Hydronephrosis describes the situation where the urine collecting system of the kidney is dilated. This may be a normal variant or it may be due to an underlying illness or medical condition.
Normally, the kidney filters waste products from blood and disposes of it in the urine. The urine drains into individual calyces (single=calyx) that form the renal pelvis.
This empties into the ureter, a tube that connects the kidney to the bladder. The urethra is the tube that empties the bladder.
While obstruction or blockage is the most frequent cause of hydronephrosis, it may be due to problems that occur congenitally in a fetus (prenatal) or may be a physiologic response to pregnancy.
A large percentage of pregnant women develop hydronephrosis or hydroureter. Experts think this is, in part, because of the effects of progesterone on the ureters, which decreases their tone.
Technically, hydronephrosis specifically describes dilation and swelling of the kidney, while the term hydroureter is used to describe swelling of the ureter. Hydronephrosis may be unilateral involving just one kidney or bilateral involving both.
A complication of hydronephrosis that is not physiologic is decreased kidney function. The increased pressure of extra fluid within the kidney decreases the blood filtration rate and may cause structural damage to kidney cells.
This decrease in function is often reversible if the underlying condition is corrected but if the duration is prolonged, the damage is often permanent.
How is Hydronephrosis Caused?
Hydronephrosis is usually caused by another underlying illness or risk factor. Causes of hydronephrosis include, but are not limited to, the following illnesses or risk factors:
- Kidney stone
- Congenital blockage (a defect that is present at birth)
- Blood clot
- Scarring of tissue (from injury or previous surgery)
- Tumor or cancer (examples include bladder, cervical, colon, or prostate)
- Enlarged prostate (noncancerous)
- Urinary tract infection (or other diseases that cause inflammation of the urinary tract)
How is Hydronephrosis Diagnosed?
An ultrasound is typically used to confirm a diagnosis. This procedure uses sound waves to create an image of your kidneys. A doctor can also confirm a diagnosis with x-rays, computerized tomography (CT) and magnetic resonance imaging (MRI).
Diagnosis could also involve a cystoscopy, which uses a long tube with a light and camera at the end (cytoscope) that allows the doctor to look inside the bladder and urethra.
Blood and urine tests can also check kidney function. The doctor can also check for blood in the urine, which can be caused by a kidney stone, infection or other factor.
What are the symptoms of hydronephrosis?
There may or may not be direct symptoms of hydronephrosis depending upon the underlying cause.
Individuals with acute hydronephrosis, for example symptoms from renal colic due to a kidney stone begin with an acute onset of intense flank or back pain radiating to the groin, associated with nausea, vomiting, and sweating.
Colicky pain comes and goes and its intensity may cause the person to writhe or roll around or pace in pain. There may be blood seen in the urine.
Chronic hydronephrosis develops over time and there may be no specific symptoms. Tumors in the pelvis or bladder obstruction may develop silently and the person may have symptoms of kidney failure.
These are often nonspecific and may include weakness, malaise, chest pain, shortness of breath, leg swelling, nausea and vomiting.
If electrolyte abnormalities occur because the kidneys are unable to regulate sodium, potassium, and calcium, there may be heart rhythm disturbances and muscle spasms.
When should I seek medical care for hydronephrosis?
A person with acute hydronephrosis usually develops significant pain and needs emergent help with pain control.
Blood in the urine is never normal and should not be ignored. Most often in women, it is due to a bladder infection, but other causes include kidney stones, tumors, and occasionally is associated with appendicitis.
Individuals who have the diagnosis of hydronephrosis who develop a fever need to be seen immediately.
If a urinary tract infection occurs and there is decreased urine flow, there is the risk of becoming very ill by developing bacteremia (blood stream bacterial infection).
Hydronephrosis is a true emergency in patients with only one kidney and should the person believe that the lone kidney is at risk, urgent medical care should be accessed.
How is Hydronephrosis Treated?
Hydronephrosis is usually treated by addressing the underlying disease or cause, such as a kidney stone or infection. Some cases can be resolved without surgery.
Infections can be treated with antibiotics. A kidney stone can pass through by itself or might be severe enough to require removal with surgery.
In cases of severe blockage and hydronephrosis, excess urine may need to be removed using either a catheter to drain urine from the bladder or a special tube called a nephrostomy that drains urine from the kidney.
The key to treatment is to get it addressed as soon as possible in order to avoid any permanent damage to the kidneys.
Severe cases of urinary blockage and hydronephrosis can damage the kidneys and lead to kidney failure. If kidney failure occurs, treatment will be needed with either dialysis or a kidney transplant.
However, most people can recover from hydronephrosis if treated promptly.