Amongst the various diagnostic studies that can be obtained in the ED, urinalysis is a virtually ubiquitous test. Urine itself reflects the functioning of the human body in both health and disease and the values it comprises can give us information regarding a myriad of conditions from infections, metabolic or endocrine derangements, and toxidromes to neoplastic processes and pregnancy. Despite this, many of the elements of even the standard urinalysis are often overlooked and underappreciated. In this talk we will explore some of these values and hopefully gain a renewed respect for the “golden cup of answers” and all that it may reveal.

Elements of Urinalysis

Let’s take a few moments to review the values that are tested on a standard urinalysis dipstick.(1,2)

Macroscopic

Color (reference yellow/straw):

Color can be abnormal in a wide range of pathology. Amber color can indicate concentration as seen with dehydration. Red urine can indicate hematuria, myoglobinuria, or may be explained by something as benign as the sliced beets your patient had with their most recent meal.

Clarity (reference clear):

Normal urine is clear, but can become turbid with various types of contaminants such as cellular debris, casts, crystals, or protein, and vaginal discharge, bacteria, or sperm.

Specific Gravity (reference 1.005 - 1.035):

In the broadest sense, specific gravity is a term that describes the density of a given substance relative to a reference substance, usually water. In physiologic terms, this value reflects the kidney’s ability to concentrate urine as well as the body’s overall hydration status. Low values are seen when urine is dilute, such as with diabetes insipidus or acute tubular necrosis, and high values indicate concentration or increased solutes such as in dehydration or proteinuria.

pH (reference 5.0 - 8.0):

pH can vary under normal circumstances by diet, with high protein diets yielding more acidic values. Acidic urine can also be the result of drugs, metabolic derangements such as DKA, dehydration, and diarrhea. Alkaline urine is found with various drugs (think salicylates and acetazolamide), infection with certain types of bacteria, and acute and chronic renal failure.

Protein (reference negative mg/dL)

Increased protein indicates impairment of the glomerular filtration apparatus. Common ED diagnoses that will exhibit proteinuria include congestive heart failure and diabetes, but it is also found in glomerulonephritis, pyelonephritis, preeclampsia and malignant hypertension. Albumin is the primary type of protein that will appear in urine, but other types can be found in states such as multiple myeloma. These other types are not detected on standard urine dipsticks.

Glucose (reference negative)

Glucose should be reabsorbed by the proximal tubules under normal conditions. When serum glucose concentration rises above 180 mg/dL then this reabsorptive capacity becomes overwhelmed and glucose will begin to appear in the urine. This is primarily observed in patients with diabetes mellitus, but can also be found in thyrotoxicosis, intravenous glucose administration, catecholamine surges, liver dysfunction, acute pancreatitis, and asphyxia (such as with CO poisoning).

Ketones (reference negative)

Ketone bodies reflect altered cellular metabolism when there is an inadequate supply of glucose to meet an increased metabolic demand. When glucose stores are depleted (or inaccessible as with type 1 diabetes), cells turn to using lipids instead, and ketones are the breakdown product of that process. They are commonly elevated in vomiting, diarrhea, and malnutrition, as well as pregnancy and hyperthyroidism, and are part of the diagnostic criteria for DKA.

Bilirubin (reference negative) and Urobilinogen (reference 0.2 - 1.0/EU/dL)

Bilirubin is a breakdown product of hemoglobin, and is normally reduced in the intestine to be excreted in urine as urobilinogen. Normally there is no bilirubin in urine, but when present it indicates liver disease. The pattern of obstructive disease includes elevated bilirubin and low urobilinogen. Hemolytic processes may show elevated urobilinogen as more hemoglobin than normal is processed. Urobilinogen can also be elevated when damage to liver parenchyma prevents its metabolism back to bilirubin. Specific processes include hepatitis, cirrhosis, pancreatic cancer, and choledocholithiasis.

Blood (reference negative)

Blood can be present in three possible forms: hematuria (results from whole red blood cells), hemoglobinuria (free hemoglobin), and myoglobinuria. A few red blood cells per HPF is normal in urine, but gross hematuria or myoglobinuria is unmistakeable even by simple visual inspection of its color. Specific conditions that can cause hematuria include many renal disorders such as calculi, neoplasms, infection, and drugs. Myoglobinuria will appear as blood on macroscopic exam with an incongruently small number of red blood cells on microscopic analysis and is usually the result of muscular trauma.

Nitrite (reference negative) and Leukocyte esterase (reference negative)

These values are the hallmarks of urinary tract infection. Nitrite is a product of the conversion of endogenous nitrates to nitrites and has high specificity for gram negative bacteriuria. Leukocyte esterase is an enzyme produced by white blood cells, usually in response to infection.