A decrease in urine volume (oliguria) can be correlated with different possible causes. Which are the most common? Who to consult? Explanations from Dr Ugo Pinar, Head of Clinic in the urology department at the Pitié-Salpêtrière hospital in Paris.
The decrease in the volume of urine (oliguria or oligoanuria) is part of urination disorders and can have several possible causes, more or less serious (heart failure, kidney failure, obstruction of the urinary tract, medications, etc.). The search for the cause of oliguria and an accurate diagnosis is essential in order to seek the appropriate treatment.
Oliguria: a symptom (insufficiency of urination) and not a disease
From a health point of view, a decrease in urine volume (oliguria or oligoanuria) does not constitute a pathology but a symptom which, as such, must be taken into consideration. “Unlike anuria, characterized by the absence of urine output over 24 hours, oliguria meets precise standards, namely a urinary flow rate of less than 500 ml per 24 hours in an adult. underlines Dr Ugo Pinar, Head of Clinic at the urology department at the Pitié Salpêtrière hospital in Paris.
As a reminder :
- In adults, normal urine output should be between 800 and 1,500 ml per 24 hours.
- In children, oliguria is diagnosed when the urine volume is less than 0.5 ml per kg per hour.
Oliguria can be correlated with four main possible causes, detailed below.
Problematic urination volume
Urologists and nephrologists distinguish between different diuresis disorders:
- Polyuria, when the volume of urine over 24 hours exceeds 3 liters;
- Oliguria, when urine output is less than 500 ml over 24 hours;
- Anuria, when the volume of urine falls below 100 ml over 24 hours.
A drop in blood volume (hypovolemia)
First of all, the volume of body fluids plays a tangible role. “Logically, if the volume of fluids decreases, you will urinate less. specifies the specialist. Several reasons can explain a drop in blood volume, namely the total blood volume in the body. Heart failure, hemorrhage, dehydration, high fever causing heavy sweating… all these causes can be the cause of oliguria, reduction of urine emitted.
Different possible renal causes
One of the functions of the kidneys is to produce urine. If they work less well, the kidneys will produce less urine (diuresis). Several pathologies can be the cause of these urinary disorders: acute or chronic kidney failure, or even a kidney infection (polynephritis), for example.
An obstructive cause in the urinary tract
Urine passes from the kidney to the bladder via the ureter. All causes of obstruction in the urinary tract can thus cause oliguria. “Kidney stones located in the ureter, benign prostatic hypertrophy, etc. are among the most common causes of oliguria.”adds Dr Ugo Pinar.
Iatrogenic causes of oliguria
Finally, certain classes of drugs are nephrotoxic (toxic to kidney function) and can induce oliguria. This is the case for anti-inflammatories, certain diuretics as well as certain classes of antibiotic medications.
Find the cause of oliguria to consider the right treatment
As such, oliguria remains an isolated symptom that does not represent a life-threatening issue. “However, it must be the subject of rapid treatment in order to be able to establish a precise diagnosis and to consider the appropriate treatment of the pathology causing the symptom. continues Dr. Ugo Pinar. On the other hand, anuria (total absence of urine over 24 hours) represents a medical emergency.
Certain clinical signs can guide the diagnosis. “A person who has a hypovolemia problem is thirsty and has low blood pressure. explains the Head of Clinic.
In addition, a person suffering from urinary retention (as is the case with an enlarged prostate, for example), may want to urinate, but will not be able to do so.
Sedema in the legs is another symptom associated with oliguria which may raise suspicion of severe kidney failure or heart failure.
Medical assessment to clarify the diagnosis in case of oliguria
A medical assessment must therefore be considered depending on the diagnostic orientation.
If hypovolemia is suspected, blood pressure measurement will be essential. If the doctor suspects heart failure, various tests such as an electrocardiogram and a cardiac ultrasound will be carried out.
The presence of pain or fever may raise suspicion of a kidney infection. A urine test and a blood test will therefore be prescribed to establish the diagnosis. “Finally, a renovation ultrasound will eliminate obstructive causes and check the proper functioning of the bladder. enlightens Dr. Ugo Pinar.
Finally, a blood test including an ionogram (composition of ions, potassium, sodium, chlorine, etc.), the creatinine dosage as well as a blood count (blood count) must also be considered.