This document discusses the use of ultrasound in the diagnosis of inflammatory arthritis such as gout and calcium pyrophosphate dihydrate crystal deposition disease (CPPD). It outlines the indications for ultrasound evaluation and describes the sonographic appearance of urate crystals, CPPD crystals, basic calcium phosphate crystals. While the double contour sign cannot reliably distinguish between gout and CPPD, combining power Doppler and lab tests like serum urate levels improves diagnostic accuracy. Systematic scanning of multiple joints and tendons along with clinical findings provides the most accurate assessment for diagnosing crystal-induced arthritides. Arthrocentesis remains the gold standard for definitive diagnosis.

3. Conclusion
US from bench to bed
Indications

4. Indications

5. 1. Diagnosis and Differential diagnosis with other
inflammatory arthritis,
2. Detection of the joint effusion (quantity, aspect) and
synovitis (symptomatic or asymptomatic),
3. Detection of Deposits at Hyaline cartilage , fibrocartilage
and Tendons ,

6. 4. Evaluation of Bone contour (erosions, osteophytes),
5. Monitoring of the disease progression and response to
treatment,
6. US-guided aspiration or injection.

7. Sonography from bench to bed

8. ↑water↓ Acoustic
impedance  ↓
Reflection 
Hypoechoic

9. Monosodium urate crystals

10. ↑Acoustic impedance
↑Reflection
Hyperechoic spots

14. NTUH

19. Calcium pyrophosphate dihydrate Crystals

20. Each unit cell of crystalline CPPD contains one
pyrophosphate (P2O7) for every 2 calciums and
2 waters of hydration, yielding a structural
formula of Ca2P2O7.2H20.
↑ ↑ Reflection
Hyperechoic DEPOSITS

26. Is the Double Contour Sign Specific for Gout?

27. Löffler C et al. 2015
225
Acute arthritis + DC +PD+SUA
Arthrocentesis
Sensitivity of DC sign for crystalline
arthritides was 85% and specificity 80%
Specificity for gout was 64%, for CPPD 52%
Degree 2 and 3 Doppler signals were highly
associated with gout and less with CPPD (p < 0.01)

28. DC + PD+ SUA  ↑ specificity for gout to > 90%
and resulted in a 7-fold ↑ of the likelihood of
diagnosis of gout
but with a loss of sensitivity (42%)
Löffler C et al. 2015

29. The DC sign alone is suitable for predicting crystal
arthropathies, but it cannot reliably distinguish gout
from CPPD in everyday clinical routine. Combining
PD and SUA levels increases the diagnostic value.

30. 1. 6 examiners  ↑ interobserver variability  ↑ inaccuracy,
2. Phagocytized urate crystals  diagnostic standard for
gout. Authors do not describe whether the presence of
extracellular urate crystals only was also considered
diagnostic for gout
3. Knee Joint + 10 1ST MTP single joint insufficient
accuracy for gout diagnosis,

31. Systematic bilateral scanning for hyperechoic deposits at the
radiocarpal joint, patellar tendon and triceps tendon, and DC sign
in 3 articular cartilages (1st MTP, talar, and 2nd MCP/femoral) 
↑ accuracy  sensitivity 85% and specificity 83%. On the other
hand , the sensitivity and specificity for DC sign at the femoral
condyle was 42% and 100%, respectively, and at the 1st MTP J
dorsal cartilage was 62% and 98%, respectively
Naredo E, et al 2014

32. Basic Calcium Phosphate Crystals

33. Hydroxyapatite is represented by the formula
Ca10(PO4)6(OH)2 and generally occurs in the
partially carbonate-substituted form. Octacalcium
phosphate (Ca8H2(PO4)6.5H2O) and tricalcium
phosphate (Ca3(PO4)2) also Present.

34. ↑ ↑ ↑ Reflection
Hyperechoic DEPOSITS
Acoustic shadowing

35. a arc-shaped, with clear
posterior acoustic shadow;
b fragmented, without
shadowing;
c nodular, with no shadow

36. Conclusion

37. 1. Understanding Chemistry and Histopathology of the
disease as well as Physics of ultrasound 
understanding and interpretation of ultrasound images
type of the crystals,
2. Gout  hyperechoic spots, DC, Tophi and erosions
3. CPPD  Calcifications of middle zone, Punctate pattern,
calcifications are parallel to tendon fascicles.

38. 4. BCC  Fragmented and Nodular (no Shadowing) or
arc like with acoustic shadowing,
5. TC  Mixed Crystal disease,
6. DC sign can’t differentiate between gout and CPPD,
7. Clinical picture + Lab + US (static & dynamic, PD,>1
joint /tendon)  ↑ accuracy of diagnosis,
8. Arthrocentesis is GOLD STANDARD