Inferior Lumbar (Petit's) Hernia

A 78-year-old woman with carcinoma of the right colon underwent CT of the abdomen and pelvis to rule out metastasis. The scan showed a musculoaponeurotic defect above the left iliac wing, with a herniated loop of colon. A soft, reducible 4 × 6-cm mass that increased with coughing was found in her left flank. The patient had not had any surgery in this area. This was an inferior lumbar hernia (Petit's hernia). No treatment was given, because the hernia was asymptomatic, but regular follow-up was recommended.

Dr Virendra Parikh of Fort Wayne, Ind, points out that although defects can occur anywhere in the lumbar area, Petit's hernia is a rare condition. It results from a posterior abdominal wall weakness that may be congenital, spontaneous, or surgically or traumatically induced. The defect is bounded by the latissimus dorsi muscle posteriorly, the external oblique muscle anteriorly, and the iliac crest inferiorly. The diagnosis can be difficult, especially if the hernia is small or the patient obese. CT can define the defect, evaluate the contents, and rule out other conditions.