Ketonuria is a medical condition in which ketone bodies are present in the

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellular ...

. 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 1 diabetes mellitus Type 1 diabetes (T1D), formerly known as juvenile diabetes, is an autoimmune disease that originates when cells that make insulin (beta cells) are destroyed by the immune system. Insulin is a hormone required for the cells to use blood sugar f ...

. Production of ketone bodies is a normal response to a shortage of

glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...

, meant to provide an alternate source of fuel from

fatty acids In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an B ...

Pathophysiology

Ketones are metabolic end-products of fatty acid metabolism. In healthy individuals, ketones are formed in the

liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...

and are completely metabolized so that only negligible amounts appear in the

. However, when carbohydrates are unavailable or unable to be used as an energy source,

fat In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food. The term often refers specifically to triglycerides (triple est ...

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

, acetoacetate can be tested by a dipstick or by a lab. The results are reported as small, moderate, or large amounts of acetoacetate. A small amount of acetoacetate 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.

Causes

* Metabolic abnormalities such as

diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...

, renal

glycosuria Glycosuria is the excretion of glucose into the urine. Ordinarily, urine contains no glucose because the kidneys are able to reabsorb all of the filtered glucose from the tubular fluid back into the bloodstream. Glycosuria is nearly always caused ...

, or glycogen storage disease. * Dietary conditions such as starvation, fasting,

low-carbohydrate diet Low-carbohydrate diets restrict carbohydrate consumption relative to the average diet. Foods high in carbohydrates (e.g., sugar, bread, pasta) are limited, and replaced with foods containing a higher percentage of fat and protein (e.g., meat, ...

s, prolonged

vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenteri ...

, and

anorexia Anorexia nervosa, often referred to simply as anorexia, is an eating disorder characterized by low weight, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. ''Anorexia'' is a term of Gre ...

including caused by hyperemesis gravidarum. * Conditions in which metabolism is increased, such as

hyperthyroidism Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidis ...

, fever, pregnancy or

lactation Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process naturally occurs with all sexually mature female mammals, although it may predate mammals. The proces ...

. 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.

Diagnosis

A wide variety of companies manufacture ketone screening strips. A strip consists of a thin piece of plastic film slightly larger than a

matchstick A match is a tool for starting a fire. Typically, matches are made of small wooden sticks or stiff paper. One end is coated with a material that can be ignited by friction generated by striking the match against a suitable surface. Wooden matc ...

, 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 (it is recommended to use a stopwatch to time this exactly and disregard any resultant colour change after the specified 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. In severe diabetic ketoacidosis, the dipstix reaction based on sodium

nitroprusside Sodium nitroprusside (SNP), sold under the brand name Nitropress among others, is a medication used to lower blood pressure. This may be done if the blood pressure is very high and resulting in symptoms, in certain types of heart failure, and ...

may underestimate the level of ketone bodies in the blood. It is sensitive to acetoacetate only, and the ratio of beta-hydroxybutyric to acetoacetate is shifted from a normal value of around 1:1 up to around 10:1 under severely ketoacetotic conditions, due to a changing redox milieu in the liver. Measuring acetoacetate alone will thus underestimate the accompanying beta-hydroxybutyrate if the standard conversion factor is applied.

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;BMJ Student Archive-Glycosuria and Ketonuria
/ref> therefore, urine ketone measurement is especially helpful in emergency situations.

References

External links

National Institute of Health (NIH) webpage on Ketonuria
{{Abnormal clinical and laboratory findings for urine Abnormal clinical and laboratory findings for urine