An Overview of Oliguria

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Oliguria is when urine output is lower than expected. It is typically a result of dehydration, a blockage, or medications. Most of the time, oliguria can be treated at home, but in some cases, it can be a symptom of a serious medical condition that requires further testing and treatment. Oliguria is different from anuria, which is when urine output stops completely. 

Symptoms

The primary symptom of oliguria is producing less urine than normal. Individuals might experience other symptoms as well, depending on the cause of the decrease. The primary signs and symptoms of oliguria are: 

  • Urinating less frequently and/or producing a smaller amount than usual. 
  • Urine is a darker color than normal (generally a deeper yellow color such as amber). If there is red or dark red blood in urine, this is a different type of issue called hematuria.

When to Call Your Doctor

Because a sudden decrease in urine output could be a sign of a serious medical issue, you should talk to your doctor right away if you also have any of the following symptoms:

  • Vomiting, diarrhea, or otherwise can’t seem to hold fluids
  • Racing heart
  • Dizziness
  • Feeling lightheaded

If left untreated, oliguria can also lead to kidney injury. 

Causes

A number of things can cause oliguria, including dehydration, blockages, and medications.

Dehydration

The most common cause of oliguria is dehydration. Dehydration is when your body doesn’t have enough water or fluids—generally because it’s losing more than it’s taking in. This can happen when you sweat a lot on a hot day or have a stomach bug that causes diarrhea or vomiting.

Blockage 

Decreased urine output can also happen when something is physically blocking the urinary tract (such as an enlarged prostate or kidney stones), limiting the flow of urine. These blockages can occur anywhere along the urinary tract, including the kidneys, ureters (tubes draining the kidney, bladder, and the urethra, which drains the bladder), and are more common in adults than children.

Medications 

Some medications can affect the body’s ability to produce or release urine. Drugs that can affect urine output include:

  • Anticholinergics: Used to block involuntary muscle movements and other bodily functions. Anticholinergics are used to treat a variety of diseases, such as Parkinson’s disease and gastrointestinal disorders, and overactive bladder. 
  • Non-steroidal Anti-inflammatory Drugs (NSAIDs): Medications used to reduce swelling or relieve pain. Examples include ibuprofen and aspirin. 
  • Diuretics: Substances that prompt the body to produce and release more urine. When used in excess or for too long, diuretics can lead to dehydration or kidney injury (or other health issues)—ultimately resulting in a decrease in urine production.
  • Antibiotics: Use of some antibiotics (like ciprofloxacin and penicillin) can harm the kidneys, and that can affect urine output. This is more common in young children or those with chronic health issues.

Other Causes 

While less common, other things can also cause a decrease in urine output. These include: 

  • Substantial blood loss
  • Serious infections
  • Physical trauma
  • Shock

Diagnosis

Oliguria is typically diagnosed during a physical exam. Doctors also might want to run further tests to investigate potential causes or check for related health issues.  

Physical Exam 

At the doctor’s visit, they will likely ask you a series of questions about your health to get a better idea of what might be causing the decrease in urine output. For example, your doctor will examine you for signs of dehydration or urinary tract blockage (such as pain in the low abdomen [bladder] or flank [kidneys]).

Doctors diagnose oliguria based on the amount of urine you produce in a day, though the criteria used are different for adults and kids:

  • Adults: less than 500 milliliters (mL) of urine in a 24-hour period.
  • Children: less than 500 mL/1.73 square meter (m2) in a 24-hour period.
  • Infants: less than 0.5 mL/kilogram (kg) per hour in a 24-hour period for infants.

Other Tests 

Doctors might also want to run more tests to determine what caused the drop in urine output and whether the decrease has caused harm to the kidneys. Some tests they might want to run include: 

  • Urine tests: To check for an infection, including urinalysis and urine culture. Additional tests of kidney function include 24-hour urine testing where urine is collected and analyzed over a one-day period at home.
  • Ultrasound or CT scan of the abdomen: To check for an obstruction, such as dilation of kidney (hydronephrosis).
  • Blood tests: To check your electrolytes, blood count, or kidney function.
  • Cystoscopy: A procedure by a urologist that involves using a small camera scope to see inside the bladder.

Treatment

How oliguria is treated depends on several different factors, including the overall health of the individual, the likely cause of the decrease in urine, and whether there’s been any injury to the kidney. Generally speaking, doctors typically recommend increasing your fluid intake, stopping medications that may be the cause of the problem, and/or using medications to treat the problem.

Increasing Fluid Intake 

A simple way to treat oliguria is by increasing the amount of fluids you take in. This can often be done at home by drinking more water or rehydration solutions that include electrolytes. In cases of severe dehydration or where another health issue is at play, your doctor might recommend intravenous (IV) fluids and possible hospitalization.

Medications 

If rehydration isn’t enough—or if there are other health issues affecting your urine output or hydration levels—your doctor might recommend using medications to treat oliguria or its underlying cause. 

Medications used to treat oliguria include: 

  • Antimicrobials: To treat infections, such as those that cause serious diarrhea or vomiting.
  • Diuretics: Which force the body to produce more urine. In small amounts, diuretics can help increase urine output, but as noted above, too much can backfire and make oliguria worse.
  • Renal-dose dopamine: A somewhat debated treatment used to prevent kidney injury by expanding arteries in the kidney and increasing urine output.

Prevention 

Because many cases of oliguria are caused by dehydration, one of the best ways to prevent it is by taking in enough fluids. The amount of fluids you need to drink will depend on how much you’re losing through sweat or sickness, as well as your overall diet. 

Contrary to health food blogs or conventional wisdom, there is no one-size-fits-all set of guidelines for how much water a person should drink every day. But the Institute of Medicine does have recommendations for how much fluid you should take in overall—including fluids from food and non-water beverages. According to the Institute of Medicine:

  • Women should get 2.7 liters of fluids (or roughly 11.4 cups) per day.
  • Men should get 3.7 liters (or roughly 15.6 cups) of fluids per day.
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