Percutaneous internal ureteral stent placement: Review of technical issues and solutions in 50 consecutive cases

ClinicalRadiology (1994)49, 256-261

Percutaneous Internal Ureteral Stent Placement: Review of Technical Issues and Solutions in 50 Consecutive Cases D. S. K. LU, N. PAPANICOLAOU, M. G I R A R D , M. J. LEE and I. C. Y O D E R

Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA Fifty consecutive pereutaneous ureteral stent placements in 40 patients over 22~ years were reviewed. Thirty-seven of 50 cases were performed following failed retrograde stenting. Antegrade stenting failed in 2/37 (5%) cases of malignant obstruction, and 4/13 (31%) cases of benign ureteral disease. Causes of failure and common technical problems included poor angulation of the percutaneous track, tortuous dilated ureters, tight obstructions, wedging of stent assembly components due to high resistance, and difficulty in positioning of the proximal pigtail. Helpful technical modifications included mid-pole rather than lower pole calyceal access, urinary decompression prior to stenting, and the routine use of a peel-away sheath (success rate 23/24 placements with sheath vs 21/26 without sheath). Stent patency rates were 95% at 3 months and 54% at 6 months. With attention to technique and appropriate modifications, success rate of percutaneons stenting remained high in this series despite the large number of cases referred after retrograde stenting had failed. Lu, D.S.K., Papanicolaou, N., Girard, M., Lee, M.J. & Yoder, I.C, (1994). Clinical Radiology 49, 256-261. Percutaneous Internal Ureteral Stent Placement: Review of Technical Issues and Solutions in 50 Consecutive Cases

Accepted for Publication 29 September 1993

Antegrade internal stent placement is a well established technique for the treatment of malignant ureteral obstruction and a variety of benign ureteral diseases [117]. Recent advancements in stent designs have simplified this procedure and enabled a high technical success rate. Antegrade stenting usually is requested after failed cystoscopic retrograde stenting. It is not surprising, therefore, that despite improvements in stent design, percutaneous stent placement often remains technically challenging. It is the purpose of this paper to analyse our experience with antegrade ureteral stenting and identify the common and persistent technical problems as well as the modifications we used to bypass these obstacles.

P A T I E N T S AND M E T H O D S We attempted to percutaneously insert 50 ureteral stents in 40 consecutive patients over a 289 year period. There were 27 males and 13 females, ranging in age from 12 to 90 years (mean 62 years). Thirty-seven procedures (74%) followed failed retrograde stenting. All stents placed were similar in design and delivery. The assembly consisted of an 8 F double pigtail stent with a proximal suture, an inner stiffener and a pusher. The majority of the stents were made of Percuflex material and a minority Glidex (Medi-Tech, Watertown, MA, USA). The basic technique of stent insertion is published elsewhere [1-3]. Whether a fresh puncture or an existing nephrostomy track was used as access, a guide wire was manipulated down the ureter into the bladder or urinary diversion. The stent assembly was then delivered over an Correspondenceto: Nicholas Papanicolaou, Department of Radiology, Massachusetts General Hospital, Boston, MA 02114, USA.

exchange guide wire, and the distal and proximal pigtails released by disengaging the inner stiffener, pusher and the guide wire from the stent itself. The final step was to cut the proximal suture once the stent position was satisfactorily adjusted. Adjustments to this basic technique have helped us circumvent many technical difficulties, which we encountered in several cases. The following categorizes these problems and outlines the corresponding technical modifications which we have found useful. Suboptimal Percutaneous Access Poor angulation of the percutaneous track via a lower pole calyx during conversion o f a nephrostomy to internal stent o ften resulted in buckling of the wire within the renal pelvis, forming a loop (Fig. la). To prevent the loop from forming in the first place, we found the use of a curved C1 or C2 (Cobra) catheter to be helpful in negotiating the ureteropelvic junction. The subsequent use of an extrastiff guide wire and a peel-away sheath further prevented the loop from forming in the renal pelvis during stent delivery (Fig. 2). To avoid this problem altogether, we now choose a mid-pole or upper pole calyx for fresh punctures (Fig. lb). Tortuous Ureter In an obstructed system, the ureter often is elongated and tortuous in addition to being dilated. To negotiate difficult ureteral tortuosities, we have found the glide wire to be invaluable. The glide wire has a soft tip and a hydrophilic coating activated by contact with water, which substantially reduces friction and can slide through severe tortuosities. Even then, certain sharp kinks and bends could not be bypassed. In this situation, which

257

PERCUTANEOUS URETERAL STENT PLACEMENT

(a)

(b)

Fig. 2 - Use of sheath to prevent looping of wire and catheter within renal pelvis. (a) Loop of catheter in renal pelvis due to poor lower pole access. (b) Loop straightened and downward course of catheter and wire maintained by use of the peel-away sheath.

(a)

(b)

Fig. 1 - Example of suboptimal access. (a) Lower pole calyceal puncture. Because of the 180 ~ turn in order to go down the ureter, the wire or catheter forms a loop which tents the renal pelvis. (b) Mid-pole calyceal access. Note how the wire and catheter course down the ureter in a smooth curve, without looping within the renal pelvis.

occurred in two of our cases, we found delayed stenting after several days o f ureteral decompression with a nephrostomy tube helpful (Fig. 3).

Tight Obstruction Complete ureteral obstruction with no contrast outlining the strictured lumen often can be negotiated with an angled tip, torquable catheter and a glide wire. Even among the failed cases, only twice could the obstruction not be traversed by a guide wire. The real challenge is in the delivery of the stent over the guide wire. With a tight obstruction, when forward force is applied to the stent, the assembly naturally either goes through the obstruction or buckles at its weakest point. The latter usually occurs in the renal pelvis where the guide wire and stent assembly buckle and form a loop (Fig. la). Once a loop forms, any additional forward force on the stent is dissipated by expansion of the loop and tenting of the renal pelvis, instead of being transmitted to the distal end of the stent. To minimize this problem, we found the combination of an extra-stiff guide wire and a peel-away sheath for stent delivery to be the most useful, the additional support preventing formation of the pelvic loop. As previously noted, the further use of a mid- or upper pole calyx for access is preferable.

Stent Assembly Breakdown We have encountered several cases where either the pusher, inner stiffener or the guide wire have been wedged and there was difficulty in releasing the stent from the rest of the assembly components (Figs 4,5). All these cases resulted from advancing the stent against high resistance either from the percutaneous track, renal parenchyma or the stricture itself. In order to minimize this problem, we have since adopted routine use o f a 9 F peel-away sheath (Cook, Bloomington, IN, USA). We found the sheath to be instrumental in eliminating the resistance through the percutaneous track and renal parenchyma, as well as helping to prevent buckling of the stent at the entrance to the calyx or within the renal pelvis.

Difficult Positioning of Proximal Stent Pigtail Sometimes, we have encountered difficulty in properly releasing and positioning the proximal pigtail of the stent. One flaw in stent design is the inability of the operator to advance the stent after the proximal pigtail is released, though the stent could be pulled back by the suture thread. Another problem has arisen where, after the proximal pigtail has formed a coil and deemed to be in good position, cutting and then pulling out the suture may result in proximal misplacement of the stent (Fig. 6), often with the proximal pigtail caught in a calyx. Since we have begun to use the 9 F peel-away sheath routinely, this problem has been eliminated. The sheath provides a way to advance the stent even after the proximal pigtail is released, and prevents displacement of the stent when the suture is removed (Fig. 7). Furthermore, it facilitates the subsequent placement of a temporary nephrostomy tube at the end of the procedure.

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CLINICAL RADIOLOGY

(a)

(b)

(c)

Fig. 3 - Example of delayed stenting for tortuous and dilated ureters. (a) Acute ureteral obstruction with tortuous proximal ureter which could not be bypassed. A nephrostomy was left in for drainage. (b) A few days later, with decompression of the system, there was a decrease in the ureteral tor tuosity. (c) Ureteral tortuosity easily bypassed and stent delivered.

RESULTS Success and failure rates of stent insertion were determined. Follow-up was obtained to determine stent patency rates. End points for follow-up were patient death, elective stent removal, stent malfunction or last available medical record. Thirty-seven stent placements were performed for malignant ureteral obstruction and 13 for benign ureteral diseases. Retrograde cystoscopic stenting was first attempted but failed in 28/37 malignant and 9/13 benign cases. The causes of malignant and benign ureteral obstruction are shown in Tables 1 and 2. Thirty-five of 37 (95%) stent placements for malignant obstruction and nine of 13 (69%) placements for benign disease were successful. We have incorporated the use of a peel-away sheath for routine stenting for our last 24 cases, of which 23 were successful (96%), compared to 21/26 (81%) without the sheath. The one failed case despite use of the sheath was complicated by renal pelvic perforation and extravasation, where prolonged manipulation was deemed unwise. N o complication requiring surgery or transfusion was encountered. Antegrade stenting was not successful in six cases. The reasons for the failure are presented in Table 3. All except one case followed failed retrograde stenting, the exception being a patient with an ileal loop, who could not be endoscoped. In five of the six patients, the percutaneous track was established through a lower pole calyx, which

usually is not as optimal an access route as mid or upper pole calyces are for stent placement. In one patient, no wire could negotiate an extremely tortuous ureter. In another one, no wire could cross a complete obstruction. In three patients, a wire could be negotiated past the obstruction, but the stent could not follow. One of these three patients subsequently had a retrograde stent placed over the antegrade guide wire. In the sixth patient, there was resistance to stent advancement so that the pusher became wedged into the proximal end of the stent and could not be disengaged (Fig. 3). Even though the final result was adequate clinically (effectively an externalized stent), this was considered a failure of internal stenting. Follow-up was available in all except two o f the 44 successfully placed stents, and their length of follow-up is shown in Table 4. Four patients (four stents) were alive with their stents at the time of this report, 10 patients died (13 stents) with their stents and 15 patients (17 stents) had their stents removed or changed electively. Only eight stents were observed until they became blocked, with a mean patency time of 5 months. Three m o n t h patency rate was 20/21 (95%) and 6 month patency rate was 7/13 (54%). DISCUSSION Percutaneous insertion of a double pigtail ureteral stent has a well established role in the management of malig-

PERCUTANEOUS URETERAL STENT PLACEMENT

259

Fig. 4 Wedged stent. In this patient, even though the stent has bypassed the obstructing proximal ureteral stone (arrow) and reached the bladder, the proximal end is wedged into the pusher and the two cannot be disengaged. The pusher is left attached to the stent and served as an externalized extension (not easily seen on this radiograph because it is radiolucent). Note how the proximal pigtail did not form and has a crumpled appearance with a flared end (arrowhead) because the pusher is telescoped into it.

Fig. 6 - Example of suboptimal proximal pigtail position due to retraction of it during suture removal. Notice that the normal loop was not formed likely because it is caught within a calyx.

S

Fig. 5 - Illustration of wedging of stent components. In this example, the distal end of the plastic pusher is wedged into the proximal end o f the stent (arrowhead), with flaring of the proximal end of the stent, and narrowing of the distal end o f the pusher, which would also result in difficulty in disengaging the assembly from the introducer and guide wire.

nant ureteral obstruction and benign ureteral diseases. Experience with polyethylene, polyurethane and soft silicone stents has been previously reported [4-9]. Newer stents made of soft, biocompatible co-polymers such as Percuflex are now increasingly being used as they combine the softness of silicone rubber and ease of insertion of the stiffer polyethylene/polyurethane stents [ 10-12]. Early experience with these newer stents has been encouraging. Our overall success rate of 88% (44/50 attempts) is similar to most large series in the literature, ranging from 77% to 87% [6,8-10]. Technical success rate was not

reported by Mitty et al. in the only previous large series of Percuflex ureteral stents [11]. It is of interest that in our series, the primary failure rate for benign ureteral disease (31%) was higher compared to that reported in the literature, ranging from 11% to 18% [5,9]. This may be a reflection of the large number of impacted ureteral calculi we see in our practice. Despite the low failure rate in our series, the cases exemplify common, persistent technical difficulties encountered with stent placements. Failure to cross obstructions often is independent of stent material. Once the obstruction is crossed with a wire, often a glide wire, smooth advancement of a stent depends on severai factors: the tightness of the stricture, the angle of the percutaneous access, and the ability of the exchange wire to prevent buckling. I f the stricture is tight, advancement of any catheter may be difficult if the guide wire is too soft or if the percutaneous access is poorly angulated with respect to the ureter. Therefore it is important to use an extra-stiff guide wire for support, and to select as an entry site a mid or upper pole calyx in order to ensure a smooth curve to the ureter. However, often the request for a ureteral stent comes after a nephrostomy catheter is already in place, and most simple nephrostomies are performed through a lower pole calyx. In this situation, of course one must first try to place the stent through the existing track. To give additional support to stent advancement and prevent buckling of wire or stent assembly in the renal pelvis, we have found the peel-away sheath to

260

CLINICAL RADIOLOGY Table 3 - Reason for failure o f stenting

i

Indication

Reason for failure

I Distal ureteral stone

Complete obstruction, wire could not cross

2 Bladder carcinoma, obstructed UVJ

Tortuous ureter, wire could not pass

3 Cervical carcinoma, obstructed UVJ

Tight UVJ, wire crossed but not stent. No prolonged manipulation due to excessive urine extravasation

4 Distal ureteral stricture

Tight stricture, wire crossed but not stent; retrograde stenting subsequently successful

5 Stricture+perforation

Tight ileal loop anastomotic stricture, wire crossed but not stent

6 Proximal ureteral stone

High resistance, wedging of stent assembly components

UVJ, Ureterovesical junction.

Fig. 7 - Illustration of facilitated proximal pigtail positioning using the peel-away sheath. Top left: Stent delivered through peel-away sheath. The introducer has already been removed. Top right: The guide wire and pusher are removed, releasing the proximal stent pigtail. Note that the pigtail is released too distal. Note also that the suture thread is still attached to the stent and exits through the sheath. Bottom left: The suture is pulled so that the proximal pigtail is pulled back into the renal pelvis and allowed to form. The suture is then cut at one limb and removed. Notice how the sheath can prevent the pigtail from being pulled back into a calyx or the percutaneous tract. Bottom right: After suture removal, a temporary nephrostomy can be easily placed through the sheath.

Table 1 - Antegrade ureteral stent placement for malignant obstruction

Malignancy Cervical Ovarian Vaginal Bladder Prostate Colon Total (%)

Success 5 3 1 9 8 9 35 (95)

Failure

Total

1 0 0 1 0 0

6 3 1 10 8 9

2 (5)

37

Table 2 - Antegrade ureteral stenting for benign disease

Indications

Success

Failure

Stone Stricture Perforation/fistula

5 2* 2

2 2* 0

Total (%)

9 (69)

4 (31)

Total 7 4 2 13

* Both successfully stented strictures and one of the failed cases were associated with ureteral perforations as well.

be very helpful. In addition, the sheath eliminated resistance to stent advancement through the percutaneous track and renal parenchyma. The use of a sheath to facilitate stent delivery is not new [13-15]. It was practically a necessity in placing the soft silicone stents [14], and Mitty et al. have found it useful in placing even the more rigid polyethylene and polyureth, ane stents [4,9]. However, its use was not reported in Mitty's recent series on Percuflex stents [11] and was deemed unnecessary for the placement of another stent made of a similar polymer, C-flex (Cook, Bloomington, IN) [10]. We believe that in dealing with difficult, tight obstructions, and despite the use of newer stent designs and materials, the sheath is invaluable in ensuring smooth stent delivery. O f the five failed cases in our series without use of the sheath, two were caused by inability to advance the stent despite crossing the obstruction with a wire, and in another one a stent was placed across the obstruction but could not be separated from its pusher. These failures represent potential situations where the sheath could have helped. Breakdown of the stent assembly due to excessive friction in stent advancement, though relatively uncommon, has had consequences. It resulted in one failure and at least several stents had to be replaced at the time of the procedure. The routine use of the peel-away sheath has virtually eliminated such problems. Tortuous ureters are commonly encountered during ureteral stenting. Relieving the obstruction with a simple nephrostomy catheter over a period of several days m a y reduce the degree of ureteral tortuosity and facilitate subsequent stent placement. Others have also recommended delayed stenting in cases where the initial puncture was traumatic or in cases of urinary tract infection [1,4]. Problems with positioning of the proximal stent pigtail had been noted by several authors [11,17]. Having the proximal pigtail caught in a calyx may result in blockage of the proximal stent side holes. Mitty et al. proposed the use of a dilator advanced over the suture in dealing with this problem [11]. We achieved the same result with the peel-away sheath, which we already had placed because of the m a n y other advantages it offered. Finally, in the few instances where the wire only can be placed through the obstructing lesion, subsequent stenting may be facilitated by transurethral retrieval of the

261

PERCUTANEOUS URETERAL STENT PLACEMENT Table 4 - Follow-up of successfully steatetl ureters* Death No. of cases

13

Follow-up time Range Mean S.D.

ld-40w 11.8w 10.5W

Still functioning 4

2w 46w 28.8w 18.8w

Elective removal or change 17

lw 25w 9.1w 7.9w

Blockage 8

5d-42w t 20. lw 13.1W

* T w o c a s e s l o s t t o ~11ow-up, availablein42/44cases. 3 month patencyrate:20/21(95%);6 month paten~ rate:7/13(54%). ~5d, 14w, 14w, 16w, 18w, 20w, 36w, 42w.

wire and either antegrade or retrograde insertion of the stent by controlling both ends of the wire. In summary, antegrade internal ureteral stent placement despite use of new stent materials and designs, can be technically difficult. Nevertheless, success rate of percutaneous stenting in this population remained high with attention to technique and judicious use of technical refinements. The routine use of a peel-away sheath was found to be the most helpful technical adjustment in facilitating stent placement. REFERENCES

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