Sentence:  Microscopically , both <WSD>kidneys</WSD> showed many small cortical scars in which there was glomerular and interstitial fibrosis , tubular atrophy , and an infiltration of lymphocytes and plasma cells . 
Meaning of the word marked with <WSD> tags:  either of two bean-shaped excretory organs that filter wastes (especially urea) from the blood and excrete them and water in urine