Technique for Percutaneous Urinary Interventions in Renal Transplants

The standard preprocedural preparations for a PCN are instituted. When planning a percutaneous puncture, it is important to avoid entry into the peritoneum by staying lateral to the lateral border of the transplant and the skin sutures. Transperitoneal punctures are more likely if an upper polar access is used and if the puncture is medial to the skin incision. Real-time ultrasound is useful in directing puncture into an anterolateral calyx with a minimal number of punctures.

Although ultrasound is quite sensitive for detecting hydronephrosis, mild, non-obstructive fullness of the transplant collecting system, which may be merely related to denervation of renal transplants may be difficult to distinguish from fullness of the collecting system due to obstruction. Another cause for mild dilation of the collecting system is reflux through the UNC. Therefore, antegrade pyelography plays a crucial role in confirming the status of the transplant collecting system in patients with suspected obstruction or leak. This procedure confirms the presence of obstruction or leak and helps to localize its site. It may also identify the etiology.

Antegrade pyelography is performed using the previously described standard technique used for nontransplant nephrostomies. If a stricture or occlusion is found, both balloon dilation followed by stenting (188) and stenting alone (184,187) are treatment options. Bhagat et al. (187) used a 4mm balloon to facilitate placement of a stent in selected patients and used 6 to 10 French double-pigtail ureteral stents (8-10 cm long stents) in all patients. Fontaine et al. (188) balloon dilated all strictures with 5 mm to 8 mm balloons, prior to nephroureteral stent placement. Pappas et al. (184) reported on 13 patients, of whom eight had distal obstruction and four had UPJ or proximal ureteral obstructions. These authors dilated the stricture in only 7 of 12 patients (58%) prior to placement of 24 cm-long double-pigtail ureteral stents in all 12 patients, and the stents were left in place for a mean duration of 15 months. Our own preference (189) is to balloon dilate all ureteral strictures with 6 mm to 10 mm high-pressure balloons (to a pressure of 17 atmospheres) prior to stenting with a nephroureteral catheter. We use commercially available special-order catheters (Cook Inc., Bloomington, Indiana) that are 8 French to 10 French in diameter and have an 8 cm to 10 cm distance between the two pigtails. Only the proximal pigtail is self-retaining (as is the case with nephroureteral catheters used for ureteral stenting in native, nontransplant urinary tracts). Internalized stents reportedly have fewer infection complications because there is no external catheter, but percutaneous access is lost, precluding radiologic evaluation of the strictured segment. Stents were left indwelling without interval change for a mean duration of 15 months in one series (184) and up to two years in another series (187), without evidence of obstruction.

Surgical management of ureteral obstructions is required when the stricture cannot be traversed with a wire, the stricture does not respond to balloon dilation and stenting, or the radiographic findings strongly suggest extrinsic compression by vascular structures or the spermatic cord; however, graft survival appears to be higher in patients treated with ureteral stent placement as opposed to surgery (191).

Balloon dilation of transplant ureteral strictures has been reported to be effective in 40% to 78% of patients (184,187,189-195). Initial technical success in dilating the stricture does not translate into long-term success. Failure of balloon dilation becomes evident usually within weeks of the stent removal. Streem et al. (193) found that all failures presented within 12 months of dilation. Strictures that present early (within three months of surgery) have been reported by some to respond better to balloon dilation and stenting (187-189), but other series have not noted this to be the case (189). Early strictures reportedly respond in 62% to 100% of cases and late strictures (greater than three months) respond in 16% to 66% of cases (194). Endour-eterotomy, which involves incision of the stricture, has also been used for UNC strictures (195,196). The results and indications for endoureterotomy are still in evolution, with the reported series all consisting of only a few patients each.

Prolonged ureteral stenting alone may be effective in treating transplant uret-eral strictures (184,187). Bhagat et al. (187) reported that 69% (18 of 26) of early obstructions and 33% (5 of 15) of late obstructions (overall success rate of 57%— 25 of 44 patients) responded to a stenting period of an average of 75 days, and the failures were treated with either surgery or chronic stent placement. Pappas et al. (184) reported that 75% of their cases responded successfully.

Strictures that develop at the UNC site appear to respond better to balloon dilation than do strictures at other sites in the ureter (188). This may be related to the ischemic nature of strictures in the proximal and middle ureter, whereas strictures at the ureteral anastomotic site are related to either errors in surgical technique or periureteral fibrosis.

Ureteral leaks also occur most frequently at the UNC; Bhagat et al. (187) reported that 80% of leaks were at the UNC and 50% of leaks were associated with stenoses. Ureteral stenting is effective in promoting healing and resolution of the leak in 59% to 80% of cases (187,188). If ureteral leak persists, surgical repair is usually required.

The only complication that is unique to a transplant nephrostomy is intraperi-toneal leak of contrast due to inadvertent puncture of the peritoneum (187). This problem usually resolves spontaneously, without any adverse event. Because the patients are immunocompromised, special vigilance is required to avoid precipitating septicemia when percutaneous interventions are performed. Still, minor urinary tract infections can reportedly occur in as many as 38% of patients after the procedure (188).

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