Disease-state biomarker for renal disease

A method for treating a kidney disease, disorder or injury comprising:

• i) measuring the amounts of a D-form and L-form of at least one amino acid among amino acids in a sample of feces or intestinal content;
• ii) calculating a disease-state index value of a kidney disease/injury based on the amount of the D-form, the amount of the L-form, or the amount of the D-form and L-form, of the at least one type of amino acid;
• and
• iii) correlating a disease-state index value of a kidney disease/injury with the pathology of a kidney disease/injury,
• wherein the disease-state index value of a kidney disease/injury is the ratio of the amount of the D-form to the sum of the amounts of the D-form and the L-form, the ratio of the amount of the L-form to the amount of the D-form, or the ratio of the amount of the D-form to the amount of the L-form, of the at least one type of amino acid, and
• wherein the ratio further determines a treatment plan comprising at least one of dietary guidance, blood pressure management, blood glucose level management, or lipid management.