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Spigelian Hernia

Case Introduction

A 41 year old male presented to the Emergency Department (ED) one day following a bicycle accident. He reported striking a “bump” in the asphalt, causing the handlebar end to strike him in the abdomen. The patient endorsed pain and tenderness with a “protrusion” at this location and denied any other injuries. He had no nausea or vomiting and returned to his house following the crash. This tender mass persisted at which time he decided to present to the ED for evaluation.
On exam, the patient was hemodynamically stable in no distress. His abdominal exam was notable for a reducible hernia located inferior to the umbilicus and along the lateral abdomen, superior to the iliac crest. This site was tender and ecchymotic. He denied any difficulty micturating or defecating.
In addition to routine blood work, a CT scan of the abdomen and pelvis was performed. This identified a hernia in the left lower quadrant of the abdomen containing small bowel without evidence of obstruction.

Discussion

Spigelian hernias are a rare form of ventral hernia characterized by protrusion of abdominal contents or peritoneum through a defect in the Spigelian fascia. The Spigelian fascia is composed of transversus abdominis and internal oblique aponeurosis. Typical etiologies include pathology that increases intra-abdominal pressure, abdominal wall trauma, or degeneration of abdominal aponeurotic layers. In degenerative cases, the hernia can be idiopathic and has been referred to as a “spontaneous lateral ventral hernia”.1Skandalakis PN, Zoras O, Skandalakis JE, Mirilas P. Spigelian hernia: surgical anatomy, embryology, and technique of repair. Am Surg. 2006 Jan;72(1):42-8.

Differential diagnosis includes:

  • Rectus sheath hematoma
  • Incisional hernia
  • Ventral hernia
  • Malignancy of soft tissue or abdominal wall
  • Abscess
  • Lymphadenopathy
Spigelian hernia traumatic clinical picture
Image of the patients abdomen. Note the protruding hernia left of midline and inferior to the rib margin.
Spigelian hernias are rare, representing less than 2% of all abdominal wall hernias.2Larson DW, Farley DR. Spigelian hernias: repair and outcome for 81 patients. World J Surg. 2002 Oct;26(10):1277-81 Incidence increases in women over 60. Patients with COPD, chronic cough, obesity, pregnancy, and ascites are at increased risk. Patients with connective tissue disorders such as Ehlers-Danlos syndrome are also at increased risk.
The Spigelian fascia is located lateral to the rectus abdominis muscle along the semilunar line. The fascial layer is made up of the aponeurosis located between the rectus abdominis medially and the semilunar line laterally. Herniation typically occurs inferior or at the level of the arcuate line which demarcates the termination of the posterior layer of the rectus sheath containing transversus abdominis aponeurosis. The intersection of the semilunar line and arcuate line represent a physiological weakness as the posterior rectus sheath is no longer present, allowing herniation lateral to the rectus muscle.
surgical anatomy of a spigelian hernia
Spigelian Hernia surgical anatomy. Drawing depicting a left-sided Spigelian hernia, axial view. Note the Spigelian hernia penetrating the Spigelian fascia (red asterisks) with an intact External oblique aponeurosis. (1) Semilunar line, (2) Rectus abdominis muscle, (3) External oblique muscle with aponeurosis, (4) Internal oblique muscle, (5) Transverse abdominal muscle, (6) Fascia transversalis, (7) Pre-peritoneal fat, (8) Peritoneum1Hanzalova, I., et al. "Spigelian hernia: current approaches to surgical treatment—a review." Hernia (2022): 1-7.
Spigelian hernias frequently present as painless masses through the abominable wall. Patients often endorse a bulge which worsens when standing. Acuity may be acute, as in the case of our patients’ trauma, or more chronic as is seen in patients with degenerative changes. Pain severity can vary greatly, especially depending on the contents contained within the hernia. It is important to clarify the natural history of the disease and consider the potential for incarceration or strangulation. Risk factors for increasing intra-abdominal pressure should be reviewed.
On physical exam, palpate for any hernias. Because they can be deep to the external oblique musculature, they can be difficult to detect clinically. Sensitivity can increase by having them stand up and with valsalva maneuvers. Asking them to perform a situp or crunch may also be useful. Not all patients will have a palpable mass despite augmentation maneuvers. Approximately 50% of Spigelian hernias are not picked up on physical exam, a limitation that is amplified in obese patients.
AbdPelv CT - Left lower quadrant spigelian hernia containing small bowel axial
Axial view of the CT abdomen and pelvis showing the spigelian hernia
AbdPelv CT - Left lower quadrant spigelian hernia containing small bowel coronal
Coronal view of the Spigelian hernia on the patients left (right side of screen)
In some cases, the hernia may remain undiagnosed and asymptomatic until a patient presents with signs and symptoms of incarceration, strangulation or obstruction. In those cases, the patient is likely to be more tender and have other associated gastrointestinal symptoms such as nausea and vomiting. Studies have found that Spigelian hernias will incarcerate up to 27% of the time. Concerning features that suggest immediate surgical intervention include peritonitis or irreducible hernia especially when coupled with other evidence of strangulation, obstruction or perforation.

Diagnosis can be made clinically if the hernia or bulge is palpated at the semilunar line. More commonly, imaging is needed. Some clinicians may begin with ultrasound with or without valsalva maneuvers to express the hernia sonographically. If concern is high despite the above, CT scan provides the most diagnostically accurate modality for diagnosing a Spigelian hernia.3Campos SM, Walden T. Images in clinical medicine. Spigelian hernia. N Engl J Med. 1997 Apr 17;336(16):1149.

Surgical intervention is the standard of care for Sigelian hernias due to their propensity to incarcerate and strangulate. Repair can be performed with open, laparoscopic or robotic approaches, with the minimally invasive approaches being preferred. Patients who have their hernia repaired successfully without any evidence of strangulation or incarceration have an excellent prognosis and outcome. Patients who have evidence of bowel ischemia or vital sign instability have increased morbidity and mortality.4Polistina FA, Garbo G, Trevisan P, Frego M. Twelve years of experience treating Spigelian hernia. Surgery. 2015 Mar;157(3):547-50.

Case Conclusion

Surgery was consulted and the patient was offered admission for elective repair. The patient declined admission, citing he would like to pursue surgical options in the outpatient setting. General surgery clinic information was provided, and the patient was subsequently discharged from the ED in stable condition. The patient has not followed up with the trauma team and has subsequently been lost to follow up.

3 Key Points

  1. A Spigelian hernia is a rare form of a ventral hernia
  2. Characterized by a defect in the Spigelian fascia, which is composed of transversus abdominis and internal oblique aponeurosis
  3. High rates of incarceration and strangulation make surgical intervention the standard of care

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