What are the clinical presentation and management of a Spigelian hernia in a patient with acute abdominal pain and a palpable mass in the abdominal wall?

Clinical Presentation of Spigelian Hernia

Spigelian hernia typically presents with localized abdominal pain and a palpable mass along the semilunar line, though diagnosis is frequently challenging because the hernia sac often lies beneath an intact external oblique aponeurosis, making it interparietal and difficult to detect on physical examination. 1, 2

Anatomical Location and Characteristics

• The hernia occurs through a defect in the transversus abdominis aponeurosis along the semilunar line (Spigelian aponeurosis), most commonly in the lower abdomen between the umbilicus and anterior superior iliac spine where the posterior rectus sheath is deficient. 2, 3

• The hernial sac typically passes through the transversus and internal oblique aponeuroses but remains beneath the intact external oblique aponeurosis, creating an interparietal hernia that is masked by subcutaneous fat and overlying fascia. 2, 1

• This interparietal location explains why even moderately sized Spigelian hernias may not be clinically apparent on routine examination. 2

Clinical Symptoms

• Abdominal pain is the most common presenting symptom, occurring in approximately 80% of patients (8/10 in one series), though the pain pattern is non-specific and varies considerably between patients. 3, 2

• The pain typically localizes to the site of the hernia defect along the lateral abdominal wall, often with a cramping or colicky nature when bowel is incarcerated. 2

• Approximately 20% of patients may be completely asymptomatic, with the hernia discovered incidentally during imaging or surgery for other indications. 3, 4

• Nausea, vomiting, and abdominal distension may occur when bowel obstruction or incarceration develops. 2

Physical Examination Findings

• In palpable cases, the key diagnostic findings are a palpable hernia mass and/or a palpable hernial orifice along the semilunar line, which when present make diagnosis straightforward. 2

• For non-palpable hernias (the majority), persistent point tenderness in the Spigelian aponeurosis with a tensed abdominal wall most strongly suggests the diagnosis—absence of palpable tenderness effectively rules out Spigelian hernia. 2

• The hernia may become more apparent with maneuvers that increase intra-abdominal pressure such as coughing, standing, or Valsalva, though the overlying external oblique aponeurosis often prevents visible bulging. 2, 1

• Small hernias and hernial orifices are frequently overlooked because they are masked by subcutaneous fat and the intact external oblique aponeurosis. 2

Diagnostic Imaging

• Ultrasound is recommended for verification of diagnosis in both palpable and non-palpable Spigelian hernias, with the ability to demonstrate the hernial orifice and sac. 2, 1

• CT scan is the gold standard when clinical diagnosis is uncertain, providing detailed information about the exact anatomical features of the defect, the contents of the hernial sac, and facilitating surgical planning. 1, 2

• CT offers superior detail compared to ultrasound regarding hernial contents and can identify associated complications such as incarceration or strangulation. 2

• In the case series by Elshof et al., three of four patients had preoperative diagnosis confirmed by CT scan, with one diagnosed incidentally during surgery for inguinal hernia. 4

Risk of Complications

• Spigelian hernias carry a high risk of incarceration and strangulation due to the rigid, well-defined defect in the transversus aponeurosis, making elective surgical repair mandatory even in asymptomatic patients. 5, 6

• The narrow, rigid nature of the fascial defect predisposes to bowel incarceration, similar to femoral hernias. 5

• Emergency presentation with incarcerated or strangulated bowel requires urgent surgical intervention to prevent bowel necrosis and perforation. 6, 5

Management Approach

• Prosthetic mesh repair is the treatment of choice for most Spigelian hernias, with both laparoscopic and open approaches validated by current guidelines. 6, 5

• Laparoscopic repair (via TAPP, IPOM, or TEP techniques) is associated with lower postoperative complications and shorter hospital stay compared to open repair, though surgeon experience is critical. 5, 3

• In cases requiring urgent repair due to incarceration or strangulation, open surgical correction remains the most common approach with excellent results. 1

• If bowel resection is needed due to ischemia or perforation with contaminated surgical fields, suture repair without mesh is preferred to avoid mesh infection risk. 6

• Diagnostic laparoscopy may be useful to assess bowel viability after reduction of complicated hernias before proceeding with definitive repair. 6