What is a Hernia Defect?
A hernia defect is an abnormal opening, weakness, or discontinuity in the muscle, fascia, or diaphragm that allows abdominal organs or tissues to protrude through it into an adjacent space. 1
Anatomic Definition
The hernia defect represents the actual hole or gap in the structural barrier, distinct from the hernia itself (which includes both the defect and the protruding contents). 1, 2
Key structural characteristics include:
Location and size - The defect can occur in the abdominal wall (external hernias), within the peritoneum or mesentery (internal hernias), or in the diaphragm (diaphragmatic hernias). 2
Tissue loss - The defect represents a loss of tissue structure and function at the load-bearing muscle, tendon, and fascial layer, resulting from either primary fascial pathology or surgical wound failure. 3
Congenital vs. acquired - Defects may be present from birth due to incomplete development (such as incomplete diaphragm formation during the eighth week of gestation) or acquired through trauma, surgery, or progressive tissue weakness. 1, 4
Clinical Significance of Defect Size
The size of the hernia defect directly determines treatment approach and risk of complications:
Small defects (< 3 cm) can typically be closed with primary suture repair using interrupted non-absorbable 2-0 or 1-0 monofilament or braided sutures in two layers. 1
Large defects (> 3 cm) cannot be closed with direct suture without excessive tension due to considerable tissue loss, requiring mesh reinforcement to prevent the 42% recurrence rate associated with primary repair alone. 1
Narrow, rigid defects (such as the femoral ring) carry the highest risk of strangulation because herniated contents become trapped and compressed. 5
Radiologic Identification
CT scan is the gold standard for identifying and characterizing hernia defects, with sensitivity of 14-82% and specificity of 87%. 1
Critical CT findings that identify the defect include:
Diaphragmatic discontinuity - Direct visualization of the gap in the diaphragm. 1
"Dangling diaphragm" sign - The free edge of the ruptured diaphragm curling toward the center of the abdomen away from the chest wall. 1
"Collar sign" - Constriction of the herniating organ at the level of the defect, indicating the exact location and size of the opening. 1
Segmental non-recognition - Areas where the normal anatomic barrier cannot be visualized due to the defect. 1
Biological Basis
Hernia defects result from cellular and extracellular molecular matrix abnormalities: