Strangulating large colon volvulus (LCV) is an important cause of fatal colic that progresses rapidly (11,12). The reported survival to discharge following surgical correction of a strangulating LCV is between 34.7% and 88% (1,3,5,8,9,17). The prognosis is affected by the degree of colon involvement, early recognition, and prompt surgical treatment (1,8). Several surgical techniques for colectomy and anastomosis, such as a resection with side-to-side or end-to-end anastomosis have been described (11,12,17). Multiple objective parameters to determine the colonic viability and prognosis, including the peripheral lactate values and histopathology evaluation of pelvic flexure biopsies, have been studied (2,7,12,14,15). Nevertheless, the clinical decisions for a colectomy are most often made based on a subjective intraoperative assessment of the colonic viability, such as the appearance of the bowel wall, particularly the mucosa, because of the lack of availability and predictability of the objective measurements for intraoperative diagnosis to predict the outcomes of LCV surgery (6,7,14,17).

Post-parturient mares are predisposed to LCV owing to the shape of the abdomen during and after carrying a foal, having a larger and deeper concave space for the large colon and cecum (18). On the other hand, clinical investigations and specific case reports on strangulating LCV are limited. Moreover, awareness of the potential risk, surgical treatment, and postoperative care of LCV is relatively lower than the awareness of other causes of colic among equine practitioners in Korea. This paper presents a clinical case of strangulating LCV in a post-parturient mare, describing the sequential therapies, surgical intervention using a large colon resection and anastomosis (LCRA), and postoperative care. In addition, this paper reports the limitations of the case, expanding current knowledge of LCV and related considerations in horses.

An 11-year-old thoroughbred mare that gave birth two months previously, with a body weight of 560 kg, was presented to the Jeju Stud Farm Equine Clinic of the Korea Racing Authority with a history of lying down and rolling. According to the referring veterinarian, the owner recognized the symptoms the day before presentation. The horse remained unimproved after the symptomatic treatment, including nonsteroidal anti-inflammatory drugs (NSAIDs) and fluid therapy. Consequently, she was referred for additional evaluation and treatment. Despite the administration of NSAID (flunixin meglumine, 1.1 mg/kg, IV) and analgesics (detomidine 10 μg/kg IV and butorphanol tartrate 10 μg/kg IV), the mare showed clinical signs of colic, including severe pain response, characterized by tachycardia (72/min), tachypnea (60/min), sweating, rolling, and lying down. The mucous membrane of the patient was pale pink with a delayed capillary refill time (CRT) beyond 2.5 seconds. The serum chemistry revealed hyperlactatemia (2.9 mmol/L, reference range, 1-1.5 mM/L), hypocalcemia (10.1 mg/dL, reference range, 11.5-14.2 mg/dL), and hypoproteinemia (5.2 g/dL, reference range, 5.7-8.0 g/dL) (Table 1), while the results of complete blood count (CBC) and electrolytes were within the normal ranges. On auscultation, pinging sounds with decreased borborygmi over both sides of the flank were identified. On rectal palpation, a loop of the large colon distended with gas, fluid, and fecal pellets was palpated. Abdominal ultrasonography (US) revealed distended edematous colons with little peristaltic activity characterized by a diffusely hypoechoic colonic wall and irregular strong high echoes off the mucosal gas interface (Fig. 1A, B).

Table 1 . Serum chemistry changes before and after strangulating LCV surgery in the horse.

Parameter	Reference range	Pre- operation	PO1	PO2	PO3	PO4	PO5	PO6	PO7	PO9
Lactate (mmol/L)	< 1.5	2.9	1.7	1.7	NA	NA	0.9	NA	0.8	NA
SAA (mg/L)	< 20	NA	416.1	1,323.6	2,127	1,743.5	679.8	888.6	530.4	< 10
CK (U/L)	120-470	470	3,739	2,471	1,758	1,165	694	563	409	340
AST (U/L)	175-340	280	712	908	1,057	979	838	821	708	521
TBIL (mg/dL)	0.5-2.3	1.8	4.3	6.3	6.6	4.1	3.3	3.7	2.8	2.0
Calcium (mg/dL)	11.5-14.2	10.1	7.4	10.1	10.8	11.6	11.6	12.0	12.0	11.9
Total protein (g/dL)	5.7-8.0	5.2	4.7	4.7	5.6	5.4	5.0	5.6	5.6	5.5
Globulin (g/dL)	2.7-5.0	2.2	1.8	1.9	2.5	2.2	2.2	2.5	2.5	2.6

NA, not available..

Figure 1. Ultrasonography image of strangulating LCV on the left paralumbar fossa (A) and left ventral abdomen (B), revealing distended edematous colons with haustrations and little peristaltic activity. Note the increased wall thickness of the large colon characterized by the diffusely hypoechoic colonic wall (arrowheads) and irregular strong high echoes (arrows) off the mucosal gas interface.

Based on the history, laboratory evaluation, and physical and rectal examinations, large colon displacement or volvulus was considered in the differential diagnosis. Immediate surgical intervention was carried out after obtaining informed consent to correct the cause of colic. In addition to the NSAID (flunixin meglumine, 1.1 mg/kg, IV), which was administered during the physical examination, prophylactic antibiotics (procaine penicillin, 22,000 U/kg, IM; gentamicin, 6.6 mg/kg, IV) were administered as a preoperative medication. General anesthesia was induced with diazepam (0.1 mg/kg, IV) and ketamine (2.2 mg/kg, IV) after sedation (detomidine, 0.02 mg/kg, IV), and maintained with isoflurane and 100% oxygen in a closed-circuit vaporizer system in the dorsal recumbency. The surgical site was prepared aseptically and draped properly. An abdominal midline incision starting at the umbilicus and extending approximately 30 cm in the cranial direction was made using a No. 20 scalpel blade. After opening the peritoneum, the first part of the identified gastrointestinal tract was the distended large colon, which was tightly distended with gas and ingesta (Fig. 2A). The large colon was exteriorized from the abdomen and assessed (Fig. 2B, D). The strangulating LCV was defined as a volvulus of >540° in the counterclockwise direction. After correcting the volvulus, the intestinal viability was determined using subjective criteria, including serosal surface color, motility, degree of edema in the bowel wall and mesocolon, and palpation of a pulse. Approximately 80% of the entire large colon, about 60cm distal from the cecocolic fold, was affected by the strangulation (Fig. 2B, D). The color of the colonic lesion was dark blue without a pulse and motility, and the intestinal edema and congestion were severe (Fig. 2C, D). After waiting for approximately 10 minutes, the colonic viability was reassessed. Unfortunately, the affected part of the bowel did not change in any of the criteria. Consequently, the surgical decision was made to remove the nonviable strangulated lesion and perform an end-to-end anastomosis procedure.

Figure 2. Identification of large colon volvulus (A, B), assessment of bowl viability (C, D), and surgical procedure for large colon resection and anastomosis (E-H) in this study. (A) Large colon that was obstructed with gas and ingesta caused by volvulus. (B) Exteriorized large colon after correction of the volvulus. Dark blue colonic lesion without pulse and motility. (C) Severe edema and congestion in the colonic wall and mesocolon on the strangulated lesion. (D) Difference in the color and congestion between viable and nonviable strangulated lesions (arrows). (E) Transected colon for the anastomosis. The colon was emptied through a pelvic flexure enterotomy before the resection. (F) Apposition and closure of the anastomosis using a simple continuous pattern for the first layer. (G) Closure of the anastomosis using the Cushing pattern for the second layer. The band on the large colon was continuously apposed. (H) The large colon after anastomosis was completed.

For an end-to-end resection, the exteriorized colon was draped off and emptied through a pelvic flexure enterotomy. All ingesta and fluid were removed carefully from the dorsal and ventral colons to minimize contamination during the resection. After choosing the site for resection based on the difference in color and congestion between the viable and nonviable lesions (Fig. 2D), the colonic vessels were isolated by a blunt dissection and double-ligated using 0 Vicryl ties. The resection site was draped carefully with sterile large laparotomy sponges. The dorsal colon (on an angle to its long axis) and ventral colon (perpendicular to its long axis) was transected (Fig. 2E). The colons were apposed to each other, lining up the bands. Closure of the anastomosis was performed with two suture layers using 0-polyglactin 910 (Coated Vicryl, ETHICON) in a full-thickness simple continuous appositional pattern and oversewn with a Cushing pattern (Fig. 2F-H). Suture adjustment in the ventral colon was wider than in the dorsal colon to make even circumferential alignment. Anastomotic leakage was checked during lavage, and the colon was replaced in the abdomen (Fig. 2H). The rest of the intestinal tract was also assessed. The distended small intestine was then decompressed by manually milking the ingesta and gas into the cecum. After correct repositioning of the bowels, peritoneal irrigation with 15 liters of warm sterile saline was conducted. The abdominal wall, subcutaneous tissues, and skin were routinely closed. The horse recovered uneventfully from anesthesia.

Postoperatively, the patient received NSAID (flunixin meglumine, 1.1 mg/kg, IV, once daily), broad-spectrum antimicrobials (procaine penicillin, 22,000 U/kg, IM, once daily; gentamicin, 6.6 mg/kg, IV, once daily), antiacids (famotidine, 0.3 mg/kg IV twice daily; omeprazole, 4 mg/kg PO once daily), and anti-diarrheal agents (smectite and probiotics) with the appropriate fluids (lactated Ringer’s solution with 5% dextrose) for five days. Continuous lidocaine infusion (1.3 mg/kg IV as a bolus followed by a 0.05 mg/kg/min infusion) was administered for the first 12 hours after surgery. The follow-up physical examinations on postoperative day 1 (PO1) showed a decreased gut sound and motility on the right flank, mild pain with bruxism, while the vital signs (heart rate, 40-54/min; respiratory rate 24/min; body temperature, 38°C) and blood lactate level (1.7 mmol/L, reference range, 1-1.5 mM/L) were ameliorated compared to the values before surgery. Blood analysis on PO1 revealed elevated levels of serum amyloid A (SAA; 416.1 mg/L; reference range < 20 mg/L), creatinine kinase (CK, 3,739 U/L; reference range 120-470 U/L), aspartate aminotransferase (AST, 712 U/L; reference range 175-340 U/L), and total bilirubin (4.3 mg/dL; reference range 0.5-2.3 mg/dL) as well as decreased levels of calcium (7.4 mg/dL; reference range 11.5-14.2 mg/dL), total protein (4.7 g/dL; reference range 5.7-8.0 g/dL), and globulin (1.8 g/dL; reference range 2.7-5.0 g/dL). The factors essential for a prognosis evaluation and out of the normal range are specified in Table 1. Defecation started from the PO1 without diarrhea, and urination was normal. The horse was not fed for the first 24 hours after surgery, then gradually introduced to hay with intermittent grazing on PO2. After PO2, the gut motility and mild pain were restored to their normal condition. With supportive care, the abnormal blood analysis values gradually improved (Table 1). The horse regained its appetite and vitality during hospitalization and was discharged on PO9. The horse remained healthy without clinical disorders related to gastrointestinal disease throughout the three-month follow-up.

This report describes a clinical case of a strangulating LCV in an 11-year-old post-parturient thoroughbred mare. Although more than 80% of the large colon was resected, the patient tolerated the procedure without serious complications. Previous clinical and experimental reports have shown that horses can endure a resection of up to 90% of the large colon well (13). Nevertheless, post-operative complications, such as persistent endotoxemia and peritonitis, are frequently encountered due to contamination during the surgery (11,12). An improper anastomotic technique leads to leakage and continued bowel devitalization, highlighting the importance of the surgeon’s technique and decision to discern the extent of a devitalized bowel and perform a meticulous anastomosis (12). In these points, the good prognosis of this case is attributed to not only the early recognition and prompt surgical treatment but also the appropriate clinical decision during the surgery. An attempt was made to reduce the time from admission to the surgical procedures. The devitalized colonic lesion was removed completely while minimizing the tension of the anastomosis site and the risk of dehiscence. Furthermore, postoperative pain and complications after LCRA, including diarrhea, hypoproteinemia, and endotoxemia, were also effectively controlled with medication, including NSAIDs and lidocaine constant rate infusion (CRI).

Two surgical techniques for colectomy are principally described: resection and end-to-end anastomosis and resection and side-to-side anastomosis (12,13). The choice depends on the surgeon’s preference and the location of the anastomosis site (12,13). Side-to-side anastomosis is preferred when the resection site is at and beyond the level of the cecocolic ligament. The end-to-end technique places much more tension on the anastomosis site and increases the risk for dehiscence than the side-to-side technique (12,13). Automated stapling equipment was also developed and evaluated for the application of LCRA (12,13,19). Stapling is used primarily for side-to-side anastomoses in the large colon. Although the differences between stapled and sutured anastomosis were not statistically or clinically significant regarding the stoma sizes and complications, a stapled anastomosis is faster than the sutured one resulting in less contamination of the surgical fields (19). However, the stapling instrument is frequently restricted because the colonic wall is usually edematous and friable, and the lesion for the resection is too extensive, making the equipment ineffective (10,12,19). In the present case, an end-to-end anastomosis was performed using a conventional sutured technique because the anastomosis site is distal from the cecocolic ligament, and the intestinal edema and congestion did not allow proper closure using automated stapling equipment (Fig. 2C).

The decisions to determine the gut viability for resection and the length of lesion that needs to be removed usually depend on the subjective intraoperative assessments (6,7,14). In the present case, intestinal viability was also assessed by subjective criteria, such as gut motility and color, degree of edema in the colonic wall, and palpation of a pulse. Several methods, including peripheral lactate value, intravenous fluorescein, doppler ultrasonography, histopathology analysis, surface and pulse oximetry, and intraluminal pressure measurements, have been introduced to improve the objectivity of viability assessment, but these methods are still considered ancillary and cannot replace clinical judgment (2,7,12-16). At this point, it is necessary to develop objective parameters for intraoperative assessment of the gut viability, which can be used conveniently during surgery. In the present case, the preoperative serum calcium and total protein values were significantly lower than the reference ranges, while the postoperative values were restored within the normal limits (Table 1). These tendencies were also observed in previous retrospective studies with horses after LCRA, which is assumed to be explained by protein and protein-bound calcium leakage associated with a compromised bowel (1,4), leaving a possibility to use the serum calcium and total protein levels as assessment parameters for LCRA. Nevertheless, further studies will be needed to demonstrate the mechanism of low calcium and protein levels in horses with a devitalized bowel and to apply it to clinical decisions. In addition, the clinical grading system for adding a degree of objectivity to the subjective assessment of devitalized intestine is warranted.

According to the retrospective data in the Jeju stud farm equine clinic of the Korea racing authority, 20 surgeries (9%) were performed due to the LCV among 221 surgical colic cases during the last seven years (Jan 2016 to Nov 2022). During and after the LCV surgery, 11 horses (55%) died or euthanized, while nine (45%) survived. The LCRA technique did not use any LCV surgeries except for the case described in this study. Despite the high occurrence rate and mortality of LCV in horses, there have been limited in-depth clinical investigations in Korea. The present report shows the specific clinical case of LCRA in a post-parturient broodmare in Korea. The authors hope that this report emphasizes and familiarizes the horse owners’ and referring veterinarians’ knowledge of the importance of proper preoperative, intraoperative and postoperative management and treatment of LCV and LCRA in horses, particularly the post-parturient broodmares so future cases in Korea and elsewhere can have successful outcomes as in the case presented here.

The present report describes the clinical diagnosis, surgical intervention, postoperative care process, and the limitations of a strangulating LCV case in a post-parturient thoroughbred broodmare. The findings will enhance the current knowledge of the clinical LCV and the related considerations on horses. The data will benefit equine practitioners and owners by contributing to a better understanding of LCV in horses in Korea and suggest the LCRA as a surgical option for the treatment of strangulating LCV.

The authors have no conflicting interests.

Conceptualization: J Yoon, PC Rakestraw, and A Kim; Data curation: J Yoon, Y Kim, and J Park; Formal analysis: J Yoon, IS Choi and PC Rakestraw; Resources: Y Kim, J Park, and PC Rakestraw; Supervision: A Kim; Validation: IS Choi and A Kim; Visualization: J Yoon; Writing-original draft: J Yoon; Writing-review & editing: J Yoon, IS Choi, PC Rakestraw, and A Kim.