A 45-year-old man complaining of abdominal pain-Spigelian hernia

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 Spigelian hernia


1. Cause and Etiology

Cause

Spigelian hernias result from a defect or weakness in the Spigelian aponeurosis, a layer of abdominal wall musculature located between the rectus abdominis medially and the semilunar line laterally.

Etiologic Factors

  • Congenital defects in the Spigelian fascia (less common)
  • Acquired weakness of the abdominal wall:
    • Increased intra-abdominal pressure from chronic cough, obesity, heavy lifting, or ascites
    • Prior abdominal surgeries (especially laparoscopic)
    • Pregnancy (due to stretching and thinning of the abdominal wall)
    • Trauma

2. Pathophysiology

Spigelian hernias occur through defects in the Spigelian fascia, most commonly at the Spigelian hernia belt, a transverse 6-cm wide zone located just below the umbilicus and above the inferior epigastric vessels. The hernia often occurs at or near the level of the arcuate line, where the posterior sheath of the rectus abdominis muscle ends, leaving only the transversalis fascia to resist intra-abdominal pressure.

The hernia sac can contain:

  • Preperitoneal fat
  • Omentum
  • Small bowel
  • Colon (occasionally)

Because the hernia neck tends to be narrow and rigid, there is a high risk of incarceration and strangulation compared to other abdominal wall hernias.

3. Epidemiology

  • Rare: Spigelian hernias account for 0.1–2% of all abdominal wall hernias.
  • Age: Typically occurs in individuals aged 40–70 years.
  • Sex: Slight female predominance due to higher abdominal wall stress from pregnancy.
  • Side: Slight right-sided predominance, though it can occur on either side.

4. Clinical Presentation

Symptoms

  • Localized lower abdominal pain (usually intermittent and dull)
  • Palpable mass in the lower lateral abdomen (may not be evident in obese patients)
  • Discomfort during physical activity, coughing, or standing
  • Incarceration signs: Acute onset of severe pain, vomiting, and bowel obstruction symptoms if the hernia is incarcerated or strangulated.

Physical Exam

  • Tender mass lateral to the rectus muscle, especially at the semilunar line
  • May be reducible or non-reducible
  • Sometimes only elicited during the Valsalva maneuver or standing

5. Imaging Features

Ultrasound

  • First-line, especially for dynamic assessment
  • Shows a defect in the Spigelian fascia with protrusion of fat or bowel
  • High-resolution, real-time imaging during Valsalva increases sensitivity

Computed Tomography (CT)

  • Gold standard for diagnosis
  • Shows a defect in the Spigelian aponeurosis (typically 1–4 cm)
  • Hernia sac may contain fat, bowel loops, or omentum
  • CT helps distinguish Spigelian hernia from other hernias and masses

MRI

  • May be used in equivocal cases or to assess soft tissue details

6. Treatment

Surgical Repair (Definitive Treatment)

  • Elective surgery is recommended due to the high risk of complications.
  • Options include:
    • Open repair with primary suture closure or mesh reinforcement
    • Laparoscopic repair (increasingly preferred due to less postoperative pain and faster recovery)
      • Intraperitoneal onlay mesh (IPOM)
      • Totally extraperitoneal (TEP) approach

Emergency Surgery

  • Required in cases of incarceration or strangulation
  • May involve resection of non-viable bowel

7. Prognosis

Outcomes

  • Generally excellent if diagnosed and treated early
  • Low recurrence rates after appropriate surgical repair (especially with mesh)

Complications (if untreated)

  • Incarceration (17–24% of cases)
  • Strangulation (up to 14%)
  • Bowel obstruction
  • Bowel ischemia or perforation

Prognosis by Type of Repair

  • Laparoscopic repairs have slightly lower recurrence rates and fewer complications compared to open repair, though the choice depends on the surgeon's expertise and hernia characteristics.

Summary Table

Aspect

Details

Cause

Defect in Spigelian fascia

Etiology

Congenital or acquired; risk factors include obesity, prior surgery

Pathophysiology

Herniation through the Spigelian aponeurosis near the arcuate line

Epidemiology

0.1–2% of abdominal hernias; middle-aged adults; slight female predominance

Clinical Features

Lateral lower abdominal pain, mass, possible incarceration

Imaging

Ultrasound, CT (gold standard), and MRI in select cases

Treatment

Surgical repair (open or laparoscopic); emergency if strangulated

Prognosis

Excellent post-repair; high risk of complications if untreated

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Case study: A 45-Year-Old Male Presenting with Abdominal Pain 
Spigelian Hernia

History and Imaging

  1. A 45-year-old male presented with complaints of abdominal pain.

  2. An abdominopelvic CT scan was performed using an oral contrast agent.

Quiz:

  1. Multiple types of hernias are visible in the provided images.
     (1) True
     (2) False 

    Explanation:
    The CT images show both a right-sided Spigelian hernia and a left-sided inguinal hernia, confirming the presence of more than one type of hernia.

  2. There is a(n) ________ hernia relative to the rectus abdominis muscle on the right abdominal wall.
     (1) Medial
     (2) Lateral 

    Explanation:
    A Spigelian hernia typically occurs lateral to the rectus abdominis, along the semilunar line (Spigelian line), where the transversus abdominis aponeurosis is located.

  3. What type of hernia is present on the right abdominal wall?
     (1) Amyand hernia
     (2) Petit hernia
     (3) Richter hernia
     (4) Spigelian hernia

    Explanation:
    The CT shows herniation of mesenteric fat and a contrast-filled small bowel loop lateral to the rectus muscle, deep to the external oblique and superficial to the internal oblique and transversus abdominis—classic for a Spigelian hernia.

  4. Signs of bowel obstruction are present.
     (1) True
     (2) False 

    Explanation:
    There is no evidence of bowel obstruction, such as proximal bowel dilation, air-fluid levels, or collapsed distal segments. The herniated small bowel loop appears to be patent without signs of compromise.

Findings and Diagnosis

Key Imaging Findings:
CT imaging reveals a herniation on the right abdominal wall, located lateral to the rectus abdominis muscle, containing mesenteric fat and a contrast-filled loop of small bowel. The hernia sac lies deep to the external oblique muscle but superficial to the internal oblique and transversus abdominis muscles.
There is no evidence of bowel obstruction.
An inguinal hernia is also noted on the left side, best appreciated on coronal imaging.

Differential Diagnosis (Right-Sided Hernia)

  • Inguinal hernia

  • Lumbar hernia

  • Spigelian hernia

  • Umbilical hernia

Final Diagnosis: Spigelian hernia

Discussion

Spigelian Hernia

Pathophysiology
A Spigelian hernia is caused by a defect in the aponeurosis of the transversus abdominis muscle, also known as the Spigelian fascia. This fascia extends from the ninth costal cartilage to the pubic tubercle and is bordered laterally by the fibers of the internal oblique muscle. Its medial boundary lies just below the point where the aponeurosis of the external oblique muscle becomes the anterior rectus sheath. The anterior surface of the Spigelian fascia is covered by the external oblique aponeurosis, while its posterior aspect is adjacent to preperitoneal fat and the peritoneum.

Epidemiology
Spigelian hernia is a relatively rare type of ventral hernia, accounting for less than 1% of all abdominal wall hernias. Reported incidence rates range between 0.1% and 2%. It typically presents in patients between the fourth and seventh decades of life.

Clinical Presentation
Most patients with a Spigelian hernia are asymptomatic. Some may experience localized pain, and in certain cases, a palpable bulge may be noted. However, a visible or palpable protrusion on the abdominal wall may not always be evident due to its location deep within the muscle layers.
Patients may present with signs of complications such as strangulation, bowel obstruction, bowel ischemia, or perforation.

Imaging Features
CT imaging is instrumental in visualizing Spigelian hernias and evaluating potential complications. The hernia typically contains fat or bowel loops protruding through the abdominal wall. The hernia sac is located along the semilunar line (also referred to as the Spigelian line), situated lateral to the rectus abdominis muscle and passes through a defect in the transversus abdominis aponeurosis (Spigelian fascia).

Treatment
The mainstay of treatment is surgical repair. While traditional open surgery was once the standard, laparoscopic techniques are now commonly employed for a less invasive approach.

References

  1. Mittal, T., Kumar, V., Khullar, R., Sharma, A., Soni, V., Baijal, M., & Chowbey, P. K. (2008). Spigelian hernia: Safe laparoscopic repair. Journal of Minimally Access Surgery, 4(3), 95–97. https://doi.org/10.4103/0972-9941.45214
  2. Larson, D. W., & Farley, D. R. (2002). Spigelian hernias: Repair and outcome for 81 patients. World Journal of Surgery, 26(10), 1277–1281. https://doi.org/10.1007/s00268-002-6369-2
  3. Skandalakis, P. N., Zoras, O., Skandalakis, J. E., & Mirilas, P. (2006). Spigelian hernia: Surgical anatomy, embryology, and technique of repair. The American Surgeon, 72(1), 42–48.
  4. Losanoff, J. E., Richman, B. W., & Jones, J. W. (2002). Spigelian hernia: Review of the literature and report of a case. The American Surgeon, 68(11), 1031–1035.
  5. Light, D., Chattopadhyay, D., Bawa, S., & Simons, A. (2013). Radiological and clinical features of Spigelian hernia. Annals of the Royal College of Surgeons of England, 95(2), 98–00. https://doi.org/10.1308/003588413X13511609956935

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