There is a considerable lack of data concerning the diagnostic testing for kidney damage after surgical procedures. In this situation the most important variables should be examined with respect to their clinical informative value, the costs associated with their analysis, and their potential use in routine diagnostic testing. Forty patients in the surgical intensive care unit (ICU) with acute kidney injury (AKI) that developed during their stay of 13–18 (median, 16) days in the ICU were examined daily during their entire ICU admission. The bulk of the laboratory research consisted of the measurement of creatinine, urea, and sodium, as well as clearances rates and diuresis. Various tests for diagnosing regional renal damage (enzymes and proteins) were also carried out. The included photometry, nephelometric analysis, and ELISA (enzyme-linked immunosorbent assay). Five days before an AKI became evident, pathologic levels of urinary α1-microglobulin (tubular parameter) could already be confirmed. Serum creatinine values or creatinine clearance indicated the presence of disease only 1 day before the AKI was seen. Our results show that determination of α1-microglobulin and immunoglobulin G (glomerular parameter) levels, in addition to the level of urea in serum, be recommended for patients in surgical intensive care units who are at risk for AKI. Use of these procedures can achieve early recognition and sufficiently precise localization of renal damage.