Most commonly hernia develops in the abdomen, when a weakness in the abdominal wall evolves into a hole, or defect, through which adipose tissue, or abdominal organs covered with peritoneum, may protrude. Another common hernia involves the spinal discs and causes sciatica. Hernia may or may not present either with pain at the site, a visible or palpable lump, or in some cases by more complex symptoms result from pressure on an organ which has becomes "stuck" in the hernia, sometimes leading to organ disfunction.