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NEPHROLOGY:

            Nephrology is the field of Medicine that deals with health and diseases of the kidneys. Due to various functions of the kidneys, the specialty of Nephrology also includes Hypertension (High Blood Pressure), Acid-Base disorders, Disorders of Water metabolism (Edema and Diabetes Insipidus), Disorders of Electrolyte metabolism (Salt, Sodium, Potassium, Calcium, Phosphorus, Magnesium). The physician who is trained to treat such disorders is called a NEPHROLOGIST.

            In contrast UROLOGY is a surgical specialty dealing with tumors and other anatomical abnormalities involving genito-urinary system (Urethra, Prostate, Urinary Bladder, Ureters and Kidneys).   A physician who is trained to treat such disorders is called UROLOGIST.

KIDNEYS:

HOW DO KIDNEYS WORK?

        Each kidney has millions of tiny filters called 'Nephrons.' Renal artery brings the blood  to pass through these nephrons.   As  the blood passes through, it is filtered. As much as 180 L of fluid with all the essential and non-essential chemicals are filtered per day. Almost 178 L of fluid and the essential chemicals and electrolytes are returned to the blood per day by the 'tubule'.  In addition tubules and other cells synthesize and add various essential chemicals and hormones to the blood.   Unwanted  chemicals  and   those essential chemicals  which are  present in the blood in excess, are left in the 2 L of fluid to be excreted as urine. But such filtering and selectively reabsorbing certain substances is only on of the many functions of the kidneys.  For a better understanding of the other functions of the kidney please read 'What do kidneys do?'

WHAT DO KIDNEYS DO?

                All organ systems (Brain, Heart, Lungs, Intestines, Liver, Muscles, Nerves and all other tissues (with the millions of natural chemical reactions that occur in them) could function only in an appropriate, very restrictive and sensitive 'internal environment'. Kidneys are the primary organs which sense any alterations in such internal environment and take appropriate corrective measure to restore it to normal.

                Components of Internal Environment:

                                                                 BLOOD PRESSURE
                                                                 OXYGEN DELIVERY TO TISSUES / ANEMIA
                                                                 WATER CONTENT OF THE BODY
                                                                 INTERNAL ENVIRONMENT
                                                                 INTERNAL CHEMICAL ENVIRONMENT
                                                                 HORMONES

                    1.   Blood Pressure:   All organs need to be supplied with blood at certain pressure.  Maintaining such a perfusion pressure is dependant on Blood Pressure. Kidneys play a major role in maintaining and regulating Blood Pressure.  
                          When kidneys fail, such a regulation is not available and patient's Blood Pressure will increase, causing Hypertension. The resulting hypertension could further affect various organs. The heart is further stressed, since it has to pump against such a high pressure within the blood vessels.

                    2.    Oxygen delivery to the organs and tissues:    All organs and tissues need Oxygen.  It is delivered to the those organs by the blood. Red blood cells (RBC) in the blood are the 'box cars' to transport the oxygen. If there is not enough RBCs then the oxygen delivery system will be inadequate.   Kidneys monitor such 'trafficking of oxygen.'  If kidneys sense that less oxygen is being transported, then they try to add more 'box cars' (RBCs) to the blood to carry more oxygen.  The kidneys do it by producing more of  a 'bone marrow stimulant' called Erythropoietin. Erythropoietin stimulates bone marrow to produce more RBCs.
                         When the kidneys are diseased, such a regulatory function of the kidneys to ensure that there are enough 'box cars' (RBCs) to carry the oxygen is impaired. Consequently, there are not enough RBCs in the blood causing anemia.

                    3.   Water content of the body:  For appropriate function of all the tissues and organs of the body, the water content of the body should be normal. When the water content of the body increases the organs and tissues get 'water logged'; and when the water content is low the tissues and organs are 'dehydrated'.   Both these abnormalities adversely affect the body and causes malfunction of various organs and tissues.  Kidneys constantly monitor the water content of the body and maintain at normal levels to the extent feasible by limiting or increasing the elimination of water from the body in the form of urine.
                          When the kidneys are diseased, such a regulatory function of the kidneys to ensure that the 'humidity' (Hydration) of the internal environment is maintained,  is impaired.   Consequently, more fluid could be lost via urine even when the body is dehydrated, further worsening the functions of all organs and tissues; or more fluid is retained due to decreasing urine volume, and cause dysfunction of organs and tissues as they get water logged.  Such excess retention of water causes swelling of the body  (legs, arms, face and abdomen).  Such swelling is called edema. Since heart is the organ to pump the fluid (lymph and blood) around, such excess fluid retention could also cause heart failure (congestive heart failure).

                    4.   Internal chemical environment:        For proper function of various organs and tissues, the internal chemical environment need to be monitored, regulated and maintained within a narrow range of variability.  Some of the chemicals (Acid-Base, electrolytes) and the narrow ranges they need to be maintained in are:

                     Kidneys are the primary organs that monitor, regulate and maintain such a delicate and fragile internal chemical environment. They do this by adding or removing chemicals from the blood. At other times they add or remove  hormones to and from  the blood.   For example, if the Calcium level is low, kidneys convert pro-vitamin D  to active vitamin D.  (For practical purposes, the only organ that generates the active vitamin D is the kidney).  The active vitamin D then transfers calcium from the bone to the blood.   It also makes the intestines absorb more calcium from the food  and the blood calcium level is thus maintained on an ongoing basis.  When the kidneys are affected this mechanism suffers and the blood levels of calcium could decrease (Hypocalcaemia) causing other complications.

               5. Hormones: Many hormones that are secreted by various glands in the body (like Insulin, Thyroid etc.,) are removed by the kidneys after such hormones have served their purpose or when they are in excess.

KIDNEY FAILURE:

                 Impairment or loss of kidney function is called Kidney Failure.  And the medical terminology for such condition is RENAL FAILURE.  When the kidneys fail suddenly or rapidly, then it is called ACUTE RENAL FAILURE.   When they fail gradually over a period of years, then it is called CHRONIC RENAL FAILURE.  In both cases, the internal environment that is needed for the other organs and tissues to function is adversely affected.  All tissue and organs have some ability to cope with in an adverse environment especially if such adverse changes occur slowly as in chronic renal failure.   Patients with chronic renal failure, therefore,  are able to tolerate without great discomfort until such changes are profound.  But when such changes occur abruptly, the tissues and organs do not have the ability to adapt.   The patients with acute renal failure, therefore,  experience profound discomfort due to multiple organs failing.