Oliguria is the medical term for low urine output. The book Common Surgical Diseases defines oliguria as a urine output of less than 13.5 fluid ounces (400 ml) of urine each day. Low urine output may be a sign of an underlying health issue in the body.
Although low urine output sometimes has a simple explanation, anyone experiencing consistent low urine output should see a doctor for diagnosis and treatment.
One of the more common causes of low urine output is dehydration.
Dehydration occurs when the body does not get enough liquid from the diet or is releasing liquid too fast for a person to replenish it.
As a 2018 study paper notes, water represents approximately 60% of the body weight of those with a healthy body mass index (BMI). It only takes a loss of about 3% of body weight in water for a person to begin experiencing dehydration.
Dehydration may be more common when a person is dealing with an illness that causes symptoms such as fever, diarrhea, or vomiting. These symptoms use a lot of the body’s water and may make it more difficult for a person to keep liquids in their body.
In these cases, the kidneys may try to preserve the body’s liquid stores by not releasing urine.
Dehydration from sickness is especially dangerous in young children, as they may be unable to communicate their needs or symptoms.
Slowly drinking more water can help combat mild dehydration. Liquid-rich foods, such as fruits and soups, may also help if the person is well enough to eat them.
Doctors may also provide special electrolyte drinks to help replenish the body’s salts and liquids. In severe cases, doctors may give the person intravenous electrolytes and liquids.
Blockages in the urinary tract
Physical and functional blockages in the urinary tract are another possible cause of low urine output. Several issues may cause a blockage and prevent urine from leaving the body.
Conditions that may block the urinary tract include:
Blockages in the urinary tract may be easy to confuse with other issues. For instance, a blockage in some areas of the urinary tract may cause symptoms that include vomiting and fever. Someone with these symptoms may mistake them for a different illness that also causes dehydration.
However, blockages may cause additional symptoms, such as abdominal swelling and unexplained pains.
Treating blockages in the urinary tract involves first discovering what the blockage is and where it occurs. Doctors may order blood tests to check for abnormal proteins or signs of cancer. They are likely to order ultrasound, plain film X-ray, or CT scan imaging studies to check for blockages or examine underlying structures, such as the prostate.
The treatment options will depend on the underlying cause of the blockage.
Severe infections or trauma
Severe infections, such as sepsis, blood loss, or other trauma, may also lead to a loss of urine output by causing the body to go into shock. This state of shock reduces blood flow to organs such as the kidneys. The kidneys cannot make urine without this blood flow.
Shock is a medical emergency that requires immediate attention. Doctors will aim to stabilize the person first before performing tests to determine the underlying cause and start the appropriate treatment.
Taking certain medications may cause a loss of urine output.
Some medications may also cause a loss of urine output, and low urine output is one of the most common symptoms of acute kidney injury.
As a 2015 study notes, a few different medications may cause acute kidney injury. These medications include:
- nonsteroidal anti-inflammatory drugs (NSAIDs)
- aminoglycoside antibiotics
- angiotensin-converting enzyme (ACE) inhibitors
- contrast agents
Other drugs, such as chemotherapy drugs and immunosuppressants, may be harmful to the kidneys in general.
A person taking these medications regularly should ensure that they drink enough to hydrate their body before taking the drugs. People with a higher risk of kidney injury, including those with diabetes mellitus, may also wish to check in regularly with a doctor for tests to monitor their kidney function.
Kidney failure is a less common cause of low urine output. People who have an increased risk of kidney failure, a history of chronic kidney damage, or repeated acute kidney injury leading to chronic kidney damage may be more likely to experience significant kidney failure as time progresses.
Doctors will regularly test people who are either at risk of or have experienced a loss of kidney function. With early detection, there may be ways to halt or at least slow the loss of kidney function. If it progresses to total kidney failure, the person will need advanced treatments, such as dialysis or a kidney transplant.
When to see a doctor
A person who regularly has low urine output should see a doctor.
Sometimes, the underlying cause of low urine output is obvious, for example, a transient sickness. In these cases, this symptom should resolve once a person takes on more fluid. However, anyone who regularly has low urine output should see a doctor.
Anyone who is experiencing symptoms of shock should seek emergency care. Likewise, anyone with anuria — a nearly complete to complete loss of urine output — should seek immediate medical help. A total loss of urine may result in permanent damage to the kidneys.
Doctors will first want to rule out simple causes of this issue, such as more common illnesses. They will ask about any medications that a person uses and may order other tests, such as an ultrasound or CT scan, to detect any physical blockages.
Doctors will also order blood tests to help identify markers of any underlying conditions.
Seeing a doctor as quickly as possible is important to diagnose and treat an underlying disorder. Prompt treatment may help minimize or prevent long-term damage to the cells of the kidney.
The cause of low urine output can often be as simple as not getting enough liquid into the body. Ensuring that a person who is sick or physically stressed gets enough liquid may help combat low urine output that is due to dehydration.
In other cases, low urine output may be a sign of a more serious underlying condition, such as cancer or significant kidney failure.
In any case, it is best to see a doctor to diagnose the underlying cause of low urine output. Adequate treatment is important in each case to avoid potentially serious complications, which may include long-term damage to the kidneys.