Prominent abdominal vein in an 81 year old male patient with retroperitoneal fibrosis. Retroperitoneal fibrosis, or Ormond's disease, is a disease of unknown origin that is characterised by the proliferation of fibrous tissue in the retroperitoneum, the abdominal cavity behind the peritoneum, which contains the kidneys, aorta, renal tract, and other organs. The fibrous tissue is causing stenosis (narrowing) of the inferior vena cava, the vein that carries blood from the lower and middle body to the heart, causing it to bulge.