Double-pigtail stents are frequently implanted in urological practice, to drain urine. The PSS described here uses the same mode of drainage in patients with obstructions. Whether the obstruction is due to a stone, an ureteropelvic junction syndrome, or ureteral stenosis, the upper, unmodified part of the stent facilitates the passage of urine around the obstacle. In our view, if the obstruction is located in the upper part of the ureter, the rest of the ureter is likely to be healthy and does not require drainage with a stent. The part of the stent in the bladder is, thus, of no use in such conditions, and its presence may provoke secondary effects. It has been suggested that pelvic symptoms could be decreased by reducing the amount of material in the bladder . The replacement of the bladder loop with a fine suture results in the presence of only tiny amounts of material in the bladder. Only the suture should cross the junction between the ureter and the bladder and float in the bladder itself (Fig. 2). The replacement of the lower part of the stent with a suture, resulting in the absence of an internal channel, probably also limits renal reflux.
Stents of several sizes, forms, and compositions have been studied, with the aim of reducing these symptoms. A short bladder loop seems to be preferable to a long loop extending throughout the bladder [7, 8]. The replacement of the bladder loop by a more flexible loop has no effect [9, 10]. Decreasing the diameter of the stent from 6 to 4.8F also has no effect . The beneficial effects or replacing the bladder loop by a collection of loop [3, 11] or by a thinned tail with a diameter of 3F [3, 12] remains a matter of debate.
Joshi et al.  obtained a score of 14.9 for the control group without stent. We obtained a score of 15.3 for such patients. Patients with a double-pigtail stent had urinary symptom scores of about 28 . This score was about 30 in a subsequent study of 116 patients . Damiano, Gianarini, and Davenport reported scores of about 27, 30, and 32, respectively [8, 10, 13]. We obtained a score of 35.2 for such patients. The score of our control group is 33.3 and was not significantly different than group 1 at baseline. The PSS decreased the total score from 35.2 to about 23, and this results confirm those of our retrospective study . Few studies have reported a significant decrease in urinary symptoms. In a meta-analysis, Lamb noted that alpha-blockers decreased scores . Kawahara  reported that the Polaris Loop® caused fewer symptoms in a group of 25 patients, but this was not confirmed in the series reported by Lingeman . Lee  found that correct stent positioning was more important than drug prescription.
The urinary and pain scores linked to the PSS were not significantly different for the patients of the two groups. Thus, the scores for group 1 do not seem to be the consequence of excessive enthusiasm for the PSS following poor tolerance of the double-pigtail stent.
Despite the clear improvement observed with PSS, the patients still had symptoms statistically different from their normal state. It seems that some symptoms decrease with time (dysuria, hematuria), but the general tolerance remains unchanged . However, about 9 months are required to observe a significant decrease in urinary symptoms . Even with PSS, duration of stenting must be as short as possible.
The stent is implanted to ensure the correct drainage of urine. The drainage mediated by the double-pigtail stent has been described previously. In normal ureters, the urine passes between the stent and the ureter wall, rarely through the holes. In ureters that are compromised or have a reduced diameter, the urine passes through the holes and the internal channel. The bladder loop seems to play no role in urine flow . Finally, the diameter of the stent (7 or 3F) has no effect on the efficacy of urine flow . In cases in which the lower ureter is healthy, we can confirm the normal flow of urine around the PSS.
Three of the PSS had to be withdrawn under ureteroscopy, because the sutures were cut too short and had migrated into the ureter. In these three cases, the PSS gave effective renal drainage. Stent removal through the ureter was easy without the further enlargement of meatus. Following these observations, in male patients, we keep a long suture so that the PSS length is 30 cm. In women, we cut the sutures at the urethral meatus. However, we believe that the obstruction must be bypassed by a segment of rigid stent and not by the suture. At the beginning of our experience, we have observed one migration of the suture into the ureter when the obstruction was bypassed by the suture only. If the ureter is healthy, sutures have not been observed to migrate up the ureter.
We felt that it was important to create a device having a perfect profile. It is possible that a straight segment of the ureter better tolerates the stent section and ureteral irritation in the region below the tail induces flank pain. PSS without the profiled tail has been used since December 2010 and has greatly reduced bladder symptoms. But frequent anterior flank discomfort seemed to be due to irritation caused by the lower part of the stent, which was sectioned manually and was unmodified. Because of flank pain, we rarely used this stent for 2 years. In 1994, Ponsot  and, in 1995, Dauleh  described a new stent prototype respectively in eight and three patients. The lower loop was replaced by a fine strong nylon loop to increase bladder tolerance  or prevent natural anti-reflux . But no further study was published.
In December 2012, since the creation of the sculpted and profiled tail, flank tolerance seems to have been improved. Ureteral irritation in the region below the tail may be milder than that in the unmodified section. The thinning of the lower end of the device seems to limit the snagging of the stent during breathing movements (Fig. 1c). Industrial manufacturers will be required to produce such a device. The suture could then be integrated into the stent, emerging at the extreme end of the tail. In this way, stent tolerance might be improved.
We developed the PSS as a means of decreasing urinary symptoms, but we discovered fortuitously that it had other surprising properties, probably due to the simple presence of the sutures in the ureter.
Firstly, about 1 month after PSS implantation, we observed in all cases of ureteroscopy clear dilation of the ureter intubated with the sutures (Fig. 3). It has been showed that preoperative stenting is effective for dilation of the ureter in preparation for ureteroscopy [21, 22] and insertion of an ureteral access sheath . Three weeks seemed sufficient for dilation . With the PSS, no patient required active dilation of the ureteral meatus at ureteroscopy. The prior implantation of a PSS could be used to prepare the ureter for the insertion of a sheath for flexible ureteroscopy without excessive discomfort. This could facilitate the introduction of a large ureteral access sheath (14/16F) for ureteroscopic treatment of large stone . We believe that dilation was probably induced by the sutures. Ureteroscopy, fluoroscopic, and CT scan imaging allowed measuring the degree of dilation (Fig. 4). To clarify our endoscopic observations, we measured the diameters of the pelvis and the ureter drained by PSS and we compared them with the diameters of the same contralateral segments. Table 3 shows the results for 35 patients of this study with short PSS and only proximal stone.
Secondly, after extracorporeal shockwave lithotripsy, the stone fragments gradually slid down the PSS sutures, without renal colic. Sutures behaves like a “stone’s toboggan” (Fig. 5). Ureteral dilation might accelerate the removal of stone fragments.
We believe that the use of a double-pigtail stent should no longer be considered the only way to drain the ureter. Instead, the form of the stent should depend on the patient’s disease. For example, in cases of non-obstructive kidney stones suitable for treatment by extracorporeal shockwave lithotripsy, we now use a stent reduced to a suture attached to a simple renal pigtail .