Oliguria

Oliguria is a medical term used when referring to a decreased urine output. Oliguria is considered when a person’s urine output is less than 400 mL in a 24-hour period. When it comes to infants, oliguria occurs when the urine output is less than 0.5 mL/kg/hr for 24 hours. 

Anuria is the absence of urine and is characterized by less than 50 mL of urine output over a period of 24 hours. Oliguria is more common than anuria. However, if it is not properly treated, patients could develop anuria, which may result in serious kidney damage that will require specialized care.

Oliguria often has an acute onset, and one of the earliest signs of impaired renal function. It is also used as a criterion when diagnosing acute renal failure or acute kidney injury.

Causes of Oliguria

Oliguria has many potential causes. These causes are classified based on the following categories:

1. Prerenal (related to blood flow)

• Low cardiac output (e.g., pulmonary embolism, heart failure, and myocardial infarction)
• Hypovolemia (e.g., loss of fluid, inadequate fluid resuscitation or replacement, and bleeding)
• Low systemic vascular resistance (e.g., sepsis)

2. Renal (intrinsic or intrarenal acute kidney injury)

• Acute Tubular Necrosis (ATN): Rhabdomyolysis, renal hypoperfusion, X-ray contrast dye, and nephrotoxic medications, such as NSAIDs, certain antibiotics, and aminoglycosides

3. Postrenal (urinary outflow obstruction)

• Bladder and sphincter dysfunction (e.g., postoperative urinary retention, anticholinergic drug use, and fecal impaction)
• Mechanical obstruction (e.g., blocked urinary catheter, urinary calculi, or prostatic hypertrophy)

Other Causes

Mild to severe medical conditions can also cause oliguria. These conditions include:

Trauma or Infections

Trauma or infections can decrease the flow of blood to the body’s organs. These conditions can also lead the body to go into shock, which requires emergency medical attention. 

Urinary Tract Obstruction

Urine cannot leave the kidneys when there is blockage or obstruction in the urinary tract. When this happens, it will affect one or both of your kidneys and can cause a low urine output.

The symptoms of a urinary tract obstruction usually depend on how fast the obstruction forms or develops. However, its most common symptoms are:

• Fever
• Swelling
• Body aches
• Nausea
• Vomiting

Dehydration

The most common cause of oliguria is dehydration. In most cases, dehydration happens when sickness is accompanied by vomiting and diarrhea or other illnesses, and people are not able to replenish lost fluid in the body. 

Medications

There are certain medications that can cause a decreased urine output. They include:

• Medications for hypertension or high blood pressure (e.g., angiotensin-converting enzyme (ACE) inhibitors)
• Antibiotics (e.g., gentamicin)
• Nonsteroidal anti-inflammatory drugs (NSAIDs)

It is important to inform your doctor if your medication causes you to urinate less. Your doctor may adjust your dosage or change your medication. Do not stop taking your medication or change its dosage without your doctor’s advice. 

Diagnosis

During your doctor’s appointment, you will be asked some questions regarding your symptoms, personal medical history, including your family’s medical history. Knowing how much liquid you consume every day may also help your doctor assess your condition.

A urinalysis may also be ordered by your doctor to check your urine for any infection, protein, and uric acid level. Other required tests may include:

• Blood Tests: These tests can check signs of any infection, anemia (a symptom often accompanied by kidney problems), kidney failure, bleeding disorders, and other chemicals in the blood that promote kidney stone formation. Depending on the results of urine and routine blood tests, additional testing may be required for certain medical conditions that can cause kidney damage and inflammation, such as autoimmune disorders. 

• Urine Culture: Aside from a urinalysis, your doctor may also order a urine culture to find the germs that cause urinary tract infection. 

• Cystoscopy: Also called a cystourethroscopy, is a procedure that involves the use of a flexible telescope into the urethra and bladder to look for tumors and check the overall health of the urethra and bladder. This procedure is usually performed with local anesthesia and sedation. 

• Intravenous Pyelogram (IVP): An IVP is an X-ray examination, which involves the injection of a contrast medium or dye into a vein. This dye provides a guide or outline of the urinary tract system and helps identify tumors and kidney stones. 

• Ultrasound: This imaging test utilizes sound waves to help identify if renal masses are solid (malignant tumor) or fluid-filled (benign cyst). Renal stones can also be identified through ultrasound imaging. 

• Abdominal and Pelvic Computed Tomography (CT) Scan: This imaging scan uses modified X-ray beams at multiple angles to provide a 3D-look inside the body’s organs, such as the kidneys and organs in the abdominal and pelvic regions. This test usually combines the features of a CT scan and an IVP by also using a contrast dye injection. When it uses such combination, the scan is called a CT urogram. 

Also, make sure that you inform your doctor if you experience other symptoms or if you are currently taking medications and supplements.

Treatment

Treatment for oliguria usually depends on its main cause. An IV drip may be prescribed by your doctor for quick rehydration or recommend a dialysis to help remove toxins in your blood. Medications that may be toxic to the kidneys may also be changed or stopped. 

For illnesses with fever, vomiting, or diarrhea, consuming special electrolyte drinks may help replace lost electrolytes and prevent oliguria from happening.

Prevention

Generally, oliguria cannot be prevented when it is caused by a medical condition. When a low urine output is due to dehydration, which is the most common cause of oliguria, preventive measures can be done by making sure that you are well hydrated all the time. 

When to See a Doctor

You should call your doctor if you experience oliguria since this symptom could be due to trauma or a serious infection that requires emergency medical treatment.

You should also seek immediate medical attention if you experience oliguria along with other symptoms, such as a fast heart rate, dizziness, or lightheadedness. It is very important to speak with your healthcare provider right away to develop a suitable treatment plan for your condition. 

References

Oliguria - Critical Care Medicine - MSD Manual Professional Edition. (January 2017). https://www.msdmanuals.com/professional/critical-care-medicine/approach-to-the-critically-ill-patient/oliguria

Oliguria (decreased urine production) information. myVMC. (2017) https://www.myvmc.com/symptoms/oliguria-decreased-urine-production/

Prowle, J., Liu, Y., Licari, E., Bagshaw, S., Egi, M., & Haase, M. et al. (2011). Oliguria as predictive biomarker of acute kidney injury in critically ill patients. Critical Care, 15(4), R172. doi:10.1186/cc10318