Assessment of KDIGO definitions in patients with histopathologic evidence of acute renal disease

Abstract

Background and objectives: AKI is a clinical syndrome with various causes involving glomerular, interstitial, tubular, and vascular compartments of the kidney. Acute kidney disease (AKD) is a new concept that includes both AKI and the conditions associated with subacute decreases in GFR (AKD/non-AKI). This study aimed to investigate the correlation between AKI/AKD defined by clinical presentation and diffuse histologic criteria for acute abnormalities based on renal biopsy.

Design, setting, participants, & measurements: All 303 patients who were histologically diagnosed as having acute tubular necrosis (ATN), acute tubulointerstitial nephritis, cellular crescentic GN, acute thrombotic microangiopathy, or complex lesions on renal biopsy from January 2009 to December 2011 were enrolled in the study. The 2012 Kidney Disease Improving Global Outcomes AKD/AKI definitions were applied to classify patients as follows: AKI, AKD/non-AKI, non-AKD, or unclassified.

Results: A total of 273 patients (90.1%) met the AKD criteria; 198 patients (65.3%) were classified as having AKI according to serum creatinine (SCr) and urine output criteria. The urine output criteria added 4.3% to the SCr criteria and reclassified 6.7% of the AKI cases into higher stages. Of patients with ATN on pathology, 79.2% met AKI criteria; this was a higher percentage than for those who had other individual pathologic lesions (50%-64%). The major cause of not being defined as having AKI was a slower SCr increase than that required by the definition of AKI (98, 93.3%). Patients with AKI had more severe clinical conditions and worse short-term renal outcome than those in the non-AKI group.

Conclusions: Diffuse, acute abnormality defined by renal biopsy and AKI defined by clinical presentation are two different entities. Most patients who have diffuse acute histologic findings met the criteria for AKD, whereas only two thirds met the definition of AKI.

Keywords: acute kidney disease; acute kidney inury; diagnosis; pathology.

Figure 1.

Flowchart of patient enrollment. ATN, acute tubular necrosis; ATIN, acute tubulointerstitial nephritis; CCGN, cellular crescentic GN; G, glomeruli; TIN, tubulointerstitial nephritis; TMA, thrombotic microangiopathy.

Figure 2.

Clinical grouping of patients with renal parenchymal acute lesions.

Figure 3.

Acute diffuse abnormality defined by renal biopsy and AKI defined by clinical presentation are two different entities. (A) No significant difference was seen in the composition of various pathological changes among different clinical groups. (B) AKI definition identified all patients with complex lesions and more cases from the ATN group than any other individual pathological groups. In addition, 2.2% of patients with cellular crescent GN (CCGN) and 22.7% of patients with thrombotic microangiopathy (TMA) were grouped as unclassified. AKD, acute kidney disease.