Urology Flashcards
What is an acute kidney injury?
An acute kidney injury is characterised by a decline in renal function that happens rapidly (over hours to days)
What classification is an acute kidney injury diagnosed on?
based on the Kidney Disease: Improving Global Outcomes (KDIGO) criteria
What are the Kidney Disease: Improving Global Outcomes criteria?
Increase in serum creatinine by ≥26.5 µmol/l within 48 h, or
Increase in serum creatinine ≥ 1.5x the baseline within the last 7 days, or
Urine output < 0.5 ml/kg/h for 6 hours
Name some risk factors for AKI?
Patients with CKD
Elderly patients
Previous AKI
Malignancy
Medical conditions increasing risk of urinary obstruction (e.g. benign prostatic hyperplasia)
Cognitive impairment and disability (may be reliant on others for fluid intake)
Recent use of medications such as NSAIDs or ACE inhibitors
Recent administration of iodine-containing contrast media
Name some pre-renal causes of Acute Kidney Injury?
due to decreased renal perfusion
Hypovolaemia (e.g. dehydration, haemorrhage, gastrointestinal losses, burns)
Renovascular disease (e.g. renal artery stenosis)
Medications reducing blood pressure or renal blood flow (e.g. NSAIDs, ACE inhibitors, ARBs, diuretics)
Hypotension due to reduced cardiac output (e.g. heart failure, sepsis)
Name some renal causes of acute kidney injury?
due to structural damage to the kidneys
The glomeruli (e.g. acute glomerulonephritis, nephrotic syndrome)
The tubules (e.g. acute tubular necrosis due to ischaemia or toxins, rhabdomyolysis - Muddy brown casts in the urine represent collections of dead renal tubule epithelial cells - results in high fractional excretion of sodium)
The interstitium (e.g. acute interstitial nephritis secondary to drugs)
The renal vessels (e.g. renal vein thrombosis, vasculitis)
Name some post-renal causes of acute kidney injury?
obstructed to urinary flow anywhere along the urinary tract
Luminal (e.g. ureteric stones or a blocked catheter)
Intramural (e.g. urethral or ureteric strictures, ureteric carcinomas)
Due to external compression (e.g. an abdominal or pelvic tumour, benign prostatic hyperplasia)
What classifies as stage 1 AKI?
Creatinine rise of 26 micromol/L or more within 48 hours
Creatinine rise to 1.5-1.99x baseline within 7 days
Urine output < 0.5 mL/kg/hour for more than 6 hours
What classifies as stage 2 AKI?
Creatinine rise to 2-2.99x baseline within 7 days
Urine output < than 0.5 mL/kg/hour for more than 12 hours
What classifies as stage 3 AKI?
Creatinine rise to 3x baseline or higher within 7 days
Creatinine rise to 354 micromol/L or more with either - Acute rise of 26 micromol/L or more within 48 hours or - 50% or more rise within 7 days
Urine output < than 0.3 mL/kg/hour for 24 hours
Anuria for 12 hours
Name some symptoms of AKI?
Nausea and vomiting
Fatigue
Confusion
Anorexia
Pruritus
What do we look for in examination of AKI?
Hypertension (a complication of AKI)
Bladder distension due to urinary retention
Hypotension and dehydration (in many pre-renal causes)
Signs of fluid overload (e.g. raised jugular venous pressure, pulmonary and peripheral oedema) as a complication of AKI
Signs related to the underlying cause (e.g., fevers in sepsis, rashes in vasculitis)
Pericardial rub (in uraemic pericarditis)
What bedside tests do we do for AKI?
Urinalysis - urine dip may show blood and protein in glomerular disease, increased white blood cells may suggest infection or interstitial nephritis
ECG to screen for complications of hyperkalaemia
Blood gas to look for acidosis as a complication of AKI, allows rapid potassium measurement
What blood tests do we do for AKI?
U&Es to get creatinine for diagnosis (compare to baseline if available) and check for hyperkalaemia
Full blood count may show anaemia in vasculitis or raised white cells in infection
LFTs may be deranged in severe hypotension causing ischaemic hepatitis
Clotting as a baseline in case a renal biopsy is later required (rare)
Bone profile to screen for hypercalcaemia (seen in myeloma which can cause renal AKI)
Creatinine kinase to look for rhabdomyolysis
CRP may be raised in infection or vasculitis
What imaging do we for AKI?
Bladder scan if urinary retention is suspected
Ultrasound KUB (kidneys, ureters and bladder) if a post-renal cause is suspected, may show hydronephrosis. The next line of imaging would be a CT KUB as this is a more sensitive modality.
What bloods do we do for an acute renal screen?
ANA
Double-stranded DNA
Anti-nuclear cytoplasmic antibodies
Anti-GBM antibodies
Erythrocyte sedimentation rate
Serum immunoglobulins
Serum electrophoresis
Serum free light chains
Complement levels (C3 and C4)
HIV screening
Hepatitis B and C serology
If the diagnosis is still unclear and a renal cause is suspected, a renal biopsy may be indicated.
The basic screen is: Protein electrophoresis, C3, C4, ANA, dsDNA, ANCA, anti-GBM, immunoglobulins
What is the management for AKI?
The key to AKI management is identification and treatment of the underlying cause
The most common cause of AKI is dehydration, and so for many patients IV fluid resuscitation will be required
Careful assessment of fluid status is crucial though, as in certain cases where the patient is fluid overloaded diuretic treatment rather than fluids may be required
Fluid balance should be monitored closely with consideration of catheterisation to monitor urine output
A catheter may be the definitive treatment in some cases (e.g. post-renal AKI due to urethral obstruction)
Screen for complications of AKI (e.g. hyperkalaemia, acidosis, pulmonary oedema) and instigate treatment promptly
Involve the renal team early in severe or complicated AKIs, where the cause is unclear or where a renal cause is suspected
Name some drugs that may need to be reviewed in AKI?
Review regular medications and suspend any nephrotoxic drugs (e.g. NSAIDs, aminoglycosides, ACE inhibitors, ARBs) and review those that may cause complications in cases of renal impairment (e.g. opiates, metformin)
“Stop the DAMN drugs”
Diuretics and digoxin
ACE inhibitor/ ARB
Metformin and methotrexate
NSAIDs
In the case of metformin NICE advises reducing the dose if eGFR is < 45 ml/min/1.73 m2 and to stop metformin if the eGFR is < 30 ml/min/1.73 m2.
In AKI what signs would prompt referral for consideration of renal replacement e.g dialysis or haemofiltration?
Acidosis (severe metabolic acidosis with pH of <7.20) - Electrolyte imbalance (resistant hyperkalaemia) - Intoxication (AKI secondary to certain drugs or poisons) - Oedema (refractory pulmonary oedema signified by bibasal crackles on auscultation) - Uraemia (uraemic encephalopathy or pericarditis)
What are the signs and symptoms of uraemia?
Uraemia caused by acute kidney injury results in the accumulation of urea in the bloodstream, leading to nonspecific symptoms such as nausea, vomiting, confusion, seizures and a characteristic “uraemic tinge” visible on the skin.
What kind of shock due to sepsis leads to renal hypoperfusion and is a common cause of pre-renal acute kidney injury.
distributive
Iodinated contrast agent is nephrotoxic and increases the risk of AKI - what is a risk factor that increases the chance of an AKI?
Age 75 or over increases the risk of AKI with contrast agents
What is haemolytic uraemic syndrome?
classical features of haemolytic uraemic syndrome - with features of bloody diarrhoea, fever, vomiting, acute kidney injury and haemolysis. Most cases occur following an E.coli O157:H7 diarrhoea. Treatment is supportive with fluid rehydration, haemofiltration, steroids and plasmapheresis
An increase by what percentage of creatinine would result in an ACE inhibitor being stopped?
A 30% increase in creatinine levels two weeks after initiating an ACE-inhibitor