Rectal prolapse in animals is often caused secondary to the conditions resulting in tenesmus, such as diarrhea, intestinal parasitism, colitis, and proctitis or increased abdominal pressure as dystocia, constipation, urinary tract obstruction, colic, retained fetal membranes, rectal tumor or foreign body (1,6,10). Rectal prolapse can be classified into the following four categories according to the anatomic organs affected and the severity of the prolapse in horses: Type I rectal prolapse involves only rectal mucosa and submucosa protruding through the anus. Type II shows a full thickness prolapse of the whole rectal ampulla or a part of it. Type III rectal prolapse involves small colon intussusception into the rectum without protruding through the anal sphincter. Type IV is when the peritoneal part of the rectum and part of the small colon intussuscepted out of the anus (3). The elk (Cervus canadensis) is one of the largest species within the deer family, Cervidae, and one of the largest terrestrial mammals in its native range of North America, Central and East Asia (5). In Korea, they are raised mainly for the commercial use of their horn in oriental medicine throughout the country even though the population is not large. Rectal prolapse can occur in all domestic animals (1,6,11), but there are few clinical reports regarding the condition in elk. This report presents a rare case of a type II rectal prolapse with an unknown etiology surgically corrected by resection and anastomosis under general intravenous (IV) anesthesia in an elk bull in detail.

A 10-year-old elk bull weighing 400 kg was referred to the Large Animal Hospital of Kyungpook National University with clinical signs of intermittent tenesmus related to rectal prolapse and anorexia. At the visit to the farm, the elk showed mild to moderate pain, with the rectum approximately 20 cm in length protruding out of the anus. The owner stated that the rectal prolapse had been developing over the previous 5 days and the elk became anorectic as the clinical symptom of rectal prolapse exacerbated. Being the breeding season of the elk, the bull was very dangerous to approach and capture without sedation, necessitating blow gun (AT-NS8010; Anytech, Korea) sedation using 3 mL of xylazine hydrochloride (Rompun, Bayer, German) at approximately 1.18 mg/kg. The elk was not sedated after waiting 10 minutes, and an additional 3 mL of xylazine was injected intramuscularly (IM) using the blow gun. The elk was then mildly sedated with his head down but still was not completely down even after 10 minutes of waiting. The elk finally was down to sternal recumbency and captured 8 minutes after an additional blow gun shot of 2 mL of medetomidine hydrochloride (Tomidin, Provet) at 0.005 mg/kg. Subsequently, 10.4 mL of ketamine hydrochloride (Ketamine 50, Yuhan) was given IM at 1.3 mg/kg. The elk was then positioned in the left lateral recumbency. A 16 gauge and 1.77 inch long IV catheter (BD Angiocath Plus; BD, Korea) was installed at the jugular vein on the right neck, and the fluid therapy with 500 mL of Hartmann dextrose solution (Hartman-Dex Inj, JW), 1,500 mL of Hartmann’s solution (Hartmann Solution Inj, JW), 1,000 mL of 0.9% sodium chloride solution (Normal Saline Inj; JW) was initiated. A systemic antibiotic, enrofloxacin (Baytril 50, Bayer, German) at 6 mg/kg, and an anti-inflammatory drug, prednisolone acetate (Solon: Handong) at 0.5 mg/kg were administered IM to prevent complications and reduce edema and pain. The body temperature, heart rate and respiratory rate were 37.6°C, 30 beats/min, and 12 times/min, respectively. The color of the mucous membranes of the patient was pink, and the capillary refill time (CRT) was less than 1.5 s. Blood was withdrawn for hematology and serum chemistry to be performed later. CBC (Complete blood count) was not performed in timely manner thus the results were omitted whereas the serum chemistry results revealed moderately elevated cholesterol and mildly decreased creatinine (Table 1) (8). The protruded lesion of the rectum was examined quickly and diagnosed with type II rectal prolapse with severe edema and necrosis due to the limited blood supply and contamination. Considering the severity of the condition, an emergency resection and anastomosis was decided upon the owner’s consent. The exposed part of the rectum and perianal area were surgically prepared and draped. A cylinder made of thick board paper wrapped in a plastic bag, 7 cm in diameter, 30 cm in length, and lubricated with a 2% lidocaine hydrochloride (Lidocain Jelly; Sungkwang, Korea), was inserted into the rectum and fixed with the distal marginal part of the inverted rectum using size 2-0 polyglactin 910 (Vicryl; Ethicon, Germany) to prevent movement of the rectum (Fig. 1A). The exposed rectum was divided into quadrants and a repeated resection and suture of one section at a time were performed with simple interrupted suture using the size 2-0 polyglactin 910 as described (Fig. 1B) (3). The sedative and anesthetic drugs were given additionally as required during the surgery. Table 2 lists the amount and route of administration of the drugs. During the surgical procedure, the IV catheter installed on the right jugular vein kept falling out of the vein because of the insufficient length of the catheter necessitating reinstallation of the catheter on the cephalic vein of the left forelimb. Upon the completion of the resection and anastomosis, the cylinder was removed and the rectum was manually placed back into its original location (Fig. 1C, D). The surgical procedure took 1 hour and 15 minutes, including the purse string suture with size 2-0 polyglactin 910 to be removed by the owner 48 h after the surgery. Each strand of the suture material, 10 cm in length, after the purse string suture ligation, was left out to facilitate easy removal by the owner afterward (Fig. 1D). The patient recovered uneventfully in approximately 40 minutes after surgery and appeared to be in better condition than before surgery showing less discomfort related to the sensing of the prolapse, seeking water and food, following resolution of the prolapsed rectum. The caudal view of the patient after recovery from outside the stall confirmed no everted mucosa of the rectum (Fig. 2). The patient was to be fasted for the following 24 h and fed with soft pellet rather than roughage for at least 1 week. The follow up after 4 weeks revealed that the rectal prolapse recurred with intermittent straining 2 weeks after surgery and the patient was on glucocorticoid for 3 days from the recurrence. Despite the efforts, the elk was finally euthanized 1 week after recurrence owing to the exacerbation of the condition, which progressed from the little protrusion of the rectum to the type II rectal prolapse even after glucocorticoid therapy.

Table 1 . Biochemical analysis results at the initial presentation*.

Parameter	Reference interval	Value	Parameter	Reference interval	Value
ALP (IU/L)	33-477	245	Phosphorus (mg/dL)	3.3-8.9	7.2
AST (IU/L)	37-114	104	Total protein (g/dL)	5.4-8.1	6.3
CK (IU/L)	70-920	125	Albumin (g/dL)	2.2-4.0	3.3
GGT (IU/L)	14-159	21	Total bilirubin (mg/dL)	0.1-0.4	0.4
Sodium (mEq/L)	95-164	141	Cholesterol (mg/dL)	25-77	95
Potassium (mEq/L)	3.4-31.3	4.7	Creatinine (mg/dL)	0.96-3.12	0.9
Chloride (mEq/L)	71-113	102	BUN (mg/dL)	13-45	16
Calcium (mg/dL)	6.2-11.2	9.3	Glucose (mg/dL)	48-226	50

*The reference interval is based on adult male elk (8)..

Table 2 . List of the sedatives and anesthetic drugs used before and during the surgery.

Time (minutes before and after surgery)	Drugs	Dose (mg/kg)	Route of administration	Total amount (mL)	Remarks in behavior
-30	Xylazine hydrochloride	0.18	Blow gun	3	No effect
-20	Xylazine hydrochloride	0.18	Blow gun	3	Head down
-10	Medetomidine hydrochloride	0.005	Blow gun	2	Sternal recumbency
-2	Ketamine hydrochloride	1.3	IM	10.4	Left lateral recumbency
55	Ketamine hydrochloride	0.625	IM	5	-
63	Ketamine hydrochloride	0.25	IM	2	-
	Ketamine hydrochloride	0.25	IV	2
	Medetomidine hydrochloride	0.0025	IV	1

Figure 1. (A) A cylinder made of thick board paper wrapped in a plastic bag, 7 cm in diameter and 30 cm in length, was inserted and fixed with the orad part of the rectum. Please note the edema and necrosis of the prolapsed rectum. (B) The protruded rectum was divided into quadrants and repeated resection and suture of one section at a time were performed using a simple interrupted suture. (C) The cylinder was removed upon the completion of the resection and anastomosis. (D) The rectum was manually placed back into its original location, and a purse string suture was performed to prevent the recurrence of rectal prolapse.

Figure 2. Caudal view of the elk bull immediately after recovery. Note that there was hardly any mucosa everted after the resection and anastomosis.

Rectal prolapse can be caused by prolonged tenesmus (1). The predisposing conditions in horses are constipation, diarrhea, intestinal parasites, dystocia, urinary obstruction, proctitis, rectal tears and tumors although they may also be idiopathic (11). The etiology remains unclear in this case because there were no apparent signs of gastrointestinal problems, such as diarrhea or colicky symptoms. The rectal prolapse, in this case, was a sudden onset and the elk maintained his health before the onset of the condition according to the owner. However, the possibility of an internal parasitic infection should not be ruled out because the patient was not provided with dewormer on regular basis. Although little is known about the parasite of the elk, they are known to be hosts for various parasites, including protozoans, cestodes, trematodes and nematodes (7). In addition, the patient was showing intermittent straining, which did not resolve even after a meticulous surgical repair, which led to the recurrence of the rectal prolapse. Another reason which may have attributed to the recurrence of the condition is that the bull was confined in a stall after the surgery separated from the harem during the rut, the breeding season of the elk, until fully recovered. Hence he could not behave true to his primal nature while the elk cows were around in estrus. The elk bulls become aggressive and show their characteristic social behaviors in the rut season (4). Although there is no direct evidence to prove that the condition recurred due to such stress, any stress might adversely affect the patient psychologically and physically.

The present case was diagnosed with a type II rectal prolapse based on the history and the clinical signs of tenesmus and 20 cm long rectal ampulla in full thickness hanging out of the anus. Type I and II rectal prolapses usually respond to medical management and manual reduction although surgical intervention may become necessary when the protruded tissue becomes necrotic (3), which corresponded to the present case. Resection and anastomosis was performed due to the severe edema and necrosis attributed to the impaired blood flow of the intussusceptum for a prolonged duration. Instead of transfixation of the prolapsed rectum using long needles, a cylinder made of thick board paper wrapped in a plastic bag was inserted into and fixed with the intussusceptum via suture, which could minimize the related damage in the large sized rectum of the elk in the present case.

The main challenge, in this case, was sedation and anesthesia for diagnosis and treatment. Xylazine and ketamine are the most widely used combination for immobilization and anesthesia of the cervids (2). The recommended dose varies widely depending on the breeds and duration required (2,9). It is known that 1 mg/kg of xylazine IM followed by 1 to 2 mg/kg of ketamine produces approximately 15 minutes of anesthesia (2). However, it was difficult to decide on the dose and the interval of the additional injections because of the condition of the patient and the lack of experience in this case. The animal was very excited and dangerous to approach even before performing any diagnostic procedure due to the rutting and discomfort related to the rectal prolapse. In addition, the syringe of the blow gun dart only allowed 3 mL of sedatives at a time. There were also concerns about the side effects of xylazine sedation, including ruminal tympany, regurgitation, impaired thermoregulation, and respiratory and cardiovascular depression (2). Furthermore, there was no patient monitoring system in hand. After three blow gun injections with xylazine and medetomidine at 10 minute intervals, the patient was down on sternal recumbency. A succeeding IM ketamine injection produced 55 minutes of stable anesthesia. Two more IM injections, one more IV injection of ketamine, and one more medetomidine IV injection at a lower dose were required for the resection and anastomosis to be complete (Table 2). Although periodic auscultation of the heart, measurement of the body temperature along with observation of the mucous color provided information to assess the status of the patient, minimal resuscitation measure including the oxygen supply and the patient monitoring system including blood pressure measurement should be available for better care of the patient even in field, which is one of the regrets in this case.

Securing the IV route is essential for surgery. After the patient was placed on left lateral recumbency, a 16 gauge and 1.77 inch long IV catheter was installed on the right sided jugular vein. However, the catheter kept falling out of the vein because of the insufficient length and sinking of the vein with gravity owing to the patient’s position. Alternatively, another catheter was installed on the cephalic vein of the left forelimb and was kept securely for continuous fluid therapy. When performing surgery on elk under general IV anesthesia, a longer IV catheter would be required depending on the size and the position of the animal.

Postoperative care was another challenge in this case. Regrettably, dietary management, including fasting and providing soft pelleted feed, was almost the only thing that could be done for the patient considering the nature of the large animal and the safety of the owner. In small animal practice, colopexy is considered to prevent recurrent rectal prolapse (12). However, it is not generally indicated in ruminants as the elk due to the risk of the development of tympany during the procedure in dorsal recumbency and the financial limitations of the owners. The failure to recognize the inciting cause of the rectal prolapse in the first place and realistic limits in postoperative care is believed to have resulted in the recurrence of the condition 2 weeks after the surgery.

A 10-year-old elk bull weighing 400 kg was diagnosed with type II rectal prolapse based on the history and clinical signs. The patient was treated successfully with resection and anastomosis under general IV anesthesia in field. The 4 week follow up revealed that the rectal prolapse recurred after 2 weeks of the surgery and the patient was euthanized after 1 week of recurrence due to exacerbation of the condition. The authors expect that clinicians will find this clinical report helpful establishing chemical restraint protocols, diagnoses and surgical management strategies and anticipating the prognosis of the cervids, including elk, with rectal prolapse.

The authors have no conflicting interests.