Peripheral microvascular parameters in the nephrotic syndrome.
BACKGROUND
Peripheral edema, in combination with severe proteinuria and low serum albumin levels, is pathognomonic of the nephrotic syndrome, yet the exact mechanism of its formation is unknown. Two of the most important of the factors in Starling's forces controlling fluid filtration across the capillary have hitherto not been studied in nephrotic subjects.


METHODS
The hydrostatic capillary pressure at the finger nail-fold in actively nephrotic subjects and age and sex matched controls was studied, using direct puncture of the apex of the capillary under video microscopy, and a servonulling apparatus to give a direct measurement of capillary pressure. Capillary filtration capacity (CFC) at the calf was measured noninvasively by a modern derivative of the technique of mercury strain gauge plethysmography. Fifteen nephrotic subjects with a variety of underlying pathological lesions, and age matched controls were studied.


RESULTS
Contrary to the assumption of the "overflow" hypothesis of edema formation, there was no evidence of capillary hypertension. The capillary pressure showed no difference between nephrotic subjects and controls: median (range) of 17.6 (12.0 to 24.2) compared with 17.3 (9.0 to 21.6) mm Hg, P = NS. CFC was significantly higher in nephrotic subjects than controls [5.23 (3.28 to 8.52) x 10(-3) versus 3.55 (2.43 to 5.28) x 10(-3) ml/min/100 g/mm Hg, P < 0.01].


CONCLUSIONS
An increase in CFC provides a potentially novel mechanism contributing at least in part to the formation of peripheral edema in the nephrotic syndrome.
Royal Devon and Exeter Hospital, and Department of Vascular Medicine, University of Exeter, England, United Kingdom. David.Lewis@dial.pipex.com
D M
DM
Lewis
J E
JE
Tooke
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M
Beaman
J
J
Gamble
A C
AC
Shore
D000328:Adult; D000368:Aged; D001794:Blood Pressure; D002196:Capillaries / Q000503:physiopathology; D016022:Case-Control Studies; D004487:Edema / Q000209:etiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008833:Microcirculation / Q000503:physiopathology*; D008875:Middle Aged; D009404:Nephrotic Syndrome / Q000209:etiology* / Q000503:physiopathology*