ABSTRACT
Thirty-seven young healthy subjects with normal renal function were studied to assess the quantitative effect of protein intake on creatinine clearance. A standard 24-h urine collection and blood sample at the end of the collection were obtained for creatinine and urea concentrations. Correlations between creatinine clearance and urinary urea nitrogen excretion (r = 0.8; P less than 0.0001) and calculated protein intake (r = 0.8; P less than 0.0001) were observed. A significant relationship between creatinine clearance and urea nitrogen excretion was also demonstrated in 28 elderly healthy subjects and 33 patients with renal disease. To demonstrate a cause and effect between urea nitrogen excretion and creatinine clearance in healthy subjects, 18 of the 37 healthy subjects repeated the 24-h urine collection and blood sample after ingesting 5 g of urea in addition to their usual diet. Mean urinary urea nitrogen excretion increased from a mean value of 9.8 +/- 4.0 to 11.8 +/- 4.0 g/day. There was a strong correlation between the changes in urea nitrogen excretion and the changes in creatinine clearance. In acute studies with oral protein loading, there was a significant correlation between creatinine clearance and urinary urea nitrogen excretion. It was concluded that protein intake has a direct and quantitative effect on creatinine clearance in healthy subjects. In normal humans, it is likely that GFR is not a fixed function. Thus, a low creatinine clearance is not a categorical sign of renal disease. A low creatinine clearance adjusted for urea nitrogen excretion may be a useful clinical tool to assess renal function.
Subject(s)
Creatinine/metabolism , Dietary Proteins/administration & dosage , Kidney Diseases/metabolism , Adult , Age Factors , Aged , Aged, 80 and over , Blood Urea Nitrogen , Female , Glomerular Filtration Rate , Humans , Kidney Diseases/diet therapy , Male , Middle AgedABSTRACT
Histiocytosis-X (H-X) is heterogeneous clinically, varying from localized benign forms to disseminated fatal forms, but has a relatively uniform and specific pathologic appearance, both by light and electron microscopy. H-X localized to bone or lung has long been recognized. Much less frequent are patients with H-X localized to skin. We report two infants with congenital self-healing H-X, clinically confined to the skin. Prediction of the clinical course from the histology of a H-X lesion is unreliable, especially for cutaneous lesions. We feel that patients with localized forms of H-X should be followed closely for progression of disease but should not be treated aggressively until time is allowed for spontaneous resolution.