Renal biopsy specimen obtained at the time of clinical presentation with advanced renal impairment. There is severe tubular atrophy and interstitial changes consistent with an advanced chronic interstitial nephropathy. A) Low power haematoxylin and eosin stain demonstrating chronic interstitial nephropathy. B) High power view indicating tubular debris within the nephron lumen (arrowed). C) High power view demonstrating marked tubular cell vacuolisation. D) PAS stain demonstrating thickened basement membrane and marked cytoplasmic lypochrome pigmentation.