Epidemiology

Herniorrhaphy (also known as hernioplasty, or surgical repair of a hernia) is a common procedure in the United States. Approximately 800,000 inguinal hernia repairs were performed in the United States in 2003; mesh was used in 90% of the cases.¹

Of groin hernias, inguinal hernias (96%) are much more common than femoral hernias (4%). The male-to-female ratio for inguinal hernias is 9 : 1, and that for femoral hernias is 1 : 4. In elderly women, femoral hernias are as common as inguinal hernias. The incidence of strangulation increases with advancing age.

Operative mortality for a strangulated hernia is 5% to 10% in patients older than 80 years, as compared with 3% for elective repair in that age group. Mortality increases to 19% when bowel necrosis is present.

The incidence of postoperative intraabdominal hernias is increasing because of the higher number of Roux-en-Y gastric bypass procedures performed each year; postoperative hernias are observed in 2.5% to 4.5% of patients undergoing bariatric surgery.

Incisional hernias of the abdominal wall occur in up to 11% of all other postoperative patients and in as many as 23% of patients with postoperative wound infections. Trocar site hernias after laparoscopic surgery are reported in up to 6% of patients. Parastomal hernia formation occurs in 28% of ileostomies and 48% of colostomies. Morbidity depends on the location and contents of the hernia, as well as the development of incarceration or strangulation.

Pathophysiology

Hernias are congenital or acquired defects in the abdominal wall that allow protrusion of intraabdominal contents through the pathologic opening. The characteristic finding consists of pain and swelling at the hernia site. Intraabdominal hernias, which can occur spontaneously or after surgery or trauma, are caused by defects in the diaphragm, mesentery, or ligamentous structures.

Incarcerated hernias are those in which abdominal contents have become trapped in the opening (i.e., nonreducible). Bowel incarceration can be manifested as pain, vomiting, or frank obstruction.

Strangulated hernias involve a compromise of the blood supply to the hernia contents. Strangulation can be manifested as fever, ischemia, or necrosis of the hernia contents and, occasionally, erythema or necrosis of the skin overlying the hernia. Smaller defects in the abdominal wall are more likely to be manifested as incarceration or strangulation.

Reduction—replacement of the hernia contents back into the abdominal cavity—is the immediate treatment of a hernia. Reduction of a hernia is accomplished by gentle pressure over the area of herniation. Reduction is assisted by use of the supine or Trendelenburg position, application of ice, analgesia, and procedural sedation to relax the musculature of the abdominal wall. Reduction should not be attempted if necrosis of the hernia contents is suspected. Definitive hernia treatment is surgical repair.

Nomenclature

Table 38.1 and Box 38.1 summarize the nomenclature of hernias, and Figures 38.1 to 38.13 illustrate some of the hernia types.

Table 38.1 Nomenclature of Hernias

Groin Hernias
Inguinal hernia (Fig. 38.1)	Physical examination cannot accurately distinguish between indirect and direct inguinal hernias
Indirect	Occurs through the inguinal canal
	Inguinal canal contents include the ilioinguinal nerve, genital branch of the genitofemoral nerve, spermatic cord in men (vas deferens, testicular artery, and vein), and round ligament in women
Direct	65% of inguinal hernias are indirect
	Weakness of the aponeurosis of the transversus abdominis and transversalis fascia in the Hesselbach triangle (the medial border of which is the lateral aspect of the rectus abdominis, the superior border is the epigastric artery, and the inferior border is the inguinal ligament)
Femoral hernia	Occurs through the femoral canal, inferior to the inguinal ligament, medial to the femoral vein
	More common in elderly, parous women
Sportsman’s hernia	Syndrome of persistent groin pain in athletes; probably caused by recurrent or persistent groin strain, osteitis pubis, or a nonpalpable hernia
	More common in kicking sports
Abdominal Wall Hernias
Anterior (Fig. 38.2)
Epigastric hernia	Occurs through the linea alba, the midline between the xiphoid line and umbilicus
Umbilical hernia	Caused by an abnormally large or weak umbilical ring
	Umbilical hernia usually closes spontaneously in infancy but does not heal in adulthood
	Rarely incarcerates in children
	Worsened by pregnancy, obesity, or cirrhosis with ascites
Spigelian hernia (Figs. 38.3 and 38.4)	Lateral ventral hernia through the spigelian zone: transversalis fascia between the lateral margin of the rectus abdominis muscle, medial margins of the external and internal obliques, and the transversus abdominis muscles
	Accounts for 1-2% of all hernias
Ventral or incisional hernia (Fig. 38.5)	Trocar sites: Difficult to recognize on physical examination Dangerous cause of early postoperative small bowel obstruction Can be the Richter type (incarceration of one intestinal wall) Iliac crest bone graft sites Parastomal hernias

 Traumatic Caused by blunt or penetrating trauma “Handlebar” hernia:

 Congenital abdominal wall defects Surgical emergencies in neonates:

Types:

Posterior (lumbar) hernias (Fig. 38.6) Bounded superiorly by the 12th rib, inferiorly by the iliac crest, posteriorly by the erector spinae muscles, and anteriorly by the posterior border of the external oblique muscle Types:

Diaphragmatic Hernias Congenital hernia (Fig. 38.7) Eventration: thin diaphragm with normal but widely spaced muscle fibers Posterolateral: through the foramen of Bochdalek Anterior, retrosternal, or parasternal: through the foramen of Morgagni (Figs. 38.8 and 38.9) Peritoneopericardial Acquired hernia Hiatal: sliding or fixed Paraesophageal Acquired eventration: caused by phrenic nerve injury and paralysis Traumatic (Fig. 38.10) Pelvic Wall and Floor Hernias Sciatic hernia (Fig. 38.11) Protrusion of the peritoneal sac and contents through the greater or lesser sciatic foramen Obturator hernia (Fig. 38.12) Protrusion of preperitoneal fat or intestine through the obturator foramen Perineal hernia Protrusion of a viscus through the pelvic floor (rare) Prolapse Weakness of the pelvic floor muscles can cause a cystocele, rectocele, and uterine or rectal prolapse Intraabdominal Hernias Spontaneous    Transmesenteric hernia Through the sigmoid mesocolon, broad ligament, or falciform ligament  Transomental hernia Hernia beneath a mesenteric or peritoneal fold (no disruption of the peritoneum) Locations:

Postoperative Transmesenteric and transomental hernias are most common, especially after Roux-en-Y procedures May occur through the falciform ligament from a trocar puncture during laparoscopic cholecystectomy Retroanastomotic—may occur behind the anastomosis

Pathophysiology

In comparison with controls, patients in whom incisional or recurrent hernias develop may exhibit abnormal synthesis of type I and type III collagen.² A higher incidence of incisional hernia formation is seen in patients with wound infection, obesity, and multiple comorbid conditions. The use of synthetic mesh and “tension-free” repair techniques has reduced rates of hernia recurrence.

Presenting Signs and Symptoms

The classic manifestation of an abdominal wall hernia is pain and swelling at the hernia site. Symptoms are more pronounced with increased intraabdominal pressure, such as occurs with standing, coughing, and straining. Occasionally, patients report an acute onset of symptoms after heavy lifting or during sports. Many patients observe that the swelling (“lump” or “knot”) resolves when they are supine or pressure is applied over the area.

Inguinal hernias can be manifested as scrotal pain, a groin mass, or swelling. Incarcerated hernias typically feature a painful lump or knot on the abdominal wall or in the scrotum. The hernia is very tender to palpation and is not reduced by gentle pressure. If small bowel is incarcerated in the hernia sac, the patient may exhibit nausea and vomiting. Incarcerated omentum or preperitoneal fat may give rise to only a localized painful mass.

As the incarceration persists over time, swelling of the hernia contents eventually compromises the blood supply and strangulation ensues. The signs and symptoms vary with the contents of the hernia. Patients with incarcerated intestine leading to intestinal ischemia or necrosis may have fever and peritonitis. Prolonged incarceration with necrosis of the hernia contents may cause erythema or necrosis of the skin overlying the hernia.

Long-standing hernias may feature very large defects in the abdominal wall. In general, larger defects are less likely to be manifested as strangulation. A large hernia may be chronically incarcerated or nonreducible. With time, fibrous adhesions develop and prevent spontaneous reduction when the patient is supine.

Less typical findings include ill-defined abdominal pain, nausea, and vomiting but without an obvious mass on the abdominal wall. This manifestation is more likely to occur with intraabdominal hernias, in obese patients, or in patients who are unable to give an adequate history.

The incidence of postoperative internal hernias is rising because of the increase in bariatric operations in the United States, particularly Roux-en-Y gastric bypass.³ Postoperative complications of hernia repair include wound infection, seroma or hematoma, ileus or small bowel obstruction, recurrence of the hernia, and in rare cases, erosion of preperitoneal mesh into intraabdominal organs with associated fistula formation.⁴ Complications of inguinal hernia repair are chronic pain as a result of nerve disruption or entrapment and, rarely, testicular ischemia.

Traumatic diaphragmatic disruption from penetrating trauma should be suspected when the trajectory of a gunshot wound or the location of a stab wound potentially crosses the diaphragm. Though rare, diaphragmatic disruption can occur after significant blunt trauma and is more common on the left side. Traumatic diaphragmatic disruption is difficult to diagnose in the acute stage because of nonspecific signs, but it should be suspected when the patient has a proximate injury and pain out of proportion to the physical findings. Standard imaging techniques, including chest and abdominal computed tomography (CT), may miss small diaphragmatic injuries, and laparoscopy, thoracoscopy, or surgical exploration may be required.

Diaphragmatic disruption has also been described after forceful coughing or vomiting. Delayed manifestations of diaphragmatic hernias consist of chest pain, dyspnea, or abnormal findings on chest radiography or CT (with or without abdominal symptoms). The use of multidetector CT scanning has improved the detection of diaphragmatic hernias.

Differential Diagnosis and Medical Decision Making

The differential diagnosis of abdominal wall hernias includes other masses involving the abdominal wall, such as lipomas and rectus sheath hematomas. Abdominal wall or intraabdominal hernias should be considered a potential cause in patients with signs and symptoms of small bowel obstruction. In patients who have previously undergone abdominal surgery, either open or laparoscopic, careful examination of the incisions,⁵ trocar sites,⁶ and parastomal areas⁷ should be performed to detect masses or abdominal wall defects. To facilitate detection of the hernia, the examiner should hold the tips of the fingers over the incision while the patient coughs or strains.⁸

Inguinal hernias should be considered in the evaluation of patients with scrotal pain or swelling. Detection of inguinal hernias is improved by examination of the patient in a standing position and insertion of the examiner’s finger into the inguinal canal through the loose skin of the scrotum. This technique allows direct palpation of the inguinal ring. Having the patient cough or strain allows the examiner to palpate the hernia bulging against the examining finger. Other causes of scrotal pain, masses, or swelling are testicular torsion, tumor, orchitis, epididymitis, lipoma, hydrocele, and varicocele.⁹

Congenital anatomic fistulas of the urachus or omphalomesenteric duct can be manifested in children or adults as umbilical pain, swelling, a mass, erythema, or discharge and can be confused with an umbilical hernia.

Obturator or other rare pelvic floor hernias should be considered in the differential diagnosis of patients with chronic atypical pelvic pain; CT should be performed.

In the majority of cases, physical examination alone enables the identification of abdominal wall or inguinal hernias. When physical examination is not sufficient, ultrasonography, CT, and occasionally magnetic resonance imaging can assist in the identification of hernias and serve to further delineate their contents.

Ultrasonography is the imaging modality of choice in the evaluation of scrotal swelling or masses because it allows differentiation of the testicles, spermatic cord, hydrocele, or varicocele separately from the hernia contents. This modality can assist in the diagnosis of abdominal wall hernias through identification of bowel loops within the hernia sac. Color flow Doppler imaging can detect the presence or absence of blood flow in some cases, thereby aiding in the diagnosis of strangulation.¹⁰

CT can be used to identify intraabdominal and abdominal wall hernias (as well as delineate the contents of the hernia sac) and signs of ischemia, perforation, or abscess formation. Plain abdominal films have limited utility in the diagnosis and evaluation of hernias. Laparoscopy may be necessary to assist in the diagnosis of difficult cases when the findings of other modalities are unrevealing.

Pediatric Considerations

Omphalocele occurs in 2 to 3 per 10,000 births. Historically, gastroschisis occurred less frequently than omphalocele, but recent trends show an increase in the incidence of gastroschisis worldwide (and in the United States). Gastroschisis occurs more commonly with younger maternal age and is associated with fewer congenital anomalies than omphalocele is. Ultrasonography has led to more frequent prenatal diagnosis, but cesarean delivery has not been shown to improve outcomes over vaginal delivery in infants with abdominal wall defects.

Congenital diaphragmatic hernias occur in 1 in 2500 births. The mortality rate is high because of pulmonary hypoplasia and the development of pulmonary hypertension. Ultrasonography allows prenatal diagnosis and identification of infants with the potential for a poor prognosis. The prognosis worsens when the liver is located intrathoracically and total lung volume is less than total head volume. In utero repair of diaphragmatic hernias has been performed, although better outcomes than those with conventional treatment have not been observed.¹¹

Percutaneous placement of a fetal endoluminal tracheal occlusion balloon may improve survival by preventing egress of the pulmonary fluid needed to stimulate lung growth.¹² This treatment is still controversial because of a higher incidence of preterm labor. Stabilization of infants with congenital diaphragmatic hernia consists of intravenous fluid resuscitation, insertion of a nasogastric tube, intubation with gentle ventilation or permissive hypercapnia (to avoid barotrauma), and surgical consultation. The use of nitric oxide and surfactant has not been demonstrated to improve outcomes in infants with congenital diaphragmatic hernias.

Late manifestations of congenital diaphragmatic hernia have been described in children and adults. Cases typically involve respiratory difficulty, and tension gastrothorax has also been reported. Unrecognized diaphragmatic hernias can be exacerbated by pregnancy and be manifested as incarceration and bowel obstruction, in addition to respiratory distress.

Indirect inguinal and umbilical hernias are extremely common in children—parents may bring an infant or child to the emergency department when the lump or bulge is first noted. Incarceration or strangulation is uncommon but can occur. The clinical findings in children are similar to those in adults. Physical examination of the scrotum and groin is mandatory in the evaluation of crying or vomiting infants. Ultrasonography is used more often than CT for the evaluation of hernias in children.

Treatment

Follow-Up, Next Steps in Care, and Patient Education

Hernias with signs or symptoms suggestive of bowel obstruction or ischemia are true surgical emergencies that require immediate consultation.

Emergency repair of incarcerated or strangulated hernias is associated with higher morbidity and mortality than is the case with elective repair, especially in elderly patients or those with multiple medical comorbid conditions.¹⁹ Complications include a higher incidence of bowel ischemia and necrosis, wound infection and dehiscence, intraabdominal compartment syndrome, sepsis and respiratory compromise, and hernia recurrence.²⁰

Patients with easily reducible hernias may be discharged for surgical follow-up and elective hernia repair. Repair is generally recommended for symptomatic hernias in otherwise healthy patients. Patients who have multiple medical problems and for whom surgery poses a high risk may not be suitable candidates for elective hernia repair, especially when the fascial defect is large and less likely to become incarcerated. The decision about the timing of hernia repair should be made by the patient in conjunction with the primary care physician and the surgeon. Elective repair of symptomatic hernias in elderly patients should be considered.²¹

Unrepaired hernias may gradually enlarge over time, and some become incarcerated. Patients with incarcerated hernias that cannot be reduced should be admitted for urgent surgical reduction and repair because some hernias progress to ischemia of the hernia contents.