String of Pearls and String of Beads Sign: Small Bowel Obstruction

Answer:

A row of small rounded gas bubbles trapped between the valvulae conniventes of dilated, fluid-filled small bowel loops on an erect or decubitus abdominal radiograph. It means mechanical small bowel obstruction. The bubbles are the only gas left in a loop otherwise full of fluid. The string-of-beads sign is the same finding under a different name.

Why is it called so?

The bubbles sit in a line of evenly spaced rounded gas pockets along the upper margin of the loop, like pearls on a string. The same appearance is also described as beads, so string of beads means the same finding.

Pathophysiology

Obstruction stops forward flow, so fluid accumulates proximally and the loop dilates. As the loop fills with fluid, the remaining gas rises and is pinched into discrete rounded pockets by the valvulae conniventes, the closely spaced circular mucosal folds of the small intestine. On an erect or decubitus film those pockets line up along the uppermost wall. The sign needs two things at once: enough fluid to displace the gas, and enough gas left to be visible. That is why it appears on some obstructed films and not others.

Alternative names:
String-of-beads sign, string of pearls appearance, pearl necklace sign (all for this same small bowel finding)

Other associated named signs:
Stepladder sign and the gasless abdomen, both also seen in bowel obstruction. The phrase “string of beads” is also used for four unrelated findings in other organs, set out below.

One phrase, five different diagnoses

Pearls and beads name at least five unrelated findings. Only the first is the sign on this page; organ and modality separate the rest.

What the sign does and does not tell you

• It does not grade the obstruction. No indexed study quantifies the sign as a marker of high-grade or complete obstruction, so do not report it as one.
• It needs a horizontal-beam film. On a supine radiograph the residual gas spreads along the loop instead of collecting into discrete bubbles.
• Its absence proves nothing. A loop completely full of fluid gives a gasless abdomen, itself a sign of obstruction.
• The management decision is made on CT. The WSES Bologna guidelines make CT the technique of choice when the adhesive cause is unsure, or when contraindications to non-operative management may be present.

Frequently asked questions

Is the string of beads sign the same as the string of pearls sign?

In the small bowel, yes. Both names describe the same row of gas bubbles trapped between the valvulae conniventes of a dilated, fluid-filled loop. Outside the small bowel the phrase names unrelated findings in the renal and carotid arteries, the bile ducts and the fallopian tube, so the organ and modality decide which sign is meant.

What does the beads on a string sign mean in pelvic inflammatory disease?

On transvaginal ultrasound it describes small mural nodules on the inner wall of a dilated, thin-walled fallopian tube, and indicates chronic tubal inflammatory disease. Timor-Tritsch and colleagues found that a thick wall with the cogwheel sign pointed to acute disease instead, while an incomplete septum was the best marker of tubal inflammatory disease, present in 92% of cases.

Does the string of pearls sign mean the obstruction is complete or high grade?

No. No indexed study quantifies the sign as a marker of grade. It indicates mechanical obstruction, but the grade, the transition point and any ischaemic complication are assessed on CT.

What is the string of pearls appearance in the ovary?

A different sign entirely. It describes small follicles arranged around the periphery of the ovary, also called the pearl necklace appearance, and refers to polycystic ovarian morphology. The 2023 international evidence-based guideline sets the threshold at 20 or more follicles per ovary in at least one ovary.

References

1. Nevitt PC. The string of pearls sign. Radiology. 2000;214(1):157-158. PMID 10644116.
2. Burgess LK, Lee JT, DiSantis DJ. The String of Pearls Sign. Abdom Radiol (NY). 2016;41(7):1435-1436. PMID 26907709.
3. Huang Z, Lin H, Liu M, et al. Computed tomography for diagnosis and risk stratification of small bowel obstruction: a systematic review and meta-analysis. Eur J Radiol. 2026;203:112999. PMID 42308707.
4. Ahmad SJS, Drvaric I, Ahmed AR, et al. From obstruction to ischaemia: a systematic review and meta-analysis on the diagnostic accuracy of CT scans in identifying small and large bowel obstruction, underlying causes and predicting critical complications in adults. BMJ Open. 2025;15(11):e103887. PMID 41248364.
5. Ten Broek RPG, Krielen P, Di Saverio S, et al. Bologna guidelines for diagnosis and management of adhesive small bowel obstruction (ASBO): 2017 update of the evidence-based guidelines from the World Society of Emergency Surgery ASBO working group. World J Emerg Surg. 2018;13:24. PMID 29946347.
6. Gornik HL, Persu A, Adlam D, et al. First International Consensus on the diagnosis and management of fibromuscular dysplasia. Vasc Med. 2019;24(2):164-189. PMID 30648921.
7. European Association for the Study of the Liver. EASL Clinical Practice Guidelines on sclerosing cholangitis. J Hepatol. 2022;77(3):761-806. PMID 35738507.
8. Dave M, Elmunzer BJ, Dwamena BA, Higgins PD. Primary sclerosing cholangitis: meta-analysis of diagnostic performance of MR cholangiopancreatography. Radiology. 2010;256(2):387-396. PMID 20656832.
9. Timor-Tritsch IE, Lerner JP, Monteagudo A, Murphy KE, Heller DS. Transvaginal sonographic markers of tubal inflammatory disease. Ultrasound Obstet Gynecol. 1998;12(1):56-66. PMID 9697286.
10. Teede HJ, Tay CT, Laven J, et al. Recommendations from the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. Hum Reprod. 2023;38(9):1655-1679. PMID 37580037.