Surgery can be performed directly for small omphaloceles, which will require a short stay in the nursery department, or in a staged manner for large omphaloceles, which will require several weeks stay. Staged closure requires a temporary artificial holding sac (a silo) to be placed over the abdominal organs and sutured to the abdominal wall. This can be made of non-adhesive dressing. The silo is gradually reduced in size at least once daily until all of the viscera have been returned to the abdominal cavity. This is repeated for several days to a week until surgical closure of the fascia/skin can be done. Closure may require a patch that can be rigid or non-rigid and made of natural biomaterials such as a bovine pericardium or artificial materials. The skin is then closed over the patch and it is re-vascularised by the body's liver blood vessels post-surgery. The staged surgery is required, as rushed reduction of the exomphalos compromises venous return and ventilation, as it raises intra-abdominal pressure. In some cases, stretching of the abdominal wall to accommodate intestinal contents may be required.