HealthFlex
×
  • Home
  • Immunology Book
  • Lab Tests
    • Hematology
    • Fluid analysis
    • CSF
    • Urine Analysis
    • Chemical pathology
    • Blood banking
    • Fungi
    • General pathology
    • Immune system
    • Microbiology
    • Parasitology
    • Pathology
    • Tumor marker
    • Virology
    • Cytology
  • Lectures
    • Bacteriology
    • Liver
    • Lymph node
    • Mycology
    • Virology
  • Blog
    • Economics and technical
    • Fitness health
    • Mental health
    • Nutrition
    • Travel
    • Preventive health
    • Nature and photos
    • General topic
  • Medical Dictionary
  • About Us
  • Contact

Renal Functions:- Part 1 – Renal Functions and Renal parameters

March 21, 2023Chemical pathologyLab Tests

Table of Contents

  • Renal Functions
      • Sample for Renal Function Tests
      • Precautions for Renal Function Tests
      • Purpose of the tests (Indications) for Renal Function Tests
    • Pathophysiology of Renal Functions
      • Nephron structure:
      • The proximal tubules:
      • The Distal tubules:
      • The Loop of Henle is:
      • The collecting system:
      • Excretory function:
      • Regulatory function:
      • Water homeostasis:
      • Endocrine Function:
      • Glomerular filtration rate (GFR):
      • Urine:
    • Routine Renal Function tests are:
      • Normal renal function tests
        • Urea nitrogen (Urea N) Concentration:
        • Creatinine Concentration:
      • Normal renal functions tests  are:
      • Table showing the severity of renal failure:
      • Questions and answers:

Renal Functions

Sample for Renal Function Tests

  1. These tests are done on the serum or plasma of the patient.
  2. A urine sample may also be needed.
  3. The specimen is stable for several days at 4 to 6 °C and for at least 2 to 3 months when frozen.
  4. The creatinine sample is stable when refrigerated for 24 hours.

Precautions for Renal Function Tests

  1. Avoid a high concentration of Na fluoride as this inhibits urease.
  2. Discontinue Vitamin B12 supplements at least 72 hours before sampling.

Purpose of the tests (Indications) for Renal Function Tests

  1. These tests diagnose any renal disease.
  2. These tests can tell the prognosis of the patient.
  3. It can assess the remaining functional capacity of the kidneys.

Pathophysiology of Renal Functions

  1. Kidneys play an important role in the homeostatic system of the body.
  2. The kidney is the highly specialized organ in the body for:
    1.  Elimination of the waste products of metabolism.
    2. It preserves the internal environment of the cells. That is it maintains the pH, water balance, ionic equilibrium, and fluid osmotic pressure.
    3. The impairment of renal function correlates with morbidity and mortality.

Nephron structure:

  1. This is the functional unit of the kidney.
  2. Each kidney contains 400,000 to 800,000 nephrons.
  3. Each nephron consists of the following:
    1. Glomerulus.
    2. Proximal Tubule.
    3. The loop of Henle.
    4. Distal Tubule.
    5. Collecting ducts.
Renal Function Tests: Kidney nephron structure

Renal Function Tests: Kidney nephron structure

  1. Kidneys’ biological functions are:
    1. Excretion.
    2. Homeostatic regulation.
    3. Endocrine function.
    4. Urine formation.
Renal Function Tests: kidney functions

Renal Function Tests: kidney functions

The proximal tubules:

These are most metabolically active and lead to the reabsorption of :

  1. 60 to 90% of the glomerular filtrate.
  2. 70% of the Na and Cl.
  3. Other substances are potassium, glucose, bicarbonate, phosphate, and sulfate.
  4. 90% of H+ is excreted.
Renal function tests: Kidney's Proximal tubules functions

Renal function tests: Kidney’s Proximal tubules functions

The Distal tubules:

  1. These are involved in the excretion and secretion of :
    1. ADH and aldosterone help in reabsorption.
    2. K+ is secreted in response to aldosterone.
    3. Sodium, Potassium.
    4. Chloride and hydrogen.
    5. H+, ammonia, urea, and uric acid were secreted, and bicarbonate was reabsorbed.
Renal function tests: Kidney's distal tubules functions

Renal function tests: Kidney’s distal tubules functions

The Loop of Henle is:

  1. Selectively permeable to sodium, urea, and water.
  2. The descending loop is highly permeable to water but not salt.
  3. Urine becomes concentrated.
  4. The ascending loop is impermeable to water but actively reabsorbs salts, decreasing the concentration of the urine.
Renal function tests: Function of Loop of Henle

Renal function tests: Function of Loop of Henle

The collecting system:

  1. This is under the control of ADH.
    1. Aldosterone regulates NaCl reabsorption.
    2. K+, H+, and ammonia are reabsorbed.
    3. Urine formed is carried to the ureter and the urinary bladder.
Renal function tests: Function of collecting system

Renal function tests: Function of collecting system

Excretory function:

  1. This  helps the body to get rid of the following:
    1. The end product of metabolism.
    2. Excess of inorganic substances digested in the diet.
    3. There is the removal of the waste products of metabolism like urea, creatinine, uric acid, and amino acids.
    4. The removal of the inorganic substances ingested in the diet like sodium, potassium, chloride, calcium, phosphate,
    5. magnesium, bicarbonate, and sulfate.
    6. The kidney also removes foreign heavy metals, drugs, and antibiotics.

Regulatory function:

  1. This is a complex system of control in which intrarenal and extrarenal humoral factors are involved.
  2. Electrolyte homeostasis takes place predominantly in the proximal collecting tubules.
    1. Where roughly 70% of the sodium, chloride, and water of ultrafiltrate is reabsorbed.
    2. Other solutes are bicarbonate, phosphate, calcium, and potassium.

Water homeostasis:

  1. Water is reabsorbed in:
    1. Roughly 70% in the proximal tubule.
    2. 5% in the loop of Henle.
    3. 10% in the distal tubule.
    4. Rest in the collecting ducts.

Endocrine Function:

  1. The kidney synthesizes hormones and also is the target organ for other site-formed hormones.
  2. The kidney is the site of degradation of hormone-like insulin and aldosterone.
  3. The kidney produces hormones like:
    1. Erythropoietin stimulates RBC production.
    2. Renin.
    3. Prostaglandins.
    4. Thromboxane.
    5. Vit. D. It converts 25-hydroxyvitamin D3 to form the biologically active vitamin D.

Glomerular filtration rate (GFR):

  1. This is the quantity of blood cleared of substances like creatinine and urea per unit of time.
  2. Substances like creatinine and urea filter through the kidney glomeruli at the rate of milliliters (mL) per minute.
Glomerular filtration rate formula

Glomerular filtration rate formula

  1. GFR depends upon the following:
    1. Plasma concentration of the substance.
    2. The excretion rate of the kidney will reflect the following:
      1. Renal plasma flow.
      2. Glomerular filtration rate.
    3. This substance used should not be reabsorbed, secreted, synthesized, or degraded in the nephron.
  2. GFR is the most reliable measure of kidney function.
    1. GFR may be measured by giving exogenous substances like Inulin clearance.
    2. GFR may be measured by endogenous substances like creatinine and urea nitrogen.

Urine:

  1. This is a fluid excreted by the kidneys.
  2. It is stored in the urinary bladder and discharged through the urethra.
  3. Normal urine is sterile, clear, and amber in color.
    1. It is slightly acidic and has a characteristic odor.
    2. Urine contains dissolved compounds, cells, and crystals.
  4. Urine in a healthy person is clear, with pH 5 to 6, and has an average specific gravity of 1.024.
  5. The normal urine output per day is 500 mL.
  6. Urinary output is described as :
    1. Anuria < 100 ml/day.
    2. Oliguria < 400 ml/day.
    3. Polyuria > 2 L/day.

Routine Renal Function tests are:

  1. BUN or blood urea.
  2. Creatinine.
  3. Calcium.
  4. Magnesium.
  5. Phosphorus.
  6. Albumin.
  7. Total protein.
  8. Electrolytes (Sodium and Potassium).
  9. Chloride in urine and blood.
  10. Creatinine clearance.
  11. Creatinine, 24- hours urine.
  12. Protein in the urine (24 hours urine sample is needed).
  13. Microalbuminuria.
  14. Urine analysis.
  15. GFR.

Normal renal function tests

Source 1

Urea nitrogen (Urea N) Concentration:

Age mg/dL
Cord 21 to 40
Premature (One week) 3 to 25
<1 year 4 to 19
Infants/child 5 to 18
18 to 60 years 6 to 20
60 to 90 years 8 to 23
>90 years 10 to 31

Creatinine Concentration:

Age mg/dL
Cord blood 0.6 to 1.2
Newborn 1 to 4 days 0.3 to 1.0
Infants 0.2 to 0.4
Child 0.3 to 0.7
Adolescent 0.5 to 1.0
18 to 60 years
Male 0.9 to 1.3
Female 0.6 to 1.1
60 to 90 years
Male 0.8 to 1.3
Female 0.6 to 1.2
>90 years
Male 1.0 to 1.7
Female 0.6 to 1.3

Other sources

  • Urea
    • 5 to 39 mg/dL.
  • BUN
    • 7 to 18 mg/dL.
  • Creatinine
    • Male = 0.9 to 1.5 mg/dL.

Female = 0.7 to 1.3 mg/dL.

Normal renal functions tests  are:

Renal parameter Normal range
  • Specific gravity
  1. Concentration = >1.025
  2. Dilution = <1.003
  • PSP excretion (phenosulfonaphthalein)
  1. >25% in urine in 15 minutes
  2. 55 to 75% in 2 hours
  • Glomerular filtration rate
  1. Endogenous creatinine = 90 to 130 mL/minutes
  2. Inulin = male = 110 to 150/minutes  Female = 105 to 132 mL/minutes
  3. Urea = Maximum = 60 to 100 mL/minutes   Standard = 40 to 65 mL/minutes

Table showing the severity of renal failure:

The degree of renal failure  GFR mL/min  Creatinine mg/dL  Clinical presentation
Mild 30 to 50 1.9 Hypertension
Moderate 10 to 30 4.0 Anemia
Severe < 10 8.0 Anemia
End-stage < 5 16.9 acidosis, hyperkalemia, coma, and death
  • Note These tests in detail are described under their names. Please see part 2 of the renal function test.

Questions and answers:

Question 1: What are the biological functions of the kidney?
Show answer
Kidney's biological functions are excretion, homeostatic regulation, endocrine function, and urine formation.
Question 2: What is anuria?
Show answer
When the kidneys produce <100 mL of urine/24 hours.

Possible References Used
Go Back to Chemical pathology

Comments

Vedprakash verma Reply
March 14, 2020

Write

Dr. Riaz Reply
March 15, 2020

Please elaborate on your comment. But still thanks.

Shahrukh tausif Reply
April 16, 2020

Very nice blog…..i am a final year student from kolkata,india….
Sir, i appreciate your hardwork…..your blog is very short , crisp, to the point

Dr. Riaz Reply
April 16, 2020

Thanks for the comments. I am updating the various topics. I will try to make the Renal function parameter better.

Meghan W Reply
September 3, 2020

Presentation is very succinct and informative and is helping me understand and study tremendously. thank you for putting this out there.

Dr. Riaz Reply
September 3, 2020

Thanks for the comments.

Ramanayake Reply
November 22, 2020

Thanks very much
For sacrifice devoted and dedicated your valuable time

Dr. Riaz Reply
November 23, 2020

Thanks a lot.

SR Raw lab technician Reply
August 4, 2021

Very nice bosss….. Your Article very easy and shorts thank you so muchhh

Dr. Riaz Reply
August 4, 2021

Thanks a lot for the encouraging remarks.

Tharindu Dhananjaya Reply
October 1, 2021

This is a very good source for medical students to come and take a quick look at a topic. With concise and easy to understand format

Dr. Riaz Reply
October 1, 2021

Thanks a lot.

Getachew Reply
March 21, 2023

thanks alot

Dr. Riaz Reply
March 21, 2023

Welcome.

Add Comment Cancel


  • Lab Tests
    • Blood banking
    • Chemical pathology
    • CSF
    • Cytology
    • Fluid analysis
    • Fungi
    • General pathology
    • Hematology
    • Immune system
    • Microbiology
    • Parasitology
    • Pathology
    • Tumor marker
    • Urine Analysis
    • Virology

About Us

Labpedia.net is non-profit health information resource. All informations are useful for doctors, lab technicians, nurses, and paramedical staff. All the tests include details about the sampling, normal values, precautions, pathophysiology, and interpretation.

[email protected]

Quick Links

  • Blog
  • About Us
  • Contact
  • Disclaimer

Our Team

Professor Dr. Riaz Ahmad Bhutta

Dr. Naheed Afroz Syed

Dr. Asad Ahmad, M.D.

Dr. Shehpar Khan, M.D.

Copyright © 2014 - 2023. All Rights Reserved.
Web development by Farhan Ahmad.