Hello, Creatinine and urea  increase as the ability of the kidneys to filter fluid within the body declines. This is irrespective of the cause of reduced efficiency of the kidneys. The most  common reasons for developing raised creatinine levels are when the filtration mechanism becomes gradually damaged by long-term raised blood pressure or diabetes. Since your father is showing consistent rise in serum creatinine levels after the surgery,it means that functions of kidney are deterioring and so he should be investigated thoroughly for finding the cause. Consult a nephrologist as early as possible. Thanks