Current Insights on Urinary Leak in Renal Transplantation

Kidney transplantation is the standard of treatment for end stage renal disease [1]. It is a major undertaking in a state of end stage renal disease which leads to myriad of physiological and metabolic derangements in the body. With advancement in medical science and technology along with the better understanding of immunology, immunosuppressive therapy and surgical technique, overall medical and surgical complications of renal transplantations have dwindled down. Urological complications, which mostly rely on surgical techniques of graft retrieval and transplantation still occur and have been known to result in considerable morbidity and even mortality. Current literature shows wide variation in incidence of urological complications occurring in 3.4-14.1% out of which urine leaks have been observed in1-8.9% [2-5].

Urinary leak in renal transplant occurs as a consequence of compromised ureteral vascularity or from a technical error during construction of ureterocystoneostomy, the latter typically developing within the first 72 hours posttransplant [6]. The vascular supply to the ureter from the renal pedicle is tenuous and may be easily damaged during kidney harvesting. Technical causes during graft retrieval include direct surgical trauma to the ureter or to the golden triangle which contains important arterial branch supplying renal pelvis and ureter [7]. Sometimes tiny accessory renal arteries supplying lower pole may be severed resulting in devascularisation of ureter. Presence of multiple renal arteries has shown to be an independent risk factor for urological complications [8]. Similarly, urine leak may be brought about by technical errors which may occur during ureterocystoneostomy such as tunnel hematoma, distal stripping of the blood supply, improper ureteral and bladder anastomotic technique, undue tension created by the short ureter and or injury to renal pelvis during ureteric stent placement [9]. As most of the surgeons apply an extravesical ureteroneocystostomy technique, the shorter ureter decreases likelihood of ischemia, and a limited cystostomy rarely leads to urinary extravasation from the bladder [10-13]. Two cases of leakage have been reported through the anterior cystotomy and both required resuturing of the bladder rent [14]. Bladder outlet obstruction due to blocked catheter and defunctionalized bladder have been shown to be postoperative risk factors for urine leak. Calycealurine leak due to injury to polar artery and infarction of renal parenchymahas been described in literature [8,15]. The vesicouretreic anastomosis was the commonest site of leak and theureteric ischemia was found to be the major cause of urine leak [16].

Cochrane database of systemic review has shown that routine prophylactic stenting reduces the incidence of major urological complications in kidney transplant recipients with the incidence of major urological complications ranging between 0-4% in stented patients (median 1.0%) and 0-17.3% (median 7.0 %) in the non-stented patients [17]. Nie et al. [18] reported thatureteroureterostomy and ureterocystoneostomy had similar incidences of urological complications with an apparent decrease in incidences of urine leakage after ureteroureterostomy [18].

Clinical presentation and investigation

Urine leak may present with decreased urine output and increased drain fluid immediate postoperatively. The drain fluid creatinine, urea and potassium which are well above the serum level or approximately equal to urine is consistent with urine and distinguish it from lymphatic and ascitic fluid [19]. Flore-Gama et al. reported that the postoperative drain represented a six-times higher possibility of urinary leak if the draincreatinine was six times higher than the plasma or the urine creatinine was less than three fold the drain creatinine [20]. This ratio may not hold true in those with low creatinine clearance rate where urine creatinine nears plasma creatinine. The volume of drain and urine output correlate with the severity of urine leakage. Late postoperatively, if drain has already been removed or if it is not functioning, patient may present with fever, pain and swelling at the graft site, lower abdomen or scrotum, urine leakage from wound site or even urosepsis. Large urinoma may compress graft ureter or renal vessels leading to renal dysfunction. It may be difficult to distinguish the signs and symptoms of urinary extravasation from those of rejection or obstructive uropathy. Systemic reabsorption of extravasated urine may elevateserum creatinine and simulate urinary obstruction. Ultrasound and CT scan aid in the early and definitive diagnosis of perigraft collection [21]. CT urography in the presence of good graft function or T2 magnetic resonance urography in presence of renal insufficiency can detect urine leak from collecting system, ureter or anastomotic site. Urinoma are homogenous and anechoic in early phase in ultrasound and may become septated with time due to infection. The biochemical analysis of aspirated fluid rich in creatinine distinguishes urinoma from lymphocele. Though not specific for a leakage, sonography is a sensitive tool for suggesting the possibility of leakage [22]. Single photon emission computed tomogram (SPECT) /CT images and magnetic resonance urography are very helpful and valuable to evaluate the anatomical relationships exactly [23,24]. Other investigations include isotope renal scanning which can show nuclear contrast extravasation and cystography which can delineate contrast extravasation from the site of cystotomy or anastomotic dehiscence [25]. Scintigraphic detection of urine leak in cases of poor renal functionmay be limited by poor excretion of the radionuclide [26].

Management

Patients presenting with a urine leak following removal of Foley catheter are initially managed with placement of a Foleycatheter. For urine leak following transplant with Foley catheter needs percutaneous nephrostomy tube to diverturine away from the region of extravasation. The extent and location of urine leak can be determined by antegrade pyelogram. A low volume leak at anastomotic site can be managed conservatively which requires maximal decompression with a nephrostomy tube, ureteral stent and bladder catheter. An overall success rate of 11.1- 87 % was reported with endourological management at a mean follow-up of 35 months (range 24-67 months) [14,27-29]. The presence of contrast medium flow into the bladder was a major prognostic factor for the outcome of the fistula [6]. Nephrostomy tube and Foley catheter can be removed once the leak subsides but the ureteral stent is removed 4-6 weeks later. Close monitoring for secondary ureteric stricture is still needed after stent removal. Fluid collections, if cause extrinsic ureteral obstruction or get infected, need urgent percutaneous drainage. The aspirated fluid should be examined for total cell count, gram stain, culture, creatinine and triglyceride. An extensive urine leak or the leak failing conservative management needs early exploration. The ischemic ureter should be resected till healthy and vascular segment is reached and the large defect may need Psoas hitch or Boari flap for ureterocystoneostomy or even pyelocystostomy if ureter is totally ischemic [14,30]. Use of methylene blue through nephrostomy tube or antegrade ureteric stenting prior to surgery may help find the graft ureter intraoperatively [31]. The healthy ureter of the transplant kidney can also be anastomosed to native ureter and even ileal substitution has been done for extensive necrosis of ureter and renal pelvis [32- 34]. Other techniques mentioned in literature were anastomosis with contralateral native ureter for absence of ipsilateral ureter and anastomosis with ileal conduit for absence of functional bladder [31]. Surgical repair has been successful in majority of cases with recurrence occurring in upto 23% of the cases [35]. A study by Karam et al. reported that ureteral necrosis did not affect the 10- year patient and graft survival [36]. Similar finding was shown by Berli et al. [31] who found equivalent graft survival rate when compared with those without urological complications. Mortality in one of the studies has been reported to be 6.4% [32]. Use of artificial ureters (pyelovesical bypass graft) have been reported after failed endourologic or open management of ureteral strictures after renal transplantation [37].

Urine leak is a common urological complication encountered in renal transplantation. With good surgical technique, most of the urological complications can be avoided. Sound judgment of clinical findings, imaging and biochemical findings of drained or collected fluid is a must for timely identification. Optimal endourological or surgical management of urine leak reduces not only morbidity but prevents graft loss as well.

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