Measurement of Renal Function Flashcards
According to the British National Formulary (BNF) what are the 3 reasons why we need to measure renal function?
1 - identify renal impairment in your patient
2 - modification of dosages of drugs which are cleared by the kidneys
3 - plan appropriate management of renal dysfunction
When assessing a patient with suspected renal impairment, why would be measure fluid balance and what symptoms may be associated with fluid balance?
- oedema may be present
- can cause breathlessness
When assessing a patient with suspected renal impairment, what could an imbalance in the patients electrolytes cause, specifically in the heart?
- abnormal ECG:
- absent P waves
- broad QRS complex
- peaked T waves
When assessing a patient with suspected renal impairment, if we detect low erythropoietin levels which is produced by the kidney, what can this cause patients to present with?
- pallor
- fatigue
When assessing a patient with suspected renal impairment, if we detect low vitamine D3 (active vitamine D) levels which is produced by the kidney, what can this cause patients to present with?
- osteomalacia (softening of bones)
- bone pain
When assessing a patient with suspected renal impairment, what are some haemodynamic measurements that would provide information about the patients condition?
- pulse
- BP
When assessing a patient with suspected renal impairment, why are fluid charts useful that would provide information about the patients condition?
- determines if patient is dehydrated
- urine passed helps with this as well
When assessing a patient with suspected renal impairment, why would serial blood tests be useful?
- creatinine is filtered out in urine normally
- if this is high in urine then GFR is not functioning effectively
- FBC
When assessing a patient with suspected renal impairment, why would an arterial blood gas be useful?
- measures acid base shift
- pH
- metabolic acidosis
When assessing a patient with suspected renal impairment, why would urinalysis be useful?
- identify if glucose and proteins are present in the urine
What are the main imaging modalities used to investigate renal impairment?
- renal ultrasound scan (mostly first scan)
- CT/MRI Kidney Ureter Bladder
- Nuclear Medicine
What is the main manifestation of renal impairment?
- oedema
- can be felt on patients
- patients weight monitored (if in hospital)
If blood is found in the urine, what does this indicate?
- blood loss is occuring in either the kidney, ureter or bladder
What is the most common cause of kidney disease?
- diabetes
In addition to doing a FBC, what other measures would you look at in the blood if you suspect the patient has impaired kidney function?
- serum creatinine
- serum urea
- serum HCO3-
- serum K+
In addition to doing a FBC, creatinine is a useful measures that would be completed in a patient with impaired renal function, why is this?
- creatinine is breakdown product of creatine phosphate from muscles
- creatinine is filtered at glomerulus and secreted into urine
- if plasma creatinine is high then GFR is reduced
In addition to doing a FBC, creatinine is a useful measures that would be completed in a patient with impaired renal function. Creatinine is breakdown product of creatine phosphate from muscles and is filtered at glomerulus and secreted into urine. High levels of serum creatinine would suggest what?
- low GFR
- normal range = 40-120 mmol/L
In addition to doing a FBC, creatinine is a useful measures that would be completed in a patient with impaired renal function. Creatinine is breakdown product of creatine phosphate from muscles and is filtered at glomerulus and secreted into urine. High levels of serum creatinine can suggest a low GFR, where a normal serum creatinine is 40-120 mmol/L. What instances can serum creatinine be raised in a young or old individual?
- young may exercise more so increased creatinine
- old may have atropy or creatinine so decreased creatinine
In addition to doing a FBC, creatinine is a useful measures that would be completed in a patient with impaired renal function. Creatinine is breakdown product of creatine phosphate from muscles and is filtered at glomerulus and secreted into urine. High levels of serum creatinine can suggest a low GFR, where a normal serum creatinine is 40-120 mmol/L. Drugs can affect creatinine levels, what can the antibiotic trimethoprim do to creatinine levels?
- used to treat UTI
- blocks secretion of creatinine into proximal tubules
- blood creatinine levels go up
- ALWAYS CHECK FOR THIS DRUG
Urea is produced in the liver as a waste product of protein digestion, before being excreted by the urinary system. If urea is raised or decreased in patients with renal impairment, why is this?
- it is secreted from tubules in collecting ducts
- if high, suggests the secretion/reabsorbtion is impaired
- can be raised on high protein diet or GIT bleeds
- can be decreased in liver disease andmalnourished
When we talk about renal clearance, what do we mean by clearance?
- volume of plasma completely cleared of a given substance in unit time
- compares rate at which glomeruli filter a substance with the rate at which the kidneys excrete it via the urine
- clearance = (Glomerular filtration + Tubular secretion) – Tubular reabsorbtion
When designing an ideal molecule to meausure renal clearance, what would the molecule have to do?
- be a naturally occurring molecule
- not metabolised or synthesized in kidney
- only excreted by the kidney
- filtered but not secreted or reabsorbed by the kidney
Inulin is filtered by the glomerulus and NOT reabsorbed, which makes this an excellent measure of renal functin. But what is the problem with inulin?
- has to be administered
- not natural compound
Paraaminohippurate is an exogenous substance that can be used to assess renal function, why is this a good compound to use?
- it is freely filtered at the glomerula
- not reabsorbed in tubules but fully secreted
- % in urine is a measure of renal function
