Understanding ureteropelvic junction obstruction: how far have we come?

Abstract

Congenital anomalies of the urinary tract are a major cause of chronic kidney disease in both adults and children. Ureteropelvic junction obstruction, usually detected as urinary tract dilatation in utero, is one of the most common forms of CAKUT. As antenatal ultrasound technology advances and screening becomes more widespread, increasing numbers of infants with this UPJO will be detected. Management of these infants presents a clinical conundrum, as distinguishing mild benign cases from those who may develop severe renal impairment is challenging. Herein we propose that an understanding of normal developmental and pathological mechanisms involved in UPJO is important in the armamentarium for tackling this challenging condition.

Keywords: CAKUT (congenital anomalies of the kidney and urinary tract); UPJO; development; kidney malformation; pediatric nephrology; ureteropelvic junction obstruction.

Figure 1

Schematic Overview of Collecting System Development. The ureteric bud invades the metanephric mesenchyme, cap mesenchyme is induced via a number of reciprocal interactions and will ultimately form the nephron. Dichotomous branching of the UB contributes to the development of the collecting system from which the developing ureter elongates towards the cloaca. Development of the ureter – smooth muscle and epithelial layers- is controlled by reciprocal interactions involving a number of molecular drivers; SHH, sonic hedgehog; TBX18, t-box transcription factor 18; BMP4, bone morphogenic protein 4; TSHZ3, teashirt zinc finger homeobox 3, MYOCD, myocardin. Created with BioRender.com.

Figure 2

Overview of Pathological Changes in UPJO. Proposed mechanisms involved in UPJO pathogenesis include increased extracellular matrix, smooth muscle changes, inflammatory cell infiltrates, and reduced nerve fibers. UPJ, ureteropelvic junction obstruction. Created with BioRender.com.