Case 46: Renal infarct

This 55 year old man had a 2 month history of increasing confusion and loss of weight. He also complained of a 1 day history of left arm weakness. He was a smoker and had a past history of alcohol abuse. In hospital he developed increasing coma with no evidence of infection or CNS abnormality on CT scan. He was treated with antibiotics and steroids with dramatic improvement in his conscious state, but persistence of his left arm weakness. Six days after admission he suffered a grand mal seizure in the morning and later that day collapsed suddenly. He was shocked and his haemoglobin was noted to have dropped. He was treated with fluid replacement unsuccessfully.

At autopsy he was found to have a massive primary retroperitoneal haemorrhage, primary carcinoma of the lung with metastases to local lymph nodes and the cerebellum, multiple pulmonary emboli with associated infarction and vegetations on both the aortic and mitral valves with multiple focal infarcts in the brain and both kidneys. In addition, there was an organising inferior myocardial infarct associated with subendocardial foci of more recent ischaemic damage which may have an embolic aetiology.

Macroscopic pathology

Microscopic pathology

Macroscopic examination of the section of kidney shows well demarcated areas which are paler that the surrounding tissue. A bluish line is seen at their margins.

Closer examination under the microscope reveals that these blue areas contain large numbers of viable and degenerate neutrophil polymorphs (1). In the pale areas ghost outlines of tubules and glomeruli (1), (2), are recognised. The cell outlines are preserved but the cytoplasm is a diffuse pink colour and most of the nuclei have disappeared. Some pyknotic nuclei remain within the glomeruli.
Some of the glomerular capillaries adjacent to the area of infarction appear congested. This is a common finding in recent infarcts and macroscopically can give a hyperaemic border to the pale area of infarction.

Normal renal system tissues

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Micro 1 of 2

Micro 2 of 2

Test yourself on the pictures of this case - Link to the renal system test pictures

Commentary

In infarction nuclear changes due to necrosis include disappearance of nuclei (karyolysis), nuclear condensation and reduction in size (pyknosis) and nuclear fragmentation (karyorrhexis). This form of necrosis in which cell outlines are preserved is called coagulative necrosis. The peripheral neutrophilic infiltration is an early response on the part of the body to an area of tissue damage. In time granulation tissue and subsequently mature fibrous tissue will replace the infarcted tissue.

Learning objectives

1. Identify the features of renal infarction
2. Recognise coagulative necrosis