Page 95 - Clinical Biochemistry

• Normal glomerular membrane normally does not allow passage of albumin and large m.wt.
protein.

• Less than 25 mg/24 hr urine (albumin)
• In nephrotic syndrome, significant damage to glomerular membrane has occurred and 250

mg/24 hr albumin can be detected.
• Assessment for proteinuria—Usually assessed by measuring urinary albumin/Cr ratio.

Renal tubular function

Renal tubules

• Make up to 95% of the renal mass
• Do the bulk of the metabolic work and modify the ultrafiltrate into urine.
• They control a number of kidney functions including
1. Acid-base balance
2. Sodium and potassium excretion
3. Urine concentration or dilution
4. Water balance
5. Small molecule metabolism (such as insulin clearance).

Investigation of tubular function

1- Osmolality measurement in plasma and urine:
• It is the measurement of osmotic conc. of plasma and urine
• Normal Urine/plasma osmolality ratio is above 3.
• If the ratio is 1, the renal tubules are not reabsorbing water efficiently.
2- Urine pH
• Usually acidic (pH = 6).
• Tubules excrete hydrogen ion by different mechanism any defect leads to renal tubular

acidosis.
3- Urine concentration test:
• In CKD, kidneys loses the ability to concentrate urine.
• Specific gravity is measured in urine
• Low fixed specific gravity is indicative for CKD
4. Urine dilution test: