Lumbar hernias can be superior (Grynfelt) and inferior (Petit). Inferior lumbar hernias are extremely rare and, therefore, are associated with diagnostic difficulty. We present a case of a primary spontaneous inferior lumbar hernia in a 79-year-old woman that was initially diagnosed as a large lipoma on ultrasound. The first operation was abandoned and an open mesh repair was conducted. Lumbar hernias can be primary acquired (55%), secondary acquired (25%) or congenital (20%). Cross-sectional imaging by CT or MRI appears to be the gold standard in diagnosis as ultrasound may lead to misdiagnosis. Strangulation, incarceration and obstruction are recognised complications, requiring prompt surgical intervention. There are currently no guidelines for surgical managements, although laparoscopic surgery may give the best results. In view of the scarcity of published cases, we aim to add to the literature to raise the index of suspicion and to promote prompt surgical management of lumbar hernias.