Urine for ketones, and Ketone Bodies (Ketonuria)

Sample

1. This is done in the urine.
2. This test can also be done on blood (serum or plasma).

Precautions

1. Keep the urine refrigerated and in closed containers.
2. Avoid loss due to evaporation and bacterial action.
3. Keep the blood also refrigerated.
4. Some of the drugs give false-positive result e.g.
   1. Phenothiazine.
   2. Ether and chloroform.
   3. Metformin.
   4. Captopril.
   5. Insulin.
   6. Levodopa.
   7. Penicillamine.
   8. Isopropyl alcohol.
   9. Valproic acid.
   10. Aminosalicylic acid.
5. The false-negative result seen in:
   1. When urine is kept at room temperature for a long time due to the loss of ketones in the air.
   2. Aspirin.
   3. Phenazopyridine.

Indications

1. It is advised in diabetic patients for the early diagnosis of ketoacidosis.
   1. Ketones are done to judge the severity of the acidosis and monitor the response to the treatment.
2. Testing of ketonuria in diabetetics:
   1. To evaluate the diabetic patient in a coma.
   2. To monitor people with diabetes who are on oral hypoglycemic drugs.
   3. Check when the patient is switched from the insulin to oral hypoglycemics; ketonuria’s appearance within 24 hours of the insulin withdrawal indicates a poor response to oral hypoglycemic drugs.
   4. Testing of the ketonuria is important In patients who have urine sugar positive and raised blood glucose.
   5. Ketonuria is done to differentiate between diabetic coma with positive ketones and insulin-shock negative ketonuria.
3. This is done by screening the ketonuria, which is usually seen in hospitalized patients, children, pregnant ladies, and patients with diabetes.
   1. During pregnancy, early detection of ketonuria is essential because ketoacidosis may lead to the fetus’s death.
4. It is done to judge the severity of the acidosis and the treatment response.
   1. The ketonuria may provide a more accurate indicator of acidosis than blood testing.
   2. This is helpful in the emergency wards.

Definition

• Increased ketone bodies in the blood are called Ketonemia.
• Increased excretion in the urine is called Ketonuria.

Pathophysiology

1. Fat metabolism, when completely metabolized, leads to CO 2 and H2O formation. So ketone bodies are not seen in the urine.
   1. While intermediate products are ketone bodies.

2. Ketone bodies are seen in:
   2. In the case of decreased availability of carbohydrates like starvation or frequent vomiting.
   3. Another possibility is decreased utilization of carbohydrates like diabetes mellitus and glycogen storage disease.
   4. High fat and low carbohydrates diet are ketogenic and increase ketone bodies in the blood.
3. Ketones are the end product of fatty acid metabolism.
   

   Ketone bodies formation

4. Ketones are formed when glucose as a source of energy is not present.

5. This situation happens when there is no insulin, so glucose cannot enter the cells.
   1. In that case, ketone bodies are the energy source for the body, particularly to the brain.
   2. In fasting for 3 to 4 days, then 30 to 40% of body energy is provided by the ketone bodies.

6. Ketones bodies are the end product of fatty acid breakdown and consists of :
   1. Beta-hydroxybutyric acid.
   2. Acetoacetic acid.
   3. Acetone.
      1. The β- hydroxybutyric acid + acetoacetic acid readily converts to acetone.
      2. It shows that the main ketone is acetone to be tested.
      3. Some of the kits only measure acetoacetic acid.

7. In the blood:
   1. Acetone is a minor amount.
   2. Acetoacetate and β- hydroxybutyrate is equal in amount and are the main ketone bodies.
8. In a healthy person, ketones are formed in the liver, completely metabolized, but there is a negligible amount in urine.

The outcome of Increased Ketones in the blood leads to :

7. 1. Electrolyte imbalance.
   2. Dehydration.
   3. If not corrected, then it leads to acidosis, coma, and ultimately death.
8. Ketones are present in the urine when a threshold level of ketones exceeds the blood’s normal level.
   

   ketone bodies result

Clinical significance of ketone bodies:

1. 1. Insulin dosage for monitoring and management of insulin-dependent diabetes mellitus, type 1 diabetes.
      1. Ketonuria shows insulin deficiency and needs to adjust the dose of insulin.
      2. This is the early sign of an insufficient dose of insulin.
   2. Diabetic acidosis (Inability to metabolize carbohydrate).
   3. Vomiting (increased loss of carbohydrate).
   4. Starvation (inadequate carbohydrate intake).
   5. Malabsorption  (inadequate carbohydrate intake).
   6. Pancreatic diseases.
   7. Inborn error of amino acid metabolism.
   8. Ketonuria shows a deficiency of insulin and indicates the regulation of insulin dose.
   9. Strenuous exercise leads to ketonuria due to the overuse of the carbohydrate.

Normal

• In Urine
  • Ketone bodies are negative.
  • Small amount = < 20 mg/dL.
  • Moderate amount = 30 to 40 mg/dL.
  • Large amount = > 80 mg /dL.
• In blood or plasma.
  • Acetone = < 2.0 mg/dL (<0.34 mmol/L).
  • Acetoacetate = < 1 mg/dL (<0.1 mmol/L).
  • β-hydroxybutyric acid = 0.21 to 2.81 mg/dL (20 to 270 µmol/L).

Source 1

• Urine
  • Acetoacetate = Negative.
  •  Acetone         = 0.3 mg/dL (0.05 mmol/L).
  • β-hydroxybutyric acid = Negative
• Serum or plasma
  • Acetone
    • Ketoacidosis = 10 to 70 mg/dL (1.72 to 12.04 mmol/L)
    • Occupational exposure = <10 mg/dL (<1.72 mmol/L)
    • Toxic concentration = >20 mg/dL  (>3.44 mmol/L)
  • Acetoacetate     =   Negative  <1 mg/dL (<0.1 mmol/L)
  • β-hydroxybutyric acid = 0.21 to 2.81 mg/dL (20 to 270 µmol/L)

Diagnostic test

1. Various types of strips are available to dectect the ketone bodies.
2. Gerhardt’s Ferric chloride reacts only with Acetoacetate. This is an indirect method to detect the β- hydroxybutyrate in the urine.
3. Nitroprusside has 10 times more sensitive to acetoacetate than acetone.
   1. Acetoacetate (acetone) + sodium nitroprusside + glycine  →  purple color
   2. There is no reaction with β- hydroxybutyrate.
   3. It is reported as:
      1. Negative.
      2. Moderate.
      3. Large amount  OR as
      4. 1⁺, 2⁺, 3⁺.
4. There are strips to detect β- hydroxybutyrate in the serum and urine are available.
5. Quantitative estimation of β- hydroxybutyrate in serum or blood kits are commercially available.
   Comparison of the various test strips for the detection of ketone bodies:

   Type of the test strip	Specificity	Sensitivity
   Acetest	Acetoacetic acid Acetone	5 to 10 mg/dL 20 to 25 mg/dL
   Chemstrip	Acetoacetic acid Acetone	9 mg/dL 70m mg/dL
   Multistix	Acetoacetic acid	5 to 10 mg/dL
   Ketostix	Acetoacetic acid	5 to 10 mg/dL

Ketone bodies are seen in:

1. Diabetic patients.
2. Starvation.
3. Fasting.
4. High protein diet.
5. Alcoholism.
6. Salicylates poisoning.
7. Isopropanol intake.
8. Acute febrile illness (especially in infants and children).
9. Renal Glycosuria.
10. Glycogen storage disease (Von Gierke’s disease).
11. Anorexia.
12. Low carbohydrate diet.
13. Pregnancy or lactation.
14. Eclampsia.
15. Fever.
16. Hyperthyroidism.
17. Prolonged vomiting and diarrhea.
18. Patients in the hospital may have ketonuria—roughly 15% show ketonuria in hospitalized patients without diabetes.
19. Ketonuria may develop after anesthesia with ether and chloroform.
20. Children are more prone to develop ketonuria and ketosis.

The critical value of the ketonuria:

1. When ketonuria is positive, clinical action should be taken, and don’t take it lightly.
2. Ketonuria positive in infants <2 years of age is a serious and critical alert.
3. In diabetic patients, ketonuria positive means that diabetes is well controlled.
4. In non-diabetics, it suggests increased Fat intake and fewer carbohydrates.
   

   Normal urine picture:

   Physical features	Chemical features	Microscopic findings
   Color = Pale yellow or amber Appearance = Clear to slightly hazy pH = 4.5 to 8.0 Specific gravity = 1.015 to 1.025	Blood = Negative Glucose = Negative Ketones= Negative Protein = Negative Bilirubin = Negative Urobilinogen = Negative (±) Leucocyte esterase = Negative Nitrite for bacteria = Negative	RBCs = Rare or Negative WBC = Rare or Negative Epithelial cells = Few Cast = Negative (Occasional hyaline) Crystal = Negative (Depends upon the pH of the urine) Bacteria = Negative

    

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