77-year-old female patient developed a left-sided hemiplegia two weeks after she suffered a myocardial infarction. She succumbed to pneumonia after another 7 days (specimen from autopsy).
- A section of the kidney with medulla and cortex is shown. At low magnification, a subcapsular trapezoid-shaped zone is observed exhibiting lighter and more homogenous staining. Within this area diffuse ischemic necrosis is observed with preservation of the glomerular and tubular architecture. In the periphery of the necrotic zone, the blood vessels show extensive congestion; a scant infiltrate of neutrophilic granulocytes is observed.
- The distal part of the medulla shows fibrosis and tubular atrophy.
Renal infarcts are the result of complete and sudden obstruction of major branches of renal arteries and less frequently of renal veins. Emboli originating from ventricular thrombi or from vegetations of heart valves are most frequently involved in causing complete arterial blockage. The patient described exhibited an embolus in an arteria radiata. Besides, arterial occlusion may be due to thrombosis of vessels exhibiting pathological changes of the wall (atherosclerosis, malignant hypertensive disease, polyarteritis, and aneurysm formation due to dysplasia of the renal artery).
The necrotic material incites an inflammatory response which is subtle in the example shown. This indicates that the infarction occurred very recently. A well-defined inflammatory response is usually present after one to two days. Over time, a reparative response will occur and the necrotic tissue will be ultimately replaced by a scar.