed. Data retrieved were signalment, ovary removed (left, right), ovarian size, ovarian pathology, intraoperative and postoperative complications, and length of hospitalization. RESULTS: Mean ovarian diameter was 17 cm. Histopathology (52 mares) confirmed 41 granulosa cell tumors (79%), 8 ovarian cysts (15%), 1 teratoma (2%), and 2 ovaries (4%) without abnormalities. Hemorrhage was observed laparoscopically in 16 mares after transection of the mesovarium. Complications encountered during surgery included 1 mare collapsing in the stocks and 1 mare that hemorrhaged excessively from the incision. Postoperative complications included 2 cases of mild colic. Overall complication rate was 6%. CONCLUSIONS: All attempts to remove the target ovary were successful. The approach is safe for the mare, as complications encountered were similar to those recently reported for other approaches.

Hand-assisted laparoscopic removal of a nephroblastoma in a horse.

A 3-year-old Thoroughbred was presented for evaluation of hematuria post exercise. On physical examination, an enlarged kidney was identified, as well as serum biochemical abnormalities such as an elevated creatine kinase (CK) and hypoalbuminemia. The kidney was removed laparoscopically and a nephroblastoma was identified.

Comparison of surgical and medical treatment of 49 postpartum mares with presumptive or confirmed uterine tears.

OBJECTIVE: To determine outcome after medical or surgical treatment of postpartum mares with confirmed or presumptive uterine tears. STUDY DESIGN: Case series. METHODS: Postpartum mares were included if foaling had occurred within 7 days and uterine tear was confirmed surgically or, in medically treated mares, by palpation or presumed based on peritonitis. Information (age, breed; physical examination, laboratory and abdominocentesis findings; treatment, survival rates, length of hospital stay, treatments costs, and breeding performance after discharge) was obtained from the medical records (1990-2007). The influence of variables was compared between medical and surgical treatment, and between survivors and nonsurvivors. RESULTS: For 49 mares, survival was 75%, with no significant difference between medical (11/15; 73%) or surgical (26/34; 76%) treatment. Admission variables, treatment cost, duration of hospital stay, and likelihood of foaling after discharge were not significantly different between treatment groups. Nonsurvivors were significantly more likely to have gastric reflux, higher heart rate, anion gap, lower total CO(2), and leukocyte count, compared with survivors. Tears were significantly (P=.018) more likely to occur in the right uterine horn than in other parts of the uterus. CONCLUSIONS: Uterine tears occur more commonly in the uterine horns, more so the right horn, and survival is similar with surgical or medical treatment of uterine tears in postpartum mares. CLINICAL RELEVANCE: Medical treatment may be a reasonable alternative to surgical treatment for uterine tears, although the severity of tear that can resolve with medical treatment is unknown, and medical therapy can be as expensive as surgical treatment.

Diaphragmatic herniation in the horse: 31 cases from 2001-2006.

Diaphragmatic rent and visceral herniation in the horse is seldom diagnosed, but historically carries a poor prognosis. The objective of this study was to document the presentation and surgical management of all diaphragmatic rents as presented to 2 referral institutions over a 5-year period. A review of 31 cases demonstrated that even with advances in surgical management of abdominal and thoracic conditions, little has been done to change the prognosis for this condition. Success rate was 23% for all horses presented for colic and were ultimately diagnosed with a diaphragmatic hernia, and 46% for those cases for which surgical management was elected.

Surgical technique to repair grade IV rectal tears in post-parturient mares.

OBJECTIVE: To describe a surgical technique for repair of grade IV rectal tears after parturition in mares and to report outcome. STUDY DESIGN: Clinical report. ANIMALS: Horses (n=6) with grade IV rectal tears. METHODS: Mares were sedated and restrained in standing stocks. After caudal anesthesia and evacuation of feces from the rectum, the perineal region was aseptically prepared. Four stay sutures were placed through the external anal sphincter before vertical transection (12 o'clock). Caudal retraction of the tear was performed using Allis tissue forceps (5 mares) or stay sutures before accurate apposition of the tear margins with steel staples below the tissue forceps. The mucosal edges were then sharply dissected leaving approximately 5 mm edges which were apposed in a single layer (2-0 poliglecaprone 25) before stapler release. In 1 mare, the rectal tear was identified and apposed using a 2-layer hand-sutured closure. Systemic antibiotics and anti-inflammatory agents were administered postoperatively (5 mares) and standing abdominal lavage performed (3 mares). RESULTS: Four mares survived long term and subsequently became pregnant. Immediately after surgical repair, 1 mare was anesthetized for exploratory celiotomy and abdominal lavage but fractured her pelvis during recovery from anesthesia and was euthanatized. A 2nd mare was euthanatized after 72 h because of severe diffuse peritonitis; however, the repair was still intact. CONCLUSION: In standing mares, rectal tears can be exteriorized by prolapse through the anal sphincter after sphincterotomy and repaired in 2 layers with staples oversewn with a continuous suture pattern. CLINICAL RELEVANCE: Rectal tears occurring as a result of parturition can potentially be repaired efficiently using an oversewn stapled primary closure technique.