Health issues linked to the kidney

Sometimes the kidney stops working properly, and may even stop working altogether If this happens, excess water and waste products like urea and salts are no longer removed from the body Left untreated, kidney failure quickly results in death! Common causes of kidney failure are – hypertension (high blood pressure) – sugar diabetes and – infection There are two main treatments for kidney failure: – renal dialysis and – kidney transplant

Renal dialysis During renal dialysis waste, excess salts and water pass from blood into dialysis fluid across a semi-permeable dialysis membrane The dialysis fluid contains concentration of solutes that are usually found in blood: – sugars, salts, etc. – any substance that is in excess can diffuse from the blood into the fluid – any substance that is in short supply can diffuse from the fluid into the blood Blood cells and plasma proteins do not pass through the membrane because of their size

Haemodialysis Blood is taken from an artery to a dialysis (kidney) machine  contains a dialysis membrane to separate the blood from the dialysis fluid  dialysis fluid contains the correct concentration of sugars and salts for normal blood  heparin is added to the blood to prevent it from clotting in the machine  in-line bubble trap is present before blood is returned  if a clamp is tightened excess water can be removed from the blood by ultrafiltration Haemodialysis is usually performed for several hours, three times a week in hospital

Bubble trap Blood is removed from an artery (or from a vein that has had an arterial shunt inserted). Pump and pressure monitor Blood is returned to the vein. Clamp: pressure can be applied to increase the removal of water from the blood. Dialysis machine: blood is separated from the dialysis fluid by a semi-permeable membrane. Heparin is added to prevent blood from clotting in dialyser or tubes.

Dialysis fluid is of contains the correct concentration of sugars, salts and wastes that should be present in blood. Dialysis fluid enters against the flow of blood. Blood enters against the flow of dialysis fluid. Excess substances diffuse from the blood into dialysis fluid. Shortage substances diffuse from the fluid into the blood.

Added convenience: Peritoneal dialysis Peritoneal dialysis uses the peritoneum or abdominal membrane for dialysis A permanent tube is inserted into the abdomen – used to fill the space between the abdominal wall and organs with dialysis fluid – after a few hours the spent fluid is drained and replaced several times Dialysis is on a daily basis and can be completed at home or at work

Note: a functioning kidney helps regulate the composition of body fluids by a number of negative feedback mechanisms  not possible with renal dialysis  control is rather crude In addition, the kidney performs a number of functions in addition to excretion, e.g.  it produces the hormone erythropoietin which controls red blood cell production  hence, dialysis patients are often anaemic

Kidney transplant Although involving major surgery, kidney transplants are routine and relatively straightforward The donated kidney (either living or cadaver donation) is implanted in the lower abdomen and attached to – the blood supply the stub of the renal artery to the common iliac artery the stub of the renal vein to the common iliac vein – the bladder

bladder Kidney: stub of renal artery, renal vein and ureter attached as appropriate (to blood vessels or bladder) common iliac artery common iliac vein aortavena cava

The main problem with any organ transplant is rejection T lymphocytes invade the organ and destroy it Rejection can be minimised by 1.tissue matching the donor and recipient closely and/or by 2.using immunosuppressant or anti-rejection drugs Unfortunately the immunosuppressant drug is required for life and increases the chance of infection

TASK: In small groups, discuss the issues around treatment of kidney failure and produce a summary to outline the main points. Things you may like to consider: – the nature of kidney failure (acute or chronic and recovery prospects – if acute quite likely to make a full recovery) – advantages/disadvantages of dialysis – advantages/disadvantages of transplantation – cadaver v. live donor transplant – availability of kidneys – waiting for someone to die, organ trade – alternatives to human kidney, e.g. xenotransplantation (i.e. from another animal such as a pig)