Clinical Investigation

Kidney International (1984) 25, 696–700; doi:10.1038/ki.1984.76

Foot process fusion and glomerular filtration rate in minimal change nephrotic syndrome

Sven-Olof Bohman1, Georg Jaremko1, Ann-Britt Bohlin1 and Ulla Berg1

1Departments of Pathology and Pediatrics, Karolinska Institute, Huddinge Hospital, Huddinge, Sweden

Correspondence: Dr A-B Bohlin, Department of Pediatrics, Huddinge Hospital, S-141 86 Huddinge, Sweden

Received 13 May 1983; Revised 20 September 1983.

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Abstract

Foot process fusion and glomerular filtration rate in minimal change nephrotic syndrome. Reduced glomerular filtration rate (GFR), not due to hypovolemia, has been reported in patients in the proteinuric phase of the minimal change nephrotic syndrome (MCNS). A group of children with MCNS was studied to investigate the possible relationship between the fusion of glomerular epithelial foot processes and the reduction in GFR. The degree of foot process fusion was estimated as the harmonic true mean of foot process width and the length density of epithelial slit pores as determined by quantitative electron microscopic stereology. In the patients investigated GFR ranged between 40 and 127 ml/min/1.73 m2 body surface area, the filtration fraction between 6.9 and 22.5%, and the serum albumin concentration between 14 and 46 g/liter. The mean foot process width, which varied between 330 and 870 nm, showed a close correlation with GFR (r = -0.859) and the filtration fraction (r = -0,812), as well as with the serum albumin concentration (r = -0.756). As expected, a reduction of epithelial slit pore length occurred concomitant with the broadening of the foot processes. These results agree with the hypothesis that the reduction in the total length of glomerular epithelial slit pores, due to the fusion of foot processes, results in a reduced glomerular capillary permeability to water and small solutes.

Fusion des pédicelles et débit de filtration glomérulaire au cours du syndrome néphrotique à lésions glomérulaires minimes. Une diminution du débit de filtration glomérulaire (GFR), non dûe à une hypovolémie, a été rapportée chez des malades à la phase protéinurique du syndrome néphrotique à lésions minimes (MCNS). Un groupe d'enfants atteints de MCNS a été étudié pour rechercher une relation possible entre la fusion des pédicelles épithéliaux glomérulaires et la réduction de GFR. Le degré de fusion des pédicelles a été estimé par la moyenne harmonique vraie de l'épaisseur des pédicelles et de la longueur de densité des pores épithéliaux déterminée par stéréologie en microscopic électronique quantitative. Chez les malades étudiés, GFR était comprise entre 40 et 127 ml/min/1,73 m2 de surface corporelle, la fraction de filtration entre 6,9 et 22,5%, et la concentration d'albumine sérique entre 14 et 46 g/litre. L'épaisseur moyenne des pédicelles qui variait entre 330 et 870 nm, présentait une corrélation étroite avec GFR (r = -0,859) et avec la fraction de filtration (r = -0,812), comme avec la concentration d'albumine sérique (r = -0,756). Comme prévu, une diminution de la longueur des pores épithéliaux apparaissait de façon concomitante avec l'élargissement des pédicelles. Ces résultats sont en concordance avec l'hypothèse qu'une réduction de la longueur totale des pores épilthéliaux glomérulaires, en raison d'une fusion des pédicelles, entraîne une diminution de la perméabilité capillaire glomérulaire à l'eau et aux petits solutés.

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