Renal Flashcards
What 3 parts are the glomerular filtration barrier made up of?
- Epithelial cells of the bowmans capsule
- Glomerular basement membrane
- Fenestrated capillary endothelium
What forms the visceral layer of renal corpuscle in the glomerulus?
Podocytes
a) What is the glomerular filtration rate?
b) What methods are used to assess GFR?
a) The sun of the filtration rates in all the functioning nephrons - the volume of plasma filtered by the glomerulus per unit of time
b) - Creatine clearance - Plasma creating concentration - Estimation equation e.e.g Cockrofts Gault, MDRD
What is a healthy
a) GFR for women
b) GFR for men
c) Urine output
a) 95 +/- 20 ml/min
b) 120 +/- 25 ml/min
c) 2-3 L/day
What is creatine and where is it filtered?
Derived from metabolism of skeletal muscle and meat
Freely filtered across glomerulus and 15% from tubular secretion by proximal tubule
What is the formula for creatine clearance?
Urine creatine concentration x Volume / Plasma creatine concentration
What are the limitations of using creatine clearance?
- Incomplete urine collection
- Increased creatine secretion from tubule in renal impairment
If GFR is low, what will the level of creatine be?
What is the shape of the curve of creatine against GFR?
Creatine high
Exponential (L shape)
Who doesnt glomerular filtration rate work in?
- Children
- Amputees
- Pregnancy
Describe stage 1 and stage 2 of chronic kidney disease (CKD)
1 - GFR 90+, normal function, may have structural abnormalities, observe and control BP
2 - GFR 60-89, mildly reduced function, observe and control BP and address risk factors
Describe Stage 3 CKD
- GFR 30-59
- Pt asymptomatic
- Creatine marginally raised
- Tend to retain solutes, become hypertensive
- Reduced vit D and calcium
- Reduced Epo, become anaemic
- Observe, BP control and modify drug doses, avoid nephrotoxins
Describe Stage 4 CKD
- GFR 15-29
- Creatine 250-600umol/L
- Tired, pale, non-specifically unwell
- Need dietary restriction, phosphate binders, vit D and erythropoeitin
- Usually need anti-hypertensive drugs and diuretics
Describe Stage 5 CKD
- GFR <15
- Creatine >700
- End stage renal failure requiring dialysis if GFR<5mls/min or creatine >900
- Pale, tired, unwell
- Anorexic, nausea, vomiting, uraemic fetor, itch
- Confusion
- Fluid retention, oedema, congestive cardiac failure
What condition can cause chronic renal failure?
Diabetes (affects small blood vessels)
Give examples of drugs in CRF pts:
a) that are renally excreted so may accumulate
b) that have an altered protein binding
c) that are nephrotoxic so worsen renal function
a) Opiates
b) Increased protein binding = basic drugs e.g. lignocaine. Decreased protein binding = acidic drugs e.g. Phenytoin
c) NSAIDS, Gentamicin
What are the effects of uraemia on the haematology of CKF pts?
- Prolonged bleeding time
- Normal platelet count but disturbed platelet function
- Increased bruising
- Check pt not on aspirin or clopidogrel
How is bleeding time improved in CKF pt with uraemia?
Dialysis or increased haematocrit (with Erythropoeitin)
Name 4 effects of chronic renal failure
- Pulmonary and Peripheral oedema (due to salt and water retention)
- Restless Leg syndrome - cramps, tremors and twitches
- Hormonal imbalance
- Increased cardiac instability (severe metabolic acidosis, hyperkalaemia and hypocalcaemia)
What is the definition of acidaemia?
A pH of <7.2 (HCO3- <16mmol/L) that impacts cellular and cardiac function
What medical intervention can offer a bridge in pts with acidaemia until dialysis is available?
Sodium bicarbonate
What are additional causes of acidaemia?
- Lactic acidosis
- DKA
- Poisoning
What happens if a patient misses dialysis session?
Lungs can fill with fluid and become breathless - pulmonary oedema
In what circumstance should anticoagulation be avoided in dialysis?
Pericardial effusion as it will reduce the risk of pericardial bleeding
For Haemodialysis
a) How often?
b) Where is the fistula connected?
c) What anticoagulation is used?
d) What does it achieve?
a) 4 hrs 3 x week
b) Tunneled intrajugular neckline or arm arteriovenous (Brachial AV)
c) Heparin
d) Fluid removal and biochemical correction
What are the issues with AV fistula?
Haematoma and Infection
What are the 2 types of vascular access lines for dialysis?
Temporary line ‘Vascath’ (high infection risk, internal jugular, lasts 1-2 yrs)
Tunelled lines ‘Tesid’ (cuff reduces infection)
What are the pros and cons of continuous ambulatory dialysis (CAPD)?
\+ Gentle, good biochemical control \+ No anticoagulation - Weight gain with glucose as osmotic agent - Peritonitis - Peritoneal membrane failure over time
What are the complications of uraemia and dialysis?
- Hypotension
- Cramp
- Anaemia
- Vascular calcification
- Increased risk of heart disaes
- Amyloidosis as a consequence of beta-2-microglobulin accumulation
Who does not require antibiotic prophylaxis?
- Immunosupressed transplant patients
- Dialysis patients
- CRF patients with no valve/endocarditis risk
- CAPD or tunelled central line patients
Who does require antibiotic prophylaxis? What cover is given?
- Haemodialysis patients with a prosthetic valve or other endocarditis risk
- Amoxicillin 3g 1 hr before procedure or IV Vancomycin or Gentamycin for dialysis pts, Clindamycin for penicillin allergies
What rare inherited syndrome is associated with kidney disease and also causes bifid tongue?
Orofacial digital syndrome
What drugs that are used in immunosupression for renal transplants cause gingival hypertrophy?
- Tacrolimus/Fk506 and Cyclosporin A/Neoral
What drugs that are used in immunosupression for renal transplants cause hyperlipidaemia, delayed wound healing and stomitis?
Sirolimus or Rapamycin
Which immunosuppressive drugs used in renal transplant pts inhibit purine synthesis?
Azathioprine and mycophenolate mofetil (MMF)
What is the MOA of cyclosporin and tacrolimus?
Calcineurin inhibitor which blocks activation of T cells and so of cytokines such as IL2
What is a clinical feature of nephrotic syndrome?
Bilateral periorbital oedema
What is nephrotic syndrome?
- Massive proteinuria with hypoalbuminaemia
- Leaky kidneys so low levels of protein in intravascular compartment
What are the clinical implications of treating a patient with nephrotic syndrome?
- Taking long term steroids
- Electrolyte disturbances and steroid treatment lead to risk of infection
- Pts more likely to have cardiovascular disorders
What is the most common cause of end stage renal failure?
Diabetic nephropathy
What should you be thinking of if treating a patient with a renal transplant?
- Steroid cover for certain procedures that are physiologically stressful
- No antibiotic cover but bear in mind for M.O.S
- Predisposition to infections: oral candidosis, herpes simplex, zoster virus - in some cases low dose aciclovir given
- Greatly increased chance of malignant disease e.g. skin cancer and lymphomas as immunosuppressed
Describe the feedback loop that makes renal osteodystrophy a universal feature of CKD
Increase in plasma phosphate levels
Supression of plasma calcium
Elevated parathyroid hormone levels (PTH)
Calcium taken out of bones
Calcium further compromised by disruption in Vit D metabolism
Renal osteodystrophy in CKD pts can also be secondary to use of which drug?
Steroid therapy (osteoporosis and bisphosphonate therapy)
Why does anaemia occur in CKD pts?
Failure of production of erythropoietin by kidneys
Renal loss of RBCs
Marrow fibrosis
Increased RBC fragility with early destruction
Reduced platelet count and function
What are the features of anaemia of chronic disease seen in CKD pts?
- Normochromic
- Normocytic
- Hb 70g/L (normal is 180g/L)
- Reduced platelet count/functioning
When is the optimal time for dental treatment after dialysis?
1 day - heparin worn off and renal function optimal
Why might there be problems with haemostasis in a CKD pt?
- Impaired platelet count and adhesion
- Decreased von Willebrands factor
- Decreased thromboxane
- Prostacyclin levels increased (vasodilation)
- Heparinisation (heparin wears off quickly)
What may you notice about a CKD pt on examination?
E/O - Fistula, Oedema, Steroid facies (moon face), swelling of major salivary glands/sialosis (dialysis pts)
I/O - Increased incidence of ulceration and infections, gingival hyperplasia (cyclosporin), palatal and buccal keratosis sometimes seen (xerostomia)
What would you notice O/E of a child with CKD?
- Decreased growth
- Delayed tooth eruption and enamel hyperplasia (due to metabolic disturbances)
Which drugs should you avoid in CKD pts?
- Tetracyclines (other than doxycycline)
- NSAIDs (unless mild)
- Gentamycin (nephrotoxic)
- If had a transplant and taking cyclosporin Erythromycin
Which drugs should you reduce dose of in CKD pts?
Aciclovir, Amoxicillin, Ampicillinm Cefalexin, Erythromycin
What is acute kidney injury?
Medical emergency, potassium rises to a dangerous level that leads to cardiac arrythmias and cardiac arrest. May be seen in hypovolaemia (if bled a lot)
How can potassium level be lowered in acute kidney injury?
- Calcium resonium (rectal)
- Glucose and insulin IV infusion - take potassium out of bloodstream
