What are the major parts and functions of the urinary system?

The functions of the urinary system include regulation of body fluids, removal of metabolic waste products, regulation of the volume and chemical makeup of blood plasma, and excretion of toxins from the body. The major parts of the urinary system are the kidneys, the urinary bladder, two ureters, and the urethra, and in men the prostate. Each component of the urinary system has a unique function. Urine is manufactured in the kidneys. The urinary bladder serves as a temporary storage reservoir for urine. The ureters transport urine from the kidney to the bladder, while the urethra transports urine from the bladder to the outside of the body (it also carries semen; for more about the urethra and male reproduction, see the chapter “How Diabetes Affects the Reproductive System”).

Why is it important for a person with diabetes to drink enough water each day?

One reason that a person with diabetes-or even without diabetes-needs to drink enough water each day is dehydration. If a person with diabetes becomes dehydrated, then major problems can occur with blood glucose levels (and vice versa). The kidneys need water to eliminate the body’s excess glucose and some wastes, so if a person does not drink enough water, the kidneys will look elsewhere in the body for fluid in order to function-which means a person will become drier, usually first in the eyes and mouth. In addition, the higher the glucose level, the more fluids a person drinks (and why thirst is one of the symptoms of diabetes). The symptoms of mild dehydration include thirst, headache, dry mouth and eyes, dizziness, fatigue, and dark-colored urine. Severe dehydration causes all those symptoms plus low blood pressure, sunken eyes, weak pulse and/or rapid heartbeat, confusion, and lethargy. It is interesting to note, too, that older people with or without diabetes do not get dehydration symptoms as readily as younger people. Thus, if an older person has diabetes or uncontrolled glucose levels, he or she may not be diagnosed with dehydration as readily.

On average, what percentage of a person’s daily intake of water comes from drinking water?

Only about 50 percent of a person’s daily water intake comes from drinking. Nearly 40 percent of water intake comes from eating certain foods, as water is a major component of most foods (these numbers are only approximations; the percentages fluctuate for each person and for the food and liquids they consume each day). For example, fruits and vegetables may contain more than 90 percent water.

Does drinking water lower a person’s blood glucose level?

No, this idea is a myth. Drinking an adequate amount of water helps eliminate toxins and supports a person’s kidney function. What lower a person’s blood glucose level are insulin, exercise, and the body’s kidney function.


What are the kidneys?

The kidneys are located on each side of the spinal column in the lumbar region, just underneath the ribcage. The kidney has two layers: the outer layer, called the cortex, which is reddish brown and granular, and the inner zone, the medulla, which is a darker, reddish brown in color. The medulla is subdivided into six to 18 cone-shaped sections called the pyramids. The pyramids are inverted so that each base faces the cortex and the tops project toward the center of the kidney. Separating the pyramids are bands of tissue called renal columns. A renal lobe consists of a renal pyramid and its surrounding tissue.

What are the major roles of the kidneys?

The kidneys have several important roles in the human body. The two kidneys most people have (people have been born with one kidney or may have a kidney in the “wrong” place, such as low in the pelvic area) are responsible for filtering the blood. They help control blood pressure by producing rennin, an enzyme that regulates the volume of fluid in the body. They are important to maintain healthy levels of minerals, such as potassium, chloride, and sodium. They also are responsible for regulating concentrations of phosphate, which is necessary in maintaining the body’s pH by making sure the body does not become too acidic. They also process two major hormones, erythropoietin and vitamin D (yes, bioactive vitamin D is considered a hormone). These hormones help produce red blood cells and help the body convert vitamin D through the skin by the action of sunlight on the skin, respectively.

Anatomy of the human kidney.

How much blood is filtered daily by the kidneys, and how much is filtered in an average lifespan?

The kidneys filter about 120 to 150 quarts (113 to 142 liters) of blood daily and produce about 4 ounces of filtrate per minute. Each day, about 1.5 to 2 quarts (1.4 to 1.9 liters) of urine are eliminated by the kidneys and eventually excreted. The entire blood supply is filtered through the kidneys 60 times per day, with the kidneys receiving 20 to 25 percent of the total heart output, or approximately 2.5 pints (1,200 milliliters) of blood per minute. This means kidneys in a person living 73 years have filtered almost 1.3 million gallons of blood.

What are kidney stones?

Most people who have had a kidney stone attack (called renal lithiasis) will tell you it is a very painful experience. The stones are usually small, hard deposits that form inside the kidneys and are made of minerals and acid salts. They often affect many places along the urinary tract from the kidneys to the bladder-and can be in one or both kidneys. They seem to form when the urine becomes concentrated and/or when the urine contains more crystal-forming substances, such as calcium or uric acid, than can be diluted by the fluid in the urine. The stones are most commonly classified as calcium, struvite, uric acid, and cystine stones-all of which form for various reasons.

Are kidney stones connected to diabetes?

For some people, yes, there may be a connection between the development of kidney stones and having diabetes. The common risk factors include diet (especially a high intake of animal protein, sodium, and sugar-along with not drinking enough fluids); some medications (for example, in some people who take calcium supplements); a family history of kidney stones (although no one agrees upon this factor versus the influence of diet and environment); and certain health conditions, including gout, obesity-and diabetes.

Is there a rise in the number of people with kidney stones?

According to a recent study published in the Clinical Journal of the American Society of Nephrology, there appears to be a rise in the number of people with kidney stones. The researchers analyzed data from more than 150,000 people in South Carolina who experienced kidney stones from 1997 to 2012. They found that the frequency of kidney stones increased 16 percent over the study period, with the biggest increases in children, women, and African Americans. They also noted that, as past studies have shown, more men have kidney stones than women, but women in this study outnumbered the men with kidney stones among those under age 25.

According to Harvard Medical School, there seems to be no direct reason for the rise in kidney stones. There are some speculations, including the rise in obesity in recent years (and also connected to type 2 diabetes). Some scientists even mention climate change, citing that warmer temperatures may increase dehydration, one of the factors often mentioned as a contributor to kidney stones.

In the United States, what percentage of people who have diabetes develop chronic kidney disease (CKD)?

Even when it is controlled, diabetes can lead to chronic kidney disease (CKD) and eventual kidney failure. In the United States alone, it is often said that diabetes is the most common cause of kidney failure. And even though most people with diabetes do not develop CKD that is severe enough to lead to kidney failure, it is estimated that of the nearly 25.8 million people in the United States with diabetes, around 180,000 are living with CKD as the result of their diabetes.

What are the major causes of kidney failure in the United States?

According the National Institutes of Health’s National Institute of Diabetes and Digestive and Kidney Diseases, to date, diabetes affects 25.8 million people of all ages in the United States, and around 40 percent of people who have diabetes may eventually develop kidney disease (CKD). This accounts for 44 percent of all the new cases of kidney failure each year. The main reasons for kidney disease are as follows:

1.4 percent urologic diseases

2.3 percent cystic kidney

What is eGFR?

The term eGFR stands for estimated glomerular filtration rate, or flow rate in the kidneys. Doctors will often use the eGFR when assessing kidney damage, including in people who have diabetes and may have symptoms of kidney disease. For example, an eGFR of less than 60 milliliters per minute is often indicative of kidney disease. Doctors may also use other tests, such as looking for protein in the person’s urine, as even a small amount may indicate trouble with the kidneys (although everyone is different in terms of protein in the system, which is why other tests are used).

6.6 percent glomerulonephritis (or glomerular disease, an acute inflammation of the kidney’s tiny filters called glomeruli, which remove excess fluid, electrolytes, and waste from the blood and pass them into the urine)

17.6 percent other reasons

28.4 percent high blood pressure (the second major cause of kidney failure; it is important since many people with diabetes also find controlling blood pressure to be a major problem. For more about high blood pressure, see the chapter “How Diabetes Affects the Circulatory System.”)

43.7 percent diabetes

How is it determined that a person with diabetes has kidney disease?

There are five stages of kidney disease, with kidney failure the final and most severe stage. Certain numbers are associated with kidney disease, called the glomerular filtration rate, or GFR. This is a reflection of how the kidneys are filtering fluid per minute. The lower the number, the less efficiently the kidneys are working. It is estimated that if a person has a GFR of around 60 milliliters per minute, it could be indicative of kidney disease. And if a person has a GFR of 15 milliliters per minute or less, he or she is a candidate for renal-replacement therapy, or, in other words, either a kidney transplant or some type of kidney dialysis.

What is kidney failure?

Kidney failure is a condition in which the kidneys fail to rid the body of waste products. It is also considered to be end-stage kidney disease (ESRD, or end-stage renal disease). It is most often treated with a kidney transplant (if a kidney can be found and/or the patient is strong enough for a transplant) or dialysis, a blood-filtering treatment (see below). Each year in the United States, more than 100,000 people are diagnosed with kidney failure.

What are the symptoms of kidney failure?

There are several symptoms of kidney failure, including excess fluid buildup (most often seen in the legs) and a buildup of salt in the body. This is because the kidneys cannot excrete enough water and salt (in urine) from the body. This causes an increase in blood pressure, which often leads to hypertension. An indirect symptom of kidney failure is anemia owing to the decreased production of erythropoietin, a hormone secreted by the kidney that increases the rate of red blood cell production in response to falling levels of oxygen in the body’s tissues. Without adequate red blood cells, a person will have fatigue and shortness of breath, two major symptoms of anemia.

What is kidney dialysis?

Kidney dialysis is a procedure that uses a special machine to eliminate wastes, salt, and excess fluids from the blood. Dialysis is usually done because the kidneys are not functioning properly, either because of disease or injury. One of the major causes of kidney failure that leads to dialysis is diabetes, owing to high blood glucose levels. This excess amount of glucose damages the millions of nephrons, the small filtering units in the kidneys. A person usually needs dialysis when he or she develops end-stage kidney failure, or has lost about 85 to 90 percent of their kidney function.

When a patient’s kidneys fail and they have not been able to get a transplant, dialysis is really the only option left. Typically, patients require three treatments a week.

Is there any way doctors can potentially identify kidney disease in a person with diabetes?

Yes, there are ways in which doctors can potentially identify kidney disease in a person with diabetes. They use what are called markers, or chemicals produced by the body that help determine possible problems with the kidneys. In particular, doctors look at A1c values to see whether a person who has diabetes has been controlling his or her blood glucose levels in the long term. They also can assess damage to blood vessels of the kidneys (and the heart) by checking on advanced glycation end products (AGEs). Doctors also check on the kidney levels themselves, including the glomerular filtration rate (GFR) and serum albumin.

Doctors are also using several new markers to determine possible kidney disease in people with type 1 and type 2 diabetes. For example, neutrophil gelatinase-associated lipocalin (NGAL) is a protein that is produced in response to a decrease in blood flow to the kidneys or a trauma to the kidneys. Another is the enzyme N-acetyl-beta-D-glucosaminidase (NAG). An increase in activity of this enzyme may be connected to uncontrolled diabetes.


What is a ureter?

There are two ureters, which are tubes extending from the kidney into the urinary bladder. Each ureter is 10 to 12 inches (25 to 30 centimeters) long. They begin in the kidneys as thin, hollow, narrow tubes and widen to 0.5 inches (1.7 centimeters) as they enter the bladder. Urine is transported to the bladder via the two ureters.

Where is the urinary bladder located?

The urinary bladder is located in the abdominal cavity. In males, it is behind the rectum and above the prostate gland. In females, it is located much lower, behind the uterus and upper vagina.

How much urine can the urinary bladder hold?

The urinary bladder is highly distensible and can vary in its capacity. As urine fills the bladder, at moderate capacity, it expands to about 5 inches (12 centimeters) long and hold 1 pint (473 milliliters) of urine. The bladder can expand to twice that capacity if necessary. It usually accumulates 0.63 to 0.85 pints (300 to 400 milliliters) of urine before emptying, but it can expand to hold 1.27 to 1.69 pints (600 to 800 milliliters).

How does the urethra differ in males and females?

Urine is transported to the outside through the urethra, which is a thin, muscular tube that extends from the urinary bladder to the exterior of the body. The length and structure of the urethra differ between males and females. In males, the urethra is about 8 inches (20 centimeters) long and extends from the urinary bladder to the exterior. It has the dual function of transporting semen as well as urine out of the body. The female urethra is only about 1.5 inches (3 to 4 centimeters) long and extends from the bladder to the exterior opening.

What is urea, and where is it produced?

During the process of metabolizing proteins, the body produces ammonia. Ammonia combines with carbon dioxide to form urea. Urea is the major organic component in the urine; it is eliminated by the kidneys. Humans generate about 0.75 ounces (21 grams) of urea each day.

What is the composition of human urine?

Human urine is composed mostly of water containing organic wastes as well as some salts. The composition of urine can vary according to diet, time of day, and diseases, but overall, it is mostly water (95 percent) and organic waste products (5 percent), such as urea, uric acid, and creatinine, along with some other organic chemicals.

How are urine tests used in diabetes diagnoses?

Urine tests were once used to detect glucose in a person’s body. In addition, many doctors would taste a person’s urine for sweetness-an indication of diabetes (the excess glucose, or sugar, eliminated in the urine)-or pour the urine into sand to see whether it was sweet enough to attract insects. Now most health care professionals rely on blood tests, which are much more accurate to determine diabetes. That being said, urine tests do have a place in diabetes diagnoses. For example, tests for protein in the urine may be conducted if a person with diabetes is suspected to have kidney damage. Tests for ketones in the urine may indicate hyperglycemia, too.

Is urine always yellow in color?

Normally, dilute urine is nearly colorless. Concentrated urine is a deep yellow; colors other than yellow are not normal. Food pigments can make the urine red, and drugs can produce colors such as brown, black, blue, green, or red. Urine may also be brown, black, or red owing to disorders or diseases such as severe muscle injury or melanoma. Cloudy urine suggests the presence of pus, due to a urinary tract infection, or salt crystals from uric acid or phosphoric acid.

Is frequent urination one of the signs of diabetes?

Yes, among other symptoms, frequent urination is often one of the signs of type 1 and type 2 diabetes. It is a symptom of high blood sugar, or hyperglycemia, or an overall rise in blood (or plasma) glucose. (For more information about the fasting plasma glucose test to measure glucose levels, see the chapter “Coping With Diabetes.”)

Is there a connection between high uric acid levels and diabetes?

Uric acid is a chemical that is created when the body breaks down substances known as purines. These are found in some foods and drinks, including liver, seafood, dried beans and peas, and beer. In people without high uric acid problems, the uric acid dissolves in the blood and travels to the kidneys, and most of it is excreted in the urine. But often, the body produces too much uric acid or the kidneys don’t excrete enough, causing uric acid to build up in the blood. This buildup can create sharp crystals that eventually form in joints, causing pain and inflammation. (If a person has an excess of uric acid in the body, it is called hyperuricemia, with a blood uric acid level greater than 7 considered to be uncontrolled.) One of the more common results of such a buildup is gout.

Recent studies have shown that people who have problems with uric acid in the blood also have a nearly 20 percent increased risk of developing diabetes, along with a more than 40 percent increased risk of developing kidney disease (also often associated with diabetes). The studies do not prove that uncontrolled uric acid levels cause these health problems, but there seems to be an association between high uric acid levels and the risk of developing these two diseases.

Diabetics are more prone to urinary tract infections, which occur when bacteria contaminate the bladder, ureters, or kidneys.

What is a urinary tract infection?

A urinary tract infection, or UTI, is caused by different types of bacteria (usually E. coli), most often from the bowels. The bacteria often travel up the urethra to the bladder, the most commonly affected organ. If the infection is in the bladder, it is called cystitis (a lower urinary tract infection), and if it is in the kidneys and ureters, it is called pyelonephritis (an upper urinary tract infection). Symptoms include a burning sensation when urinating, strong-smelling urine, fever or chills, a pain in the back or abdomen, and cloudy, dark, or bloody urine.

Why are women more prone to urinary tract infections?

Women are ten times more likely to suffer from urinary tract infections (UTI) than men. More than 50 percent of women will have a UTI at some point in their life. The main reason is that the urethra in women is much shorter, making it easier for bacteria to reach the bladder and cause an infection. It also becomes more of a health problem if the woman has diabetes.

Do people with diabetes have more urinary tract infections?

Yes, people with diabetes seem to be more prone to developing urinary tract infections (UTI) than people who do not have diabetes. Some statistics indicate that people with type 1 and type 2 diabetes are about twice as likely to experience urinary tract infections as people without diabetes. This increased risk of UTI for diabetics may be due to several reasons. The person may have poor circulation because of diabetes, which lowers the ability of white blood cells to travel in the bloodstream and fight off infection. And if he or she has high blood glucose, it can damage the nerves of the bladder, so the person cannot sense when the organ is full. The person also may have trouble controlling the muscles that help release urine, causing bacteria to grow within the bladder.