Name four radiographic signs of mechanical bowel obstruction

1. A transition point (enlarged bowel loops proximal to the site of obstruction and small to normal-caliber bowel loops distal to site the of obstruction)
2. A large quantity of fluid in the bowel loops proximal to the obstruction
3. The stair-step sign (i.e., air-fluid levels on an upright exam)
4. The string of pearls sign