Teaching Case

We present the case of a 69-year-old female who sustained significant blunt thoracic and abdominal wall trauma in a farmyard accident. The patient was haemodynamically stable on arrival into the emergency department, but complained of right sided abdominal pain. Secondary survey demonstrated a tender swelling in the right flank.

The patient underwent a routine trauma CT series of the thorax, abdomen & pelvis. In our institution, this constitutes arterial phase imaging of the thorax and upper abdomen, followed by portal venous phase imaging of the abdomen and pelvis. No oral contrast was administered.

Review of images of the abdomen and pelvis demonstrated an acute fat-containing right inferior lumbar hernia, with rupture of external oblique, internal oblique, and transversus abdominis muscles. The lateral wall of the ascending colon traversed the neck of the hernia, without overt evidence of herniation. There was no evidence of bowel obstruction or bowel wall injury.

Expansion of the right lateral abdominal wall musculature with subcutaneous haematoma within the right lateral abdominal wall was also evident.

Thoracic injuries included fractures of the left 7^th – 12^th ribs, without evidence of pneumothorax or haemothorax. Multilevel lumbar vertebral transverse process fractures were also identified.

Lumbar hernias are rare defects, representing 1-2% of abdominal hernias. [1] They arise in the posterolateral abdominal wall through weaknesses in lumbar musculature or posterior fascia.

Lumbar hernias are classified based on anatomical location. [1]

• Superior lumbar hernia (Grynfeltt-Lesshaft) [2]
  • • More common.
    • Arises in the superior lumbar triangle.
      • Borders: 12^th rib (superior), internal oblique muscle (anterior), erector spinae muscles (posterior). [3]
• Inferior lumbar hernia (Petit) [4]
  • • Less common.
    • Arises in the inferior lumbar triangle.
      • Borders: External oblique muscle (anterior), latissiumus dorsi muscle (posterior), iliac crest (inferior). [3]
• Diffuse lumbar hernia [1]
  • • Large defect, not contained by anatomical borders.
    • Usually traumatic or incisional.

Lumbar hernias may be congenital or acquired.

• Congenital (20%)
  • • Associated with congenital anomalies, including scoliosis, limb deformities, undescended testes, bilateral renal agenesis, anorectal malformation, cardiac defects, tracheoesophageal fistula. [5, 6]
• Acquired
  • Primary (55%)
    • Occur without specific precipitant.
    • Risk factors common to ventral abdominal wall hernias, such as obesity, chronic disease, muscular atrophy, strenuous physical activity, chronic cough.
  • Secondary (25%)
    • Identifiable cause such as surgery, local infection or trauma.
    • Traumatic hernias tend to occur in the inferior triangle. [7]

Herniation of both intraperitoneal and retroperitoneal structures has been described. [6] Complications are common to other abdominal wall hernias, including incarceration, obstruction, strangulation [8] or nerve injury (collateral branch of subcostal nerve, iliohypogastric nerve). [9]

Lumbar hernias present a diagnostic challenge, due to their relative rarity. Examination may reveal a reducible swelling with cough impulse. A painful, irreducible hernia should raise concern for strangulation. In the setting of trauma, clinicians should consider potential for significant co-existing injury such as pelvic or spinal fractures; or seatbelt-related injuries including major vascular injury, mesenteric disruption or intestinal perforation. [6, 7, 10] In non-traumatic hernias, associated congenital anomalies should be considered.

CT is the gold standard in confirming the presence of a lumbar hernia. Additionally, CT can delineate hernia anatomy and contents, identify potential hernia-related complications, or demonstrate co-existing injuries. [1, 3]

Surgical repair is usually advocated. Open, laparoscopic (transabdominal or retroperitoneal) and minimally invasive approaches have all been described. [1, 9, 11] There lacks consensus regarding operative timing and technique, due to the relative rarity of the condition with paucity of evidence in the published literature to date. [12, 13]

Interpreting radiologists should be familiar with the relevant anatomy of a lumbar hernia, and communicate this information to surgical colleagues to inform operative planning. An understanding of the potential associations of lumbar hernias is also important, such that these may be identified when reporting.