Sharon E. Mace
A hernia is the protrusion of a structure or organ through the tissues that normally contain it. External or abdominal wall hernias are far more common than internal hernias and are the focus of this chapter (Fig. 110.1). Herniorrhaphy is the most common general surgical procedure in the United States and worldwide, accounting for 10% to 15% of all general surgery operations (1–3). Inguinal hernias account for about 75% of herniorrhaphies (4). Inguinal hernia repair is also the most commonly performed pediatric surgical operation (5). It is estimated that 5% of the adult male population has a groin hernia (6), but the actual prevalence may be higher since many hernias are asymptomatic or have only mild symptoms and may be undiagnosed. Abdominal hernias are the second most common cause of small bowel obstruction (6,7).
FIGURE 110.1 Abdominal wall hernias. (Reproduced with permission from Sharon E. Mace, MD, and Dave Schumick of the Cleveland Clinic Center for Art and Photography.)
Males are nine times more likely to have a groin hernia than females, while there is a marked female predilection (10:1) for femoral hernias. Femoral hernias are rare in men and direct hernias are rare in women. The most common hernia in either gender is an indirect inguinal hernia (Table 110.1).
TABLE 110.1
Relative Distribution of Hernias in Men and Women
Age is also a factor affecting the incidence of hernia. For inguinal hernias, there is a bimodal distribution by age—those younger than 1 year and those older than 40 to 55, especially geriatric patients (7).
The cause of hernias is probably multifactorial: weak connective tissue with cellular and extracellular matrix defects, aging, and congenital defects; incisional and recurrent inguinal hernias may be due to surgical wound failure or technical limitations (8). Smoking and malnutrition can impair collagen structure (8). There is also a high prevalence of hernias in patients with connective tissue disorders such as Marfan syndrome, Ehlers–Danlos syndrome, Hurley–Hunter syndrome, and Down syndrome (8–10).
The “shutter mechanism” is a reflex contraction of the internal oblique and transversus abdominis muscles in response to increased abdominal pressure. It causes the inguinal ring to close like a sphincter around the spermatic cord, which protects against herniation. When the abdominal musculature is weakened (e.g., age, malnutrition, wasting, neuropathy), the protective shutter mechanism does not function optimally, and the risk of herniation is increased (11).
Increased intra-abdominal pressure (e.g., ascites, pregnancy, peritoneal dialysis) may also contribute to the development of a hernia. If the transversalis fascia is weakened or thinned or a patent processus vaginalis is present, a hernia may develop. Physical exertion precipitates the development of an inguinal hernia in <10% of patients, except when worker’s compensation is a consideration (12). The fact that athletes such as weightlifters do not have a higher incidence of inguinal hernias supports the current view that a specific episode of physical exertion is not a major risk factor for a hernia.
A reducible hernia is defined as one in which the herniated structures can be returned through the abdominal wall defect back into the abdominal cavity. An irreducible hernia cannot be returned through the abdominal wall defect back into the abdominal cavity. Another term for an irreducible hernia is an incarcerated hernia, which is sometimes mistakenly used to imply an irreducible hernia about to become strangulated.
A strangulated hernia is one in which the blood supply to the herniated structures is compromised. Gangrene may occur if the vascular compromise is not relieved. A strangulated hernia is a life-threatening situation requiring emergency treatment and surgical intervention. Hernias with a small neck or opening and a large sac have a tendency to strangulate. All strangulated hernias are irreducible or incarcerated, but not all irreducible or incarcerated hernias are strangulated.
Hernias can be classified as an external, internal, or interparietal. An external hernia protrudes completely through the abdominal wall to the outside and, thus, can be seen and palpated. Examples include incisional, umbilical, inguinal, and femoral hernias. An interparietal hernia is a rare hernia in which the hernial sac is contained within the abdominal wall. An internal hernia is one in which the herniated part occurs within the confines of a body cavity. Internal hernias include diaphragmatic hernias, hernias through a tear in the mesentery or omentum, and hernias through the foramen of Winslow into the lesser sac. Internal hernias are much less common than external hernias and can be very difficult to diagnose.
Hernias occur where there is a weakness in the abdominal wall so that peritoneum and other internal abdominal structures or organs can protrude through the abdominal wall defect. Thus, hernias represent a failure of the abdominal wall to contain the abdominal structures or viscera. The intestines are the most common structure undergoing herniation, but all intraperitoneal structures can herniate, from a tiny piece of omentum to an entire organ.
Groin hernias, which include inguinal hernias (both direct and indirect) and femoral hernias, are the most common, accounting for 85% of all hernias (80% groin, 5% femoral). Adding umbilical and incisional hernias to groin hernias would raise the total to 95% to 98% of all hernias.
Inguinal hernias are superior to the inguinal ligament, whereas the femoral hernia is inferior to the inguinal ligament (Fig. 110.2). The indirect inguinal hernia passes through the internal (or deep) inguinal ring and into the inguinal canal and lies lateral to the inferior epigastric vessels. The direct hernia lies medial to the inferior epigastric vessels and protrudes through Hesselbach triangle, which is bounded by the inferior epigastric artery, the lateral border of the rectus abdominis muscle, and the inguinal ligament. Of all inguinal hernias, about two-thirds are indirect.
FIGURE 110.2 Inguinal hernias. A: Direct inguinal hernia. B: Indirect inguinal hernia. (Reproduced with permission from Sharon E. Mace, MD, and Dave Schumick of the Cleveland Clinic Center for Art and Photography.)
An indirect inguinal hernia follows the path of a patent processus vaginalis. The processus vaginalis is formed during fetal development to allow the descent of the testes in the male from their original retroperitoneal site into the scrotum (Fig. 110.3). If the processus vaginalis fails to close off after birth, an indirect hernia may occur, allowing abdominal contents to progress down the inguinal canal into the scrotum.
FIGURE 110.3 Processus vaginalis. A: Normal, fusion of processus vaginalis. B: Inguinal hernia, complete failure of fusion of processus vaginalis. (Reproduced with permission from Sharon E. Mace, MD, and Dave Schumick of the Cleveland Clinic Center for Art and Photography.)
A femoral hernia is the protrusion of abdominal contents between the femoral vessels (artery and vein) and the lacunar ligament in the femoral canal. Femoral hernias occur almost exclusively in women and, because of the narrow neck or opening, they frequently incarcerate.
Less common types of abdominal wall hernias include epigastric, pelvic, lumbar, and spigelian hernias. Epigastric hernias are hernias that occur in the midline of the abdominal wall between the umbilicus and the xiphoid. Pelvic hernias involve the protrusion of abdominal contents through areas in the floor of the abdominal cavity. The obturator hernia involves herniation through the obturator foramen and generally occurs in elderly women. Lumbar hernias occur in the superior and inferior lumbar triangles, which are two naturally weak regions of the posterior abdominal wall. Spigelian hernias are protrusions of abdominal contents lateral to the rectus abdominis muscle through the external oblique fascia (Fig. 110.1).
Ventral hernias include umbilical, epigastric, and spigelian hernias. Incisional hernias constitute about 10% of all hernias and result from postincisional weakness of the anterior abdominal wall. Incisional hernias of the abdominal wall occur in up to 20% of postoperative patients and up to 35% to 50% of those with a postoperative wound infection or dehiscence. There is a 6% incidence of trocar site hernias following laparoscopic surgery. Parastomal hernias are reported in nearly half (50%) of ostomies (6).
Umbilical hernias in adults, unlike those in pediatric patients, result from an acquired rather than a congenital defect and are usually due to increased intra-abdominal pressure. Patients with increased intra-abdominal pressure, such as peritoneal dialysis, ascites, pregnancy, or obesity, have a higher incidence of umbilical hernias. Umbilical hernias occur in about 20% of patients with cirrhosis and ascites. Elective repair is often recommended for umbilical hernias in adults since there is a greater incidence of complications, including incarceration and spontaneous rupture than in children and infants (7). Ulceration and perforation are complications that are associated with high morbidity and mortality, especially in cirrhotic patients. Skin changes with maceration and ulceration usually occur before frank rupture occurs and so patients with these findings need referral for urgent repair (6). Strangulation of an umbilical hernia precipitated by rapid fluid removal during paracentesis has been reported. Therefore, before paracentesis is performed, an umbilical hernia should be reduced (6).
PEDIATRIC CONSIDERATIONS
In pediatric patients, the incidence of inguinal hernias is greatest in infancy (age 0 to 12 months) with a peak in the first month of life. The overall incidence of pediatric inguinal hernia is 4%. There is an increased incidence in premature infants, with 30% of infants weighing <1,000 g having an inguinal hernia (9,13).
Inguinal hernia repair is the most common surgical procedure in children (5). As with adults, hernias are much more common in males than females, with a ratio of about 10:1 (5). Most children with an inguinal hernia are asymptomatic; the hernia is discovered by the parent changing the infant’s diaper or by a physician during a routine examination. However, incarceration and strangulation can occur. It has been estimated that 70% of incarcerated hernias occur in infants younger than 1 year (14) and the rate of incarceration in premature infants with an inguinal hernia is as high as 31% (5). Most incarcerated hernias (90%) can be reduced outside the operating room (15). As with adults, if the hernia cannot be reduced, immediate surgery is warranted owing to the risk of subsequent strangulation (5).
Umbilical hernias are very common in infants, occurring in 10% of infants, with a higher incidence in African American infants (20%) versus white infants (3%) and in premature infants occurring in up to 75% of infants <1,500 g (10). The majority of umbilical hernias in infants close spontaneously by 2 years of age, and rarely incarcerate or strangulate. “Strapping” is not an effective treatment. Surgery is generally not recommended unless the hernia becomes strangulated, persists to age 5 years, becomes progressively larger after 1 to 2 years of age, or is symptomatic (9).
CLINICAL PRESENTATION
The most common presenting complaints of a symptomatic hernia are swelling and pain. If there is an acute incarceration, there may be the sudden onset of severe pain with nausea and vomiting. The pain occurring with an acute incarcerated hernia is caused by edema and inflammation of the herniated structures and the surrounding tissues. Incarcerated hernias are the second most common cause of bowel obstruction in the United States, with postoperative adhesions being first. If strangulation is present, the patient may present with pain, distention, peritonitis, vomiting, fever, or sepsis.
Occasionally, the initial symptoms may be somewhat misleading. In some patients, the pain from an incarcerated groin hernia may be located in the epigastrium because of traction on the abdominal contents from the hernia. In other patients, strangulation can occur without any symptoms and signs of bowel obstruction when only part of the bowel wall is herniated. This occurs with a Richter hernia, in which only one side of the intestinal wall is within the hernia sac.
Pain and/or hypesthesia located along the medial aspect of the thigh radiating to the knee owing to irritation of the obturator nerve (Howship–Romberg sign) occurs in half of patients with an obturator hernia.
DIFFERENTIAL DIAGNOSIS
The most common diagnoses to consider in a patient presenting with a groin mass are an inguinal hernia, enlarged inguinal lymph node(s), abscess, hydrocele, and testicular pathology such as torsion of an undescended testicle in an infant (Table 110.2).
TABLE 110.2
Differential Diagnosis of Groin and Scrotal Masses
ED EVALUATION
History should include questions about previous operations or hernia. Also noteworthy is whether the patient has noted variability in the size of the hernia related to activity or lying flat. Physical examination should include inspection and gentle palpation for any bulges or masses. Cooperative patients may be asked to cough or strain, which increases intra-abdominal pressure, in an attempt to demonstrate the hernia. Palpation of the external inguinal ring in a standing male patient may also be helpful in detecting an inguinal hernia.
Laboratory tests are generally not helpful unless the patient has developed an incarcerated or strangulated hernia. In such cases, leukocytosis with a left shift may be present, although these findings are not sensitive or specific. Dehydration with electrolyte abnormalities and an elevated BUN also occurs frequently in patients with incarceration or strangulation.
Acute abdominal series radiographs may be helpful if bowel obstruction is suspected. The upright chest roentgenogram can rule out free air under the diaphragm resulting from perforation or dead bowel. Computed tomography scan and ultrasound are also useful in demonstrating a hernia and whether it contains bowel, when the diagnosis is in doubt, or an acute complication is suspected. One study reported 100% sensitivity and specificity for the diagnosis of groin hernia by bedside emergency ultrasound (16).
KEY TESTING
• History and physical examination alone are adequate in most cases.
• CT scan and ultrasound are useful in equivocal cases or to evaluate for complications.
ED MANAGEMENT
Patients with hernias can be grouped into three categories: (a) asymptomatic or minimal symptoms (swelling or mild discomfort) with a reducible hernia, (b) irreducible but not strangulated hernia, and (c) strangulated hernia.
Although surgery is indicated for the majority of patients with complications or significant symptoms related to their hernia, a recent clinical trial comparing routine surgical repair versus observation for asymptomatic patients with inguinal hernias concluded that “watchful waiting” is an acceptable option for men with minimally symptomatic inguinal hernias (17). Although used in the past, trusses are generally not recommended (18) and may actually be harmful in some cases (19). If the irreducible hernia is acute (and there is no evidence for strangulation), nonsurgical reduction should be performed. Cool compresses may be placed over the hernia site to diminish pain, edema, local blood flow, and decrease intraluminal gas pressure. Appropriate sedation should be given. If the patient has a groin hernia, he or she may be placed in the Trendelenburg position. The hernia may spontaneously reduce. If not, gentle manipulation (or taxis) may be attempted. Slow, steady compression should be used, not forceful attempts.
If the acute, incarcerated hernia cannot be reduced, emergency surgery should be performed as soon as fluid and electrolyte abnormalities are corrected. Complications of manual hernia reduction include partial reduction and hernia reduction en masse. Hernia reduction en masse is a rare complication in which the hernia sac is manipulated into the preperitoneal space. This gives the false impression that the hernia has been reduced although it is still incarcerated and at risk for strangulation.
The patient with a strangulated hernia requires aggressive resuscitation with fluids and blood as needed and emergent surgical consultation for operative intervention. Gastric decompression with a nasogastric tube is appropriate if bowel obstruction is present. Broad-spectrum antibiotics are also advised in the acutely ill or potentially septic patient.
CRITICAL INTERVENTIONS
• Reduction of an incarcerated hernia
• Aggressive resuscitation and early surgical consult for patients with a strangulated hernia
DISPOSITION
Patients with an asymptomatic or a reducible hernia should be given discharge instructions, which include the warning signs of incarceration and strangulation. They need referral to general surgery for evaluation for possible elective herniorrhaphy.
For patients with a hernia that has been reduced in the emergency department, urgent surgical referral for herniorrhaphy is recommended, as the incidence of recurrence is high.
Admission for surgical management is mandatory for acute, incarcerated hernias that cannot be reduced and for all strangulated hernias.
Common Pitfalls
• Failure to identify an incarcerated or strangulated hernia.
• Failure to diagnose a small hernia.
• Failure to make an appropriate referral to a surgeon.
• Failure to aggressively resuscitate a patient with a strangulated hernia.
REFERENCES
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