The Urinary System
4.3a The physiology of the urinary system
The urinary system consists of the kidneys, the ureters, the bladder and the urethra. An alternative name is the renal system, although strictly speaking, renal (from the Latin term for kidney) is a term that refers to the kidneys alone. The Greek word for kidney is nephron, and hence the study of the kidneys is called nephrology.
The component parts of the urinary system are illustrated in Figure 4.3a-I. It can be seen how the kidneys are situated in the upper part of the back of the abdomen. They rest, protected against the ribs, between the levels of T11 and L3. The influential acupoints on the back of the Kidney Organ (Shen Shu, BL-23) lie directly over the lower parts of the kidneys. The ureters run from the medial aspect of each kidney, down the posterior border of the abdominal cavity, to open into the bladder. The bladder sits protected within the pelvis. Note from the diagram how small the bladder is. Even when uncomfortably full the bladder rarely rises very much higher than the level of the pubic symphysis (the region of acupoint Qu Gu, RN-2). The urethra (a very similar name to that of the more proximal ureter, but a different anatomical structure) is the tube that links the bladder to the external world. It is very short in women, but longer in men because of its passage through the penis.
The major function of the kidneys is to maintain homeostasis of the composition of the blood by excreting wastes and controlling the concentrations of the various mineral salts within the blood. They do this by the formation of urine, which is a solution of wastes and salts. Other important functions of the kidneys include the control of blood pressure, control of the development of red blood cells by the secretion of the hormone erythropoietin, and production of active vitamin D.
Figure 4.3a-I The component parts of the urinary system (excluding the urethra) and related abdominal structures
The function of the ureters is to allow the free drainage of the urine into the bladder. The bladder is a reservoir that contains this steady flow of urine from the kidneys until there is an appropriate time for its expulsion. This happens through the process of urination (also known as micturition) in which the bladder contracts and the urine passes through the urethra and out of the body.
The position and structure of the kidneys
The kidneys sit at the back of the upper abdominal cavity embedded in fat. The adrenal glands sit on the top of each kidney, but do not have a direct link with the role of the urinary system. However, both the adrenal glands and the kidneys have functions that would be understood in Chinese medicine as being related to the Kidney Organ. The kidneys sit very close to a number of other deep organs, including the spleen, pancreas, liver, duodenum and the large intestine.
The tissue of the kidney consists of thousands of tiny tubes called nephrons. Each of these tubes has its origin in the outer parts of the substance of the kidney (the renal cortex). The nephrons converge to open out into wider tubes called collecting tubules, which drain into a space in the core of the kidney called the renal pelvis. The renal pelvis drains downwards into the ureter. The collecting tubules are situated in the deeper tissue of the kidney that is known as the renal medulla. Figures 4.3a-II and 4.3a-III illustrate the external and internal structure of the kidneys in some detail. Figure 4.3a-II shows the position and size of the adrenal glands, and Figure 4.3a-III indicates the location of the renal cortex, medulla, pelvis and ureter.
These diagrams clarify how the kidneys receive their blood supply from a large branch of the aorta called the renal artery. This artery branches within the substance of the kidney to provide each nephron with its own arteriole. The blood supply to the kidney is very rich. About a quarter of all the blood that has left the heart is directed from the aorta through the kidneys. This is very important because it ensures that the blood undergoes a continual and efficient process of being cleansed and returned to a state of balance.
Figure 4.3a-II Anterior view of the kidneys illustrating proximity to overlying abdominal organs
Figure 4.3a-III Longitudinal section of the right kidney
The formation of urine in the kidneys
Figure 4.3a-IV shows how the blood that reaches the nephron first enters a cluster of capillaries called the glomerulus. Here, because of a sudden restriction of easy flow, fluid containing salts, wastes and water is forced out of the glomerulus. From here this fluid passes into the cup-like origin of the nephron. However, substances such as plasma proteins and blood cells are too large to be squeezed out, and so these remain within the blood vessel. This process of draining water and small molecules from the blood into the nephron is called simple filtration.
This fluid then drains down through the tube of the glomerulus towards the collecting tubule. However, it does not yet have the composition of urine. During its passage through the nephron some of the fluid and the salts are reabsorbed back into the bloodstream. The diagram indicates how the arteriole travels on to supply the rest of the nephron with a blood supply for this purpose. Substances can also be secreted from the blood in the arteriole into more distal parts of the nephron.
These two processes of reabsorption and secretion not only make the original fluid that has been drained out of the glomerulus much more concentrated (it is nearly 200 times as concentrated as plasma fluid), but they also allow for a subtle control of its composition according to the body’s requirements. For instance, if the person is dehydrated, more water than normal is reabsorbed, and if the person is depleted in salts, more salts are reabsorbed.
The reabsorption and secretion of the fluid in the nephron are under the control of a number of hormones, including parathyroid hormone from the tiny parathyroid glands in the neck (which regulates calcium and phosphate levels), antidiuretic hormone (ADH) from the pituitary gland (which regulates the concentration of the blood) and aldosterone from the adrenal glands (which regulates the amount of sodium and potassium in the blood).
The fluid that leaves the nephron to enter the collecting tubule and thence the renal pelvis has the composition of urine. This yellow-colored fluid consists mostly (96 percent) of water, with a further 2 percent being urea (the waste product of protein metabolism) and the remaining 2 percent comprising a range of other salts including sodium, potassium and uric acid. In a healthy adult, approximately 1–1.5 liters of urine are passed a day, although this can vary from as little as 500 milliliters to as high as 3 liters, depending on the balance of fluid intake and other fluid losses.
Diuretic drugs that act on the kidney tend to inhibit the amount of water that is reabsorbed, and so increase the volume of urine entering the renal pelvis. Some diuretic drugs may also affect the reabsorption of salts. This is why some diuretics can lead to sodium or potassium depletion, and others may cause a buildup of uric acid (predisposing to an attack of gout).
The kidneys and the formation of red blood cells
Erythropoietin (EPO) is a hormone that is made within the kidneys and is released into the bloodstream in response to low levels of oxygen. It is an essential factor in the production of red blood cells from the bone marrow. When blood oxygen levels drop, the secretion of EPO is stimulated, and this in turn increases the production of red blood cells from the bone marrow. These blood cells are then available to carry more oxygen, and thereby to increase the level of oxygen in the blood.
The kidneys and the control of blood pressure
Healthy kidneys are essential for the control of blood pressure, and disease of the kidneys is one of the causes of hypertension. In addition, the kidneys act in a situation of shock (low blood pressure) to conserve fluid, and so to prevent its loss into the urine. There are at least two important hormone systems that cause the kidney to excrete more fluid when the blood pressure is high and to conserve fluid when the blood pressure drops.
The hormones involved in the kidneys’ control of blood pressure include aldosterone, renin, angiotensin I and II, and atrial natriuretic factor (ANF). ACE (angiotensin-converting enzyme) inhibitors and angiotensin II receptor blockers are drugs used in the treatment of hypertension and heart failure. They act by blocking the formation of one of these hormones (angiotensin II).
The kidneys and vitamin D metabolism
Although vitamin D is mostly manufactured as a response to the action of sunlight on the skin, it requires conversion within the kidneys to become active in the body. For this reason, kidney disease can be a cause of the disease of weakening of the bones known as osteomalacia.
The physiology of the ureters
The ureters receive a steady flow of urine from the renal pelvis at a rate of 20–100 milliliters/hour. These structures run down the back of the abdominal cavity and enter the bladder where it sits within the pelvis. The flow of urine is aided by waves of muscular contractions that are generated by the smooth muscle fibers within the ureter walls.
The urine that enters the bladder passes through a narrowing, akin to a valve, as it enters the bladder. This important structure prevents the return of urine back into the ureter (known as reflux) from the bladder. The urine enters the bladder in little spurts, which occur every 10 seconds or so.
Figure 4.3a-V The pelvic organs associated with the bladder in the female
Figure 4.3a-VI The pelvic organs associated with the bladder in the male
The bladder is a hollow, pear-shaped organ, the function of which is to act as a reservoir for urine. Figures 4.3a-V and 4.3a-VI above show a vertical section through the pelvis of a woman and a man, respectively. These diagrams illustrate the position of the bladder within the pelvis. Note how in the woman the bladder sits just in front of the cervix and womb. In the man the prostate gland sits at the neck of the bladder, surrounding the first part of the urethra.
The bladder is lined by a form of epithelium called transitional epithelium that has the ability to stretch. Within the wall of the bladder are sheets of smooth muscle, which together are called the detrusor muscle. When the detrusor muscle contracts, it forces urine out through the urethra.
In a healthy adult the desire to urinate arises when the bladder contains more than 300 milliliters of urine. At this stage, the stretch of the bladder muscle stimulates nerve impulses so that the bladder contracts spontaneously (this is a spinal reflex). Indeed, this is what occurs both in the newborn and in someone who has had a spinal injury. However, in the healthy adult, although the sensation of a desire to urinate occurs at this stage, the brain exerts an inhibitory control on this reflex until an appropriate time arises for it to occur. This voluntary control of bladder function is usually learned during the third year of life.
The physiology of the urethra
The urethra is the canal that leaves the neck of the bladder and links it to the exterior. In women, the urethra is about 4cm long, and it opens to the exterior just in front of the vaginal orifice. In men, the urethra first passes through the tissue of the prostate gland and then travels through the length of the penis to the orifice at the tip of the glans penis. Ducts open out into the first part of the male urethra through which the seminal fluid and semen are passed during ejaculation.
In both women and men the urethra passes through the region of the body called the perineum that forms the floor of the pelvis. In doing so, it passes through the pelvic floor muscles, which are slung between the pubic bone and the base of the sacrum and coccyx.
At the origin of the urethra is a smooth muscle ring called the internal urethral sphincter. This is generally maintained in a state of contraction, thus holding the urine within the bladder. In addition to the internal sphincter, the muscles of the pelvic floor provide an additional external urethral sphincter as a result of their generally high level of tone. Together, these factors exert a closing pressure on the urethra, which is released when the person intends to urinate.
Information box 4.3a-I
The urinary system: comments from a Chinese medicine perspective
According to traditional Chinese medicine, the functions of the Kidneys and Bladder are considered to be as follows.
•store Essence (Jing) and control birth, growth, reproduction and development
•produce Marrow, fill up the brain and control bones
•control the reception of Qi
•open into the ears
•manifest in the hair
•control the lower two orifices
•house the Will.41
•removes water by the power of Qi transformation.42
According to Chinese medicine, it is not only the Kidneys and Bladder that play a part in fluid balance and the excretion of waste. The Lungs, Spleen, Small Intestine and Triple Burner also have specific functions, which are described by Maciocia (1989).43 These can be summarized as follows.
The Lungs control dispersing and descending. The Lungs have the function of spreading the body fluids around the body in the form of a fine mist. If impaired, fluid may accumulate in the form of edema (often of the face).
The Lungs regulate the water passages. The Lungs also direct fluids down to the Kidneys and Bladder. If this function is impaired there may be urinary retention.
The Spleen governs transformation and trans-portation. One aspect of this is the transformation, separation and movement of fluids. In Chinese medicine the dirty part of the fluids ingested gets sent to the Small Intestine. If this function is impaired, Phlegm or Damp will Accumulate, sometimes in the form of edema.
The Small Intestine controls receiving and transforming and separates Fluids. The Small Intestine first receives food and drink from the Stomach. The Clean part is sent to the Spleen, and the Dirty part to the Large Intestine (solid) and to the Bladder (fluid). This function of separation is powered by Kidney Yang.
The Lower Burner aspect of the Triple Burner is directly related to the excretion of fluids. This is the aspect that directs the separation of the food essences into a Dirty and Clean part, and which facilitates the excretion of the dirty fluid as urine. In this way the Lower Burner is a summary of the function of the Spleen and Small Intestine.
So here it becomes clear that the Chinese medicine interpretation of the function of the urinary system is not that straightforward. First, most of the functions of the Kidney Organ do not relate directly to functions of the urinary system (e.g. storage of Essence, production of Marrow (with the exception of the effect of EPO on red blood cell production), reception of Qi, opening into the ears, manifesting in the hair and housing Will power). Second, the actual function of the urinary system, which is to permit the continual cleansing of the blood of wastes and the removal of excess fluid into the urine, would seem to be controlled in Chinese medicine by a number of Organs (i.e. Kidney, Bladder, Stomach and Spleen, Small Intestine and the Triple Burner).
It is important to bear this in mind when considering specific diseases of the urinary system, and attempting to draw conclusions about a Chinese medicine interpretation. An imbalance in the urinary system may therefore be described in terms of pathology of one or more of these six Chinese medicine organs.
Diseases of the urinary system are investigated within three distinct conventional specialties. Medical conditions that affect the kidney are treated by a renal physician within the specialty of renal medicine or nephrology. Conditions that affect the ureters, bladder and urethra, and also those conditions of the kidney that may require surgery, are treated by a surgeon called a urologist within the specialty of urology. Conditions that affect the male reproductive organs are also commonly treated by a urologist. However, those conditions that result from sexually transmitted diseases are treated by a genitourinary physician within the specialty of genitourinary medicine or sexual medicine.
The investigation of the urinary system
The investigation of the urinary system involves:
•a thorough physical examination
•blood examination to check for anemia, to assay waste products and salts in the serum, and to look for autoantibodies and other markers of specific diseases
•imaging tests to examine the structure of the urinary system, including ultrasound scan, computed tomography (CT) scan and plain X-ray images
•imaging tests to examine the function of the urinary system, including intravenous urography, cystourethrography and radioactive isotope scans
•examination of the inside of the bladder (cystoscopy)
•biopsy of the kidneys
These are each considered briefly in turn below.
The physical examination of the urinary system involves the stages listed in Table 4.3b-I.
Table 4.3b-I The stages in the physical examination of the urinary system
Examination of general appearance for the pallor of anemia and the smoky yellow tinge of uremia (this develops in chronic renal failure)
Assessment of blood pressure
Examination of the ankles for evidence of edema
Examination of the abdomen for abnormal enlargement of the kidneys or a distended bladder (the kidneys and bladder are usually not palpable in the abdominal examination, so if they can be felt, this is a sign of distension or enlargement)
Examination of the male genitalia and prostate gland: the prostate gland is examined by means of the insertion of a gloved finger through the anus into the rectum
Examination of the female genitalia:internal vaginal examination can identify uterine prolapse and posterior prolapse of the bladder wall, both causes of urinary incontinence
The most commonly performed urine tests require a midstream sample of urine (MSU). This means that the specimen is taken only after a flow of urine from the urethra has been established. The sample should ideally be free from contamination by the bacteria of the skin, although this is not always possible to ensure, particularly when collecting urine from small children. Any sterile container is suitable for a urine specimen.
Healthy urine is pale yellow and clear. The first urine passed in the morning is usually the most concentrated, and can have a deep amber color. Visual assessment of urine may reveal a pink discoloration suggestive of blood or cloudiness suggestive of infection. Both these findings are abnormal, but commonly result from benign causes. For example, a large amount of beetroot in the recent diet as well as some medications can cause the urine to become pink.
The simplest quantitative test of urine involves dipping the urine with a plastic strip that holds tiny indicator cards. These cards change color according to the concentration of a range of factors within the urine. Use of the plastic dipsticks, commonly termed stix or multistix, can give an instantaneous indication of the amount of sugar, blood, protein and white blood cells in the urine, to name just a few of the variables that can be detected. This test is not as reliable as a laboratory test, but is very commonly used in general practice to check for blood in the urine (hematuria), to give an indication of undiagnosed or poorly controlled diabetes, and to give added weight to a provisional diagnosis of urine infection.
Urine may then be sent to a laboratory for microscopic examination. This may reveal the presence of microorganisms and excessive white blood cells in the case of infection. It will also confirm the presence of red blood cells in the urine. In the diseases (classed as glomerulonephritis) that affect the structure of the tubules of the kidney, unusual tube-shaped casts of protein may be seen in the urine.
The urine can also be analyzed for the substances that are dissolved within it. In addition to the usual body wastes, drugs and hormones can also be found in the urine. Therefore, a urine test can detect the presence of illicit drugs or increased levels of hormones. There is very little protein to be found in healthy urine, but in severe kidney disease it may be present in vast quantities. Both the total protein and the albumin (the most common protein in the plasma) levels may be assessed from a urine sample. A 24-hour collection of urine may be used to quantify accurately the protein loss in kidney disease, and can also be used to assess the rate at which blood is filtered by the kidneys (glomerular filtration rate).
A serum sample of blood can be analyzed to reveal the disturbances in blood chemicals that result from kidney failure. In particular, the by-products of protein metabolism (urea and creatinine) may be increased in quantity. In severe kidney disease there may also be disturbances of the concentration of the basic mineral salts, such as sodium, calcium and potassium, in the blood. The level of creatinine may be inserted into a mathematical formula that incorporates the age, ethnicity and sex of the patient to generate an estimate of the amount of fluid filtered by the kidneys in a fixed amount of time. This is the estimated glomerular filtration rate (eGFR), which is a useful indication of the progression of chronic kidney disease (CKD), a condition that becomes increasingly prevalent with aging.
Other factors that indicate a specific cause of kidney disease may also be assayed (e.g. autoantibodies in systemic lupus erythematosus (SLE)). In disease of the prostate gland, a particular protein called prostate-specific antigen (PSA) is assayed, as this is more likely to be raised if cancer is present.
A full blood count (FBC) may reveal the anemia of chronic disease that can accompany chronic kidney disease.
Imaging tests to examine the structure of the urinary system
Ultrasound, magnetic resonance imaging (MRI) and CT scans are used to visualize the shape of the kidneys, ureters and bladder. The images obtained may be used to examine gross defects, such as the presence of cancer or obstruction to the outflow of urine from the bladder, but cannot reveal the more subtle changes that occur in most diseases of the urinary system. An ultrasound scan obtained by means of a probe passed into the anus may also be used to examine the prostate gland.
A plain X-ray image, although it cannot show any detail about the soft tissues, may be used to reveal the presence of kidney stones, also known as calculi. Figure 4.3b-I shows the X-ray images of the passage over time of a calculus down the left ureter.
Figure 4.3b-I X-ray images of calculi (ureteric stones) at different levels of the left ureter
A catheter (a plastic tube) may be passed into the bladder via the urethra to inject a dye that is opaque to X-rays into the bladder. This test, known as cystography or urography, can show up defects in the structure of the bladder.
Imaging tests to examine the function of the urinary system
Until recently, the most commonly performed of the imaging tests of function would involve the intravenous injection of a solution that contained iodine. This solution, when concentrated, shows up on X-ray images. After injection, serial X-ray images can be taken of the abdomen. The whole procedure, known as an intravenous urogram (IVU) or excretion urogram, reveals the passage of the dye through the urinary system, from when it is first concentrated from the blood by the kidneys and then drained into the bladder. This test can reveal abnormalities in the structure of the kidneys and ureters, as well as in their function of filtering the blood. An excretion urogram is shown in Figure 4.3b-II. An increasingly popular and more accurate form of the IVU is the CT urogram in which the CT scanner is used to locate the obstruction in the urinary system instead of a series of X-ray films.
The function of the bladder may be visualized by requesting the patient to urinate after dye has been inserted into the bladder for cystography. An X-ray image taken during contraction of the bladder will reveal any abnormalities in the way in which it empties. This test is known as micturating cystourethrography (MCU).
A radioactive chemical (containing a radioactive isotope) known as DMSA can be used to assess the filtration function of the kidneys more accurately than the IVU. As in the IVU, DMSA is injected intravenously, and is filtered and concentrated in the kidney. The amount of radioactivity that builds up in the kidneys over the next few hours is then assessed by means of a gamma scanner. The radioactivity dies off very quickly, and so this test is not considered to be harmful to the patient.
Figure 4.3b-II Excretion urogram showing a pale patch of contrast in the calyx of the left kidney
The pale patch represents a large calculus (kidney stone).
In cystoscopy, a fiber-optic telescope is inserted into the urethra so that the inside of the bladder can be seen directly. The patient is usually heavily sedated, or has a general anesthetic. Biopsies of the bladder can also be taken by means of the cystoscope.
Under guidance from an ultrasound scan, a needle may be directed through the skin into the kidney to remove a small sample of tissue for examination. This procedure carries a small but significant risk of bleeding into or around the kidney.
Urodynamics is the study of the pressure of the urine in the bladder and the flow of the stream of the urine from the urethra. Specialized tests to measure the pressure within the bladder and the flow rate are used mostly to investigate the underlying problem in cases of incontinence or obstructed flow of urine. Urodynamic studies may be used in combination with MCU.
4.3c Diseases of the kidneys
The conditions studied in this section are:
Part I: Disease processes that affect the kidney:
•glomerulonephritis – nephritic syndrome and nephrotic syndrome
•acute and chronic pyelonephritis
•kidney and ureteric stones
•polycystic kidney disease
•hemolytic uremic syndrome
•hypertension and the kidneys
•diabetes and the kidneys
•cancer of the kidney
Part II: Serious consequences of disease of the kidney:
•acute kidney injury (AKI)
•chronic kidney disease (CKD).
All the common diseases of the kidney described in this section may be so severe as to lead to either sudden (acute) or gradual (chronic) failure of the kidney to perform its necessary functions.
Part I: Disease processes that affect the kidney
Glomerulonephritis is a term used to describe a broad range of conditions that affect the structure of the cup-like origin of the tubules in the kidney and the cluster of blood vessels within this cup known as the glomerulus. In glomerulonephritis the filtering process is impaired. This has the consequence that red blood cells and protein may leak out of the blood into the urine, and also that excess salts, wastes and water may be retained in the circulation.
In medical textbooks, the condition of glomeru-lonephritis may be categorized according to the precise pathological changes occurring in the glomerulus, and these categories are assigned descriptive terms such as minimal change, membranous glomerulonephritis and mesangiocapillary glomerulonephritis. This categorization, which is based on the results of kidney biopsy and is important for predicting prognosis, does not relate directly to the condition that may have caused the disease process. For this reason it is not described further in this section.
Glomerulonephritis can result from a variety of underlying disease processes, but also commonly develops without any obvious cause. In many cases the problem results from the deposition of autoantibodies within the glomerulus. Autoantibodies stimulate the immune response, and the inflammation that results leads to glomerular damage. Autoantibodies may develop as a delayed response to infection, as part of an established autoimmune disease such as systemic lupus erythematosus (SLE) or as a reaction to certain drugs. They may also account for many of the cases of glomerulonephritis of unknown cause.
The Streptococcus bacterium, which is a common cause of sore throat and tonsillitis, used to be a very common cause of antibody-related glomerulonephritis. Post-streptococcal glomerulonephritis tends to lead to a characteristic cluster of symptoms known as nephritic syndrome or acute nephritis (see below). Bright’s disease is an old-fashioned name for nephritic syndrome. This term used to be almost synonymous with post-streptococcal kidney disease.
Other infectious agents that may cause the development of damaging autoantibodies include viruses, such as measles and hepatitis, bacteria, such as Salmonella, and parasites, such as malaria.
Glomerulonephritis may also be part of the disease process of a multisystem autoimmune disease. SLE is the most common specific autoimmune disease known to cause glomerulonephritis. In SLE, chronic kidney disease (CKD) resulting from severe persistent cases of glomerulonephritis is the most common cause of death.
Some drugs may also trigger the development of damaging autoantibodies. The drug that most commonly has this effect is penicillamine, which is prescribed as a disease-modifying treatment in rheumatoid arthritis.
THE CONSEQUENCES OF GLOMERULAR DAMAGE
The effects of glomerulonephritis can be broadly divided into four categories, although in practice, for any individual patient, it may be difficult to assign them to a category. The categories are:
•hematuria (blood in the urine)
•proteinuria (protein in the urine)
•nephritic syndrome (blood and protein in the urine, with high blood pressure and edema)
•nephrotic syndrome (excessive protein in the urine leading to severe edema).
HEMATURIA AND PROTEINURIA IN GLOMERULONEPHRITIS
Some forms of glomerulonephritis cause sufficient damage to the glomerulus to bring about a leakage of red blood cells, protein or both. This leakage may not be sufficiently severe to be visible to the patient, and instead may be picked up on routine urine testing. Greater numbers of red blood cells might cause the urine to appear pink or smoky colored, and excess protein might cause the urine to appear frothy. There may be no other symptoms.
Nevertheless, despite the mildness of the symptoms, the finding of even small amounts of blood or protein in the urine in the absence of urinary infection can be a warning sign of a progressive disease of the kidney. CKD can be the long-term consequence of glomerulonephritis that may be signaled by hematuria or proteinuria. For this reason, all patients who are found to have unexplained hematuria or proteinuria above a certain level will be referred to a renal physician for further investigations.
Some forms of glomerulonephritis that cause hematuria or proteinuria may respond to treatment with immunosuppressant drugs, including corticosteroids. Other immunosuppressant medications that may be prescribed at the same time include azathioprine, cyclophosphamide and chlorambucil. All these drugs can have a wide range of toxic effects.
Information box 4.3c-I
Glomerulonephritis: comments from a Chinese medicine perspective
In Chinese medicine, the underlying pathological process of damage to the structure of the kidney in post-streptococcal glomerulonephritis (leading to acute nephritis) suggests that Internal Heat (which may have had External origins if following an infection) is impairing the normal function of Lung/Spleen and Kidneys to transform and move water. Blood in the urine can be a result of transmission of Heart Fire via the Small Intestine or Damp Heat in the Bladder. Protein in the urine may be interpreted as the draining of Essence from the Kidneys.
In other forms of glomerulonephritis Heat Toxins are not part of the picture and instead Wind, Qi Stagnation, Blood Stasis or Damp lead to the impairment of the normal handling of body fluids by the three key organs. Kidney disease is more likely if there is pre-existing Lung, Kidney and Spleen Deficiency. Blood Stasis is more likely in elderly people. Flaws and Sionneau (2010) state that the most common form of chronic glomerulonephritis is said to be “Spleen-Kidney Yin and Yang Vacuity with Blood Stasis.”44
The predominant energetic effect of immunosuppressant drugs such as azathioprine and cyclophosphamide is that of Heat and they may cause severe damage to Blood and Yin.
Nephritic syndrome is a term used to describe a glomerulonephritis that causes severe symptoms to appear rapidly. In nephritic syndrome the patient, commonly a child, becomes unwell with fever, vomiting and pain in the back. There may be a history of a streptococcal infection within the past two to four weeks, although streptococcal infection is not always the cause. The face becomes puffy with edema and blood pressure is raised. The urine may be pink or smoky colored by red blood cells. In severe cases the production of urine becomes severely reduced as the filtration function of the kidney is extremely impaired. The patient is then at risk of death from acute kidney failure or malignant hypertension.
A patient with nephritic syndrome requires close medical observation. In most childhood cases there is full recovery from the condition after four to seven days, although a minority of cases take a more chronic course. In contrast to the forms of glomerulonephritis that cause hematuria and proteinuria alone, most of these chronic cases of nephritic syndrome do not respond to immunosuppressant drugs. In post-streptococcal nephritis a course of penicillin is given to ensure eradication of the Streptococcus.
Information box 4.3c-II
Nephritic syndrome: comments from a Chinese medicine perspective
In Chinese medicine, some of the symptoms of nephritic syndrome would appear to result from Full Heat. This may originate from a Wind Heat Invasion in the case of post-streptococcal disease. Heat in the Heart is transmitted via the Small Intestine to the Bladder, causing scanty urination and hematuria. Heat obstructing the Orifices of the Heart may lead to the confusion and coma that result from acute renal failure.
Hypertension in nephritic syndrome can lead to convulsions. In Chinese medicine terms these are most likely to result from Heat causing damage to Kidney Yin. Liver Yin is then not nourished, and this leads to Hyperactivity of Liver Yang, which rises and stirs up Liver Wind.
A sudden development of facial edema would be described as Invasion of Wind Water. Proteinuria is a manifestation of Essence draining from the Kidneys.
In acute cases, as the tissue of the kidneys recovers, the toxins and excess salts that have built up in the body are cleared by means of profuse urination. However, in rare cases, the patient may die during the acute illness from acute renal failure and from damage caused to the brain by a rapidly rising blood pressure. Convulsions may develop in these severe cases. This consequence can be prevented with the help of emergency dialysis, which takes over the function of the failing kidney (see later).
In the more chronic cases, and more commonly in adults, there may be persisting damage to the kidneys. This damage can progress to chronic kidney failure over the course of months to years.
Other forms of glomerulonephritis cause the filter of the kidney to leak large amounts of protein. This protein is lost into the urine, which becomes frothy as a result. The main plasma protein to be lost is albumin, but other proteins, including immunoglobulin (the protein that forms the plasma antibodies), are also lost. Nephrotic syndrome describes those cases when excessive amounts of protein are lost into the urine. As albumin is the most abundant plasma protein, this is found in high concentrations in the urine.
Other causes of nephrotic syndrome include the kidney damage that develops in some cases of diabetes, rare drug reactions and allergic reactions.
It is important for the plasma to be maintained at a certain concentration to give it sufficient osmotic pressure to remain in the circulation. The protein albumin plays a vital role in giving the plasma this adequate level of concentration. If albumin is lost, the plasma becomes too dilute, and the plasma fluid tends to move by osmosis into the more concentrated tissue fluid. Excessive fluid collecting in the tissues is called edema. In nephrotic syndrome, the severity of the proteinuria results in severe edema. The patient develops very swollen ankles and legs, and eventually fluid collects in a wide range of body regions, including the abdomen, within the lungs, the facial tissues and the genitalia.
In nephrotic syndrome, changes in the constitution of the plasma mean that clotting becomes a problem, and there is an increased risk of venous thrombosis. Loss of antibodies means that the patient with nephrotic syndrome is more prone to infection. Hyperlipidemia can also develop.
The patient with nephrotic syndrome is treated by means of diuretic medication to encourage loss of the excess tissue fluid, and restriction of salt in the diet. ACE inhibitor medication is prescribed, as this tends to reduce proteinuria, partly by reducing blood pressure. Anticoagulant medication may be given by injection to prevent blood clots. Statins may be prescribed to reduce the hyperlipidemia. Some cases will respond to corticosteroid medication or to other immunosuppressant drugs; this is particularly true in many of the cases that start in childhood.
In children, the underlying glomerulonephritis will very often (in 95 percent of cases) disappear after a few weeks of treatment with corticosteroids. In many of these cases the remission is permanent, and the kidneys return to a healthy state. In most adults, and the remaining childhood cases, a more chronic course develops, in which the proteinuria has to be controlled by ongoing immunosuppressant medication. In some cases the damage to the kidney progresses and CKD results.
Information box 4.3c-III
Nephrotic syndrome: comments from a Chinese medicine perspective
In Chinese medicine, the excessive edema and proteinuria of nephrotic syndrome is associated with a chronic Deficiency of the Lungs, Spleen and Kidneys. The accumulation of edema corresponds to Damp or Damp Heat.
Proteinuria is seen as the draining of Essence from the Kidneys. The Deficiency of Original Qi of the Kidneys that results gives rise to Stagnation of Blood, as Original Qi is necessary to enable smooth movement of Blood in the vessels. This is reflected in the increased risk of thrombosis in nephrotic syndrome.