Chronic kidney disease (CKD) is the gradual and permanent loss of kidney function over time, usually over months to years. The most common causes of chronic kidney failure are diabetes mellitus and high blood pressure, which directly damage the kidneys' small blood vessels and diminish the kidneys' ability to filter metabolic waste from the blood.
There are approximately 4.5 million noninstitutionalized adults in the United States diagnosed with kidney disease, according to the 2009 National Health Interview Survey. Overall, kidney disease (which includes nephritis, nephrotic syndrome and nephrosis) is the ninth most common cause of death in the United States, behind influenza, Alzheimer and diabetes mellitus.
Signs & Symptoms
CKD is sometimes called a “silent disease.” Patients rarely feel sick during the beginning and there are few noticeable symptoms until the disease has seriously progressed. In fact, the deterioration of kidney function may be so slow and imperceptible that symptoms do not occur until the damaged kidneys function at less than 10 percent of its normal capacity, according to the National Institutes of Health.
Initially, patients may experience general ailments such as headaches, fatigue and itchiness. However, as the disease progresses and the body has more trouble filtering and getting rid of excess water (a condition known as uremia), patients will also experience the need to urinate more or less often and may have swelling in their hands, legs, ankles or feet, loss of appetite and nausea and muscle cramps. Some patients will also have “fishy” ammonia-smelling breath, according to the NIH.
Diagnosis & Tests
Since many CKD patients also have high blood pressure (the kidney damages may be caused by high blood pressure), blood pressure measurement is an important first step toward a proper diagnosis. Other than that, CKD has very few symptoms during the early stages. Physicians have to rely on laboratory tests, rather than physical examinations, as part of the diagnosis. These tests measure certain protein markers in the blood or urine to confirm the presence of kidney failure.
One such marker is creatinine, a waste product produced by the body when it converts food into energy. The kidneys normally filter creatinine from the blood and remove it from the body through urine. A build-up of creatinine in the blood may mean the kidneys are not working properly, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDKD). In addition, people with kidney problems will also have a higher level of urea in the blood.
The presence of the blood protein albumin in the urine is another indicator of kidney troubles. The condition, known as proteinuria, can be discovered using a color-changing dipstick in a small sample of urine. However, this is a rather crude method and most positive dipstick tests are a result of benign proteinuria, according to the American Academy of Family Physicians. The organization recommended that urine dipstick tests be followed up with 24-hour urine collection for quantitative measurements of protein in the urine.
Another useful indicator of kidney function is the glomerular filtration rate (GFR), which measures how efficiently the kidneys filter waste from the blood. This number is usually extrapolated by measuring the level of creatinine in a blood sample, along with values assigned for age, sex and race. The lower the estimated glomerular filtration rate, the more serious the kidney damage, according to the NIDDKD.
Beyond these lab tests, a kidney ultrasound may be used to identify polycystic kidney disease, cancer, kidney stones or other obstructions, according to the Mayo Clinic. It can also help identify other reversible conditions.
Treatments & Medication
The first step to staunch the disease and prevent any worsening of kidney function is to treat the root cause. Patients with hypertension should take blood pressure medications and adopt a healthy diet and exercise routine. Those with acute infections, such as a urinary tract infection, should be treated with antibiotics or have any obstructions in the urinary tract removed or relieved.
In severe cases and end-stage renal disease, where there's a complete or near-complete failure of the kidneys to excrete waste, concentrate urine and regulate electrolytes, the patient will need to go on dialysis or undergo a kidney transplant, according to the Mayo Clinic.
The rate of decline in kidney function depends somewhat on how well the underlying disorder is controlled. Controlling blood pressure is a key step in delaying further kidney damage, according to the NIH. Some preventive measures include eating a diet that is low in fat and cholesterol, doing regular exercise, not smoking and closely monitoring blood sugar levels.
Patients diagnosed with CKD should adopt a low-protein, low-salt diet and limit fluid intake to maintain a balance of electrolytes, minerals and fluid. Since most dialysis patients urinate very little or not at all, fluid restriction between treatments prevents fluid from building up in the body, which could lead to excess fluid in the heart, lungs, and ankles, according to the NIH.