Investigation of Non-Protein Nitrogen Compounds

Question 1

What is the main source of ammonia in the body?

Answer 1

Protein catabolism (deamination of amino acids).

Question 2

How is ammonia eliminated?

Answer 2

Converted into urea in the liver and excreted by the kidneys.

Question 3

What enzyme is responsible for the first step of the urea cycle?

Answer 3

Carbamoyl Phosphate Synthetase I (CPS I).

Question 4

What is the most common sample type for ammonia measurement?

Answer 4

Plasma (collected in EDTA or lithium heparinate tubes).

Question 5

What precautions should be taken when collecting ammonia samples?

Answer 5

Transport on ice, process immediately to avoid false elevation.

Question 6

What are the main methods for measuring ammonia?

Answer 6

Colorimetric (Berthelot reaction), Enzymatic, and Electrochemical methods.

Question 7

What is the normal range of ammonia in blood?

Answer 7

14 – 38 µmol/L.

Question 8

What is the normal range of ammonia in urine?

Answer 8

30 – 60 mmol/24h.

Question 9

What are the causes of hyperammonemia?

Answer 9

Liver failure (cirrhosis, hepatitis), Urea cycle disorders, Organic acidemias, Metabolic acidosis.

Question 10

What clinical symptoms suggest hyperammonemia?

Answer 10

Confusion, tremors, encephalopathy, vomiting, seizures, coma.

Question 11

A neonate has hyperammonemia, vomiting, and lethargy. What is the likely diagnosis?

Answer 11

Urea cycle disorder (OCT or CPS deficiency).

Question 12

Why should patients avoid smoking before ammonia testing?

Answer 12

Smoking increases plasma ammonia levels.

Question 13

What test can confirm a urea cycle disorder?

Answer 13

Measurement of urea cycle enzyme activity and blood amino acid chromatography.

Question 14

Why is ammonia measured in hepatic encephalopathy?

Answer 14

High ammonia levels correlate with neurological deterioration.

Question 15

How is hyperammonemia treated?

Answer 15

Lactulose, low-protein diet, sodium benzoate, arginine supplementation.

Question 16

What is the main function of urea?

Answer 16

Excretion of nitrogenous waste via urine.

Question 17

Where is urea synthesized?

Answer 17

Liver (urea cycle).

Question 18

How is urea eliminated?

Answer 18

Filtered by the kidneys, partially reabsorbed, and excreted in urine.

Question 19

What is the most common sample type for urea measurement?

Answer 19

Serum or heparinized plasma.

Question 20

What are the main methods for measuring urea?

Answer 20

Enzymatic (urease-based), Colorimetric (Berthelot reaction), and Electrochemical techniques.

Question 21

What is the normal range of urea in blood?

Answer 21

0.15 – 0.45 g/L.

Question 22

What is the normal range of urea in urine?

Answer 22

18 – 30 g/day.

Question 23

What conditions cause hypoazotemia (low urea)?

Answer 23

Liver failure, malnutrition, pregnancy.

Question 24

What conditions cause hyperazotemia (high urea)?

Answer 24

Kidney disease, dehydration, high protein intake, infections.

Question 25

A patient has high urea but normal creatinine. What does this indicate?

Answer 25

Dehydration.

Question 26

What is the most common clinical use of urea measurement?

Answer 26

Assessing kidney function.

Question 27

A diabetic patient has high urea and creatinine. What is the likely diagnosis?

Answer 27

Diabetic nephropathy.

Question 28

Why is urea not a perfect marker of kidney function?

Answer 28

It is influenced by diet, hydration, and catabolic states.

Question 29

What test is better than urea for kidney function assessment?

Answer 29

Serum creatinine and eGFR (estimated glomerular filtration rate).

Question 30

How does liver failure affect urea levels?

Answer 30

Decreases urea production (hypoazotemia).

Question 31

What is creatinine?

Answer 31

A waste product of muscle metabolism (from creatine breakdown).

Question 32

How is creatinine excreted?

Answer 32

Filtered by the kidneys and excreted in urine.

Question 33

What is the most common sample type for creatinine measurement?

Answer 33

Serum or heparinized plasma.

Question 34

What is the gold standard method for creatinine measurement?

Answer 34

IDMS (Isotope Dilution Mass Spectrometry).

Question 35

What is the normal range of creatinine in blood?

Answer 35

Men: 6–12 mg/L, Women: 5–10 mg/L, Children: 4–9 mg/L.

Question 36

What is the normal range of creatinine in urine?

Answer 36

1–2 g/day.

Question 37

What are the causes of hypercreatininemia?

Answer 37

Acute & chronic renal failure, dehydration, muscle disease.

Question 38

A 60-year-old diabetic has high creatinine, high urea, and proteinuria. What is the likely diagnosis?

Answer 38

Chronic kidney disease (CKD).

Question 39

How is eGFR calculated?

Answer 39

Using formulas like MDRD, CKD-EPI, or Cockcroft-Gault.

Question 40

What is the difference between creatine and creatinine?

Answer 40

Creatine stores energy in muscles; creatinine is its waste product.

Question 41

What are the three main types of jaundice?

Answer 41

Pre-hepatic, Hepatic, Post-hepatic.

Question 42

What is the normal range of total bilirubin in adults?

Answer 42

6 – 10 mg/L.

Question 43

What condition causes isolated unconjugated hyperbilirubinemia?

Answer 43

Gilbert’s syndrome.

Question 44

What enzyme deficiency causes Crigler-Najjar syndrome?

Answer 44

Glucuronosyltransferase deficiency.

Question 45

What type of jaundice is seen in biliary obstruction?

Answer 45

Post-hepatic (cholestatic) jaundice.

Question 46

What is the main cause of pre-hepatic jaundice?

Answer 46

Excessive hemolysis (e.g., hemolytic anemia, sickle cell disease).

Question 47

What is the enzyme responsible for bilirubin conjugation in the liver?

Answer 47

UDP-glucuronosyltransferase (UGT).

Question 48

How does intrahepatic cholestasis affect bilirubin levels?

Answer 48

Both conjugated and unconjugated bilirubin increase.

Question 49

A patient has pale stools and dark urine. What type of jaundice is most likely?

Answer 49

Post-hepatic (obstructive) jaundice due to bile duct obstruction.

Question 50

Why should bilirubin samples be protected from light?

Answer 50

Light degrades bilirubin, leading to falsely low results.

Question 51

What type of jaundice occurs in newborns due to immature liver enzymes?

Answer 51

Physiological jaundice.

Question 52

What condition causes conjugated hyperbilirubinemia with black liver pigmentation?

Answer 52

Dubin-Johnson syndrome.

Question 53

What is the most common method for measuring bilirubin?

Answer 53

Diazo reaction (Van den Bergh method).

Question 54

A patient with liver failure, ascites, and jaundice has high conjugated bilirubin. What is the diagnosis?

Answer 54

Hepatic jaundice due to liver cirrhosis.

Question 55

What genetic disorder leads to isolated unconjugated hyperbilirubinemia with no hemolysis?

Answer 55

Gilbert’s syndrome.