Do you know someone who has had a kidney stone? If so, they probably told you how painful it was to “pass” the stone. Kidney stones are not uncommon. About 10% of Americans will develop a kidney stone sometime during their lives.
What are kidney stones, and how do the form?
During the formation of urine, sometimes certain salts do not stay dissolved in the filtrate-most notably calcium salts and uric acid but instead form crystals called kidney stones. These stones form for a variety of reasons, including too little water intake or use of certain medications.
Kidney stone attacks are excruciatingly painful. The stone which may be quite jagged, moves through the kidney and then blocks the flow of urine.
Since 1984, a treatment for kidney stones called shock-wave lithotripsy has been available. In this procedure, the patient is immersed up to the neck in a tank of water. Guided by X-ray monitors, intense sounds waves are directed at the stone, shattering it. Lithotripsy is a Greek word meaning “stone crushing”. Once the stone is broken apart, the pieces are excreted in the urine. Surgery is still used to remove stones larger than 2 centimeters in diameter or stones that are causing infection.
A reduction in the filtration rate in the glomerulus leads to renal failure
Renal failure is a condition in which the kidneys stop working properly or at all. It occurs when the filtration of the blood at the glomeruli either slows or stops.
In acute renal failure, filtration stops suddenly. Acute renal failure can have many causes such as decreased blood flow through the kidneys as a result of heart problems or blockage of a blood vessel, damage to the kidney by disease, the presence of a kidney stone blocking urine flow, or severe dehydration as occurs occasionally in marathoners and other endurance athletes.
In chronic renal failure, the filtration of the blood at the glomeruli slows gradually. This condition is usually irreversible because it is most commonly caused by injury to the glomeruli. These injuries have many causes such as the deposit of toxins, bacterial cell walls, or molecules produced by the immune system within the glomeruli; the coagulation of the blood within the glomeruli or the presence of a disease such as diabetes mellitus.
If the kidneys become unable to excrete nitrogenous wastes, regulate the pH of the blood or regulate the ion concentration of the blood, the individual will die unless the blood is filtered in another manner. A machine called an artificial kidney accomplishes this job. The process of filtering blood to replace the normal function of the kidney is call dialysis.
During hemodialysis, a patient’s blood is pumped through tubes to one side of a selectively permeable membrane. On the other side of the membrane is a fluid called the dialysate, which contains the same concentration of ions as is normally found in the bloodstream. Because small molecules can pass across the membrane, any extra ions in the patient’s blood move by diffusion into the dialysate until their concentrations on both side on the membrane is equal. In addition, the dialysate contains no wastes and is changed frequently, so the wastes in the patient’s blood also diffuse into the dialysate. Hemodialysis is a slow process, usually taking four hours, three times a week. The results of research studies show that some patients with kidney failure can undergo hemodialysis successfully at home, while they sleep.
Another type of dialysis is periotoneal dialysis. This process uses the thin lining of the abdominal cavity, the peritoneum, as the dialyzing membrane. The patient has a thin tube called a catheter implanted in the abdominal wall. The dialysate flows into the abdomen through the catheter from a bag outside the body. Waste materials and excess water pass from blood vessels in the peritoneum into the dialysate. After severel hours, the dialysate is drained from the abdomen.
Only 10% of persons with kidney failure survive for at least 10 years on dialysis due to the stress that toxic waste products place on the body organs. Many more persons with kidney failure survive for at least 10 years with a kidney transplant. 56% with a transplant from a deceased donor and 76% with a transplant from a living donor. Each year in the United States, over 13,000 patients with renal failure receive kidney transplants. It is the second most common transplant operation in the country, with corneal transplants being the first.
Source : Biology – Understanding Life (Alters & Alters)