Rectal Pull-Through in Dogs

Rectal pull-through is a surgical procedure for removing the rectum and suturing the colon to the anal sphincter, depending on the severity and the location of tumours. However, it is recommended when possible, that a 1.0-1.5cm section of rectum should be left behind to assist in preserving continence.

Leading up to the surgery, for approximately three to seven days, the dog should be placed on a low residue diet (like a low-fiber diet) to reduce the bulk and frequency of defecation. Laxatives should not be used to empty the colon and rectum prior to surgery, due to the requirement of slow intestinal movements. Due to the risk of infection, antibiotics should be given as a preventative measure and given as a course post-surgery.

The patient should be evaluated for surgery and pre-anaesthesia blood tests should be taken to determine the patient is suitable for anaesthesia. There are no restrictions for types of anaesthetic agent for this surgery, and they should be chosen according the patient's general health.

The surgery is performed with the dog in sternal recumbency with the anus slightly elevated to assist the surgeon. The tail should be clipped, bandaged and tied back to allow unobstructed visualisation of the surgical site. The contents of the rectum and the anal glands should be empted by the surgeon prior to preparing the sterile surgical environment. The perineal area along with a suitable margin should be clipped, scrubbed and adequately draped prior to surgery.

The rectum wall is prolapsed and cut though around its circumference, the rectum is then dissected and mobilised by transection of the rectococcygeal muscles and blunt dissection of the rectum along its length. After the rectum is mobilised, it is pulled caudally out of the body and stay sutures are put in place to prevent retraction back into the abdominal cavity.

In order to establish the point of resection, the rectum is palpated or partially opened longitudinally (unless the tumour is around the complete circumference) to determine the point of resection and an adequate margin; this may be done in a single or multiple-step process.

The remaining section of rectum or colon (depending on degree of severity of resection) is anastomosed at the rectal stump at the anus. The anastomosis may be performed with a single layer or dual layers of sutures (usually dependent on the tension). Finally the stay sutures are released, allowing the anastomosed site to sit in the pelvic canal.

In cases of tumours which extend into the distal colon, a modified Swenson’s pull-through procedure may be employed, which is a double approach from the perineal area and from the abdomen. When using the modified Swenson’s pull-through procedure, the dog is placed in dorsal recumbency; a caudal laparotomy is performed, and the section of colon to be removed is determined and clamped with Doyen clamps. After the section of colon is removed, the two stumps are anastomosed together, followed by closure of the abdomen as usual.

Following the abdominal approach, the dog is repositioned in sternal recumbency and the surgery progresses as described above.

The surgery is an effective method of removal of tumours of the rectum in dogs, however, caution must be taken as malignant tumours may spread to the lymph nodes or other organs. The surgery is generally successful, however complications with dehiscence (rupture) of the suturing site can be fatal and metastasis of malignant tumours can result in secondary tumours.

Post-surgery complications include dehiscence of the anastomosed site (usually seen three to five days after surgery), infection from spillage of colon or rectal contents, stricture formation at the site of anastomosis, and fecal incontinence. In order to prevent fecal incontinence, it is recommended to leave a segment of rectum of 1.0-1.5cm in length. Post-surgery, there may be a loss of continence which may resolve over time.

An alternative approach is a pubic ischial osteotomy, which allows better visualisation of the rectum and allows full removal of the affected section without the need to use modified Swenson’s pull-through procedure. However, this approach, whilst convenient for the surgeon, allows a more accurate anastomosis, and has a lower risk of complications compared to the modified Swenson’s pull-through procedure, is traumatic for the patient and requires a longer recovery period.

Postoperative care consists of analgesia (pain treatment), fluid and electrolyte therapy. Water should be offered eight to twelve hours after surgery and stool softeners mixed in with food when the patient starts to eat. An Elizabethan collar may be required if the patient is biting at the surgical site. Hematochezia (bloody stool) and dyschezia (difficult defecation) may occur up to one to two weeks post-surgery with tenesmus (frequent need to defecate) up to two months; these conditions are usually self-limiting and require no treatment.

Fecal incontinence may occur due to damage of the pudendal nerve or the lack of the remaining section of colon to distend to store feces; transient fecal incontinence may occur, with resolution on no particular timeframe. For dogs affected with fecal incontinence, regular cleaning of the perineal area is important for healing and general hygiene of the skin.

Follow-up veterinary care is required to check the rectum digitally for strictures, monitor incontinence, and to check for sites of metastasis.

This type of surgery is expensive and can range in price between $2,000 and $12,000 depending on the severity and spread of the tumors and the technique used (standard rectal pull-through or modified Swenson’s pull-through). A dog with a tumor in the caudal rectum would have a lower treatment cost than a dog whose tumor had spread to the lower colon and required the modified Swenson’s pull-through procedure. Surgical correction of complications like strictures or dehiscence of the anastomosis will increase overall treatment costs.

When planning on resection of a section of rectum, the precise location of the tumour needs to be visualised either by x-ray or ultrasound to determine whether a standard approach or a modified Swenson’s pull-through is required. In cases of severe spread of a tumour extending to the colon, a pubic ischial osteotomy approach may be considered to give the surgeon better visibility of the rectum. Due to the surgery being for treatment of malignant tumours, the chance of recurrence or metastasis is high and needs to be monitored regularly after surgery.

Tumours of the gastrointestinal tract are generally idiopathic which give little in the way of preventative measures. Other causes like rectal strictures, diverticula and perforations can be difficult to predict or prevent.