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Table of Contents
Year : 2020  |  Volume : 28  |  Issue : 3  |  Page : 179-180

Scruples over speckles

Division of Rheumatology, Boston University Medical Center, Boston, MA, USA

Date of Submission19-Dec-2019
Date of Decision11-Feb-2020
Date of Acceptance14-Feb-2020
Date of Web Publication25-May-2020

Correspondence Address:
Dr. Eugene Y Kissin
Boston University, 72 E Concord St., Evans 501, Boston, MA 02118
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JMU.JMU_122_19

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The “snowstorm” sign refers to the ultrasound appearance of motile hyperechoic specks within synovial fluid and has been reported to have a high specificity for gout. We describe three additional etiologies commonly encountered in the rheumatology clinic that can produce a snowstorm: calcium pyrophosphate deposition disease, fibrin collections/rice bodies, and gas bubbles in viscous synovial fluid.

Keywords: Calcium pyrophosphate, gout, rice body, snowstorm

How to cite this article:
Persons B, Kissin EY. Scruples over speckles. J Med Ultrasound 2020;28:179-80

How to cite this URL:
Persons B, Kissin EY. Scruples over speckles. J Med Ultrasound [serial online] 2020 [cited 2023 Mar 22];28:179-80. Available from: http://www.jmuonline.org/text.asp?2020/28/3/179/285047

Monosodium urate (MSU) crystals deposited in the joints and soft tissues elicit the inflammatory reaction of gout, the most prevalent form of inflammatory arthritis. In addition to detecting MSU crystals on synovial aspiration, evidence for gouty arthritis can frequently be seen on radiographs and on ultrasound (US) joint imaging. US findings of gouty arthritis include the “double-contour” sign, which corresponds to the deposition of MSU crystals on the surface of hyaline cartilage, subclinical tophaceous deposits, and the “snowstorm” sign, where hyperechoic aggregates are seen as free-floating specks in synovial fluid.[1] Both recent meta-analyses and a large observational study find the snowstorm sign to have a specificity of 90% for gout.[2],[3],[4]

In the observational study done by Ogdie et al., however, note is made that the snowstorm sign can be seen in calcium pyrophosphate deposition (CPPD) disease as well.[4] This in mind, we would like to report an expanded list of conditions that can produce free-floating hyperechoic specks in synovial fluid. The figure below displays US images and resultant aspirates from four patients seen in clinic over a 1-month period whose joints had a snowstorm appearance on US. Images have been obtained using a GE Logiq e device with 12 L probe set at 12 MHz. Four different etiologies as confirmed by microscopy are identified: fibrin aggregates [Figure 1]a, gas bubbles [Figure 1]b, calcium pyrophosphate crystals [Figure 1]c, and MSU crystals [Figure 1]d.
Figure 1: In each panel are displayed ultrasound image and corresponding joint aspirate with arrowheads indicating representative lesions. (a) Knee effusion, lateral transverse view, containing fibrin aggregates in a rheumatoid arthritis patient. (b) Posterior longitudinal view of popliteal cyst with hyperechoic specks due to gas bubbles suspended in viscous synovial fluid. (c) Posterior longitudinal view of popliteal cyst with calcium pyrophosphate aggregates. (d) Anterior longitudinal view of knee effusion from a patient with gout and hyperechoic specks due to monosodium urate crystals

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“Rice bodies” are collections of fibrin and leukocytes that are most commonly seen in rheumatoid arthritis but that have been linked to a variety of inflammatory joint conditions.[5] Befitting the name, the classic description has been of smooth, white granules that resemble rice, but intra-articular aggregates of fibrin come in a range of morphologies, some of which have previously been described as producing hyperechoic specks on US in a pattern similar to what we report.[6],[7]

The development of free-floating specks has also been reported under US after joint traction, commonly referred to as “knuckle cracking,” suggesting that manipulation is one process by which the development of intra-articular gas bubbles regularly occurs.[8],[9] Our experience suggests that bubbles can be seen in patients with osteoarthritis resulting in chronic effusions with very high viscosity as well.

As mentioned, CPPD is additionally known to manifest as synovial specks on ultrasound. In a meta-analysis of US findings in CPPD, 12% of descriptive terms reviewed are of intra-articular hyerechoic bodies or “spots without acoustic posterior shadowing,” which is similar to the 10% incidence of the snowstorm pattern for CPPD patients reported by Ogdie et al.[4],[10] These relatively common causes of mobile hyperechoic specks in synovial fluid should be considered before assuming that the snowstorm sign confirms a diagnosis of gout.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Filippucci E, Di Geso L, Grassi W. Tips and tricks to recognize microcrystalline arthritis. Rheumatology (Oxford) 2012;51 Suppl 7:vii18-21.  Back to cited text no. 1
Lee YH, Song GG. Diagnostic accuracy of ultrasound in patients with gout: A meta-analysis. Semin Arthritis Rheum 2018;47:703-9.  Back to cited text no. 2
Zhang Q, Gao F, Sun W, Ma J, Cheng L, Li Z. The diagnostic performance of musculoskeletal ultrasound in gout: A systematic review and meta-analysis. PLoS One 2018;13:e0199672.  Back to cited text no. 3
Ogdie A, Taylor WJ, Neogi T, Fransen J, Jansen TL, Schumacher HR, et al. Performance of ultrasound in the diagnosis of gout in a multicenter study: Comparison with monosodium urate monohydrate crystal analysis as the gold standard. Arthritis Rheumatol 2017;69:429-38.  Back to cited text no. 4
Forse CL, Mucha BL, Santos ML, Ongcapin EH. Rice body formation without rheumatic disease or tuberculosis infection: A case report and literature review. Clin Rheumatol 2012;31:1753-6.  Back to cited text no. 5
Popert AJ, Scott DL, Wainwright AC, Walton KW, Williamson N, Chapman JH. Frequency of occurrence, mode of development, and significance or rice bodies in rheumatoid joints. Ann Rheum Dis 1982;41:109-17.  Back to cited text no. 6
Spence LD, Adams J, Gibbons D, Mason MD, Eustace S. Rice body formation in bicipito-radial bursitis: Ultrasound, CT, and MRI findings. Skeletal Radiol 1998;27:30-2.  Back to cited text no. 7
Jones AR, Yelverton CJ, Bester C. Ultrasound imaging of the trapeziometacarpal articular cavity to investigate the presence of intraarticular gas bubbles after chiropractic manipulation. J Manipulative Physiol Ther 2014;37:476-84.  Back to cited text no. 8
Malghem J, Omoumi P, Lecouvet FE, Vande Berg BC. Presumed intraarticular gas microbubbles resulting from a vacuum phenomenon: Visualization with ultrasonography as hyperechoic microfoci. Skeletal Radiol 2011;40:1287-93.  Back to cited text no. 9
Filippou G, Adinolfi A, Iagnocco A, Filippucci E, Cimmino MA, Bertoldi I, et al. Ultrasound in the diagnosis of calcium pyrophosphate dihydrate deposition disease. A systematic literature review and a meta-analysis. Osteoarthritis Cartilage 2016;24:973-81.  Back to cited text no. 10


  [Figure 1]

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