Renal Function Tests Prof. K. Sivapalan.

Specific Gravity Normal to Indicates the degree of concentration. May be high when heavy molecular weight substances as some dyes are excreted. Less in compulsive drinking, chronic nephritis, diabetes insipidus

Volume 24 hour volume- normal 1500 ml or 1 ml/min. If close to 500 ml, specific gravity should be increased. If less than 400 ml, GFR is reduced. Water restriction test- indicates concentrating power, differentiate compulsive drinking from diabetes insipidus. Water diuresis- drinking of large volume of hypotonic fluid [water]- diuresis starts in 15 minutes, maximal in 40 minutes.- ADH

Proteinurea. Albumin can be present in diseases of glomerulus. Plasma proteins can be present on bleeding into nephrons, ureter, bladder, urethra. Some abnormal proteins can be filtered when produced

Haemoglobin Urea Haemoglobin can be filtered normally. Presence indicates intravascular haemolysis. Risk of haemoglobin crystalizing in tubules when concentration increases and blocking tubules

Microscopic Examination Red cells- inflammation or bleeding. In females- menstruation. White cells- few cells- normal. Increased means infection. Micro organisms- normal urethral commensasl or infection- [mid stream] Crystals, epithelial cells, casts- pathology

Titratable Acid, pH. Normal pH- 4.5 to 6. It is concentration and depends on urine flow also. Titratable acid does not account for acid combined with bicarbonate

Clearence. Clearence = UV/P It is an estimation of the volume of plasma cleared of a perticular substance in one minute. PAH- plasma flow Inulin, creatinine, urea – GFR. Because urea is diffusible in and out of tubules the value varies depending on the flow. Free water clearance- –C H 2 O = V - U osm V/ P osm

Blood Parameters Blood urea- increase means reduced renal function Electerolytes Bicarbonate and PCO 2 Protein

Imaging X’ray- stones Ultrasound- change in size, shape Intravenous pyelogram- internal structure- pelvis, ureters, bladder, urethra