Idiopathic Hydronephrosis: Types, Causes, Symptoms, Diagnosis, Treatment and Complications

The term “idiopathic” indicates that inflammation does not respond to any apparent reason and that, on the contrary, it is not known what the causes of the condition are.

Idiopathic hydronephrosis is only a condition in which the collecting system of urine of the kidney is dilated.

Technically, idiopathic hydronephrosis specifically describes the dilation and swelling of the kidney, which can cause a decrease in kidney function.

The increased pressure of fluid retained within the kidney decreases the rate of blood leakage and can cause structural damage to the kidney cells.

This decline in kidney function is often reversible if diagnosed early and the underlying condition corrected, but if the duration is prolonged, the damage is usually permanent.


  • Unilateral: Involves a single kidney.
  • Bilateral: Involves both kidneys.

Causes of idiopathic hydronephrosis

The causes of hydronephrosis are multiple and are classified according to the place where the swelling is located, that is, if the motivation is intrinsic (within the urinary collector system), extrinsic (outside the collector system) or if, on the contrary, it is due to an alteration in renal function.

In the case of idiopathic hydronephrosis, in which the exact cause is unknown, experts can not rule out any of these as the origin of the condition.


Intrinsic Causes of Hydronephrosis

In the ureter:

  • Kidney stones are probably the most common reason for unilateral hydronephrosis because the kidney stone obstructs the urethra.
  • Blood clot.
  • Stenosis or scars.

In the bladder:

  • Bladder cancer.
  • Stones in the bladder.
  • Cleanliness.
  • Contracture of the neck of the bladder.

In the urethra:

  • Urethral stricture
  • Urethral valves
  • Urethral cancer.

Extrinsic Causes of Hydronephrosis


  • Tumors or cancers compress the urethra and prevent the flow of urine.
  • Fibrosis retroperitoneal.
  • Ovarian vein syndrome.
  • Cancer of the cervix.
  • Prostate cancer.
  • The pregnancy.
  • Uterine Prolapse


  • Hypertrophy or swelling of the prostate is a frequent cause of urinary retention and hydronephrosis in men.
  • Prostate cancer

Functional causes of hydronephrosis


  • Neurogenic bladder: the inability of the bladder to function correctly. It originates due to nerve damage. This can occur in the case of multiple sclerosis, diabetes, brain tumors, injuries, or spinal cord tumors.
  • Vesicoureteral reflux: when the urine moves in the opposite direction from the bladder to the urethra.

Symptoms of idiopathic hydronephrosis

A person with acute hydronephrosis usually develops significant pain, blood in the urine, fever, and decreased urine flow.

Chronic hydronephrosis develops over time and may not have definite symptoms and may include weakness, malaise, chest pain, shortness of breath, swelling of the legs, nausea, and vomiting.

If electrolyte abnormalities occur because the kidneys cannot regulate sodium, potassium, and calcium, there may be changes in heart rhythm and muscle spasms.

In acute hydronephrosis, the symptoms of kidney colic due to a kidney stone begin with the appearance of intense back pain that radiates to the groin, associated with nausea, vomiting, and sweating, and there may be blood in the urine.


The diagnosis begins with a history of the symptoms that the patient develops.

The physical examination may reveal sensitivity where the kidneys are located; the bladder may be distended. In men, a rectal exam is performed to assess the size of the prostate; in women, a pelvic exam can be performed to evaluate the uterus and ovaries.

In addition, the following tests are carried out depending on the potential diagnosis:

Lab tests:

  • Urine analysis.
  • The complete blood count.
  • The electrolyte analysis.
  • NUS (blood urea nitrogen), creatinine, and glomerular filtration rate (GFR) are blood tests that help evaluate kidney function.

Image studies:

  • Tomography to evaluate the anatomy of the kidney, kidney stones, or structures that compress the urinary collecting system.
  • Ultrasound to assess structures in the abdomen and retroperitoneum. Ultrasound is also helpful in pregnant women where there are radiation problems.
  • Intravenous pyelography (IVP) has been replaced mainly through computed tomography, but its use is limited.
  • The X-Rays, an x-ray that shows the bladder, kidney, and urethra, are used to classify a kidney stone as radiodense or radiotransparent or determine if the stone can migrate down the urethra into the bladder.

Treatment of idiopathic hydronephrosis

The treatment for idiopathic hydronephrosis depends on the condition’s cause and the degree of severity.

The treatment aims to restart the free flow of urine, decreasing the swelling and, therefore, the pressure to minimize pain and prevent urinary tract infections and treat the underlying cause avoiding permanent kidney damage.

Among the treatments are:

  • Formal surgery or laparoscopy.
  • Antibiotics and steroid therapy.
  • The lithotripsy by shock waves. The shock waves from outside are directed to a kidney stone, causing the stone to fragment into small pieces that can pass from the urinary tract to the urine.
  • Placement of a “stent” in the urethra.
  • The insertion of a percutaneous nephrectomy tube through the side directly into the kidney to allow the urine to drain.

Complications of idiopathic hydronephrosis

If idiopathic hydronephrosis is not treated early, increased pressure from liquids retained in the kidney may decrease the ability of the kidney to filter blood.

In this way, it is possible to eliminate the waste products, allowing the passage of urine and regulating the level of electrolytes in the body.

It can also cause kidney infections and, in some instances, complete loss of kidney function or, in more chronic cases, death.