CHBT Study Guide — 300 Q&A
CERTIFIED HEMODIALYSIS BIO-MEDICAL TECHNICIAN COMPLETE
EXAM QUESTIONS AND CORRECT ANSWERS
1: ANATOMY & PHYSIOLOGY OF THE KIDNEY
Q1. What is the primary function of the kidneys?
Answer: The primary function of the kidneys is to filter blood, remove
waste products and excess fluids, regulate electrolyte balance,
maintain blood pressure, and produce urine.
Q2. How many nephrons are present in each kidney?
Answer: Each kidney contains approximately 1 to 1.5 million nephrons,
which are the functional units responsible for filtering blood and
producing urine.
Q3. What is the glomerular filtration rate (GFR) and what is the
normal value?
Answer: GFR is the volume of fluid filtered per unit time from the
plasma flowing through the glomeruli. Normal GFR is approximately
90–125 mL/min (or ~180 L/day).
Q4. Name the three layers of the glomerular filtration barrier.
Answer: The three layers are: (1) the fenestrated endothelium of the
capillary wall, (2) the glomerular basement membrane (GBM), and (3)
the podocyte layer (visceral epithelium) with filtration slits.
Q5. What is the role of the tubuloglomerular feedback mechanism?
Answer: Tubuloglomerular feedback regulates blood flow and filtration
rate in the kidney by sensing NaCl concentration at the macula densa
in the distal tubule, causing vasoconstriction or dilation of the afferent
arteriole.
Q6. What percentage of filtered water is reabsorbed in the proximal
convoluted tubule (PCT)?
Answer: Approximately 65–80% of filtered water is reabsorbed in the
PCT via osmotic reabsorption that follows solute reabsorption.
Q7. What is the role of aldosterone in the kidney?
Certified Hemodialysis Bio-Medical Technician (CHBT) — Examination Preparation Study Guide
, CHBT Study Guide — 300 Q&A
Answer: Aldosterone is a mineralocorticoid that increases sodium
reabsorption in the collecting duct and distal tubule, thereby increasing
water retention and blood pressure.
Q8. Describe the renin-angiotensin-aldosterone system (RAAS).
Answer: RAAS: Decreased renal perfusion stimulates juxtaglomerular
cells to release renin, which converts angiotensinogen to angiotensin I.
ACE then converts it to angiotensin II, a vasoconstrictor that also
stimulates aldosterone secretion from the adrenal cortex.
Q9. What structures make up the juxtaglomerular apparatus?
Answer: The juxtaglomerular apparatus consists of: (1)
juxtaglomerular (granular) cells in the afferent arteriole wall, (2) macula
densa in the distal convoluted tubule, and (3) extraglomerular
mesangial (lacis) cells.
Q10. What is the normal blood flow to the kidneys per minute?
Answer: Normal renal blood flow is approximately 1,000–1,200
mL/min, which is about 20–25% of total cardiac output.
Q11. What is the role of ADH (antidiuretic hormone) in the kidney?
Answer: ADH (vasopressin) is released from the posterior pituitary and
acts on the collecting ducts to increase water reabsorption, thereby
concentrating urine and reducing urine output.
Q12. What is the filtration fraction?
Answer: Filtration fraction is the ratio of GFR to renal plasma flow
(RPF). It is normally about 0.20 (20%), meaning 20% of plasma flowing
through the kidneys is filtered.
Q13. Name the components of the nephron in order of fluid flow.
Answer: Bowman's capsule → Proximal convoluted tubule (PCT) →
Loop of Henle (descending then ascending limb) → Distal convoluted
tubule (DCT) → Collecting duct → Renal papilla → Minor calyx →
Major calyx → Renal pelvis → Ureter.
Q14. What is the function of the loop of Henle?
Certified Hemodialysis Bio-Medical Technician (CHBT) — Examination Preparation Study Guide
, CHBT Study Guide — 300 Q&A
Answer: The loop of Henle creates a concentration gradient (osmotic
gradient) in the renal medulla by reabsorbing solutes (primarily NaCl) in
the ascending limb without water, facilitating water reabsorption in the
collecting duct.
Q15. What is the role of the peritubular capillaries?
Answer: Peritubular capillaries reabsorb fluids and solutes that have
been transported out of the tubular fluid by the proximal and distal
tubules, returning them to systemic circulation.
───────────────────────────────────────────────
───────────────────────────────────────────
SECTION 2: HEMODIALYSIS PRINCIPLES & PHYSICS
Q16. What is the principle of diffusion in hemodialysis?
Answer: Diffusion is the movement of solutes across a semi-
permeable membrane from an area of high concentration (blood) to an
area of low concentration (dialysate), driven by the concentration
gradient.
Q17. Define ultrafiltration in the context of hemodialysis.
Answer: Ultrafiltration is the removal of fluid (water) across the dialyzer
membrane due to a transmembrane pressure (TMP) gradient. It is used
to remove excess fluid from the patient's body.
Q18. What is the transmembrane pressure (TMP)?
Answer: TMP is the pressure difference across the dialyzer
membrane, calculated as: TMP = [(arterial pressure + venous
pressure)/2] – dialysate pressure. It drives ultrafiltration.
Q19. What is the role of the dialyzer membrane?
Answer: The dialyzer membrane is a semi-permeable barrier that
allows diffusion of waste products and small molecules from blood to
dialysate while preventing large molecules (proteins) and blood cells
from passing through.
Q20. Explain the concept of clearance in hemodialysis.
Certified Hemodialysis Bio-Medical Technician (CHBT) — Examination Preparation Study Guide
, CHBT Study Guide — 300 Q&A
Answer: Clearance is the volume of blood from which a solute is
completely removed per unit time. It depends on the dialyzer's mass
transfer coefficient (KoA), blood flow rate, and dialysate flow rate.
Q21. What is the Donnan effect in hemodialysis?
Answer: The Donnan effect refers to the unequal distribution of
charged ions across a semi-permeable membrane due to the presence
of non-diffusible charged species (like albumin) on one side, creating
an electrochemical equilibrium.
Q22. What is the hollow fiber dialyzer and how does it work?
Answer: A hollow fiber dialyzer contains thousands of thin-walled,
semi-permeable polysulfone or similar fibers. Blood flows inside the
fibers while dialysate flows outside in the opposite direction (counter-
current), maximizing the diffusion gradient.
Q23. Define the KoA (mass transfer coefficient) of a dialyzer.
Answer: KoA is the overall mass transfer coefficient that describes the
dialyzer's ability to transfer a solute across the membrane. A higher
KoA indicates greater diffusion efficiency.
Q24. What is convective mass transfer in dialysis?
Answer: Convective mass transfer occurs when solutes are carried
(dragged) through the membrane along with water during ultrafiltration.
It is particularly effective for removing middle molecules.
Q25. Explain the counter-current flow principle in hemodialysis.
Answer: In counter-current flow, blood and dialysate move in opposite
directions through the dialyzer. This maintains a high concentration
gradient throughout the dialyzer, optimizing solute removal efficiency.
Q26. What is the concept of 'dialysis adequacy' and how is it
measured?
Answer: Dialysis adequacy refers to how well the dialysis session
removes uremic toxins. It is commonly measured using Kt/V urea,
where K = urea clearance, t = dialysis time, V = volume of distribution
of urea. A Kt/V ≥ 1.2 is the target.
Certified Hemodialysis Bio-Medical Technician (CHBT) — Examination Preparation Study Guide
CERTIFIED HEMODIALYSIS BIO-MEDICAL TECHNICIAN COMPLETE
EXAM QUESTIONS AND CORRECT ANSWERS
1: ANATOMY & PHYSIOLOGY OF THE KIDNEY
Q1. What is the primary function of the kidneys?
Answer: The primary function of the kidneys is to filter blood, remove
waste products and excess fluids, regulate electrolyte balance,
maintain blood pressure, and produce urine.
Q2. How many nephrons are present in each kidney?
Answer: Each kidney contains approximately 1 to 1.5 million nephrons,
which are the functional units responsible for filtering blood and
producing urine.
Q3. What is the glomerular filtration rate (GFR) and what is the
normal value?
Answer: GFR is the volume of fluid filtered per unit time from the
plasma flowing through the glomeruli. Normal GFR is approximately
90–125 mL/min (or ~180 L/day).
Q4. Name the three layers of the glomerular filtration barrier.
Answer: The three layers are: (1) the fenestrated endothelium of the
capillary wall, (2) the glomerular basement membrane (GBM), and (3)
the podocyte layer (visceral epithelium) with filtration slits.
Q5. What is the role of the tubuloglomerular feedback mechanism?
Answer: Tubuloglomerular feedback regulates blood flow and filtration
rate in the kidney by sensing NaCl concentration at the macula densa
in the distal tubule, causing vasoconstriction or dilation of the afferent
arteriole.
Q6. What percentage of filtered water is reabsorbed in the proximal
convoluted tubule (PCT)?
Answer: Approximately 65–80% of filtered water is reabsorbed in the
PCT via osmotic reabsorption that follows solute reabsorption.
Q7. What is the role of aldosterone in the kidney?
Certified Hemodialysis Bio-Medical Technician (CHBT) — Examination Preparation Study Guide
, CHBT Study Guide — 300 Q&A
Answer: Aldosterone is a mineralocorticoid that increases sodium
reabsorption in the collecting duct and distal tubule, thereby increasing
water retention and blood pressure.
Q8. Describe the renin-angiotensin-aldosterone system (RAAS).
Answer: RAAS: Decreased renal perfusion stimulates juxtaglomerular
cells to release renin, which converts angiotensinogen to angiotensin I.
ACE then converts it to angiotensin II, a vasoconstrictor that also
stimulates aldosterone secretion from the adrenal cortex.
Q9. What structures make up the juxtaglomerular apparatus?
Answer: The juxtaglomerular apparatus consists of: (1)
juxtaglomerular (granular) cells in the afferent arteriole wall, (2) macula
densa in the distal convoluted tubule, and (3) extraglomerular
mesangial (lacis) cells.
Q10. What is the normal blood flow to the kidneys per minute?
Answer: Normal renal blood flow is approximately 1,000–1,200
mL/min, which is about 20–25% of total cardiac output.
Q11. What is the role of ADH (antidiuretic hormone) in the kidney?
Answer: ADH (vasopressin) is released from the posterior pituitary and
acts on the collecting ducts to increase water reabsorption, thereby
concentrating urine and reducing urine output.
Q12. What is the filtration fraction?
Answer: Filtration fraction is the ratio of GFR to renal plasma flow
(RPF). It is normally about 0.20 (20%), meaning 20% of plasma flowing
through the kidneys is filtered.
Q13. Name the components of the nephron in order of fluid flow.
Answer: Bowman's capsule → Proximal convoluted tubule (PCT) →
Loop of Henle (descending then ascending limb) → Distal convoluted
tubule (DCT) → Collecting duct → Renal papilla → Minor calyx →
Major calyx → Renal pelvis → Ureter.
Q14. What is the function of the loop of Henle?
Certified Hemodialysis Bio-Medical Technician (CHBT) — Examination Preparation Study Guide
, CHBT Study Guide — 300 Q&A
Answer: The loop of Henle creates a concentration gradient (osmotic
gradient) in the renal medulla by reabsorbing solutes (primarily NaCl) in
the ascending limb without water, facilitating water reabsorption in the
collecting duct.
Q15. What is the role of the peritubular capillaries?
Answer: Peritubular capillaries reabsorb fluids and solutes that have
been transported out of the tubular fluid by the proximal and distal
tubules, returning them to systemic circulation.
───────────────────────────────────────────────
───────────────────────────────────────────
SECTION 2: HEMODIALYSIS PRINCIPLES & PHYSICS
Q16. What is the principle of diffusion in hemodialysis?
Answer: Diffusion is the movement of solutes across a semi-
permeable membrane from an area of high concentration (blood) to an
area of low concentration (dialysate), driven by the concentration
gradient.
Q17. Define ultrafiltration in the context of hemodialysis.
Answer: Ultrafiltration is the removal of fluid (water) across the dialyzer
membrane due to a transmembrane pressure (TMP) gradient. It is used
to remove excess fluid from the patient's body.
Q18. What is the transmembrane pressure (TMP)?
Answer: TMP is the pressure difference across the dialyzer
membrane, calculated as: TMP = [(arterial pressure + venous
pressure)/2] – dialysate pressure. It drives ultrafiltration.
Q19. What is the role of the dialyzer membrane?
Answer: The dialyzer membrane is a semi-permeable barrier that
allows diffusion of waste products and small molecules from blood to
dialysate while preventing large molecules (proteins) and blood cells
from passing through.
Q20. Explain the concept of clearance in hemodialysis.
Certified Hemodialysis Bio-Medical Technician (CHBT) — Examination Preparation Study Guide
, CHBT Study Guide — 300 Q&A
Answer: Clearance is the volume of blood from which a solute is
completely removed per unit time. It depends on the dialyzer's mass
transfer coefficient (KoA), blood flow rate, and dialysate flow rate.
Q21. What is the Donnan effect in hemodialysis?
Answer: The Donnan effect refers to the unequal distribution of
charged ions across a semi-permeable membrane due to the presence
of non-diffusible charged species (like albumin) on one side, creating
an electrochemical equilibrium.
Q22. What is the hollow fiber dialyzer and how does it work?
Answer: A hollow fiber dialyzer contains thousands of thin-walled,
semi-permeable polysulfone or similar fibers. Blood flows inside the
fibers while dialysate flows outside in the opposite direction (counter-
current), maximizing the diffusion gradient.
Q23. Define the KoA (mass transfer coefficient) of a dialyzer.
Answer: KoA is the overall mass transfer coefficient that describes the
dialyzer's ability to transfer a solute across the membrane. A higher
KoA indicates greater diffusion efficiency.
Q24. What is convective mass transfer in dialysis?
Answer: Convective mass transfer occurs when solutes are carried
(dragged) through the membrane along with water during ultrafiltration.
It is particularly effective for removing middle molecules.
Q25. Explain the counter-current flow principle in hemodialysis.
Answer: In counter-current flow, blood and dialysate move in opposite
directions through the dialyzer. This maintains a high concentration
gradient throughout the dialyzer, optimizing solute removal efficiency.
Q26. What is the concept of 'dialysis adequacy' and how is it
measured?
Answer: Dialysis adequacy refers to how well the dialysis session
removes uremic toxins. It is commonly measured using Kt/V urea,
where K = urea clearance, t = dialysis time, V = volume of distribution
of urea. A Kt/V ≥ 1.2 is the target.
Certified Hemodialysis Bio-Medical Technician (CHBT) — Examination Preparation Study Guide
