Can occur in either superior lumbar triangle of Grynfeltt-Lesshaft or inferior lumbar triangle of Petit
– Superior lumbar triangle of Grynfeltt-Lesshaft defined by 12th rib superiorly, superior border of internal oblique inferiorly, and erector spinae medially
– Inferior lumbar triangle of Petit defined by latissimus dorsi muscle medially, iliac crest inferiorly, and free border of external oblique muscle laterally
Overall, hernias are more common in superior triangle
IMAGING
• Disruption of thoracolumbar fascia at insertion of aponeurosis of internal oblique and transverse abdominal muscles
• Hernia may contain extraperitoneal fat, colon, kidney, or intraperitoneal structures (small bowel, ascites)
Most commonly involved are colon and small bowel
TOP DIFFERENTIAL DIAGNOSES
• Abdominal wall neoplasms
• Abdominal wall hematoma
• Abdominal wall lipoma
PATHOLOGY
• 80% of lumbar hernias are acquired
Can be spontaneous (especially in older patients and patients with excessive weight loss) or secondary to trauma, infection, or previous surgery in flank
Most commonly occurs following flank incision for renal surgery or iliac crest bone harvesting
• 20% of lumbar hernias are congenital
CLINICAL ISSUES
• Very difficult to detect (and often missed) on physical examination and more likely to be diagnosed on CT
• Incarceration and strangulation are uncommon because of large size of opening into hernia
Incarceration more common with acute traumatic lumbar hernias (8-10%)
• Treatment: Early surgical repair because repair becomes technically more difficult as hernia enlarges
(Left) Axial CECT shows herniation of retroperitoneal fat that is covered only by the thinned latissimus dorsi muscle in a patient with right flank discomfort.
(Right) Axial CECT in the same patient shows the site of herniation immediately above the iliac crest. The lumbar hernia is a defect in the aponeurosis of the internal oblique and transverse abdominal muscles, which should insert on the thoracoabdominal fascia that envelops the quadratus lumborum and erector spinae muscles.
(Left) Axial CECT in an elderly female patient shows a defect in the left thoracolumbar fascia through which the descending colon herniates dorsally. The thoracolumbar fascia should be a strong sheet of tissue that inserts on the iliac crest.
(Right) Axial NECT demonstrates a fascial defect in the right lumbar region with herniation of the liver and colon . Notice that while the liver is diffusely steatotic, the liver within the lumbar hernia is higher in density, probably as a result of differential perfusion due to entrapment in the hernia.
Axial NECT demonstrates a lumbar hernia with extension of the right kidney into the hernia sac.
Axial CECT shows avulsion of the muscular and tendinous insertions of the abdominal wall muscles from the left iliac wing and thoracolumbar fascia, with creation of a post-traumatic lumbar hernia . Post-traumatic lumbar hernias are rare but much more likely to be associated with strangulation or incarceration.
Coronal CECT shows avulsion of the muscular and tendinous insertions of the abdominal wall muscles from the left iliac wing and thoracolumbar fascia, with creation of a post-traumatic lumbar hernia. Post-traumatic lumbar hernias are rare but much more likely to be associated with strangulation or incarceration.
Axial NECT shows surgical absence of the left kidney with protrusion of abdominal fat through the site of the incision. The hernia is covered mostly by the thin latissimus dorsi muscle. The defect, a variant of a lumbar hernia, is through the aponeuroses of the abdominal oblique and transverse muscles.
in a patient with right flank discomfort.
in the aponeurosis of the internal oblique and transverse abdominal muscles, which should insert on the thoracoabdominal fascia that envelops the quadratus lumborum and erector spinae muscles.
in the left thoracolumbar fascia through which the descending colon 
herniates dorsally. The thoracolumbar fascia should be a strong sheet of tissue that inserts on the iliac crest.
and colon 
. Notice that while the liver is diffusely steatotic, the liver within the lumbar hernia is higher in density, probably as a result of differential perfusion due to entrapment in the hernia.
with extension of the right kidney 
into the hernia sac.
. Post-traumatic lumbar hernias are rare but much more likely to be associated with strangulation or incarceration.
of the muscular and tendinous insertions of the abdominal wall muscles from the left iliac wing and thoracolumbar fascia, with creation of a post-traumatic lumbar hernia. Post-traumatic lumbar hernias are rare but much more likely to be associated with strangulation or incarceration.
of abdominal fat through the site of the incision. The hernia is covered mostly by the thin latissimus dorsi muscle. The defect, a variant of a lumbar hernia, is through the aponeuroses of the abdominal oblique and transverse muscles.
