amount of albumin is observed in urine in insulin-dependent diabetics, and this
finding appears to correlate with very early diabetic nephropathy. Immune complex
disease also affects the glomerules. In such progressive renal disease, the ability to
restrictfiltration of smallest of larger proteins is lostfirst. Thus albumin appearsfirst
in urine. Large proteins are not seen in urine. Progressively, severe glomerular
lesions produce less selective proteinuria that pass proteins of all sizes through the
glomerulus and is called nonselective proteinuria. In thefinal stage of disease, as
glomeruli are destroyed, proteinuria decreases and renal failure results.
Glomerular proteinuria with pathological damage to the glomerulus may be
divided into two types, i.e., non-nephrotic proteinuria and nephrotic proteinuria
based on the quantity of protein excretion. Nephrotic-range proteinuria is associated
with loss of 3 g or more proteins in 24 h urine, while there is presence of 2 g of
protein/g of urine creatinine in a single-spot urine collection. Thisfinding denotes
significant glomerular disease. Nephrotic syndrome is another clinical representation
showing the combination of nephrotic-range proteinuria with a low serum albumin
level and edema. The amount of proteinuria is <3.5 g/24 h and is persistent in case of
non-nephritic proteinuria.
Tubular Proteinuria It is characterized by the appearance of low molecular weight
proteins such asα-microglobulin, delta globulin such asβ 2 -microglobulin, light
chain immunoglobulin, and lysozymes in the urine because of defective reabsorption
of these compounds in the proximal renal tubules. The amount of proteinuria is about
1 – 2 g/day.
Post Renal ProteinuriaIt occurs due to proteins arising from the urinary tract and
is usually due to inflammation or malignancy lesions (stones, tumor, growth) of renal
pelvis, bladder, and prostate of urethra.
Fig. 8.1Types of proteinuria
8.2 Tests for Urinary Proteins 37