Normal Urine Output in Hemodialysis

Kidneys are important organs responsible for filtering blood and producing urine. By urinating, the kidneys can discharge the metabolic wastes and excess water from blood. Therefore, the urine output is an important index in reflecting of the renal function.

The amount of urine output in hemodialysis is equable to fluid that does not need to be removed by the dialysis machine. Although the remaining GFR may only be 4 to 5 Ml/ min in patients begun on maintenance hemodialysis, this is sufficient to make a significant contribution to the removal of the potential uremic toxins since filtration is continuous. Moreover, the urine output also helps regulate the fluid and electrolyte balance and may enhance nutritional status and survivals.

However, with extended period of hemodialysis, their urine output will decrease gradually and finally evolve into anuria. The decreasing urine output in hemodialysis is related to the flowing factors.

1. Once the patients start dialysis, a part of metabolic wastes like blood urea nitrogen (BUN) and creatinine are filtered out of fluid. The concentration of BUN and creatinine in blood are lower than before so osmotic diuresis may decline.

2. The patients with End Stage Renal Failure need to remove the excess water and sodium from body by hemodialysis. If ultrafiltration occurs, it can cause the effective blood volume to decline rapidly, which is followed by declining in urine output.

3. Hemodialysis can only clear up the metabolic wastes, but do not have secretion or regulation functions at all. With the dialysis going on, the patients’ renal function is still keeping on aggravation.

For patients on hemodialysis, the residual renal function is closely linked their urine output. Most of the patients may still have much and even normal urine output when they just start dialysis. The experts point that they should keep this condition to create favorable environment for improving the survival rate of the patients.

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