A hernia occurs when an organ or fatty tissue pushes through a weak spot or opening in the muscle or connective tissue that is meant to contain it. While most people are familiar with common types like inguinal hernias in the groin, a flank hernia is a far rarer form of this condition. Also referred to as a lumbar hernia, it involves a defect in the posterolateral abdominal wall, which is the muscular boundary along the side and back of the torso. Due to its unusual location and complex anatomy, this type of hernia presents unique challenges in diagnosis and surgical repair.
Defining the Flank Hernia and Its Location
A flank hernia is defined by a protrusion of abdominal contents through a weakness in the side of the body, specifically in the lumbar region between the 12th rib and the top of the hip bone (iliac crest). This area, which forms the posterior abdominal wall, is inherently less protected by muscle layers than the front of the abdomen. The defects most commonly occur in two specific, naturally occurring weak points in the lumbar musculature, often described as triangles. The superior lumbar triangle (Grynfeltt-Lesshaft triangle) is a less common site, while the inferior lumbar triangle (Petit’s triangle) is a slightly more common location. Flank hernias account for only about two percent of all abdominal wall hernias.
Causes and Formation
The development of a flank hernia results from a breach in the fascial layers of the abdominal wall, which can occur either spontaneously or due to an acquired factor. Primary flank hernias are rare and develop without an identifiable external cause, often appearing in older individuals, most commonly men between the ages of 50 and 70. These spontaneous occurrences stem from an age-related weakening of the muscle and fascial structure in the lumbar region.
The majority of flank hernias, however, are secondary or acquired, resulting from an external event that compromises the integrity of the abdominal wall. The most common cause is previous surgical incisions, particularly those used for kidney procedures, spine surgery, or other operations that require a large incision in the side or back. Blunt force trauma to the abdomen or back, such as from a motor vehicle accident or a severe fall, can also cause a traumatic flank hernia by tearing the lateral abdominal wall muscles. Factors that increase pressure within the abdomen, like chronic coughing, obesity, or significant weight loss, can further contribute to the formation or enlargement of an existing defect.
Recognizing the Symptoms
The most common sign of a flank hernia is the presence of a soft, noticeable bulge or mass on the side or lower back that may become more prominent when the patient stands or strains. This protrusion often disappears or becomes smaller when the person lies down, a characteristic known as being reducible. Patients frequently report localized discomfort or a persistent dragging or pulling sensation in the area of the defect.
Pain in the flank or back is also a frequent symptom, and this discomfort often intensifies with physical exertion, coughing, or lifting heavy objects. Because the defect is near the spine and major nerves, some individuals may experience a vague or confusing pain pattern that is sometimes mistaken for a back problem. If the hernia involves a portion of the small or large bowel, the patient may also experience gastrointestinal symptoms, such as changes in bowel habits or a feeling of fullness.
A simple, reducible hernia becomes a more serious concern if it transitions into an incarcerated or strangulated state. Incarceration occurs when the tissue pushed through the defect becomes trapped and can no longer be pushed back inside, causing a sudden increase in pain and tenderness. The bulge will remain firm and irreducible. The most dangerous complication is strangulation, which happens when the blood supply to the trapped tissue is cut off, leading to tissue death (necrosis). Symptoms of a strangulated hernia are severe and require immediate emergency medical attention, including intense, unrelenting pain, fever, and signs of bowel obstruction such as nausea, vomiting, or an inability to pass gas or have a bowel movement.
Diagnosis and Repair Methods
Diagnosing a flank hernia typically begins with a thorough physical examination, as the physician can often feel the defect or the bulge, especially when the patient is asked to cough or strain. Due to the deep location of some lumbar hernias and the complexity of the surrounding musculature, imaging is frequently required to confirm the diagnosis and determine the precise size and contents of the hernia sac. A computed tomography (CT) scan is often the most effective imaging tool, as it provides clear, detailed cross-sectional images of the abdominal wall layers and can accurately visualize the defect. Ultrasound imaging can also be used to assess the hernia, particularly to see if the contents are moving or if there is any fluid accumulation.
Surgical intervention is the primary treatment for flank hernias because they have a low chance of resolving on their own and a high risk of developing complications like incarceration or strangulation. The goal of the procedure is to return the protruding contents to the abdominal cavity and close the defect to prevent recurrence. Surgical approaches generally fall into two categories: open repair and minimally invasive techniques.
Open repair involves a larger incision directly over the hernia site and is often preferred for larger, complex, or recurrent defects, as it allows for direct visualization and strong mesh fixation. Minimally invasive approaches, such as laparoscopic or robotic surgery, use smaller incisions and specialized instruments to perform the repair from the inside of the abdominal wall. Regardless of the technique used, mesh reinforcement is the standard of care, as it acts as a scaffold to strengthen the weakened area and significantly reduce the risk of the hernia returning.