A hernia occurs when an internal organ or fatty tissue pushes through a weak spot in the surrounding muscle or connective tissue, creating a noticeable lump or bulge. While most people are familiar with common types like inguinal hernias, a less frequent defect is the flank hernia, also known as a lumbar hernia. This type of hernia forms in the posterolateral abdominal wall, the area on the side and back of the torso. Although rare, flank hernias require prompt medical attention because they can lead to serious complications if left unrepaired.
Understanding Flank Hernias: Location and Causes
Flank hernias develop in the region bordered by the 12th rib above and the hip bone, or iliac crest, below. The protrusion of abdominal contents occurs through a defect in the muscle and fascia layers. These protrusions are classified based on two distinct anatomical weak points: the superior lumbar triangle of Grynfeltt (the more common site) and the inferior lumbar triangle of Petit.
The causes of flank hernias are often categorized as acquired, meaning they develop over time due to external factors. Secondary flank hernias frequently occur after previous surgical procedures, such as spinal or kidney surgery, creating an incisional defect. Trauma from a hard injury or blunt force to the side of the abdomen is also a significant factor.
Other acquired hernias are primary or spontaneous, developing without a clear precipitating factor. Repetitive strenuous activity or underlying connective tissue disorders can contribute to muscle weakness. Congenital flank hernias are present from birth but account for only a small percentage. The majority of flank hernias are acquired and appear more often in men between the ages of 50 and 70.
Key Warning Signs and Symptoms
The most common sign of a flank hernia is a noticeable bulge in the side or lower back area, typically between the lower rib cage and the hip. This bulge becomes more pronounced when the person is standing, coughing, or straining, as these actions increase abdominal pressure. In the early stages, the bulge might be “reducible,” meaning it temporarily disappears when the person lies down or is gently pushed back into the abdomen.
Discomfort or pain is a frequent symptom, ranging from a dull, persistent ache to a sharp pain at the site of the protrusion. Patients often report a dragging or pulling sensation in the side. The pain usually worsens during movements like bending or lifting heavy objects. If the hernia involves the intestine, a person may also experience gastrointestinal issues such as nausea, vomiting, or constipation.
A change in the characteristics of the bulge is a serious warning sign. If the lump can no longer be pushed back inside and remains prominent even when lying down, it has become incarcerated. This indicates a risk that the trapped tissue could progress to a more hazardous state and requires immediate evaluation.
The Immediate Dangers and Risks
Flank hernias carry the risk of progressing to acute complications. The primary concern is incarceration, where the protruding tissue, such as a loop of intestine or fatty tissue, becomes tightly trapped within the muscle defect. Incarceration can lead to an obstruction, blocking the contents of the bowel and causing symptoms like severe abdominal pain, vomiting, and an inability to pass gas or have a bowel movement.
The most serious complication is strangulation, which occurs when the blood supply to the incarcerated tissue is completely cut off. Without oxygenated blood, the trapped tissue rapidly begins to die (necrosis). Strangulation is a medical emergency that can lead to gangrene, sepsis, and potentially fatal infection if not treated immediately.
Warning signs of a strangulated flank hernia include a sudden increase in pain at the hernia site that becomes unrelenting. Systemic symptoms include a high fever, a rapid heart rate, and severe nausea and vomiting. Locally, the skin over the bulge may change color, becoming red, purplish, or dusky, and the area will be extremely tender to the touch.
Diagnosis and Repair Methods
Evaluation of a suspected flank hernia begins with a physical examination to assess the location and characteristics of the bulge. Because flank hernias are located on the side and back, diagnosis can be difficult based on physical exam alone, especially in patients with a higher body mass index. Physicians rely on medical imaging to confirm the diagnosis, determine the exact size of the defect, and identify the contents of the hernia sac.
The computed tomography (CT) scan is the most reliable imaging method for diagnosis and planning surgical repair. Ultrasound and magnetic resonance imaging (MRI) may also be used for detailed visualization of the abdominal wall muscles and tissue. Once diagnosed, surgery is necessary because these defects rarely close on their own and carry the risk of incarceration and strangulation.
Surgical repair aims to return the protruding contents to the abdominal cavity and close the muscle defect, often using a prosthetic mesh to reinforce the weakened wall. The two main approaches are open repair, using a larger incision, and minimally invasive techniques like laparoscopic or robotic repair. Minimally invasive methods offer benefits such as smaller incisions and faster recovery times, but the choice depends on the size and complexity of the hernia.