A case of high drain output after renal transplantation: Review of current evidence

Surgical complications remain common causes of renal transplant dysfunction in early post transplant period. Any patient with a renal graft dysfunction should be evaluated for surgical complications including collections. Investigations should be tailored individually to each patient. Correlation of clinical examination and laboratory evaluation is fundamental for diagnosis in such cases. Biochemical assay of the drain fl uid and radiological examination are essential.


Introduction
In this review, we discuss different causes of collections after a renal transplant, their diagnosis and management.

Scenario
The index patient is a renal transplant recipient day 3 post

Abstract
Surgical complications are not uncommon after renal transplantation. They should always be in the differential diagnosis of renal graft dysfunction. While ruling out or confi rming a surgical cause of graft dysfunction, a sequential approach should be undertaken starting from clinical examination and moving on to more invasive investigations as the clinical picture becomes clearer. Biochemical assay of drain fl uid is important. Causes of a collection around/near the graft include abscess, hematoma, urinoma and lymphocele. Treatment of each of them is different.
Causes of urinoma can be donor derived or surgical technique related. SPECT/CT may be needed to confi rm the location of urinary leak. Treatment of the urinoma depends on its severity and location. Small and distal lesions can be treated conservatively while as larger and proximal leaks need surgical intervention. Ureteric stenting may be undertaken as a prophylaxis against urinary leak.
Lymphoceles should always be considered as a cause of perinephric collection in renal transplant. It can be differentiated from a urinoma by the concentration of creatinine in the drain fl uid. The treatment may be conservative or surgical depending on the size of the lymphocele and initial response or resistance to conservative management.

Scenario:
A 28-year-old CKD 5 underwent a kidney transplantation from his brother with primary function. Post-surgery, the drain is quite productive (820 mls on day 2 and 750 mls on day 3). Drain fl uid biochemistry showed K of 28 mmol/L and creatinine of 16000 μmol/l. His serum creatinine on that day was 416 μmol/l and serum K is 5.1 mmol/L. living donor renal transplant with productive drain (820 mls on day 2 and 750 mls on day 3). Drain fl uid biochemistry has showed K of 28 mmol/L and creatinine of 16000 μmol/l. His serum creatinine on that day was 416 μmol/l and serum K is The approach to this case should be orthodox, starting with physical examination looking for any pre-renal causes of The second step would be to perform a scan to rule out or confi rm urinary obstruction, to check perfusion and look for any collections. Serum and drain fl uid should be sent simultaneously for biochemistry if needed.
The likely causes of a collection and dysfunction in early post renal transplant period are urinoma, hematoma/haemorrhage, lymphocele or abscess (Table 1). These pathologies can generally be differentiated from each other by examination of the drained fl uid. While hematoma fl uid will have high hemoglobulin concentration, the fl uid from an abscess will have high white blood cell count and a urinoma fl uid would be positive for high creatinine.

Urinoma
The risk factors for urinary complications post transplant are male recipient, black recipient and U stitch technique of the ureteral anastomosis [2]. Ureteric complications are more likely after donation after cardiac death (DCD) than after living donation or donation after brain death (DBD) though donor type is not a risk factor [3]. In addition, urinary leak may be lower after ureteroureterostomy as compared to ureterocystostomy [4].
Urinary leakmay present clinically with a picture of peritonitis if the urine is present in peritoneal cavity in case of an intraperitoneally placed kidney. More commonly, swelling around the graft or high drain output may be the only sign. In some cases, it may present as a swelling of the ipsilateral lower limb.

Causes
The major cause of urinary leak is ureteral necrosis and devascularisation during organ harvest. However, there are other causes of urinary leak like technical failure including a poor construction of the ureterocystostomy resulting in a nonwatertight anastomosis, dehiscence or polar artery ligation.
Depending upon the cause, the urinary leak may present within 24 hours if secondary to technical error or after 2 weeks if secondary to necrosis [6].

Diagnosis
Biochemical -The drain fl uid is six times more likely to be secondary to urine leak compared to lymphocele if the drain creatinine is 6 times higher than the plasma creatinine and the urine creatinine is not more than 3 fold drain creatinine and is 7 times higher than the plasma creatinine [7]. It is noteworthy that drained fl uid from the urine leak may have creatinine nearer to plasma if creatinine clearance is low.
Radiological -Ultrasonography helps in identifying a collection around or near the renal graft. However, it may be diffi cult to differentiate urinoma from other collections.
Usually, urinoma is a well-defi ned simple collection without internal echoes while as abscesses and hematomas are hyperechoic with septations. A urinoma may show septations if it is secondarily infected or blood contaminated.
In some cases diagnosis may still be unclear. Scintigraph-ic99mTc-DTPArenography may play an important role in such cases especially if the volume of urine leak is large. The pattern of photopenia and its course over time may differentiate urine leak from lymphocele, hematoma and abscess. The initial photopenic region which becomes hotter than the background is very likely secondary to a urine leak as compared to other causes [8].
Scintigraphy is more sensitive than ultrasonography in the diagnosis of urinoma. AyşegülDirlik et al reported fi ve patients who underwent imaging related to collection around the graft.
Ultrasound diagnosed urinary leak in one patient out of four while as scintigraphy detected all the four cases of urinary leak in addition to one false positive [9].
Even after confi rming that the collection is secondary to a urine leak, the exact location of the leak may still be undetected.
Accompanying SPECT/CT may be very useful in evaluating the anatomy of the urine leak [10], (Figure A-C).

Treatment
Stenting: ureteral stenting is used routinely after renal transplantation. The contribution of stents in preventing urine leaks is controversial.
In this prospective randomized study [11], with a total of 194 renal transplant patients, 97 were randomized to have a double pigtail stent inserted and another 97 patients were without a stent. 6 patients in the no-stent group had urinary leak while only one patient in the stent group developed a urinary leak, hence favouring stenting.
In another randomized trial, 280 renal transplant recipients were randomized to either a no-routine stent group or a routine stent group. In the no-routine stent group patients were not stented except for an intra-operative event based on surgeon'sopinion. There was no difference between the groups in an intention to treat analysis [12]. In one study the documented closure rate was 87% with infection related complications occurring in 17% and one case of stricture [13]. Balloon dilation or endoureterotomy may be considered for short, low-grade strictures, but open reconstruction is associated with higher success rates.
Nearly 60% of patients can be successfully managed with a pelvic drain and urinary decompression (nephrostomy tube, ureteral stent, and indwelling bladder catheter). Proximal, large-volume, or leaks that persist despite urinary diversion, require open repair [14]. Patients, who develop transplant ureteral fi stulae, can be treated endourologically [15].

Lymphocele
Another cause of high drain output after renal transplantation is a lymphocele which is a collection of lymphatic fl uid around the kidney. It is a hard fi brous cavity without epithelial lining containing lymph [16].
Before ultrasound, the incidence of lymphocele ranged between 0.6 -18% increasing to around 33% with the use of ultrasound [17,18]. There are reports of some lymphoceles developing as late as after 3 years of transplantation [20].
Diagnosis: As discussed above, the creatinine level in the fl uid from lymphocele is not as high as in a urinoma and should match serum creatinine. Once it is established that the drain fl uid is lymph, next question to answer is whether the lymph is recipient originated or from the transplanted kidney. CK activity, a marker of the iliac lymph, should be checked. The nomogram by Pacovsky can be used to fi nd the contribution of renal lymph [21].

Treatment:
If the lymphocele is small, it may resolve following percutaneous drainage. Bigger lymphoceles or those resistant to drainage may resolve by sclerosis with doxycycline, bleomycin, talc or fi brin glue. In some cases deroofi ng, either laparoscopic or open, is needed. Sclerosis may, however, cause ureteric fi brosis.

Hematoma
The hematoma can develop spontaneously, post biopsy or post surgical trauma.
The clinical presentation can be graft dysfunction as a result of hypovolemia or hydronephrosis secondary to displacement by the hematoma [22]. Clinical signs of hypovolemia may or may not be present.
Pre transplant use of anticoagulants adds to the risk of bleeding while as living donor transplant recipients and those with lower BMI carry lesser risk of bleeding [23].
The drain fl uid may contain frank blood or be serosanguinous.
Hematomas are usually echogenic on US but lose echogenicity as they age. Hematomas have high-attenuated components in acute stage, but attenuation diminishes with time [22].
The hematoma can be managed conservatively if it is small but needs surgical exploration if large or compressing. There is a risk of infection and abscess formation.

Abscess
Urinoma, hematoma and other collections around a transplanted kidney can transform into an abscess. The clinical signs of sepsis may or may not be present. The drain fl uid contains high number of WBCs.
Infl ammatory markers may be elevated but can be so as a result of recent surgery or may be blunted because of immunosuppression.
As opposed to renal cortical abscesses, the perinephric abscesses are more likely to be due to gram negative bacteria especially Enterobacteriaceae. Rare organisms like salmonella have been reported [24].
Abscesses can have a non-specifi c appearance at US while as CT may differentiate them from other collections because of the gas present in an abscess [22].
Drainage would be needed in most of the cases [25,26].

Conclusion
Urinoma is not uncommon in early post transplant period and should always be in differential diagnosis of a collection around renal transplant or in recipients with high drain output.
The drain fl uid should be sent for biochemical assay including creatinine level and be matched with the serum creatinine.
The management may be conservative or surgical depending upon the size and location of the urinary leak. Conservative management includes percutaneous drainage and should be undertaken regardless whether a surgical exploration is considered or not.