Renal lesions in Norwegian slaughter pigs. Macroscopic and light microscopic studies

Six hundred and sixty-eight consecutive carcasses of slaughtered swine were examined for renal lesions at meat inspection. The macroscopic lesions were divided into 7 categories: D1 = depressions of the external surface and partial persistence of fetal lobation; D2 = focal leukolymphocytic nephritis (acute focal tubulo-interstitial nephritis); D3 = cysts; D4 = interstitial fibrosis; D5 = infarct-like lesions; D6 = fatty degeneration, and D7 = hydronephrosis. 396 (59.3%) of the examined carcasses were diagnosed as having one or more of these renal lesions. Two hundred and seventy-two (40.7%) of the carcasses were macroscopically judged as having normal kidneys. A selected material of 250 kidneys representative for each group of lesions based on macroscopic examination and 50 normal kidneys were prepared for histological examination. In the group of kidneys with the macroscopic diagnosis interstitial fibrosis (D4), an accompanying histological finding was proliferative glomerular changes with fatty degeneration of the proximal tubules. Cortical infarct-like lesions (D5) were observed in the absence of thrombo-embolic disease and were considered to have developed in association with local arterial alterations similar to polyarteritis nodosa.