Silicone elastomer sling for rectal prolapse in cats

Abstract

This study reports 2 cases of recurrent rectal prolapse secondary to anal abnormality in cats. In both cases the anus was wide, leading to a rectal mucosal prolapse during defecation. A silicone elastomer sling was introduced around the anus, and the rectal prolapse was definitively resolved.

Rectal prolapse is usually a consequence of an underlying disorder that produces severe or persistent straining. It may be associated with intestinal diseases that cause diarrhea and tenesmus, anorectal diseases that produce constipation and dyschezia, or lower urinary tract diseases that cause stranguria and dysuria. Management of rectal prolapse involves both prolapse repair and treatment of underlying diseases (1,2).

This study reports 2 cases of recurrent rectal prolapse that were successfully treated with a silicone elastomer sling introduced around the anus.

Case description

Case 1

A 5-year-old, female, neutered, domestic short-hair cat was brought to our clinic due to rectal prolapse. Diarrhea, constipation, or lower urinary tract disease was not present. Complete blood (cell) count and serum biochemistry were within normal limits.

In the previous month, the cat was presented with an episode of anal myiasis which led to anal sphincter musculature destruction. The anus became wide, and although rectal prolapse was frequent, the cat had fecal continence (Figure 1). Several attempts at manual reduction and purse-string suture around the anus were done with no success. The purse-string suture was left for 10 d, but the rectal prolapse recurred immediately after its removal.

Figure 1.

Rectal prolapse in Cat 1. A – Rectum prolapsed 3 to 5 cm after defecation. B – Wide anal opening caused by previous myiasis which led to frequent rectal prolapses.

Colopexy was done twice in an effort to prevent rectal prolapse recurrence, but it was unsuccessful. Finally, a silicone elastomer sling was implanted in the anus to replace the destroyed sphincter musculature with an artificial external anal sphincter (Figure 2). The surgical technique of silicone sling implantation was done as described by Dean et al (3).

Figure 2.

Silicone sling implantation in Cat 1. A – Silicone elastomer. B – A strip of silicone sheeting 0.4-cm wide and 6.0-cm long. C – Bilateral skin incisions 1- to 2-cm long were made just lateral to the anal opening and deepened 0.5 to 1.0 cm by sharp dissection. D – Blunt dissection with curved Kelly hemostatic forceps was used to create a tunnel above and below the rectum joining the 2 skin incisions. E – The strip was passed from left to right, dorsal and ventral to the anus. Care was taken not to twist the strip. F – The ends of the strip were overlapped and tightened to fit snugly around the proximal interphalangeal joint of an assistant’s gloved index finger placed in the rectum. The overlapped sheeting was sutured together with mattress sutures of 3-0 nylon. The long ends of the sling material were trimmed and the sling was placed deeply into the wound. G – The new anal sphincter after the silicone implantation. Subcutaneous tissue was sutured with 3-0 polyglactin 910 and the skin was closed with 3-0 nylon. H – The anal opening 7 d after surgery. Erosion of the sling through the left perineal skin had occurred, and the device was removed. I – On day 15, the device had to be removed because it was rejected. J – Anal opening 2 mo after surgery. It became more narrow than it used to be.

No enema or other preoperative bowel preparation was used. Preanesthesia included intramuscular tramadol (Tramal 50 mg/mL; Pfizer, Sao Paulo, Brazil) at 2 mg/kg body weight (BW), and acepromazine (Acepran 0.2%; Vetnil, Sao Paulo, Brazil) at 0.05 mg/kg BW. Anesthesia was induced with intravenous thiobarbiturate (Thipentax 1g; Cristalia, Sao Paulo, Brazil) and maintained with isoflurane (Forane; Abbott, Sao Paulo, Brazil) administered via a cuffed endotracheal tube and Ayres T-piece circuit. The perineal region was clipped and prepared aseptically. The cat was positioned in sternal recumbency with the tail elevated over the back. Bilateral skin incisions 1.0- to 2.0-cm long were made just lateral to the anal opening and deepened 0.5 to 1.0 cm by sharp dissection. Blunt dissection with curved Kelly hemostatic forceps was used to create a tunnel above and below the rectum joining the 2 skin incisions. A silicone strip 6 cm long and 0.4 cm wide was carefully introduced in the perineal incisions from left to right, dorsal and ventral. The ends of the strip were overlapped and tightened to fit snugly around the proximal interphalangeal joint of an assistant’s gloved index finger placed in the rectum. The overlapped sheeting was sutured together with mattress sutures of 3-0 nylon (Medsuture, Amazonas, Brazil). The long ends of the sling material were trimmed, and the sling was placed deeply into the wound. Another strip of silicone was cut and similarly introduced around the anus and placed deeply into the wound. The subcutaneous tissue was sutured with 3-0 polyglactin 910 (Vycril 3-0; Ethicon, Sao Paulo, Brazil), and the skin was closed with 3-0 nylon.

Postoperative analgesia was provided with tramadol (2 mg/kg BW), SC, q12h for 5 d and meloxicam (Maxican 0.2%; Ouro fino, Sao Paulo, Brazil), 0.1 mg/kg BW, SID, for 4 d. Oral amoxicillin (Amoxicilina 50 mg/mL; Uniao Quimica, Sao Paulo, Brazil) was also administered at 15 mg/kg BW for 10 d.

The cat had pain and tenesmus after sling implantation. A laxative was added to the diet to soften the fecal matter as feces appeared to be impacted in the rectum. Enemas using warm water were also used to alleviate this problem. Although the new anal opening was not narrow (a proximal interphalangeal joint of an index finger could easily fit within the rectum), she appeared to be in pain, and feces were not expelled through the new sphincter.

Tenesmus was present during the next month. On day 14 postoperative, the device had to be removed because erosion of the sling through the perineal skin had occurred. On day 20, the other sling was rejected and also removed. Reimplantation of the sling was not performed. Tenesmus decreased after removal of the device, and she was discharged on day 30.

There were no further rectal prolapse episodes during a period of 5 mo of follow up. The surgery was considered successful, even with the prosthesis rejection.

Case 2

A 6-month-old female cat found on the street was presented with a rectal prolapse of 1.0 to 3.0 cm during every defecation. Diarrhea was not present. The tail was absent and the anal sphincter was atonic. A first attempt of manual reduction followed by a purse-string suture around the anus was done with no success. Colopexy was also performed, and failed to prevent new episodes of rectal prolapse. Rectal prolapse secondary to a congenital rectal neurological abnormality was suspected but electromyograms were not done.

The kitten was submitted to general anesthesia, and a single silicone elastomer sling was introduced around the anus (Figure 3).

Figure 3.

Rectal prolapse Cat 2. A – Rectum prolapsed .5 to 1 cm. The tail was absent in this cat. B – New anal opening after the silicone sling implantation.

Oral amoxicilin (Amoxicilina), 15 mg/kg BW, tramadol (Dorless V 12 mg; Unao Quimica), 2 mg/kg, BID and meloxicam (Maxican 0.5 mg; Ouro fino), 0.1 mg/kg BW were administered postoperatively. A laxative drug was added to the kitten’s diet in order to soften the fecal material. She had tenesmus and pain after the surgical procedure. On day 2, a sling erosion through the perineal skin occurred, and feces passed through the surgical site. The device was removed. On day 4, tenesmus was no longer evident, and the cat was discharged on the same day. One month after surgery, the rectal mucosa showed a slight protrusion through the anus; however, there were no further rectal prolapse episodes.

Discussion

Two cases of fecal continence are described: colonic and sphincteric. Colonic continence depends on the plastic adaptation of the colon smooth muscle to the enlarging fecal mass. This type of continence is retained by the patient with well-managed abdominal colostomy (4,5). Considering the 2 cases described in this study, colonic continence might explain the cats’ habitual defecation in littermates and the absence of fecal incontinence even with a large anal opening.

In contrast with earlier reports, the cause of recurrent rectal prolapse in these cats was anal abnormality (1,2). The first cat had the anal sphincter musculature destroyed by myiasis. The second case was likely secondary to a sphincter neurological abnormality. Both cases had wide anal openings and the rectal mucosa prolapsed through the anus during defecation. To our knowledge, these causes of rectal prolapse have not been previously described.

Colopexy is a surgical technique for treating recurrent rectal prolapse. In a previous study, surgery was successful in all dogs and cats (1). However, in our study, both cats had rectal prolapse recurrence after a correct colopexy technique (6). The problem was solved with a silicone elastomer sling implantation, which created an artificial external anal sphincter. In our experience, other prolapsed cats weren’t successfully managed with colopexy. The patients had acute abdominal pain and tenesmus after colopexy. The effort to defecate probably explains the recurrent rectal prolapse.

Literature reports that complications associated with silicone implantation include tenesmus after initial implantation and infection or erosion of the sling through the perineal skin (3,7) In this report, complications included erosion of the sling through the perineal skin and fistula. The silicone sling was badly tolerated by both cats, but rectal prolapse episodes ceased after the device had been removed. A possible explanation is that the fibrous tissue developed after the surgery provided an anal opening reduction, avoiding recurrence of rectal prolapse.

Tenesmus always occurs after surgical procedures in the perineal region because this region is very sensitive. We tried to reduce this by using analgesics after surgery. Fecal impaction may be explained by anal pain following surgery and an enema could alleviate these signs by softening the feces. Although erosion of the perineal skin occurred, the fibrous tissue prevented recurrence of the prolapse and, therefore, it was unnecessary to replace the silicone prosthesis.

The silicone sling may be a useful technique for recurrent rectal prolapse correction in cats that have anal sphincter abnormality. The fibrous tissue that develops after surgery may increase anal tonus, interrupting rectal prolapse episodes during defecation. However, further studies are necessary to assess the role of fibrous tissue in avoiding recurrence of the rectal prolapse. CVJ