December 22, 2008 Leave a comment
Partial or complete ureteral replacement remains a challenge for the urologist. The maintenance of kidney function is the primary goal of this procedure. The crucial problem with ureteral replacement is that in most cases several surgical procedures and frequently radiotherapy have been performed beforehand, and kidney function is usually already impaired at the time of intervention. Therefore, standardized recommendations may not be applicable, and the approach must be tailored according to the individual situation.
Several ureteral substitutes have been proposed, including blood vessels, fallopian tubes, and the appendix. Nevertheless, all these tissues or organs and the corresponding procedures are correlated with a significant morbidity, including recurrent infection, stone, or stricture formation, with a worsening of kidney function in many patients. Because larger series have rarely been reported, the results and morbidity of the various procedures differ significantly.
Because partial or complete ureteral replacement with small bowel is always a secondary treatment, every attempt should be made to preserve as much ureteral length as possible. Antegrade and retrograde pyelography will usually provide sufficient information regarding the length and degree of the stricture, but in selected cases ureteroscopy may provide valuable information. In patients treated for malignant disease, tumor recurrence must be excluded by CAT scan or MRI. Kidney function needs to be examined by preoperative isotope scintigraphy to ensure it is appropriate because with severely decreased function, the results of ureteral reconstruction are poor. Furthermore, preoperative isotope scintigraphy provides a baseline for follow-up examinations after surgery.
INDICATIONS FOR SURGERY
Partial or complete ureteral replacement with small bowel is indicated as a second-line treatment after failure of ureter-sparing surgery.
Every attempt should be made to maintain the ureter. Depending on the length and location of the stricture, the preoperative evaluation should demonstrate whether ureter-sparing approaches are viable alternatives to ureteral replacement. Because of their relatively low morbidity, endoscopic procedures should be considered first. A success rate of only 50% to 70% with endoscopy necessitates further measures in a number of patients.
Autotransplantation carries several disadvantages and risks, especially after previous surgery and/or radiotherapy and impaired renal function. Although no prospective study addressing this question has been conducted, ureteral replacement with small bowel seems preferable in this patient population.
Bladder outlet obstruction is a contraindication for ureteral replacement with small bowel and, therefore, must be excluded. If necessary, urodynamic examination of the lower urinary tract should be performed. In patients with obstructive prostatic hyperplasia, prostatectomy should be performed before ureteral replacement. Preoperative bowel preparation should be performed as in patients undergoing bowel surgery for other urologic procedures . A nephrostomy tube is already in place in most patients or should be inserted during surgery.
Position and Incision
If both sides are affected, a midline incision or a right paramedian incision is recommended. If only one ureter is to be replaced, a lateral flank position (twist position) with the table flexed and the chest positioned at about a 60-degree angle to the table is preferable. Allow the pelvis to fall back. The incision starts between the 11th and 12th ribs, continues semiobliquely nearly to the midline, and ends as a paramedian incision to the os pubis. The peritoneum is opened, and the small bowel packed away.
For a right ureteral replacement, mobilize the cecum and divide the lateral attachments of the ascending colon . Mobilize the ascending colon as for an extensive retroperitoneal lymph node dissection. Mobilize the peritoneum from the bladder dome and the lateral aspect of the bladder. Carefully determine the length of intestine required for ureteral replacement.
Select an appropriate segment from the preterminal ileum. Consider adequate vascularization of the chosen segment . It is mandatory to select the sites of transection to permit a dissection deep enough for the proximal end to reach the renal pelvis and the laborial or distal end to reach the bladder. The bowel is divided, and the continuity restored, as described for the ileal conduit. The mesenteric defect is then closed with 3-0 vicryl to prevent internal herniation. The excised bowel segment is irrigated with saline solution until the effluent is clear.
The mesentery of the ascending colon is incised depending on the location of the mesentery of the ileal segment, and the ileum is passed into the retroperitoneal space. The ileal segment is then rotated to place the distal end near the bladder and the proximal end close to the renal pelvis or the ureter. The defect in the colonic mesentery is closed using 3-0 vicryl sutures. In this closure, it is important to avoid compression of the ileal mesenteric vessels.
Pyeloileal Anastomosis or Ileoureteral Anastomosis
In cases of partial ureteral replacement, the proximal opening of the ileal segment is closed with a running 3-0 chromic catgut suture. Before the anastomosis, the ureter is stented with a 6- to 9-Fr catheter held in place with a 4-0 catgut suture. The ileoureteral anastomosis of the spatulated ureter is performed end to side with a single-layer technique with either a running suture or interrupted sutures of 4-0 or 5-0 vicryl sutures.
For complete ureteral replacement, the proximal opening of the ileal segment is brought to the renal pelvis. The renal pelvis is opened widely to permit end-to-end anastomosis to the ileum. In case of a small renal pelvis, it may become necessary to taper the ileum by closing the proximal opening of the ileum partially on the antimesenteric side. The pyeloileal anastomosis is performed in a single layer with either a running suture or interrupted sutures of 3-0 or 4-0 chromic catgut. Because a nephrostomy tube is already in place, it is not necessary to stent the ileal ureter.
We prefer to perform ileocystostomy on the posterior bladder wall about 1 to 2 cm craniolaterally to the native ureteral orifice to avoid extensive angulation and possible obstruction of the ileum during bladder filling. The anastomosis is performed in a double-layered technique with a running mucosa-to-mucosa suture (4-0 vicryl) and interrupted seromuscular–detrusor muscle sutures of 3-0 vicryl . Except for the fixation of the mutual stent, vicryl may be replaced by chromic catgut.
Most reports on ureteral replacement with ileum are case reports including only a few patients. Because no larger contemporary series are available for review, the assessment of the outcome of this procedure is difficult.
No data are available regarding perioperative complications of ureteral replacement with ileum. It is assumed that the complications are similar to those observed after surgery for an ileal neobladder. In patients with partial replacement of the ureter, strictures at the ureteroileal anastomosis presumably occur at a similar frequency as in patients after an ileal conduit. Ileoureteral reflux is observed in 50% to 85% of the patients depending on whether the bladder is filling or emptying. The significance of this reflux is unknown.
Hyperchloremic metabolic acidosis requiring treatment should be anticipated in approximately 50% of patients. Careful follow-up examination including routine measurements of base excess, serum bicarbonate, and pH are mandatory.
This group of patients is certainly prone to urinary tract infections (UTI). In 30% to 100% of the patients, UTI will occur. Regular urinalysis and appropriate antibiotic treatment in cases of proven UTI are required.
The results of ureteral replacement with ileum are difficult to assess because this form of surgery is not standardized, and patient selection varies considerably between the different series. Furthermore, the objective goals of the procedure are not clearly defined. The values of BUN or serum creatinine that have been reported in some series are probably not sufficient to define the outcome in patients with bilateral kidneys. Dilation of the upper urinary tract is another parameter used in the literature. However, it is difficult to discriminate between persistent dilation despite reduction of ureteral obstruction and those cases in which dilation persists as a result of obstruction and/or reflux after surgery. To date, no reports including diuretic isotope scintigraphy have been published.
In the few studies with long-term results, a favorable outcome has been reported in up to 85% of the cases. This does not include patients with impaired renal function with serum creatinine levels greater than 2.0mg/dl. In this population, fewer than 50% will benefit from ureteral replacement.
In general, to avoid metabolic problems, the length of the ileal segment should be as short as possible. Hinman and Oppenheimer, however, have shown in the dog that an ileal segment greater than 18 cm will block the transmission of 20 to 30 cm H2O pressure. These experiments also form the basis for the introduction of a nontubularized ileal segment in modifications of the neobladder. Clinical reports on ureteral replacement with ileum apparently do not support this experimental observation, however, because cystoileal reflux and/or ileal–ureteral reflux can be observed in some patients at an intravesical pressure of only 3 to 8 cm H2O. It is questionable whether a pressure of less than 20 cm H2O can lead to damage to the upper urinary tract. So far, no clinical data including simultaneous measurement of intravesical and intrapelvic pressures are available. In addition, long-term results seen after ureteral replacement with ileum and experiences with the intestinal neobladder suggest that some protection of the upper urinary tract may be afforded by the ileal segment. We therefore prefer to use a bowel segment at least 15 cm in length.
In summary, ureteral replacement with ileum is a feasible technique that carries considerable perioperative and long-term morbidity and should therefore be considered only as a second-line treatment in selected patients.