STRANGULATED SMALL BOWEL OBSTRUCTION
A patient presents with nausea and vomiting, is found to have small bowel obstruction, and is to be admitted to the hospital. The hospitalist and general surgeon disagree over whether strangulation is present. Can we recognize strangulated small bowel obstruction at the bedside?
Strangulation means intestinal ischemia. Most of the time this is caused by a “closed loop obstruction,” meaning there is obstruction not only distally but also proximally, preventing the release of pressure. Small intestinal causes include hernia and torsion of a loop of bowel around an adhesive band. Any colon obstruction can cause a closed loop obstruction if the cecal valve is competent, for example, colon cancer. The most common colonic causes include sigmoid and cecal volvulus.
So how do we decide who might have strangulation? The consulting surgeon on this case says if there is no CT diagnosis of a closed loop, then the patient does not need surgery. But in well-designed studies, this finding is a low as 43% sensitive.(Sheedy Radiology 2006) CT sensitivity overall has been reported as high as 100% but that is when it is used as its own gold standard.(Frager Am J Roentgenol 1996)
Clinical indications of strangulation include the systemic inflammatory response syndrome (tachycardia, fever, leukocytosis), shock or acidosis, and guarding and rebound tenderness. These are all signs of advanced ischemia. Ideally we want to diagnose these patients earlier but in the early stages we do not have a proven approach. And yet, as with all things clinical, it starts with our risk stratification at the bedside.
Clinical gestalt is hard to study but is probably the most important diagnostic intervention we do. Did the patient get better after nasogastric decompression? Do they look well or ill? Is he or she looking worse than an hour ago? With an equivocal CT, these bedside considerations help us decide when to proceed with surgery.
Take home points:
Don’t completely trust the CT for diagnosing strangulated SBO
Shock, acidosis, and SIRS indicate strangulation has occurred
Bedside worsening suggests the need for surgery
Sheedy SP, Earnest F 4th, Fletcher JG, Fidler JL, Hoskin TL.
Radiology. 2006 Dec;241(3):729-36.