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MATRIC NO.: 12/MHS01/076
COURSE: BIOCHEMISTRY PRACTICAL
COURSE CODE: BCH 313
LEVEL: 300L
DATE: 15TH JUNE, 2015.
QUESTION: Discuss the clinical significance of glycosuria and ketonuria
Glucose urine test
The glucose urine test measures the amount of sugar (glucose) in a urine sample. The presence of
glucose in the urine is called glycosuria or glucosuria. Glucose level can also be measured using a
blood test or a cerebrospinal fluid test.
This test was commonly used to test for and monitor diabetes in the past. Now, blood tests to
measure glucose level in the blood are easy to do and used instead of the glucose urine test. The
glucose urine test may be ordered when the doctor suspects renal glycosuria. This is a rare condition
in which glucose is released from the kidneys into the urine, even when blood glucose level is
normal. Glucose is not usually found in urine. If it is, further testing is needed. Normal glucose range
in urine: 0 - 0.8 mmol/l (0 - 15 mg/dL).
Higher than normal levels of glucose may occur with:
Diabetes-- Small increases in urine glucose levels after a large meal are not always a cause for
concern.
Gestational Diabetes in Pregnancy -- Up to half of women have glucose in their urine at some time
during pregnancy. Glucose in the urine may mean that a woman has gestational diabetes.
Renal glycosuria: A rare condition in which glucose is released from the kidneys into the urine, even
when blood glucose levels are normal (renal glycosuria). Blood is filtered by millions of nephrons, the
functional units that comprise the kidneys. In each nephron, blood flows from the arteriole into the
glomerulus, a tuft of leaky capillaries. The Bowman's capsule surrounds each glomerulus, and
collects the filtrate that the glomerulus forms. The filtrate contains waste products (e.g. urea),
electrolytes (e.g. sodium, potassium, chloride), amino acids, and glucose. The filtrate passes into the
renal tubules of the kidney. In the first part of the renal tubule, the proximal tubule, glucose is
reabsorbed from the filtrate, across the tubular epithelium and into the bloodstream. The proximal
tubule can only reabsorb a limited amount of glucose. When the blood glucose level exceeds about
160 – 180 mg/dl, the proximal tubule becomes overwhelmed and begins to excrete glucose in the
urine. This point is called the renal threshold of glucose (RTG). Some people, especially children and
pregnant women, may have a low RTG (less than ~7 mmol/L[3] glucose in blood to have glucosuria).
If the RTG is so low that even normal blood glucose levels produce the condition, it is referred to as
renal glycosuria. Glucose in urine can be identified by Benedict's qualitative test.
Clinical Significance of Glucose in the Urine
In a healthy individual, almost all of the glucose filtered by the renal glomerulus is reabsorbed in the
proximal convoluted tubule. The amount of glucose reabsorbed by the proximal tubule is
determined by the body's need to maintain a sufficient level of glucose in the blood. If the
concentration of blood glucose becomes too high (160-180 mg/dL), the tubules no longer reabsorb
glucose, allowing it to pass through into the urine. It is important to note that glucose may appear in
the urine of healthy individuals after consuming a meal that is high in glucose. Fasting prior to
providing a sample for screening eliminates this problem. Conditions in which glucose levels in the
urine are above 100 mg/dL and detectable include: diabetes mellitus and other endocrine
disordersimpaired tubular reabsorption due to advanced kidney diseasepregnancy - glycosuria
developing in the 3rd trimester may be due to latent diabetes mellituscentral nervous system
damagepancreatic diseasedisturbances of metabolism such as, burns, infection or fractures.
Conditions in which glucose levels in the urine are above 100 mg/dL and detectable include: diabetes
mellitus and other endocrine disorders, impaired tubular reabsorption due to advanced kidney
disease, pregnancy - glycosuria developing in the 3rd trimester may be due to latent diabetes
mellituscentral nervous system damagepancreatic diseasedisturbances of metabolism such as,
burns, infection or fractures.
KETONURIA
Ketonuria is a medical condition in which ketone bodies are present in the urine. It is seen in
conditions in which the body produces excess ketones as an indication that it is using an alternative
source of energy. It is seen during starvation or more commonly in type I diabetes mellitus.
Production of ketone bodies is a normal response to a shortage of glucose, meant to provide an
alternate source of fuel from fatty acid. Ketones are metabolic end-products of fatty acid
metabolism. In healthy individuals, ketones are formed in the liver and are completely metabolized
so that only negligible amounts appear in the urine. However, when carbohydrates are unavailable
or unable to be used as an energy source, fat becomes the predominant body fuel instead of
carbohydrates and excessive amounts of ketones are formed as a metabolic byproduct.
Higher levels of ketones in the urine indicate that the body is using fat as the major source of
energy. Ketone bodies that commonly appear in the urine when fats are burned for energy are
acetoacetate and beta-hydroxybutyric acid. Acetone is also produced and is expired by the lungs.[1]
Normally, the urine should not contain a noticeable concentration of ketones to give a positive
reading. As with tests for glucose, acetone can be tested by a dipstick or by a lab. The results are
reported as small, moderate, or large amounts of acetone. A small amount of acetone is a value
under 20 mg/dl; a moderate amount is a value of 30–40 mg/dl, and a finding of 80 mg/dl or greater
is reported as a large amount.
Interpretation of results
Normally only small amounts of ketones are excreted daily in the urine (3-15 mg). High or increased
values may be found in:
Poorly controlled diabetes.
Diabetic ketoacidosis (DKA).
Starvation: Not eating for prolonged periods (12 to 18 hours)
Anorexia nervosa
Bulimia nervosa
Alcoholism
Poisoning (eg with isopropanol)
Ether anaesthesia
Alkalosis
False positives: It is also possible to have a positive test result but 'no' ketones i.e ketones are
actually absent in the urine. Taking some medications can create false positive results. Such
medications include: Levodopa - eg, Sinemet®, Phenazopyrazine, Valproic acid, Vitamin C,
Dehydration.
False negatives: Most urine testing kits detect aceto-acetate, not the predominant ketone betahydroxybutyrate. It is possible for the test to be negative with high levels of beta-hydroxybutyrate
and then, as ketoacidosis improves and ketone levels fall, the urine test becomes positive (to acetoacetate).
Special cases of ketonuria: Metabolically severe insulin deficiency (relative or absolute) produces
hyperglycaemia and ketoacidosis. Insulin lack increases release of fatty acids from adipose stores
and reduces the rate of fat synthesis. Lipolysis is further increased by increased catecholamines,
cortisol, growth hormone and glucagon. The free fatty acids are transported to the liver for
conversion to ketone bodies, which serve as fuels for muscle and fat. Excess production of ketone
bodies (aceto-acetate and beta-hydroxybutyrate) gives rise to ketoacidosis. Beta-hydroxybutyrate
accounts for 75% of ketones. Urine is tested for ketones as part of monitoring of type 1 diabetes
mellitus. Home blood glucose and ketone monitoring can possibly decrease the number of hospital
admissions due to diabetic ketoacidosis.
Monitoring of ketones is important in all people with diabetes: When the diet is low in
carbohydrates, exercise levels are high or a combination of both, In pregnant women with diabetes
and in gestational diabetes, When blood sugars are high (over 15 mmol/L), In DKA or with
suspected ketoacidosis. Patients with diabetes who detect high levels of ketones in their urine
should seek medical advice.