Anuria

Anuria Definition

Anuria is the medical term for the non-passage of urine. The word is derived from its two component parts, “uria” being a modern Latin derivative of the earlier Greek word “ouron” or “ouria” meaning urine and the prefix “an” is a contra-indicator meaning that anuria simply means “no urine”.

As a medical condition, it is more correctly referred to as anuresis but in practice the two words tend to be regarded as interchangeable. A related but less extreme condition, Oliguria (hypouresis), refers to the production of abnormally small amounts of urine and in many ways the two conditions tend to have similar causes requiring similar treatments and oliguria may progress to become anuria. The actual name given to the condition is purely dependant on the daily volume of urine produced with oliguria normally referring to urine production of less than 400 ml but more than 80 ml and lower levels being regarded as anuria although the dividing between the two conditions is rather vague with different authorities placing it anywhere between 50 and 100 ml/day.

Anuria is a symptom not a disease and there is always an underlying cause for this condition. It is frequently accompanied by other symptoms such as nausea, vomiting and lack of appetite.

Causes of Anuria

The diagnosis and treatment of anuria are complicated by the fact that there is no one single cause of this condition and the first step is always to determine the nature and physical location of the problem. It is understandable that most people would immediately suspect that kidney disease is likely but this is not always the case. The causes of Anuria may stem from problems before the kidney, with the kidney itself or after the kidney and are usually referred to as: pre-renal, renal or post-renal.

• Pre-renal Causes

  – The kidneys need a good steady supply of blood in order to operate at optimum efficiency and any form of decreased cardiac output or other compromises to the circulatory system such as vasoconstriction or vasodilation can seriously degrade the blood supply. There are many other causes including hypovolemia which simply means an inadequate volume of blood. This can come about as a result of trauma such as a haemorrhage, serious burn, or following diarrhoea, vomitting, use of diuretics, pulmonary oedema or due to fluid loss during an operation or from a post-operative drain to a wound. The body’s organs, including the kidneys, can also be starved of blood due to low systemic vascular resistance or other causes of hypotension such as sepsis, shock, drugs or anaphylactic shock. Arrhythmia, myocardial infarction, cardiomyopathy, cardiac tamponade, compression of the renal vein or inferior vena cava can also seriously affect blood flow. Certain types of diabetes and pancreatitis can also be a causative factors.

• Renal Causes

  – There are various causes of anuria due to a malfunction of the kidney itself. In some patients this may be due to having inherited congenital kidney disease and this is more likely where there is a known family history of renal disease. Vascular diseases such as renal artery thrombosis, renal vein thrombosis or vasculitis can cause kidney damage as can autoimmune and other systemic diseases. The parts of the kidney normally affected are the glomerulus and the renal tubules. Some of the conditions which may occur include renal vascular exclusion, papillary necrosis, glomerulonephritis, cortical necrosis and acute tubular necrosis. There are a considerable number of drugs considered to be nephrotoxic including diuretics, NSAID, penicillin and angiotension-converting enzyme (ACE) inhibitor.

• Post-renal Causes

  – Some cases of anuria are due to post-renal causes where the passage of urine is impaired due to a physical obstruction. This can range from a lower urinary tract infection to tumours or calculi (stones) and an enlarged prostate gland is a common cause of the problem in male patients.

Anuria Diagnosis & Symptoms

As anuria is a symptomatic condition, its presence is self explanatory and diagnosis is centred on the investigation of the underlying cause. The first step is likely to be the performance of an ultrasound scan in order to establish whether any obstruction is present, especially calculi. A urine sample will need to be taken for an in-depth analysis with particular reference to crystals and casts and a blood sample may also be required along with other routine checks of blood pressure and heartbeat. It may be necessary to insert a urinary catheter into the bladder at some stage. Careful monitoring of fluid intake and urine production are normally required in order to establish the severity of the problem. Once the initial tests have been completed, it will be known whether the condition stems from pre-renal, renal or post-renal causes and an appropriate course of treatment can then be formulated. Anuria is rarely seen in cases of chronic kidney disease but it can be associated with acute kidney injury (AKI) whether due to toxins or other causes. In some cases AKI may develop following a previous bacterial infection such as a streptococcal infection leading to a post-infectious glomerulonephritis. Various other symptoms may be present giving useful diagnostic clues such as the presence of oedema, anaemia or congestive heart failure. Swollen joints possibly accompanied by a characteristic butterfly rash would suggest that systemic lupus erythematosus may be playing a part in the condition. AKI and anuria are commonly encountered in critical care where they often form part of a major systemic failure such as MODS (multiple organ dysfunction syndrome).

Anuria Treatment

Anuria or Anuresis is a medical emergency and immediate expert medical assistance is required. Although many forms of alternative therapies are said to be available to help with the condition, only a doctor can effectively diagnose the specific underlying cause and provide suitable effective treatment. Each course of treatment will be tailored to the individual circumstances. In some cases surgical intervention will be required whereas in others, such as a lower urinary tract infection a simple course of antibiotics may suffice. Pre-renal and renal cases may require a longer course of treatment often centring on cardiopulmonary resuscitation, stabilising the heart-rate and blood pressure and carefully controlling fluid intake so as to closely match urine output. Drugs are available to increase the blood flow such as Dextrose and Dobutamine or to increase urine production such as Mannitol but the latter in particular should be used with great caution as there are some contraindications. All potentially nephrotoxic drugs should be withdrawn and blood electrolyte levels closely monitored. In short, the treatment is generally designed to give the kidneys an easy time. Renal anuria due to tubular necrosis can be reversible and after about eight days of very carefully controlled treatment with frequent monitoring of fluids, glomerular function normally returns. Tubular function can take a little longer but a full recovery normally follows.

Complications of Anuria

In the majority of cases recovery is straightforward but, as with all illnesses, there can be some future complications. With Anuria, most of the potential complications arise from the hidden factors which gave rise to the problem in the first place and for example those suffering from cardiovascular problems may still be affected by conditions such as fluid and sodium retention, pulmonary oedema or congestive heart failure requiring long-term medication. Haematological abnormalities such as anaemia or platelet dysfunction may need frequent monitoring. In cases involving infections, there is always a danger of a recurrence. A serious complication occurs when it proves impossible to adequately control potassium levels resulting in hyperkalaemia which not only threatens the kidneys but also results in cardiac arrythmias and other ECG abnormalities. In such cases, haemodialysis (or possibly peritoneal dialysis) is normally required.

In summary, anuria (anuresis) is always considered to be a medical emergency. Without treatment this can be a life-threatening condition. It should be noted however that anuria is a fairly common occurrence following surgery involving the use of a urinary catheter. It is not uncommon for the catheters themselves to become kinked so causing the problem. So although anuria always presents the same unpleasant symptoms, it has many possible causes some more serious than others and the important thing to remember is that this condition invariably requires expert medical attention.