Figure 72-20. Richter hernia. Part of the bowel wall herniates through the defect in the abdominal wall.

The next steps in management include resuscitation followed by urgent surgery. At surgery, an

approach directly over the hernia is used. In all patients, the entire gastrointestinal tract must be

assessed to eliminate causes of obstruction other than the hernia itself. This is done before the hernia is

repaired. The bowel, if viable, is reduced into the abdomen. If difficulty is encountered in reducing the

hernia, the neck of the hernia can be widened. In the case of an inguinal hernia, division of the neck

with or without ligation and division of the inferior epigastric vessels is safe, and the hernia contents

can be reduced into the abdomen. In the case of a femoral hernia, the inguinal ligament can be split

anteriorly and the hernia contents reduced into the abdomen. If the bowel is nonviable, then a bowel

resection can be performed with anastomosis. The hernia is then repaired.

Strangulation

Strangulation of a hernia is a serious and life-threatening condition in which the hernia contents become

ischemic and nonviable. The pathogenesis of this condition involves intra-abdominal contents within the

hernia sac. Straining may push more contents into the sac, and the tense sac then causes pressure at the

neck. This pressure initially produces venous congestion, resulting in edema. Eventually, the pressure is

so great that the arterial supply is obstructed and the contents become gangrenous.

When intestine is involved, in addition to having an irreducible hernia and intestinal obstruction, the

patient is toxic, dehydrated, and febrile. Examination of the abdomen reveals the signs of an intestinal

obstruction, with distention and increased bowel sounds. Absolute constipation and vomiting are other

manifestations. The hernia itself is tense, irreducible, and very tender, and the overlying skin may be

discolored with a reddish or bluish tinge. No bowel sounds are heard within the hernia itself. The

patient commonly manifests a leukocytosis with a predominance of polymorphonuclear leukocytes.

Blood gases may reveal metabolic acidosis.

Management of these patients requires urgent attention to detail. No attempt should be made to

reduce the hernia. Rapid resuscitation should commence immediately, with nasogastric suction and

replacement of fluids and electrolytes. The patient should be given antibiotics. Once the patient is

resuscitated, urgent surgery commences to expose the hernia, open the sac, and assess the viability of

the bowel. More bowel can be pulled into the hernia so that viable bowel can be transected and the

gangrenous portion removed. An end-to-end anastomosis should be performed and the bowel then

reduced into the abdominal cavity. The hernia is then repaired.

Richter Hernia

August Gottlieb Richter in 1785 described a hernia type that bears his name in which the antimesenteric

border of the intestine protrudes into the hernia sac without involving the entire circumference of the

intestine so that intestinal obstruction does not occur (Fig. 72-20). The most common site is the femoral

ring (36% to 88%), followed by the inguinal canal (12% to 36%), and an abdominal wall incision (4%

to 25%). Miscellaneous locations include umbilical, obturator, supravesical, Spigelian, triangle of Petit,

sacral foramen, Morgagni, internal, and diaphragmatic.35 The routine use of laparoscopy by general

surgeons has resulted in an increased incidence at trocar sites such that most surgeons will repair the

fascia for trocar sleeves greater than 5 mm. The surgical treatment is to expose the herniated bowel by

opening the sac. The neck of the sac is enlarged to allow delivery of the bowel into the wound. Any

areas of gangrene are excised and the bowel wall reconstituted. The hernia is then repaired.

Prosthetic Materials

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The development of a wide variety of materials for abdominal wall reconstruction makes it possible to

individualize the selection of prostheses so that they can be used in almost all clinical situations.

Currently available prosthetic materials can be divided into synthetic or biologic depending on their

source. The synthetic prostheses can be further classified as noncomposite heavyweight plastic,

noncomposite heavyweight membrane, noncomposite lightweight plastic, composite, and coated

prosthesis. Although surgeons use the term mesh to refer to all varieties of hernia prostheses, this is

inaccurate as only prostheses that have large grossly visible interstices should be termed meshes.

Microporous material such as expanded polytetrafluoroethylene (ePTFE) have no visible interstices, do

not promote ingrowth as with the mesh prosthesis, and act more like a membrane. In the absence of

infection, synthetic material is preferred to biologic prostheses. The materials that have the longest

track record for routine use in hernia surgery include polyester, polypropylene, either monofilament

(Marlex, Prolene) or polyfilament (Surgipro); Dacron (Mersilene); and ePTFE (Gore-Tex). Synthetic

materials such as polypropylene or polyester work by inciting an intense fibroplastic response to form a

strong scar plate interface. Because of this response, they should not be used adjacent to the viscera

because of the propensity of these materials to erode into intra-abdominal organs, most commonly

intestine, resulting in fistulization. The weight of the polypropylene or polyester meshes, as well as the

size of the pores, is a controversial issue currently. As an example, a 7.5- × 15-cm polypropylene mesh

(Prolene, Ethicon, Inc.) contains about 80 g/m2 of polypropylene, while a polypropylene–

poliglecaprone-25 (Monocryl) lightweight mesh of the same size (UltraPro, Ethicon, Inc.) contains less

than 30 g/m2. One of the ways of reducing the amount of nonabsorbable material in a mesh is to

increase the size of the pores. Many authorities believe that the inflammatory response incited by the

small-pore, heavyweight plastic meshes can lead to chronic pain; a sensation of being able to feel the

mesh; increased stiffness of the abdominal wall with loss of compliance; and shrinkage, which can lead

to recurrence. There is increasing evidence that decreasing the density of polypropylene and increasing

the size of the pores reduces this foreign body response, resulting in less long-term pain than normal

mesh with a similar recurrence rate.36–39 Recently, there have been reports of “burst mesh” or central

mesh failures with the use of lightweight mesh in the repair of large ventral hernias and thus, one

should exercise caution while employing them in repair of massive hernias.40

Table 72-2 Classification and Examples of Prosthetic Materials Currently

Available for Hernia Repair

When contact of mesh with viscera cannot be avoided, either a nonmesh material such as ePTFE alone

or a dual-layered prosthesis with a standard plastic mesh on the side facing the abdominal wall and

ePTFE facing the viscera should be used. Because ePTFE heals by encapsulation rather than

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incorporation as with the mesh prostheses, it does not have the propensity to erode or fistulize which

makes it suitable for use adjacent to abdominal viscera. This lack of incorporation has a downside in

terms of increased susceptibility of ePTFE to infection, and when these do get infected, they almost

always have to be removed. On the other hand, the incorporated mesh materials such as polypropylene

can commonly be salvaged when infected. To address this issue, manufacturers have developed

temporary or biodegradable adhesion barrier materials to coat the mesh on the side facing the viscera to

prevent adhesions without the need for ePTFE (Table 72-2). The injured peritoneum forms a mesothelial

layer as quickly as 5 to 7 days with the adhesion barrier products being degraded over the course of an

average of 30 (range 28 to 240) days.41 Neither the adhesion barriers nor ePTFE can completely

eliminate adhesions. Patients who undergo laparotomy after either type of prosthesis has been placed

intra-abdominally are routinely found to have significant adhesions to the device. However, these

adhesions tend to be filmy and easily taken down. It remains to be seen if the long-term performance of

coated prostheses compares to ePTFE with its long track record.

The role of biologic tissue matrix in ventral hernia repair has evolved over the last few years. These

materials are derived from human, porcine, or fetal bovine skin; porcine small intestine submucosa; and

bovine pericardium and are processed to remove hair, cells, and cell components as well as other

antigens present in the matrix, leaving only the highly organized collagen architecture with the

surrounding extracellular ground tissue.32 The matrix acts as a scaffold to allow native tissue and

neovascularization to infiltrate the healing wound and promote strong tissue in-growth that limits

contraction. These properties, theoretically, lead to increased resistance to infection. Some biologics

undergo further processing to increase the crosslinking between collagen fibers and to decrease

susceptibility to degradation by collagenase. In general, these materials possess the physical and

mechanical characteristics of a clinically acceptable surgical mesh in that have sufficient mechanical

strength to withstand the physiologic and anatomic stresses of the abdominal wall.42–44

Because of the properties mentioned above, it is felt by some surgeons that the best indication for

biologic prostheses is in contaminated wounds, where a synthetic prosthesis may be contraindicated.

They are not useful in grossly infected wounds presumably because of the high collagenase content

present, which destroys them. It should be noted that none of the biologic prostheses are regulated by

the U.S. Food and Drug Administration (FDA) as a medical device and are typically approved under a

510 (K) approval process which is primarily based on safety. These materials were introduced into

clinical practice and used in contaminated fields without prior FDA approval or clearance for this

indication.45 Another major argument against them is their expense, as they generally cost 20 to 30

times that of the plastic prostheses. The majority of evidence for the use of biologic prostheses for

hernia repair is based on retrospective studies and mostly in clean procedures. Pooled results from 635

patients treated with three different biologic materials have revealed a recurrence rate of up to 18% to

30% at 2 years with biologic prostheses.43,45 Retrospective study with long-term follow-up (>5 years)

with the use of porcine acellular dermal matrix for repair of incisional hernias at risk for infection showed

a recurrence rate of 20% and 53% when used as an onlay or intraperitoneal sublay technique compared

to 80% when used as a bridge in either inlay or sublay position, with particularly high recurrence rates

seen in contaminated (71%) and grossly infected (100%) wounds.46 Although these materials allow a

single stage repair of hernias in a contaminated field, with no or little need for mesh removal in case of

subsequent wound infection, the high rate of recurrence with the use of biologics, especially in

contaminated fields, remains a concern.

A major factor in the popularity of biologic materials for hernia repair is reluctance among many

surgeons regarding the use of synthetic mesh in clean-contaminated and contaminated fields, although

currently available evidence does not support this view. A retrospective review evaluating lightweight

polypropylene mesh placed in a sublay position, in clean-contaminated and contaminated cases revealed

a 14% surgical site infection rate (7.1% for clean-contaminated and 34% for contaminated cases) and a

7% recurrence rate at a mean follow-up of 10 months.47 Results from this and other similar experiences

challenge the surgical dictum contraindicated in a contaminated surgical field. Even when infectious

complications occur, synthetic macroporous mesh materials can often be salvaged without the need for

removal.

Another interesting area of research is development of novel materials which integrate the desirable

qualities of both biologic and synthetic mesh materials. Examples of such materials include Phasix®

mesh (Davol, Warwick RI) which is a long-term resorbable mesh composed of monofilament poly-4-

hydroxybutyrate, TIGR Matrix Surgical Mesh® (Novus Scientific) which is composed of fast and slow

degrading synthetic reabsorbable fibers (Glycolide, lactide and trimethylene carbonate). These materials

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