When kidneys fail, the damage shows up in blood, bones and breath
Kidneys do far more than make urine. They release a hormone that tells bone marrow to build red blood cells, and they balance potassium, phosphate and fluid. So when they drop below 15 percent of normal function, the effects ripple outward into anaemia, cramps, swelling and breathlessness.
Doctors split kidney failure into two broad kinds. Acute failure comes on fast and often reverses; chronic failure creeps up slowly, frequently without early symptoms, and usually does not. In the United States acute failure strikes about 3 in 1,000 people each year, while chronic failure affects about 1 in 1,000. A Canadian estimate put the lifetime risk of end-stage disease at 2.66 percent for men and 1.76 percent for women.
Acute cases usually follow a sudden loss of blood flow to the kidneys or a flood of toxins, from injuries, surgical complications, drug overdoses or even bee stings. One striking example is crush syndrome: when a limb pinned for a long time is suddenly freed, toxins pour into the circulation and can clog and wreck the kidneys. Chronic failure most often stems from diabetes and long-term high blood pressure, with polycystic kidney disease, lupus and some infections such as hantavirus also responsible. Researchers have linked two West African variants of a gene called APOL1 to several forms of non-diabetic kidney failure in people of African ancestry.
The symptoms trace the kidney's jobs. Waste building up in the blood, a state called azotemia, may be silent at first. Falling production of erythropoietin means fewer red blood cells and anaemia. Excess phosphate can drag calcium down and bring muscle cramps, retained potassium causes hyperkalemia, and unremoved fluid swells hands, ankles and face or collects in the lungs. Damaged filters leak protein that healthy ones hold back.
Chronic disease is graded in five stages by glomerular filtration rate, the best overall measure of kidney function; by stage 5 it has sunk below 15 millilitres per minute. At that point treatment means dialysis, either by machine outside the body or with fluid cycled through the abdomen, or a kidney transplant.
Source: Kidney failure
