Pediatric robotic‐assisted laparoscopic ureterocalycostomy: Salient tips and technical modifications for optimal repair

Abstract Introduction Ureterocalycostomy is a necessary option for renal salvage in cases where conventional reconstructions have failed or as a primary option in anatomic situations such as intrarenal pelvis, malrotated, or horseshoe kidney. The primary principle of this procedure is to allow for dependent drainage. Ureterocalycostomy is often difficult due to extensive scar tissue and may be complicated by bleeding in the setting of a normal functioning lower pole cortex, compared to thin renal cortex and poor renal function as seen in end‐spectrum of the obstruction. Identification of a dependent calyx and hemostasis can be difficult when there is a normal cortical thickness. Though the vascular control of hilum is an option, we suggest some simple tips to avoid this step and optimize surgical results. We present our experience and salient technical tips with pediatric robotic‐assisted laparoscopic ureterocalycostomy and provide a step‐by‐step video. Methods Four patients underwent robotic‐assisted laparoscopic ureterocalycostomy between the years 2012 and 2016 by a single surgeon. Perioperative outcomes measured included operative time, hospital stay, pain relief, degree of hydronephrosis on postoperative ultrasound at 3 months, and renal scintigraphy as needed. We describe the operative procedure and provide tips on identifying a dependent lower pole calyx with flexible nephroscopy and needle puncture, the use of harmonic scalpel for incision of the lower pole cortex, and anastomosis by pre‐placement of interrupted sutures as the urothelium of the renal calyces is thin and friable. Results Patients ranged in age between 11 months and 14 years old. Three of four patients had one prior pyeloplasty, and one patient had two prior pyeloplasties. Mean operative time (incision to closure) was 208 minutes. No Clavien‐Dindo 30‐day complications were encountered and no patients required blood transfusion. Anatomic success was reported in all patients with a mean follow‐up of 4.46 years; however, one patient ultimately required nephrectomy despite patent anastomosis, which would not drain due to a capacious pelvis. Conclusions Robotic‐assisted laparoscopic ureterocalycostomy is feasible in re‐operative cases with extensive scaring and in patients with normal lower pole renal cortex. We offer tips to allow for safe and proficient performance of this procedure.

principle of this procedure is to allow for dependent drainage. Ureterocalycostomy is often difficult due to extensive scar tissue and may be complicated by bleeding in the setting of a normal functioning lower pole cortex, compared to thin renal cortex and poor renal function as seen in end-spectrum of the obstruction. Identification of a dependent calyx and hemostasis can be difficult when there is a normal cortical thickness. Though the vascular control of hilum is an option, we suggest some simple tips to avoid this step and optimize surgical results. We present our experience and salient technical tips with pediatric robotic-assisted laparoscopic ureterocalycostomy and provide a step-by-step video.
Methods: Four patients underwent robotic-assisted laparoscopic ureterocalycostomy between the years 2012 and 2016 by a single surgeon. Perioperative outcomes measured included operative time, hospital stay, pain relief, degree of hydronephrosis on postoperative ultrasound at 3 months, and renal scintigraphy as needed. We describe the operative procedure and provide tips on identifying a dependent lower pole calyx with flexible nephroscopy and needle puncture, the use of harmonic scalpel for incision of the lower pole cortex, and anastomosis by pre-placement of interrupted sutures as the urothelium of the renal calyces is thin and friable.
Results: Patients ranged in age between 11 months and 14 years old. Three of four patients had one prior pyeloplasty, and one patient had two prior pyeloplasties. Mean operative time (incision to closure) was 208 minutes. No Clavien-Dindo 30-day complications were encountered and no patients required blood transfusion. Anatomic success was reported in all patients with a mean follow-up of 4.46 years; however, one patient ultimately required nephrectomy despite patent anastomosis, which would not drain due to a capacious pelvis.

| INTRODUC TI ON
Ureterocalycostomy is a necessary option in cases where conventional reconstructions have failed or as primary option in anatomic situations such as intrarenal pelvis, malrotated, or horseshoe kidney.
In re-operative cases, a scarred renal pelvis and significant peripelvic fibrosis is often encountered. The ureter is often engulfed in scar tissue and may be difficult to identify. Ureterocalycostomy is useful in patients with extensive peripelvic scarring, allowing for dependent drainage, and may compensate for lack of adequate ureteral length.
Laparoscopic and robotic-assisted laparoscopic ureterocalycostomy has a good track record of success in the adult literature. [1][2][3][4][5] As this procedure is infrequently performed, there is a paucity of literature regarding robotic ureterocalycostomy in the pediatric population. 6,7 We report our experience with robotic ureterocalycostomy of a single surgeon and describe salient tips for successful repair, especially in patients with ample renal cortex where identification of a dependent cortex may be difficult and bleeding may occur during lower pole nephrectomy.

| Preoperative work up
All patients undergo a renal ultrasound and a MAG3 lasix renogram prior to operative intervention. In patients who have required percutaneous nephrostomy tubes, an antegrade nephrostogram can be used to better delineate anatomic obstruction. MR Urography can be an alternative tool in the preoperative setting in the complex reoperative patient. MRU provides functional and anatomic information, but often requires sedation for children and is costly, without much utility as a renal scan can provide similar functional information. An on-table retrograde pyelogram is performed to delineate the anatomy of the ureter, UPJ, and assess length of scarring. Conclusions: Robotic-assisted laparoscopic ureterocalycostomy is feasible in reoperative cases with extensive scaring and in patients with normal lower pole renal cortex. We offer tips to allow for safe and proficient performance of this procedure.

K E Y W O R D S
pediatric, robotic, ureterocalicostomy, ureteropelvic junction obstruction concern regarding the healing of the anastomosis. Drain creatinine is only sent if the output is high, and is removed after 48-72 hours. Salient tips for robotic-assisted ureterocalycostomy 1. Flexible nephroscopy to identify dependent calyx and minimize nephrotomy to preserve nephrons 2. Use of harmonic scalpel when creating nephrotomy to decrease bleeding, without need to clamp hilum 3. Use of stay suture or hitch stitch for reconstruction due to mobility of the lower pole of kidney 4. Pre-placement of anastomotic sutures on calyx as these easily tear 5. Drain placement is recommended to diagnose and control a urine leak

| ME THODS
We retrospectively identified four patients who underwent robotic-

| RE SULTS
A total of four patients underwent robotic-assisted laparoscopic ureterocalycostomy.   scalpel transmits a large amount of energy and heat to tissues which is advantageous for hemostasis. When using the harmonic scalpel, one must take caution near the collecting system, as significant tissue necrosis can lead to postoperative urine leak due to anastomotic breakdown. As only a nephrotomy is made, maximally sparing the lower pole parenchyma, we have had success without requiring clamping of the hilum. Significant bleeding can be encountered during the cortical dissection, especially if a guillotine amputation is planned, therefore, hilar control may be necessary. The use of a stay suture on the lower pole of the kidney and/or hitch stitch can allow for ease of reconstruction.

| D ISCUSS I ON
We recommend pre-placing interrupted anastomotic sutures on the calyx first, as the calyceal urothelium is delicate and sutures may easily tear. A separate suture is not used to evert the calyceal edge. Then the interrupted sutures can be placed on the spatulated ureter and tied. A drain is routinely placed. These tips allow for proficiency during this operation.
One of the most feared and frequent complication following ureterocalycostomy is recurrent obstruction. Success of UC has varied, with adult literature 60%-77%. 1,8 and pediatric literature with a 70%-90% success rate or greater. 6,7,[9][10][11] Success between open and minimally invasive techniques have not been directly compared, but appear to be similar. Failure rates correlate with poor preoperative GFR and renal cortical thickness of <5 mm. 1 Mean time to failure in a large series was 5.5 months with majority of patients failing within a year. 1 Authors recommend guillotine lower pole nephrectomy in order to reduce anastomotic stricture rates. 12 We have had success with a lower pole nephrotomy. The flexible nephroscopy guided needle puncture onto a dependent calyx allows for appropriate exposure and wide anastomosis without lower pole nephrectomy. We believe that guillotine amputation of the lower pole leads to unnecessary loss of nephrons in patients who may have a compromised kidney. With a median follow-up of 4.46 years, we believe this technique prevents long-term obstruction.
In two patients who underwent MAG3 renal scintigraphy postoperatively, both showed a decrease in the T1/2 of the affected moiety.
One patient in this series did proceed to nephrectomy due to chronic flank pain and a poorly draining, capacious renal pelvis despite patency of the ureterocalycostomy as seen on multiple retrograde pyelograms. Other reported complications such as urinary leak and bleeding requiring transfusion were not observed in our cohort. A drain is routinely left in place in order to manage these complications.
In most cases, this operation may salvage the kidney and avoid nephrectomy. In pediatric patients with poorly functioning moieties (split function <20%), surgical intervention to improve drainage may allow modest renal recovery with low rates of failure (3%). 13 The combined assessment of renal ultrasound and DMSA with a decompressed kidney may offer a more accurate depiction of renal function. Alternative salvage operations include ileal ureter, buccal mucosal grafting, appendiceal interposition, and auto transplantation (with pyelocystostomy) which can add morbidity and uncertainty in regard to long-term outcomes. Buccal mucosal grafting in upper tract reconstruction is a novel technique which has been recently popularized with high rates of success in an adult population. 14 This may be an appropriate salvage maneuver in children who fail pyeloplasty, however long-term outcomes should be established before applying this technique to a vulnerable pediatric population. Other considerations of the buccal mucosal graft utilization in children include the potential morbidity of facial deformity and contracture. Additionally, the length of buccal mucosa graft able to be harvested from a pediatric population may be inadequate for complex upper tract reconstruction.

| CON CLUS ION
Robotic-assisted laparoscopic ureterocalycostomy in children is feasible in re-operative cases with extensive scaring and in patients with normal lower pole renal cortex. We offer tips to allow for safe and proficient performance of this procedure.

CO N FLI C T O F I NTE R E S T
Dr Mohan Gundeti is co-director of the NARUS course. There are no other conflict of interest.