BODY SYSTEMS
RENAL
,Medic_Summaries (Body Systems)
Renal Strand
Functions of kidneys:
- Two broad functions:
- Homeostasis (maintenance of internal environment of body)
- Hormone secretion (endocrine function)
- Fluid/electrolyte balance:
- Volume status (regulates fluid balance (urine))
- Electrolyte levels (Na, K, urea, creatinine)
- Osmolarity (concentration of particles exerting osmotic pressure (glucose))
- Acid-base balance:
- Maintains optimum pH for cellular function
- Bicarbonate regeneration (proximal tubule)
- Removal of fixed acid
- Recovery of small molecules:
- Sugars (glucose in urine can indicate diabetes mellitus/tubular disorders)
- Amino acids (loss of amino acids occurs in disease of proximal tubule)
- Excretion of waste products/drugs:
- Nitrogenous waste from protein metabolism (urea and creatinine)
- Creatinine released from muscles; level in blood measures kidney function
- Drugs can accumulate in kidney disease (antibiotics, digoxin, opiates, lithium)
- Red blood cell production:
- Erythropoietin (EPO)
- Stimulated by hypoxia
- Patients with kidney disease develop anaemia
- Recombinant EPO decreases need for blood transfusions
- Used by athletes for doping
- Calcium/phosphate balance:
- Secretes activated form of vitamin D
- First stage (liver); second stage (kidneys)
- Increases absorption of Ca from gut
- Blood pressure control:
- Renin secretion (converts angiotensinogen to angiotensin I)
- Angiotensin I is the angiotensin II pre-cursor
- Angiotensin II is a vasoconstrictor
- Patients with kidney disease often have high blood pressure
Chronic kidney disease:
- Kidneys activate vitamin D
- In CKD, there is decreased activation of vitamin D and decreased Ca level
- Stimulates secretion of parathyroid hormone (PTH):
- Secondary hyperparathyroidism
- Releases Ca from bone
- Develop bone disease (renal osteodystrophy)
Blood tests:
- Urea/electrolytes (U&Es):
- Sodium (Na+): 133-146mmol/L
- Potassium (K+): 3.5-5.3mmol/L
- Urea: 2.5-7.5mmol/L
- Creatinine: 64-104µmol/L (male); 60-93µmol/L (female)
- 50% loss of function if beyond this value
- Bicarbonate (HCO3-): 22-29mmol/L
- Chloride (Cl-): 95-108mmol/L
2 Adapted from Lectures at the University of Leeds Medical School
, Medic_Summaries (Body Systems)
Urine tests (urinalysis):
- pH
- Haematuria (blood not normal)
- Proteinuria (protein not normal)
- Glucose (diabetes/CKD)
- Nitrates (infection)
- Leucocytes (infection)
- Protein/creatinine ratio: 0.1-13.0mg/mmol/L
- Albumin/creatinine ratio: 0.1-3.0mg/mmol/L
- Midstream urine (MSU) - clean catch of urine (sent if UTI suspected)
Radiological tests:
- Ultrasound (size of kidney, obstruction)
- Doppler
- CT kidneys ureter bladder (KUB)
- Magnetic resonance angiography (MRA)
Kidney biopsy:
- Required to diagnose some forms of kidney disease
- Ultrasound guidance
- Complications include risk of bleeding (1/100) and losing a kidney (1/1000)
Kidneys and blood:
- Every minute, 1200mL blood enters both kidneys (20% total blood pumped by the heart)
- In one day, 1700L blood is purified (this equates to 1.5-2L urine)
- Adults have 7-8L blood
- This blood is therefore filtered ca. 400 times per day
Glomerular filtration rate (GFR):
- Measurement of renal function (normal = 100-120mL/min/1.73m2)
- Accurate measurement requires injection of radioactive tracer (Tc99)
Creatinine clearance:
- Estimation of glomerular filtration rate
- Creatinine released from muscle at relatively constant rate
- Filtered by kidneys (some secretion into filtrate by proximal tubule; not as accurate)
- Rarely used in clinical practice (blood test; 24-hour urine collection)
Serum creatinine:
- Released by muscle and removed by kidneys
- Simple blood test (64-104µmol/L (male); 60-93µmol/L (female))
- Routinely used to measure kidney function
- Accumulates in kidney disease (not specific injury site; delay in rise following acute injury)
Estimated glomerular filtration rate (eGFR):
- Used instead of creatinine clearance/alongside creatinine
- Calculated using age, sex, ethnicity, serum creatinine
- Correlates with percentage of kidney function (eGFR = 50; 50% kidney function)
- Useful when discussing with patients
- Patients will need to commence dialysis as eGFR <10mL/min/1.73m2
Glomerular filtration rate (GFR) Interpretation
>90 Normal
60-90 May correspond to stage 3 CKD
30-60 Corresponds to stage 3 CKD
3 Adapted from Lectures at the University of Leeds Medical School
RENAL
,Medic_Summaries (Body Systems)
Renal Strand
Functions of kidneys:
- Two broad functions:
- Homeostasis (maintenance of internal environment of body)
- Hormone secretion (endocrine function)
- Fluid/electrolyte balance:
- Volume status (regulates fluid balance (urine))
- Electrolyte levels (Na, K, urea, creatinine)
- Osmolarity (concentration of particles exerting osmotic pressure (glucose))
- Acid-base balance:
- Maintains optimum pH for cellular function
- Bicarbonate regeneration (proximal tubule)
- Removal of fixed acid
- Recovery of small molecules:
- Sugars (glucose in urine can indicate diabetes mellitus/tubular disorders)
- Amino acids (loss of amino acids occurs in disease of proximal tubule)
- Excretion of waste products/drugs:
- Nitrogenous waste from protein metabolism (urea and creatinine)
- Creatinine released from muscles; level in blood measures kidney function
- Drugs can accumulate in kidney disease (antibiotics, digoxin, opiates, lithium)
- Red blood cell production:
- Erythropoietin (EPO)
- Stimulated by hypoxia
- Patients with kidney disease develop anaemia
- Recombinant EPO decreases need for blood transfusions
- Used by athletes for doping
- Calcium/phosphate balance:
- Secretes activated form of vitamin D
- First stage (liver); second stage (kidneys)
- Increases absorption of Ca from gut
- Blood pressure control:
- Renin secretion (converts angiotensinogen to angiotensin I)
- Angiotensin I is the angiotensin II pre-cursor
- Angiotensin II is a vasoconstrictor
- Patients with kidney disease often have high blood pressure
Chronic kidney disease:
- Kidneys activate vitamin D
- In CKD, there is decreased activation of vitamin D and decreased Ca level
- Stimulates secretion of parathyroid hormone (PTH):
- Secondary hyperparathyroidism
- Releases Ca from bone
- Develop bone disease (renal osteodystrophy)
Blood tests:
- Urea/electrolytes (U&Es):
- Sodium (Na+): 133-146mmol/L
- Potassium (K+): 3.5-5.3mmol/L
- Urea: 2.5-7.5mmol/L
- Creatinine: 64-104µmol/L (male); 60-93µmol/L (female)
- 50% loss of function if beyond this value
- Bicarbonate (HCO3-): 22-29mmol/L
- Chloride (Cl-): 95-108mmol/L
2 Adapted from Lectures at the University of Leeds Medical School
, Medic_Summaries (Body Systems)
Urine tests (urinalysis):
- pH
- Haematuria (blood not normal)
- Proteinuria (protein not normal)
- Glucose (diabetes/CKD)
- Nitrates (infection)
- Leucocytes (infection)
- Protein/creatinine ratio: 0.1-13.0mg/mmol/L
- Albumin/creatinine ratio: 0.1-3.0mg/mmol/L
- Midstream urine (MSU) - clean catch of urine (sent if UTI suspected)
Radiological tests:
- Ultrasound (size of kidney, obstruction)
- Doppler
- CT kidneys ureter bladder (KUB)
- Magnetic resonance angiography (MRA)
Kidney biopsy:
- Required to diagnose some forms of kidney disease
- Ultrasound guidance
- Complications include risk of bleeding (1/100) and losing a kidney (1/1000)
Kidneys and blood:
- Every minute, 1200mL blood enters both kidneys (20% total blood pumped by the heart)
- In one day, 1700L blood is purified (this equates to 1.5-2L urine)
- Adults have 7-8L blood
- This blood is therefore filtered ca. 400 times per day
Glomerular filtration rate (GFR):
- Measurement of renal function (normal = 100-120mL/min/1.73m2)
- Accurate measurement requires injection of radioactive tracer (Tc99)
Creatinine clearance:
- Estimation of glomerular filtration rate
- Creatinine released from muscle at relatively constant rate
- Filtered by kidneys (some secretion into filtrate by proximal tubule; not as accurate)
- Rarely used in clinical practice (blood test; 24-hour urine collection)
Serum creatinine:
- Released by muscle and removed by kidneys
- Simple blood test (64-104µmol/L (male); 60-93µmol/L (female))
- Routinely used to measure kidney function
- Accumulates in kidney disease (not specific injury site; delay in rise following acute injury)
Estimated glomerular filtration rate (eGFR):
- Used instead of creatinine clearance/alongside creatinine
- Calculated using age, sex, ethnicity, serum creatinine
- Correlates with percentage of kidney function (eGFR = 50; 50% kidney function)
- Useful when discussing with patients
- Patients will need to commence dialysis as eGFR <10mL/min/1.73m2
Glomerular filtration rate (GFR) Interpretation
>90 Normal
60-90 May correspond to stage 3 CKD
30-60 Corresponds to stage 3 CKD
3 Adapted from Lectures at the University of Leeds Medical School
