Lecture 9 Urine and serum proteins
Proteinuria • Presence of excess of serum proteins in the urine is called proteinuria. • The excess of protein leads to foamy or frothy urine • Up to 150 mg a day of protein may be excreted by a normal person, primarily the Tamm-Horsfall protein
Causes of proteiuria • Dehydration • Emotional stress • Fever • Heat injury • Inflammatory process • Intense activity • Most acute illnesses • Orthostatic (postural) disorder
Types of proteinuria • Glomerularproteiuria • Tubular proteiuria • Overflow proteiuria
Glomerularproteiuria • Most common type of proteiuria • Increased glomerular permeability • Amount may vary from several hundred mg to > 100 gm per day
Tubular proteiuria • Low molecular weight proteins are filtered by glomerulus but are reabsorbed by tubules • Less than 150 milligram are excreted out in urine. • More than 150 mg are excreted out , it means that tubular function is damaged. • Β2- microglobulin, immunoglobin light chains, aminoacids, and retinol binding protein etc.
Overflow proteiuria • Overproduction • Multiple myeloma
Detection of proteinuria • Urine dipstick • But do consider specific gravity • If specific gravity is high then it may give positive dipstick test even if no proteinuria or low proteinuria • If sp gravity is low then even if proteinuria is present dipstick may be negative Dipstick test will also be negative if low molecular weight proteinuria is present (sulfosalicylic acid test or protein electrophoresis)
24 hour urine collection for protein • Urine dipstick is semiquantitative test • For persistent proteiuria 24 hr urine should be tested for protein • Creatinine should also be checked • Male excrete 20-25 mg/kg of creatinine in 24 hrs • Female excrete 15-20 mg/kg of creatinine in 24 hrs Normal protein excretion ……………..
Urinary protein: creatinine ratio • It can be done on a random spot urine • urine protein measured in mgldL by the urine creatinine measured in mgldL • For example, a urine protein to creatinine ratio of 4 corresponds to the excretion of 4 grams of protein over a 24-hour time period
Differentiation between glomerular and other types of proteiuria • if hematuria is present, especially if red blood cell casts or dysmorphic red blood cells are noted on examination of the urinary sediment. • When no hematuria 24-hour urine collection for protein or urine protein:creatinine ratio can help to differentiate.
If protein excretion exceeds 3 g/day, glomerular proteinuria is very likely • If protein excretion is <3 g/day, glomerular, tubular, or overflow proteinuria may be present • Urine protein electrophoresis is a useful test in patients who excrete < 3 g of protein/day • When >70 % of the total protein is albumin, glomerular proteinuria is said to be present • When globulin is in excess then other than glomerular type are present
When globulin is more as compared to albumin then tubular or overflow proteinuria. • Differentiation between tubular and overflow proteiuria is made on the basis of electrophoresis • Single globulin peak overflow proteinuria • Multiple peaks tubular proteinuria
Microalbuminuria • urinary excretion of albumin that is below the detection capability of the urine dipstick (30-300 mg/day) but above the upper limit of normal for healthy individuals • diabetic patients earliest clinical finding of diabetic nephropathy. • annually in diabetes mellitus type I, beginning 5 years after the diagnosis • annually in diabetes mellitus type II, beginning at the time of diagnosis
24-hour urine collection • albumin:creatinine ratio on an untimed urine specimen (ratio >30 mg/g is considered a positive test result). • Fever, exercise, and congestive heart failure are other causes of microalbuminuria. • repeating the test for confirmation of microalbuminuria.
Quiz • Q no 1: On urine electrophoresis of a patient, bencejonesproteins were detected. What type of proteinuria you suspect in this patient? (2) • Q no 2: Define microalbuminuria? Which test you will advise for diagnosis? (3)