The kidneys play a crucial role in maintaining the body's water, electrolyte and acid-base balance. They filter out toxins and the end products of metabolism. They secrete hormones that affect the blood pressure and production of blood cells. One healthy kidney can perform all these functions on its own, but damage to both kidneys will cause a wide range of symptoms affecting all of the body's systems.
Water Balance and Edema
In kidney failure, water output is usually decreased, leading to edema. As explained in "Harrison's Principles of Internal Medicine," edema usually starts with swelling of the ankles; swelling around the eyes may appear. Edema can progress to a point where the entire body is swollen, a condition known as anasarca. Protein loss through malfunctioning kidneys can contribute to edema.
Certain types of kidney disease lead to polyuria, or excessive urination. Urine is not properly concentrated and the body loses too much water. The patient compensates for excessive water loss by drinking excessive amounts of water. Nighttime urination caused by kidney disease is characterized by urinating at standard intervals, such as every two hours, unlike excessive urination from other causes, which occurs at random intervals.
Acidosis and Hyperkalemia
The blood's PH, or acidity level, is maintained within a very narrow range. Kidney disease can cause acidosis, meaning increased acidity of the blood. According to the Merck Manuals Online Medical Library, symptoms include nausea, vomiting and fatigue. Breathing is typically rapid and deep. Left untreated, coma and death may follow.
Renal failure can lead to hyperkalemia, or high blood levels of potassium. Hyperkalemia often has no symptoms that the patient can feel, but it can cause fatal disturbances in the heart rhythm. Acidosis contributes to hyperkalemia.
Effects on the Brain
Kidney failure can lead to uremic encephalopathy, which is thought to be caused by accumulation of toxins in the blood. The first symptoms can be confusion and memory loss. Seizures may appear. The patient may become progressively more lethargic till he lapses into a coma. Death will eventually ensue.
Anemia
Erythropoietin, a hormone secreted by the kidneys, stimulates production of red blood cells. According to the National Kidney Disease Clearinghouse, even mild kidney damage reduces secretion of erythropoietin; anemia can appear early in the course of kidney failure. Symptoms of anemia include fatigue; inability to carry on normal physical activities; depression; and increased cardiac symptoms in patients with heart disease.
High Blood Pressure
High blood pressure often has no known cause. Of all the known causes of hypertension, renal disease is the most common, as explained in "Harrison's Principles of Internal Medicine." Hypertension in turn can damage the kidneys, as well as contribute to heart disease and stroke. Renal disease can cause malignant hypertension, which means a rapid rise of blood pressure to very high levels. Symptoms include blurry vision, headache, confusion and chest pain. Malignant hypertension requires treatment in the emergency room.
References
- "Harrison's Principles of Internal Medicine, 17th edition"; Anthony Fauci, et al. (eds.); 2008
- National Kidney and Urologic Diseases Clearinghouse: Glomerular Diseases
- Merck Manuals Online Medical Library: Acidosis
- National Kidney and Urologic Disease Clearinghouse: Anemia
