Using an autopsy case of a 59-year-old man with analgesic nephropathy, papillary necrosis, and nephrolithiasis, it is shown that analgesic nephropathy may be complicated by damage resulting from intrarenal urine reflux. The morphologic alterations characteristic of intrarenal and/or pyelointerstitial reflux are caused by high intrapelvic pressure values during episodes of renal colic. Bacterially infected and possibly also sterile urine is then forced into the interstitium, directly within the papillary defect or indirectly via the tubular system after rupture of the tubule. The result is a severe interstitial process with inflammation, destruction, and scarring.