A comprehensive presentation on glomerular filtration rate (GFR) & renal blood flow and how these entities are impacted by intrinsic and extrinsic regulation. This was presented by the author in the finals of the physiology seminar presentation in medical school.

1. Renal Blood Flow (RBF)
And Its Regulation
AHMAD OZAIR
MBBS 2016
KING GEORGE’S MEDICAL UNIVERSITY, LUCKNOW
1

2. Contents
•Route of blood through kidney
•Features of Renal Blood Flow (RBF)
•Measuring RBF
•Factors affecting RBF
RENAL BLOOD FLOW & ITS REGULATION 2

3. *VALUES FROM GANONG 3
25 % of
Cardiac Output
1.2 L/min *
Low
Arterio-Venous
extraction of O2
High flow for high GFR
-Removal of N2 wastes
-Regulation of body
fluid volumes, pH,
solute concentrations
Image source – Open Textbook, Rice University

4. RBF Hemodynamics
𝑅𝐵𝐹 =
𝑹𝒆𝒏𝒂𝒍 𝑨𝒓𝒕𝒆𝒓𝒚 𝑷𝒓𝒆𝒔𝒔𝒖𝒓𝒆 −𝑹𝒆𝒏𝒂𝒍 𝑽𝒆𝒊𝒏 𝑷𝒓𝒆𝒔𝒔𝒖𝒓𝒆
𝑹𝒆𝒏𝒂𝒍 𝑽𝒂𝒔𝒄𝒖𝒍𝒂𝒓 𝑹𝒆𝒔𝒊𝒔𝒕𝒂𝒏𝒄𝒆
Pressure drop – 100 to 8 mm Hg
Total resistance = sum of all vasculature segments
2 main sources of resistance => sites of regulation
1. Afferent arteriole
2. Efferent arteriole
RENAL BLOOD FLOW & ITS REGULATION 4

5. Measurement of RBF
1. By Radioactive Microspheres
2. By Renal Scintigraphy – Tc labelled DTPA / MAG3
3. By Positron Emission Tomography
4. By PAH Clearance
- Index of RPF
- 𝑅𝐵𝐹 =
𝑹𝑷𝑭
𝟏−𝑯𝒄𝒕
RENAL BLOOD FLOW & ITS REGULATION 5

6. Regulation of RBF
Local regulation – waste removal from blood
◦ Maintain GFR
Systemic regulation –whole body homeostasis
◦ Maintenance fluid volumes & concentrations
RENAL BLOOD FLOW & ITS REGULATION 6

7. Local Regulation  Focus on GFR
All vascular constrictions increase renal vascular
resistance -> decrease RBF
RENAL BLOOD FLOW & ITS REGULATION 7
Factors causing Vasoconstriction
- decrease RBF
• Endothelin (-> Afferent)
• Sympathetic Stimulus
(-> Afferent)
• Angiotensin II (-> Efferent
Mainly)
Factors Causing Vasodilation &
Increasing RBF
Prostaglandins (-> Afferent)
Nitric Oxide & Bradykinin
ANP, BNP, Urodilatin
Clinical Correlates
• ACEi Decrease GFR,
Increase RBF
• NSAID decrease both GFR
& RBF
• ACEi/ARB contraindicated
in Renal Artery Stenosis
(low RBF)

8. Local Regulation -
Arteriolar Myogenic
response
Works in afferent arteriole
Protects glomerulus from
high pressures
RENAL BLOOD FLOW & ITS REGULATION 8

9. Local Regulation => Tubulo-Glomerular Feedback
RENAL BLOOD FLOW & ITS REGULATION
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10. Effectiveness of Autoregulation
RENAL BLOOD FLOW & ITS REGULATION 10
Maintains RBF and
GFR constant
between 80 – 180
mm Hg

11. RBF affected
in BP
regulation
Maintains
Body
Homeostasis
Effect of RAAS
on RBF
Image Source – Berne & Levy, 6th ed

12. Working of Macula Densa
RENAL BLOOD FLOW & ITS REGULATION 12

13. Effect of Blood volume on RBF
Extravascular Volume Depletion  RBF decreases
Increase in ECF Volume  RBF increases
◦ Role in Pregnancy  50% rise in RBF
◦
RENAL BLOOD FLOW & ITS REGULATION 13

14. Bibliography
1. Koeppen BM. Berne and Levy Physiology, 6th edition,
Chapter 32-36, Amsterdam: Elsevier, 2015, pp 557-650
2. Hall JE, Stanton BA. Guyton & Hall’s Textbook of
Medical Physiology, 12th international edition,
Philadelphia: Elsevier Saunders, 2011, pp
RENAL BLOOD FLOW & ITS REGULATION 14

15. Thank You
Did You Know!
Green Ribbon = Kidney Disease Awareness
RENAL BLOOD FLOW & ITS REGULATION 15