Renal replacement therapy replaces all except -
Endocrine function
Urine output
Blood biochemistry
Ultrafiltration
Renal replacement therapy does not replace the endocrine and metabolic functions of the kidney . It maintains plasma biochemistry (uraemic toxins, electrolytes acid base) It also removes fluid from the circulation (ultrafiltration) to maintain the plasma volume. Ref Harrison20th edition pg 290
Kidney