Histological Features of Acute Tubular Necrosis in Native Kidneys and Long-Term Renal Function

There are few studies on the relationship between the morphology of acute tubular necrosis (ATN) in native kidneys and late functional recovery. Eighteen patients with acute renal failure (ARF) who had undergone renal biopsy were studied. All had the histological diagnosis of ATN and were followed for at least six months. Clinical characteristics of ARF were analyzed, and histological features were semi-quantitatively evaluated (tubular atrophy, interstitial inflammatory infiltrate, interstitial fibrosis, and ATN). According to the maximal GFR achieved during the follow-up, patients were divided into two groups: complete recovery (GFR ≥ 90 mL/min/1.73 m²) and partial recovery (GFR < 90 mL/min/1.73 m²). Only 39% of the patients achieved complete recovery. Patients with partial recovery achieved their maximal GFR (63 ± 9 mL/min/1.73 m²) 37 ± 14 months after ARF, a period of time similar to those patients with complete recovery (i.e., 54 ± 22 months). Patients with partial recovery had more severe ARF: oliguria was more frequent (90 versus 17%, p < 0.01), and they had higher peak creatinine (13.85 ± 1.12 versus 8.95 ± 1.30 mg/dL, p = 0.01), and longer hospitalization (45 ± 7 versus 20 ± 4 days, p = 0.03). No single histological parameter was associated with partial recovery, but the sum of all was when expressed as an injury index [4.00 (2.73–5.45) versus 2.00 (1.25–3.31), p < 0.05]. In conclusion, among patients with atypical ATN course, those with more severe ARF and tubule-interstitial lesions are more prone to partial recovery.