Receiving about 20% to 25% blood pumped by the heart, kidney is a smart, natural purification plant of your body. Working tirelessly day and night, it performs a plethora of jobs assigned to it, including purification of blood, removal of wastes, regulation of homeostasis, maintenance of blood pressure, secretion of enzymes and hormones, and so on. ^[1]

The normal kidney size is 11.2 cm and 10.9 cm for the left and right kidneys, respectively. It shows that left kidney is a bit large. Do you know, as you grow old, your kidneys shrink due to reduction of parenchymal tissue? ^[2]

Fig. 1: Kidney Diagram

According to kidney definition, you can trace the kidney location in human body to the rear of abdominal cavity under the dome of the diaphragm. This well protected space in the upper abdomen is called retroperitoneal space. ^[3] To put in simpler words, kidneys are located right under the lungs in the abdomen.

Several types of tissues make up the kidneys including small and large blood vessels, tubular structures and supporting components. ^[4]

Your kidneys do not ask for a penny in return. They only ask you not to put extra burden on them through unhealthy eating and drinking. If you don’t take care of them, they may fall victim to disorders like chronic kidney disease which 30 million Americans have. ^[5]

In addition to serving as the blood purifier, your kidneys have to perform lots of other important jobs, including the maintenance of volume of extra cellular fluids (ECF), solute concentration and electrolyte composition. ^[6] They also have a role in the excretion of waste products, secretion of kidney enzymes and hormones, reabsorption of water and solutes, and regulation of acid balance of the body, etc. ^[7]

Insufficient drinking, malnutrition and overburden can put your kidneys in trouble. By understanding the causes and effects of kidney failure and other kidney diseases on your life, you can easily improve the quality of your life. If there is protein or blood in the urine or your blood has elevated level of creatinine and glucose, you might be suffering from a kidney disease, such as diabetes, polycystic kidney disease (PKD) and high blood pressure. ^[8]

Presence of red blood cells or proteins in the urine is the indicator of kidney disease while decreased glomerular filtration rate may serve as a kidney failure symptom. Losing weight, quitting smoking and controlling your blood pressure can reduce the risk and development of kidney disease. ^[9]

Kidney Anatomy

Job of the natural filters is to purify blood and make it free from all the waste substances that it has collected from every individual cell. How do the natural filters of your body perform their complex job? For this purpose, you need to study the kidney anatomy.

Fig. 2: Kidney Anatomy

The complex kidney function suggests that the organ should have an extraordinarily complex structure. With a close examination, you can see that each kidney contains around 1,000,000 basic structural and functional units, called nephrons. Each nephron is composed of a glomerulus and an unbranched tubule with three anatomically distinct parts. ^[10]

Martini (2007) estimates the number of nephrons in each kidney to be about 1,250,000. Joined end to end, they may extend to the length of 145 kilometers!

Here follows a brief description of anatomically distinct kidney parts with a short overview of the structure of kidney and its function.

Outer, Two-Layer Membrane of the Kidney/Fibrous Renal Capsule

Lying close upon its flesh, like a skin, a proper or reflected membrane of the kidney envelopes the whole substance of the organ. It is located immediately beneath the adipose membrane and is non-cellular in nature. The oil ducts and vessels form a communication link between adipose membrane and the reflected membrane. ^[11]

The reflected membrane is made up of two delicate layers. The outer layer is more dense and fibrous than the inner one. A delicate and minute network of cellular tissue fills the space between these two layers. You can view the two coats of the membrane by blowing air between the two layers. ^[12]

The reflected membrane of kidney or fibrous renal capsule not only covers the outer surface of the kidney but also lines the renal cavity within the kidney, called the renal sinus. In addition to protecting the organ against abrasive damage, renal capsule stabilizes the positions of different structures by binding to their surfaces. ^[13] In other words, the membrane of the kidney reflects inward, thus given the name “reflected membrane”. [^[14]

Renal Cortex

Fig. 3: Renal Cortex

In the sectional kidney anatomy, you can distinguish between an outer cortex and inner medullar layer of the organ. The superficial renal portion, the cortex is granular in texture and has a reddish-brown appearance. It makes a direct contact with the renal capsule. ^[15]

Renal Medulla

Research by Martini (2007) indicates that the renal medulla is the inner layer of the kidney which houses six to eight triangular or conical structures, called the renal pyramids. The base of each pyramid lies towards the cortex while its tip projects into the sinus. Renal papilla is the name given to the tip of the pyramid.

A number of fine grooves of the pyramid converge to form papilla. Extending into the renal medulla, there are bands of cortical tissue which separate the adjacent pyramids. The granular texture of the renal columns is similar to that of the cortex.

The production of urine occurs in the renal lobes which consist of the renal columns, pyramids and the overlying area of renal cortex. Minor calyx is a cup-shaped drain that receives urine from papilla via ducts. A major calyx forms from the merger of 4 to 5 minor calyces.

On the other hand, a large funnel-shaped chamber of the kidney, called renal pelvis forms from the merger for 2 to 3 major calyces. Most of the sinus is filled by the pelvis which makes a connection with the ureter. The ureters are the tube used to drain the kidney.

Located in the cortex of each renal lobe, nephrons are the microscopic, tubular structures. The production of urine begins in these basic functional units of the kidney. ^[16]

The Hilus

The hilus is a prominent medial indentation in each reddish-brown bean-shaped kidney. It serves as the point for the enter of renal nerves and renal artery. The renal vein and the ureter also exist the kidney at this point. ^[17]

Renal Blood Supply

Weighing even less than 300g collectively, the kidneys receive a phenomenal amount of blood, about 1200 ml/minute, accounting for the 20 to 25% of the cardiac output. Branching off from the abdominal aorta, a renal artery carries blood to the kidney. The segmental arteries receive blood from the renal artery at the point of renal sinus.

The branching of segmental arteries leads to the formation of a series of interlobar arteries. The interlobar arteries, in turn, radiate outward through the renal columns, while running between the renal pyramid tissue.

Arching along the boundary between medulla and cortex, there are arcuate arteries which receive blood from the interlobar arteries and pass it to the interlobular arteries. The interlobular arteries supply blood to the cortical portions of the adjacent renal lobes. Meanwhile, they branch off to form afferent arterioles. The capillaries supplying the individual nephrons receive blood from these arterioles.

The capillaries pass on the blood to venules and small veins that combine to form interlobular veins. The arcuate veins make a connection between the interlobular veins and interlobar veins and ensure the continuity of the blood flow. As there are no segmental veins, the renal vein receives blood directly from the interlobar veins and leaves the kidney. ^[18]

Renal Nerve Supply

Turning to renal nerve supply, there is a network of renal nerves which innervate the left and right kidney and ureters. Originating from the inferior splanchnic nerves and the celiac plexus, most of the renal nerve fibers are sympathetic postganglionic fibers in nature.

After entering the kidney at the medial indentation, the renal nerve reaches individual nephrons by following the path of the tributaries of renal arteries. ^[19]

Nephron – The Basic Functional Unit of Kidney

For the proper understanding of renal function, the study of the structural arrangement and types of nephron is of crucial importance. A nephron is the smallest functional unit in your kidney consisting of a vascular component and a tubular component. There is intimate structural and functional relation of these components with each other. ^[20]

Fig. 4: Nephron - Basic Unit of Kidney Function

The vascular component of nephron is called glomerulus which is a tuft of capillaries projecting into the space, called Bowman’s capsule. On the other hand, the tubular component of nephron consists of proximal and distal convoluted tubules, and Henle’s loop. The Bowman’s capsule opens into the proximal convoluted tubule. ^[21]

The loop of Henle has descending and ascending limps. The descending limb is continuous with the proximal convoluted tubule and runs into the medullar region. The ascending limb takes the loop back into the cortical area and is connected with the distal convoluted tubule. The distal tubule joins the collecting duct. Up to eight separate nephrons empty fluid into a single collecting duct.

Based on their location and length of associated structures, you can distinguish between two types of nephrons, cortical nephrons and juxtamedullary nephrons. Most of the neurons (about 80%) in your kidney are of the cortical type.

The origin of all the nephrons lies in the cortex. One of the major differences between the cortical and juxtamedullary nephrons is that the glomerulus of the former lies in the outer layer of the cortex and that of the latter lies in the inner layer of the cortex, next to the renal medulla.

The loops of Henle show a marked difference in two types of nephrons. While the loop of juxtamedullary nephron penetrates the entire depth of medulla, the loop of cortical nephron dips only slightly into the medullar region.

The third major difference is that hairpin vascular loops or vasa recta are formed by the peritubular capillaries of juxtamedullary units only.

An afferent arteriole, formed from the branching of interlobular arteries, reaches the glomerulus to supply blood to the glomerular capillaries. On the other hand, the glomerular capillaries rejoin to form efferent arteriole (another type of arteriole).

A second set of capillaries, called the peritubular capillaries, results from the subdivision of efferent arteriole. As the very name implies, the peritubular capillaries intertwin around the tubular component of nephron. ^[22]

Location of Kidneys

Responsible for the formation of urine, the kidneys are the most important organs of the urinary system. Each of these small, beanlike structures lies on either side of the vertebral column to the back of the abdominal cavity.

Fig. 5: Kidneys Location in Human Body

The kidneys lie behind the peritoneum in a retroperitoneal position. It is because the peritoneal membrane, lining the abdominal cavity, covers only the front side of the kidneys. ^[23]

The right kidney is smaller and situated slightly lower than the left. The diaphragm forms a dome over the kidneys. Psoas muscle lies on the medial side of the kidney. The transverse abdominal muscles are on the lateral side, and the quadratus lumborum muscles are present posteriorly.

A concave bed of adipose tissues, called the renal fascia, serves as a cushion for the kidneys to rest on. It also provides support and holds the kidneys in place in the abdominal chamber. ^[24]

What are skeletal muscles? Attached to bones, these muscles render strength and movement.

Read Further: Where are Your Kidneys and Liver Located?

The Kidney Function

Tiny and lightweight organ, a kidney serves your body in three major capacities: an excretory organ, regulator of homeostasis, and an endocrine organ. ^[25]

As an excretory organ, the kidneys form the principal component of the urinary system. It is this place where the waste products are filtered from the blood for their removal outside the body in the form of urine.

Sherwood (2013) lists 10 important functions of the kidney. A variety of kidney functions are aimed at maintaining homeostasis. The neural and hormonal inputs regulate and control the kidney function in the body.

The primary responsibility of kidneys is to maintain and stabilize the extra cellular fluid (ECF) volume, solute concentration and electrolyte composition. Despite a wide range of losses and intake of water and plasma constituents through different venues, the kidneys are able to maintain their balance in the body within a narrow range that is compatible with life.

Working intelligently, kidneys keep track of the abnormal losses of ECF constituents through heavy sweating, hemorrhage, diarrhea or vomiting, and adjust the urinary output accordingly to compensate for these losses.

The urinary losses of the substances in short supply are limited by the kidneys and the access of water and electrolytes is eliminated in the urine. However, a kidney is more efficient in compensating for the excess than for deficit.

As the urinary system cannot eliminate waste products in the form of solids, they are converted into solution. And, at least, 500ml of urine is to be produced every day. For the production of urine, water is derived from the blood plasma. When water is inevitably removed along with wastes, the plasma volume may fall to a fatal level. So, if you do not drink enough water, you will eventually urinate to death.

Fig. 6: Kidney Function

As listed by Sherwood (2013) in Human Physiology: From Cells to Systems, the key kidney functions are:

Excretion of Metabolic Wastes

If the metabolic wastes are not removed, they will have detrimental effects on your health. The waste products, like urea, uric acid, bilirubin and creatinine are the metabolic wastes of proteins, nucleic acids, hemoglobin and muscle creatine, respectively. Many of these wastes are toxic to the brain and other organs of the body.

As a part of the urinary system, it is the primary job of the kidneys to remove metabolic wastes from the body. (Sherwood, 2013)

Excretion of Foreign Compounds

In addition to excreting metabolic wastes, these excretory organs facilitate the elimination of several foreign compounds, including drugs, pesticides, food additives and other exogenous, nonnutritive substances. (Sherwood, 2013)

Glucose Homeostasis

The studies conducted during the past two decades, suggest the role of kidney in the regulation of glucose homeostasis. It involves the processes of gluconeogenesis, take up of glucose from blood and its reabsorption from the glomerular filtrate.

Gluconeogenesis is the process through which liver and kidneys produce glucose from glycerol portion of fats, amino acids and other non-carbohydrate sources. The increase in the glucose release by kidneys in the fasting state is indicative of the fact they are involved in the synthesis of glucose. ^[26]

Maintenance of Water Balance

Did you ever imagine why you have to urinate very often when you drink too much? And when you do not drink enough, why does the urine volume decrease and you urinate less often?

It is an important job of the kidneys to maintain and stabilize the volume of water in the extra cellular fluids. In case of surplus supply, the excess of water is eliminated in the urine and you have to urinate in large volumes after short intervals. The reverse is true for the insufficient intake of water. ^[27]

Blood Pressure Regulation

Your body has several systems to control the blood pressure including neural receptors, ischemic response and the kidney-fluid volume system. Though the response of kidney-fluid volume takes days or weeks, this mechanism makes the greatest contribution for the regulation of blood pressure. ^[28]

Body Fluids Osmolarity

What is osmolarity? It is the measurement of the total number of solute particles in one liter of solution. Kidneys regulate the proper osmolarity of the body fluids particularly by maintaining the water balance.

In this way, the osmotic fluxes into or out of the cells can be prevented. The osmotic fluxes into the cells result in swelling while the reverse process causes shrinkage of the cells.

ECF Ions Concentration

Do you know minor fluctuations in the concentration of ions and electrolytes can have profound effects on the overall working of your body? For instance, a change in the quantity of K+ ions in the extra cellular fluids has the potential to cause fatal cardiac dysfunction. It is the responsibility of the kidneys to regulate the concentration of ECF ions.

Stabilizing Arterial Blood Pressure

For the long-term stability of the arterial blood pressure, it is essential to maintain proper plasma volume and your kidneys do that job well. They accomplish this job with the help of their regulatory role in the balance of water and salt.

Balancing Acid-Base Ratio

The abnormal concentration of acids and bases in the body can be detrimental to the healthy working of the body. The blood purifying organs are helpful in this regard as well. By adjusting the urinary output of HCO3- and H+ ions, the kidneys can maintain the proper acid base balance.

Activating Vitamin D

As an antioxidant and an essential dietary component, vitamin D, helps protect the cells from damage. ^[29]

This vitamin is essential for maintaining a good health. You can have an idea about the importance of vitamin D from the fact that its deficiency can cause many bone disorders, weakness of muscle and over a dozen internal cancers. ^[30]

Your kidneys also have a role in converting vitamin D into its biologically active form, calcitriol. Activation of the vitamin occurs with the help of an enzyme in the proximal convoluted tubule. Vitamin D in turn increases calcium and phosphorus absorptions from the gut. It also promotes bone mineralization.

Production of Enzymes

Enzymes are biological catalysts which are produced in mouth, pancreas, stomach, kidney and other organs. Salivary glands in the mouth produce saliva which also contain a salivary enzyme to digest carbohydrates.

The kidney function is not limited to excretion of metabolic wastes and the maintenance of homeostasis. It also produces some kidney enzymes that assist the organ in the execution of assigned tasks. For example, it secretes renin which is an enzymatic hormone. Renin assists the kidney in starting a chain reaction to conserve salts. (Sherwood, 2003)

Synthesis of Hormones

It sounds strange to learn that kidneys also synthesize hormones. Do you know about any kidney hormones? Well, erythropoietin is a hormone secreted by your blood purifying organs. It stimulates the production of red blood cells. (Sherwood, 2013)

Constituents of Urine

Do you know urine composition can serve as the indicator of several health conditions? Doctors suggest urine test to diagnose various disorders, such as diabetes and formation of stones in different organs of the body. The constituents of urine can also help in the diagnosis of renal, metabolic and nutritional disorders.

Fig. 7: Constituents Of Urine

According to Seager et al. (2013), the pH of the urine of a healthy person ranges from 4.5 to 8.0. However, for a person taking ordinary diet, 6.6 is the reasonable average for pH. Different types of foods tend to make the urine acidic or alkaline. For example, foods with high proteins tend to decrease the pH, whereas vegetables and fruits bring an increase it in or make it alkaline.

Around 96% of your urine is water while the remaining 4% is contributed by different organic and inorganic substances. The 24-hour urine output of an adult may contain about 40 to 50g of dissolved solids.

The major dissolved solids in the normal urine with 1400ml/24 hours output include urea, uric acid, amino acids, various ions and other compounds. Hydrogen, ammonium, sodium, calcium, chlorine, potassium, magnesium, sulphate and bicarbonate are the major types of ions in healthy urine. The concentration of various waste substances varies depending on the fluid and diet intake.

On average, an adult human takes in nearly 2400ml of water a day. Ingested liquids account for 1500ml H2O. The foods you eat contain around 700ml while catabolic reactions in the body produce approximately 200ml of water. Kidneys, lungs, skin and intestines are the organs that play a role in the excretion of water. The major excretory organs, kidneys are responsible for the elimination of 1400ml of water on daily basis.

When the normal constituents are eliminated in excess in the urine, they are considered abnormal. ^[31]

Hormonal Control of the Kidney

Antidiuretic Hormone (ADH)

The reabsorption of water from the renal tubules is the primary factor that controls the urine production. But how is water reabsorbed from the tubules? Vasopressin or ADH (antidiuretic hormone) is a pituitary hormone, produced by pituitary gland. It controls the rate of reabsorption. Aldosterone, an adrenal cortex hormone, also serves as a controlling factor.

Vasopressin increases the permeability of the wall of tubules to water. It increases blood volume and leads to the production of concentrated urine of dark yellow color.

On the other hand, in the absence of this hormone, there is less reabsorption of water into the bloodstream. Consequently, a large volume of dilute, light yellow urine is produced.

In case of nonproduction of ADH, the individuals suffer from diabetes insipidus, a rare kidney disease. The urine of such patients is extremely dilute and voluminous. ^[32]

Renin & Angiotensin

Renin is a hormone, secreted by the cells of juxtaglomerular apparatus (JGA), that plays an important role in the regulation of blood pressure. As the blood pressure or the volume of circulating blood falls too low, the JGA cells secrete it into the blood stream to activate the renin-angiotensin-aldosterone (RAA) mechanism. The RAA mechanism is responsible for raising the blood pressure and maintaining it at the normal level. ^[33]

Fig. 8: Renin & Angiotensin

In the Textbook of Basic Nursing, Rosdahl et al. (2008) claim that the release of renin into the bloodstream triggers the production of angiotensin I which is then changed to angiotensin II by the action of a converting enzyme. In addition to having a direct action on kidney, angiotensin II causes the adrenal cortex to increase secretion of aldosterone. Through the direct and indirect action, the hormone produces vasoconstriction and also increase the retention of water and salts.

Aldosterone

It is with the help of vasopressin that your body is able to stabilize the overall concentration of different substance in the blood despite widely varying intake of water. But what will you do if the water content of the body gets dangerously low?

Fig. 9: Aldosteron

When you do not drink enough or there is excessive loss of water through diarrhea or vomiting, aldosterone the hormone of adrenal cortex and the adrenal glands, comes to your rescue. This hormone triggers the reabsorption of electrolytes, especially sodium ions, from the tubules into the blood. In order to maintain electrical neutrality, the sodium ions are followed by chloride ions. Meanwhile, water follows the sodium chloride.

In this way, through the secretion of aldosterone, your body can conserve both salts and water. But the normal level of body fluids causes a decrease in the secretion of aldosterone. ^[34]

Parathyroid Hormone

There are four tiny glands located behind the thyroid gland, called parathyroid glands. Through the secretion of parathyroid hormone or PTH, the parathyroid gland plays an important role in the control and regulation of mineral metabolism. The action of PTH on kidney reduces the excretion of urinary calcium. Meanwhile, it also triggers the production of 1,25-dihydroxy vitamin D and inhibits phosphate reabsorption.

Production of 1,25-dihydroxy vitamin D causes the intestines to absorb more phosphate and calcium. Another job of PTH is to act on bones for increasing the efflux of calcium and phosphate.

As kidney function declines in the chronic kidney disease or CKD, there is a significant increase in the levels of circulating parathyroid hormone. The condition with excessive synthesis of PTH is called secondary hyper parathyroidism or SHPT.

Interesting Kidney Facts

Below is the list of some interesting kidney facts. You will not only get entertainment but also add to your knowledge about the amazing potential, incredible filtration surface, sophisticated working, control and shape of kidneys.

Fig. 10: Interesting Kidneys Facts

• Do you know each kidney in your body may contain as many as 1.25 million functional units, nephrons? ^[35]
• If joined end to end in a straight line, the nephrons in a single kidney would run for the length of 145 km! ^[36]
• Each kidney can have the filtration surface of 64.5 square feet. Doesn’t it seem incredible? ^[37]
• The glomerular filtration rate for each kidney is outstanding 125 ml per minute. (Martini, 2007)
• Do you know if there were no kidneys, your body would get over-flooded with water as you drank more? No matter how much water you drink, the fluid contents of your body would always remain at the normal level. It is all because of the regulatory role of the kidneys.
• Would you believe kidneys receive 20% to 25% of total cardiac output with 1200 ml of blood flowing through them each minute? It is a phenomenal amount of blood for the organ with less than 150g kidney weight! ^[38]
• What makes kidney a bean shaped organ? It is the medial indentation (or hilus) of kidney which gives it a beanlike form. ^[39]
• Do you know the glomeruli (and associated Bowman’s capsule) of all the nephrons are present only in the cortical region of the kidney? This is what gives the renal cortex its granular appearance. ^[40]
• Water accounts for 45 to 75% of your body weight with its percentage depending on several factors, including the amount of body fat, age and sex. ^[41]
• Generally, decrease in fat content increase the percentage of water in the body. ^[42]
• Out of the 2400ml water excreted every day, the kidneys eliminate around 1400ml. The remaining 1000ml is eliminated by the lungs, skin, small intestine and large intestine collectively. ^[43]
• The regulation of blood pressure also falls under the job assignments of kidneys. For this purpose, they take help from various renal and other hormones. ^[44]
• Different kidney hormones, like aldosterone, parathyroid hormone (PTH), antidiuretic hormone, and the systems like Renin-Angiotensin System (RAS) and Renin-Angiotensin-Aldosterone (RAA) mechanism help the kidney in maintaining blood pressure and performing other assigned tasks. ^[45]
• Do you know out of the 7 billion world population, 1.5 billion individuals are obese? And obesity is one of the major risk factors for kidney disease. ^[46]
• Serving as natural filters, the kidneys remove all the toxins and waste products from the blood that have harmful effects. It not removed, the toxic substances will contaminate the blood to a dangerous extent.
• A kidney appears no bigger than a standard mouse in its size.
• The formation of urine in the kidney starts in the glomerulus or Malpighian Body which consists of a spherical tuft of capillaries receiving blood from a short, wide afferent arteriole. ^[47]
• The nephrons are the structural and functional units of the kidney. They are capable of filtering the blood and eliminating the waste products so quickly and efficiently.
• The number of nephrons in each kidney are about 1,250,000. Joined end to end, they may extend to the length of 145 kilometers! (Martini, 2007)
• Around 30 million Americans are suffering from chronic kidney disease. ^[48]

Kidney Disease

Your body’s natural purifier and an excellent regulatory organ may fall victim to lots of renal disorders. But how will you come to know that you are suffering from an abnormality, such as kidney cancer? There are several ways to diagnose a kidney disease.

Fig. 11: Kidney Disease and Disorder

The urine test alone can give you very useful information about various renal conditions. Similarly, the abnormal blood composition can indicate the risk or confirm a particular kidney disease.

Low glomerular filtration rate, the presence of protein and red blood cells in the urine and abnormal amount of glucose in blood indicate that you are suffering from a kidney disorder. Obesity, high blood pressure, and white blood cells in the urine are some of the risk factors. ^[49]

Kidney Problems Indicators

The changes in normal color and composition of urine reflect various kidney problems as well as different other diseases. Similarly, the abnormal change in pH is also indicative of some kidney malfunctioning.

Doctors examine color, clarity, volume and odor of the urine and look for any deviation which may indicate some renal disorder. The color of freshly voided urine is usually light yellow or amber. Overhydration or dehydration may bring a change a noticeable in the urine color.

Abnormal substance in urine may change its clarity from transparent to cloudy. Freshly voided urine has a characteristic ‘aromatic’ odor. However, after decomposition in air, it starts emitting a strong, ammonia-like odor. In case, a freshly voided urine emits a strongly offensive odor, you may be suffering from some abnormality. ^[50]

Here are some of the abnormal color variations of urine as listed in “Textbook of Basic Nursing” edited by Rosdahl et al. (2008):

Clear or Colorless Urine: When urine becomes colorless, it may be due to either large amounts of liquid intake or a diagnostic sign of diabetes mellitus or diabetes insipidus. The liver disorders, such as cirrhosis and viral hepatitis also make it colorless.

Cloudy Urine: The presence of blood, white blood cells, pus or epithelial cells in the urine makes it cloudy. A cloudy urine may also indicate formation of kidney stones or bacterial infection of the urinary tract.

Bright, Neon Yellow: Do you take vitamin supplements? While taking vitamin supplements, the urine color may turn bright, neon yellow. Usually, it is not the sign of a disease.

Green Colored Urine: Present of bile pigments changes the normal light yellow or amber urine color to green. However, the green coloration may also be due to pseudomonas infection.

Black or Dark Brown: Some foods, food dyes and certain medications make the urinary fluid black or dark brown. Meanwhile, such an abnormal coloration can be contributed to hematuria (blood in urine), typhus infection and some liver disorders.

Yellow Brown: The abnormal yellow brown appearance of urine can be caused by the presence of bile juice in it.

Gold or Dark Yellow: Low fluid intake and dehydration lead to the concentration of urine. And a concentrated urine appears gold or dark yellow. At the same time, the presence of bile and inability of kidneys to dilute urine also leads to such a coloration.

Red/Pink Coloration: Some laxatives, foods and food dyes are responsible for making the urine appear red or pink. Such a coloration is due to hematuria or blood in urine. On the other hand, urine in blood can be the sign of kidney infection or cancer of bladder or kidney.

Green or Blue: Certain medications, foods and food dyes are usually the reason behind the abnormal green or blue appearance of urine.

Red Brown or Orange: The urine color turns orange or red brown due to the use of certain medications, foods and food coloring agents. Dehydration can also be the cause of such an abnormal coloration.

Hazy or Smoky Urine: Yeast infection, prostatic fluid from the prostate, chyle, hemoglobin and remnants of red blood cells have the potential to make urine appear hazy or smoky. Here chyle is the product of digestion which is normally emptied into venous system. ^[51]

Abnormal Urine Constituents Indicating Kidney Disease

Are you aware of the fact that urine composition serves as an excellent indicator of the state of your health? That is why doctors recommend urinalysis as a part of physical check or diagnosis for some disease. ^[52]

If there is an additional substance in the urine or any normal urinary constituent is in excess, it is considered an abnormal urine constituent. The abnormal urine constituents are usually indicative of the disorders of kidney or other body parts.

Seager et al. (2014) list some conditions associated with abnormally high amounts of normal urine constituents and other substances, like pus and blood. They are discussed below:

Glucosuria: Glucose is not a normal constituent of the urine. So, glucosuria or excretion of glucose into the urine is an indicator of renal or other abnormalities, like renal diabetes, diabetes mellitus and alimentary glucosuria.

Proteinuria/Albuminuria: Protein in urine refers to the condition of proteinuria. Meanwhile, albuminuria is the condition when albumin protein becomes an abnormal constituent of urine. Such symptoms may be the result of bladder infection, kidney damage or nephritis.

Ketonuria: Ketonuria results from ketone bodies as abnormal urine constituent. It usually occurs due to starvation and high fat diets. But diabetes mellitus can also be the cause for such a condition.

Pus/Leukocytes in Urine: The infection of bladder or kidney may cause the excretion of pus or leukocytes into the urine. So, you can use the presence of pus in the urine as a diagnostic sing of the bladder or kidney infection.

Hemoglobinuria: Hemoglobin is an oxygen carrier protein in the blood and does not form a normal constituent of urine. When found in the urinary fluid, it refers to the condition of hemoglobinuria. On the other hand, hemoglobinuria may be the symptom for excessive hemolysis of red blood cells.

Hematuria: As the freshly voided urine looks light yellow in color, it is not supposed to contain any red blood cells (RBCs) as normal constituents. If such a condition occurs, you call it hematuria. And the cause behind hematuria is hemorrhage in the urinary tract.

Jaundice: Jaundice expresses itself through the yellowing of the skin and whites of the eyes. You can also confirm the condition from the presence of large amount of pigments in the urine. Cirrhosis, hepatitis and blockage of bile duct are the conditions that cause the release of bile pigments into the urine.

Kidney Stone Disease

According to Margolis (2004), a renal calculus or kidney stone refers to the formation of hard, solid lump in the kidney. It is a painful condition and occurs when substances, like calcium oxalate, concentrate in the urine and coalesce to form stones.

Fig. 12: Kidney Stone Disease

The stones are of different types but those containing calcium are most common, accounting for 70 to 80% of renal calculi. Other kinds of renal calculi may be composed of uric acid and the combination of phosphate, ammonium and magnesium.

Another name for kidney stones is nephrolithiasis. When formation of stony concretions occurs in pelvic, it is called pelvic lithiasis. Urolithiasis is the formation of stones in the urinary tract or bladder.

Major Factors that Increase the Risk of Kidney Stones

There are multiple things that cause the formation of renal calculus or kidney stone. By controlling factors, like obesity, diet, medications and hydration, you can successfully prevent the kidney stones symptoms from occurring. The most common kidney stone risk factors include:

Fig. 13: Factors Lead to Kidney Stones

Obesity: The medical condition of obesity refers to the accumulation of access body fat with negative impact on the individual’s health. In addition to increasing the risk of various diseases, obesity may also reduce the life expectancy. ^[53]

Individuals suffering from obesity have a higher risk of kidney stone disease. In other words, people having higher body mass index (BMI) and waist size are at the higher risk of developing renal calculi. Also note that obese patients with nephrolithiasis mainly develop stones composed of uric acid and calcium. ^[54]

Heredity: A person with positive family history of stones is also at the risk of developing a kidney stone. Curhan et al. (1997) claim that people with family history of kidney stones are at higher risk of renal calculi than those without a family history. However, it is not clear whether the increased risk should be attributed to genetic factor or environmental exposure. ^[55]

Diet: Diet directly affects the health of every individual. Do you know everything you eat has potential even to change your brain chemistry?

Your diet is an important factor which may lead to the development of the kidney stone. However, as the metabolism of the dietary factors, like calcium, changes with age, there is a different relation between diet and renal calculi for the older people. ^[56]

Medication: Your healthcare provider prescribes medications to relieve the symptoms of an existing medical conditions. But some medicines may cause complication and lead to the formation of renal stones. Research reveals that about 1 to 2% of renal calculi are induced by drugs.

Excess use of laxatives, carbonic anhydrase inhibitors and diuretics are some of the drugs that can induce metabolic calculi. The crystallization of drugs results in the development of urinary calculi.

The drugs, like ciprofloxacin, magnesium trisilicate, ephedrine and indinavir are nefarious in this regard. In such a situation, you need to stop the use of medications to reverse the process of renal calculi formation. ^[57]

Hydration: Maintaining the hydration of your body is very important. It not only reduces the risk of kidney stones but also doctors recommend copious hydration as a part of treatment of the condition.

For example, the ideal initial treatment option for pregnant women with stones is conservative care which involves taking advantage of hydration, bed rest and analgesia.

These reasons increase the risk of kidney stones formation. Thus, taking care of all the above kidney stones causes is paramount for a happy and a healthy life. ^[58]

Kidney Stone Symptoms

Margolis (2004) lists the most common symptoms which surface in patients suffering from kidney stones. These are as follows:

Fig. 14: Kidney Stones Symptoms

• Excruciating kidney lower back pain below the ribs travelling downward to the groin.
• Sever pain in penis as the stone passes in men.
• Frequent urge to urinate but only small amounts of urine passing.
• Fatigue accompanied by pain in muscles and joints.
• Nauseated feeling followed by vomiting.
• Urgent urination with burning sensation. Discolored urine emitting an unpleasant odor.
• In case of chronic pyelonephritis, generally there appear no symptoms until enough damage to the organ has occurred. It may lead to kidney failure symptoms.
• Victim suffers from fever and chills.

Diagnosis

According to Pagana et al. (2013), around 80 percent of stones are composed of calcium oxalate and calcium phosphate; 10 percent of magnesium ammonium phosphate; and 9 percent of uric acid. Ammonium acid urate and drug related stones account for remaining 1 percent of renal calculi. ^[59]

In case you feel, or suffer from any of the above kidney stone symptoms, you shouldn’t delay to consult your healthcare provider. They will recommend to undergo kidney function test for the diagnosis of stones. Do note that the earlier you detect the stones the easier it is to remove them.

In case immediate action is not taken, the renal calculi will increase in size and number. They may aggravate the situation.

For diagnosis, doctors record the patient history and carry out physical examination. They may take blood sample to measure uric acid and calcium levels. A urine test is used to measure its volume and pH and the amount of uric acid, calcium, oxalate, sodium, citrate, urea nitrogen and sulfate present in it.

A computed tomography (CT) scan and kidney x-ray will tell you about the exact location and size of stones. A piece of stone that passes and is captured will be subjected to laboratory for its chemical content. ^[60]

Treatment

After successful diagnosis, your doctor will move on to the kidney stones treatment stage. There are two main factors which they need to take into consideration before starting the treatment. These are:

• The size of the stone.
• The place of the stone.

Small and benign kidney stones pass through urine on their own. While the bigger and the more dangerous ones cannot do the same. They need proper treatment or medication. The main treatments which the kidney patients get include:

• Initially, the patients are encouraged to drink at least 3 liters of water as an attempt to flush the stone into the bladder.
• Pain killers and medicines can help cope with the pangs of kidney pain that the patient experiences.
• Medicines which facilitate the passing of urine.
• Antispasmodic drugs to ease passing of the stone along ureter.
• Use of extracorporeal shock wave lithotripsy for the stones that are huge and unable to pass on their own.
• Performing kidney operation to remove the stones.
• In rare and advanced cases that do not respond to other forms of treatment, the patient may need to undergo kidney removal surgery. ^[61]

Prevention

To prevent the formation of kidney stones you need to take a few preventive measures. A well-balanced diet and drinking 8 to 10 glasses of water a day is a must thing. It makes sure that one’s body functions properly. You must take proper proportions of vitamins, minerals and essential salts.

If you have already suffered from a kidney stone disease, dietary change will help prevent the recurrence. The changes in diet will depend on the specific type of kidney stone involved.

In addition to dietary changes, exercise is of great importance. Regular workout will keep you fit, fresh and healthy. But the key to preventing renal calculi is excess water intake. It will improve the functioning of your kidney. And, there will be lesser chances of mineral accumulation resulting in stone formation. ^[62]

Kidney Failure

The kidney failure can be of two types, acute and chronic. When both the kidneys suddenly stop functioning, it is called acute renal failure. Whereas, in case of chronic renal failure, both the kidneys gradually cease to function.

The kidneys not only regulate the fluid and chemical balance but also filter waste materials out of the blood and excrete it in the form of urine.

Kidney disorders, complete or partial blockage in the passage of urine and decrease in the blood volume may lead to acute renal failure with symptoms developing over several days. It is a life-threatening condition because an excessive amount of water and minerals accumulates in the body.

If the cause is timely identified and treated, the kidneys can fully regain the function within days to weeks.

In chronic renal failure, a kidney suffers damage from an injury or inflammation over several months or years. Meanwhile, the healthy tissue compensates for the loss of function. The extra work load damages the healthy tissue as well and eventually the entire kidney ceases to function. ^[63]

Fig. 15: Kidney Failure

Acute Renal Failure Symptoms

• Frequent urination with only small amounts of bloody or cola-colored urine passing.
• Fluid accumulation causing the swelling of face and ankles.
• Nausea, vomiting and loss of appetite.
• Fatigue and laziness.
• Widespread itching and pain in the abdominal area.
• Shortness of breath and loss of consciousness (late stage symptoms). ^[64]

Chronic Renal Failure Symptoms:

• Frequently passing small amount of urine.
• Poor health.
• Nausea, vomiting and loss of appetite.
• Fatigue and drowsiness.
• Unexplained bleeding from gums and other parts.
• Accumulation of waste materials in the blood.
• Swelling of face, ankles and tissues around the eyes due to fluid retention.
• Shortness of breath from the accumulation of fluid in the lungs.
• Muscle spasms and loss of consciousness. ^[65]

Diagnosis

Physical examination, patient history, urine and blood tests, kidney biopsy, kidney ultrasound and CT scan are the tests and tools that can be used for both the acute and chronic cases of renal failure. MRI (Magnetic Resonance Imaging) of the abdominal area may also be carried out. ^[66]

Treatment

Relieving kidney failure symptoms requires the identification and treatment of the underlying disorder. Severe injury and damage to the organ requires emergency treatment to repair the damaged tissues. An obstruction in the urinary tract may be removed through surgery.

The use of diuretics helps reduce fluid retention in the body and bring an increase in the urine output. For the full recovery, a number of post-emergency measures are required which include fluid restriction. In case of a bacterial infection as the underlying factor, your healthcare provider may prescribe antibiotics.

If significant portion of the kidney is lost, an artificial blood filtering process, called dialysis, becomes inevitable. However, different types of kidney dialysis may be used for acute and chronic renal failure. ^[67]

Prevention

Both chronic and acute types of renal failure can be prevented by identifying and treating the potential underlying causes. The causative factors for acute kidney failure include severe injury depleting the blood volume, tumors, polycystic kidney disease, acute glomerulonephritis, certain antibiotics and high doses of nonsteroidal anti-inflammatory drugs.

Diabetes mellitus, primary kidney disorders, high blood pressure, tumors, use of nonsteroidal anti-inflammatory drugs, certain antibiotics and poisoning with heavy metals are some of the common causes of chronic renal failure. ^[68]

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