Low Urine Output (Oliguria) – Causes, Symptoms, Diagnosis & Long-term Outlook

The decreased output of urine, medically termed as oliguria is defined as the condition when the urine output is less than 400 ml daily in adults, less than 0.5 ml/kg/h in children ^[1] and less than 1 ml/kg/h in infants. It is also known as hypouresis, which literally translates to 'not enough urine'.

In medical terms, oliguria marks the onset of possible renal failure in the future and has been applied as the gauge for the diagnosis of acute kidney injury (AKI) also referred to as acute renal failure. Oliguria is considered as the earliest indicator impaired renal function and is mostly^[1] acute.

Causes Of Oliguria

The aetiology of decreased urine output can be described as being pre-renal, renal and post-renal. Pre-renal cause of oliguria is blood-flow related issues within the kidneys. When there is a lack of blood supply to the kidneys, its functioning can take a halt even if it is otherwise functioning well.

The lack of blood flow is another factor resulting in decreased urine output, as your kidneys are unable to perform its functions. The renal related causes for oliguria can also be classified as renal(intrinsic kidney disorders) and post-renal disorders (outlet obstruction). The pre-renal causes include respiratory distress syndrome, haemorrhage, perinatal asphyxia, haemolysis, congenital heart disease etc.

The intrinsic renal causes include acute tubular necrosis, exogenous toxins, endogenous toxins, congenital kidney disease, vascular and transient renal dysfunction of the newborn. And the post-renal ^[2] causes include bladder outlet obstruction, neurogenic bladder, and ureteral obstruction, bilateral.

The common causes encompassed in the aetiology of oliguria include:

1. Dehydration

Dehydration is the primary cause of oliguria. It is understood that the lack of adequate water in your body can cause dehydration, the most common cause of decreased urine output. Your body usually succumbs to dehydration when your body is affected with diarrhoea, fever, vomiting, or any other illness because it lacks the capability to replace the fluids that have been lost from your body. Thus, your kidney retains whatever fluid that is remaining in your^[2] body.

2. Total urinary tract obstruction

Urinary tract obstruction or urinary tract blockage develops when the urine is unable to leave your kidneys. The obstruction can affect the kidney and in some severe cases, both the kidneys. Any damage to your kidney will inherently result in decreased performance ^[3] and even failure of the organ. Urinary tract obstruction affects your body at different speeds, where the blockage can lead to other symptoms such as nausea, body pain, vomiting, fever and swelling of the prostate^[4] .

3. Medications

Yes, medicines are always meant for your good. But it is not necessary that it will do only good to your body. Various medications and prescribed drugs have been proven to have side effects on your bodily functions^[5] and system. Medicine such as diuretics, anticholinergics, chemotherapy or immunosuppressant drugs can cause decreased urine output. Antibiotics such as angiotensin-converting enzyme (ACE) inhibitors, and gentamicin ^[6] reduces your urine output as it consumes the fluids in your body.

4. Blood loss

Any form of blood loss from your bodies, such as a wound or a deep cut that results in the ample loss of blood can result in oliguria ^[7] . This occurs because your kidney lacks the proper amount of blood that is required for its^[8] functioning.

5. Severe shock/infection

Your body can succumb to oliguria in the event of a shock. The internal changes that come across your body when you are subjected to septic, toxic or anaphylactic shock can result in pre-renal failure. It is caused in the event a decline in the circulatory volume that aids the functioning of a systematic response that normalises the intra vascular^[9] volume.

Symptoms Of Oliguria

Signs and symptoms of oliguria ^[10] or low urine output may include

• fluid retention
• dark urine
• fatigue
• body pain
• nausea
• swelling
• fever
• vomiting.

Diagnosis Of Oliguria

Medical attention is necessary to identify the cause of medical conditions. It is critical that you go to a doctor if you are facing the above-mentioned symptoms. Please take it into consideration that it is essential to go see a doctor, as there are no self-treatment options for oliguria.

Your doctor will ask you several questions before making the diagnosis such as when did the decreased urine output began, was it a sudden occurrence or a gradual one, and the current condition. It would be helpful for the diagnosis if you have a clear idea about your daily liquid intake. You should also be aware of the impact your liquid consumption has on the urine output and your everyday urine production.

Your doctor will have to perform a number of tests ^[11] to analyse and examine the cause of your condition.

1. Blood tests

The blood tests will check for signs of renal failure, urinary tract infection, bleeding disorders, high levels of blood chemicals causing kidney stones etc.

2. CT scans

A computed tomography of your pelvis and abdomen will be carried out to take a closer look into your kidneys, abdominal organs and pelvic ^[12] organs.

3. Urinalysis

Your urine will be analysed by the laboratorian to check for protein, white cells, and red cells to identify any possible onset of kidney inflammation or kidney or bladder infection.

4. Intravenous pyelogram (IVP)

IVP is an X-ray test where a contrast medium or a dye will be injected into your arm vein. The dye travels to the kidney and settles there, which is then excreted through the urine providing a complete outline of your urinary system.

5. Abdominal ultrasound

The test uses sound waves to detect the development of any form of obstructive mass in your abdomen, which can detect any sort of inflammation in your kidney.

6. Urine culture

In the urine culture test, a sample of urine will be monitored to examine any bacterial growth. The urine culture can confirm bladder or kidney^[13] infection.

Remedies For Oliguria

Generally, there are no remedies to prevent oliguria. Decreased urine output is a serious medical condition that needs immediate medical care. However, as one of the major cause of decreased or low urine output is dehydration, you can take precautions^[14] in that manner.

• Avoid dehydration by hydrating yourself often.
• If you are suffering from diarrhoea, vomiting or any other sickness - make sure to increase your fluid intake.
• Consume drinks that help regain the electrolytes.

Long-term Outlook

It is very common for people to avoid medical conditions such as oliguria as most are unaware of the drastic outlook it can result in. If you think that you may have the symptoms of oliguria, do not waste your time by overlooking the facts and get to a doctor. The long-term impact of oliguria varies from one individual to the other, depending on the cause of the condition. In the case of no treatment, decreased urine output can result in causing various medical complications such as

• heart failure
• anaemia
• platelet dysfunction
• hypertension
• gastrointestinal issues.