Strangulated Hernia

Etiology

There are several causes of hernias. A hernia can be caused by congenital predispositions or acquired from the weakening of the abdominal wall secondary to an incision or trauma. Umbilical and inguinal hernias are often present at birth and can enlarge over time. Incisional hernias can form from an iatrogenic weakness of the abdominal wall from previous surgeries. These can develop at any incision, including trocar sites over 5 mm from laparoscopic surgery.[1] Patient factors can influence hernia formation. Patients with collagen vascular disease and connective tissue disorders (Marfan syndrome, Ehlers-Danlos) have weak tissue strength and are at increased risk for hernia formation.[2] Hernias form in patients with increased abdominal pressure, including pregnancy, straining due to constipation, chronic obstructive pulmonary disease (COPD), or chronic cough.[3] It is controversial whether people who engage in heavy lifting regularly are at increased risk of hernia formation.[4][5]

Epidemiology

Hernias are common, and it is estimated that 5% of individuals develop an abdominal wall hernia over their lifetime. Inguinal hernias are approximately 7 times more prevalent in men than women. The most common type of groin hernia in men and women is an indirect inguinal hernia.[6] Although inguinal hernias are also most common in women, femoral and umbilical hernias occur more frequently in women than in men. Groin hernias occur more commonly on the right side due to the embryologic delayed or failed closure of the processus vaginalis. Femoral hernias are also more common on the right side, possibly due to a lack of sigmoid colon covering the femoral canal. Hernias increase with age and strain on the abdominal wall over time. The risk of a hernia becoming incarcerated or strangulated is estimated between 1% to 3% over a person’s lifetime.[7] Femoral hernias can become incarcerated up to 30% of the time and should always be repaired surgically when found.[8]

Pathophysiology

The anatomy of the abdominal wall is very important when evaluating a patient for a hernia. Several layers of adipose tissue, fascia, and musculature form the abdominal wall. In the midline, the rectus abdominis muscle runs longitudinally from the pubic symphysis to the sternum and ribs. Laterally, 3 layers of muscle run in oblique patterns to prevent abdominal wall herniation. The external oblique, internal oblique, and transversus abdominus coalesce to form fascial sheaths surrounding the rectus abdominis.

There are weak points in the abdominal wall where the muscle and fascial layers are attenuated. In the inguinal canal, several anatomic boundaries help delineate the type of hernia. Hasselbach’s triangle is bounded by the rectus abdominis medially, the inguinal canal inferior laterally, and the inferior epigastric vessels superiorly. Direct inguinal hernias occur within this triangle. Hernias that occur lateral to the inferior epigastric vessels and along the inguinal ring are indirect inguinal hernias. There is a weakness here due to the thinning of the external and internal oblique to form an aponeurosis. This weakness leaves the transversalis fascia and peritoneum without additional muscular support. Femoral hernias occur inferior to the inguinal canal within the femoral space and medial to the femoral vessels.[9]

History and Physical

A history of trauma, heavy lifting, or chronic bulge may be elicited from the patient. The patient usually describes a bulge and pain, which is worse when lifting or straining. When strangulation exists, the patient may present with bowel obstruction symptoms, including nausea, vomiting, and obstipation. If bowel ischemia is present, the patient has severe pain and may present with sepsis (hypotension, tachycardia). Before palpating the abdominal wall, it is important to visually inspect the skin overlying the hernia. Any appearance of erythematous or dusky skin is a concern for a possible strangulated hernia. An emergent surgical consult should be obtained if skin changes are noted before attempting to reduce the hernia. When evaluating a patient for a hernia, asking the patient to increase abdominal pressure via a Valsalva maneuver is essential.

The patient should be evaluated in both the sitting and standing position. Palpate the abdominal wall area to evaluate for a hernia during Valsalva, and a bulge or weakening of the abdominal musculature should be appreciated. When evaluating for inguinal hernias in males while standing, invaginate the scrotum and place a finger within the external inguinal ring to palpate for a bulge. There should be a push against your finger when the patient is performing a Valsalva maneuver. Large hernias in the groin area may appear as a mass in the femoral area near the vessels or a scrotal mass. Acutely incarcerated hernias appear erythematous, indurated, swollen, and painful to palpation. When there is a bowel within the hernia defect, you may feel peristalsis of fluid in the hernia sac. If bowel strangulation is present, the patient may have focal or generalized peritonitis on examination.

Evaluation

The majority of hernias can be diagnosed with physical examination alone. In patients who have an exam that causes concern for a strangulated hernia, it is important to rule out bowel ischemia. A complete blood count and a basic metabolic panel should be checked for leukocytosis and abnormalities. A lactate level can be helpful, although, with acute strangulated small bowel, this level may be falsely normal for up to 8 hours while the blood supply is compromised.[10] Ultrasound is the best initial test in determining whether a hernia is present, especially if there are concerns about the testicular etiology of the patient’s pain. A CT of the abdomen and pelvis can help delineate anatomy and determine if the bowel is strangulated within the hernia. MRI is a more sensitive test than a CT scan in diagnosing occult hernias. It can determine if associated musculoskeletal injuries are noted, but it is not as useful in the acute setting. Another useful technique to diagnose occult hernias is diagnostic laparoscopy, although this is not usually necessary.[11][12][13]

Treatment / Management

Patients with non-incarcerated hernias may be offered elective surgical repair based on their symptomatology. For patients with moderate to severe symptoms who are healthy enough to undergo surgery, surgical repair is indicated.[14] For an older patient with multiple comorbidities and a relatively asymptomatic hernia, a watchful waiting approach may be warranted due to the low risk of strangulation.[15] For an acutely incarcerated hernia without a bowel present, manual reduction can be attempted. Sedation may be necessary if this area is particularly painful for the patient. The patient should be supine, and Trendelenburg may help reduce incarcerated groin hernias. Gentle pressure on the hernia itself from all sides helps the hernia reduce intra-abdominally. Ice helps reduce acute inflammation of the hernia sac. An acutely incarcerated hernia with concern for strangulation is an indication of emergent surgery. Femoral hernias have a higher risk for incarceration and should be repaired soon after diagnosis to avoid future complications. When a strangulated hernia is suspected, an emergent surgical consultation should be obtained. If bowel obstruction is present, consider placing a nasogastric tube for decompression and ensure the patient has appropriate fluid resuscitation. If there is suspicion of bowel necrosis or perforation, broad-spectrum antibiotics should be started.[16](A1)

Surgical repair of the strangulated hernia depends on the operative skill and choice of the surgeon. Studies have shown success with a laparoscopic or robotic technique to evaluate strangulated bowel. Depending on the surgeon's skill and experience, bowel resection may also be performed using a minimally invasive technique. For surgeons not experienced in laparoscopic approaches, open approaches are equally successful.[17][18][19] The bowel must be adequately visualized and evaluated to determine viability before closing the defect. Studies have shown the safe placement of synthetic mesh in the acute setting. Still, most surgeons would avoid placing synthetic mesh to reduce the risk of seeding the mesh with bacteria, especially when a bowel resection is performed. For incarcerated hernias without bowel strangulation, synthetic mesh placement has been proven to be safe and best practice to prevent recurrent hernia formation.[20][21][22] Closing the hernia defect primarily with a tissue technique or placement of a non-synthetic (biologic acellular dermal matrix) are additional options well described in the acute setting.[23](A1)

Differential Diagnosis

Groin mass: lymphadenopathy, abscess, undescended testicle, vascular aneurysm, lipoma

Scrotal mass: hydrocele, testicular tumor, varicocele, testicular torsion

Groin pain: musculoskeletal injury, athletic pubalgia (sports hernia), epididymitis

• Abscess
• Athletica pubalgia
• Epididymitis
• Hydrocele
• Lipoma
• Lymphadenopathy
• Musculoskeletal injury
• Testicular torsion
• Testicular tumor
• Varicocele
• Vascular aneurysm
• Undescended testicle

Prognosis

Overall mortality and prognosis are influenced by whether the surgery was emergent or elective. For elective surgical repair of a groin hernia, the risk of mortality is low at 0.1%. Mortality is increased to up to 3% with emergency surgery for strangulated bowel, notably when bowel resection is performed.[24]

Complications

Complications are more common in emergent surgeries and in patients who have had previous abdominal surgeries or hernia repairs. Large hernias can distort the normal anatomy and increase the risk of injury to intra-abdominal structures. Complications related to hernia surgery are more common in patients undergoing emergent surgery with multiple co-morbidities and increased age.[24]

• Surgical site infection
• Hematoma
• Wound dehiscence
• Chronic pain
• Anastomotic leak (when bowel resected)
• Bowel necrosis
• Testicular necrosis
• Nerve injury
• Vascular injury