Page 121 - Urological Health

How do the kidneys work?

To understand hydronephrosis, it is helpful to know about the urinary tract system. This is a group of
body parts that work together to make, collect and pass urine. The urinary tract system includes the
kidneys, ureters, bladder and urethra.

Here’s how the system works:
• The tissue of the kidney (called the renal parenchyma) filters and removes waste from the
blood, which makes urine.
• Urine moves into the collecting system. First into the calyces and then into the renal pelvis.
• Urine leaves the collecting system of the kidney and flows down to the bladder through
a tube called the ureter.

• Urine is stored in the bladder.
• When the bladder empties, urine flows out through a tube called the urethra.
• The opening of the urethra is at the end the penis in boys and in front of the vagina in girls.
The urinary system The parts of the kidney

Capsule
Renal parenchyma

Minor calyces

Kidney Major calyces
Ureter Renal pelvis

Bladder
Urethra Ureter

What causes hydronephrosis?

The three most common known causes are:

Ureteropelvic Junction (UPJ) Obstruction • Ureterovesical Junction (UVJ) Obstruction
• Part of the urinary tract is narrowed or kinked.This can occur at the point where the ureter connects
to the kidney, called the ‘ureteropelvic junction’.
• Urine builds up in the collecting system and dilates the renal pelvis.
• Part of the urinary tract is narrowed or kinked.This can occur at the point where the ureter connects
to the bladder, called the ‘ureterovesical junction’.
• Urine builds up in the ureter and collecting system.The ureter becomes dilated, this type of ureter
dilatation is called a megaureter.
Vesicoureteral Reflux (VUR)
•Urine flows backward, from the bladder back up into the ureters and sometimes all the way to the kidneys.
• The ureters may become dilated.

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