Hydronephrosis can occur in people of all ages. If the condition occurs before birth, it is called fetal or antenatal hydronephrosis.

There are many causes of hydronephrosis. In adults, the conditions that most often cause hydronephrosis include:

• Kidney stones: Salts and minerals that are present in urine can form small hard stones that may become lodged in the kidneys or urinary tract.
  
• Cancer: Tumors in the bladder, prostate gland, uterus or other organs that are part of or near the urinary tract may cause blockages that disrupt the flow of urine.
• Benign prostatic hyperplasia (BPH): Enlargement of the prostate gland in men can cause pressure on the urethra, the tube that urine passes through before it leaves the body.
  

Other possible causes of hydronephrosis include:

• Blood clots in the kidney or ureter
• Narrowing or stricture of the urinary tract due to injury, infection, birth defects or surgery
• Nerve or muscle problems that affect the kidneys or ureters
• Urinary retention due to an inability to empty the bladder
  
• Vesicoureteral reflux, when urine flows backwards from the bladder to the kidneys
  
• Uterocele, when the lower part of the ureter may protrude into the bladder
  

In women, hydronephrosis may occur as a result of:

• Pregnancy: As the uterus expands, it can press on the ureters and block the flow of urine.
• Uterine prolapse: A condition in which a woman’s uterus (womb) sags or slips out of its normal position.
• Cystocele (fallen bladder): A condition that occurs when the wall between a woman’s bladder and her vagina weakens and allows the bladder to droop into the vagina.

• Sudden or intense pain in the back or side
  
• Nausea
• Vomiting
• Frequent or painful urination
  
• Blood in the urine
  
• Weakness or malaise
  
• Fever due to a urinary tract infection
  

• Physical examination: Your doctor will ask you about any symptoms you are having and will examine the area near the kidneys and bladder for tenderness or swelling. The doctor may ask about your medical history and your family’s medical history. Men may need to undergo a rectal exam to determine whether the prostate is enlarged. Women might require a pelvic exam to evaluate whether there are any problems with the uterus or ovaries.
• Urine tests: A urine sample will be collected and analyzed to find out if any blood cells, bacteria or abnormal cells are present.
  
• Blood tests: A complete blood count may be performed to determine whether an infection is present. Other tests such as a blood urea nitrogen (BUN) test or glomerular filtration rate may be done to evaluate kidney function.
• Imaging procedures: These tests may include X-rays, computed tomography (CT scan) or ultrasound.
  

If hydronephrosis is caused by stones in the kidneys or ureters, these options are available:

• Shock wave lithotripsy: This is the most common method for treating kidney stones. High-energy shock waves are emitted by a machine outside to break up the stones into dust or smaller fragments so they can pass out of the body.
• Ureteroscopy: A thin tube with special instruments may be placed in the urethra to allow a doctor to break up and remove the stones. This method is used most often for stones in the bladder or lower half of the ureters. Ureteroscopy may be used in combination with other techniques, such as a pulsed dye laser or electrohydraulic lithotripsy, to break up stones. This is the method of choice for pregnant women, patients with blood clotting disorders, and those who are morbidly obese.
• Surgery: When kidney stones are very large or difficult to remove, they may have to be removed surgically. Also, you might need surgery in the case of tumors or other types of blockage.