What diagnostic indicator suggests a patient is experiencing rejection of a transplanted kidney?

An elevated serum creatinine level is a key diagnostic indicator suggesting that a patient may be experiencing rejection of a transplanted kidney. This elevation typically occurs because the kidneys are not functioning effectively due to immune response against the transplanted organ. When the kidney is rejecting, its ability to filter waste products, such as creatinine, diminishes, leading to an increase in its serum levels. Monitoring serum creatinine values is critical following a kidney transplant, as timely recognition of increased levels can allow for interventions to address possible rejection.

While elevated serum BUN (blood urea nitrogen) may also indicate kidney dysfunction, it is less specific to the rejection process compared to creatinine levels. A low hemoglobin level could suggest issues such as anemia, which is not a direct indicator of rejection. Similarly, low vitamin D levels might be present due to various factors but are not specific to kidney transplant rejection. Thus, elevated serum creatinine is consistently recognized as a primary sign of possible rejection in the context of renal transplantation.