[A Case of IgG4-Associated Tubulointerstitial Nephritis Developing into End-Stage Renal Dysfunction Even after Release of Urinary Obstruction by Ureteral Stenting].

A 74-year-old woman was transported to an emergency room of a general hospital with sudden left flank pain. After examination, the pain was attributed to left hydronephrosis resulting from left retroperitoneal fibrosis (RF). The pain and renal function improved after left ureteral stenting. Four months after the transportation, she was referred to our hospital for further examination. Her renal function deteriorated again despite successful release of ureteral obstruction. Consequently, the left kidney developed end-stage renal dysfunction at 15 months after symptom onset. Pathological examination of the left dysfunctional kidney removed by laparoscopic surgery to avoid infectious pyelonephritis revealed numerous IgG4-positive plasma cells invading the renal parenchyma. The pathological findings suggested that the renal dysfunction was due to IgG4-related tubulointerstitial nephritis (IgG4-TIN) rather than ureteral obstruction. In the case of RF with decreased renal function, not only retroperitoneal lesion biopsy but also renal biopsy should be considered to diagnose IgG4-TIN and start steroid treatment if necessary.