A method for (a) diagnosing or monitoring kidney function in a subject or (b) diagnosing kidney dysfunction in a subject or (c) predicting or monitoring the risk of an adverse event in a diseased subject wherein said adverse event is selected from the group comprising worsening of kidney dysfunction including kidney failure, loss of kidney function and end-stage kidney disease or death due to kidney dysfunction including kidney failure, loss of kidney function and end-stage kidney disease or (d) predicting or monitoring the success of a therapy or intervention comprising • determining the level of Pro-Enkephalin or fragments thereof of at least 5 amino acids in a bodily fluid obtained from said subject; and (a) correlating said level of Pro-Enkephalin or fragments thereof with kidney function in a subject or (b) correlating said level of Pro-Enkephalin or fragments thereof with kidney dysfunction wherein an elevated level above a certain threshold is predictive or diagnostic for kidney dysfunction in said subject or (c) correlating said level of Pro-Enkephalin or fragments thereof with said risk of an adverse event in a diseased subject, wherein an elevated level above a certain threshold is predictive for an enhanced risk of said adverse events or (d) correlating said level of Pro-Enkephalin or fragments thereof with success of a therapy or intervention in a diseased subject, wherein a level below a certain threshold is predictive for a success of therapy or intervention, wherein said therapy or intervention may be renal replacement therapy or may be treatment with hyaluronic acid in patients having received renal replacement or predicting or monitoring the success of therapy or intervention may be prediction or monitoring recovery of renal function in patients with impaired renal function prior to and after renal replacement therapy and/or pharmaceutical interventions, wherein said Pro-Enkephalin or fragment is selected from the group comprising SEQ ID No. 1, SEQ ID No. 2, SEQ ID No. 5, SEQ ID No. 6, SEQ ID No. 8, SEQ ID No. 9, SEQ ID No. 10 and SEQ ID No. 11. • determining the level of Pro-Enkephalin or fragments thereof of at least 5 amino acids in a bodily fluid obtained from said subject; and (a) correlating said level of Pro-Enkephalin or fragments thereof with kidney function in a subject or (b) correlating said level of Pro-Enkephalin or fragments thereof with kidney dysfunction wherein an elevated level above a certain threshold is predictive or diagnostic for kidney dysfunction in said subject or (c) correlating said level of Pro-Enkephalin or fragments thereof with said risk of an adverse event in a diseased subject, wherein an elevated level above a certain threshold is predictive for an enhanced risk of said adverse events or (d) correlating said level of Pro-Enkephalin or fragments thereof with success of a therapy or intervention in a diseased subject, wherein a level below a certain threshold is predictive for a success of therapy or intervention, wherein said therapy or intervention may be renal replacement therapy or may be treatment with hyaluronic acid in patients having received renal replacement or predicting or monitoring the success of therapy or intervention may be prediction or monitoring recovery of renal function in patients with impaired renal function prior to and after renal replacement therapy and/or pharmaceutical interventions, (a) correlating said level of Pro-Enkephalin or fragments thereof with kidney function in a subject or (b) correlating said level of Pro-Enkephalin or fragments thereof with kidney dysfunction wherein an elevated level above a certain threshold is predictive or diagnostic for kidney dysfunction in said subject or (c) correlating said level of Pro-Enkephalin or fragments thereof with said risk of an adverse event in a diseased subject, wherein an elevated level above a certain threshold is predictive for an enhanced risk of said adverse events or (d) correlating said level of Pro-Enkephalin or fragments thereof with success of a therapy or intervention in a diseased subject, wherein a level below a certain threshold is predictive for a success of therapy or intervention, wherein said therapy or intervention may be renal replacement therapy or may be treatment with hyaluronic acid in patients having received renal replacement or predicting or monitoring the success of therapy or intervention may be prediction or monitoring recovery of renal function in patients with impaired renal function prior to and after renal replacement therapy and/or pharmaceutical interventions,