High blood creatinine, what's going on?

Blood creatinine is high, suggesting the following reasons: First, when the renal prerenal blood perfusion is insufficient, it will cause the renal filtration rate to decrease, leading to the increase of blood creatinine; Second, when the renal retrorenal urinary tract obstruction occurs, creatinine excretion will be abnormal; Third, when the renal function decreases, the filtration rate will decrease and excretion will be abnormal, thus causing the phenomenon of increased blood creatinine.