The Renal Glomerulus of the Cat: Its Normal Structure and the Description of a Novel Glomerular Lesion

Familarity with the anatomy of the normal glomerulus would seem to be an essential pre-requisite to the understanding and the interpretation of the glomerular abnormalities as detected by light, electron microscopy and immunofluorescence both during and after pathological conditions. As glomerulonephritis is now recognised as being an important feline nephropathy the need for such a base-line study of the normal feline glomerulus was highlighted. In Chapter 1 of the present work, an attempt was made to elucidate the more important gaps in our understanding of the normal cat glomerulus. This was done with particular reference to a number of important parameters such as methods of fixation and embedding, section thickness and glomerular size variation within the kidney. In the course of this part of the work nine cats were found, at necropsy, to be suffering from a diffuse glomerular endothelial lytic lesion. Chapter 2 provided a detailed study of the sequential autolytic changes taking place after death in the cat kidney. The time scale of this experiment ranging from five minutes to six days following the animals demise. Autolytic changes were seen to occur very rapidly after death, although even with TEM, there were significant areas of tissue where recognisable cytological integrity had been preserved as late as 60 hours after death. In Chapter 3 the neonatal kidney was examined at the time of birth and at three day intervals until 70 days. This study attempted, once again, to illuminate those areas which no previous study had examined in the cat. Thus it was found that the nephrogenic zone persisted as late as eight weeks after birth. Chapter 4 dealt with those animals excluded from Chapter 1 due to their exhibiting a severe form of a glomerular endothelial lesion not previously described in the literature. This was a combined light, electron microscopy and immunofluorescence study. It revealed the complete destruction of the glomerular endothelium together with the partial destruction of the glomerular mesangium. This was accompanied by granular deposition of both IgG and C3 in the glomerular capillaries. In Chapters 5, 6 and 7 successive experimental attempts to elucidate the nature and occurrence of this novel lesion by examining both the physical parameters and the chemicals used in the primary study. Overall, by histological, ultrastructural and immunofluorescence methods of examination, the lesion recreated in Chapters 6 and 7 was seen to be identical, if differing in severity, to that noted in spontaneously occurring cases in Chapter 4. It was concluded that the anaesthetic agents employed in the present study, which are also used in general practice, were responsible for this novel lesion yet in an entirely random fashion. The consequences of this lesion occurring in the cat during routine and / or experimental procedures in which the structural detail of the glomerulus was under study were considered to merit further study