Laparoscopic Pyeloplasty via Transmesenteric Approach for Pediatric Ureteropelvic Junction Obstruction

Summary

Transmesenteric laparoscopic pyeloplasty for left-sided UPJO in children accesses the dilated pelvis through a mesenteric window, avoiding colon mobilization. The technique reduces operative time, minimises blood loss, and accelerates postoperative bowel function recovery while providing a focused surgical field.

Abstract

With ongoing advances in minimally invasive surgical techniques, laparoscopic pyeloplasty (LP) has become the standard of care for the treatment of pediatric ureteropelvic junction obstruction (UPJO). Numerous studies have demonstrated that, compared with traditional open surgery, laparoscopic surgery offers significant advantages, including reduced postoperative pain, diminished surgical trauma, accelerated recovery, and superior cosmetic outcomes, while achieving success rates comparable to those of open surgery. Among various surgical approaches, the transmesenteric approach represents an innovative route that directly accesses the renal pelvis through the mesenteric window, effectively circumventing the complex step of extensive colonic mobilization required in conventional transperitoneal laparoscopic pyeloplasty. This approach is particularly advantageous for the treatment of left-sided UPJO in children, enabling rapid and precise localization of the hydronephrotic renal pelvis while avoiding excessive colonic mobilization, thereby shortening operative time and reducing intraoperative blood loss. However, laparoscopic suturing and knot-tying techniques remain technically demanding and challenging, with a prolonged learning curve, particularly in pediatric patients with limited intra-abdominal working space, which imposes stringent requirements on the surgeon's laparoscopic proficiency. With the progressive standardization of surgical techniques and the widespread adoption of robotic-assisted surgical systems, robotic-assisted laparoscopic surgery—leveraging three-dimensional visualization and articulating robotic arms with up to seven degrees of freedom—has substantially reduced the difficulty of fine maneuvers such as intracorporeal dissection and suturing. Combining this approach with advanced laparoscopic technology may further improve surgical outcomes for pediatric UPJO and propel the field toward greater precision and minimal invasiveness.

Introduction

Hydronephrosis ranks among the most prevalent congenital anomalies in pediatric urology, with UPJO constituting its primary etiology^1,2,3. Progressive disease may precipitate urinary tract infections, flank pain, and, in severe cases, irreversible renal impairment or end-stage kidney disease⁴, necessitating timely surgical intervention. Historically, open pyeloplasty served as the gold standard for UPJO management⁵. However, the substantial incisions and tissue trauma associated with open surgery prompted the pursuit of minimally invasive alternatives. Since Schuessler's inaugural report of LP in 1993, this technique has matured considerably, offering comparable efficacy to open surgery while minimizing surgical trauma and accelerating postoperative recovery⁶. Conventional transperitoneal LP for left-sided UPJO requires descending colon mobilization to expose the ureteropelvic junction, thereby prolonging operative time and increasing the risk of complications. The transmesenteric approach, which traverses avascular mesenteric planes, enables direct access to the renal pelvis, curtailing tissue dissection and organ manipulation^7,8. Herein, we delineate the procedural nuances and clinical utility of transmesenteric LP, illustrated by a representative pediatric case of left-sided UPJO.

Case Presentation:
An 8-year-old male presented with an 8-year history of left hydronephrosis, initially detected at 24 weeks of gestation via prenatal ultrasonography and subsequently monitored postnatally. The recent onset of abdominal pain and recurrent urinary tract infections prompted further evaluation. Ultrasonography revealed severe left hydronephrosis with an anteroposterior pelvic diameter of 6.0 cm, calyceal dilation, and junctional narrowing (Figure 1A–C). Computed tomography confirmed marked pelvic distension with elevated intrapelvic pressure (Figure 2A–C). Preoperative preparation included the following: administration of a glycerine enema on the evening before and the morning of surgery for bowel evacuation; nil per os (NPO) status for 8 h prior to the operation; prophylactic antibiotic administration; and insertion of a nasogastric tube and urinary catheter.

Diagnosis, Assessment, and Plan:
Preoperative diagnosis: left UPJO. Imaging demonstrated severe pelvic dilation displacing the left colon laterally, rendering traditional transcolonic access hazardous due to the requisite colonic reflection and peritoneal mobilization, with an attendant risk of colonic injury. Accordingly, transmesenteric LP was selected as the surgical approach.

Protocol

This protocol adhered to the ethical standards of the Medical Ethics Committees at Peking University First Hospital and Ningxia Women and Children's Hospital, and informed consent was obtained from the patient's guardians.

1. Pre-surgical steps

1. Following endotracheal intubation under general anesthesia, the patient was positioned in the right lateral decubitus position (healthy side down).
2. The lumbar region was elevated using a cushion, and the affected (left) side was raised to approximately 45 ° to optimize exposure of the renal hilum.
3. A standard three-port configuration was employed. A 5-mm trocar was inserted at the umbilicus to serve as the camera port.
4. A 3-mm trocar was placed 2 cm below the left costal margin along the midclavicular line, functioning as the primary operating port. An additional 3-mm trocar was inserted 3 cm above the left iliac crest along the midclavicular line, serving as the auxiliary operating port.
5. Pneumoperitoneum was established and maintained at a constant pressure of 8 mmHg throughout the procedure.

2. Surgical steps

1. Exposure of the stenotic segment
   1. A 5-mm trocar was inserted at the umbilicus under direct vision following a small skin incision. Under laparoscopic guidance, two additional 3-mm trocars were placed.
   2. Following exploratory laparoscopy, the colon was gently retracted medially using atraumatic grasping forceps to expose the colonic mesentery.
   3. A bulging mass, indicative of the hydronephrotic left renal pelvis, was visualized through the mesentery.
   4. A 2-cm avascular window was created in the mesentery, with careful identification and preservation of the underlying mesenteric vessels (Figure 3A,B).
   5. Through this mesenteric window, the retroperitoneal space was accessed.
   6. A 2 cm incision of the perirenal fascia (Gerota's fascia) was made to identify the renal pelvis and proximal ureter. The dilated renal pelvis and proximal ureter were subsequently mobilized and fully exposed (Figure 3C).
2. Resection and anastomosis
   1. A 3-0 absorbable suture was placed at the body surface projection of the left renal pelvis, and the superior pole of the renal pelvis was suspended to an appropriate height via traction (Figure 3D).
   2. The ureter was transversely incised immediately distal to the stenotic segment, and the redundant renal pelvis was trimmed while maintaining a partial connection to preserve spatial orientation.
   3. A longitudinal ureterotomy of approximately 1.5 cm was performed along the dorsal aspect of the ureter. Employing a non-clamping anastomotic technique, everting sutures were placed with 5-0 absorbable sutures.
   4. The initial anastomotic suture was placed at the most dependent point of the renal pelvis along the renal axis, aligned precisely with the inferior extent of the longitudinal ureterotomy.
   5. Following placement of the initial stitch, anastomotic tension was assessed and confirmed to be satisfactory.
   6. The posterior wall of the ureter and renal pelvis was then anastomosed using a continuous suturing technique.
   7. Subsequently, the remaining connecting portion of the renal pelvis was completely divided, and the anterior wall was anastomosed in a similar continuous fashion (Figure 3E,F).
3. Double-J (D-J) ureteral stent insertion
   1. A 6-Fr pneumoperitoneum needle was percutaneously inserted at the body surface projection of the left renal pelvis, located below the left costal margin.
   2. A super-smooth guidewire and a (D-J) stent were introduced through the puncture site. Under direct laparoscopic visualization, the D-J stent was placed in an antegrade fashion: the distal end was advanced into the bladder, while the proximal end was positioned within the renal pelvis.
   3. Successful placement was confirmed by visualizing the distal coil of the D-J stent entering the bladder along the ureteral course (Figures 3G,H). The renal pelvis was then irrigated, and meticulous inspection was performed to confirm the absence of active bleeding.
   4. The previously preserved stenotic segment of the ureteropelvic junction was excised. The anterior wall of the ureter and renal pelvis was then anastomosed, completing the ureteropelvic reconstruction.
4. Closure and drainage
   1. Pneumoperitoneum pressure was reduced to confirm anastomotic integrity.
   2. The operative field was irrigated, and the mesenteric incision was closed with a 4-0 absorbable suture. An 18-Fr silicone drain was placed via the auxiliary port site. The incisions were closed in layers.

3. Postoperative management

1. The excised stenotic tissue was submitted for histopathological examination with hematoxylin-eosin staining.
2. Postoperative infection prophylaxis was administered, and the patient was encouraged to increase oral fluid intake to reduce the risk of stent-related obstruction⁹.
3. On postoperative day (POD) 1, following the passage of flatus, the nasogastric tube was removed. The patient was encouraged to ambulate early and gradually resume oral intake.
4. On POD 3, routine laboratory investigations, including complete blood count, serum biochemistry, urinalysis, and urinary tract ultrasonography, were performed.
5. The abdominal drainage tube was removed when the daily drainage volume was less than 10 mL for three consecutive days. The urinary catheter was removed on POD 7, and the patient was discharged on POD 10. The D-J stent was removed at 6 weeks postoperatively¹⁰.
6. Follow-up urinary tract ultrasonography was scheduled at 3, 6, and 9 months following D-J stent removal to monitor changes in the anteroposterior diameter (APD) of the renal pelvis and renal parenchymal thickness.

Results

The operative time was 120 min, with an estimated intraoperative blood loss of approximately 10 mL. No blood transfusion was required. The patient experienced an uneventful postoperative recovery, with no complications, including urinary leakage, intestinal obstruction, wound infection, or fever. Postoperative ultrasonography was performed at 1, 5, and 9 months to evaluate surgical outcomes (Figure 4A–D)¹¹. The patient remained under continuous follow-up at 9 months postoperatively. Histopathological examination of the resected specimen confirmed the diagnosis of ureteropelvic junction obstruction (UPJO), characterized by mucosal edema and fibrous tissue hyperplasia.

Figure 1: Preoperative ultrasound findings of the urinary system. (A) Dilated left renal pelvis with elevated intrapelvic tension. (B) Distended urinary bladder. (C) Normal right kidney with preserved parenchymal thickness. Please click here to view a larger version of this figure.

Figure 2: Detailed imaging characteristics of left hydronephrosis. (A) Dilation of the left renal pelvis, indicating urine accumulation. (B) Thinning of the left renal cortex, suggesting parenchymal compression. (C) Dilatation of the left renal calyces, consistent with caliectasis. Please click here to view a larger version of this figure.

Figure 3: Intraoperative steps of left pyeloplasty. (A) Identification of an avascular area of the mesentery for surgical access. (B) Exposure and identification of the dilated left renal pelvis. (C) Visualization of the left ureteropelvic junction (UPJ). (D) Suspension (hitching) of the left renal pelvis for stabilization. (E) Posterior-wall anastomosis after trimming the left renal pelvis. (F) Transsection of the left renal pelvis. (G) Placement of a double-J (D-J) ureteral stent over a super-smooth guidewire. (H) Completion of anterior-wall pyeloureteral anastomosis following D-J stent placement. Please click here to view a larger version of this figure.

Figure 4: Postoperative follow-up ultrasound findings. (A) One-month follow-up: mild left hydronephrosis; the hyperechoic tubular structure represents the D-J stent. (B) Five-month follow-up: mild left hydronephrosis with low renal pelvic tension. (C) Five-month follow-up: mild left hydronephrosis with improved left renal cortical thickness compared to preoperative status. (D) Nine-month follow-up: stable left hydronephrosis without evidence of progression. Please click here to view a larger version of this figure.

Discussion

UPJO constitutes the predominant cause of pediatric hydronephrosis, with an incidence of approximately 1/2000 to 1/1000¹². Surgical indications include pelvic separation ≥3 cm, or ≥2 cm with calyceal dilation accompanied by symptoms or recurrent infections¹³. Dismembered pyeloplasty yields efficacy rates exceeding 95%^14,15,16. Traditional LP employs a transcolonic paracolic sulcus approach, which mandates extensive colonic mobilization and attendant risks of adhesion formation, bowel obstruction, and postoperative pain. The transmesenteric approach, utilizing avascular mesenteric planes, expedites exposure of the UPJO site while averting unnecessary colonic dissection and retroperitoneal separation¹⁷. Its advantages include abbreviated exposure time; for well-defined etiologies (stenosis, high insertion, aberrant vessels, or polyps), a 2-cm incision suffices for pelvic trimming and anastomosis, thereby minimizing tissue trauma and reducing the risk of postoperative ileus. Reduced retroperitoneal dissection alleviates postoperative pain and hastens recovery¹⁸, while enhancing cosmetic outcomes—the umbilical port conceals the scar, and 3-mm ports yield minimal visible marks. Mesenteric closure with 4-0 absorbable suture prevents internal hernia formation. For D-J stent insertion, percutaneous guidewire placement under bladder distension optimizes success; cystoscopic retrograde or nephrostomy alternatives may be employed when difficulties arise¹⁹. For pediatric patients in whom D-J stent placement is not feasible, a 6-Fr silicone urethral catheter can be inserted percutaneously through the pneumoperitoneum needle puncture site as a nephrostomy tube. At two weeks postoperatively, methylene blue dye can be injected through the nephrostomy tube to assess ureteral patency by observing whether the urine turns blue; alternatively, contrast imaging may be performed for evaluation. Of note, tubeless laparoscopic pyeloureteroplasty has been reported in the literature²⁰.

The transmesenteric approach is most suitable for pediatric patients with left-sided UPJO, pronounced hydronephrosis extending beyond the descending colon, low body mass index with minimal mesenteric adiposity, and in whom a ureteral stent has not been previously placed. This approach effectively shortens operative time, reduces bowel manipulation, and facilitates early postoperative recovery. However, the technique requires the surgeon to possess a thorough understanding of the regional anatomy and to precisely identify and avoid mesenteric vessels. Based on our experience, the dilated renal pelvis should first be identified through the mesentery. The mesentery is then fully opened to visualize arterial pulsations and blue-tinged veins; meticulous identification of these structures is essential to prevent injury to critical mesenteric vessels, which could lead to intestinal ischemia and necrosis. With the application of robotic-assisted surgical systems, three-dimensional visualization and tremor filtration capabilities facilitate more precise tissue dissection and suturing, potentially expanding the indications for this approach^21,22,23. Future research directions should include multicenter, large-sample, randomized controlled trials comparing long-term outcomes and complications between the transmesenteric and conventional approaches. Further studies should also explore its application in complex cases, such as horseshoe kidney, ectopic kidney, or reoperative surgery²⁴.

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Electrocoagulation hook	Karl Storz	26050D	Used for dissection separation
Laparoscope--4K3D-laparoscope	Karl Storz	L-EX2721	The surgical field shows
Inflatable needle	Karl Storz	26120J	Used as a channel for percutaneous ureteral stent insertion
One-time use laparoscopic puncture device	Shide (Xiamen) Medical Equipment Co., Ltd.	IIA-3F-35X100	The disposable abdominal puncture device is used to create an abdominal operation hole.
Suture	Johnson medical	5-0 Absorbable Suture	Anastomosis of renal pelvis and ureter
Ureteral stent	BARD	4.7F	Used for supporting the anastomosis site
Da-Vinci surgical system	Da-Vinci		robotic-assisted surgical systems