Human Physiology

Urinalysis (U/A)

Urinalysis can be used to detect a wide variety of disease states, particularly disorders of the urinary system (obviously). Urinalyses are easy to…

Dr. Shweta Bairagi · 04 Jun 2011

Urinalysis can be used to detect a wide variety of disease states, particularly disorders of the urinary system (obviously). Urinalyses are easy to misinterpret or ignore, however - hopefully this brief guide will help.Color: Usually clear to yellow. As a general rule, The more yellow, the more concentrated. Some drugs (such as rifampin) will color urine (rifampin orange, for example), and abnormally colored urine will give false readings on the dipstick labs, which rely on color for their interpretation.Clarity: Should be clear. UTI's lead to cloudy urine, because of cells or other particulate matter. Carbohydrates will also cloud a urine.pH: Urine pH usually reflects serum pH, but with much greater variablility. Normal is anywhere from 5.0 to 9.0.NOTE: If the pH is low (or if ascorbic acid [Vitamin C] is present in high quantities), this can lead to a FALSE NEGATIVE for nitrites - meaning that nitrites are really present, but they won't show up on the U/A.Ketones: elevated in dehydration, fasting, or DKA (diabetic ketoacidosis - seen in Type I diabetics).Hemoglobin (Hgb): if elevated,Without red cells present: hemolytic anemia (transfusion reaction?); error caused by lysing of old sampleWith red cells present: bladder trauma; tubular damageWith red cell casts present: glomerulonephritisBilirubin: This refers to conjugated bilirubin, Elevated in post- or intra- hepatic obstruction.Urobilinogen: This is elevated in conditions with high unconjugated bilirubin, such as hemolysis or Gilbert's Disease.Nitrites: This is elevated when bacteria (particularly Gram - organisms, generally fecal) are present in the urinary tract.Leukocyte Esterase: This enzyme is made by neutrophils as a response to the presence of bacteria. It indicates 2 things: [1] UTI; and [2] a functioning immune system. This will NOT rise in neutropenic patients, even if they have UTI's.Glucose: Glucose spilling into the urine indicates a serum glucose of >180. People with normal kidneys and normal glucose metabolism do not have glucose in their urine (they may have 1+ immediately after a high carb meal).Protein: The assays used in chemistry labs primarily detect albumin more than other proteins. These assays are not particularly good at detecting immunoglobulins, for example. If elevated, urinary protein indicates UTI, recent exercise or renal disease.IMPORTANT: U/A protein is not sensitive enough for the microalbuminuria seen in diabetes. If you wish to detect/measure this, order the Urine Microalbumin Assay specifically.IMPORTANT: If you suspect pre-ecplampsia or eclampsia, order a Total Urine Protein in addition to the U/A.Specific Gravity: This is used to infer volume status, which you should be able to assess clinically with more accuracy than this test will provide. If spec grav is elevated, that means the urine is concentrated, suggesting a hypovolemia . If the spec grav is low, that means the urine is dilute, suggesting hypervolemia . Optimally, U/A's will be collected first thing in the morning, when urine tends to be more concentrated. Spec grav goes up with high glucose or other elevated "stuff" in the urine.Casts: are associated with the collection of cells in the distal tubule, which become concretions after sufficient time has elapsed. They are generally associated with different conditions dependent on their color:Red = nephritic syndrome.White = pyelonephritis.Muddy brown = renal failure.Crystals: Seen in gout, kidney stones, or in the presence of many drugs.