Updated: Jun 25, 2018
Author: Thomas MT Turk, MD; Chief Editor: Bradley Fields Schwartz, DO, FACS 



With the widespread use of contemporary ultrasonographic techniques in the obstetric period, congenital hydronephrosis has become the most common initial presentation of ureteropelvic junction (UPJ) obstruction. Prior to this, infants often presented with an abdominal mass, and children presented with abdominal pain, nausea, and vomiting. Hematuria and urinary tract infections are also not uncommon presenting symptoms.

The application of radiographic studies, according to the pediatric urology paradigm, separates cases of congenital hydronephrosis due to UPJ obstruction from cases caused by other etiologies such as posterior urethral valves, megaureter, and vesicoureteral reflux. See the images below.

CT scan without contrast demonstrating severe left CT scan without contrast demonstrating severe left-sided hydronephrosis secondary to ureteropelvic junction obstruction.
Excretory urogram shows a horseshoe kidney with le Excretory urogram shows a horseshoe kidney with left hydronephrosis.

History of the Procedure

UPJ obstruction is the most common cause of prenatal hydronephrosis, accounting for 80% of the cases. Dismembered pyeloplasty has been the criterion standard surgical therapy for UPJ obstruction. In the 1980s, with the advent of percutaneous access to the kidney, antegrade endopyelotomy was developed as a less-invasive surgical therapy for UPJ obstruction. More recently, with rapid advancements in optics yielding smaller and more functional ureteroscopes, retrograde endopyelotomy has developed as an even more minimally invasive approach to treat UPJ obstruction. In addition, a retrograde approach using a balloon cutting catheter (Acucise) allows treatment of UPJ obstruction using only fluoroscopic guidance. The most recent advancement in treatment for UPJ obstruction is the development of the laparoscopic dismembered pyeloplasty.


Urologic texts define UPJ obstruction as an impediment to urinary flow from the renal pelvis into the ureter, which may result in symptoms or renal damage. The problem that clinicians face with UPJ obstruction is determining when poor drainage of the renal collecting system jeopardizes the future function of the affected kidney and the patient's overall health. The answer to this question drives the urological workup of potential UPJ obstruction and results in the application of surgical techniques to alleviate the obstruction and preserve renal function.



Obstruction of the UPJ is one of the most common congenital abnormalities of the urinary tract. Prior to the proliferation of prenatal ultrasonography, most cases of UPJ obstruction were not detected in the first year of life. The frequency of births with unilateral UPJ obstruction is estimated to be 1 case in 5000-8000 live births, and it is bilateral in 6% of these cases. Studies have indicated that UPJ obstruction is more common on the left side than on the right by a left-to-right ratio of 5:2 and that it is has a male-to-female ratio of 5:2. Another study found bilateral UPJ obstruction in 32 of 89 cases. This same study found that the diagnosis was made prenatally in 74 of 89 cases and that most patients diagnosed postnatally presented with an abdominal mass.

Currently, the vast majority of UPJ obstructions (90%) are detected with prenatal ultrasonography. As many as 80% of children identified with prenatal hydronephrosis have no signs or symptoms of their urologic abnormality after birth. An epidemiological study of 11,986 pregnant women who underwent prenatal ultrasound evaluations demonstrated that the overall frequency of congenital abnormalities is 0.5% and that urinary tract abnormalities represent 50% of these cases.[1] Furthermore, others have estimated that the etiology of prenatal hydronephrosis is UPJ obstruction in 50-67% of the cases. Taken together, this suggests that each mother who undergoes prenatal ultrasound examination has a 0.2-0.4% chance of having a neonate with hydronephrosis and these children have a 50% chance of eventually having the diagnosis of UPJ obstruction after birth.

UPJ obstruction is associated with a number of anomalies. A known association exists between UPJ obstruction and horseshoe kidneys.[2] UPJ obstruction has also been found to occur in 17 of 82 patients with ectopic kidneys. A strong relationship also exists between UPJ obstruction and nephrolithiasis.[3] One study found a 20% incidence rate of stones in patients with UPJ obstruction. Finally, no strong evidence exists indicating a hereditary pattern. Only one study has suggested that UPJ obstruction has a genetic etiology,[4] and thus, most cases are believed to be spontaneous in nature.


The etiologies of UPJ obstruction are numerous and are classified on an anatomic basis as either extrinsic or intrinsic. Intrinsic causes are inherent to the development and anatomy of the UPJ itself, while extrinsic causes are exterior to the UPJ. Additionally, UPJ obstruction can be classified as primary and secondary. Primary UPJ obstruction is thought to be due to developmental anomalies of the UPJ, while secondary UPJ obstruction is due to other causes, including previous surgery, recurrent stone passage, or infection and vesicoureteral reflux.

Because the pathophysiology is enigmatic, the etiologies of UPJ obstruction are classified on an anatomic basis. Intrinsic etiologies are primarily due to insertional anomalies or functional abnormalities such as an aperistaltic section of smooth muscle. Studies have demonstrated abnormal collagen architecture within the stenotic UPJ.

Another intrinsic etiology that has been described is tissue valves forming mucosal folds and ureteral polyps that may be due to anatomical abnormalities. As first proposed in 1894 by Fenger, these anatomic anomalies may obstruct the ureter at the UPJ in a ball-valve fashion during periods of diuresis.

Insertional anomalies are described as cases in which the ureter inserts into the renal pelvis at a location that is not the most dependent. This prevents efficient drainage of the pelvis during periods of diuresis. However, whether this is the cause or the result of UPJ obstruction is not clear. Because the kidney is not fixed, except by its pedicle, UPJ obstruction can possibly cause dilation of the pelvis, resulting in distortion of the normal renal position and making the ureter appear to insert in an anomalous location. On the other hand, faulty embryogenesis of the renal unit may be the cause of the anomalous ureteral insertion. Some physicians have classified this cause as extrinsic because the pattern of volume-flow relationships across the UPJ is similar to the pattern of other extrinsic etiologies.

Extrinsic etiologies of UPJ obstruction result from lesions that are anatomically exterior to the UPJ itself. These include aberrant or accessory blood vessels, scars from previous surgery, scarring from nephrolithiasis or infection, and other secondary causes such as vesicoureteral reflux.

At the time of surgical repair, accessory vessels to the lower pole of the kidney or early branching of the segmental artery to the lower pole have been found to be associated with cases of UPJ obstruction. Because these vessels pass anterior to the ureter, distension of the pelvis during diuresis has been hypothesized to possibly cause the pelvis to displace anteriorly and hang over these vessels, which produces a kink in the ureter. This kink worsens as the process repeats itself, and the pelvis becomes progressively more hydronephrotic as the result of the developing UPJ obstruction.

Previous surgery, nephrolithiasis, or infections that cause scars and fibrosis around the UPJ and resultant obstruction may also be extrinsic etiologies that trigger UPJ obstruction by the formation of bands of tissue that compress the ureter. Differentiating this from an intrinsic cause may be difficult because a UPJ obstruction may feasibly develop adhesions and scars from the UPJ obstruction, the stone disease, and infections that may follow.


The cause of most intrinsic (or primary) UPJ obstruction likely relates to the embryological development of the urinary tract. During the fifth week of gestation, the ureteric bud forms from the wolffian duct and invades the metanephric blastema to begin renal differentiation. The nephrons, in turn, induce the ureteric bud to further divide and branch, leading to the formation of the collecting system (including the UPJ).

The aberrations of this developmental process must cause primary UPJ obstructions. For example, during development, the ureter is believed to become solid and then recanalize later. This is thought to occur mostly at the mid ureter. Incomplete recanalization has been speculated to possibly lead to UPJ obstruction. Additionally, smooth muscle differentiation begins in the bladder at 7 weeks' gestation and reaches the upper ureter by approximately the 16th week. An abnormality in smooth muscle development may lead to a section of ureter that does not appropriately contract and, thus, also to primary UPJ obstruction due to poor peristalsis.

The notion that vesicoureteral reflux can lead to progressive pelvic dilation and, eventually, UPJ obstruction, is logical. Although an association exists between UPJ obstruction and vesicoureteral reflux, no causal relationship has been identified. In a large retrospective review, no increased risk of UPJ obstruction was associated with all grades of vesicoureteral reflux. A 5-fold increased risk of UPJ obstruction existed in patients identified to have grade 5 reflux. The same review demonstrated that of patients with vesicoureteral reflux, only 3.6% also had UPJ obstruction. This small percentage does not support vesicoureteral reflux as a causative etiology of UPJ obstruction. Moreover, the same review demonstrated that when UPJ obstruction is repaired prior to the repair of vesicoureteral reflux, the UPJ obstruction does not recur. If vesicoureteral reflux were a causative etiology of UPJ obstruction, this would not be the case.


UPJ obstruction occurs most often in children but may present in persons of any age. The clinical presentation of UPJ obstruction has changed dramatically because of the widespread proliferation of prenatal ultrasonography. Prior to this change, most children presented with an abdominal mass or urosepsis. In this age of ubiquitous prenatal ultrasound, the vast majority of patients with UPJ obstruction present with prenatal hydronephrosis.

Clinical symptoms of UPJ obstruction later in life include urosepsis, failure to thrive, flank pain or mass, and hematuria. As first described by Dietl, the episodes of flank pain, nausea, and vomiting may manifest during periods of rapid diuresis with large volumes of liquid intake (so-called Dietl crisis).[5] This may only manifest after drinking liquids that promote a brisk diuresis such as beer or coffee.

In adults, one study demonstrated that the most common presenting symptoms are flank pain (77%), nephrolithiasis (20%), microscopic hematuria (16%), history of pyelonephritis (14%), gross hematuria (9%), decreased renal function (9%), and gastrointestinal symptoms (5%). Hypertension may also be a rare presenting symptom.


Once the diagnosis of ureteropelvic junction (UPJ) obstruction has been made, management of depends on the severity of the case. Indications for dismembered pyeloplasty or any other operative therapy are variable. Most clinicians consider the presence of symptoms from the obstruction, such as recurrent flank pain, nausea, and vomiting, to be indications for interventions. Other indications include recurrent urinary tract infections, pyelonephritis, ipsilateral nephrolithiasis, and deterioration in renal function.


While performing an antegrade endopyelotomy, the inability to pass a guidewire through the strictured area is a contraindication to endopyelotomy. Additionally, a stricture longer than 2 cm is generally a contraindication to endopyelotomy.

Some authors believe a crossing vessel is a contraindication to endopyelotomy because success rates are reportedly lower and bleeding complications higher. However, others have challenged these contentions and believe that if the incision is performed in a true lateral position, endopyelotomy is safe and has an acceptable success rate even in the presence of a crossing vessel.

Uncorrected coagulopathy is a contraindication to surgical repair, and thus, referral to an internist or hematologist would be appropriate before undertaking surgical treatment.



Laboratory Studies

See the list below:

  • Laboratory studies in the evaluation of a patient with a possible or known ureteropelvic junction (UPJ) obstruction include routine serum chemistries with measurement of BUN and creatinine, urinalysis, and urine culture. Kidney function, as indicated by the BUN and creatinine values, may be normal or elevated (indicating impairment of renal function) depending on the function of the affected and contralateral kidney.

  • Prior to surgical repair, obtain a CBC count and coagulation studies as indicated. One would not expect abnormalities in the CBC count directly related to the UPJ obstruction unless kidney function is severely compromised or an active infection is present. Measures should be taken to correct any abnormality prior to surgical repair. Abnormalities of coagulation parameters would most likely be unrelated to the UPJ obstruction. Uncorrected coagulopathy is a contraindication to surgical repair, and thus, referral to an internist or hematologist would be appropriate before undertaking surgical treatment.

Imaging Studies

See the list below:

  • Renal ultrasound is usually the first test ordered in children with a urinary tract infection. Also, it is often obtained in combination with an abdominal ultrasound in adults with abdominal pain of unclear etiology.

    • Regardless of the indication for renal ultrasonography, the findings of moderate-to-severe hydronephrosis of the renal pelvis and calyces without concomitant hydroureter are indicative of UPJ obstruction.

    • If the UPJ obstruction has existed untreated for some time, a thin renal parenchyma may also be apparent.

  • In the past, the primary study obtained in adults with a clinical presentation suggestive of renal obstruction has been the intravenous pyelogram (IVP).

    • In a patient with UPJ obstruction, the initial finding from an IVP is a delayed nephrogram that may persist for 24 hours or longer.

    • Later images demonstrate gradual filling of the collecting system up to the level of obstruction of the urinary tract. The time delay to this opacification is directly proportional to the degree of obstruction.

    • Additionally, the amount of hydronephrosis correlates to the completeness and duration of the UPJ obstruction.

    • Other findings from an IVP indicative of UPJ obstruction include pyelosinus extravasation and pyelovenous backflow. Pyelosinus extravasation at a ruptured fornix can occur and may correlate with improvement in a patient's symptoms, although the obstruction itself may not have resolved. Pyelovenous backflow may also occur during an acute episode of UPJ obstruction.

  • An abdominal and pelvic CT scan with and without contrast is often the first imaging study obtained in adults who present with abdominal or flank pain because of the speed and efficacy at establishing both nonurologic and urologic causes of such pain.

    • Although it is not the first-line test for the diagnosis of UPJ obstruction, the images from a contrast CT scan are analogous to the images from an IVP of a patient with UPJ obstruction.

    • The noncontrast images demonstrate hydronephrosis without hydroureter and may also demonstrate decreased renal size and parenchymal thickness.

    • If intravenous contrast is administered, the affected kidney usually demonstrates delayed cortical and excretory phases, which correlate to the delayed nephrogram and excretory phases of an IVP.

    • The UPJ obstruction is often demonstrated by the marked delay of the passage of contrast from a hydronephrotic renal pelvis proximally to a nondilated distal ureter.

    • The severity of a UPJ obstruction may prevent any enhancement of the affected kidney during the time of the CT scan. In this instance, a delayed radiograph of the kidneys, ureters, and bladder many hours later may also demonstrate the UPJ obstruction.

    • The presence of crossing vessels, an extrinsic cause of UPJ obstruction, may also be apparent on the contrast images of a CT scan. Three-dimensional reconstruction of the CT scan for clarification of the vascular anatomy is of particular value when preoperatively evaluating anomalous renal units such as horseshoe kidneys.

  • Although not widespread as yet, the use of magnetic resonance imaging to diagnose and direct therapy of UPJ obstruction will likely increase in the future.

    • Magnetic resonance urography (MRU) offers advantages over more conventional imaging modalities because it does not use ionizing radiation and its contrast agents do not cause allergic reactions.

    • Further, MRU has recently been demonstrated to have a very high sensitivity for helping detect UPJ obstruction.

    • Magnetic resonance angiography is also a useful method to help evaluate for the presence of a crossing vessel at the UPJ, which is an important consideration during endoscopic approaches to the repair of UPJ obstruction.

  • The premier radiographic test to confirm the diagnosis of UPJ obstruction is a diuretic renogram. This study entails the administration of a radiopharmaceutical tracer such as technetium Tc 99m mercaptoacetyltriglycine (MAG-3) or technetium Tc 99m diethylenetriaminepentaacetic acid (DTPA).

    • The concept of a "well-tempered" renogram involves adequate patient hydration with a combination of oral and intravenous fluids, as well as bladder catheterization for continuous drainage throughout the study.

    • The MAG-3 diuretic renogram is the criterion standard test because the agent is secreted by the renal tubules. This enables an interpretation of both the relative function of each kidney and the presence of any urinary tract obstruction, including UPJ obstruction

    • The DTPA diuretic renogram findings can also lead to a diagnosis of UPJ obstruction, but this agent does not measure tubular function because it is only filtered at the glomerulus and not secreted by renal tubules. Thus, no determinations can be made regarding relative renal function.

    • Additionally, conditions that inhibit the glomerular filtration rate, such as the renal immaturity of neonates or other nephropathies (eg, diabetic nephropathy), may make interpretation of DTPA renogram findings difficult.

    • As implied by its name, a diuretic agent, such as furosemide, is administered during the study. Furosemide is a loop diuretic, with peak effect occurring 15-18 minutes after administration. Although the exact regimen may vary by institution, the classic well-tempered renogram involves the administration of the diuretic agent 20 minutes after the radiopharmaceutical agent is administered.

    • Under this protocol, the initial images and the corresponding tracer counts indicate relative renal function. In unobstructed systems, the secretion and passage of MAG-3 to the bladder is visualized. In an obstructed urinary tract, such as in UPJ obstruction, the secretion and passage of the tracer is delayed.

    • At 20 minutes, the furosemide is administered and further images are obtained.

      • If the tracer clears with the induced diuresis, obstruction can be excluded.

      • If the tracer does not clear, then the images demonstrate continued holdup of the tracer.

      • The corresponding renogram curve also demonstrates the poor clearance of the tracer from the renal pelvis.

      • From these curves, the reaction half time (t1/2) of the clearance of the pharmaceutical tracer can be determined.

      • The upper limit of normal t1/2s has been determined to be either 10 or 15 minutes.

      • Obstructed systems have t1/2s greater than 20 minutes.

      • Systems with t1/2s between 10 and 20 minutes are deemed indeterminate.

  • Although not necessary to establish the diagnosis of UPJ obstruction, retrograde pyelograms and antegrade pyelograms may both help confirm the presence of obstruction.

    • An antegrade pyelogram may be obtained if the patient presented with an infection that required nephrostomy tube placement. Once the infection has cleared, the administration of contrast through the nephrostomy tube demonstrates the same hydronephrotic collecting system and UPJ obstruction that is seen on IVP findings.

    • Similarly, a retrograde pyelogram demonstrates similar findings. Retrograde pyelography is often performed immediately prior to the definitive repair of a UPJ obstruction in the operative suite to help confirm the site of obstruction and to help rule out any other concomitant obstruction that may be present in the urinary tract.

Diagnostic Procedures

See the list below:

  • In those cases that are indeterminate, a Whitaker test may be appropriate to establish the diagnosis of UPJ obstruction. The idea of the test is that obstruction produces a constant impediment to the flow of urine that requires an elevated pressure gradient to drive these higher flow rates. Therefore, the test attempts to measure this elevated pressure gradient.

    • The Whitaker test requires a nephrostomy tube and the ability to simultaneously measure intrapelvic and cystometric pressures.

    • Once these devices are present, fluid is administered via the nephrostomy tube at a pressure sufficient to establish a flow rate of 10 mL/s, and the resulting pressure gradient between the renal pelvis and the bladder is measured.

    • Whitaker proposed ranges of normal pressure differential as high as 12 cm water and obstructive pressure differentials greater than 20 cm water.

    • Although this test is helpful, it frequently is not obtained in clinical practice because it is highly invasive and often requires anesthesia.

Histologic Findings

The histologic findings at the UPJ can be variable, depending on the etiology of the obstruction. In general, derangement of the normal architecture is thought to exist with an increase in collagen, atrophy, or abnormal arrangement of smooth muscle cells and aberrant innervation. The net result of the changes can result in a functional, but not a structural, obstruction. The abnormal segment can lack the normal peristaltic ability of the ureter and produce the normal passage of urine across the narrowed segment.



Medical Therapy

No medical therapy is available for the treatment of ureteropelvic junction (UPJ) obstruction. Conservative treatment, ie, watchful waiting, is reasonable in situations in which the obstruction is asymptomatic, no evidence in deterioration of renal function exists, and the patient is free from recurrent infections or nephrolithiasis. Conservative treatment may be particularly appropriate in selected children with asymptomatic UPJ obstruction because the obstruction may regress as the child grows.

Of course, if the clinician chooses expectant management, prophylaxis against urinary tract infections that may develop as a result of UPJ obstruction is appropriate. Prophylaxis includes appropriate antibiotics and drainage of the collecting system as indicated. UPJ obstruction may resolve spontaneously in a substantial portion of children.

Surgical Therapy

Open pyeloplasty

Open pyeloplasty remains the criterion standard for the treatment of UPJ obstruction. Although many variations exist in the methodology, this procedure typically involves the surgical excision of the narrowed segment of the UPJ and performance of a spatulated reanastomosis of the renal pelvis to the ureter. If significant dilation of the renal pelvis occurs, it is often reduced in size by trimming off redundant tissue, and then it is tailored in such a fashion that it funnels down towards the anastomosis. If an accessory or aberrant vessel exists near the UPJ, the anastomosis is positioned anterior to the vessel.

An open pyeloplasty can be performed through a variety of incisions but is most likely performed through an extraperitoneal flank incision. Depending on the surgeon's preference and the function of the kidney postoperatively, a nephrostomy tube is occasionally left in place, or, more often, a ureteral stent that passes from the renal pelvis to the bladder is placed. Some surgeons leave a drain near the anastomosis; this is removed postoperatively when the output becomes minimal. The rationale behind this is to help detect fluid leakage from the anastomosis and to prevent its accumulation in the retroperitoneum. If a drain is left, it is usually removed after the patient's bladder Foley catheter is removed and after trial of having the nephrostomy tube (if present) clamped to ascertain that neither maneuver will increase drainage from the anastomosis.

The advantages of this operation include excellent exposure of the UPJ, familiar anatomy for essentially all urologists, the ability to tailor the renal pelvis as needed, and the performance of a watertight anastomosis. The disadvantages include the large surgical incisions and the associated postoperative pain and convalescence.

Laparoscopic pyeloplasty

Since it was first reported in 1993 by Schuessler and associates,[6] the laparoscopic approach to pyeloplasty has continued to gain popularity. The procedure closely mimics the steps of the open approach with adherence to identical surgical principles. It can be performed though either a transperitoneal or retroperitoneal route, depending on surgeon preference and patient factors such as obesity and previous abdominal surgeries. While a transperitoneal approach is familiar to all surgeons and allows a larger working space, the retroperitoneal approach provides more direct access to the UPJ. As with the open pyeloplasty, the UPJ is excised and a spatulated anastomosis is performed using absorbable suture.

The advantages of the laparoscopic approach include less postoperative pain, a shorter hospital stay, and a more rapid recovery. As with its open counterpart, laparoscopy allows for excision of the strictured segment, reduction pyeloplasty, transposition of the UPJ over crossing vessels, and even extraction of concomitant renal calculi. The primary disadvantage is the advanced skill level required for intracorporeal suturing and knot tying. Although the development of specialized laparoscopic instruments has facilitated these tasks, the technical difficulty of the procedure has limited its widespread adoption.

Robot-assisted laparoscopic pyeloplasty

The introduction of the da Vinci robotic surgical system has helped to overcome many of the challenges imposed by laparoscopy. Robotic surgery is similar to traditional laparoscopic surgery in that instruments are introduced into the body through several small incisions and manipulated under video guidance. Unlike conventional laparoscopy, in which the surgeon's hands are directly linked to the instruments, in robotic surgery, the surgeon's movements are made in a console that is remote from the patient and translated by the robotic arms.

The advantages provided by the robot include a magnified 3-dimensional view, increased articulation with 6° of freedom to mimic wrist movements, tremor reduction, and motion scaling. These make intracorporeal suturing less formidable and more efficient, giving more surgeons the tools necessary to perform a minimally invasive pyeloplasty. Thus, robotics is rapidly becoming the preferred approach to pyeloplasty for an increasing number of surgeons.

A retrospective cohort study by Varda et al that included data from 11,899 pyeloplasties from 2003 to 2015 reported that 75% were open, 10% laparoscopic and 15% robotic. Even though the total number of cases decreased 7% annually, robotic pyeloplasty grew 29% annually, accounted for 40% of the cases in 2015 and reduced the likelihood of prolonged length of stay, however, increased likelihood of prolonged operative time.[7]

Percutaneous antegrade endopyelotomy

With the advent of percutaneous techniques for kidney stone removal in the 1970s, adaptation for treatment of UPJ obstruction was a natural extension. Briefly, percutaneous access is established into the kidney through a mid- or upper-pole posterior calyx. The calyx is chosen so that it allows straight access to the region of the UPJ. The nephrostomy tract is dilated, and a working sheath is placed. A variety of instruments can be passed and directed down to the region of the UPJ through this working sheath. Safety guidewires are passed through the region of the UPJ and into the bladder.

A full-thickness incision is made across the strictured segment in a true lateral position. The lateral position is chosen to reduce the likelihood of injury to the renal hilum located medial and anterior or accessory vessels to the lower pole of the kidney located posterior to the UPJ. The incision is extended to approximately 1 cm distal and 1 cm proximal to the strictured area until periureteral fat is seen.

Following this, a ureteral stent is passed down over one of the safety guidewires and positioned so that one end is in the renal pelvis and the other is passed into the bladder. The size and type of ureteral stent used are based on surgeon preference. Many use a standard 7F stent with the length chosen based on the patient's height. However, specifically designed endopyelotomy stents are available. These stents are of changing diameter. The end with the larger diameter (10-14F) is positioned across the region of the endopyelotomy. The stent then tapers to a diameter of 6 or 7F, which is positioned in the bladder. Whether the larger-diameter stent increases the patency of the endopyelotomy remains controversial.

A nephrostomy tube is placed until the urine has cleared and the patient can tolerate having the nephrostomy tube clamped. The ureteral stent is usually left in place for 4-6 weeks and then removed cystoscopically.

This procedure has the advantage of requiring a very small skin incision and relatively rapid postoperative convalescence with minimal pain. Success rates are reported as high as 85%. Disadvantages of this procedure include potential complications of percutaneous access to the kidney, including infection, bleeding, pneumothorax and hemothorax; potential for bleeding at the site of the ureteral incision; and a slightly lower success rate compared to open or laparoscopic pyeloplasty.

Retrograde endopyelotomy

In an attempt to reduce the potential morbidities associated with a percutaneous approach when treating UPJ obstruction, a retrograde approach has been developed. This procedure involves the passage of a ureteroscope through the bladder and into the ureter in a retrograde fashion. The scope is advanced up to the region of the UPJ. Under direct vision, the UPJ is incised through the full thickness using a variety of devices such as electrocautery or laser. The incision is usually carried proximal and distal to the strictured area until periureteral fat is seen. Following incision, a ureteral stent is left in place in a fashion similar to the antegrade approach.

This procedure has the advantage of being minimally invasive; no skin incision is required. It can often be performed in an outpatient setting. Potential disadvantages include slightly lower success rates compared to its open counterpart; the inability to pass the ureteroscope to the region of stricture, thus requiring additional procedures; the discomfort associated with the postoperative stent; and the need for a skilled endoscopist to accurately and safely perform the procedure.

Acucise endopyelotomy

An additional retrograde approach to the treatment of UPJ obstruction has been developed. This technique uses a balloon catheter with a cutting wire. The Acucise catheter is passed in a retrograde fashion over a safety guidewire under fluoroscopic guidance to the level of the UPJ obstruction. The cutting wire of the catheter is positioned so that it traverses the strictured area. The balloon portion of the catheter is inflated with contrast; when the appropriate position is confirmed fluoroscopically, the cutting wire of the catheter is activated, which incises the strictured area. The incision is meant to be of full thickness and usually results in the extravasation of contrast material. Following incision, the Acucise catheter is removed and a ureteral stent is placed. This stent is left in place for approximately 6 weeks to allow reepithelialization of the ureter and then is removed cystoscopically.

This procedure has the advantages that it is relatively easy to perform, can be performed in an outpatient setting, has low patient morbidity, and has overall success rates of approximately 75%. Disadvantages include the reliance on fluoroscopy rather than continuous and direct vision, potential bleeding complications that may require angiographic or other intervention, and the discomfort associated with the indwelling ureteral stent.

Antegrade endopyeloplasty

A modification of the antegrade endopyelotomy is termed an endopyeloplasty. The beginning of this procedure is similar to that of an antegrade endopyelotomy. After establishing percutaneous access to the kidney, the UPJ is incised full thickness, as with a traditional endopyelotomy. The incision is enlarged with laparoscopic Endoshears. The vertical incision is then closed in a Heineke-Mikulicz (horizontal) fashion with a laparoscopic suture device (Sew-Right SR-5, LSI solutions, Victor, New York) placed through the working channel of the nephroscope. The experience with this procedure is limited to only a few large centers; thus, it has not gained widespread acceptance.

Preoperative Details

All patients should have an anatomic study illustrating the extent of the obstruction and a functional study to assess the function of the affected kidney and contralateral kidney. The authors recommend that all patients have a Lasix renal scan prior to surgery to confirm the presence of obstruction and to ascertain function of the affected and contralateral kidney.

Make every attempt to sterilize the urine of any of these patients preoperatively. Check baseline kidney function, hemoglobin values, and bleeding parameters if indicated. Obtain informed consent that lists alternative treatments and potential intraoperative and postoperative complications. Although transfusion after pyeloplasty or endopyelotomy is rare, ask all patients to sign a blood consent preoperatively. Conversion to an open procedure or the need for additional procedures is a possibility with all of the treatments for UPJ and thus should be addressed in detail with the patient preoperatively.

Immediately prior to the procedure, the patient should receive a dose of a broad-spectrum antibiotic such as cefazolin. As an alternative, ampicillin and gentamicin can be given concurrently.

Intraoperative Details

Open pyeloplasty

If the patient's ureteral anatomy has not been defined preoperatively with intravenous urogram (IVU) images, most physicians advocate performance of a retrograde pyelogram prior to the pyeloplasty. Findings illustrate the length of the stricture and help confirm that no evidence of obstruction exists distal to the UPJ. After performance of the retrograde pyelogram, a Foley catheter is placed and the patient is placed in the flank position. The incision used is based on surgeon preference and the patient's particular anatomy, but typically, an extraperitoneal flank or subcostal approach is used.

Following incision and division of the muscles, the peritoneum is swept medially, the kidney is identified, and Gerota fascia is opened. Perinephric fat is cleaned off until the renal pelvis and proximal ureter are completely identified. Control of the renal hilum is generally not necessary. Accessory renal arteries are often identified, supplying the lower pole of the kidney that crosses the ureter at the point of the UPJ obstruction. Make every effort to spare these vessels because ligation can devascularize a segment of kidney.

Once the region at the UPJ is dissected out, holding stitches are placed on the renal pelvis and the ureter distal to the UPJ obstruction. The region of the UPJ is then excised out sharply. Following this, free flow of urine from the renal pelvis should occur. The ureter is often injected with sterile saline to confirm free flow down the remainder (distal portion) of the ureter. Next, the ureter is spatulated laterally at a distance of approximately 1 cm. If the renal pelvis is largely hydronephrotic, it is frequently reduced with the hope of funneling the urine down towards the newly created anastomosis.

The next step is the anastomosis. If an accessory renal vessel is identified, perform the anastomosis anterior to the vessel. Using small absorbable sutures such as 5-0 Monocryl or PDS on a small tapered needle, the anastomosis is performed between the spatulated ureter and renal pelvis.

The first stitch is usually placed in the lateral aspect of the ureter and the lateral most aspect of the renal pelvis. The remainder of the anastomosis is then performed using either interrupted or running sutures. If a ureteral stent is to be placed, it is placed prior to completion of the anastomosis. After performance of the anastomosis, usually a redundant pelvis must be closed. This is usually performed in a running fashion. If a Penrose or a closed-suction drain is placed near the anastomosis, it is brought up through a separate incision. The abdomen is closed in a routine fashion.

Laparoscopic pyeloplasty

Prior to proceeding with pyeloplasty, many surgeons perform retrograde pyelography to more precisely define the stricture length and location and to rule out obstruction distal to the UPJ. A double-J ureteral stent may be placed at this time. The patient is then repositioned on the operating table, and pneumoperitoneum is established. The dissection is begun by mobilizing the colon on the affected side medially by incising along the avascular line of Toldt. The kidney, with overlying perinephric fat, is usually easily identified. Gerota fascia is opened, and dissection is carried down to the level of the kidney.

Once the UPJ is identified, the renal pelvis and proximal ureter are dissected. As with the open pyeloplasty, dissection of the ureter is minimized in an attempt to preserve its blood supply. The strictured region is then excised sharply. At this point, the ureteral stent should be clearly visible. The ureter is spatulated on its lateral aspect, and, if necessary, the redundant renal pelvis is excised. The goal is to place the UPJ in a dependent position to maximize drainage without placing the anastomosis under tension. If a crossing vessel is present and appears to be obstructive in nature, the renal pelvis and ureter may be transposed anterior to the vessel. It is important to preserve accessory arteries because they often supply blood to a significant portion of the kidney, as well as to the renal pelvis and proximal ureter.

Prior to completion of the anastomosis, the proximal end of the double-J stent is passed into the renal pelvis. Most surgeons perform the anastomosis in a running fashion. Lapra-Ty clips may be used to minimize knot tying, and specialized instruments such as the Endostitch device may facilitate suturing. Important principles include the creation of a tension-free watertight anastomosis with preservation of the periureteral blood supply. Once the anastomosis is completed, a closed-suction drain is placed through one of the trocar sites. The pneumoperitoneum is reduced, and the abdomen is exited in the standard fashion. All trocar sites larger than 10 mm are closed in an effort to reduce herniation of abdominal contents through the fascial defect.

Robot-assisted laparoscopic pyeloplasty

The steps of the robotic pyeloplasty are similar to those of a traditional laparoscopic pyeloplasty. Retrograde pyelography and stent placement may be performed initially with the patient in the lithotomy position. However, the specialized instruments used during robotic surgery facilitate antegrade stent placement, leading some surgeons to forego the initial cystoscopic procedure. The patient is then placed in the lateral decubitus position with the ipsilateral kidney superior. Pneumoperitoneum is established with either a Veress needle or the Hasson technique. A 12-mm camera port and two 8-mm robotic ports are placed in a triangular fashion, with the camera in the center. Assistant ports are placed as needed.

After the colon has been reflected medially, the UPJ is mobilized and then divided, taking care to preserve the periureteral blood supply and any accessory lower-pole vessels. Careful manipulation of the proximal ureter may be accomplished by using the redundant UPJ tissue as a handle or with the aid of a stay suture. The redundant pelvis is excised along with the strictured segment, and the ureter is spatulated along its lateral aspect. A running anastomosis is performed over a stent, most commonly with 4-0 polyglactin suture, along the posterior and anterior walls. A drain may be placed near the anastomosis and brought out through one of the port sites, although many surgeons do not routinely leave a drain.

Antegrade endopyelotomy

Ureteral anatomy must be defined. If needed, a retrograde pyelogram is performed. A stricture longer than 2 cm is generally a contraindication to endopyelotomy. The role of a crossing vessel in the region of the UPJ is controversial. Some authors believe a crossing vessel is a contraindication to endopyelotomy because success rates are reportedly lower and bleeding complications higher. However, others have challenged these contentions and believe that if the incision is performed in a true lateral position, endopyelotomy is safe and has an acceptable success rate even in the presence of a crossing vessel.

A Foley catheter is placed at the start of the case. The patient is positioned in a prone position with appropriate padding. Access to the kidney is obtained through either a mid- or upper-pole posterior calyx. This can be performed at the start of the procedure or prior to the endopyelotomy if the interventional radiologist establishes access at the surgeon's hospital. A guidewire is then passed through the calyx, negotiated beyond the UPJ, and continued down into the bladder. The inability to pass a guidewire through the strictured area is a contraindication to endopyelotomy. Then, a second safety wire is usually placed. The nephrostomy tract is dilated using either a dilating balloon or serial dilators.

A working sheath is passed from the skin into the collecting system. A scope is then passed through the working sheath and into the renal pelvis. The renal pelvis is inspected. If any calculi are found, they are treated and removed. The region of the UPJ is then inspected. Contrast material can be injected in an antegrade fashion to further delineate the anatomy. Next, the endopyelotomy is performed.

The authors typically use a cold knife; however, a hot knife (electrocautery or laser) can be used to make the incision. Making the incision in a truly lateral position is critical. This position can be confirmed using a combination of direct visualization and fluoroscopic guidance. The incision is generally begun 0.5-1 cm distal to the obstruction, carried through the strictured area, and continued 0.5-1 cm proximal to the strictured area. The incision should be of full thickness until periureteral fat is visible. Following the incision of the strictured segment, a ureteral stent is placed. The size of the stent depends on surgeon preference. An endopyelotomy stent can be used. The stent is passed down over one of the safety guidewires, and the position is confirmed with fluoroscopy so that one curl is in the renal pelvis and the distal curl is in the urinary bladder.

After confirming satisfactory stent position, the scope is removed and a nephrostomy tube is placed through the working sheath into the renal pelvis. The working sheath is then removed. The nephrostomy tube is generally hooked to gravity drainage, and the patient is recovered from anesthesia.

Antegrade endopyeloplasty

The technique for pyeloplasty is very similar to that of a standard endopyelotomy. Antegrade access is established into the kidney in an upper or midpole calix. The site of obstruction is identified and incised the full thickness, as with a standard endopyelotomy. Laparoscopic scissors are passed through the nephroscope, and the distal edge of the endopyelotomy incision is mobilized. The vertical defect is then closed in a horizontal fashion (Heineke-Mikulicz) using a laparoscopic suture assist device (Sew-Right SR-5, LSI solutions, Victor, New York). A ureteral stent and nephrostomy tube are placed in the standard fashion.

Retrograde endopyelotomy

In this procedure, the patient is placed in the lithotomy position. Retrograde pyelography is performed to help delineate the ureteral anatomy. A guidewire is passed in a retrograde fashion up the ureter and curled in the renal pelvis. A second safety wire is then placed. Generally, the procedure is performed using a flexible ureteroscope, although in certain individuals, a rigid ureteroscope can be passed to the region of the UPJ. The scope is passed to the level of the UPJ. Again, the incision is made in a true lateral position. This is critical to reduce the risk of bleeding complications. The strictured segment is incised 0.5-1 cm both proximal and distal to the strictured area. The device used for incision is based on surgeon preference but can include a hook electrode hooked to electrocautery or, more recently, the holmium:YAG laser. The incision should be of full thickness until periureteral fat is visible.

Following the incision, the ureteroscope is removed and a double-J stent is placed in a routine fashion. The position of the proximal curl in the renal pelvis is confirmed, as is the distal curl in the bladder. A Foley catheter is generally placed at least overnight, and the patient is recovered from anesthesia.

Acucise endopyelotomy

This procedure is performed without the passage of an ureteroscope and is essentially performed under fluoroscopic guidance only. With the patient in the lithotomy position, a retrograde pyelogram is performed to help delineate the UPJ anatomy. Next, a safety wire is passed up the ureter, beyond the UPJ, and into the renal pelvis. The Acucise endopyelotomy catheter is then passed over the guidewire and to the region of the UPJ. The cutting-wire portion of the catheter is readily visible on fluoroscopy images. Inflate the balloon portion of the catheter with contrast under fluoroscopic guidance. Identify a clear "waist" (ie, narrowing) in the region of the UPJ. Once this is confirmed, the balloon is then deflated again.

Using fluoroscopic guidance, a true lateral position of the cutting wire is confirmed. The balloon is then reinflated with contrast, and the cutting wire is activated with 75 W of pure cutting current for 5 seconds. With activation of the cutting wire, the waist should immediately disappear. After cutting, the balloon is left inflated for an additional 5 minutes. If extravasation of contrast is identified outside of the collecting system, the balloon is deflated and the Acucise catheter is removed.

If no obvious extravasation is identified, more contrast material is injected in a retrograde fashion to further fill the renal pelvis. If extravasation is still not identified, the catheter can be repositioned and a second incision performed in a similar fashion to the first. Perform no more than 2 cuts. Following removal of the Acucise catheter, a ureteral stent is placed in a routine fashion over the safety wire, under fluoroscopic guidance. The safety guidewires are removed, a Foley catheter is placed, and the patient is recovered from anesthesia.

Postoperative Details

Open pyeloplasty

Following recovery from anesthesia, the patient is generally given ice chips and, perhaps, clear liquids at the end of surgery if they have no clinical evidence of an ileus. If not, liquids are deferred until the following morning. Prompt mobilization of the patient and a pulmonary toilet is maintained postoperatively. Pain is controlled with either a morphine patient-controlled analgesia device or, in some cases, an epidural catheter. Once patients are tolerating a general diet, they are switched to oral pain medication. Antibiotics are continued until the drain is removed. The drain is removed once the output is deemed minimal. The Foley catheter may be removed at any point between the first and fifth postoperative day, and the patient is discharged.

Laparoscopic pyeloplasty/robot-assisted laparoscopic pyeloplasty

Postoperative recovery from laparoscopic procedures is generally quicker than from open surgery. Patients may be allowed to have a clear liquid diet the evening of surgery. Postoperative pain can usually be adequately managed with oral pain medications. The urethral catheter is removed first, usually on postoperative day one or two. If the flank drain output remains low with voluntary voiding, which indicates a water-tight anastomosis, it may be discontinued. Many surgeons, especially those performing minimally invasive pyeloplasty, do not routinely leave a drain. In this instance, the Foley catheter may be left in place for 3-5 days to reduce the transference of high voiding pressures to the newly created anastomosis. Most patients are discharged from the hospital within 2-3 days. The double-J ureteral stent is removed at 4-6 weeks once the repair has healed.

Antegrade endopyelotomy/endopyeloplasty

After recovering from anesthesia, patients are kept in a regular room. A nephrostomy tube is usually left with open drainage until the urine is free of clots. The tube can then be clamped. If the patient tolerates clamping of the tube without significant pain or fever, the nephrostomy tube can generally be removed. Postoperative pain for this procedure is usually minimal and requires only oral narcotics. Antibiotics are continued until the nephrostomy tube is removed, and patients are usually discharged home with suppressive antibiotics, although the authors are aware that no clinical studies exist that prove the necessity of this approach.

Retrograde endopyelotomy and Acucise endopyelotomy

Recovery from these procedures is usually the fastest compared to the other procedures mentioned. If a Foley catheter is left in place, it is usually removed the next morning, assuming the urine is free of clots. Pain is usually easily controlled with oral pain medicine. Perioperative antibiotics are continued until the following morning. Discharge usually occurs on the morning after surgery, although in some centers, these procedures are performed in an outpatient setting.


Follow-up of UPJ obstruction after the procedure is somewhat dictated by the procedure performed. If an indwelling ureteral stent is left in place, it is usually removed cystoscopically 4-6 weeks after the procedure.

Generally, perform imaging studies approximately 6-8 weeks after the procedure to assess renal function and to help rule out residual obstruction.[8] The authors believe that the Lasix renal scan is the best study to use because it provides an assessment of the function of the kidney and helps establish whether any evidence of obstruction exists. An alternative study is an IVP. Ultrasound is probably not a good procedure because patients can often have residual hydronephrosis without evidence of obstruction.

If patients experience recurrence of flank pain or have evidence of urinary tract infection prior to 6 weeks, consider performing imaging studies earlier. If findings from the initial study at 6 weeks show no evidence of obstruction, monitor patients clinically from that time forward in terms of their symptoms, and obtain routine urinalyses to help detect infection. The authors typically obtain one other imaging study 6 months to 1 year postprocedure to help rule out a silent obstruction from stricture recurrence. Recurrence of the obstruction can occur anytime after the initial surgery; therefore, patients generally require a lifetime of follow-up.

For excellent patient education resources, see eMedicineHealth's patient education articles Blood in the Urine and Intravenous Pyelogram.


Each of the different surgical treatments for the correction of ureteropelvic junction (UPJ) obstruction has potential complications. Recurrent obstruction can develop after any of the techniques described. Specific success rate for the various procedures are described in Outcome and Prognosis.

As with all surgical procedures, a potential for bleeding exists at the time of surgery and in the immediate postoperative period. Adherence to proper surgical technique and proper patient selection should decrease the potential for significant bleeding complications. The endourological techniques of antegrade and retrograde endopyelotomy and the Acucise endopyelotomy are different because bleeding may not be as readily apparent as in the open or laparoscopic pyeloplasty. Adequate monitoring of vital signs, hematocrit measurements when indicated, and the degree of hematuria after the procedure can alert the surgeon to the possibility of significant bleeding.

Urinary tract infection can occur after any treatment for UPJ obstruction. Make every effort to sterilize the urine of patients prior to the procedure. In addition, use preoperative and perioperative antibiotics in all patients. For antibiotic coverage, use broad-spectrum antibiotics with particular emphasis on coverage against gram-negative rod pathogens. A study by Ferroni et al found that the administration of extended prophylactic antibiotics following minimally invasive pyeloplasty showed no significant impact on the rate of urinary tract infection.[9]

Secondary ureteropelvic obstruction

Secondary UPJ obstruction occurs when a previous attempt at surgical treatment has failed. Scar tissue formation due to surgical dissection or to fluid extravasation during endoscopic treatment may present an additional challenge during treatment of secondary UPJ obstruction. Traditionally, the treatment of choice following a previous open repair has been antegrade endopyelotomy, while open pyeloplasty is usually attempted after an initial endoscopic approach has been unsuccessful. Jabbour and colleagues (1998) report an 88% success rate with endopyelotomy following failed open pyeloplasty.[10] Conversely, the success rate of endoscopic treatment of secondary obstruction following a previous attempt at endoscopic management may be as low as 38%.

More recently, centers with considerable experience in laparoscopy have achieved good success rates with secondary laparoscopic pyeloplasty. Sundaram and colleagues (2003) reported an overall success rate of 83% among 36 patients, most of whom had undergone previous endourologic procedures, including 28 who underwent previous cutting balloon retrograde endopyelotomy.[11] Laparoscopic pyeloplasty is certainly a reasonable option following previous attempts at endourologic management. However, more authors are proceeding directly to laparoscopic or robotic pyeloplasty for secondary obstruction after an initial pyeloplasty. Basiri and colleagues (2007) treated 18 patients with laparoscopic pyeloplasty following failed open surgery, with a success rate exceeding 75%.[12]

Outcome and Prognosis

Success rates for the different treatments for ureteropelvic junction (UPJ) obstruction vary depending on a number of factors, including, but not limited, to the degree of obstruction; whether it is a primary or secondary obstruction; the function of the affected kidney; anatomic considerations, such as the presence of crossing vessels; and the expertise of the treating surgeon.

Open pyeloplasty

Often considered the criterion standard for the treatment of UPJ obstruction, open pyeloplasty has success rates consistently greater than 90% based on subjective patient symptoms and objective radiographic evidence.

Laparoscopic pyeloplasty

Although technically more difficult than open pyeloplasty, this technique shares similar success rates with its open counterpart. Success rates range from 88%-100%, with most series citing rates well over 90%. In the largest series to date of 170 patients undergoing dismembered pyeloplasty, Moon and colleagues (2006) report a symptomatic success rate of 96%.[13]

Robotic pyeloplasty

The enthusiasm for robotic pyeloplasty is supported by a mounting body of evidence documenting its efficacy. Several single-center series report symptomatic and radiographic success rates of 94%-100%, and, recently, a multi-institutional review reported that 96% of patients undergoing robotic dismembered pyeloplasty at 3 centers demonstrated resolution of obstruction on imaging studies.[14] In addition, most series report significantly shorter operative times for robotic compared with laparoscopic pyeloplasty.

Antegrade endopyelotomy

The success rates of antegrade endopyelotomy are 75-95%. Different factors contributing to the success or failure include whether the obstruction is primary or secondary, whether high insertion of the ureter into the renal pelvis occurred, the degree of hydronephrosis and the function of the affected kidney, and the presence of a crossing vessel near the UPJ.

Retrograde endopyelotomy

Although this approach is typically considered to have lower success rates compared to an antegrade approach and open or laparoscopic pyeloplasty, it can usually be performed with minimal morbidity and, perhaps, at a lower cost compared to alternative treatments. Success rates are reported to be 70-85%. As with an antegrade approach, anatomic and functional factors affect the overall success rates.

Acucise endopyelotomy

The overall success rate of 75% for Acucise retrograde endopyelotomy is similar to that of the antegrade and retrograde approach. Similar anatomic and functional factors can also affect the success rate of this procedure.

Future and Controversies

The optimal treatment for patients with ureteropelvic junction (UPJ) obstruction is a continuing source of controversy among urologic surgeons. While open pyeloplasty has traditionally yielded the highest success rates, this must be balanced against greater patient discomfort and longer recovery times. Conversely, endopyelotomy is a less morbid approach, with generally lower but potentially acceptable success rates. Standard laparoscopic pyeloplasty combines the minimally invasive aspects while maintaining the effectiveness of open pyeloplasty; however, its technical challenges have limited its use to centers with considerable laparoscopic expertise. The da Vinci robot holds promise as a tool that will allow more surgeons to offer a minimally invasive approach to pyeloplasty.

As evidenced by the development of the laparoscopic pyeloplasty, a trend toward less-invasive approaches for the treatment of UPJ obstruction is certainly occurring. Other methods are being explored that may work as adjuncts to the currently available surgical treatments. The primary reason for failure of the current procedures is the formation of scar tissue composed of collagen at the site of the anastomosis or the site of endopyelotomy. Some investigators are examining the role of collagen inhibitors in animal models to reduce the amount of collagen in an attempt to reduce scarring after treatment.

Other investigators are examining the role of adenovirus to transfect genes to reduce scarring in the ureters of animals with ureteral strictures. While these studies explore adjuncts to the currently available treatments, the ultimate outcome may be the development of less-invasive or noninvasive treatments for UPJ obstruction.