Pedunculated lipoma is one of the common causes of strangulation or obstruction of the small intestine (4,6). The lipoma is a benign tumor originating from the mesentery of the small intestine, causing strangulation of the small intestine and mesentery (3,4,6,10). Previous studies have reported abdominal lipomas measuring 4 to 14 cm (2,3,9). Pedunculated lipomas account for 0.25-7% of hospitalized colic (1,12), 7-13% of colic surgery (4,8,11,12), and 3-27% of small bowel disease in horses (3,5,6,14). Small intestinal obstruction by lipomas is more common in geldings than in mares or stallions and is seen more frequently in older horses (4-6). American Saddlebreds, Arabians, Quarter Horses, and pony breeds are at high risk of lipomas (4).

The clinical signs of pedunculated lipoma vary according to the segment, extent, and degree of strangulation of the intestine (6). Horses with lipoma usually present with mild to moderate abdominal pain and gastric reflux (3). Because the symptoms are non-specific, the diagnosis of pedunculated lipoma is complicated. Although the enlarged small intestine can be palpated through rectal examination, lipomas are usually detected by exploratory laparotomy or post-mortem examination (6). A definitive diagnosis is made through histopathological examination after surgical resection. Horses with lipomas are usually treated surgically (3). The prognosis varies, with reported short-term survival of 48-78.6% (3,4) and long-term survival of 50-72.7% (3,4,11).

This report describes the diagnosis and surgical treatment of the small intestinal strangulation caused by abdominal lipoma in a Thoroughbred horse in Korea.

A seven-month pregnant 15-year-old Thoroughbred mare weighing 610 kg presented with acute colic to Jeju National University Equine Hospital. The patient was found lying in the paddock at dawn. The pain persisted even after administering flunixin meglumine 1.1 mg/kg IV (Fotis; Dongbang. Co., Ltd.), detomidine hydrochloride 0.02 mg/kg IV (Detomidine; Provet Veterinary Products), and butorphanol tartrate 0.02 mg/kg IV (Butophan; MyoungmoonPharm. Co., Ltd.) at the farm. At presentation, the mare was depressed, with a low rectal temperature of 36.4°C, a normal heart rate of 40 bpm, and a normal respiratory rate of 16 bpm. The hydration status was fair with pink mucous membrane and the capillary refilling time <1 s. Bilateral gastrointestinal borborygmi was not heard on auscultation. Hematocrit, total protein, and lactate were 33.9%, 5.9 g/dL, and 2.0 mmol/L, respectively. Creatinine kinase was 586 U/L (reference range; 120-470 U/L), indicating possible intestinal injuries. Nasogastric intubation revealed foul-smelling reflux of 10 L. Rectal examination and abdominal ultrasonography confirmed small intestinal distention and loops of thickened small intestine.

An exploratory laparotomy was performed. Penicillin G 12,500 IU/kg IM (PPS; Daesung Microbiological Lab. Co., Ltd.), gentamicin sulfate 4.4 mg/kg IV (Samu gentamicin injection; Samu Median Co., Ltd.) and flunixin meglumine 1.1 mg/kg IV were administered to the patient as preoperative treatments. For anesthesia initiation, detomidine hydrochloride 0.02 mg/kg IV (Detomidine; Provet Veterinary Products) and butorphanol tartrate 0.02 mg/kg IV (Butophan; MyoungmoonPharm. Co., Ltd.) were injected. Anesthesia was induced with ketamine hydrochloride 2.2 mg/kg IV (Ketamine. Inj; Yuhan) and diazepam 0.03 mg/kg IV (Diazepam. Inj; Samjin Pharm. Co., Ltd.). General anesthesia was maintained with isoflurane (Ifran^®, Hana Pharm. Co., Ltd.) and 100% oxygen. The patient was placed in dorsal recumbency.

A midline incision was made after surgical disinfection. The exploratory laparotomy revealed congestion of the terminal ileum and mesentery and a yellowish large, smooth-surfaced mass (Fig. 1). The mass originated from the mesentery. After the reduction of the small intestine, the mass was resected after double ligating the stalk with an absorbable suture using Vicryl No. 2-0 (Ethicon; New Jersey, USA). A small bowel resection was not performed as intestinal motility was detected after the removal of the mass. After a peritoneal lavage, a simple continuous suture was performed on the abdominal wall and subcutaneous tissue with absorbable sutures, using Vicryl No. 2 (Ethicon; New Jersey, USA) for the abdominal wall and Vicryl No. 2-0 for the subcutaneous tissue. Skin staples were used. Gauze and Ioban^TM (3M; St. Paul, USA) were applied. After surgery, the patient recovered well from anesthesia with assistance.

Figure 1. Intraoperative findings of the abdomen. (A) A laparotomy revealed the congestive mesentery and ileum. The color of the strangulated ileum had changed to purple (left), distinguishable from the color of the unaffected small intestine (right). (B) A smooth and yellowish mass was seen which originated from the mesentery.

The patient was treated with penicillin G (12,500 IU/kg IM once daily for 1 week, PPS; Daesung Microbiological Lab. Co., Ltd.), gentamicin sulfate (6.6 mg/kg IV once daily for 1 week, Samu gentamicin injection; SamuMedian Co., Ltd.), flunixin meglumine (1.1 mg/kg IV once daily for 1 week, Fotis; Dongbang. Co., Ltd.) and famotidine (1.8 mg/kg PO once daily for 1 week, Famotidine tab; Korea Nelson Pharm Co., Ltd.) as postoperative treatment. The patient was administered 20 L of isotonic fluid for 5 days. The patient was fed water 24 hours after surgery and 500 g of hay 36 hours after surgery. The patient was discharged on postoperative day 8 without complications.

The excised mass was yellowish and 24 cm × 16 cm × 16 cm in size (Fig. 2A). Histopathology confirmed the mass as a lipoma, mainly composed of benign fat cells and fibrosis along with fat necrosis (Fig. 2B).

Figure 2. Photograhic image of the resected mass (A) The mass was round peanut- shaped with a smooth surface, measuring 24 cm × 16 cm × 16 cm. (B) Microscopy showed the mature neoplastic lipocytes (Hematoxylin and eosin (H&E) stain; Bar = 100 μm), indicating a histopathologic finding of lipoma.

In the current case, a pregnant 15-year-old Thoroughbred mare presented with acute abdominal pain. Nasogastric tubing found 10 L of gastric reflux, and ultrasonography revealed dilated loops and thickened walls of the small intestine. Exploratory laparotomy identified the mass, which was removed blindly. The patient recovered without complications. Histopathological examination confirmed that the mass was a lipoma. This is the first report describing a horse with small intestinal strangulation due to a large pedunculated lipoma in South Korea.

The frequency of occurrence of lipomas may vary according to sex, stature, breed, and age. The mean age of horses with pedunculated lipoma has been reported to be 16.6-18.7 years old (6). Among horses, being a gelding and having a short stature are predisposing factors for abdominal lipoma (4-6). However, in this case, the mare with acute colic had a lipoma that was different from those previously reported. Therefore, lipoma should be considered as a differential diagnosis in horses presenting with acute colic even in the absence of predisposing factors.

Abdominal ultrasonography is a non-invasive diagnostic tool for horses with abdominal pain. Manso-Díaz et al. (9) reported ultrasonographic findings in two horses with abdominal lipoma. In their report, an ultrasound found small intestinal loops in the caudo-ventral site and also detected an echogenic round mass alongside the small intestinal loops (9). However, due to the deep abdominal cavities and intestinal gas, in most cases, the pedunculated lipoma was diagnosed by an exploratory laparotomy or postmortem examination (6). In this case, ultrasound revealed small intestinal loops with thickened walls but not the mass. Considering its position, a combination of transcutaneous and rectal ultrasonography may facilitate the detection of the abdominal mass.

The length of the pedicle reportedly acts as a risk factor rather than the size of the lipoma (7,13). The elongated pedicle allows the mass to move more freely in the abdominal cavity, causing an extraluminal and strangulating obstruction by surrounding the intestine and mesentery (7). On the other hand, if the pedicle is short, the lipoma rarely causes strangulation or obstruction of the small intestine. However, it is difficult to exteriorize and remove the mass. Hence, this usually allows only blind resection which could cause damage to the surrounding structures including the mesentery or other intestinal structures. Generally, as the lipoma enlarges, it draws out the pedicle (7). In this case, the large-sized lipoma with a short pedicle made it impossible to exteriorize the mass, and only blind resection could be carried out. Blind resection of the mass usually requires the great degree of caution. Evaluation of the length of the pedicle is also desirable before mass removal.

Abdominal lipomas in horses are usually surgically removed. However, resection of the lipoma alone was reportedly performed in only 18% of cases (6). A simultaneous intestinal anastomosis was performed in the remaining 82% (6). However, in this case, a small intestinal resection was not performed because motility was detected and the color of the small intestine was fair. A quick decision to operate helped avoid the resection of the small intestine aided the successful recovery.

In the current case, a seven-month pregnant mare presented with acute abdominal pain. An ultrasonographic examination detected small intestinal dilation with a thickened wall. An exploratory laparotomy revealed strangulation of the ileum and the mesentery by a large pedunculated lipoma, which was resected blindly. This report could be helpful in the diagnosis and treatment of intestinal strangulation due to mesenteric pedunculated lipoma in horses.

The authors have no conflicting interests.