Renal Flashcards
How is AKI diagnosed?
Serum creatinine levels
What is the diagnostic criteria for AKI?
Rise in creatinine > 25micromol/L in 48h
Rise in creatinine > 50% in 7d
Urine output < 0.5ml/kg/h over 6h
List risk factors for AKI
> 65y
Sepsis
CKD
HF
Diabetes
Liver disease
Cognitive impairment- Decreased fluid intake
Medications (NSAIDs, gentamicin, diuretics and ACE-is)
Radiocontrast agents (CT scans)
List pre-renal causes of renal impairment
Insufficient blood supply to kidneys reducing filtration of blood
- Dehydration
- Shock (septic or acute blood loss)
- HF
List renal causes of renal impairment
Intrinsic disease in kidneys
- Acute tubular necrosis
- Glomerulonephritis
- Acute interstitial nephritis
- HUS
- Rhabdomyolysis
List post-renal causes of renal impairment
Obstruction to outflow of urine
- Kidney stones
- Tumours
- Strictures of ureters or urethra
- BPH
- Neurogenic bladder
What is acute tubular necrosis?
Damage and death of epithelial cells of renal tubules
What are the causes of acute tubular necrosis?
Ischaemia due to hypoperfusion (dehydration, shock, HF)
Nephrotoxins (gentamicin, radiocontrast, cisplatin)
What is seen on urinalysis in acute tubular necrosis?
Muddy brown casts
Renal tubular epithelial cells
What is the prognosis of acute tubular necrosis?
Epithelial cells regenerate = Reversible
Recovery in 1-3wks
What does urinalysis +ve for protein and blood suggest?
Acute nephritis
How to test for obstructive cause of AKI
US
Outline management of AKI
IV fluids
Withhold meds that worsen condition- NSAIDs, ACE-is
Withhold meds that may accumulate with reduced renal function- Metformin and opiates
Catheter if obstruction
Dialysis if severe
List complications of AKI
Fluid overload, HF, pulmonary oedema
Hyperkalaemia
Metabolic acidosis
Uraemia (high urea)- Can lead to encephalopathy and pericarditis
Define CKD
Chronic reduction in kidney function sustained over 3mths- Permanent and progressive
List causes of CKD
Diabetes
HTN
Meds- NSAIDs or lithium
Glomerulonephritis
PKD
Outline presentation of CKD
Fatigue
Pallor (anaemia)
Foamy urine (protein)
Nausea
Loss of appetite
Pruritis
Oedema
HTN
Peripheral neuropathy
What is eGFR based on?
Serum creatinine
Age
Gender
What is GFR?
Rate at which fluid is filtered from blood into Bowman’s capsule
How do you quantify proteinuria?
Urine albumin : Creatinine ratio (ACR)
Outline diagnostic criteria of CKD
eGFR sustained below 60mL/min/1.73m2
Urine ACR sustained above 3mg/mmol
Outline G score
Based on eGFR- Marker of CKD
- G1>90
- G2 60-89
- G3a 45-59
- G3b 30-44
Outline A stage
Based on ACR- Marker of CKD
- A1 <3mg/mmol
- A2 3-30mg/mmol
- A3 >30mg/mmol
What is accelerated progression in CKD?
Sustained decline in eGFR within 1yr of either 25% or 15mL/min/1.73m2
List complications of CKD
Anaemia
Renal bone disease
CVD
Peripheral neuropathy
End stage kidney disease
List criteria for referral to renal specialist
eGFR<30mL/min/1.73m2
Urine ACR > 70mg/mmol
Accelerated progression
5yr risk of requiring dialysis >5%
Uncontrolled HTN despite 4+ antihypertensives
List medications that slow disease progression of CKD
ACE-i/ARBs
SGLT-2 inhibitor (dapagliflozin)
List medications that reduce the risk of complications of CKD
Exercise, maintain healthy weight, avoid smoking
Atorvastatin 20mg for primary prevention CVD
List medications that manage complications of CKD
Oral sodium bicarbonate- Metabolic acidosis
Iron and erythropoietin- Anaemia
Vit D, low phosphate diet, phosphate binders- Renal bone disease
Why does anaemia occur in CKD?
Kidneys produce EPO (produces RBCs)
CKD= Lower EPO and RBC production
Normocytic, normochromic anaemia
What is renal bone disease?
CKD- Mineral bone disorder
High serum phosphate
Low Vit D
Low serum calcium
Why does renal bone disease occur?
Reduced phosphate excretion by diseased kidneys results in high serum phosphate
Kidneys metabolise vit D to activate, normally allows calcium absorption in intestines and reabsorbed in kidneys- Responsible for regulating bone turnover and promoting bone reabsorption
Parathyroid glands react to low serum calcium and high serum phosphate by excreting more PTH- Secondary hyperparathyroidism
PTH stimulates osteoclast activity, increasing calcium absorption from bone
Why does osteomalacia occur?
Increased turnonver of bones without adequate calcium supply
Why does osteosclerosis occur?
Osteoblasts respond by increasing activity to math the osteoclasts, create new tissue in bone
Low calcium level means new bone not properly mineralised
Outline management of renal bone disease
Low phosphate diet
Phosphate binders
Active forms of Vit D (alfacalcidol and calcitriol)
Ensuring adequate calcium intake
When are ACE-is offered to patients with CKD?
Diabetes + urine ACR >3mg/mmol
HTN + urine ACR >30mg/mmol
All patients with urine ACR >70mg/mmol
What in particular needs monitoring in patients with CKD taking ACE-is?
Serum potassium- Risk of hyperkalaemia
What is the criteria for offering SGLT-2 inhibitors to patients with CKD?
Dapagliflozin
Offered- Diabetes plus urine ACR >30mg/mmol
Considered- Diabetes plus urine ACR 3-30mg/mmol
Non-diabetic with ACR >22.6mg/mmol
What is a rugger jersey spine?
Finding on spinal X-ray involving sclerosis of both ends of each vertebral body (denser white) and osteomalacia in centre (less white)
What is dialysis and when is it used?
Performs filtration tasks of kidneys artificially
Used in end-stage renal failure or complications of acute AKI
Removes excess fluids, solutes and waste products
What are the indications for short-term dialysis?
A- Acidosis (severe and not responding to treatment)
E- Electrolyte abnormalities (treatment resistant hyperkalaemia)
I- Intoxication
O- Oedema (severe and unresponsive pulmonary oedema)
U- Uraemia symptoms (seizures, reduced consciousness)
Outline haemodialysis
4h/d, 3d/wk
Blood taken out of body passed through machine, passes along semipermeable membranes inside machine
Solutes filter out of blood into dialysate and conc. gradient causes water and solutes to leave blood
Anticoagulation with citrate and heparin prevents blood clotting in machine
What are the long term access options for haemodialysis?
Tunnelled cuffed catheter (tube in subclavian or jugular vein with tip in SVC or RA)- Has 2 lumens- Red (blood exiting) and blue (blood entering)
Arteriovenous fistula (artificial connection between artery and vein, bypasssing capillary system)- Requires 4-16wks after surgery till it can be used
What are the main complications of a tunnelled cuffed catheter?
Infection
Blood clots
What are the main complications of an AV fistula?
Aneurysm
Infection
Thrombosis
Stenosis
STEAL syndrome
High-output HF
Where can a fistula be placed for haemodialysis?
Radiocephalic- Wrist- Radial artery to cephalic vein
Brachiocephalic- Antecubital fossa- Brachial artery to celhalic vein
Brachiobasilic- Upper arm- Less common
What are the features of a fistula on examination?
Check skin integrity
Aneurysms
Palpable thrill (fine vibration over anastomosis)
Machinery murmur on auscultation over fistula
List complications of AV fistulas
Aneurysm
Infection
Thrombosis
Stenosis
STEAL syndrome
High-output HF
What is STEAL syndrome?
Inadequate blood flow to limb distal to fistula
AV fistula steals blood from rest of limb- Blood diverted away from part of limb it was supposed to supply= Ischaemia
What is high-output HF?
Caused by blood flowing quickly from arterial to venous system through AV fistula
Rapid return of blood to heart= Increased pre-load= Hypertrophy of heart muscle and HF
What is a key rule regarding fistulas?
Never take blood from a fistula= Risk of damage
Outline the complications of peritoneal dialysis
Bacterial peritonitis
Peritoneal sclerosis- Thickening and scarring of peritoneal membrane
Ultrafiltration failure- Dextrose absorbed, reducing filtration gradient= Less effective
Weight gain- Due to absorption of dextrose
Psychosocial impairment
What is peritoneal dialysis?
Uses peritoneal membrane to filter blood
Dextrose added to peritoneal cavity
Ultrafiltration occurs from blood, accross peritoneal membrane, into dialysis solution
Dialysis solution replaced, taking away waste products
What is the tube used in peritoneal dialysis called?
Tenckhoff catheter