Description of the condition
Ureteric-pelvic junction obstruction (UPJO) adversely effects kidney development and function. UPJO is defined as impeded normal urine outflow from the renal pelvis to the nearest ureter (Koff 2008). Its incidence is 0.5 to 1/1000 births and is most often unilateral (60% to 80%). Children with UPJO have increased incidence of associated urological anomalies (Karnak 2008).
Unilateral UPJO is the most common cause of pre- and postnatal obstructive uropathy, which can lead to development of chronic kidney disease (CKD) (Mesrobian 2012; Williams 2007). UPJO is generally detected at pre- or neonatal ultrasound screening (Clayton 2012), but before ultrasonographic screening was widespread, it was often detected on investigation of clinical symptoms secondary to urinary outflow obstruction (Sutherland 1997). UPJO aetiology is multifactorial (Chen 2009; Chevalier 2010), and pathophysiology is limited to animal model findings (Chevalier 2010; Thornhill 2007).
Three primary pathophysiologic processes - mural, intramural and extramural changes - are associated with anatomic or functional UPJO (Chen 2009). Mural obstruction is the most common diagnosis, and results from either dysfunctional or adynamic ureteral peristalsis caused by abnormal distribution of smooth muscle, collagen fibres and innervation, or from incomplete re-canalisation during development. Intramural changes, such as fibroepithelial polyps or stones, are rare in children. Extramural anomalies such as crossing vessels, kinks, bands, adhesions, high insertion of the ureter, or abnormal rotation of the kidney can cause intermittent impairment in urine flow with dilatation of the pelvicaliceal system.
The pathogenetic consequences on kidney maturation, growth and histomorphology are dependent on the child's developmental stage when obstruction occurs, and the degree and duration of urinary tract obstruction on the non-obstructed kidney (Rosen 2008; Vaughan 2004).
UPJO evaluation requires kidney ultrasound and scintigraphy (Riccabona 2009). UPJO presents on ultrasound as a dilated renal pelvis without ureter dilatation. It is commonly assessed using the Society for Fetal Urology grading system and the anterior-posterior diameter (APD) of the renal pelvis in the transverse plane (Nguyen 2010). Renal scintigraphy using 99mTc-MAG3 provides useful information on split kidney function and isotope clearance (Riccabona 2009). Administration of diuretics, such as frusemide 0.5 to 1.0 mg/kg body weight, is aimed to differentiate between obstruction and the immediate drainage of non-obstructive urinary tract dilatation caused by a reservoir effect (Riccabona 2009).
Investigations of MRI and proteome analysis from urinary polypeptides have been suggested as promising non-invasive alternatives to diagnose UPJO in the future (Cerwinka 2010; Mesrobian 2010; Muthusami 2013).
Although kidney imaging techniques are often used to investigate need for surgical intervention, they are not good predictors to determine pathophysiological consequences of kidney function (Riccabona 2009).
The changing and dynamic nature of urinary outflow obstruction, individual compensatory processes, and the child's developmental stage at which the obstruction occurs elucidate the clinical variability of consequences on kidney development, function and urodynamics in children with similar degrees of urinary tract dilatation on kidney imaging (Davenport 2013). Therefore, urinary tract dilatation does not necessarily equate to the presence of urinary flow obstruction (Mesrobian 2012).
Description of the intervention
Both surgical and non-surgical interventions are essential therapeutic strategies for children with unilateral UPJO (Csaicsich 2004; Gallo 2009; Mei 2011). There are three main surgical procedures undertaken for the management of children with UPJO:
open approach (such as Anderson-Hynes pyeloplasty)
endoscopic approach (antegrade or retrograde)
The type of surgical approach is determined by factors including the specific anatomical abnormality, the child's age and clinical presentation (Herndon 2009; Williams 2007). Conservative non-surgical wait-and-see strategy with and without prophylactic antibiotics and nephroprotective ACE-inhibitors requires serial kidney ultrasound and scintigraphy imaging to monitor for early kidney deterioration in children with UPJO (Csaicsich 2004; Malki 2012).
How the intervention might work
Surgical intervention aims to resolve obstruction and provide adequate drainage of the affected kidney (Mei 2011; Thornhill 2007; Williams 2007). Although it has been suggested that optimal kidney function improvement results from surgery performed during the first year of life, others argue that delayed surgical intervention offers better outcomes (King 1984). The gold standard of open dismembered pyeloplasty has a reported success rate of 90% to 99% and a 13% complication rate (Williams 2007). Other surgical procedures have varying success (56% to 98%) and complication rates (3.6% to 25%) often resulting from applied techniques and limited experience in children (Mei 2011; Weikert 2005).
However, unilateral UPJO may improve or even resolve spontaneously without surgical intervention, and can persist without significant impairment of split kidney function (Dhillon 1998; Palmer 1998). Only around 25% of children with UPJO develop clinical problems or evidence of deteriorating kidney function that requires surgical intervention following conservative management (Malki 2012; Ransley 1990). Full recovery of impaired split kidney function after surgical procedure was reported for most of these children (Dhillon 1998).
Why it is important to do this review
Despite the epidemiological relevance of UPJO, optimal management remains controversial and practice varies widely (Csaicsich 2004; Ingraham 2011; NAPRTC 2008). Although early surgical intervention aims to prevent kidney function impairment (King 1984; Perez 1991), several studies have challenged this therapeutic approach, and recommend conservative management with close monitoring and serial kidney imaging (Dhillon 1998; Malki 2012; Palmer 1998). It is therefore essential to establish a common therapeutic approach in children with unilateral UPJO that balances the risks and costs of surgery with harms associated with excessive imaging and risk of kidney deterioration (Csaicsich 2004). The purpose of this review is to inform practice through the examination of evidence from randomised controlled trials (RCTs) comparing surgical and conservative management for children with UPJO.