Introduction

Congenital hydronephrosis has become the most common initial presentation of ureteropelvic junction (UPJ) obstruction with the widespread use of contemporary ultrasonographic techniques in the obstetric period. At the initial, 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.

History of the Procedure

The most common cause of prenatal hydronephrosis is UPJ obstruction. Dismembered pyeloplasty has been the criterion standard surgical therapy for UPJ obstruction. 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.

Problem

Working as a barrier to urinary flow from the renal pelvis into the ureter by UPJ obstruction, 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 forces the urological workup of potential UPJ obstruction and results in the application of surgical techniques to alleviate the obstruction and preserve renal function.

Frequency

One of the most common congenital abnormalities of the urinary tract is Obstruction of the UPJ. 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 very low. UPJ obstruction is associated with a number of anomalies. A known association exists between UPJ obstruction and horseshoe kidneys. A strong relationship also exists between UPJ obstruction and nephrolithiasis.

Etiology

As either extrinsic or intrinsic the etiologies of UPJ obstruction are numerous and are classified on an anatomic basis. Intrinsic causes are inherent to the development and anatomy of the UPJ itself, while extrinsic causes are exterior to the UPJ. Additionally, it 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. Another intrinsic etiology that has been described is tissue valves forming mucosal folds and ureteral polyps that may be due to anatomical abnormalities. During periods of dieresis, these anatomic anomalies may obstruct the ureter at the UPJ in a ball-valve fashion. 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. Extrinsic etiologies of UPJ obstruction result from lesions that are anatomically exterior to the UPJ itself. Aberrant or accessory blood vessels, scars from previous surgery, scarring from nephrolithiasis or infection, and other secondary causes such as vesicoureteral reflux are common examples. 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.

Pathophysiology

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. 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. Recanalization which is not complete 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.

Presentation

Most occurrence of UPJ obstruction is found 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. 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). This may only manifest after drinking liquids that promote a brisk diuresis such as beer or coffee.

Indications

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

Contraindications

While performing an antegrade endopyelotomy, the inability to pass a guide wire through the strictured area is a contraindication to endopyelotomy. Additionally, a stricture longer than 2 cm is generally a contraindication to endopyelotomy. Uncorrected coagulopathy is a contraindication to surgical repair, and thus, referral to an internist or hematologist would be appropriate before undertaking surgical treatment.