Year : 2000 | Volume
: 16 | Issue : 2 | Page : 176--177
Choosing a single transanastomotic stent for pediatric pyeloplasty
Department of Pediatric Surgery, AIMS, New Delhi - 110 029, India
D K Gupta
Department of Pediatric Surgery, AIMS, New Delhi - 110 029
|How to cite this article:|
Gupta D K. Choosing a single transanastomotic stent for pediatric pyeloplasty.Indian J Urol 2000;16:176-177
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Gupta D K. Choosing a single transanastomotic stent for pediatric pyeloplasty. Indian J Urol [serial online] 2000 [cited 2023 Feb 4 ];16:176-177
Available from: https://www.indianjurol.com/text.asp?2000/16/2/176/22232
Ref: Detailed comments on the article on the Use of Infant Feeding Tube as an Alternative to Nephrostent in Pyeloplasty by S.S. Samaiyar et al, Varanasi (IJU 16 (1), pp. 67-68, 1999)
May I take the opportunity and submit detailed information on the choice and the use of a single transanastomotic stent in relation to the paper published in IJU, 1999. Various comments for choosing a single transanastomotic stents are:
1. Size of the tube: The authors have not mentioned the range or the mean age of the 15 patients treated with the use of a "uniform size 8 Fr." feeding tube for pyeloplasty. May be the patients were infants and children. While the 8Fr. stent may be quite thick for the neonates' and the infants' ureter, it is small (and quite often unable to drain the large volume of urine) in adults. The size of the stent to be used would vary with the size of the lumen of the ureter available at pyeloplasty. The size of the stent should always be smaller than the lumen of the ureter, allowing the free flow of urine from the pelvis to the ureter. A snugly fitting stent is more harmful at the anastomotic site causing edema, infection, suture disruption and a blockage to the urine flow.
2. Are the additional holes in the stent necessary?: It is a misconception that the urine from the pelvis would be drained only in the presence of the holes located in the part of the stent in the region of the renal pelvis. Secondly, I feel that the holes which are made in the stent by the needle (possibly by the hypodermic one in this series) would be too small to effectively drain the pelvis (the authors themselves have also experienced the same problem) even if they are many in number. Any attempt to create larger holes, specially if the holes are more than half the circumference in diameter, would have the risks of "fracture" of the stent while attempted removal, retaining the fragment inside the pelvis as a foreign body. A stent (like the suction catheter available with only an end hole) without any additional holes in the pelvis drains as effectively as the nephrostomy catheter, provided that neither it is too tight at the ureteropelvic junction nor it is too far down near the vesicoureteric junction.
3. The exit route of the stent: The prolonged obstruction coupled possibly with infection slowly damages the nephrons, the renal cortex and the renal parenchyma. Any additional trauma to the renal cortex with the stent traversing through it, would result in renal scar formation on healing, carrying a definite risk of future hypertension, albeit in small number of patients. This is completely preventable and the stent can safely be taken out of the renal pelvis (instead of through the cortex), either from the suture line or a separate oblique wound in the wall of the pelvis. The stent can then well be reinforced by absorbable sutures, if required. Also, there is no need for the stent to be taken out of a separate skin wound. A smaller sized stent can easily be taken out of the most lateral part of the wound, securing it firmly in the various suture planes with absorbable sutures.
4. Duration of the stent: The authors have kept the stent for 14 days following pyeloplasty. To me it is not required to be kept for such a long time. A stent is required in the immediate postoperative period to drain the urine, expedite healing process and support anastomosis. It also prevents kinks, provides patency and avoids synaechae formation across the neo ureteropelvic anastomosis. However, the medical grade PVC or even the silastic and the polyurethane tubes (J stents) are all notorious for complications in uro-surgery causing infection, bleeding, encrustation and persistent fistula formation, specially if kept for a longer duration.
In our experience, a stent kept across the neo-anastomosis for 4-5 days is quite sufficient and thereafter can be safely removed when the daily urine output decreases and the distal flow is established. A nephrostogram is not mandatory. A postpyeloplasty nephrostogram may rather introduce infection in the dilated system. Unless there is a specific indication, we feel stent should be removed within 4-5 days after pyeloplasty and should not be left for 14 days or so.
In view of the above, there is no disagreement about the choice of the use of a single transanastomotic stent following the pyeloplasty (in children as well as in adults). However, the choice of the size of a catheter, the route of its placement, the material of the catheter used and the need for the additional holes in the part of the stent to be placed in the renal pelvis require a few considerations and modifications to achieve trouble-free postpyeloplasty urinary drainage, without infection and renal scar formation.
It serves as good a purpose as a flexible feeding tube or any other costly J stent available in the market. The polyurethane material stents (J stents) have not become popular in the pediatric age-group as it is expensive and requires a second anesthesia and cystoscopy for its removal. Also, after some time the J stents become brittle in the presence of urine and there are case reports where the J stents have fractured while retrieving them cystoscopically.
During the period from 1993-97, we have used the suction catheter as a trans-pelviureteric stent. Suction catheters of various sizes are freely available in the operating rooms, are comparatively firm and unlike feeding tubes do not stretch easily, thus avoiding the kinks and curls. The tip is smooth and the hole is located end on. It provides perfect scaffold and support to the neo-anastomosis and drains the pelvis without the need for additional holes.
The PVC suction catheter (without any additional holes for draining the pelvis) is simple and cheap. When taken out through the renal pelvis (and not through the cortex) and the edge of the main wound, it produces neither a renal scar nor an external skin mark. It can be removed after 4-5 days when the distal urine flow is achieved. We have found this a much better alternative to the use of the flexible infant feeding tubes in more than 50 pediatric pyeloplasties.
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