Nutrition for Kidney Problems
Are you interested in knowing about the bean-shaped organ??? Read further below for a detailed discussion on the kidneys and their associated problems.
Physiology and Functions of the Kidneys
The kidneys are a pair of organs, about the size of a fist, situated below the rib cage on each side of the spine. The primary function of the kidney is to filter the blood several times in a day. This organ also removes waste, controls body’s fluid balance and regulates electrolyte balance. When the kidneys filter blood, they create urine which is collected in the pelvis which is a funnel-shaped structure used to drain down tubes called ureters to the bladder.
Each kidney has about 1 million functioning units called nephrons which are microscopic filters of blood. These nephrons contain tiny filtering units of blood vessels called glomerulus attached to a tubule. It is here that chemicals and water are either added to or removed from this filtered fluid producing urine as the end product excreted out.
A normal kidney filters 136 liters to 170 liters of blood to produce 1.13 liters to 2.26 liters of urine. Kidneys are actively involved in producing vitamin D as well as eliminating calcium and phosphorus.
Renal diseases are due to affected urinary tracts. Discussed below are the most important renal diseases.
Glomerulus is responsible for producing ultrafiltrate and preventing unwanted substances from entering this filtrate. When this function does not happen accurately it results in diseases.
Nephritic syndrome or glomerulonephritis is due to the inflammation of the glomerulus. This inflammation affects the glomerular functioning of filtering blood to produce urine and remove waste. Hence, blood and protein appear in the urine with fluid accumulation in the body. Symptoms include blood in the urine, high BP, decreased urine output, blurred vision and general ill feeling. Treatment for this disease constitutes limiting salt, potassium and fluids intake. But this is of use only if uremia or hyperkalemia develops. Kidney dialysis is yet another optional treatment if medications do not help in curing the disease.
Nephrotic syndrome is a collection of symptoms indicating kidney damage. The main indication is large amounts of protein content in the urine along with increased cholesterol levels, edema and hypoalbuminia. The damaged glomeruli allow 3 grams or more of protein to leak into the urine in a period of 24 hours, which is almost 20-times the normal level passed through healthy glomeruli. Systemic diseases (diabetes mellitus, SLE and amyloidosis) are the root cause for more than 95% of nephrotic syndrome.
Treatment for nephrotic syndrome is primarily diet changes and medication. The first goal is to take steps to reduce high blood pressure, edema, high cholesterol and risk of infections. The diet should also focus on providing enough protein and energy to maintain sufficient nitrogen balance, increase albumin levels and reduce edema. Restricting sodium intake to approximately 3g daily helps to reduce edema.
Diseases of the Tubules and Interstitum
The monstrous energy requirements of the tubule in performing active secretion and resorption make it vulnerable to ischemic diseases. Local concentration of toxic drugs may damage various parts of the tubule.
Acute Renal Failure
Acute renal failure is the rapid loss of ability of the kidney to remove waste and balance electrolytes in the body. This disease develops rapidly over a period of few days or few weeks. Causes can be systemic diseases, crush injury, urinary tract blockage, decreased blood flow, autoimmune kidney disease and more. Primarily patients acquire this disease due to sustained shock caused by severe infection, trauma, surgical accident or cardiogenic shock. ARF due to drug toxicity is curable simply by stopping the drug usage. The mortality rate in patients having ischemic acute tubular necrosis due to shock is almost 70%. Recovery from these, if possible, should occur in 2 to 3 weeks time when the underlying causes have been corrected.
Treatment goal is to make your kidney functional again and prevent waste accumulation in the body. In most cases hospitalization is required. If lack of fluids is found to be the cause of kidney failure, the doctor may recommend IV fluids. When potassium is not filtered properly from the body calcium, potassium or sodium polystyrene sulfonate can be suggested to remove excess potassium. Basically, your diet would be rich in carbohydrates and low in protein, salt and potassium. Toxin buildup in the body may result in dialysis treatment. Dialysis is the process used to artificially perform the function of the kidney temporarily. It helps to remove the excess toxins and potassium from your body. But when kidney damage is irreparable dialysis may be needed permanently for survival.
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Other Tubular or Interstitial Diseases
Chronic interstitial nephritis may occur due to sickle cell disease, diabetes mellitus, analgesic abuse or vesicoureteral reflux. This disease results in the inability to concentrate urine. Fanconi’s syndrome is the inability to resorb the required amount of glucose, amino acids, phosphate and bicarbonate in the proximal tubule, as a result of which these substances are excreted in the urine. Diet modification is the only available treatment for this disease. Replacement therapy includes advocating large volumes of water and dietary supplements of bicarbonate, potassium, phosphate, calcium and vitamin D. Pyelonephritis is a bacterial infection of the kidney which does not require extreme diet modifications. Cranberry and blueberry juices aid in reducing the bacteria present.
Progressive Nature of Renal Disease
Many of the above discussed diseases may or may not result in renal failure. Some patients may have pre-ESRD (end state renal disease) for few months to many years while other patients may find dialysis as their only option for renal failure. But once your kidney is affected by almost 50%-75% kidney functions start deteriorating further.
When glomerular filtration rate (GFR) decreases the kidney automatically tries to prevent this decrease which leads to glomerular pressure in the long run. Dietary protein is a leading factor in increasing glomerular pressure and hence must be restricted. Hypertension, an important factor that leads to progressive loss of renal function, must be kept under control to effectively benefit from protein restriction. Controlled blood glucose level is mandatory in people with diabetes.
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End-Stage Renal Disease
End stage renal disease (ESRD) happens when the kidneys are unable to perform their daily functions any longer. Diabetes, high blood pressure and glomerulonephritis are the most common causes of ESRD. Treatment of ESRD is either by dialysis or transplantation. The patient must have optimal nutrition levels and the nutrition care required after transplantation depends on the metabolic effects of the required immunosuppressive therapy. Adequate amount of calcium and phosphorus with decreased cholesterol content in the diet is recommended. Weight management must be insisted along with proper diet modifications for long life after transplantation.
Dialysis can be done by hemodialysis or PD.
This is an artificial method of purification where unwanted fluids and wastes are removed from the body. For hemodialysis, the patient is connected to a filter by tubes attached to the blood vessel. The blood from the patient is slowly pumped into the dialyzer where unwanted fluids and toxins are removed and the purified blood is again pumped back into the body. This treatment is required thrice a week where each session lasts for about 3 to 5 hours. Patients requiring dialysis daily have treatments lasting between 1.5 and 2.5 hours, whereas some patients undergo nocturnal treatment thrice a week for about 8 hours.
Peritoneal Dialysis (PD) makes use of the semipermeable membrane of the peritoneum which acts as a filter to wash out the extra toxins and fluids from the body. This treatment can be done at home after getting trained at a dialysis center. Two types of PD are common. In the first type, continuous ambulatory PD (CAPD), dialysis is performed 4-5 times daily making it a 24-hour treatment. In the second type, continuous cyclical PD (CCPD), treatment happens during the night as the process takes about 10 to 12 hours. Patients opting for PD can consume sodium, potassium and fluids liberally as the dialysis process happens almost continuously.
Patients with renal failure not only undergo treatment continuously for survival but also their lifestyle and quality of life change drastically to adapt to the disease. People in association with these patients must be tolerant toward their mood change and diet modifications.
Medical Nutrition Therapy
MNT focuses mainly on preventing any deficiency and providing healthy nutrition status. Most patients take self responsibility for their diet. Periodic counseling with an RD is compulsory to motivate these patients and track their food habits.
Most of the patients undergoing dialysis are recommended to reduce sodium intake to prevent increased fluid intake. They are advised to snack on few ice chips, cold sliced fruits or sour candies to deal with thirst without drinking. Surprisingly, in few patients with ESRD sodium is lost from their body. To prevent hypotension, cramps and further decrease in renal function extra sodium is required. Adding salt or eating salty diet elevates sodium level. As this type of patients is rare, a thorough examination of the patient’s history and understanding of his requirements are mandatory. Potassium intake should also be curbed in patients undergoing dialysis depending on their urine output, body size and frequency of hemodialysis. Apart from diet history other sources of potassium must also be scrutinized. Poor dialysis frequency, raised blood sugar in patients with diabetes, blood transfusions, chemotherapy and radiotherapy are few examples of non-dietary sources.
Dialysis results in protein depletion from the body. Hence daily intake should be increased to compensate for this loss. Mortality rate is higher in patients with low albumin levels. Hypoalbuminemia is affiliated to poor nutrition, inflammation and comorbid diseases. Energy intake should be in par with the patient’s nutrition status and degree of stress. Between 25 and 40 kcal/kg of body weight should be provided, with the lower amount for transplantation and PD patients and the higher level for nutrition-deficit patients.
Calcium intake must be on the higher side and phosphorus intake must be on the lower side. This feasibility is pretty difficult as most high-calcium foods are also high in phosphorus. A high-protein diet requirement also increases phosphorus content. Hence the excess phosphorus should be removed with phosphorus-binding medication. Anemia due to chronic renal failure is corrected during dialysis.
Water-soluble vitamins lost during dialysis are compensated with vitamin supplements depending on the patient’s history. Lipids intake must be restricted during dialysis.
Complications may arise anytime during dialysis in the form of postdialysis hypoglycemia, due to abrupt glucose supply cut-off or amino acid losses. Patients may be suggested carbohydrate-enriched snacks toward the end of the treatment to avoid post-treatment rebound hypoglycemia.
ESRD in Patients with Diabetes
Most renal failures are due to diabetes and approximately 40% to 50% of patients undergoing dialysis have diabetes. Hence dietary modifications are compulsory for such patients.
Education of Patients with ESRD
Patients with ESRD liable to follow a strict diet all through their life must be thoroughly educated by an RD regarding their dietary regulations. The RD must take authority to develop a good rapport with the patient and family to help them make excellent nutrition choices for an extended period of time.
Chronic Kidney Disease in Children
Chronic kidney disease (CKD) which may occur in children right from their birth up to adolescence is a rare occurrence. Causes may be congenital, anatomic defects, inherited, metabolic disorders or acquired conditions or illnesses. The main challenge of this disease is to make the child nutritionally balanced without making it a manipulative tool and an attention-getting device. Maintaining energy and protein requirements in these children is similar to the requirements of normal kids. Also calcium and phosphorus levels must be kept under control in children with CKD.
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Nephrolithiasis (Kidney Stones)
Nephrolithiasis is the most prevalent chronic kidney condition after hypertension. Kidney stones are small, hard mineral deposits inside your kidneys which leave the body through the urine stream. Genetics and environmental factors apart from high urine calcium levels, obesity, calcium supplements, inadequate fluid consumption and gout are the main reasons behind kidney stone formation. It is more common in men than women. Various types of kidney stones are discussed below.
Uric acid stones are the only ones that respond to dissolution therapy. Hence prevention is the best solution for this disease. After treatment, diet and nutrition counseling is stressed upon to reduce urinary risk factors and kidney stone recurrence. High urine flow will wash out any stones formed and the desired urine volume to prevent further occurrence of stones is between 2 to 2.5 L/day. This goal is met when 250ml of fluid is consumed at each meal, between meals, at bedtime and when getting up in the night.
Calcium stones are the most common type of kidney stones present in the form of calcium oxalate. Some fruits, vegetables, nuts and chocolates are high in oxalate content. Dietary factors, increased vitamin D levels and metabolic disorders increase calcium and oxalate levels in urine. Restricting calcium levels does not guarantees relief from kidney stones and may inversely cause or worsen osteoporosis. Dietary changes include reduced sodium intake, avoiding animal proteins such as meat, eggs and fish, maintaining enough calcium levels in the body and preventing oxalate-rich foods such as spinach, nuts and wheat bran.
Uric Acid Stones
Uric acid stones are formed due to persistently acidic urine. Also diabetes is associated with uric acid stone formation. A diet rich in purines, substances found in animal proteins, increases uric acid in urine. Purine-rich foods such as organ meats, anchovies, herrings, sardines, meat-based broth and gravy should be avoided. Black currant juice may prevent uric acid stones and hence can be suggested for patients.
Cystine stones are the result of genetic disorders that causes kidneys to excrete too much of certain amino acids (cystinuria). Methionine is the metabolic precursor of cystine. Hence restricting methionine-rich foods such as milk, meat and eggs is considered.
Struvite stones are formed due to kidney infections. These stones are a combination of magnesium ammonium phosphate and carbonate apatite. Surprisingly, these stones are more common in women than men. Treatment for stone removal includes surgery or extracorporeal shockwave lithotripsy with adjunctive culture-specific antimicrobial therapy that uses urease inhibitors. Cranberry juice is recommended to treat urinary tract infection and struvite stones.
Dietary changes and fluid intake are the main factors to avoid kidney stone formation and stone recurrence.