Ureteropelvic junction (UPJ) obstruction is defined as an obstruction of the flow of urine from the renal pelvis to the proximal ureter. The condition is frequently encountered by both adult and pediatric urologists. Congenital abnormalities may be observed in both adults and children, but adults may also present with UPJ obstruction following previous surgery or other disorders that can cause inflammation of the upper urinary tract.
The critical decision to be made in dealing with suspected UPJ obstruction is whether the radiologic findings correlate with the physiologic picture. In other words, severely dilated hydronephrotic kidneys may, in fact, drain well when studied appropriately. Defining the exact anatomy and function of these kidneys is crucial when evaluating and treating these patients.
The treatment strategies for UPJ obstruction have seen a significant shift in the last several years. The gamut of surgical treatments for UPJ obstruction today includes the following:
While open pyeloplasty is still considered the criterion standard for treatment of UPJ obstruction in infants, laparoscopic pyeloplasty, with or without robotic assistance, is the treatment of choice in older children and in most adults.
UPJ obstruction is the most common cause of neonatal and antenatal hydronephrosis, occurring in one per 1500 live births. Prior to the use of prenatal ultrasonography, most patients with UPJ obstruction presented with pain, hematuria, urosepsis, failure to thrive, or a palpable mass. With the enhanced ability and availability of prenatal ultrasonography, urologic abnormalities are being diagnosed earlier and more frequently. Fifty percent of patients diagnosed with antenatal hydronephrosis are eventually diagnosed with UPJ obstruction upon further workup.
Initially, most children are treated conservatively and monitored closely. Intervention is indicated in the event of significantly impaired renal drainage or poor renal growth.
UPJ obstruction is defined as an obstruction of the flow of urine from the renal pelvis to the proximal ureter. The resultant back pressure within the renal pelvis may lead to progressive renal damage and deterioration.
UPJ obstruction presents most frequently in childhood, but adults and elderly individuals can also present with a primary obstructive lesion. In adults, other etiologies for ureteral obstruction must be considered, including stones, ureteral compression due to extrinsic processes, retroperitoneal fibrosis, and other inflammatory processes.
Epidemiologic features of UPJ obstruction are as follows:
Possible etiologies for UPJ obstruction include the following:
All of the above abnormalities impair drainage of urine from the kidney into the ureter, resulting in elevated intrarenal back pressure, dilatation of the collecting system, and hydronephrosis.
Scanning electron microscopy studies using 3-dimensional techniques have shown that normal elasticity and distension of the renal pelvis are impaired secondary to rigid collagen bundling. Increased collagen deposition between smooth muscle cells result in wider cell-to-cell and nerve-to-cell distances. Neural depletion has also been reported. In addition, immunohistochemical studies have shown decreased neuronal markers and nerve growth factors within the smooth muscle layer, thus impeding peristalsis.
In the rat model, acute obstruction resulted in increased levels of angiotensin 11 and increased TGF-β expression, resulting in pathological deposition of extracellular matrix, which may be one mechanism that leads to obstruction.
Neonates mayho present with hydronephrosis. Older children may present with urinary tract infection (UTI), a flank mass, or intermittent flank pain secondary to a primary UPJ obstruction. Hematuria may also be a presenting sign if it is associated with infection.
Adults with UPJ obstruction can present with various symptoms, including back and flank pain, UTI, and/or pyelonephritis. A detailed history may reveal that the pain correlates with periods of increased fluid intake or ingestion of a food with diuretic properties (ie, Dietl crisis).
The goals in treating patients with ureteropelvic junction (UPJ) obstruction are to improve renal drainage and to maintain or improve renal function.
As mentioned above, dilatation of the intrarenal collecting system or hydronephrosis does not necessarily imply obstruction. Specifically in children, renal pelvic dilatation should be monitored with serial imaging to assess for changes in dilatation, renal parenchymal thickness and/or the presence of scarring, and function. Surgical repair is indicated upon a significant differential on serial imaging or progressive deterioration of renal function.
Using this algorithm, patients with hydronephrosis are monitored closely with renal ultrasonography and nuclear medicine renography every 3-6 months. Similarly, in adults, repair is recommended if nuclear medicine renal scan or intravenous pyelography (IVP) reveals ureteral obstruction.
The evaluation of an obstructed ureteropelvic junction (UPJ) requires information about ureteral and surrounding anatomy, renal position and ectopy, associated vasculature, and renal function. Prior to surgical intervention, the surgeon frequently evaluates for renal position/ectopy, mobility, and UPJ anatomy, such as high-insertion variants versus annular stricture variants.
The major vascular supply of the UPJ comes from branches of the renal artery. These vessels usually lie in an anteromedial location in relation to the proximal ureter. Aberrant polar vessels may also be associated with the renal pelvis, causing compression and obstruction of the collecting system. These vessels arise from either the renal artery from a position proximal to the main intrarenal branching site or directly from the aorta. They can surround the UPJ and can be associated with obstruction, or they may be aberrantly positioned secondary to increasing hydronephrosis.
Intraluminal sonogram demonstrating the renal vein surrounding the ureteropelvic junction and causing extrinsic compression and obstruction.
An endopyelotomy refers to an endoscopic incision of the UPJ, performed to create a more funneled drainage system and to bring the UPJ more dependent or caudad below areas of pathology.
The vascular anatomy at the UPJ becomes crucial during an endopyelotomy. The renal collecting system may be accessed percutaneously (antegrade) or in a retrograde fashion via passage of a ureteroscope through the urethra, bladder, and ureter in order to access the obstruction and to perform an incision. While most associated UPJ vessels lie in the anteromedial plane, accessory vessels may lie posteriorly or laterally. If all endoscopic incisions are made in the posterior-lateral plane, intraoperative hemorrhage may occur. For this reason, a comprehensive vascular evaluation with intraoperative endoluminal ultrasonography, preoperative CT scanning, or MRI with vascular reconstruction is recommended prior to this form of treatment.
CT scan without contrast demonstrating severe left-sided hydronephrosis secondary to ureteropelvic junction obstruction.
CT scan with intravenous contrast demonstrating pooling of contrast and delayed excretion of contrast from a left-sided ureteropelvic junction obstruc....
Multidetector CT scanning with 3-dimensional reconstruction can be particularly helpful in establishing the anatomy of UPJ obstruction, revealing an intrinsic or high-insertion UPJ. Crossing vessels and their relationship to the ureter of the UPJ can also be evaluated. The location of these vessels and their possible contribution to renal obstruction can help the surgeon clinically decide whether endopyelotomy, open pyeloplasty, or laparoscopic pyeloplasty would be the most effective treatment modality.
When an open or laparoscopic pyeloplasty is performed, an accurate understanding of the vascular anatomy allows the surgeon to preserve the accessory renal vessels and to redirect them if the surgeon feels that they contribute to the obstruction. If an endopyelotomy is planned, this information can guide the surgeon in directing the endopyelotomy incision away from crossing vessels. CT scanning in combination with 3-phase and 3-dimensional contrast imaging yields a reported sensitivity of 75%-97% in revealing crossing vessels. El-Nahas et al reported that CT scanning yielded a sensitivity of 97%, specificity of 92%, and accuracy of 96% in detecting crossing vessels associated with UPJ obstruction.
Retrograde pyelography at the time of surgery is often used to estimate the length of the stricture and the amount of pelvis/ureter that needs to be excised at the time of the pyeloplasty to create a dependent funnel.
All patients with possible ureteropelvic junction (UPJ) obstruction should be evaluated with the following laboratory studies:
Neonates who present with hydronephrosis should be fully evaluated with voiding cystourethrography (VCUG; to rule out vesicoureteral reflux) and renal ultrasonography (see image below) soon after birth. These patients should also be placed on prophylactic antibiotics (amoxicillin 15 mg/kg) to prevent urinary tract infections (UTIs), especially while diagnostic imaging is being performed.
Intraluminal sonogram of ureteropelvic junction obstruction demonstrating multiple crossing vessels.
If renal ultrasonography demonstrates hydronephrosis without reflux on VCUG, a diuretic renal scan (mercaptotriglycylglycine [MAG-3], diethylenetriamine [DTPA], or dimercaptosuccinic acid [DMSA]) should be performed to quantify relative renal function and to define the extent of obstruction. Renal ultrasonography and VCUG are performed in children with suspected UPJ obstruction.
Historically, intravenous pyelography (IVP) was used to evaluate patients with possible UPJ obstruction. However, in the evaluation of a child with a hydronephrotic kidney, diuretic renography has taken the place of IVP. The benefits of diuretic renography are that iodine-based intravenous contrast is not used, radiation exposure is minimal, and renal function can be better quantified. The disadvantage of the nuclear medicine scan is that insight into renal anatomy is not obtained.
In 1992, the Society for Fetal Urology and the Pediatric Nuclear Medicine Council published guidelines for the "Well-Tempered Diuresis Renogram." Standardized protocols for hydration, radiopharmaceuticals, bladder catheterization, diuretic dose, timing of diuretic, and determination of clearance half-time (T 1/2) have been established.
Functionally significant obstruction is often diagnosed with diuretic renal scanning. The conventional renographic criteria include a flat or rising washout curve after diuretic with T 1/2 of greater than 20 minutes and differential function of less than 40. The differential function is important in determining the need for intervention, especially in asymptomatic patients, and in selecting the appropriate treatment (pyeloplasty vs nephrectomy). Poorly functioning kidneys (< 10%) are often best treated with nephrectomy. Nuclear medicine scanning is also used to assess outcomes after surgical intervention.
The evaluation of ureteral anatomy is difficult with nuclear medicine renal scanning. In adult patients, IVP is more commonly used to outline this anatomy and can often replace nuclear medicine scanning altogether. See the images below.
Intravenous pyelogram demonstrating ureteropelvic junction obstruction with dilatation of the collecting system and lack of excretion of contrast.
Retrograde pyelogram demonstrating ureteropelvic junction obstruction secondary to annular stricture.
Retrograde pyelogram demonstrating ureteropelvic junction obstruction secondary to crossing vessels.
Multidetector computed tomography (CT) scanning with three-dimensional reconstruction may be used to help establish the anatomy of UPJ obstruction and associated vessels. In children, retrograde ureteropyelography is sometimes performed to define the entire ureter just prior to surgical repair. Contrast-enhanced color Doppler imaging is recommended by some as a useful imaging modality for the detection of crossing vessels in patients with UPJ obstruction.
Dynamic contrast-enhanced magnetic resonance urography (MRU) is the latest imaging modality used in assessing UPJ obstruction. In children, this study offers the advantages of no radiation exposure and excellent anatomical and functional details with a single study. The study also provides details of renal vasculature, renal pelvis anatomy, location of crossing vessels, renal cortical scarring, and ureteral fetal folds in the proximal ureter.
Recent criteria for diagnosis of UPJ obstruction on MRU include fluid levels on delayed contrast-enhanced scans and the presence of swirling contrast material on the dynamic images. MRU using a time-resolved, data-sharing three-dimensional contrast-enhanced technique can demonstrate ureteral peristalsis and permits quantification of ureteral peristaltic frequency.
Contrast-enhanced magnetic resonance angiography (MRA) had a sensitivity of 85%, a specificity of 80%, and a positive predictive value of 0.8 for the diagnosis of aberrant and obstructing renal arteries in a retrospective study of 19 pediatric patients with UPJ obstruction.
When the workup results are equivocal, a Whitaker antegrade pressure-flow study may be performed to further evaluate for UPJ obstruction. This test begins with the placement of a small-diameter nephrostomy tube through the back and directly into the kidney. Dilute contrast medium is instilled, and the intrarenal collecting system is pressure-monitored. Under fluoroscopy, the UPJ is assessed and drainage through this segment is defined.
While function cannot be assessed, relative resistance and pressure within the renal pelvis can be measured. High intrarenal pressures define obstruction, while low pressures in the presence of hydronephrosis are consistent with normal variance. This is particularly useful in large dilated systems in which the renal pelvis must be completely full prior to drainage assessment. In this setting, nuclear medicine scanning can yield false-positive results.
In children with ureteropelvic junction (UPJ) obstruction, medical therapy is focused on maintaining sterile urine and assessing renal function and the degree of hydronephrosis. Typically, when imaging studies reveal an incomplete obstruction, the patient is monitored with routine renal ultrasonography and nuclear medicine renography. Currently, no available medical therapy is capable of reversing UPJ obstruction in either adults or children.
Initially, most children are treated conservatively and monitored closely. Intervention is indicated in the event of significantly impaired renal drainage or poor renal growth. The accepted criteria for intervention in infants and children include clearance half-time (T 1/2) greater than 20 minutes, differential function less than 40%, and ongoing parenchymal thinning with or without contralateral compensatory hypertrophy. Intervention is also indicated in those with pain, hypertension, hematuria, secondary renal calculi, and recurrent urinary tract infections.
Surgical intervention to treat an obstructed UPJ is warranted, especially upon deterioration of renal function. The principles of surgical repair, as initially described by Foley, include the following:
In children, the procedure of choice is an Anderson-Hynes dismembered pyeloplasty. The approach may be performed through a flank, dorsal lumbotomy, or anterior extraperitoneal technique. Laparoscopy has gained increasing acceptance in pediatric surgery and is often used to perform pyeloplasties in children. In many cases, laparoscopic pyeloplasty is technically unfeasible in very small children and infants because of space constraints.
Using this method, the obstructed segment is completely resected, with reanastomosis of the renal pelvis and ureter in a dependent funneled fashion. The decision of whether to use a ureteral stent transiently during the initial healing process is based on the personal preference of the surgeon. The success rate of dismembered pyeloplasty for treating an obstructed UPJ exceeds 95%.
Laparoscopic pyeloplasty offers a minimally invasive treatment option that may be used in patients with either primary or secondary UPJ obstruction and is emerging as a new criterion standard in the treatment of UPJ obstruction. Success rates are comparable with those of open pyeloplasty procedures, and some studies have shown that laparoscopy offers the advantages of decreased morbidity, shorter hospital stay, and quicker recovery. Laparoscopic pyeloplasty is a technically demanding procedure that generally requires significant laparoscopic experience. Robotic-assisted laparoscopic pyeloplasty has become increasingly popular as the robots have become more prevalent. A small intrarenal pelvis is a relative contraindication to laparoscopic pyeloplasty.
Endoscopic treatment alternatives include an antegrade or retrograde endopyelotomy, which is an endoscopic incision performed through the obstructing segment.
Prior to incising a UPJ obstruction, intraluminal ultrasonography or another imaging study is recommended to evaluate adjacent ureteral vasculature. Endoluminal ultrasonography is particularly useful in evaluating an obstructed UPJ because it allows for complete real-time evaluation with specific attention to the presence or proximity of blood vessels prior to an endoscopic incision. It is also useful in defining the ureteral anatomy and in directing the incision technique in order to maximize the surgical outcome.
An endopyelotomy incision is performed through the area of obstruction with a laser, electrocautery, or endoscopic scalpel. Most surgeons dilate the newly incised area with a balloon catheter to help ensure a complete incision. This is followed by prolonged ureteral stenting, for a period of 4-8 weeks. The stent acts as internal scaffolding during healing and maintains renal drainage. Success rates with the percutaneous and ureteroscopic endopyelotomy are 80-90%.
When open pyeloplasty fails, endopyelotomy is particularly useful, even in the pediatric population.
In patients who have a suboptimal result from endopyelotomy, repeat incision can be performed with success. Traditional open or laparoscopic pyeloplasty is also indicated after failed endopyelotomy.
Of the open surgical repairs used to treat UPJ obstruction, the Anderson-Hynes dismembered pyeloplasty is particularly useful for the high-insertion variant. The benefit of this procedure is complete excision of the diseased segment of ureter and reconstruction with healthy viable tissue.
The Foley Y-V plasty is also useful for the high-insertion variant but cannot be used if transposition of a lower-pole vessel is needed.
Endopyelotomy for high-insertion UPJ obstruction is patterned after this open surgical procedure but is contraindicated in the presence of a crossing posterior or lateral vessel.
Spiral and vertical flaps (eg, Culp and DeWeerd, Scardino and Prince) are useful when a long-strictured segment of diseased ureter is encountered. With these procedures, the proximal ureter is re-created with redundant renal pelvis that is tubularized.
Ureterocalicostomy, ie, anastomosis of the ureter to a lower-pole renal calyx, is usually reserved for failed open pyeloplasty when no extrarenal pelvis and significant hilar scarring are present. With this procedure, the ureter is sutured directly to a lower pole calyx after a modest partial nephrectomy is performed to remove parenchyma in the area of anastomosis.
Endopyelotomy is a reasonable option in patients with mild-to-moderate hydronephrosis and reasonably good renal function. The stricture should be short (< 1.5 cm), and no crossing vessels should be defined on preoperative or intraoperative imaging (ie, intraluminal ultrasonography). Endopyelotomy may be the preferred option in patients in whom prior pyeloplasty has failed. Antegrade and retrograde approaches are equally efficacious.
Reported by Gill et al from the Cleveland clinic in 2002, endopyeloplasty essentially consists of horizontal suturing of a standard vertical endopyelotomy incision performed through a percutaneous tract via a 26F nephroscope. Indications for endopyeloplasty include short-segment UPJ obstruction, an absence of crossing vessels, and an absence of prior surgery in the UPJ. Endopyeloplasty yields results comparable to those of endopyelotomy, but additional studies are needed for validation.
This procedure is replacing open pyeloplasty as the criterion standard. Most large series report 95% success rates. Unlike endopyelotomy, laparoscopic pyeloplasty can be offered to patients with severe hydronephrosis, crossing vessels, and long-segment strictures. However, the significant learning curve associated with laparoscopic suturing has limited its widespread use. In skilled hands, the indications for laparoscopic pyeloplasty may be extended to secondary UPJ obstruction, concomitant renal calculi, and anomalous and solitary kidneys. Salvage laparoscopic pyeloplasty is an excellent option with durable long-term outcomes in patients in whom open pyeloplasty has previously failed.
The success rates of transperitoneal laparoscopic pyeloplasty and retroperitoneoscopic laparoscopic pyeloplasty were comparable (96.4% versus 96.6%) during a mean follow-up of approximately 30 months in a prospective study of 112 patients with primary UPJ obstruction, but transperitoneal laparoscopic pyeloplasty was associated with significantly greater postoperative pain, a higher tramadol dose, a higher rate of temporary ileus, and a longer hospital stay. Total operative time was significantly higher for retroperitoneoscopic laparoscopic pyeloplasty.
Robotic assistance is useful for surgeons who are obtaining experience with laparoscopic technique or for rare, complex cases for which suturing is challenging secondary to prior surgery or anatomic variants. The da Vinci robotic surgical system has been used successfully for laparoscopic reconstruction of the collecting system. The advantages of this system include degrees of suturing freedom in a tight surgical field, stereoscopic vision, tremor filtration, and scaling. The results are similar to those of conventional laparoscopic pyeloplasty. In the pediatric population, although only a few published series have addressed long-term outcomes, the short-term data suggest similar success in both traditional open and laparoscopic pyeloplasty, including treatment of the youngest children.[9, 10]
Recently, reports have described early experiences with laparoscopic single-site pyeloplasty, during which pyeloplasty is performed via a single port placed at the umbilicus. Conventional laparoendoscopic single-site (C-LESS) pyeloplasty is technically challenging owing to instrument clashing, loss of triangulation, and difficulty sewing. Adaption of the da Vinci Si robotic surgical platform to laparoendoscopic single-site pyeloplasty appears to reduce the learning curve for this complex procedure. Long-term follow-up with single-site laparoscopic pyeloplasty is not yet available. Improved cosmesis and one large access port scar versus three 5-mm port sites are theoretical advantages with this approach.[11, 12, 13]
The preoperative workup includes the following:
One of the goals of laparoscopy is to mirror open techniques, so most of the principles of surgical repair apply to both. In addition to creating a funnel with dependent drainage, care must be taken to minimize tissue handling and tension on the reconstructed UPJ. Whether to use ureteral stents or nephrostomy tubes after open or laparoscopic repair is based on personal preference.
Endopyelotomy may be performed either antegrade or retrograde, ureteroscopically. A safety guidewire must be placed within the ureter prior to endoscopic incision. Intraluminal ultrasonography or preoperative imaging is essential to define peri-UPJ vascular anatomy.
The endoscopic incision should be performed full-thickness through the UPJ and into perirenal fat with laser energy, electrocautery, or an endoscopic scalpel. To ensure a proper incision, extravasation of contrast should be seen on pyelography during the procedure. The incision is most commonly performed posterolaterally.
Balloon dilation is often performed after the incision is made to ensure completeness. Ureteral stenting for 4-8 weeks after the endoscopic procedure is common, although no consensus exists regarding size and duration of stents.
Risk factors for failure after endopyelotomy include the following:
Prophylactic antibiotic therapy should be given postoperatively. Remove the endopyelotomy stent after 4-8 weeks.
Follow up with renal ultrasonography 1-3 months after surgery. In addition, follow up with IVP or nuclear medicine renal scan 3-6 months after surgery.
Serial renal imaging is recommended for the first year after surgery and should be continued less frequently thereafter if results have normalized.
For patient education information, see Intravenous Pyelogram and Adhesions, General and After Surgery.
Potential complications from open surgical pyeloplasty include UTI and pyelonephritis, urinary extravasation and leakage, recurrent ureteropelvic junction (UPJ) obstruction, or stricture formation. Treatment of urinary leakage is centered around catheter drainage, such as nephrostomy, ureteral stent, or perianastomotic drain, to direct urine away from the perianastomotic tissues and to decrease the risk of postoperative stricture disease.
Specific complications from endopyelotomy include significant intraoperative bleeding if the endoscopic incision is made inadvertently into a major polar vessel, postoperative infection, and recurrence of obstruction. If significant intraoperative bleeding is encountered with hypotension, emergency arteriography and embolization are indicated.
Open and laparoscopic pyeloplasty yield long-term success rates that exceed 95%. The success rate for endopyelotomy approaches 80-90%.
The future of treatment of ureteropelvic junction (UPJ) obstruction will certainly include a broadening of the application of laparoscopic techniques. As laparoscopic pyeloplasty has gained acceptance and the surgical experience increased, the procedure has become shorter. The use of robotic assistance may broaden the application of laparoscopy.