A urinary obstruction refers to anything that blocks, slows, or disrupts the normal flow of urine through the urinary tract. Obstructions can occur at any point in the urinary tract. They can be present at birth (congenital) or develop later.

Causes of urinary obstructions in children include:

• Kidney stones. Kidney stones are caused by the buildup of minerals in the kidneys.
• An abnormality of the point where the ureter joins the kidney.
• A sagging or bulging of the ureter into the bladder, called a ureterocele.
• An abnormality in which the ureter opens into an area other than the bladder. The ureter may open into the urethra or the vagina in girls or the vas deferens in boys.
• Misplaced, narrowed, or widened ureters or urethra.
• Posterior urethral valves in boys (congenital blockage of urethra).

Urinary obstructions disrupt normal urine flow and allow bacteria to grow in the urinary tract. This increases the risk of bladder and kidney infections.