Obturator canal fat plug: a pre-hernial condition?

Although obturator hernias are rare, they are associated with a high mortality, as diagnosis is often delayed and the condition tends to occur in the elderly. Previous researchers have postulated that obturator hernias begin with invagination of pre-peritoneal fat through the pelvic orifice of the obturator canal, forming a fat plug. With chronically raised intra-abdominal pressure, or sudden weight loss, this can progress to a clinical obturator hernia. We dissected 95 Caucasian cadaveric hemi-pelvises (47 males; 48 females) in order to investigate the frequency of fat plugs and examine the validity of the current hypothesis regarding obturator hernia pathogenesis. The mean age (SD) of the specimens was 83 (9) years, with 48 (24 male; 24 female) from the left side and 47 (23 male; 24 female) from the right side. A fat plug was found in 21 canals (22%); the majority were female (71%, P = 0.03), and right sided (62%, P = 0.20). The mean (SD) length was 20.0 mm (6.3 mm), with mean diameter 5.9 mm (1.8 mm). A shallow peritoneal dimple was also found overlying fat plugs in two specimens. No visceral herniations were found. The sex and side distribution of the obturator canal fat plugs we found are similar to those of obturator hernias reported in the literature, supporting the hypothesis that fat plugs are pre-hernial. It is unlikely that fat plugs are a high-risk condition, but dimples over these plugs may be a marker of potential hernia formation.