Bowel obstruction may be classified by 5 different classification methods including: Open and closed, incomplete and complete, extrinsic, intrinsic and intraluminal, true and pseudo-obstruction, and finally, small bowel and large bowel. In this chapter, the extrinsic, intrinsic and intraluminal classification method will be used.

Bowel obstruction may be classified as follows:^[1][2]

• Open or closed bowel
  • Open type of bowel obstruction refers to an obstruction at a single location where the rest of the bowel is patent. A closed bowel obstruction refers to an obstruction occurring at two locations, so that there is no proximal or distal outlet.
• Complete or incomplete obstruction
  • Obstructions can either completely occlude the lumen of the bowel, or can partially (incompletely) occlude the bowel.
• Extrinsic, intrinsic/intramural or intraluminal obstruction
  • An obstruction may be due to an external cause, for example, a tumor that pushes on the bowel from the outside.
  • An obstruction may be caused by an intrinsic (intramural) wall abnormality, for example, a tumor or stricture or hematoma.
  • An intraluminal obstruction describes the process by which a luminal defect prevents the normal passage of bowel contents, for example, a foreign body, gallstone or an intussusception.
• Small or large bowel obstruction
  • Small bowel obstruction include obstructions that occur along the duodenum up to the ileocecal junction, obstructions beyond this junction are classified as large bowel obstructions. A subset of large bowel obstruction includes outlet obstructions.
• True or pseudo-obstruction
  • Ogilvie’s syndrome and adynamic (paralytic) ileus represent pseudo-obstructions, and are not true mechanical obstructions as the bowel is dilated and patent but intestinal contents are not able to pass.

Bowel obstruction classification algorithm:

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