[Effect of urethral stenoses on the urinary tract]

Area of Science:

• Developmental biology
• Urology
• Experimental medicine

Background:

• Congenital urinary tract anomalies are a significant cause of pediatric morbidity.
• Understanding the developmental pathogenesis of conditions like megaureter syndrome is crucial for effective intervention.

Purpose of the Study:

• To investigate the effects of induced intrauterine urethral stenosis on the developing fetal urinary tract in sheep.
• To elucidate the pathogenesis of upper urinary tract dilatation and its correlation with the degree of infravesical obstruction.

Main Methods:

• Intrauterine surgical procedures were performed on fetal sheep (50-122 days gestation).
• Varying degrees of urethral stenosis were created using silk, catgut, and polyglycolic acid sutures.
• Urachal ligation was performed in all cases; urethral stenosis was added to experimental groups.

Main Results:

• Urachal ligation alone had no adverse effects on the upper urinary tract.
• Urethral stenosis led to upper tract dilatation, proportional to the degree of obstruction.
• Progressive changes included pyelocalyectasis, hydronephrosis, hydroureter, and megacystis, with dilatation progressing antegrade from the renal pelvis.
• Histological findings revealed reduced parenchymal thickness, dilated tubules, and muscular hypertrophy in the ureter and bladder; extreme obstruction caused ureteral muscular atrophy.

Conclusions:

• Induced urethral obstruction in fetal sheep mimics key pathological features of congenital urinary tract anomalies.
• The study provides insights into the pathogenesis of megaureter syndrome, highlighting the role of infravesical obstruction in driving upper tract dilatation.
• The experimental model demonstrates that dilatation begins in the renal pelvis and progresses towards the bladder, with specific histological changes observed in the parenchyma, ureter, and bladder.