Chapter 7 Urinalysis

Front 1

Urinalysis

Back 1

is an examination of urine to determine the presence of abnormal elements that may indicate various pathologic conditions.

Front 2

Color

Back 2

Normal urine color is yellow (amber) or straw-colored. A colorless, pale urine indicates a large amount of water in the urine, whereas a smoky-red or brown color of urine indicates the presence of large amounts of blood. Foods such as beets and certain drugs also can produce a red coloration of urine.

Front 3

Appearance

Back 3

Normally, urine should be clear. If it is is cloudy (turbid), this often indicates a urinary tract infection with pus (pyuria) and bacteria (bacteriuria).

Front 4

pH

Back 4

Determination of pH reveals the chemical nature of urine. It indicates to what degree a solution (such as urine or blood) is acidic or alkaline (basic). The pH range is between 0 (very acid) and 14 (very alkaline). Normal urine is slightly acidic (6.5). However, in infections of the bladder, the urine pH may be alkaline, owing to the actions of bacteria in the urine that break down the urea and release an alkaline substance called ammonia.

Front 5

Protein

Back 5

Small amounts of protein are normally found in the urine but not in sufficient quantity to produce a positive result bt oridnary methods of testing. When urinary tests for protein become positive, albumin is usually responsible. Albumin is the major protein in the blood plasma. If it is detected in urine (albuminuria), it may indicate a leak in the glomerular membrane, which allows albumin to enter the reanal tubule and pass into the urine.

Through more sensitive testing, abnormal amounts of albumin may be detected (microalbuminuria) when ordinary tests are negative. Microalbuminuria is recognized as the earliest sign of renal involvement in diabetes mellitus (see page 227) and essential hypertension (see page 226-227).

Front 6

Glucose

Back 6

Sugar is not normally found in the urine. In most caes, when it does appear (glycosuria), it indicates diabetes mellitus. In diabetes mellitus, there is excess sugar in the bloodstream (hyperglycemia), which leads to the "spilling over" of sugar into the urine. The renal tubules cannot reabsorb all the sugar thar filters out through the glomerular membrane.

Front 7

Specific gravity

Back 7

The specific gravity of urine reflects the amounts of wastes, minerals, and solids in the urine. It is a comparison of the density of urine with that of water. The urine of patients with diabetes mellitus has a higher-than-normal specific gravity because of the presence of sugar.

Front 8

Ketone bodies

Back 8

Ketones (or acetones, which are a type of ketone body) are breakdown products resulting from increased delivery of free fatty acids to the liver, and from catabolism of the fatty acids. Ketones accumulate in large quantities in blood and urine when the body breaks down fat, instead of sugar, for fuel. Ketonuria occurs in diabetes mellitus when cells deprived of surgar must use up their available fat for energy. In starvation, when sugar is not available, ketronuria and ketosis (ketones in the blood) occur as fat is catabolized abnormally.

The presence of ketones in the blood is quite dangerous because ketones increase the acidity of the blood (acidosis). This can lead to coma (unconsciousness and death).

Front 9

Sediment and casts

Back 9

The presence of abnormal particles in the urine is a sign of a pathologic condition. Such particles, which may settle to the bottom of a urine sample sediment, may include cells (epithelial cells, white blood cells, or red blood cells), bacteria, crystals, and casts (cylindrical structures of protein often containing cellular elements).

Front 10

Phenylketonuria (PKU)

Back 10

Phenylketones are substances that accumulate in the urine of infants born lacking the important enzyme phenylalanine hydroxylase. Normally, this enzyme changes the amino acid phenylaline to another amino acid, tyrosine. Lack of the enzyme causes phenylalanine to reach high levels in the infant's bloodstream, which will eventually lead to mental retardation. The PKU test, done just after birth, detecs the phenyleketonuria or phenylalaine in the blood. If it is detected, the infant is fed a low-protein diet that excludes phenylalanine to prevent mental retardation. The child remains on this diet until adulthood.

Front 11

Bilirubin

Back 11

This pigment substance, which results from hemoglobin breakdown, may be present in the urine, producing a darker appearance, as an indication of liver or gallbladder disease or excessive hemolysis (breakdown of hemoglobin is tood rapid for the liver to clear). When the liver has difficulty removing billrubin from blood, hyperbilrubinemia occurs and billrubinuria follows.