Nephrology Investigations Flashcards
Define AKI
Abrupt reduction in kidney function resulting in the retention of nitrogenous products (urea) + dysregulation of electrolytes
What staging tool is used in nephrology to asses for:
AKI
CKD
Both use KDIGO staging although there are different parameters for both obv
What is considered reduced urine output?
<0.5 ml/kg/hr
Run me through the KDIGO staging for AKI
Stage 1:
Serum creatinine >1.5x baseline or >0.3mg/dl within 48hrs
OR Reduced urine output for 6+ hours
Stage 2:
Serum creatinine >2x baseline
OR Reduced urine output for 12+ hours
Stage 3:
Serum creatinine >3x baseline or >4mg/dl
OR Anuria/Reduced urine output for 24+ hours
What is the GFR of a patient who is not producing any urine? This patient has an eGFR of 10
Anuria is GFR of 0 regardless of what eGFR is
Drugs are typically eliminated via kidney excretion. Certain drugs have an increased risk of causing AKI and should have their doses appropriate to the patient’s kidney function Give 3 pre-renal and 3 intra-renal drugs leading to AKI.
Pre-renal:
Drugs affecting kidney perfusion (ACE inhibitors!!!, NSAIDs, Diuretics)
Intra-renal:
Nephrotoxins (Gentamicin, Vancomycin, contrast media, chemotherapy drugs)
What are the Pre-renal causes of AKI
Pre-Renal (reduced supply)
1) Hypovolaemia (cardiogenic/neurogenic/haemorrhagic shock)
2) Sepsis
3) Congestive HF
4) Renal artery stenosis
5) ACE inhibitors!!!
What are the Intra-renal causes of AKI
Renal:
1) Ischaemia
2) Nephrotoxins (Gentamicin, Vancomycin, contrast media, chemotherapy drugs)
3) Glomerulonephritis
4) Interstitial nephritis
5) Hepatorenal syndrome
6) HUS/TTP
What are the Post-renal causes of AKI:
Post-Renal: obstructive
1) Nephrolithiasis
2) Tumour obstruction
3) Prostate hypertrophy/tumour
4) Blocked
5) Catheter/outflow obstruction
What is Hepatorenal syndrome?
What will show on blood tests supporting this?
Conditioned characterised by a rapidly progressive (type 1) or gradual (type 2) decline in kidney function in patients with advanced liver disease such as cirrhosis or acute liver failure.
This deterioration is due to splanchnic vasodilation and renal vasoconstriction
Like any other decline in renal function. Raised creatinine and urea as well as reduced urine output and GFR
Give 10 causes of AKI
Pre-Renal (reduced supply)
1) Hypovolaemia (cardiogenic/neurogenic/haemorrhagic shock)
2) Sepsis
3) Congestive HF
4) Renal artery stenosis
5) Drugs affecting kidney perfusion (ACE inhibitors!!!, NSAIDs, Diuretics)
Renal:
1) Ischaemia
2) Nephrotoxins (Gentamicin, Vancomycin, contrast media, chemotherapy drugs)
3) Glomerulonephritis
4) Interstitial nephritis
5) Hepatorenal syndrome
6) HUS/TTP
Post-Renal: obstructive
1) Nephrolithiasis
2) Tumour obstruction
3) Prostate hypertrophy/tumour
4) Blocked
5) Catheter/outflow obstruction
Define CKD
Abnormalities of kidney structure and function for >3 months
How would you assess kidney function and damage? Give 5 methods
GFR (best for kidney function)
ACR/PCR (Best for kidney damage)
Urinary sediment abnormalities
Imaging abnormalities
Biopsy/histological/pathological abnormalities
The KDIGO tool is used to grade kidney function and damage. Run me through it
ACR - Damage
A1 - Normal <3.4
A2 - Moderately increased 3.4-34
A3 - Severely increased - >34
eGFR - Function
G1 - Normal - 90+
G2 - Mild increase - 60-89
G3 - Moderate decrease A - 45-59, B - 30-44
G4 - Severe Decrease - 15-29
G5 - ESKD (kidney failure)
Give 10 causes of CKD
Glomerular -> Diabetes, Sepsis, Autoimmune, Drugs, neoplasia
Vascular -> Atherosclerosis, HTN, Ischaemia, Vasculitis
Tubulointerstitial -> UTI, Nephrolithiasis, Obstruction (BPH, prostate/bladder cancer)
Genetic -> ADPKD, Alport
What is in a U&E?
Creatinine
BUN
Calcium
Phosphate
K+
Na+
You obtain results from a U&E which show a disproportionately raised Urea but relatively normal eGFR and creatinine. What is this suggestive of?
Why?
A disproportionate rise in urea compared to creatinine suggests hypovolaemia, a pre-renal cause of AKI
This is because in hypovolemic patients, water, Na, and Urea are increasingly reabsorbed in the PCT giving a rise in urea without a decrease in eGFR
T or F: Creatinine is used to calculate eGFR because it is solely excreted as is from serum to elimination
False, some is also secreted in the PCR and hence as eGFR decreases, creatinine increases
Creatinine is neither excreted nor metabolised by the kidney and hence used to measure eGFR. There is, however some secretion in the PCT. Early falls in eGFR may not increase serum creatinine and hence not the best for early renal disease nor in AKI (hence why we dont use eGFR when discussing AKIs). What are some factors affecting serum creatinine levels? Give 3
Remeber creatinine is used to calculate eGFR => think of factors that may influence the calculation
1) Age, Gender, Race
2) Muscle mass/protein-rich diet
3) Ingestion of Red meat within 12 hours
4) Pregnancy
What are the 2 most used methods of estimating eGFR?
CKD-EPI equation (takes into acount creatinine, age, and gender)
24 hour creatinine clearance
Muscle mass, protein-rich diet, and red meat consumption affects creatine levels. What tool will you use to estimate eGFR in a patient with these factors?
CockCroft-Gault
What does a Urine Dipstick detect?
Proteinuria
Haematuria
Haemoglobinuria
Glycosuria
Ketones
Bilirubin
Urobilinogen
Leukocytes
Nitrites
Specific gravity
What is the difference between haematuria and haemoglobinuria
Haematuria is the presence of blood in urine
Haemoglobinuria is the presence of haemoglobin in the urine (After RBC breakdown)
Nephrotoxic drugs can lead to what type of AKI? (not pre-renal/intrarenal…)
Acute tubular necrosis
What is the significance of Haemoglobinuria (what does it indicate)?
Free haemoglobin in the urine suggests intravascular haemolysis such as TTP, DIC, prosthetic valve etc.. This is significant as haemoglobin is nephrotoxic and hence can lead to acute tubular necrosis/AKI
You are performing a urine dipstick showing ketones. Give 5 ddx
Dehydration!!
DKA
Starvation
Alcoholism
Pre-eclampsia/eclampsia
Hyperthyroidism