Kidney disease. Light micrograph of a section through a lesion (centre) in a kidney. This is a Kimmelstiel-Wilson lesion, which may develop in patients with diabetes mellitus. A lesion is a zone of tissue with impaired function as a result of damage by disease. Solid material has been deposited in round nodules (pink) in glomerular tufts. The glomerulus is a tightly coiled network of blood vessels. Magnification unknown.