EXPERIMENTAL AND CLINICAL TRANSPLANTATION

Although they are not common, urologic complications after renal transplant are associated with risk of graft loss. Fluid collection during the postoperative period can be caused by urine leak or lymph leak of seroma. Biochemical analysis of the drained liquid is essential and should be compared with a concomitant serum sample. Surgical exploration is indicated if suspected urine leak is significant. Reimplantation of the ureter to the bladder can be challenging if there is extensive ureteral necrosis due to compromised vascularization.

Key words : Diagnosis, Kidney transplant, Treatment, Urinoma, Urologic complication

Complications after renal transplant can be due to either medical or surgical reasons. Among early com-plications, surgical causes are significant, although they are less frequent than medical or immunologic causes. Delayed graft function is a common but nonspecifically important clinical problem.

Fluid collection during the postoperative period can be caused by urine leak or lymph leak of seroma. In addition to clinical features, radiologic imaging can play a key role in ascertaining whether increased drainage fluid is because of urine leak or because of other causes in the posttransplant period.^1-3 Biochemical analysis of the drained liquid is essential and should be compared with a concomitant serum sample. In this review, we allude to various causes of increased fluid collection after kidney transplant, discuss different clinical presentations of urinoma, and describe an evidence-based management plan according to the leak source, anastomosis type, and the evolution of urine leak.

Our example patient is a 28-year-old male who underwent a kidney transplant from his brother with primary function. During the first 72 hours after transplant, the patient presented with increased drainage. Biochemical analysis of the drain showed high creatinine (16 000 μmol/L) and potassium levels (28 mmol/L) on aspirate fluid compared with a simultaneous analysis of a serum sample (creatinine of 416 μmol/L and serum potassium of 5.1 mmol/L).

Causes of Fluid Collection After Kidney Transplant

Productive drainage after kidney transplant can be associated with hemorrhage, lymphocele, perinephric abscesses, or urologic complications.^4,5

Hemorrhage
Anticoagulation and antiplatelets increase the risk of bleeding after kidney transplant.⁶ In the most obvious form of presentation, the diagnosis is evident because of a high amount of drain output of blood associated with signs of shock (a combination of tachypnea, hypotension, and tachycardia). In the immediate posttransplant period, a stable hemog-lobin level or lack of clinical swelling does not exclude this diagnosis. Ultrasonography may show hematoma early after transplant. An urgent exploration is required even if there is a doubt that delayed graft function is related to bleeding. Nevertheless, the clinical presentation can be less obvious especially as the drain can be obstructed by blood clots and the hemoglobin drop can be minimal.^3,4 If there is doubt, an urgent surgical exploration is a sensible approach.^4,5

Urinoma
The prevalence of urine leaks after kidney transplant is about 2% to 6%.⁷ Urine leak is considered to be less common in patients whose ureterovesical anastomosis has been conducted with use of an indwelling double J ureteric stent.⁸ Urine leak can occur during the immediate posttransplant period or later. Urinoma manifests as increased drainage, delayed graft function, or wound leakage. Similar to our patient, biochemical analysis of the drained liquid will show high creatinine and potassium levels on drained or aspirated fluid compared with a concomitant serum sample. In contrast, if the biochemistry of the drained liquid is comparable to serum, then it would indicate that the collection is either lymphocele or seroma.

Lymphocele
Lymphocele is a collection of lymph around the kidney, and it can be evident because of increased drain output. The incidence varies from 1% to 15%.^1,4 Lymphocele, even if large, could be asymptomatic when away from helium and the graft is not compressing the ureter. Lymphoceles can cause delayed graft function and decreased urine output if associated with ureteral obstruction. Ureter obstruction can be visualized with ultrasonography with pelvicaliceal dilatation. For lymphoceles that are not causing hydronephrosis and not associated with graft dysfunction, intervention is not indicated.^2,5,8 In other circumstances, it can be difficult to distinguish mixed urinoma and lymphocele if previous imaging showed fluid collection attributed to lymphocele. Biochemical analyses or collection analyses can help in diagnosis. High creatinine and potassium levels on drained or aspirated fluid are associated with urinoma.^3,8

Perinephric abscesses
Abscesses can be a complication of lymphocele, hematoma, or urinoma. Aspirate fluid should be sent for gram stain and cultured to aid in detection.³ Clinical, biologic, and imaging features of the suggested diagnostics are detailed in Table 1.

Approach for Patients With Urine Leak

Urologic complications are common after kidney transplant, but, compared with vascular com-plications, they are not as responsible for graft loss. Most urologic complications occur during the first 2 weeks after transplant. In most cases, leaks occur in the anastomotic region.⁴

For leaks that occur 1 day after surgery, the reason is technical error.8 Those that occur later (1-2 wk after surgery) are caused by ureteral necrosis. It is essential to eliminate first an obstruction resulting from a blocked catheter, which can lead to perforation or release of anastomosis.^9,10 The site of the urinary leak is often at the ureteral anastomosis and rarely due to a caliceal leak or to bladder perforation. The cause of ureteral leak can be either related to technical failure (ureteric kinking or suture dehiscence) or to ureteric ischemia^.11,12

In an investigation by Nie and associates,¹¹ the most common cause of urinary fistula was ureteral necrosis. Excessive dissection of periureteric tissue and use of a too long ureter are common causes of ureteric necrosis. As stated above, technical failures will be apparent during the first few days after transplant, with severe rejection affecting the ureter. Ureteric necrosis can be secondary to thrombosis or ligation of a lower polar arterial branch. An anastomotic pyeloureteral leak can be related to a malpositioned double J stent that may have perforated through the pelvis of the transplanted kidney.^4,10Bladder leak can be due to bladder wall dehiscence. A urinary leak can be also secondary to bladder retention as a result of blocked transurethral catheter.^3,5 A caliceal leak can be due to a localized renal infarction by ligation of a polar artery.¹³

Clinical Features

A key clinical finding of urine leak is excessive liquid drain output during the early postoperative period. Other leading clinical findings include one or more of the following: decreased urine output, wound fluid drainage, delayed graft function, and pain over the graft. Clinical examination can reveal swelling over the kidney graft site and of the ipsilateral lower extremity. Double J stents removed during the early postoperative period rather than the usual 6 weeks after transplant can lead to urine leakage.^2,3 The clinical presentation can have a more insidious onset because of confounding factors (preexisting seroma, limited drainage fluid related to other causes of delayed graft function). Infection of nonevacuated urinoma can manifest as a perinephric abscess.³ Table 2 shows the clinical and therapeutic features according to the mechanisms of urine leak.

Biological features of urine leaks
A comparison of the drained liquid versus a simultaneous serum sample is essential to discriminate between urinoma and lymphocele. With urinomas, the drained or aspirated fluids show high creatinine and potassium levels versus that shown in serum samples.

Imaging features of urine leaks
Ultrasonography is helpful for establishing urinoma diagnosis. In normal bladder, urinomas appear as well-defined anechoic collections without septations, unless infected or mixed with blood (echoic collection with septations). Urinomas can rapidly increase in size. The leak may be extraperitoneal or intraperitoneal.^10,12 Ultrasonography will allow measurement and monitoring of the collection area. Hydronephrosis can be a consequence of high volume urinoma or a cause. In fact, the obstruction can be associated with urine extravasation.

Computed tomography scans can show an isodense collection area for urinary tract fluid (Figure 1). Ultrasonography and computed tomo-graphy can both show the area of fluid collection but may not precisely show the source of the urine leak (Table 3).

Renal scintigraphy can be used to contribute to the diagnosis if the patient has good renal function. It is useful for detection of urine leaks after renal transplant.¹⁴ Cystography imaging can also be used to show bladder leaks. This imaging can be associated with a retrograde opacification.

An anterograde nephrostogram is performed if the patient has demonstrable hydronephrosis (Figure 2). This exploration represents the "criterion standard" imaging for locating the leak and for specifying its importance.¹⁵ Table 3 summarizes the merits and disadvantages of the principal imaging types for urinoma analyses.

Urinomas can cause hydronephrosis (extrinsic ureteral obstruction), and a percutaneous drainage should be performed. Infection can be also a complication.

Evidence-Based Management Plan

Prevention
Ureteric ischemia can be prevented by avoiding excessively dissected tissue around the ureter donor, which can lead to poor ureter vasculature. The preservation of per-ureteric tissue is crucial to minimizing the risk of devascularization of the ureter. In addition, the use of a ureter as short as possible may also minimize this risk. Routine double J stent placement at the time of ureterovesical anastomosis is recommended because it appears to decrease the urologic complication rate, although it is associated with higher risk of urinary tract infections.⁸

Treatment of urine leak
The treatment depends on the leak site and the possible cause of urinoma formation. Table 4 summarizes the therapeutic options.

Percutaneous treatment
Patients with urinary leak due to ureteral fistula can be treated with percutaneous nephrostomy if it is a relatively small leak and there is hydronephrosis (Figure 3). The objective of this conservative management is to divert urine from the urinary leak site. A larger urine collection may need to be drained to reduce risk of infection if there is a delay in operative intervention.^16-19 It is possible to manage urine leak associated with hydronephrosis by maximal decompression with external drainage (percutaneous nephrostomy) and double J stent placement. However, sufficient hydronephrosis is required to perform nephrostomy. At the time of percutaneous nephrostomy, it is possible to perform an antegrade nephrostogram to evaluate the importance of extravasation and to guide therapeutic management, as illustrated in Figure 3. If there is a small urine leak, the patient should be treated with maximal decompression (conservative procedure).^16,17 If the urine leak is associated with hydronephrosis, an anterograde stent placement can be performed.⁵ Alcaraz and associates²⁰ assessed that percutaneous nephrostomy can result in successful treatment for 60% of recipients who develop urine leak 3 days after kidney transplant. If the conservative treatment is not sufficient, surgical exploration is indicated.

Conservative treatment in the absence of hydronephrosis
If the patient had already a ureteral stent, replacing this stent can be effective. It is essential to confirm the absence of leak before stent removal. If the patient did not receive a double J stent, retrograde placement is technically an uphill task and should not be attempted in the early postoperative period.

Open exploration and reconstruction
Open exploration should be considered for patients with extensive extravasation, with proximal fistula, or those not responding despite maximal decompression (Figure 4). Ureteric leak that is the result of anastomotic failure would require reimplantation to the urinary bladder. Ureteric leak that is a result of ureteric necrosis would require resection of the necrotic ureter and then ureteral reimplantation if needed. The reimplantation depends on the ureter perfusion and length.²¹

If the ureter length and perfusion are adequate, a reimplantation of the preserved transplant ureter is performed. If there is not enough length of well-perfused transplanted ureter, then the native ureter rather than the urinary bladder is used for anastomosis. Whether it is side-to-side anastomosis or the end of native ipsilateral native ureter is used, native nephrectomy is not required.²² Boari flap and hitching of a mobilized bladder are other options. Other techniques include the use of ileum as a neoureter, which is indicated if there is no native ureter available (ie, for previous bilateral nephrectomy).^23,24

Management of bladder leak
If a blocked transurethral catheter is the cause of the leak, then replacing the catheter is the solution. If there is a significant leak, then bladder repair may be indicated; this should be followed with a prolonged vesical drainage of at least 2 weeks.⁵

Management of calyceal leak
If calyceal leak is the result of obstruction, removal of this obstruction is the effective treatment.⁴ If this leak is attributed to segmentary renal infarction by ligation of a polar artery, conservative treatment is the first choice. Partial nephrectomy has been used previously to save the allograft in this rare instance.²⁵

Urine leak after kidney transplant should be considered if there is delayed graft function, poor urine output, or increased drainage. Biochemical analysis of drained liquid is essential and should be compared with a serum sample. Conservative treatment by percutaneous drainage should be considered as the first line of treatment in patients with relatively small urine leaks. If there is no response to conservative treatment or if the leak is significantly large, then surgical exploration should be performed. Surgical treatment depends on leak source, anastomosis type, and ureter perfusion.

Volume: 16 Issue: 1 February 2018

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