Subcapsular kidney urinoma after Percutaneous Nephrolithotomy

==inizio objective==

Percutaneous nephrolithotomy (PCNL), as primary treatment of kidney urinary stones, has regained much interest in the last decade thanks to the variations and refinements of the technique. Albeit 54% of complications are negligible, such as fever and small bleeding, for which no invasive intervention are needed (I type according to the Clavien classification), severe complications may occur and a prompt correct management should be established to avoid the worsening of patient clinical state. 1 We report on an unusual PCNL complication and its management.

==fine objective==

==inizio methodsresults==

A male patient, 43 years of age, underwent PCNL for a large left pyelocaliceal stone. Surgery was performed in Valdivia- Galdakao supine position. The percutaneous tract was established by combined radiological and sonographic guidance. The tract was dilated by balloon and a 24 F Amplatz sheath was located. As complete clearance was not achieved because of a residual lower pole calyceal stone, an ureteral double J and a 20 F nephrostomy were located for a second-look PCNL through the same tract after 7 days. After second-look PCNL residual stone was still not cleared because it was unreachable through the tract established and the patient was discharged without Nephrostomy and with the ureteral stent, with the plan of performing Retrograde intrarenal surgery (RIRS) in 3-4 weeks. Haemoglobin, Haematocrit and the renal function were normal. At the 7th day after PCNL no leakage was detected from the percutaneous tract, but the patient started to complain about flank discomfort and fever. Imaging showed a 6 cm lower-pole subcapsular collection. After 3 day of conservative management with antibiotics, the sub capsular collection did not resolve and a percutaneous 6 Fr mono-j drainage in the collection was placed. Drain output was at first purulent and evolved into urine throughout the following days. Drain urine culture was positive for E. Coli infection and Carbapenemic targeted antibiotic was offered to the patient.

==fine methodsresults==

==inizio results==

Collection drained about 400 cc in 7 days and the drain was removed when the output was less than 10 cc per day. No late complications were reported and RIRS was scheduled in 1 month to clear the residual stone.

==fine results==

==inizio discussions==

Improvement of surgical care demands transparent, consistent, and accurate reporting of surgical outcomes that are evaluated and documented in a standardised manner. 2A Clavien-Dindo Complication classification has recently been adopted and validated in a PCNL surgery. A Categorisation of percutaneous nephrolithotomy-specific complications according to Clavien classification score based on expert opinions collected from 74 urologists via an international survey has mentioned most of the PCNL complication and relative management. 3
To our knowledge the aforementioned complication is quite uncommon and deserves to be reported. In the Clavien-Dindo classification it may be located at 3b category, because its resolution needed a radiological intervention under local anaesthesia. The subcapsular collection did not resolve spontaneously because an internal fistula between the damaged calix and the subcapsular space supplying the collection had been established. The second-look PCNL irrigation without an Amplatz sheath probably plumped the collection through the fistulous small path, although it was carried out one week later when the tract should be mature enough and the calix rupture healed. Usually, the collection should shrink without further management when the collecting system is adequately drained by the stent after nephrostomy removal. That was not the case because the tract sealed quickly and the subcapsular collection continued being supplied by urine extravasation despite the double J placement. After 7 days the patient became symptomatic as the collection augmented and evolved into an abscess. Another interesting aspect we observed was the complete absence of blood clots in the collection as it was not a result of a traumatic hematoma, but rather a urine extravasation supplied by the second-look PCNL irrigation.

==fine discussions==

==inizio conclusion==

To our knowledge and experience the aforementioned complication is very uncommon and dreadful. Prompt detection and minivasive management may be resolutive.

==fine conclusion==

==inizio reference==

1. References Labate G, Modi P, Timoney A, Cormio L, Zhang X, Louie M, Grabe M, de la Rosette J, on behalf of the CROES PCNL Study Group J. The percutaneous nephrolithotomy global study: classification of complications. J Endourol. 2011 Aug;25(8):1275-80
2. Ibarluzea G, Scoffone CM, Cracco CM, Poggio M, Porpiglia F, Terrone C, Astobieta A, Camargo I, Gamarra M, Tempia A, Valdivia Uria JG, Scarpa RM. Supine Valdivia and modified lithotomy position for simultaneous anterograde and retrograde endourological access. BJU Int. 2007 Jul;100(1):233-6.
3. Krupski TL. Standardization of reporting surgical complication. Are we ready? J Urol 2010;183:1671–2.
4. de la Rosette JJ, Opondo D, Daels FP, Giusti G, Serrano A, Kandasami SV, Wolf JS Jr, Grabe M, Gravas S; CROES PCNL Study Group. Categorisation of complications and validation of the Clavien score for percutaneous nephrolithotomy. Eur Urol. 2012 Aug;62(2):246-55.

==fine reference==

Calicotomia sinistra lomboscopica per idrocalice litiasico

==inizio abstract==

Presentiamo il trattamento di un paziente di 48 anni, affetto da coliche renali a sinistra ed IVU ricorrenti, con riscontro TC di litiasi renale sinistra in idrocalice superiore sinistro.
E’ stata posta indicazione al trattamento laparoscopico del caso clinico.
Il video descrive la sede dei trocars, la preparazione dello spazio di lavoro retroperitoneale e l’isolamento parziale del polo superiore del rene sinistro, l’incisione della corticale renale assottigliata, la litolapassi con pinza.
Attraverso cateterino ureterale preventivamente posizionato, si inietta indaco di carminio, con individuazione del collettore puntiforme del calice superiore, che viene suturato. Segue prova di tenuta idraulica negativa.
Il tempo operatorio è stato di 80 minuti, sono state registrate perdite ematiche pari a 50 ml. L’emoglobina preoperatoria è stata 15.4, in I giornata postoperatoria 14.6.
La creatininemia preoperatoria è stata 1.0, in I giornata 0.8.
Al paziente è stato rimosso il catetere ed il cateterino ureterale in I giornata. Le dimissioni sono state in II giornata dopo rimozione del drenaggio.
L’ecografia di controllo a 3 mesi evidenzia assenza di ectasia calico pielica, in paziente asintomatico con urine abatteriche.

==fine abstract==

Robotic pyelolithotomy for a staghorn stone of kidney

==inizio abstract==

The video shows a case of a staghorn stone of the right kidney in a female patient 48 years old.The patient complained of recurrent infections and flank pain.The stone occupied entirely the pelvis and most of  the calyces.There was no evidence of ureteropelvic junction obstruction. Two minor calculi were in the mid calyces.
The stone was approched by robotic procedure. The renal pelvis was prepared and opened with V incision. Marked edema and hyperemia were present. The stone filling the entire pelvis and the calyces was dislocated and removed. During  maneuver part of stone in the upper calyx ruptured and was removed apart.The operative time was about 120 minutes . The two residual minor calculi were approched in a second time by endourological procedure.
There was no post operative complication.The patient was discharged after two days.Double J was removed at the third month after endoscopic laser lithotripsy of  two minor calculi. TC control after three months  demonstrated the  absence  of residual stone  and a normal configuration of the urinary tract.
In selected cases of large renal staghorn calculi the robotic surgery is very effective. The specific articulation and the finest movements of the robotic arms allow a complete removal of stone and a precise reconstruction of the urinary tract.

==fine abstract==

Renal stones treatment in Spinal-Cord–Injured patients

==inizio objective==

The risk of upper tract stone disease in patients with SCI is significantly higher than the general population. Risk for urolithiasis in the general population is estimated at 12% for men and 6% for women with annual incidence rates between 0.36 to 1.22/1000 person years. A large series study found the incidence rate after the first year post SCI was 8/ 1000 person-years with an incidence of urinary stones up to 38%.
The incidence of renal calculi appears to peak during the period immediately after SCI. This early risk of stone formation is hypothesized to be a result of a significantly increased calcium excretion because immobilization and loss of calcium from the lower extremity skeleton.
In addition bladder neurologic dysfunction as detrusor hypocompliance, detrusor-sphincter dyssynergia and detrusor overactivity can lead to increase urinary tract infection (UTI), stone disease, bladder cancer, autonomic dysreflexia, and renal dysfunction.
In these patients urinary stones are frequently composed by struvite and calcium phosphate rarely by calcium oxalate.
Higher risk of complication in these patients is related to urinary tract infections by Proteus, Ureoplasma o Klebsiella; patients positioning obliged by musculoskeletal spasticity and comorbidity.
This study reports the experience of a single unit and the objective was to evaluate incidence of complications in patients with renal stones and SCI treated with RIRS or PCNL compared to general population.

==fine objective==

==inizio methodsresults==

A retrospective chart review of patients with spinal neuropathy who underwent PCNL and RIRS was undertaken. The charts of 9 patients with spinal neuropathy who underwent PCNL and RIRS for renal stones in our institution between 2013 and August 2016 were reviewed.
All patients who underwent contrast URO TC and were evaluated to identify the preoperative stone characteristics. Stone size was determined by measuring the greatest length of the stone on CT. In case of a kidney with multiple stones the stone burden of that kidney was determined by adding the sizes of all the stones.
A urine culture was obtained preoperatively in all patients. If patients had bacteriuria, they were treated with a specific antibiotic preoperatively.
Age, operative time, stone side and characteristic, stone free rate and complications were also recorded.
All procedures were performed by a single surgeon with the experience of more than 50 cases for each treatment.
The percutaneous access was performed by the urologist. The renal puncture was done under fluoroscopic and ultrasonography control. The telescopic dilation in prone position was used under fluoroscopic control through the calix and when a supine procedure was done a pneumatic balloon for dilation was used. A 24 F Amplatz sheath was positioned, and an ultrasonic or pneumatic lithotripter used for lithotripsy. Nefroscope of 22 ch with continuous flow irrigation was used. The operative time was evaluated from the puncture to removal of Amplatz sheath. In RIRS treatment a flexible URS 7.5 ch with holmium laser lithotripsy was used. After a urinary stent DJ was inserted and was removed within two weeks. Only patients with no stones or a single stone size < 4 mm on postoperative ultrasound and KUB after 3 month was declared stone free ==fine methodsresults== ==inizio results== A total of 9 patients 6 male and 3 female, age 23-58 years (average 42) were treated and a total of 10 procedures were performed. A quadriplegia was present in 2 cases, paraplegia in 2, Multiple sclerosis in 4 and only 1 patient had a spastic quadriplegia In one patient a percutaneous treatment and the next RIRS was performed. In 5 patients kidney stones were located in the left kidney and in 4 in the right kidney. Stone free rate was higher in PCNL group. Urinary stones were located in 1 case in the renal pelvis, in 6 cases in the renal pelvis and in the lower calyx, in 1 case in the renal pelvis and middle calyx and in 1 case the stone was located in the pelvis and in two calix (middle and lower). In 3 patients hydronefrosys was also present. In 6 cases urine cultural examination was positive and the patients were treated with specific antibiotic therapy the others with third generation cephalosporine or fluorchinolone preoperative prophylaxis. Stone diameter was included between 1.4 and 4.6 cm (average 2.6 cm); in 6 cases a PCNL and in 4 cases RIRS were respectively performed. Average operative time was 54.1 min in RIRS group and 40.3 min in PCNL group. Only two patients were considered no stone free and one of them underwent RIRS. Analysis of complication showed an incidence of postoperative infection in 2 patients treated with RIRS and in one of them a serious septic event with a perirenal ematoma was recorded (Clavien IVb). No respiratory failure after awakening was reported. In PCNL group no septic events were present but a serious post-operative bleeding was recorded. The patient was treated with selective embolization and no blood transfusions were needed (Clavien IIIa). He was discharged in 5 days. Time of hospitalization was comparable to patients without SCI with a single exception of one patient with a serious complication that was kept for a long period in intensive care. ==fine results== ==inizio discussions== The management of upper tract stones is more difficult in patients with SCI than in the general population. The higher incidence of bacteriuria and infection stones increases the risk of sepsis either with the presentation of the stone or as a result of treatment of the stone. Treatment of sepsis is complicated by the high rate of multidrug-resistant bacteria within this population. Anyway only early identification and treatment of urolithiasis in SCI patients will aid in preserving renal function and minimizing associated complications. In our short series no septic complications were reported after PCNL and in this group stone free rate was higher than in RIRS group. Post operative fever and several sepsis were reported in two of four cases treated with RIRS. Not many studies about endoscopic treatment of kidney stones in patients with SCI are present. Some reports consider flexible ureteroscopy and laser lithotripsy as an effective treatment modality for SCI patients with upper urinary tract calculi with an incidence of complication of 22%. Nabbout et al. in a series of 46 PCNL in 26 renal unit report an incidence of complication of 14.3% patients, necessitating admission to the intensive care unit postoperatively. ==fine discussions== ==inizio conclusion== Percutaneous treatment seems to be more suitable in patient with renal stones and SCI. Surgical management of urolithiasis in patients with SCI should be performed in high-volume units in light of the technical challenges and higher rate of perioperative complications. ==fine conclusion== ==inizio reference== 1) Chen Y, DeVivo MJ, Roseman JM. Current trend and risk factors for kidney stones in persons with spinal cord injury: A longitudinal study. Spinal Cord 38: 346–353, 2000. 2) Welk B, Fuller A, Razvi H, Denstedt J.: Renal stone disease in spinal cord injuried patients. J Endourol. 26: 954-9, 2012. 3) Tepeler A., Sninsky B.C., Nakada S.Y.: Flexible ureteroscopiclaser lithotripsy for upper urinary tract stone disease in patients with spinal cord injury. Urolithiasis 43, 501-505, 2015. 4) Nabbout P, Slobodov G, Mellis AM, Culkin DJ. Percutaneous nephrolithotomy in spinal cord neuropathy patients: a single institution experience. J Endourol. 26: 1610-3, 2012. ==fine reference==

Ureteropieloscopia rigid and flexible: simplification of the technique in our experience

==inizio abstract==

ureteropieloscopy rigid and flexible: simplification of the technique according to our experience
The authors suggest some maneuvers to simplify the ureteropieloscopy diagnostic and therapeutic procedure that can reduce: 1) execution times, 2) minor urethral trauma, 3) reduction in the risk of dislocamneto rail, 4) use of simplified instrumentation

==fine abstract==

Nefrolitotomia percutanea e cistolitolapassi di stent ureterale calcifico in rene trapiantato

==inizio abstract==

Presentiamo il caso di un uomo di 64 anni con stent ureterale calcifico in rene trapiantato. Il paziente sottoposto a trapianto renale e posizionamento di stent ureterale a tutela dell’anastomosi uretero-vescicale 8 mesi prima , perso al follow up dal centro di riferimento , giungeva alla nostra osservazione per sintomatologia disurica irritativa e macroematuria. La TC addome mostrava la presenza di uno stent ureterale calcifico a livello del ricciolo situato in pelvi ed in vescica ed alcune calcificazioni segmentarie lungo il corpo dello stent medesimo. Descriviamo la strategia terapeutica utilizzata per la rimozione dello stent ureterale calcifico mediante litotrissia vescicale per via transureteroscopica, nefrolitotrissia ed estrazione dello stent per via percutanea ottenendo la bonifica completa della via escretrice in tempo unico. La procedura è stata priva di complicanze ed ha consentito di salvaguardare la funzione del rene trapiantato.

==fine abstract==

ECIRS: a new proposal for the patient position

==inizio abstract==

Intrarenal Combined Endoscopic Surgery (ECIRS) is a combination between retrograde intra-renal (RIRS) and percutaneous nephrolithotripsy (PCNL) surgery.
It is a very effective technique to treat: complex renal stones and contextual ureteral ones, in case of uretero-pelvic junction obstruction.
Most important things to perform this procedure are: surgical instruments, patient’s position, side of kidney puncture/dilation, intracorporeal lithotripsy, nephrostomy/stenting.
Valdivia Uria – Galdakao modified position is milestone to the technique development, according to the undoubted surgical and anesthetic advantages.
The video shows our procedure to perform ECIRS, using a new modified position, which in our experience can allows:
– patient in supine position, avoiding his 30 ° inclination on the operatory table
– respect of anatomical access to the kidney
– more space for the surgeon to perform the procedure
– increased chance to spontaneous leaking gravity of stones fragments

==fine abstract==

THE SUCCESS OF EXTRACORPOREAL SHOCK-WAVE LITHOTRIPSY BASED ON THE ULTRASOUND COLOR-DOPPLER TWINKLING ARTIFACT EVALUATION

==inizio objective==

Aim of our study was to determine the utility of the ultrasound color-doppler twinkling artifact study for predicting the success of ExtracorporeaL Shock-Wave Lithotripsy (ESWL) of ureteral calculi. To the best of our knowledge, for the first time, similar approach has been used in a patient group.

==fine objective==

==inizio methodsresults==

Between July 2015 and September 2016, a total of 178 patients who underwent to ultrasound-guided ESWL for single ureteral stones of 5 to 10 mm were included in this study. All patients underwent a baseline evaluation, including a medical history, a physical examination, a complete blood count, a serum creatinine measurement, determination of the glomerular filtration rate, a urinalysis and a color-doppler ultrasound scan of upper urinary tract. The exclusion criteria were as follows: placement of percutaneous nephrostomy tube or ureteral stent before ESWL. The ultrasound parameters included stone location and stone length. During Color-Doppler ultrasound examination single focal zone was always placed somewhat deeper than the level of the targeted stone. The presence of twinkling artifact, and if detected its signal intensity was recorded. Signal intensities of the twinkling artifacts were classified as follows: twinkling artifact not observed (grade 0); grade 1: focal and hardly observed twinkling artifact; strong signal intensity observed on only some part (grade 2) or all over the stone (grade 3)(1). To investigate the usefulness of color Doppler twinkling artifact study for predicting ESWL success-rate, patients were divided into two subgroups. Patients with no twinkling artifact (grade 0) or with focal and hardly observed twinkling artifact (grade 1) (GROUP A) and patients with twinkling artifact (grade 2 and grade 3) (GROUP B). Patients were followed up every 2 weeks after ESWL with ultrasound. If there were significant fragments others sessions of ESWL were planned. The final results were considered after the complete passage of all fragments or after 3 months from the last ESWL session. The outcome of ESWL was described as a success with stone-free condition or clinically insignificant residual fragments with no symptoms at 3 months after ESWL. Failure was defined as residual stone fragments or no evidence of fragmentation after 3 sessions of ESWL.

==fine methodsresults==

==inizio results==

The GROUP A consisted of 153 patients (85.9%), and the GROUP B consisted of 25 patients (14.0%). The average stone size (mm) in the two groups was 7,9±1,4 and 8,1±0.5 respectively, which was no significantly different between the two groups. Other ultrasound parameters such as stone location and hydronephrosis were not significantly different. No significant differences in other baseline characteristics were found between the two groups. Overall success rates in the GROUP A and GROUP B were 86.9% (133 patients) and 100% (25 patients) respectively. Mean time to stone free status and the average number of ESWL sessions required for success in the two groups were 18.7±31.7 days compared with 12.2±20.0 days and 1.2±1.2 compared with 1.1±1.5, respectively. However, the subgroup analysis divided by stone size and stone location was not performed because the sample size was relatively small for accurate analysis.

==fine results==

==inizio discussions==

ESWL is a non-contact, non-invasive technique for the treatment of urinary calculi. It is widely used in clinical treatment, and this method of removing stones has advantages such as simple operation, less pain and lower cost(2). Several studies concluded that the outcomes of ESWL correlate with several factors, including type of lithotripter, stone size, stone location, stone composition, calyceal and ureteral anatomy, body mass index and recently the stone attenuation value(3). Many previous studies have investigated the relationship between computed tomography (CT) parameters and successful ESWL. Data revealed that the energy of the shock wave needed for fragmentation was related to stone density, and that the higher the stone density, the stronger the shock wave energy needed to achieve fragmentation(4). A twinkling artifact associated with color doppler ultrasonography of urinary calculi has been described as a rapidly changing mixture of red and blue seen on or behind the stone where the shadowing would be expected on B-mode imaging. The etiology of the artifact is not completely understood, but it has been hypothesized to be from phase or clock jitter, and stone surface roughness. More recent data suggest that twinkling may arise from tiny gas pockets on the stone surface. Several studies have demonstrated the dependence of the twinkling artifact on ultrasound machine settings and stone composition. The twinkling artifact has been observed in 83% to 96% of stones seen on B-mode ultrasonography(5). In the identification of urinary stones this artifact provides additional contribution to gray-scale ultrasound, and increases diagnostic success rates. Some stones do not induce formation of artifact, while others lead to greater amount of artifact. For the first time Chelfouh et al. investigated this correlation. In this in vitro study performed with small number of stones, calcium oxalate monohydrate stones generally did not induce formation of twinkling artifact, while a correlation between calcium oxalate dihydrate stones and twin¬kling artifact was found(6). Bulakçı et al, in vivo, evaluated to the role of twinkling artifact observed in color doppler analysis for the pre¬diction of the mineral composition of urinary stones. Overlapping intensities of the twin¬kling artifact have been also observed among all stone groups. On the other hand, mineral composition of the stones with a density value below 780 HU which also display grade 3 artifact can be evaluated in favour of non-calcium stones(1). In our study we demonstrated that the absence of ultrasound color-doppler twinkling artifact correlate with a higher ESWL success rate for the treatment of ureteral stones. The lower number of patients and the dependence on the sonographer of the ultrasound exam are important limitation of our study. Statistical power of our study was weakened. Therefore, further prospective studies should be conducted with greater number of patients. However we think that these preliminary data which is contributed to the literature will be helpful as guiding tools for future investigations.

==fine discussions==

==inizio conclusion==

Our study shows the utility of the ultrasound color-doppler twinkling artifact study for predicting the success of ESWL of ureteral calculi.

==fine conclusion==

==inizio reference==

(1) Bulakçı M, Tefik T, Akbulut F, Örmeci MT, Beşe C, Şanlı Ö, Oktar T, Salmaslıoğlu A. The use of non-contrast computed tomography and color Doppler ultrasound in the characterization of urinary stones – preliminary results. Turk J Urol 2015;41(4):165-70.

(2) Yang C, Li S, Cui Y. Comparison of YAG Laser Lithotripsy and Extracorporeal Shock Wave Lithotripsy in Treatment of Ureteral Calculi: A Meta-Analysis. Urol Int 2016; DOI: 10.1159/000452610

(3) Massoud AM, Abdelbary AM, Al-Dessoukey AA, Moussa AS, Zayed AS, Mahmmoud O. The success of extracorporeal shock-wave lithotripsy based on the stone-attenuation value from non-contrast computed tomography. Arab J Urol 2014;12(2):155-61

(4) Gücük A, Uyetürk U. Usefulness of hounsfield unit and density in the assessment and treatment of urinary stones. World J Nephrol 2014;3(4):282-6

(5) Sorensen MD, Harper JD, Hsi RS, Shah AR, Dighe MK, Carter SJ, Moshiri M, Paun M, Lu W, Bailey MR. B-mode ultrasound versus color Doppler twinkling artifact in detecting kidney stones. J Endourol 2013;27(2):149-53

(6) Chelfouh N, Grenier N, Higueret D, Trillaud H, Levantal O, Pariente JL, et al. Characterization of urinary calculi: In vitro study of ‘’twinkling artifact’’ revealed by color-flow sonography. AJR Am J Roentgenol 1998;171:1055-60.

==fine reference==

One shot renal dilation versus gradual metal telescopic dilation technique in percutaneous nephrolithotomy: comparison of safety and effectiveness

==inizio objective==

Renal dilation (RD) is an important step in percutaneous nephrolithotomy (PCNL). It is usually done using metallic telescopic dilators (Alken), sequential fascial dilators (Amplatz), and single-step balloon dilator (BD). Despite its high costs, BD is considered the most modern and safest system. The aim of this study was to evaluate the feasibility of one-shot (OS) RD versus metallic telescopic (MT) dilation technique for tract creation in PCNL (1).

==fine objective==

==inizio methodsresults==

We enrolled 90 consecutive patients whose underwent PCNL for a renal stone at our institution from October 2015 to September 2016. The patients were randomized into two groups, with the first (Group A) having OS RD using the 30-F Amplatz dilator, and the second (Group B) having gradual dilation using the MT dilators (Alken). Intraoperative outcomes were collected in a prospectively maintained database and analyzed. Postoperative complications have been classified according to the Clavien-Dindo (CD) system (2). The stone-free rate was assessed using a plain abdominal film on the day after surgery. Statistical analyses were conducted using SAS version 9.3 software (SAS Institute, Inc., NC). Mean values with standard deviations (±SD) were computed and reported for all items. Statistical significance was achieved if p-value was ≤0.05 (two-sides).

==fine methodsresults==

==inizio results==

All procedures were performed by a single surgical team in the prone position. There were no differences in the demographics and baseline characteristics between the two groups. In all patients of the Group A there was renal access with correct tract dilation except for 9 out of 45 (20%) patients in which a shift from the OS to the MT dilation was needed. There was a significant differences in successful dilation (p=0.0095). There were no significant differences in transfusion rate (p = 0.56) and in hemoglobin decrease (p = 0.60) between the two groups. OS dilation had significant shorter access time (p = 0.019) and X-ray exposure time (p=0,031) than MT dilation. There were no significant differences in stone-free rates (p=0.56) and in complication rates (p=0,65) between the groups. Table 1 reports post-operative complications according to CD systems.

==fine results==

==inizio discussions==

Tract dilatation is an important step in PCNL, and inadequate RD can lead to a failure of the procedure or to provoke bleeding. In our department RD is classically done using metallic telescopic dilators (Alken) or single-step balloon dilator. The single-step balloon dilator is a safe but expensive technique. Even if in 9 patients of the Group A a shift from the OS to the MT dilation was needed, no significant differences in transfusion and complication rates were seen. Moreover OS dilation had significant shorter access time. In our opinion the difficulty encountered to obtain an adequate access using the OS dilation, could be related to the difficulty to perforate the layers of abdominal wall and the Gerota’s fascia.

==fine discussions==

==inizio conclusion==

OS RD is a cheap, effective and safe technique for tract creation in PCNL, with shorter access time and X-ray exposure time and without increased complications.

==fine conclusion==

==inizio reference==

1- Nour HH, Kamal AM, Zayed AS, Refaat H, Badawy MH, El-Leithy TR.Single-step renal dilatation in percutaneous nephrolithotomy: A prospective randomised study. Arab J Urol. 2014 Sep;12(3):219-22.

2- de la Rosette JJ, Opondo D, Daels FP, Giusti G, Serrano A, Kandasami SV, Wolf JS Jr, Grabe M, Gravas S.Categorisation of complications and validation of the Clavien score for percutaneous nephrolithotomy. Eur Urol. 2012 Aug;62(2):246-55.

==fine reference==