Sunday, June 24, 2007

Week 1: Kidney Transplant

In this blog I will attempt to give a preview of the kidney function, its failure, and then how the transplant is carried out.. By the way, did you know that the defective native kidneys in a patient aren't taken out? Rather, the patient is grafted with another kidney to bring the number = 3 kidneys..Keep reading on!


What do Kidneys do?
In a nutshell, a kidney is responsible for maintaining physiological homeostasis that is required for the proper functioning of the body. It involves the regulation of the body's fluid volume, mineral composition and acidity by excretion and reabsorption of water and inorganic electrolytes. Kidneys also are vital in ions regulation such as sodium, potassium, chloride, calcium, magnesium, sulfate, phosphate and hydrogen, all of which are required in certain concentrations for the normal functioning of the body. A well known kidney function is the excretion of metabolic waste such as urea and other organic osmolytes. Another important function of the kidney besides waste removal is the release of 3 vital hormones namely: erythropoietin(for red blood cell production), renin( for blood pressure regulation), and calcitriol( active form of vitamin D for calcification in bones).

Where do all these things take place?

Everyday, the kidneys filter about 800 liters of blood through its tiny units called nephrons and later reabsorbs ~ 99.9% of it leaving 2 liters of urine. There are about 1 million of these nephrons in each kidney, each of which is endowed with a glomerulus(filtration site) and reabsorption/secretion tubules. The great abundance of these nephrons is advantageous in that a person may have a large number > 50% of them dead and still maintain normal kidney function. Thats is one reason why a kidney donor can still lead a normal life with only one kidney functioning. A kidney transplant is needed when there a renal failure, where the 2 kidneys can no longer maintain the required homeostasis by removing waste products, etc.

Why do Kidneys fail?
Most kidney diseases attack the nephrons, causing them to lose their filtering capacity. The most common causes of kidney disease are diabetes and high blood pressure. Diabetes (high blood glucose) damage and obstruct the reabsoption mechanism of the nephrons leading to Diabetic nephropathy. High blood pressure also damage blood vessels in the nephrons to cause renal failure. Other causes of renal failure include: glomerular diseases, congenital kidney diseases, poison, and trauma. ohh yea, I will finally delve into the more interesting transplant section.

Transplant of Kidney...
A lucky patient who has been praying and patiently waiting for a donor finally has his/her wish answered. He/she has to face the scapel! There are over 100,oo0 people awaiting for kidney transplants in the U.S.; and the current wait time is ~ 7 years. The only requirement is that receipient's blood type matches the donor's blood, i .e., O type gets O. Due to better targeted immunosuppresion, the blood antigen do not have to match. For instance, O- blood type donor can donate to O+ receipient and vice versa. Also other previously important prerequisite are no longer necessary....Thanks to the great strides in immunology!

Once the patient has been matched and neccesary paperwork has been done, its time to face the scapel. The incision is made either on the right or left pelvic starting right above the bladder. The surgeon's intention is to graft the new kidney without tampering with the failed ones by attaching the renal artery and vein of the graft to the corresponding renal artery and vein (upstream) of the native kidneys and then suturing the ureter(graft) to the bladder. I haven't found the answer as to why the failed kidneys are left intact. So once the new kidney is sutured in place, the surgeon makes room for it around the pelvic cavity by sh0veling intestines, etc away... The patient now has 3 kidneys, 2 of which are failed.. The operation takes ~ 4 hours and the patient would typically stay for 2 days in the hospital for observation. It takes about 2 - 3 months or even sooner for complete renal function recovery.. Just this 1st week, I saw a kidney transplant from a 3 year cadaveric( non-living) donor, a kidney transplant from a 56 yr-old living twin brother donor to his HIV-positive brother.., and a kidney/pancreas transplant. It is so astounding how knowledgeable surgeons are as every case is completely different from others. Some cases require the administration of 3 combinations of immunosuppresants to avoid organ rejection, while some require minimal immunosuppresant use.
For kidneys, obtaining a kidney from a baby is much better and than a kidney from an older person whose nephrons are over 50% dead. Dr. Goldstein has performed a trasplant from a 17-month old donor. In theory he says, it can be from as young as 7-month old or Apparently it grows very fast and in 3 months reaches the size of an adult kidney(fist size).

Doing Rounds...Patient Checkups..
For the 2 hospital stays, the surgeon and the medical staff(residents and med. students) would go on morning checkups to ensure that the patients are recovering well. To monitor how well the transplanted kidney is working, the amount of urine is measured..Usually it would take several hours after transplant before the kidney starts making urine.. For the most part, a kidney from a younger person regains its function faster.. Because the how hard the heart beats is intimately related to how the kidney works, the blood pressure is also monitored to ensure that the patient is normotensive. Also during this period, blood osmolytes such as albumin (responsible for oncotic blood pressure) are monitored and administered if needed. The patient is also slowly weaned off pain medication and liquid food.. If all is well in 2-3 days, the patient is released and reports for checkup in 3 months..

I have another entry on pancreas transplant but this blog is getting too long..I shall save it for a later date..

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