Meenakshi Sambharia, MBBS

For hemodialysis (the more common form of dialysis), a patient will visit a hospital or clinic and be connected to a dialysis machine by a needle attached to a tube that draws blood from the arm. The drawn blood is transferred to the dialysis machine, where it is filtered and separated until clean. Waste products from the blood pass into a fluid called dialysate, which is pumped out of the machine into a waste receptacle. The machine also measures and helps ensure the blood has the appropriate level of fluid, electrolytes, and pH. A tube delivers the cleaned blood back into the patient's body. A dialysis session like this will typically last for three to four hours, with a patient undergoing dialysis around three times per week.

A second method of dialysis is known as peritoneal dialysis. Unlike hemodialysis, peritoneal dialysis can be performed at home by oneself after an initial surgery. To start, a physician (generally a surgeon) will make a small incision in the lower abdomen and insert and surgically attach a catheter (thin tube). At home, the patient connects a pump to the abdomen catheter, delivering dialysate (dialysis fluid) from a bag hanging on a wheeled stand. This fluid enters the peritoneal cavity (greater abdomen area containing the stomach, liver, and intestines) and collects waste through osmosis, where waste in the blood moves across a membrane and into the dialysate. This process continues for several hours until the fluid concentration is equal between the blood and dialysate, at which point the fluid can be drained. The fluid can then be passed through a machine called a cycler, which removes waste and allows for the dialysate to be reused. This process is repeated about four times per day. Dialysis patients must limit the amount of fluid they consume prior to receiving dialysis and should also avoid eating salty foods. The cycler cannot filter more than a certain amount of waste products from the blood.

Kidneys are important organs, and dialysis treatments are vital for those with renal dysfunction. For many, dialysis is not so much a medical procedure but a part of their normal life.

Kidney stones can be smooth or jagged and are yellow to brown in color. They are mostly comprised of the minerals calcium, oxalate, and phosphorus. Examining the stones to see what they are made of can show what caused the stone to be formed in the first place. For example, a stone made of mostly calcium, which is the most common type, can happen any time the urine becomes too concentrated due to dehydration or a blockage in the kidney. A uric acid stone forms when acid levels in the urine get too high, usually due to excessive consumption of animal protein such as meat and fish. A struvite stone is a sign of certain infections, and a cystine stone can be due to a genetic disorder that raises the risk of kidney stones.

The most common symptom of kidney stones is pain, either in the back or lower abdomen, or severe pain when urinating. There may also be blood in the urine. Treatment for kidney stones depends on how large the stone is. Very small stones can pass out of the body on their own, and they do not require treatment other than drinking adequate water and taking pain killers. Larger stones need to be broken apart and removed. The main treatment options are:

• Shock wave lithotripsy, which uses sound wave vibrations to break apart the stone
• Percutaneous nephrolithotomy, or the use of a very tiny tool (like a wire inserted through the back) to break apart and remove the stone
• Ureteroscopy, a thin tube inserted through the urethra and bladder to the stone, where tiny tools can grasp the stone and remove

People who have had one kidney stone are at risk of developing another. To reduce this risk, patients are given instructions specific to the type of stone they developed. Generally the instructions will include drinking more water to dilute the urine, but it may also involve lowering sodium intake or eating less meat.