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
acids. Pathophysiology
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. 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. One 2010 study admits that though
ketonuria's relation to general metabolic health is ill-understood,
there is a positive relationship between the presence of ketonuria after fasting
and positive metabolic health. Screening
Screening for ketonuria is done frequently for acutely ill patients,
presurgical patients, and pregnant women. Any diabetic patient who has
elevated levels of blood and urine glucose should be tested for urinary
ketones. In addition, when diabetic treatment is being switched from insulin
to oral hypoglycemic agents, the patient's urine should be monitored for
ketonuria. The development of ketonuria within 24 hours after insulin withdrawal
usually indicates a poor response to the oral hypoglycemic agents. Diabetic
patients should have their urine tested regularly for glucose and ketones,
particularly when acute infection or other illness develops.
In conditions associated with acidosis, urinary ketones are tested to assess the
severity of acidosis and to monitor treatment response. Urine ketones appear
before there is any significant increase in blood ketones; therefore, urine
ketone measurement is especially helpful in emergency situations. During
pregnancy, early detection of ketonuria is essential because ketoacidosis is a
factor associated with intrauterine death.
Causes of ketosis and ketonuria Metabolic abnormalities such as
diabetes, renal glycosuria, or glycogen storage disease
Dietary conditions such as starvation, fasting, high protein, or low
carbohydrate diets, prolonged vomiting, and anorexia
Conditions in which metabolism is increased, such as hyperthyroidism,
fever, pregnancy or lactation In non-diabetic persons, ketonuria may
occur during acute illness or severe stress. Approximately 15% of
hospitalized patients may have ketonuria, even though they do not have
diabetes. In a diabetic patient, ketone bodies in the urine suggest that the
patient is not adequately controlled and that adjustments of medication, diet, or
both should be made promptly. In the non diabetic patient, ketonuria reflects a
reduced carbohydrate metabolism and an increased fat metabolism.
Test equipment A wide variety of companies manufacture
ketone screening strips. A strip consists of a thin piece of plastic film
slightly larger than a matchstick, with a reagent pad on one end that is either
dipped into a urine sample or passed through the stream while the user is
voiding. The pad is allowed to react for an exact, specified amount of time; its
resulting colour is then compared to a graded shade chart indicating a
detection range from negative presence of ketones up to a significant quantity.
It is worth noting that in severe diabetic ketoacidosis, the acidosis
causes acetoacetate to accept an H+ and become betahydroxybutyrate. Since the
nitroprusside reaction on dipstix detects acetoacetate but NOT
betahydroxybutyrate, this can be deceptive in very acidotic patients.
References ^ Detection of Ketones and Monitoring of
Diabetic Ketoacidosis-cov-7 ^ Nam-Seok Joo at al. Ketonuria after
Fasting may be Related to the Metabolic Superiority. J Korean Med Sci. 2010
December; 25(12): 1771–1776. Published online 2010 November 24.
doi:10.3346/jkms.2010.25.12.1771. ^ BMJ Student Archive-Glycosuria and
Ketonuria ^ Ketone Testing-Barbara Davis Center
for Diabetes ^ Measuring Ketones in Urine-Children
With Diabetes ^ a b PTS PANELS™ Ketone Test Strips
Information paper PS-002588E Rev. 2 10/05 by Polymer Technology Systems
^ a b c Converted from molar values, using average of 10.3 g/mol as used in:
PTS PANELS™ Ketone Test Strips Information paper PS-002588E Rev. 2
10/05 by Polymer Technology Systems, and subsequently rounded to same number of
significant figures as molar value ^ a b c Taboulet, P.; Deconinck, N.;
Thurel, A.; Haas, L.; Manamani, J.; Porcher, R.; Schmit, C.; Fontaine, J.;
Gautier, J.. "Correlation between urine ketones and capillary blood ketones in
hyperglycaemic patients". Diabetes & Metabolism 33: 135–139.
doi:10.1016/j.diabet.2006.11.006. PMID 17320448.
^ Sekizawa, A; Sugito, Y; Iwasaki, M; Watanabe, A; Jimbo, M; Hoshi, S; Saito,
H; Okai, T. "Cell-free fetal DNA is increased in plasma of women with
hyperemesis gravidarum". Clinical chemistry 47: 2164–5. PMID 11719487.
[1] ^ Burbos, Nikolaos; Shiner, Alice M.;
Morris, Edward. "Severe metabolic acidosis as a consequence of acute
starvation in pregnancy". Archives of Gynecology and Obstetrics 279: 399–400.
doi:10.1007/s00404-008-0715-3. PMID 18592261.
External links National Institute of Health webpage on
Ketonuria