An internal hernia occurs when a section of an organ, typically part of the small intestine, pushes through an opening or defect located entirely within the abdominal cavity. Unlike common external hernias, which create a visible bulge through the abdominal wall, an internal hernia remains hidden inside the body. The lack of an external lump often makes the condition challenging to diagnose initially. Despite being contained within the abdomen, the trapped bowel can lead to severe, life-threatening complications requiring immediate medical attention.
Defining Internal Hernias and Their Origin
An internal hernia involves the protrusion of abdominal contents through an aperture within the peritoneal cavity. These defects are most frequently acquired due to prior abdominal surgery, though they can be naturally occurring. The most common modern cause is an operation that rearranges the small intestine, such as a Roux-en-Y Gastric Bypass (RYGB).
This bariatric procedure creates new spaces and defects in the mesentery, the tissue anchoring the small intestine to the back of the abdominal wall. The small intestine can prolapse through these defects, becoming trapped.
The two primary sites for internal hernia formation following RYGB are Petersen’s defect and the jejunojejunal mesenteric defect. The incidence of internal hernias is higher following laparoscopic RYGB than the open technique because the minimally invasive approach results in fewer protective adhesions forming within the abdomen.
Recognizing the Signs
The symptoms of an internal hernia are variable and often non-specific, contributing to the difficulty in diagnosis. The most noticeable symptom is typically the sudden onset of severe, cramping abdominal pain. This pain is frequently intermittent, meaning it comes and goes as the loop of bowel may spontaneously reduce or become trapped.
When the bowel becomes trapped and obstructed, the pain becomes constant and intense. Associated symptoms like nausea, vomiting, and abdominal distention are common as the flow of digestive contents is blocked.
Patients who have had bariatric surgery and experience unexplained abdominal pain should have a high suspicion for this condition. The absence of a visible external bulge means that any digestive symptoms require careful investigation.
Diagnosis and Need for Intervention
Confirming the presence of an internal hernia typically relies on medical imaging, as a physical exam often yields non-specific findings. A computed tomography (CT) scan is the standard diagnostic tool for visualizing the abdominal anatomy and detecting these internal defects. The CT scan can identify signs of a cluster of small bowel loops in an abnormal location or a radial array of distended loops converging toward the hernia orifice.
The immediate danger is the risk of a closed-loop small bowel obstruction, which can lead to strangulation. Strangulation occurs when the blood supply to the trapped section of the bowel is cut off. Loss of blood flow (ischemia) results in the death of the intestinal tissue, potentially leading to perforation and sepsis.
Because of the high risk of strangulation, an internal hernia is considered a surgical emergency once confirmed or highly suspected. Ischemia can develop rapidly, and the potential for a mortality rate exceeding 50% with strangulation underscores the need for immediate intervention. A CT scan with intravenous contrast is often used to assess bowel wall enhancement, indicating whether the tissue is still receiving blood supply.
Repair and Recovery
The definitive treatment for an internal hernia is surgical repair, which aims to reduce the herniated segment of bowel and permanently close the anatomical defect. This procedure is most often performed using a laparoscopic approach, utilizing small incisions and specialized instruments. Laparoscopic surgery allows for a faster recovery compared to traditional open surgery.
During the operation, the surgeon gently pulls the trapped loop of small intestine back into the abdominal cavity. The next step is to close the defect using sutures to prevent future herniation. This repair addresses the underlying cause and reduces the risk of recurrence.
Following laparoscopic repair, patients typically have a short hospital stay, often being discharged within a day or two. Most individuals return to light activities within one to two weeks. Strenuous activities or heavy lifting must be avoided for approximately four to six weeks until a full return to normal physical activity is expected.