- decreased urine production
Decreased urination result from decreased blood circulation to the kidneys due to low overall blood volume, or to kidney disease, or to a blockage of urine flow out of the kidney. It can indicate a serious problem.
What is going on in the body?
The kidneys produce urine by filtering the blood. Decreased urination is related to one of three problems:
- blockage in the tubes that carry urine from the kidneys to the outside of the body
- insufficient blood reaching the kidneys, so they cannot make adequate urine.
- the kidneys' normal response to dehydration, which is to conserve fluids
- kidney damage, which makes the kidney unable to filter
What are the causes and risks of the condition?
Causes of decreased urination can be divided into three categories:
Insufficient amounts of blood reaching the kidneys (physicians call this a "pre-renal" cause). This may be due to:
- blood loss
- dehydration or decreased intake of fluids and/or food from vomiting, diarrhea, excessive sweating, or inability to take in fluids. Medicines, such as a diuretic, or water pill, can also cause depletion of fluid and salts.
- a heart that cannot pump enough blood to the kidneys, which can occur in heart failure
- low blood pressure from shock or a serious infection. Medicines, such as those used to treat high blood pressure, can also cause low blood pressure.
Kidney damage (physicians call this category "renal"). This may be due to:
- acute tubular necrosis, a type of kidney injury caused by low blood pressure or other injuries to the kidney. Another cause is a substance that is toxic to the kidney. Examples are the antibiotic gentamicin, the metal mercury, or contrast agents used in certain X-ray tests.
- autoimmune disorders, which means that a person's immune system attacks his or her own body. An example is systemic lupus erythematosus, or lupus, a condition that can affect many areas of the body including the kidneys.
- chronic renal failure, which is usually a complication of long-standing diabetes or high blood pressure. An inherited condition called polycystic kidney disease is another cause of kidney failure.
- glomerulonephritis, another type of kidney damage that may occur after an infection
Blockage in the tubes that carry urine from the kidney (physicians call this category "post-renal"). This may be due to:
- cancer or a tumor in the bladder or prostate
- kidney stones that affect both kidneys, or a kidney stone in the only working kidney, either of which is unusual
- prostate enlargement, also called benign prostatic hyperplasia, a condition usually found in men older than fifty
Other causes are also possible. Sometimes, the cause cannot be found.
What can be done to prevent the condition?
Prevention depends on the cause. Avoiding certain medicines can prevent some cases. Drinking enough fluids can prevent cases due to dehydration. Effective treatment of diabetes and hypertension can prevent some cases due to kidney failure. Many cases cannot be prevented.
How is the condition diagnosed?
In some cases, the diagnosis is obvious from the history and physical exam. In other cases, further testing is needed. Blood or urine tests may be ordered, depending on the suspected cause. Sometimes, the urine is collected over a 24-hour period to get an exact measurement of the amount of urine being made and whether that urine contains protein or blood.
Special X-ray tests of the kidneys and bladder may also be done to find an obstruction or blockage to urine outflow. In some cases, a procedure called a kidney biopsy is needed. A special needle is inserted through the skin and into one of the kidneys. A tiny piece of the kidney is then removed with the needle and sent to the lab for examination.
Long Term Effects
What are the long-term effects of the condition?
Long-term effects are related to the cause. Most cases of dehydration can be treated, and the amount of urine returns to normal. In these cases, there usually are no long-term effects. A person who has kidney failure may need a kidney transplant or dialysis.
Dialysis is a procedure to filter the blood. The person usually has surgery first to implant a shunt in the arm, and is then hooked up to a blood-filtering machine three times a week. In these cases, the decreased urination is usually permanent.
If the cause is a serious infection or cancer, death may result. If the decreased urination is a result of obstruction (that is, it is post-renal) relieving the blockage in time can save kidney function.
What are the risks to others?
Decreased urination is not contagious, so there are usually no risks to others.
What are the treatments for the condition?
Treatment is directed at the cause. A person who is dehydrated is given fluids. Fluids can be given through an
intravenous line if the person is unable to drink. An intravenous line is a thin tube that is inserted through a person's skin and into a vein, usually in the hand or forearm.
Someone with an infection may be given antibiotics. A person with a tumor or prostate enlargement may need surgery. A person with kidney failure usually needs a kidney transplant or dialysis. There are some treatments for glomerulonephritis that may save the kidneys.
What are the side effects of the treatments?
Side effects depend on the treatments used. Antibiotics may cause an allergic reaction, stomach upset, or colitis. Any surgery carries a risk of bleeding or infection. Dialysis has many risks, including salt imbalances, infection, and death. Transplantation requires the patient to take medications that suppress the body's immune system, leading to an increased risk of infections and cancer.
What happens after treatment for the condition?
Treatment usually cures a person with dehydration. Relieving obstruction may preserve kidney function if done early. Acute kidney failure can be completely reversible. An individual with chronic kidney failure often needs lifelong dialysis or a transplant.
How is the condition monitored?
The amount of urine output can be monitored closely if needed. Other monitoring is related to the cause. For example, a person with diabetes needs frequent blood tests to monitor blood sugar levels, urine protein, and kidney function.
Harrison's Principles of Internal Medicine, 1998, Fauci et al.