Spigelian HerniaEdit
Spigelian hernia is a rare form of ventral hernia that protrudes through defects in the Spigelian fascia, a layer of the abdominal wall found along the semilunar line. These defects occur in the vertical fascial plane between the rectus abdominis medially and the oblique and transversus muscles laterally, most often in the lower abdomen just lateral to the rectus muscle. Although any person can develop one, it is more commonly detected in middle-aged adults and is known for being difficult to diagnose on physical examination because the hernia sac can lie between muscle layers rather than presenting as a conspicuous lump at the surface. The condition is typically a surgical concern because the content—often omentum or small bowel—can become incarcerated or strangulated if the opening narrows.
Because the physical exam can be unrevealing, imaging plays a central role in confirming the diagnosis. Ultrasound and Computed tomography are commonly used, with CT offering detailed visualization of the fascial defect and the surrounding anatomy. Clinicians consider Spigelian hernias in patients with localized abdominal pain or a subtle abdominal wall mass, particularly when initial assessments for more common ventral hernias are inconclusive.
Anatomy and pathophysiology
The Spigelian fascia forms the aponeurotic layer of the abdominal wall along the semilunar line where the rectus abdominis transitions to the lateral oblique and transverse muscles. Spigelian hernias occur through defects in this fascia, most often just lateral to the rectus muscle. The location corresponds to the so-called Spigelian belt, a relatively narrow zone where the fascial layers are more prone to weakness. The resultant hernia sac can lie between layers of the abdominal wall, which contributes to a tendency for delayed or missed clinical recognition.
- Key anatomical terms: Spigelian fascia, semilunar line, rectus abdominis, transversus abdominis, external oblique.
- Typical contents: omentum and segments of the small intestine are commonly involved, but other intra-abdominal contents can herniate.
- Pathophysiology: weakness or defects in the Spigelian fascia allow abdominal contents to protrude; repeated increases in intra-abdominal pressure (such as coughing or heavy lifting) can promote expansion of a small defect over time.
Clinical presentation and diagnosis
Spigelian hernias often present as localized, intermittent abdominal pain that may be worsened by activity or Valsalva maneuvers. A palpable lump may be absent or difficult to detect because the hernia sac remains interparietal (between muscle layers). When present, a mass may change in size or become more prominent with strain. Because of the risk of incarceration, a high index of suspicion is important in patients with persistent focal abdominal pain and a negative exam for more common hernias.
- Diagnostic tools: ultrasound and computed tomography are the mainstays of evaluation. Ultrasound is a convenient initial test, while CT provides detailed mapping of the fascial defect and its relation to surrounding muscles and intra-abdominal contents.
- Differential diagnosis includes other forms of ventral hernias, abdominal wall hernias at different sites, and non-hernia causes of localized abdominal pain.
Treatment and prognosis
Surgical repair is the standard of care for most Spigelian hernias, given the propensity for incarceration and strangulation. The goal is to close the fascial defect and reinforce the abdominal wall, frequently with mesh to reduce recurrence risk.
- Open repair: A conventional approach that directly addresses the defect through an incision in the abdominal wall; mesh reinforcement is commonly used.
- Laparoscopic repair: Techniques such as transabdominal preperitoneal (TAP) or totally extraperitoneal (TEP) approaches offer the advantages of smaller incisions and potentially faster recovery.
- Mesh and fixation: Synthetic mesh is frequently employed to reinforce the repair and reduce recurrence. The choice of mesh type and fixation method may depend on operative technique and patient factors.
- Postoperative considerations: Recovery varies with the surgical approach, but most patients improve with standard postoperative care. Early recognition and treatment of incarceration or strangulation are critical to outcomes.
Epidemiology and history
Spigelian hernias are rare among abdominal wall hernias, comprising a small fraction of ventral hernias. They are most often identified in adults, with a slight predilection for those in midlife to older age groups. The condition bears the eponym associated with the Spigelian fascia and the anatomical region around the semilunar line, and its recognition has evolved with advances in imaging that clarify its sometimes subtle clinical presentation.