String-of-Pearls Sign | Radiology Signs

Answer:

The String-of-Pearls Sign is caused by mechanical small bowel obstruction, where dilated loops of small intestine filled with fluid trap small gas bubbles between the closely apposed valvulae conniventes (mucosal folds). This sign is typically seen on upright or decubitus abdominal radiographs. It reflects the accumulation of multiple small gas bubbles lined up in a row or series within the dilated, fluid-filled small bowel loops, indicating increased intraluminal pressure and impaired bowel motility.

Why is it called so?

It is called the String-of-Pearls Sign because the trapped gas bubbles appear as a linear row of small, rounded or oval gas pockets on the radiograph, resembling a string of pearls or beads aligned along the bowel wall.

Pathophysiology

In mechanical small bowel obstruction, distal bowel obstruction causes proximal accumulation of fluid and gas. The bowel dilates and fluid surrounds the bowel lumen, creating a meniscus effect that shapes the entrapped intraluminal gas bubbles into discrete rounded pockets. These gas pockets become visible between the valvulae conniventes, which are closely spaced mucosal folds of the small intestine, resulting in the characteristic linear arrangement of gas bubbles.

Alternative names:
String-of-Beads Sign (used interchangeably for this same small-bowel-obstruction finding)

Other associated named signs:
Stepladder sign (also seen in small bowel obstruction). Note: “string of beads” is also a distinct, unrelated vascular imaging term for the alternating stenoses/aneurysmal dilatations of renal artery fibromuscular dysplasia – a completely different entity from this gastrointestinal sign.

References

1. Nevitt PC. The string of pearls sign. Radiology. 2000;214(1):157-158.
2. Burgess LK, et al. The String of Pearls Sign. Abdom Radiol (NY). 2016;41(7):1454-1455.