INTRODUCTION — Abdominal wall hernias can be a significant problem in patients treated with continuous peritoneal dialysis (PD) [1]. A discussion of abdominal wall hernias in patients undergoing peritoneal dialysis will be presented in this topic review.
Other potential complications of PD are discussed elsewhere. (See "Noninfectious complications of peritoneal dialysis catheters" and "Peritoneal catheter exit-site and tunnel infections in peritoneal dialysis in adults".)
INCIDENCE — In the early 1980s, the incidence of abdominal hernia was approximately 10 to 15 percent per year. Historically, the incidence was lower with intermittent than with continuous ambulatory peritoneal dialysis (PD), with the former having an annual rate of less than 5 percent [2].
A subsequent advance, the utilization of a paramedian approach to PD catheter insertion, has significantly reduced the incidence of exit site and incision hernias [3,4]. Hernia rates are currently reported at a rate of 0.04 to 0.08 per patient per year [1,5,6].
RISK FACTORS FOR HERNIA FORMATION — Studies conflict regarding risk factors for hernia formation [4-7]. A large study conducted in the United States of 1864 peritoneal dialysis (PD) patients did not show an association between hernias and patient age, body surface area, PD modality, volume of dialysate, time of largest dwell, or type of catheter used. Cystic disease conferred a 2.5-fold increase in risk for anatomic complications, female sex conferred an 80 percent reduction in risk, and Kt/V ≥2.0 conferred a 52 percent reduction in risk (p <0.05) for hernia [7]. From a pathophysiologic standpoint, these risk factors reflect anatomic, hydrostatic, or metabolic factors that can influence hernia formation.
Anatomic sites — The sites of anatomic weakness that predispose to hernia formation include the inguinal canals, umbilicus, linea alba, patent processus vaginalis, exit site, and site of a prior surgical incision. As an example, the testes descend into the scrotum via the processus vaginalis, which should then become obliterated. However, a patent processus vaginalis has been found in 90 percent of infants at birth and, at autopsy, in up to 37 percent of adults without hernias. Leakage of peritoneal fluid into a patent processus vaginalis can result in the formation of an indirect inguinal hernia.
Previously, the most common location for hernia was the inguinal area (23 percent), followed by exit site (19 percent), umbilical (19 percent), and other incisional site hernias (10 percent) [2]. There is an increase in hernia risk if the PD catheter is placed in an area of anatomic weakness, such as the midline. The incidence of catheter-related hernias has decreased since catheters have been placed in a paramedian location [4]. A later study in patients from the United States showed that hernias comprised approximately 60 percent of all anatomic complications of peritoneal dialysis, with 41.4 percent inguinal, 31 percent umbilical, 23 percent ventral, 3.8 percent femoral, and 0.8 percent intrathoracic [7]. An additional 25 percent of complications were due to either pericatheter or subcutaneous leaks, and 8 percent were due to hydrothorax. Leaks are most commonly located in the pericatheter area [5,6,8].
Anatomic weakness also may account for the apparently higher risk of abdominal hernia in patients with autosomal dominant polycystic kidney disease [9]. The abdominal wall abnormality may be secondary to the same process that results in the increased incidence of cerebral aneurysms, valvular disease, and diverticulosis in these patients. (See "Autosomal dominant polycystic kidney disease (ADPKD): Extrarenal manifestations".)
Hydrostatic pressure — The empty peritoneal cavity has an intra-abdominal pressure of 0.5 to 2.2 cmH2O; this value rises in direct proportion to the amount of fluid infused into the peritoneal cavity [10]. In a review of 61 consecutive PD patients at a single center in Belgium, mean baseline intra-abdominal pressure was approximately 13.5 cmH2O with a two-liter instilled volume, and, as noted in other studies, intra-abdominal pressures rose as instilled volume increased and were higher when ambulatory than when supine [11,12].
However, there does not appear to be an increase in the rate of hernias in patients who are prescribed higher dwell volumes [6,7,13]. This indicates that hernias appear in sites of anatomic weakness and are not absolutely related to dwell volume [6,7,13].
Further elevations in intra-abdominal pressure can be induced by increasing abdominal girth, changing from a supine to standing position, straining due to constipation, weight lifting, and leg lifting [10,14]. The highest pressures, up to 30 cmH2O, have been recorded with coughing. Therefore, efforts should be made to prevent increased abdominal pressure, especially in regard to avoiding constipation. (See "Abdominal compartment syndrome in adults".)
Metabolic factors — Metabolic factors also may play a contributory role. Examples include the adverse effects of malnutrition, uremia, and specific medications on wound healing and cellular proliferation [15].
CLINICAL MANIFESTATIONS — It is important to assess for preexisting hernias and to repair any that are present in any individuals who have chosen peritoneal dialysis (PD) as their dialysis modality. Seventeen percent of patients presenting for PD catheter placement were found to have a hernia prior to the initiation of peritoneal dialysis [16]. Combined hernia repair and PD catheter placement, in experienced hands, does not lead to an increase in mortality, morbidity, or surgical complication rates compared with hernia repair prior to PD catheter placement [17].
Symptoms associated with abdominal hernia in PD patients include painless swelling at different sites, discomfort or disfigurement, and problems related to a complication from the hernia. As an example, these patients may develop intestinal obstruction, incarceration, or strangulation and present with symptoms of peritonitis. Thus, underlying intestinal pathology should be considered in any patient with a hernia who develops peritonitis [11,18].
The migration of peritoneal fluid into adjacent body structures (ie, dialysate leakage) can lead to either abdominal wall or genital edema. As an example, scrotal or labial swelling can be caused by dialysate flow through a patent processus vaginalis or the peritoneal membrane, followed by tracing of the fluid inferiorly into the scrotal or labial wall. Dialysate fluid can also traverse the peritoneal membrane into the soft tissues of the anterior abdominal wall, leading to abdominal wall edema. Patients with this complication often present with increasing abdominal girth in conjunction with decreased peritoneal fluid drainage volume.
Pericatheter fluid leakage can be related to catheter break-in time. Patients who start their peritoneal exchanges within 72 hours of catheter placement (urgent-start PD) are more likely to have a pericatheter leak than those who start their peritoneal dialysis exchanges one or two weeks after placement, which allows for postoperative healing of the catheter exit site [19]. This type of leakage is usually not dangerous and can often be remedied by using low-volume supine dialysis. (See "Noninfectious complications of peritoneal dialysis catheters".)
More serious complications, such as small bowel obstruction or intestinal incarceration and/or strangulation, are rare. Incarcerated hernias can be seen in the umbilical, inguinal, or incisional area of the PD catheter [20]. They are most likely to occur with catheter and other incisional site hernias and are least common with inguinal hernias. Incarceration and strangulation of the bowel are also more likely when the hernia is small, preventing the free movement of bowel into and out of the hernia sac. Presenting features of this complication are variable, ranging from tenderness at the site of the hernia sac to bowel perforation or obstruction.
DIAGNOSIS OF HERNIAS AND DIALYSATE LEAKS — Several methods can be used to detect hernias in peritoneal dialysis patients. These are discussed in detail separately. (See "Modalities for the diagnosis of abdominal and thoracic cavity defects in peritoneal dialysis patients".)
PREVENTION — Several measures can be taken in the preoperative and postoperative periods to reduce the risk of hernia formation and dialysis leaks. These include:
●Detection and repair of preexisting hernias [16].
●Detection of a patent processus vaginalis by the surgeon during insertion of the peritoneal catheter.
●Paramedian versus midline catheter placement [4].
●Placement of the deep cuff of the peritoneal dialysis catheter in the subaponeurotic area (instead of rectus muscle) [21].
●Liberal use of agents in the early postoperative period to prevent constipation and coughing.
●Laparoscopic placement with rectus sheath tunneling [22,23].
●A catheter break-in period of at least two weeks. If dialysis is needed in the interim, it can be provided with either the use of a low-volume (1.0 to 1.5 L), supine, rapid cycling (six exchanges per day) PD regimen or with hemodialysis. The latter modality is preferred if there are concerns about inadequate dialysis by using low-volume PD.
TREATMENT
Surgical repair of hernias — Patients who develop a hernia after the initiation of peritoneal dialysis (PD) should undergo elective repair, if possible. The use of a polypropylene mesh prosthesis appears to decrease the risk of hernia formation postoperatively and allows for the reinstitution of peritoneal dialysis within several days of the hernia repair [24-26]. In a retrospective review of 58 hernia repairs in 50 patients, recurrence rates were 12 percent without use of mesh and 0 percent with mesh hernioplasty. There were two cases of peritonitis, and, although unclear in the manuscript, it appears that these resolved with antibiotics alone without the need to remove mesh [26].
Peritoneal dialysis may frequently be resumed within several days of the herniotomy, using low-volume, supine, rapid cycling PD (which decreases intra-abdominal pressure) with gradual reinstitution of the former PD regimen in the subsequent two- to four-week period [16,25,27,28]. At the University of Toronto, intermittent peritoneal dialysis is begun 48 hours after surgery and PD is gradually reintroduced. In a retrospective study of 50 consecutive patients at this center, hemodialysis was not required in any patient, and leakage or early hernia recurrence was not observed [27]. The use of cough suppressants or laxatives, as needed, may decrease the risk of intermittent rises in intra-abdominal pressure [29].
Treatment of dialysate leaks with or without hernia
Overview — Patients with uncomplicated peritoneal leaks (ie, without an associated hernia) can initially be treated with either low-volume supine PD with a dry day or hemodialysis. In one study in which this technique was attempted for four weeks, the rate of relapse was 52 percent [5]; however, repeating this technique for an additional four weeks resulted in resolution of the leak in 86 percent of the remaining patients.
Abdominal wall or genital edema — The patient with uncomplicated abdominal wall or genital edema (but without an associated hernia) should be treated conservatively with bed rest and temporary hemodialysis. A rest period of three to seven days may be sufficient for the tissue defect to heal and allow for the reinstitution of PD.
Recurrent abdominal wall edema can be treated with a more prolonged course of hemodialysis (at least four to six weeks) or surgical repair. Surgery may be difficult if there is no obvious hernia present, since the site of the leak may not be defined. In this setting, imaging studies, as described above, may help localize the defect [8,30].
In contrast, the treatment of recurrent genital edema is dependent upon the etiology of the edema:
●A patent processus vaginalis should be surgically repaired. This anatomic defect can be detected by technetium scanning, computed tomography (CT) with intraperitoneal contrast, magnetic resonance imaging (MRI) scanning without gadolinium, or exploratory laparotomy [31,32].
●Migration of fluid via the anterior abdominal wall can be treated as previously described. This migration occurs via either small rents in the peritoneal membrane or pericatheter leak.
If it is unclear if genital wall edema is secondary to dialysate leakage, then confirmation of the leakage can be performed by imaging techniques [18,30]. Sequential imaging can be used to determine if dialysate fluid travels outside of the peritoneal cavity [18,30,33].
SUMMARY AND RECOMMENDATIONS
●Abdominal hernias can be a significant problem in patients treated with continuous peritoneal dialysis (PD). Hernia rates among patients undergoing PD are currently reported at a rate of 0.04 to 0.08 per patient per year. (See 'Incidence' above.)
●From a pathophysiologic standpoint, the principal risk factors for the hernia formation reflect anatomic, hydrostatic, or metabolic factors. (See 'Risk factors for hernia formation' above.)
●Symptoms include painless swelling at different sites, discomfort or disfigurement, and problems related to a complication from the hernia. The migration of peritoneal fluid into adjacent body structures can lead to either abdominal wall or genital edema. More serious complications are rare but include small bowel obstruction and intestinal incarceration and/or strangulation. (See 'Clinical manifestations' above.)
●Several measures can be taken in the preoperative and postoperative periods to reduce the risk of hernia formation and dialysis leaks, including evaluation and repair of existing hernias, the location and procedures used for peritoneal dialysis catheter placement, and methods to decrease intra-abdominal pressure in the postoperative period. (See 'Prevention' above.)
●Patients who develop a hernia after the initiation of PD should undergo elective repair, if possible. The use of a polypropylene mesh prosthesis appears to decrease the risk of hernia formation postoperatively. Low-volume supine peritoneal dialysis can often be resumed several days after surgical repair.
●Treatment of a dialysate leak varies in patients with or without an associated hernia. Treatment of an uncomplicated dialysate leak (that is, no associated hernia) can initially be by temporarily stopping PD; by changing to low-volume, supine, or dry day PD; or by a short-term transfer to hemodialysis. Treatment of recurrent leaks depends on the location and etiology of the leak. (See 'Treatment' above.)
