Oliguria: causes, symptoms and treatment

Chronic renal failure (CKD) is defined as the progressive, permanent and irreversible loss of the glomerular filtration rate of the kidneys over a variable period of time. Oliguria is one of the symptoms of CRF.

According to epidemiological data, 17.8% of the adult population could suffer from this condition. The value increases to 45% in the elderly. Basically oliguria it is defined as a decrease in urine output (diuresis).

In addition to chronic kidney failure, it can also be a sign of acute kidney disease, dehydration, acute tubular necrosis, and many other etiologic agents. If you want to find out everything about this clinical sign, keep reading.

What is oliguria?

A person who drinks 2 liters of water a day should go, on average, once to the bathroom every 4 hours to urinate. The kidneys are continually working to purify the blood, so we produce approximately 800 to 2,000 milliliters of urine per day.

As indicated by the Navarra University Clinic (CUN), oliguria is defined as the reduction of urinary volume below the necessary one. The standardized figure from which the event begins to be considered pathological is 0.3 milliliters / minute or, failing that, less than 400 milliliters of urine every 24 hours.

Of course, this cut-off point of 400-2000 milliliters of urine produced is set for a "normal" person; that is to say, of about 70 kilograms of weight, evolemic (balance in the blood pressure) and with an optimal renal function. According to the MSDmanuals portal, oliguria can be classified into 3 different types:

1. Prerenal: related to blood flow.
2. Renal: by intrinsic affections to the glomeruli and other structures of the kidneys.
3. Postrenal: obstruction in the passages of exit of the urine.

The stage after oliguria is anuria; that is, the total absence of urine production. The clinical sign is considered anuria when the patient produces less than 100 milliliters of urine in 24 hours. It is the most serious form.

General table

Based on the information collected so far and according to the parameters of the Electronic Journal of Medical Portals, these are the clinical stages that are conceived in terms of urination:

• Normal urine production: 1.5 to 2 liters per day.
• Oliguria: production of 100 to 400 milliliters per day.
• Anuria: production of less than 100 milliliters per day.
• Absolute anuria: no urine is produced. Unless proven otherwise, it is assumed to be due to a blockage in the urinary tract.

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What are the symptoms that accompany an oliguria?

As we have said previously, oliguria is not a disease in itself but it is one more clinical sign. Depending on the underlying disease, symptoms can be very different and oliguria may or may not be present. Next, we present the symptoms of acute kidney disease:

• Oliguria: decrease in the volume of urine excreted, although in some cases it can remain stable.
• Fluid retention derived from this lack of urination that results in swelling of the legs, ankles and feet.
• Shortness of breath, fatigue and disorientation.
• Nausea and weakness.
• Irregular heartbeat
• Pain or tightness in the chest
• Coma and unconsciousness in the most severe cases.

All of these clinical signs indicate that something is wrong with the kidneys. When these organs do not work well, toxic and harmful substances accumulate in the bloodstream, and the blood composition becomes unbalanced. In these cases, the patient's homeostatic balance is lost.

Possible complications

If the kidneys don't filter well, it can cause an accumulation of fluid in the pulmonary alveoli. This results in feeling overwhelmed, shortness of breath, and possible death of the patient if not acted on quickly.

Also, due to underlying processes, inflammation of the pericardium can occur, leading to chest pain and altered heart rate. All these events bring the patient closer to death, so it is vital to see a doctor before any indication of kidney failure.

Main causes

As we have said, oliguria can be prerenal, renal, and postrenal. Depending on the organs and structures affected, different causes can be identified, such as the following:

Dehydration

If there is no fluid in the body, the kidneys cannot make urine. A prolonged severe diarrhea or the presence of repeated vomiting due to an infectious disease can cause the loss of fluids and electrolytes in the patient's body. Thus, oliguria is a clear sign of dehydration.

Obstruction in the urinary tract

We would be, on this occasion, before a postrenal etiologic agent. As indicated by the MSDmanuals portal, the causes of obstruction in the urinary tract in adults are, generally, kidney stones, benign prostatic hyperplasia and, in the most severe cases, prostate cancer.

Kidney disease

If the kidneys do not filter the blood properly, oliguria may appear in the patient. Chronic kidney disease (CKD), acute kidney disease (ARD), glomerulonephritis or hemolytic uremic syndrome are clinical entities that can drastically reduce the rate of urination of the individual.

Low cardiac output

Cardiac output is the volume of blood expelled by a ventricle in one minute. If the heart doesn't pump enough blood, the kidneys can filter less and produce less urine. Anemias, hemorrhages, and hypertension can promote this type of prerenal oliguria.

How is oliguria diagnosed?

Oliguria is not a disease, so the diagnosis must be made at the level of the etiological agent that causes it. First of all is the anamnesis; that is, communicate with the patient. If the patient has an urgent need to urinate but cannot, the oliguria is probably the result of an obstruction in the urinary tract.

On the other hand, if the individual is very thirsty but does not want to urinate, a lack of fluid volume in your body is suspected. Also, a gradual decrease in the volume of urine produced over days (or months) may indicate acute tubular necrosis or a prerenal cause.

After these initial distinctions, the doctor will decide the types of tests to perform on the patient. It goes without saying that prostate cancer is not the same as reduced cardiac output due to hypertension. Each clinical entity requires a series of specific tests for diagnosis.

When to seek medical help

Sometimes it is normal to urinate less than normal, perhaps because the rate of hydration has been neglected in a busy workday. In any case, if this lack of urination is accompanied by any of these symptoms, it is essential to see a doctor. Among the symptoms that lead to medical consultation:

1. You don't urinate enough and your limbs are swollen.
2. You experience a feeling of tiredness, disorientation, and trouble catching your breath.
3. You feel nausea and chest pain / pressure.

Available treatments

According to medical portals already cited, the approach depends entirely on the cause of the oliguria. Before deciding on any medical treatment, the healthcare professional should ask the following questions:

1. Does the patient have a normal blood pressure?
2. Is there evidence of kidney disease?
3. Is there evidence of a urinary tract obstruction?

Based on these 3 questions and their answers, treatment is started in one way or another. Here are some of the most common approaches depending on the type of oliguria the patient presents.

1. If the cause is prerenal

If the oliguria is due to a dysfunction in blood pressure (and therefore in cardiac output), it is potentially reversible with proper treatment and early recognition of the condition. The initial approach is intravenous fluid therapy, followed by the pertinent drugs that stabilize the situation.

2. If the cause is kidney

According to Kidney Foundation, Kidney injuries will be treated based on the problem that caused them. To stabilize the patient, hemodialysis, medicines to control the amount of vitamins and minerals in the blood, and drugs that stabilize the volume of fluids in the body may be necessary.

3. If the cause is postrenal

If the cause of the urinary tract obstruction is mineral stones, shock wave lithotripsy is usually the option to follow. These waves break the sediment into small pieces so that the patient can eject it more easily, thus releasing the "plug" that was preventing the urine from coming out.

If the cause is a tumor in the prostate, it is necessary to resort to surgery and subsequent approaches, depending on whether it is neoplastic or not. Radiation therapy and focal therapies are the most common treatments for prostate cancer.

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Oliguria, a symptom of an underlying disease

In conclusion, oliguria is not a disease in itself, but a clinical sign that indicates a failure at the vascular, renal or urinary tract level.

Its approach depends entirely on the underlying cause, Well, a kidney injury has nothing to do with prostate cancer, for example. Faced with a decrease in urine, it is recommended to visit the doctor.