According to the relevant studies retrieved in the database,the incidence of renal transplant lithiasis is lower(0.52%), and it is the least described urologic complication of renal transplantation.However, urinary obstruction caused by renal transplant lithiasis can even lead to a devastating loss of allograft without timely and appropriate therapy.We should pay more attention to this complication.
The etiology of renal transplant lithiasis includes donor-grafted, metabolic abnormality and mechanical factor. Renal transplant lithiasis identified within 6 weeks after transplantation are usually accepted as native to the donor kidney [33], The increasing use of CT imaging in living donor assessment has given rise to an increased detection of asymptomatic renal calculus [34]. Nevertheless, the British Transplantation Society guidelines indicate that potential donors with a small renal calculus on imaging should be considered potential kidney donors if they do not have significant metabolic abnormality [35]. It is generally considered that renal calculus less than 4 mm could not be contraindication to donation even they are left in situ [15]. Therefore, in this case the donated kidney can be transplanted without removal of the stone. Ganpule thought that introduce of a ureteral stent can be useful to make the stone pass spontaneously [36]. For the donors after brain death,CT is not universally performed before operation due to the serious illness of donors.Therefore,the incidental renal calculus was found more often in deceased donors than that in living donors during procuring the donated kidney. Larger stones should be removed on the bench prior to transplantation. Both ESWL and nephrotomy can be performed to remove the stones prior to transplantation [37]. Nevertheless, Ex vivo ureteroscopy as a convenient procedure is recommended to retrieve the stones after kidney procurement [38]. The most common metabolic abnormalities contributing to reanl calculus are hyperparathyroidism and hyperuricemia. Hyperparathyroidism usually exists in the patients with urimia due to the systemic metabolic abnormality.It leads to hypercalcemia which is one predisposing factor of renal calculus.Many of patients with urimia even suffer from native kidney stone before transplantation,although they are usually asymptomatic. Most of recipients present with hyperuricemia after kidney transplantation,which is one of side effects of immunosuppressive drugs. Norlen et al. considered that cyclosporin A produced hyperuricosuria in about 50–60% of patients receiving this medication for immunosuppression [39]. Also,ureteral stricture or obstruction due to unskilled surgical technique can lead to renal transplant lithiasis. Additional, patients with UTI are more likely to suffer from renal stone, vice-versa,renal stone can lead to UTI. Unexpectedly,our case did not have any predisposing factors mentioned above. Moreover,he was even burdened by renal stone for two times.Based on the constituent of his calculus,we deduced that the level of uric acid in the urine maybe higher although it was normal in the blood.It’s a pity that we did not detect the uric acid in urine.
The patient with reanl transplant lithiasis usually has no specific symptom.They can present with oliguria,anuria,hematuria,urinary frequency, UTI, allograft dysfunction or even ARF, but seldom with graft pain. As we mentioned above, this can be attributed to denervation of the allograft kidney. Our data also demonstrated that only 3.18% of patients presented pain,and 28.90% of them were asymptomatic.Therefore,the patient usually would have a high propensity to be delayed for diagnosis.Our case presented oliguria,anuria,UTI and ARF during the two attacks, but without pain.Due to lack of early manifestations, he was not diagnosed until the advanced stages of the disease.This also brought a huge impairment of the allograft,and the impairment would not be reversed if it was delayed for a few more days.Therefore,we recommend ultrasonography as routine examination during the recipients’ follow-up,in ordre to detect the renal calculus in the early stage.
Management of renal calculus includes conservative treatment,ESWL,PCNL,URS and open surgery,and the choice of treatments depends on patient’s symptom,the etiology,position and size of the stone. Challacombe et al. considered that treatment protocols for calculus in the transplanted kidney could mimic those for a solitary kidney [6]. Nevertheless, the management of transplant kidney lithiasis is more challenging and complicated.The renal transplantation recipients have lower immunological activity than general patients due to immunosuppresive drugs. They are more susceptible to all kinds of infection.Therefore,all the operation including surgery and anesthesia for the recipients shoud be performed with more caution.For patients with stone less than 4 mm and no presenting any symptom or urinary obstruction,it is more possible for stone to pass spontaneouly, and conservative treatment can be chosen with close follow-up [16]. An alkalinizer drug can be recommended for patients with radiolucent stone and lower pH value of urine during the follow-up.
ESWL, as a non-operative treatment modality,is recommended for patients with stone less than 15 mm [40], and its most distinct advantage is that it can avoid risk of infection and impaired wound healing caused by surgery [32]. Nevertheless,some drawbacks of this treatment need to be noted.Firstly, the iliac bone adjacent to the transplanted kidney may potentially decrease the effectiveness of the shock waves.Secondly,it usually requires multiple sessions of operation to completely disintegrate the calculus, meaning possible impair to the allograft.Thirdly, stone debris which are left in the kidney may potentially cause ureteral obstruction. Combination of ESWL and other auxiliary managements such as PCNL or URS can siginficantly decrease the disadvantages.
PCNL, as the most common operation, is used widely for the renal transplant lithiasis patients with stone size more than 2 cm or when ESWL failed [27]. PCNL is usually performed under general anesthesia in the supine position due to the special location of transplanted kidney. For the renal transplant recipients, the access to the pelvicaliceal system is usually punctured through an anterior calyx in the upper pole with the guide of ultrasonography. The serious perinephric fibrosis caused by immunosuppressive drugs increases the difficulty for puncturing and risks of bleeding [21]. And also the puncture location would become more fibrotic after the procedure. Therefore, we chose two different accesses to puncture for our case. Althoug the superficial location of the allograft is more easier to be accessed,it also increases the risk of bowel injury. This complication was reported by one of our retrieved studies [11]. This risk can be avoided with assistance of ultrasonography.During the surgery for our case,we employed both nephroscope and flexible URS,and in combination with laser lithiasis.Comparing with nephroscope, flexible URS can reach more far distance and has more advantages in treating ureteral stones. In fact,many kinds of other methods such as ESWL,scour, basket extraction and grasp can be performed as auxiliary procedures based on the position,component and size of the stone. In regarding to the impaired renal function for this case, we chose laser lithiasis instead of ESWL to fragment the stone,since the former is more effective and less impact on the allograft function. Due to the proficiency in endourological technique, a modified mini-PCNL proposed by some authors provides an excellent treatment alternative [12, 41]. This technique should be recommended in well equipped centers with experienced surgeons since it can minimize the injury risk of the interlobar arteries of the transplanted kidney [42].
URS is another minimally invasive operation,which can be completed without any incision in the body. It is pretty appropriate for ureteral stone. As there is no exact anatomic position of bladder for ureteroneocystostomy, it is really difficult to locate new orifice by retrograde URS.Although orifice can be found sometimes,guide wire can not be inserted into transplanted ureter through the anastomosis. It was just like our case. In this situation, semirigid ureteroscope or with 70° lens can be tried to facilitate the process.If it still failed after several tries, switching into PCNL promptly to avoid unexpected injury to ureter due to repeated insertions. As the lack of connective tissue support of the allograft ureter can increase the risk of perforation when performing ureteroscopy, especially with a rigid scope [27]. Some articles reported 60%-67% success rate for extracting a ureteral stone by ureteroscopic management [29, 43]. URS along with holmium laser lithotripsy or basket extraction can increase the possibility of complete calculus removal. Ureteral stent is usually placed at the end of the ureteroscopic management [34]. It was considered that the stent can hold ureter open and conduce to pass of the residual stones. Although Branchereau et al. considered that stent is not a risk factor for early stone formation [5], we still suggest that patients with stent have a higher propensity to develop renal stone than ones without stent. So we did not place the stent after the second operation.
As the development of endoscopic techniques for management of urological lithiasis, the importance of open surgery is decreasing gradually. From the retrieved literature,we can see that the rate of open surgery is very lower(4.35%).Now very few patients with renal transplant lithiasis need an open surgery.Only when patients burdened by ureteral stricture or giant staghorn calculi can not be cured by other management methods,open surgery will be considered.
Every management has its own characteristics,and we should choose the optimal one for patients based on characteristics of stones and patients’ general state. As the patients with renal transplant lithiasis are characterized by lower immunological activity, unusual anatomical position, and severe perirenal fibrosis,we should treat these patients with more caution and choose minimally invasive management. The combined usage of two or more procedures can raise the efficiency and decrease the negative impact on allograft.Based on our data, the most frequent complication is residual stones(52.73%).Therefore, we should try our best to remove all the calculi and avoid residual stones during the operation. Whether the stones were cleared should be verified by nephroscope or URS in combination with intraoperative ultrasonography.If it is impossible to remove all the stones,the small stone less than 4 mm can be left with close follow-up after operation.After removal of the stones,component of the stones should be tested to guide the medicine treatment to avoid recurrence of lithiasis. We think the most common reason for recurrence of lithiasis is exposure to predisposing factors did not be reduced or eliminated after surgery. Repeated UTI after surgery and retained foreign body, such as stent and prolene suture, also contribute to the recurrence of lithiasis.Therefore, correcting metabolic disorders, treating UTI and removing the stent timely after surgery are pivotal to prevent the recurrence of lithiasis.
To our best knowledge,few articles reported the treatment protocols for recurrence of lithiasis in the transplanted kidney. We think it should mimic the protocol that was performed for them during their first attack. Minimally invasive surgery is optimal therapy if conserved treatment is not effective. We should choose a location different from the first one for puncturing when the second PCNL would be performed, and pay more attention to the operation since both surgery and anesthesia pose a potential threat to allograft function.Try best to remove all the stones and preventive drug therapy after operation is suggested according to the component of the stone.A close follow-up composed of renal ultrasonography, urinalysis and renal function is necessary, in this way the patients with lithiasis in the early stage can be detected timely. We would collect more cases in order to statistically analyze the risks for recurrence of renal transplant lithiasis in future.