Parastomal and Perineal Hernias
Parastomal hernias are incisional hernias created by making a defect in the abdominal wall during stoma creation (Figure 10.1). The development of parastomal hernias depends on patient factors, the type of stoma, and technique used to construct the stoma. The incidence is estimated to be 1.8%-28.3% for end ileostomies, 0-6.2% for loop ileostomies, 4-48% for end colostomies, and 0-30.8% for loop colostomies.  Studies with long follow-up have shown the hernia rate after colostomy creation to be more than 50%. Risk factors include advanced age, obesity, wound infection, increased intra-abdominal pressure, COPD, inflammatory bowel disease, malignancy and use of steroids.   The technique used to construct the stoma has been shown to affect the rate of hernia. Emergency surgery, poor site selection, open vs laparoscopic approach, abdominal wall strength and the size of the fascial aperture increase the risk. One study with mean follow-up of 26 months demonstrated that no patient with an abdominal wall aperture diameter ≤25 mm developed a parastomal hernia.
Patients with parastomal hernias may present with minimal or no symptoms, or present with symptoms that range from mild peristomal discomfort, difficulty in maintaining the stoma appliance, dermatitis, stoma prolapse, cosmetic disfigurement, bowel obstruction and strangulation. These symptoms may impact patient quality of life.
Extraperitoneal tunneling, stoma-fascia fixation, stapled ostomy creation, and prophylactic mesh reinforcement have been described as means to prevent parastomal hernias. Extraperitoneal tunneling is associated with lower rate of parastomal hernias but increased operative times and rate of complications. Data showing decreased incidence of parastomal hernias after prophylactic mesh placement using either biologic or synthetic mesh in a preperitoneal or sublay position have been inconclusive.  A meta-analysis of randomized trials showed that the rate of parastomal hernias was significantly decreased with prophylactic mesh placement except when considering only trials in the last 5 years. A multicenter randomized double-blind trial showed that there was no significant difference in parastomal hernia rates at 3-year follow-up between patients with and without prophylactic mesh.
Most patients with parastomal hernias can be managed conservatively by enterostomal nurses with stoma belts and optimizing stoma appliances. Less than 20% of patients will require parastomal hernia repair. All surgical approaches have a risk of recurrence. Local suture repair is simple in design but has >70% recurrence rate.   Relocation of the stoma has a significant combined risk of recurrent hernia at the old site, hernia at the new stoma site and hernia at the laparotomy/laparoscopy site of 24-86%. Intra-abdominal repair with mesh (Sugarbaker or keyhole, performed open or minimally invasive) is the most commonly used technique with recurrence rates of 2-16%. Hernia contents are reduced back into the abdominal cavity and mesh is placed anterior to the rectus or external oblique fascia (onlay) or below the fascia and muscular layers (preperitoneal or sublay technique). Laparoscopic, robotic and open approaches have been described. Synthetic prosthetic mesh materials include polypropylene, polyester or ePTFE. Composite mesh has been specifically designed to be used in parastomal hernia repairs with a 3% complication rate. Biologic mesh has similar complication rates when compared to prosthetic mesh with increased risk of recurrence and significantly increased cost.
Perineal hernia is a weakness of the endopelvic fascia and musculature leading to herniation of intraabdominal and pelvic organs such as small bowel, colon, omentum, uterus, and bladder (Figure 10.2). The incidence of perineal hernias ranges from 0.6 to 7%  and most frequently occurs after abdominoperineal resection (APR), especially extralevator APR, sacrectomy, and pelvic exenteration. Risk factors include smoking, chemoradiation therapy, poor nutrition, perineal wound infection, female gender and perineal defect closure method.
Repair may not be indicated in asymptomatic patients unless there is progressive increase in size. Patients who develop pain, discomfort on sitting or standing, urinary symptoms, intestinal obstruction, skin breakdown, wound dehiscence or evisceration will require surgical intervention. Several techniques have been described including primary repair via abdominal, perineal or combined abdominal and perineal approach, repair with insertion of biologic or prosthetic mesh, omentoplasty and perineal reconstruction with myocutaneous flaps. , Mesh repair is associated with lower recurrence rate than primary suture repair.  Abdominal approach can be done laparoscopically or robotically and may provide superior visualization.    Based on a systematic review of 21 studies, perineal and laparoscopic approaches are currently the most commonly used techniques. Perineal approach with the use of mesh demonstrated good results with 5% rate of recurrence. Plastic surgery perineal flap reconstruction, such as rectus abdominis muscle (VRAM, TRAM), gluteus, and gracilis muscle flaps, have been used to close perineal defects after APRs and can also be used to close perineal hernia defects. Comparative studies do not conclusively show better outcomes for one technique over another and the perineal hernia repair option is therefore individualized for each patient.
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