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INTRODUCTION — A parastomal hernia (PSH) is a type of incisional hernia that occurs at the site of the stoma or immediately adjacent to the stoma. It forms when the abdominal wall defect, the trephine, is continually stretched by the tangential forces applied along the circumference of the abdominal wall opening .
The construction of an ostomy and the management of patients with an ileostomy or colostomy are reviewed separately. (See "Surgical principles of ostomy construction" and "Management of patients with a colostomy or ileostomy".)
INCIDENCE — A PSH is the most frequent complication following the construction of a colostomy or an ileostomy. It has even been suggested that a certain degree of PSH is almost inevitable .
The reported incidence varies widely and is related to a number of factors including: the lack of a standard definition, type of ostomy constructed, and variability in the duration of follow-up after ostomy construction [3-13]. A minor degree of parastomal weakness is present in many patients and does not represent a true hernia .
A literature review found that PSH occurs in 1.8 to 28.3 percent of patients with end ileostomies, 0 to 6.2 percent with loop ileostomies, 4.0 to 48.1 percent with end colostomies, and 0 to 30.8 percent with loop colostomies . The lower rates for loop ostomies are related to the temporary nature of most of these stomas and the short duration of follow-up. Most parastomal hernias occur within the first two years from construction, and studies with longer follow-up have reported higher PSH rates.
A radiologic classification scheme using findings from cross sectional imaging has also been developed . This scheme distinguishes between possible contents of the hernia sac, including omentum, the loop of bowel forming the ostomy, and other loops of bowel not forming the ostomy.
While these classification schemes may be useful in research and for academic discussions, in practice there is little need for such a system since management is based on the symptoms induced by the hernia, rather than differences in the hernia composition, which may be difficult to appreciate on physical examination.
RISK FACTORS — Patient characteristics that have been associated with an increased risk of PSH formation include obesity, weight gain after ostomy construction, poor nutritional status, immunosuppressive drugs (eg, corticosteroids), emergency construction of a stoma, chronic or recurrent increases in abdominal pressure (chronic coughing), infection, and underlying disease such as malignancy or inflammatory bowel disease [18-22]. Of these, the association with obesity, defined as waist circumference >100 cm or body mass index >30 kg/m2, is best supported by clinical evidence [7,22].
Technical factors that might influence the risk of PSH formation include stoma placement, surgical technique for ostomy construction, and abdominal wall strength [23,24]. The size of the trephine may be particularly important. An analysis of the forces acting upon the trephine that cause dilatation, thus a hernia, revealed that the larger the trephine radius, the stronger the tangential force pulling the trephine apart . This physical analysis supports the clinical findings that PSH is less common following an ileostomy than a colostomy or end stoma as compared to a loop stoma .
There is also increasing evidence that herniation in general is the result of an intrinsic defect in collagen metabolism and wound repair [25-27]. Hence, prosthetic mesh has been introduced to minimize tension on fascia in hernia repairs.
PREVENTION — The development of parastomal hernia (PSH) after construction on an ostomy has, in different studies and different techniques, occurred in 0 to 48 percent of patients. (See 'Incidence' above.) In an attempt to reduce the rate of PSH, the current focus is on modifying risk factors for PSH formation prior to surgery and on better primary stomal construction techniques to strengthen the abdominal wall [28-36].
The best available data on prevention of PSH comes from a randomized trial in which 54 patients who required a colostomy following an abdominal perineal resection; the patients were assigned to an ostomy construction with or without mesh in the sublay position (figure 2) . (See 'Intraabdominal repair with mesh' below.) There were significantly fewer parastomal hernias in the mesh group (15 versus 41 percent) with no difference in complication rates. There were no episodes of mesh intolerance or mesh removal during the two year follow-up period.
CLINICAL MANIFESTATIONS — Most patients with a PSH are asymptomatic and do not require surgical repair. They typically present with a bulge at the site of or adjacent to the intestinal stoma, with or without pain (picture 1). Symptoms range from mild abdominal discomfort, back pain, intermittent cramping, distention, nausea, vomiting, diarrhea, constipation, and a reducible hernia, to severe abdominal pain, fever, and an unreducible hernia, which can be signs of a life-threatening complication. (See 'Complications requiring surgical intervention' below.)
DIAGNOSIS — Diagnosis is based on characteristic findings of a parastomal hernia on physical examination. After removal of the appliance, the patient is examined in the standing position and asked to perform the Valsalva maneuver. A hernia and the paracolostomy or paraileostomy tissue can be identified by digital exploration [15,28]. Diagnostic imaging to evaluate subclinical PSH in patients with a negative physical examination is unnecessary.
COMPLICATIONS REQUIRING SURGICAL INTERVENTION — There is a low rate of life threatening complications associated with PSH [14,15,37,38]. Urgent or emergent surgical repair because of the risk of ischemic bowel is necessary for patients with a high grade obstruction resulting from strangulation or an unreducible hernia.
Patients with the following signs or symptoms can be repaired electively:
NONSURGICAL MANAGEMENT — Surgical repair is avoided in most patients with no or mild symptoms because of the high recurrence rates. While no randomized trial has been conducted, most patients with mild symptoms can be managed with an ostomy hernia belt [2,14].
These patients should be educated about signs and symptoms of obstruction, strangulation, and infarction of bowel and instructed to contact the surgeon's office promptly if these symptoms occur. Delays in diagnosis of ischemic bowel can be life-threatening and may result in severe electrolyte imbalance, sepsis, and death.
SURGICAL REPAIR — The techniques for repair of PSH include:
A multitude of different approaches has been reported; there is no ideal repair and all are associated with varying recurrence rates. Complicating the assessment and comparison of the success of the different repair techniques is that most can be performed using various standard surgical procedures, including a local open repair at the stoma site, laparotomy, or a laparoscopic approach (figure 3).
Repair using prosthetic mesh — The high local failure rate of direct fascial repair for incisional, inguinal, and parastomal hernias and the evidence for defects in collagen metabolism (see 'Risk factors' above) led to the development of local repairs with prosthetic mesh, which is the most common method of PSH repair (figure 4).
The overall success rate for a repair with mesh is relatively high compared with repair without mesh, although all of the reports are nonrandomized, include small patient numbers, use different techniques, and have variable follow-up. However, a mesh repair is still associated with a local failure rate of 4 to 30 percent [39-47]. Furthermore, complications such as contamination of the mesh and fistula formation, while very rare, can be devastating .
Direct fascial repair with mesh — In this technique, an incision is made in the abdominal wall well away from the stoma and a subcutaneous dissection along the rectus and oblique fascia is performed circumferentially around the stoma. The content of the hernia is reduced into the abdomen and abdominal wall defect is closed using a tension free mesh repair. While all of the series describing this technique are small, nonrandomized, and lack long-term follow-up, these reports describe low complication rates and recurrence rates of 0 to 20 percent. The use of closed suction drains overlying the mesh appears to reduce complications resulting from seroma collections . However, the use of drains to minimize the risk associated with seroma formation needs to be balanced against the possible risk of mesh infection.
The advantages of a direct fascial repair are: (1) that it avoids the need for a formal laparotomy and (2) it does not require relocation of the stoma. A disadvantage is that undermining the skin around the stoma risks ischemic injury to the skin, which can result in significant management problems with the stoma appliance. Furthermore, the risk of infection contaminating the mesh is higher than intraperitoneal placement of mesh.
Intraabdominal repair with mesh — By far the most common approach to PSH repair is an intra-abdominal repair with a prosthetic mesh. The mesh may be placed above the fascia (onlay technique) or below the fascia and muscular layers (preperitoneal or sublay technique) (figure 5) [25,41,44,48-59]. Insertion of mesh into the abdominal wall defect (inlay technique) has been abandoned because of high failure rates.
The technique for mesh repair is described in detail separately. (See "Overview of abdominal hernias", section on 'Mesh repair'.)
The onlay technique has the advantage of being technically a more straight forward repair and avoids a large intra-abdominal dissection. It is associated with a higher risk of contamination and sepsis than the sublay technique. The sublay technique has a higher risk of adhesions and intestinal obstruction [41,49]. Identifying the best suited material for the mesh and establishing the best site for the placement of the mesh are the main problems with this technique. Similar to the surgical experience with incisional hernia repairs, the sublay technique is associated with fewer recurrences because intra-abdominal pressure does not dislocate the mesh from the repair .
There are several variations on the technique to place the mesh. The common aspect of all of the approaches is the reduction of the hernia contents into the abdominal cavity and closure of the defect by securing a piece of mesh under the defect with wide overlap onto the normal abdominal wall. The loop of bowel forming the ostomy is either brought out directly through a defect in the mesh, the "key hole" technique, or around the mesh, similar to the extraperitoneal ostomy construction. The bowel loop exiting at the stoma site is secured to the lateral and anterior abdominal wall and then a large piece of mesh is attached to the anterior and lateral abdominal wall over this loop of bowel, excluding all other bowel loops from contacting or protruding through the abdominal wall at the trephine for the stoma.
Laparoscopic mesh repair — Reports of decreased patient morbidity and improved outcomes with laparoscopic tension-free mesh repair of ventral and incisional hernias have led surgeons to apply these techniques to the repair of PSH. The Sugarbaker technique and modifications thereof have been widely used in laparoscopic repairs since it avoids the need for making apertures in the mesh, which make laparoscopic placement more difficult [55,57]. Short-term results are promising (recurrence rate less than 2 percent) [25,61], but longer term results (more than 24 months) are not available (figure 2).
There is very little data to determine which patients with PSH are best treated via a laparoscopic approach or an open approach. Based upon the experience with midline incisional hernias, a laparoscopic approach is best offered in patient with a smaller (<8 to 12 cm) hernia. Laparoscopic repair is also best reserved for when the surgeon does not anticipate extensive intestinal adhesions or extensive anterior peritoneal wall scarring from prior surgery .
Biologic substitutes for prosthetic mesh — The most recent approach for PSH repair is use of biologic tissue instead of prosthetic mesh [43,63-66]. The theoretical advantage is that it avoids the placement of synthetic material near the bowel and near a highly contaminated site, the stoma; however, biologic materials can cost thousands of dollars per piece. A review of four retrospective studies that included 57 patients with a PSH repaired with a biologic graft found a recurrence rate of 16 percent and wound complication rate of 26 percent . This is comparable to the failure rate of PSH repair using prosthetic mesh. (See 'Repair using prosthetic mesh' above.)
While the data are limited regarding the use of biologic tissue substitutes for PSH, it should be considered in patients who are at especially high risk for synthetic mesh complications, such as inflammatory bowel disease patients.
Relocation of the stoma — Historically, the most common approach to a symptomatic PSH was to relocate the stoma to another site on the abdominal wall. This approach is to be generally avoided because the construction of a new stoma at a new site is associated with the same high risk of hernia formation as the primary stoma operation [39,68]. The local recurrence rate is approximately 36 percent (range 0 to 76 percent) and complication rates are as high as 88 percent [38,39,47,68]. This wide range of recurrence and complication rates reflects the variations of the definition of a PSH, type of stoma, size of defect, indications for a repair, length of time of follow-up, and whether or not the PSH is symptomatic.
Direct repair of the fascial defect — To address the high recurrence rate with relocation of a stoma, surgeons performed direct repairs of the hernia similar to suture repairs of inguinal and incisional hernias. A direct fascial repair involves reducing the size of the hernia defect by reapproximating the fascial edges of the trephine with permanent sutures. A direct local repair involves a dissection of the fascia at the site of the stoma. This approach can be performed at the local site externally or via a laparotomy incision or laparoscopically.
This approach is also generally avoided because the physics of PSH and the nature of the defect are not amenable to this simplistic approach. Another problem with this repair is that it violates an important surgical tenet of successful tissue healing: no tension should be placed on the repair. Recurrence rates for a primary fascial repair are high, ranging from 30 to 76 percent [39,68,69].
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