Twinkling sign?

Recently, Andrulli et al. [1] published a study about twinkling artefacts. The authors suggest that one should not speak of ‘twinkling artefacts’ but rather of ‘twinkling signs’, as this phenomenon plays an important role in kidney stone diagnosis. Both twinkling artefacts [2] and urine jet have been identified for many years but little used for purposes of diagnosis. Unlike other countries, in Switzerland, these phenomena were introduced by Jürg Prim into the course catalogue of the learning objectives for abdominal sonography training as early as 2003.

In fact, the search for stones in the renal sinus and in the ureter is not easy. Previously, the sensitivity of ultrasonography to ureteral stones was low with only 19–37% reported [3]. Thanks to the twinkling artefact, kidney stone diagnosis has been greatly enhanced. In addition, many ureteral stones and also renal sinus stones have been discovered. Our prospective study [4] showed that, with the combined utilization of twinkling artefacts, modern equipment and indirect signs of a stone, sensitivity, comparable with CT, of 98.2% and specificity of 100% were achieved. More recent studies by Park et al. [5] achieved a sensitivity of 93 and 98.5%, respectively, and specificity of 95 and 100%, respectively. In the study by Park et al. [5], twinkling in 184 of 214 stones was detectable (86%).

Indirect signs of nephrolithiasis are important, and here, urine jet plays an important role. A normal value is two jets per ureter per minute. The measurements are carried out between 3 and 5 min. But the twinkling artefact arises not only from renal stones, it also exists in many other formations with hard echoes. For example, some of these formations include calcifying pancreatitis or colonic air. Because twinkling is not specific only to urethral stones, I think that we should continue to speak of twinkling artefacts, and not, despite its usefulness, of twinkling signs.

Conflict of interest statement. None declared.