Small Animal Surgical Emergencies. Группа авторов
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whereas a complete prolapse occurs when all layers of rectum are protruding through the anal orifice [6, 7]. A digital rectal exam is a critical part of the physical but may be impossible in more severely affected patients at the time of presentation. Additionally, a complete prolapse must be differentiated from a prolapsed intussusception which is a surgical emergency. To differentiate the two conditions, the clinician should pass a blunt, lubricated instrument or thermometer between the prolapsed tissue and the anal wall. The instrument tip cannot be advanced due to the presence of the fornix between the rectum and the anus in cases of rectal prolapse (Figure 7.1) [5].
Depending on the underlying cause of the prolapse, patients may present dehydrated, hypovolemic, hypotensive, tachycardic, painful, and exhibiting other signs consistent with shock. These patients should be stabilized with intravenous fluids and pain medications prior to pursuing additional diagnostics or treatment. In many cases, patients are relatively stable, even when suffering with large, complete prolapses. The affected tissues can exhibit severe edema, swelling, and congestion. Viability of the prolapsed tissues must be determined; evidence of significant trauma or necrosis are both indications for urgent surgical intervention for rectal resection and anastomosis.
Diagnostics should be tailored toward each patient based on the history and physical exam findings. At a minimum, fecal flotation, fecal culture, complete blood count, serum chemistry, urinalysis with or without urine culture, and abdominal radiography or ultrasonography should be recommended. Abdominal computed tomography, thoracic radiographs, and endoscopic imaging and biopsies can also be considered, especially in cases of recurrent prolapse or when a neoplastic process is suspected.
Treatment
Correction of the rectal prolapse is only the first step in providing appropriate treatment for these patients. Underlying diseases that contributed to prolapse formation must also be addressed as failure to do so may increase the risk of prolapse recurrence [1, 5].
Box 7.1 Conditions Associated with Rectal Prolapse in Small Animals
Gastrointestinal parasitism
Intestinal neoplasia
Colitis
Proctitis
Intestinal foreign body obstruction
Colonic duplication
Rectal polyps
Rectal sacculation following perineal hernia repair
Dysuria
Urolithiasis
Vaginal prolapse
Dystocia
Prostatitis/prostatic disease
Figure 7.1 Cat with rectal prolapse. Note the minimal ability to insert hemostats along the prolapsed tissue. This is in contrast to colorectal or jejunorectal intussusception, where the hemostat would be able to slide easily into the space between the mucosal layers.
Source: Image courtesy of L. Aronson.
Reduction of Prolapse
Prolapse reduction should be attempted in any patient where the exposed tissue is deemed viable. Most prolapses can be reduced with appropriate interventions.
For partial and smaller, acute complete prolapses, reduction can typically be achieved with the patient heavily sedated. Tissues should be thoroughly lavaged with warm, sterile, isotonic solution and sterile lubrication generously applied. Application of gentle, continuous pressure to the prolapse should result in reduction at which point a purse‐string suture can be placed at the anal mucocutaneous junction, taking care to avoid the anal sac ducts. Monofilament, non‐absorbable suture is recommended for this purpose (2‐0 for large dogs, 3‐0 for small dogs and cats). The suture should be tied tight enough to prevent prolapse while allowing enough space for soft stool to pass without inciting tenesmus. To avoid excessive tightening of the suture a spacer, such as a 3‐cc syringe casing or a finger, is placed in the rectum prior to tightening and tying the purse‐string suture.
For moderate to severe, viable, complete prolapses, patients should be placed under general anesthesia to allow adequate relaxation of the rectum and perineal muscles. Epidural anesthesia can also be useful in preventing rectal spasming and providing analgesia during the reduction process as well as during the recovery. In additional to cleaning the prolapse, hyperosmotic agents can be applied to help reduce tissue edema and swelling. Various agents, including 50% dextrose solution, 70% mannitol, glycerol solution, and granulated sugar can be used for this purpose, although there is no evidence that supports the effectiveness of one agent over another. Again, gentle and consistent pressure applied to the prolapse will promote reduction. For large prolapses, this process can be time consuming but rewarding (Figure 7.2). Once reduced, a rectal exam should be performed to ensure normal anatomy prior to placement of a purse‐string suture as described above.
With the prolapse reduced, further treatment should focus on medical management of the primary inciting cause. Additionally, patients should be fed a low‐residue diet and placed on a stool softener such a lactulose or polyethylene glycol while the purse‐string suture is in place. Anti‐spasmodic medication such as aminopentamide hydrogen sulfate (Centrine®, Fort Dodge Animal Health; 0.01–0.03 mg/kg subcutaneously, intramuscularly, or orally every 8–12 hours) can be considered, but should be used cautiously as there is the potential for serious adverse effects, including ileus [8]. Topical steroids have also been recommended by some to treat anorectal inflammation [5]. Purse‐string sutures should be left in long enough to allow medical therapies to take effect in treatment of the primary disease process. Published recommendations range from five days to two weeks and are likely related to the severity of the prolapse and initial clinical signs [5, 6, 8].
Surgical Intervention
Rectal resection and anastomosis is indicated for patients presenting with prolapsed tissues that are necrotic, severely traumatized, or irreducible. Surgery should be performed as soon as the patient is deemed stable for general anesthesia. Epidural anesthesia can be useful for improving analgesia. Antibiotics that target Gram negative and anaerobic bacteria, such as a second‐generation cephalosporin, are administered perioperatively.
Figure 7.2 (a) Two‐year‐old female intact mixed‐ breed dog presented for rectal prolapse of 24 hours' duration. Note the severe congestion and edema of exposed rectal mucosa. (b) Post‐prolapse reduction. The patient was placed under general anesthesia and given an epidural. Granulated sugar was applied to edematous mucosa as a hyperosmotic agent. A purse‐string suture was placed following reduction and patient was treated for colitis and intestinal parasitism.
The perineal region is clipped widely for surgery. The patient is positioned in sternal recumbency with the pelvis raised on a padded rectal stand. If a rectal stand is not available, the pelvis can be elevated by using vacuum sandbags or other positioning devices (Figure 7.3). The area is prepped and draped. Placement of a sterile cylindrical structure, such as a syringe, blood collection tube, or test