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The Canadian Veterinary Journal logoLink to The Canadian Veterinary Journal
. 2019 Sep;60(9):991–994.

Surgical treatment of persistent colic in a horse caused by an anomalous vascularized fibrous band

Rachael K Needles 1, Marie-Soleil Dubois 1,
PMCID: PMC6697011  PMID: 31523088

Abstract

This case report documents an unusual case of persistent colic in a horse caused by an anomalous vascularized band of tissue running between the visceral surface of the liver and the mesentery of the large colon at the level of the sternal/diaphragmatic flexures. The horse was presented with a history of exhibiting signs of mild persistent colic that were suspected to be caused by displacement of the large colon. Volvulus of the large colon was identified during exploratory celiotomy. The band of tissue was transected, and the displacement corrected. The horse made an uneventful recovery.


“Colic” is an all-encompassing term used in horses to describe signs of abdominal pain. The origin of this pain is most commonly the digestive system, but it may also result from conditions affecting other organ systems (1). There was an estimated 4.2 colic events/100 horses per year in the United States from 1998 to 1999, with an estimated overall cost of $115 300 000 annually (2). A more recent study has not been found, but it is likely that the overall costs have changed significantly since then. While most cases of colic can be resolved with medical management, approximately 10% of all instances of colic will not resolve without surgical exploration of the abdominal cavity (3). Exploratory celiotomy is most commonly performed at a referral facility, with the horse restrained in dorsal recumbency under general anesthesia (3). The surgical procedure may range from a simple abdominal exploration and lavage, to a more complex procedure such as intestinal resection and anastomosis (36).

While relatively uncommon (1.1% to 4.6% of all cases of colic), abdominal bands have been reported in a few cases of equine colic (711). Usually involving the small intestine, these bands can be inflammatory in nature (adhesions) or structural congenital anomalies arising from various structures (12). This report describes an unusual case of surgical colic caused by a vascularized fibrous band of tissue connecting the large colon to the liver.

Case description

A 12-year-old Quarter Horse cross gelding was presented to the Milton Equine Hospital in August 2017 with a 24-hour history of exhibiting signs of colic. The horse was found recumbent in the pasture the previous evening with signs of mild to moderate colic (lack of appetite, pawing, frequent recumbency). Physical examination of the horse by the referring veterinarian revealed mild tachycardia and absence of gut sounds on auscultation of the abdomen. A firm distended large colon palpated per rectum enabled that individual to tentatively reach a diagnosis of a pelvic flexure impaction. The horse was given a non-steroidal anti-inflammatory medication intravenously (flunixin meglumine, Prevail; MWI, Boise, Indiana, USA). The colic signs were temporarily relieved, but returned overnight and the horse began exhibiting more severe signs of colic (rolling, restlessness). Repeat examination early the following morning by the same attending veterinarian revealed increased tachycardia and a trans-rectal palpation examination consistent with a pelvic flexure impaction and colonic displacement, at which point the horse was referred for further diagnosis and treatment. To the best of the owner’s knowledge, this was the first episode of colic that this horse had experienced. No previous abdominal surgeries or significant infections, including strangles, were reported.

At the time of our examination, the horse was bright, alert, and responsive. His cardiac auscultation revealed tachycardia (52 beats per min) and a grade IV/VI systolic heart murmur. His respiratory rate was 24 breaths per min and temperature was 38.0°C. The horse had decreased borborygmi on auscultation of the 4 quadrants of the abdomen. He was exhibiting full body tremors. A complete blood (cell) count (CBC) showed mild leukopenia [white blood cells (WBC) 4.1 × 103/μL (reference interval (RI): 5.5 to 12.5 × 103/μL].

The horse was sedated with xylazine (XylaMed; Bimeda, Cambridge, Ontario), 0.25 mg/kg body weight (BW), IV. He was also administered an antispasmodic (Hyoscine butylbromide, Buscopan; Boehringer Ingelheim, Burlington, Ontario), 0.2 mg/kg BW, IV, to facilitate trans-rectal examination. Palpation of abdominal viscera per rectum revealed moderate gas distension within the cecum and large colon, as well as multiple tight taenial bands consistent with colonic displacement. The large colon also contained a moderate quantity of firm fecal material, consistent with an impaction. Exact localization of the impaction and characterization of the displacement were difficult. Furthermore, the pelvic flexure was not identified. On abdominal ultrasonography, the colonic mesenteric vessels were distended and visible on the right ventral abdomen. A nasogastric tube was placed, and 4 L of net reflux were obtained, consisting of fibrous feed material. The tube was left in place and the stomach was lavaged every 2 h until cleared of food content. Given the clinical findings, our conclusion was that there was a colonic displacement that could be treated medically with isotonic crystalloid fluid therapy, hand walks, and close monitoring.

The horse remained comfortable without exhibiting signs of abdominal pain throughout the rest of the day and overnight, passing normal manure. Repeat trans-rectal palpation the morning after admission (day 1) showed a decrease in gas distension of both the cecum and large colon, but the colonic displacement was still present. The size and density of the impaction were unchanged upon palpation. The nasogastric tube was removed that morning after administration of 6 L of water, 185 g of electrolytes (Electrolytes, Calf-Lyte II HE; Vétoquinol, Lavaltrie, Quebec), and 1 L of mineral oil. The rate of intravenous fluid therapy was gradually reduced that day and the gelding remained comfortable, passing soft formed manure.

On day 2 after admission, rectal palpation indicated that the impaction was reduced in size but still present. The colonic displacement had not resolved. The horse was started on a refeeding program of very small mashes that day in order to stimulate intestinal motility. He had a large appetite and good manure production. Repeat CBC showed worsening of the leukopenia (WBC: 2.1 × 103/μL).

On day 3 after admission, the impaction was only slightly smaller and the displacement was unchanged. That afternoon the horse showed mild colic signs (grunting, flank watching, lying down), which responded well to treatment with xylazine (Bimeda), 0.3 mg/kg BW, IV, and hyoscine butylbromide (Boehringer Ingelheim), 0.2 mg/kg BW, IV. His vitals remained within the normal range overnight. The following morning (hospital day 4), the findings per rectal palpation were unchanged. Due to failure to resolve both the displacement and the impaction with medical therapy, the decision was made to perform an exploratory laparotomy.

The gelding was administered procaine benzylpenicillin (Depocillin; Intervet Canada, Kirkland, Quebec), 22 000 mg/kg BW, IM, gentamicin (Gentocin; Intervet Canada), 6.6 mg/kg BW, IV, flunixin (MWI), 1.1 mg/kg BW IV, and tetanus antitoxoid (Tetanus antitoxoid; Zoetis, Kalamazoo, Michigan, USA), 1 mL, IM, before surgery. The horse was sedated with xylazine (Bimeda), 1 mg/kg BW, IV, and anesthesia was induced with ketamine (ketamine hydrochloride, Narketan; Vétoquinol), 3 mg/kg BW, IV, and diazepam (diazepam; Sandoz Canada, Boucherville, Quebec), 16.6 mg/kg BW, IV. The horse was placed in dorsal recumbency and anesthesia was maintained with isoflurane inhalant anesthetic agent vaporized in oxygen. A lidocaine (lidocaine hydrochloride, Lidocaine Neat 2%; Zoetis Canada), 1.3 mg/kg BW bolus over 15 min, followed by a continuous rate infusion at 3 mg/kg BW per hour was given. The ventral abdomen was prepared and draped for aseptic surgery according to hospital protocol.

An incision was made through the ventral midline from the umbilicus extending 20 cm cranially and the abdomen was opened. Abdominal exploration revealed significant displacement and mild gas distension of the large colon. A tight band of tissue was palpated within the cranial abdomen and it appeared that a portion of the colon was attached to it. After decompression of the large colon using suction with 18-G needles, the colon could be partially exteriorized. It was then possible to further characterize the colonic displacement, which involved a volvulus at the level of the right colon. There was an abnormal band of tissue present that originated from the visceral surface of the quadrate lobe of the liver and attached to the mesentery of the large colon at the level of the diaphragmatic/sternal flexures (Figure 1). The band was approximately 40 to 50 cm long and about 3 cm in diameter along its length, becoming wider at the attachment sites. It contained several large blood vessels that were approximately 6 to 8 mm in diameter. The attachment site to the liver was diffuse over an area of approximately 10 × 4 cm. Attempts to reduce the colon volvulus with the band intact were unsuccessful and therefore it was decided to transect it. Transection was selected over resection as it was difficult to access and visualize most of the band. The vascular band was exteriorized as much as possible and 2 transfixing sutures (USP size 2 polyglactin 910) were placed on each side of the planned transection site. The band was then transected using an emasculator, which was left in place for 2 min, then released (Figure 2). The volvulus, which was at the level of the right colon and was approximately 270°, was manually corrected and the colon was observed for approximatively 15 min; it did not show any color changes and proper pulses were palpated within the mesenteric vessels. A mild impaction was present in the left ventral colon but was not judged significant enough to warrant evacuation. The colon was then replaced in the abdomen in its correct anatomical location. All other organs and internal structures were checked; no other abnormalities were found.

Figure 1.

Figure 1

Intra-operative image of the anomalous vascular band (arrowhead) running from the quadrate lobe of the liver (not shown in the photograph) to the mesentery of the diaphragmatic/sternal flexure of the large colon. The vessels within the band branched off at the attachment site to the large colon. (* pelvic flexure).

Figure 2.

Figure 2

The transection site of the band on the mesentery of the diaphragmatic/sternal flexure of the large colon after resolution of the volvulus (arrowheads).

The horse recovered well from anesthesia and was maintained on a course of antibiotics [gentamicin (Intervet Canada), 6.6 mg/kg BW, IV, q24h, and procaine penicillin (Intervet Canada), 22 000 mg/kg BW, IM, q12h for 2 d, then trim-ethoprim sulfamethoxazole (TMS; Trutina Pharmacy, Ancaster, Ontario) 25 mg/kg BW, PO, q12h for 5 d], and a tapering dose of intravenous flunixin meglumine (flunixin meglumine, Prevail; MWI) for 3 d. The horse made an uneventful recovery from the surgery, with no post-operative complications. He had 1 episode of colic 2 mo after discharge, which resolved with medical intervention.

Discussion

Abdominal bands involved in cases of equine colic can be inflammatory in nature (adhesions) or structural congenital anomalies arising from various structures. The most common congenital band is a mesodiverticular band, which is usually seen as a fold of tissue running from the mesentery to the antimesenteric side of the ileum or jejunum (8). Arising from remnants of fetal circulation, these mesodiverticular bands provide a flap of tissue through which the small intestine can become entrapped (8). These bands originate from the vitelline arteries of the embryonic yolk sac and are normally formed as a congenital abnormality when the arteries fail to regress as the embryo matures (8). In contrast to horses, mesodiverticular bands are commonly reported in young children as a cause of intestinal obstruction (9).

The band described in this case consisted of a thick structure containing fibrous and connective tissue, with at least 2 major vessels running through it. The location of this band within the abdomen (running from the quadrate lobe of the liver to the mesentery of the diaphragmatic/sternal flexure of the large colon) does not fit with any descriptions of mesodiverticular bands or vestigial congenital structures that the authors found in the literature. The anomalous congenital bands that have been described in the literature all originate or terminate at portions of the small intestine: mostly the jejunum (8,10,11). In the human literature, there are a few scattered case reports of large colon obstruction by congenital anomalous bands, and 2 reports of a band extending from the liver to either the large or small intestine (9). The human patient with a band extending from the liver to the ascending colon was only 9 d old at the time of surgery, and unfortunately died following surgical complications (9). At this time, there are no reasonable embryonic explanations for the origins of these liver-associated bands in either human or veterinary medicine (9).

Although the possibility of the band being congenital in nature was explored, it cannot be excluded that some form of intra-abdominal inflammatory process occurred resulting in adhesion formation. However, given the history reporting lack of previous colic episodes, abdominal surgeries or significant infections, there does not appear to be any known clinical reasons for adhesions to be present in this horse. Furthermore, the diameter of the band, the well-established vasculature, and the absence of any other adhesions within the abdomen render this hypothesis unlikely. The exact nature of the band remains unknown.

The decision to transect this unknown vascular structure was not without risks, as it contained significant sized blood vessels that appeared to provide some vascular supply to the colon. However, after multiple failed attempts to resolve the colon volvulus with the band intact, it appeared that the only viable course of action to correct the displacement was to proceed with transection of the band, knowing that it involved risks of hemorrhage, colonic ischemia, and possible death. Despite our misgivings, from the current clinical appearance of the patient there appears to have been no long-term effects of ligating the vascular structure. It could have been beneficial to clamp the band for a few minutes before ligation in order to assess the significance of its vascular supply provided to the colon.

This case shows that vascularized fibrous bands can be present between the liver and the large colon in the horse, and these can result in a low grade, non-resolving displacement colic. It is a good example of the use of an elective exploratory laparotomy as a diagnostic and treatment option for certain cases of non-resolving colic signs in the equine patient. It seems plausible that there may be more patients with these bands that go undiscovered due to lack of clinical signs or when surgery is not a financial option. In the event of a vascularized band such as the one described here, care should be taken to evaluate the extent of the vascular involvement both before and after ligation and transection of the anomalous band. CVJ

Footnotes

Use of this article is limited to a single copy for personal study. Anyone interested in obtaining reprints should contact the CVMA office (hbroughton@cvma-acmv.org) for additional copies or permission to use this material elsewhere.

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