Clinical Pathology: Kidney Function

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Questions and Answers

What is the primary function of the kidneys in the body?

To store nutrients

To produce hormones

To regulate body temperature

To regulate the internal environment of the body (correct)

What is the term used to describe nitrogen-containing components of serum or plasma that are not associated with protein?

Free nitrogen

Nonprotein nitrogen (correct)

Protein nitrogen

Nitrogen waste

What is the primary location where urea is formed in the body?

Liver (correct)

Pancreas

Kidneys

Spleen

What is the purpose of estimating non-protein nitrogen level in the blood?

To diagnose kidney disease Signup and view all the answers

What is the role of the kidneys in regulating the body's internal environment?

All of the above Signup and view all the answers

What is included in the group of nonprotein nitrogen substances?

Urea, creatinine, creatine, uric acid, ammonia, amino acids, and undetermined nitrogen Signup and view all the answers

What is the function of urea in the body?

To have a possible mild diuretic action Signup and view all the answers

What is included in the renal function tests?

Urine specific gravity, estimation of non-protein nitrogen, studies of the ability of the kidney to excrete certain dyes, and tests based on clearance concept Signup and view all the answers

What is the primary function of urease enzyme in Nesslerization method?

To release ammonia Signup and view all the answers

What is the normal range of BUN concentration in blood?

Less than 35 mg/dl Signup and view all the answers

What is the primary source of creatinine in the body?

Muscle metabolism Signup and view all the answers

What is the effect of diet on creatinine concentration?

It has no influence Signup and view all the answers

What is the recommended method for determining serum creatinine levels?

Lloyd's reagent method Signup and view all the answers

What is the effect of abnormal glomerular filtration rate on serum creatinine concentration?

It increases serum creatinine concentration Signup and view all the answers

What is the correlation between BUN concentration and renal function impairment?

Direct correlation Signup and view all the answers

What is the similarity between BUN and creatinine concentration interpretations?

They have similar interpretations Signup and view all the answers

What percentage of filtered urea is reabsorbed as it passes through the tubules?

25-40% Signup and view all the answers

What is the indication for Blood Urea Nitrogen Testing when decreased kidney function is suspected?

Whenever decreased kidney function is suspected Signup and view all the answers

Which of the following anticoagulants should be avoided in Blood Urea Nitrogen testing?

Anticoagulants containing nitrogen Signup and view all the answers

Which technique is used to estimate blood urea nitrogen concentration?

Chromatography Signup and view all the answers

What is the advantage of the Chromatography technique?

It is simple and requires a small amount of serum or plasma Signup and view all the answers

What is the principle of the Chromatography technique?

The chromatography paper is banded with different reagents and the serum passes through a series of chemical reactions Signup and view all the answers

What is the purpose of adding mercuric chloride in the Mercury combining power technique?

To combine with nonprotein nitrogen substances in the filtrate Signup and view all the answers

What is the result of the reaction between mercuric chloride and the test reagent sodium carbonate?

A reddish brown precipitate Signup and view all the answers

Study Notes

Kidney Function

The kidneys regulate the internal environment of the body through various functions, including:
- Eliminating excess water and inorganic elements
- Removing nonvolatile end products of metabolic activity
- Retaining essential substances for normal bodily functions
- Eliminating foreign toxic elements
- Forming and excreting substances like hydrogen ions and ammonia

Renal Function Tests

These tests assess kidney function and include:
- Urine specific gravity and water deprivation tests
- Estimation of non-protein nitrogen levels in the blood
- Studies on the ability of the kidney to excrete certain dyes
- Clearance concept tests
- Other blood chemistry determinations (e.g., serum amylase, electrolytes, blood pH, cholesterol, and serum proteins)

Non-Protein Nitrogen Levels in Blood

Non-protein nitrogen (NPN) refers to nitrogen-containing components in serum or plasma not associated with protein
NPN includes:
- Urea, creatinine, creatine, uric acid, ammonia, amino acids, and "undetermined nitrogen"
NPN represents products of intermediary metabolism from both tissue and ingested protein

Blood Urea Nitrogen (BUN)

Urea is the principal end product of protein catabolism, formed in the liver and excreted primarily by the kidneys
Approximately 25-40% of filtered urea is reabsorbed in the tubules
Indications for BUN testing:
- Suspected decreased kidney function
- Measuring peripheral perfusion of tissues in animals with hypovolemic shock or decreased blood pressure
- Routine presurgical laboratory screening

Technique of BUN Tests

BUN determinations are usually conducted on whole blood, plasma, or serum
Anticoagulants containing nitrogen must be avoided; EDTA, heparin, sodium citrate, and sodium oxalate are acceptable
Various laboratory techniques are used to estimate BUN concentration, including:
- Chromatography
- Mercury combining power
- Nesslerization
- Determination of Urease enzyme

Chromatography Technique

Advantages:
- Simplicity
- No special chemicals required
- Small amount of serum or plasma needed
Principle of the test:
- Chromatography paper is banded with different reagents, which react with the serum to produce a color change, indicating urea nitrogen concentrations

Interpretations of BUN Results

If BUN concentration exceeds 35-45 mg/dl, glomerular filtration rate (GFR) is diminished
Abnormal BUN concentrations may be caused by prerenal, primary renal, or postrenal factors
Correlation can be made between the degree of BUN elevation and the severity of renal function impairment

Creatinine

Creatinine is a nonprotein nitrogen substance formed during muscle metabolism of creatine and phosphocreatin
It is excreted by glomerular filtration and provides an index of glomerular filtration
Factors influencing creatinine concentration are similar to those for BUN, except:
- Creatinine is not influenced by diet
- Daily production of creatinine from muscle metabolism is relatively constant
- Creatinine production is not easily influenced by catabolic factors affecting urea formation

Interpretations of Creatinine Concentration

Similar to BUN interpretations, with elevations indicating decreased GFR and potential renal function impairment

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Description

This quiz covers the functions of the kidneys in regulating the internal environment of the body, including elimination of excess water and waste products, retention of essential substances, and more.