Acute kidney injury in immunoglobulin A nephropathy: potential role of macroscopic hematuria and acute tubulointerstitial injury.

The aim of our retrospective study was to analyze the clinical course and outcome of patients with immunoglobulin A (IgA) nephropathy who presented with macroscopic hematuria and acute kidney injury (AKI). During the period from 1990 to 2005, seven out of 584 adult patients with IgA nephropathy (1.2%) fulfilled the criteria for macroscopic hematuria-induced AKI. There was an equal gender distribution among our patients, and a rather high average age at presentation (55.7 +/- 10.9 years). Four patients who were oliguric upon admission to hospital needed hemodialysis treatment. The average serum creatinine at the time of kidney biopsy was 429.8 +/- 377 micromol/L (median value 378). The percutaneous kidney needle biopsies showed focal proliferative crescentic glomerulonephritis of subclass III, according to the Haas scheme, associated with prominent red blood cell tubular casts and acute tubulointerstitial nephritis. Four patients with the most prominent crescents and tubulointerstitial involvement were treated with methylprednisolone. All patients, treated and untreated, recovered their kidney function (the serum creatinine at a median follow-up of 15 months was 111.7 +/- 38 micromol/L). In conclusion, AKI in IgA nephropathy accompanied by macroscopic hematuria appears to have been a reversible condition in our series of patients. Regarding pathogenesis, the kidney biopsy study points to the important role of glomerular bleeding with consequent, widespread obstructive red blood cell tubular casts accompanied by tubular injury and interstitial nephritis.