Hernias: Clinical practice

A hernia is when an organ protrudes or bulges out through the body wall that normally contains it.

So an abdominal wall hernia is when an organ protrudes through the abdominal wall, which is made up of a few layers.

The deepest layer is the visceral peritoneum, which covers many of the abdominal organs, and lines the peritoneal space.

That layer wraps around to form the parietal peritoneum.

Then moving outwards, there’s the extraperitoneal fat, the transversalis fascia, the muscle layer with the internal and external oblique and transversus abdominis aponeurosis, and a layer of fascia, which has different names in different regions.

Anything that increases the pressure of the abdominal cavity may result in a sac that forms in the abdominal wall through which organs may protrude.

The organ that’s usually involved in a hernia is the gastrointestinal tract, but it can also involve other organs like the omentum, the bladder, and even the ovary.

Abdominal hernias vary in size and location.

Small hernias can be asymptomatic or they can cause pain and create a small bulge that can worsen with increased abdominal pressure from coughing or straining.

Over time, hernias can grow and lead to bowel obstruction, causing severe pain, nausea, vomiting, or constipation.

Larger hernias can put pressure on the overlying skin, causing erythema and ulceration.

Generally speaking, there are four types of abdominal wall hernias - groin, ventral, pelvic, and flank hernias.

The most common type are groin hernias, and they occur at the lower margin of the abdomen where the thigh meets the hip.

Groin hernias are classified into inguinal and femoral hernias, and inguinal hernias are further classified into direct inguinal and indirect inguinal hernias.

Direct inguinal protrude medial to the inferior epigastric vessels within Hesselbach's triangle, which is formed by the inguinal ligament inferiorly, the inferior epigastric vessels laterally, and the rectus abdominis muscle medially.

Whereas indirect inguinal hernias go through the inguinal ring, and protrude lateral to the epigastric vessels.

Femoral hernias are inferior to the inguinal ligament and protrude through the femoral ring.

Risk factors for groin hernias include a prior hernia; old age; chronically increased intra-abdominal pressure due to chronic cough, constipation, or strenuous exercise; abdominal wall injury; and smoking.

Most of the time, a groin hernia causes a dull sense of groin discomfort with straining or lifting, which is relieved once the pressure is removed.

Femoral hernias in particular can be an emergency if the bowel tissue gets trapped or incarcerated and the blood vessels get strangulated - leading to bowel ischemia.

Next, there’s ventral hernias, which occur in the anterior abdominal wall – and there are a few types.

First, there are epigastric hernias which are defects in the abdominal midline between the umbilicus and the xiphoid process. They’re due to a weakened linea alba, and most individuals have a small, slightly uncomfortable lump between the umbilicus and the xiphoid.

Second, there are umbilical hernias also called periumbilical hernia. This is a ventral hernia near the umbilicus, and it’s often associated with pregnancy. In males, umbilical hernias can often get incarcerated, whereas in females, the hernias are often easy to reduce.

Third, there are Spigelian hernias. These occur through a defect in the Spigelian aponeurosis, which is the aponeurosis of the transverse abdominal muscle bounded by the linea semilunaris laterally and the lateral edge of the rectus muscle medially. The typical location is in the "Spigelian hernia belt," a transverse 6 centimeter wide zone around the level of the arcuate line, which is the caudal-most extent of the posterior rectus sheath. Individuals usually have tenderness and swelling in the mid to lower abdomen, just lateral to the rectus muscle.

Fourth, there are incisional hernias which develop where a prior surgical incision was made and the fascia never fully healed. Since most abdominal incisions are made in the anterior abdominal wall, most incisional hernias are ventral hernias. Risk factors for poor healing include smoking, diabetes, old age, obesity, smoking, malnutrition, immunosuppressive therapy, and connective tissue disorders. Incisional hernias typically develop in the early postoperative period, but can sometimes occur even years after surgery.

Pelvic hernias protrude through one of the pelvic foramina – so obturator and sciatic hernias - or the pelvic floor – so perineal hernias.

Obturator hernias are rare, and they occur when there’s protrusion of the abdominal organs through the obturator foramen, which is on the anterolateral aspect of the pelvic wall, where the obturator nerve, artery, and vein traverse.

Weakness of the obturator membrane can cause enlargement of the obturator canal with a defect that is usually anterior and medial to the obturator neurovascular bundle.

Preperitoneal fat and lymphatic tissue in the obturator canal normally form a cushion around the neurovascular bundle that prevents herniation. Thus, obturator hernia usually occurs in the setting of profound weight loss.

An obturator hernia can cause obturator neuralgia, which is groin pain that radiates medially to the knee due to compression of the obturator nerve.

An obturator hernia can also cause a proximal thigh mass to form between the pectineus and adductor longus muscles, or ecchymosis of the thigh if bowel necrosis has occurred.

Next, are sciatic hernias which occur when abdominal contents protrude through the greater or lesser sciatic foramen.

The risk for a sciatic hernia increases in individuals that have had pelvic surgery. These unusual hernias can cause a buttock mass, abdominal pain, or sciatica symptoms.

Finally, perineal hernias are the protrusion of organs into the perineum through a defect in the pelvic floor.

Perineal hernias typically occur in older multiparous females, or occur as incisional hernias in individuals with extensive pelvic operations.

Perineal hernias cause a unilateral bulge in the area of the labia, perineal regions, or gluteal regions.