| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Case Report |
1
Service de Radiologie, Groupe Hospitalier Pellegrin, Place
Amélie
Raba-Léon, 33076 Bordeaux Cedex, France.
2
Service d'Urologie, Groupe Hospitalier Pellegrin, 33076 Bordeaux Cedex,
France.
Received July 19, 2000;
accepted after revision November 11, 2000.
Address correspondence to N. Grenier.
Introduction
 Top Introduction ObservationsDiscussionReferences |
|---|
To date, diagnosis of encrustation of ureteral stents has been based only on unenhanced radiographs of the abdomen. Using color-flow Doppler sonography, a color artifact called the twinkling artifact has been described behind calcifications and, in particular, behind urinary stones [5]. This artifact, which results from complex physical mechanisms, is related to the irregularity of the surface of the calcifications [6]. It appears as a random color encoding behind the stones, in the region where shadowing would be expected on gray-scale images.
We present two cases of stent encrustation detected on color-flow Doppler sonography.
|
TopIntroductionObservationsDiscussionReferences |
|---|
|
|
|
|
|
|
Second Patient
A 40-year-old woman underwent a right ureteral pure silicone stent
placement for a ureterolithiasis of the lower ureter, requiring urologic
treatment during her fourth month of pregnancy. Two months later she presented
with hematuria without pain. Scans obtained with B-mode sonography of the
bladder did not show any abnormality of the lower end of the stent. Its upper
end could not be identified in the absence of dilatation of the upper
cavities. On color Doppler sonography, a twinkling artifact was present at the
lower intravesical end of the stent (Fig.
2A). This artifact was not massive, as in the first patient, but
followed the course of the stent itself. Careful examination of the left
pelvis with high-velocity scale showed a small artifact at the ureteropelvic
junction. Unenhanced radiographic images confirmed the low position of the
stent and showed only a thin calcified rim around both ends
(Fig. 2B). The stent was
withdrawn using a pulsed-dye laser. Chemical analysis of stone fragments
showed calcium oxalate.
|
|
|
TopIntroductionObservationsDiscussionReferences |
|---|
Follow-up of stents by unenhanced radiography is recommended; even so, the encrustation phenomenon can be missed in its early phase. The second case reported here shows how difficult it can be to identify the thin calcified rim around the stent at the beginning of the phenomenon.
Encrustation usually occurs at the extremities of the stent. The lower extremity is easily identified within the bladder, because urine provides a useful contrast for identification of the twinkling artifact. The upper extremity may be more difficult to see within the pelvis if it is not dilated. In such a setting, differentiation between the hilar renal vessels and the twinkling artifact requires an increase in the Doppler pulse repetition frequency. This has no effect on the artifact [5] but decreases the Doppler signal. However, identification of encrustation at the lower end of the stent within the bladder should be sufficient, because it usually occurs symmetrically.
The artifact is frequently observed behind calcifications but is not constant. Rahmouni et al. [5] showed that it is generated by a random, strongly reflecting medium with a rough interface composed of individual reflectors. A relationship was shown in vitro between the surface of urinary stones and the presence of a twinkling artifact [6]. In most cases it appears when the surfaces of calculi are irregular (crystalline or mottled). In the case of encrustation, it is probable that a calcium phosphate or a calcium oxalate deposit makes the surface of the stent irregular or crystalline, thus creating the artifact. The second case shows how striking this artifact is within the bladder compared with the thin calcic rim visible with unenhanced radiography.
In summary, identification of encrustation of ureteral stents, one of the main complications of these materials, is possible with color-flow Doppler sonography in the presence of a twinkling artifact. The exact impact of sonographic follow-up on the urologic management of indwelling ureteral stents still remains to be defined.
|
TopIntroductionObservationsDiscussionReferences |
|---|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  E. A. O'Flynn and P. S. Sidhu The Sonographic Twinkling Artifact in Testicular Calcification J. Ultrasound Med., April 1, 2009; 28(4): 515 - 517. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Tchelepi and P. W. Ralls Color Comet-Tail Artifact: Clinical Applications Am. J. Roentgenol., January 1, 2009; 192(1): 11 - 18. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. J. Jeon and S. E. Yoon Color Doppler Twinkling Artifact in Hepatic Bile Duct Hamartomas (von Meyenburg Complexes). J. Ultrasound Med., March 1, 2006; 25(3): 399 - 402. [Full Text] [PDF]
|
|
|
|
|
|
E. Ghersin, M. Soudack, and D. Gaitini Twinkling Artifact in Gallbladder Adenomyomatosis J. Ultrasound Med., February 1, 2003; 22(2): 229 - 231. [Full Text] [PDF]
|
|
|
|
|
|
A. Kamaya, T. Tuthill, and J. M. Rubin Twinkling Artifact on Color Doppler Sonography: Dependence on Machine Parameters and Underlying Cause Am. J. Roentgenol., January 1, 2003; 180(1): 215 - 222. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Ustymowicz, J. Krejza, and Z. Mariak Twinkling Artifact in Color Doppler Imaging of the Orbit J. Ultrasound Med., May 1, 2002; 21(5): 559 - 563. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
