Plain X-ray flims -of kidneny, ureters and bladder (KUB). Renal outline can be difined and calcification may be detected In renal areas, ureteric

tubular function.1. Tubular concentration of urine - (a) Specifc gravity of urine (range 1.005-1.004). For greater accuracy. (b) Urine osmolality (range 30 -1400 mOsmol). After overnight fluid deprivation, urine osmolality usually exceeds 600 mosmol'/1( sp. gr.>1015) In more formal tests.fluid deprivaiion for upto 24- hrs or injection of antiduratic hormone (vasopressin tannate) should increase urinary osmolality to 750 mOsmol/1 or more. 2. Urinary acidifition - Kidneys must axcrate 70-100 m mol of non-valatile acids/'day. otherwise plasma pH 'falls and urine pH is high. ph of urine can be assessed by dipstic A more formal testl is the add load test Ammonium chloride 100 mg/kg is given orally over 30-60 minutes (to avoid vomiting). Urine pH and plasma bicarbonate are measured over 3 hrs. "the Bicarbonate concerrtration should falI below 18 mmol/1 and urine pH below 5.3. In metabolic acidosisr plasma bicarbonate is allready <>