Overview of Renal Diseases

Question 1

How do we measure kidney function?

Answer 1

Blood tests:
-Creatinine
-Formulae
Urine output 
Elimination of radioisotopes
Creatinine:
From muscle cells 
Closest to an ideal endogenous 
Steady production means steady state in plasma dependent upon excretion
Small changes at good function= large changes in GFR
Urea:
Less reliable
Levels vulnerable to change for other reasons

Question 2

What is obstructive uropathy?

Answer 2

Prostatic obstruction causes 25% of AKI
Single remaining kidneys at high risk
Can still produce significant amounts of urine
Delay in correction (catheter or nephrostomy) compromises renal function permanently

Question 3

When should RRT be started?

Answer 3

RRT should be initiated once AKI is established and unavoidable but before overt complications have developed
Exposes the patient to potential of:
Venous thrombosis
Bacteraemia
Haemorrhage from anticoagulants
Plus some will recover without ever developing an absolute indication
Avoids:
Metabolic abnormalities and problems of volume overload

Question 4

What are the indications for acute dialysis?

Answer 4

Hyperkalaemia refractory to medical therapy- K+ > 6.5 with ECG changes
Severe acidosis pH < 7.25, HCO3 <15
Fluid overload- despite high-dose furosemide appropriate
Symptomatic uraemia: urea > 35:
Pericarditis, encephalopathy

Question 5

What are the presentations of GN?

Answer 5

Asymptomatic urinary abnormalities
CKD
Nephrotic syndrome
Nephritic syndrome
Rapidly progressive GN

Question 6

How is proteinuria quantified?

Answer 6

Urine analysis (blood and protein)
Proteinuria quantified by:
Urine albumin : creatinine ratio
Urine protein : creatinine ratio

Question 7

How can decreased GFR lead to bone mineral disease?

Answer 7

1. Decreased filtration rate
   
   2. Decreased phosphate load
   3. Phosphate retention
   4. Decreased 1,25 (OH)2 Vit D3 synthesis -> decreased calcium
      Directly increases PTH
   5. PTH release
   6. Long term leads to secondary hyperparathyroidism and bone disease

Question 8

How are anemia and impaired renal function linked?

Answer 8

Common and debilitating
80% of patients with advanced renal impairment
Defined as a state in which there is a reduced number of circulating red blood cells
Key indicator- Hb
CKD rates:
68% of patients on RRT
Stage 3= 5.2%
Stage 4= 44%

Question 9

What is end-stage renal failure?

Answer 9

Renal failure that requires renal replacement therapy
Kidney:
Excretes toxins
Sodium and water balance
Acid-base balance
Homeostasis
Endocrine- 1a vitamin D hydroxylation, erythropoietin
Metabolic

Question 10

When is dialysis inappropriate?

Answer 10

Unacceptable impact on quality of life
Patient choice
Imminent death
Dialysis may or may not increase lifespan:
- CO-morbidities e.g. cardiovascular
- New starters on haemodialysis who are aged over 75 have a 30% mortality rate within the first year

Question 11

How does haemodialysis work?

Answer 11

Blood passes down one side of a highly permeable membrane
Water and solutes pass across the membrane:
solutes up to 20,000 daltons- drugs and electrolytes
Infuse replacement solution with physiologic concentrations of electrolytes

Question 12

How does peritoneal dialysis work?

Answer 12

PD catheter into the patients abdomen
Peritoneum used as the membrane:
-Solute and water exchange between peritoneal capillary blood and dialysate fluid
-Membrane= vascular wall, interstitium, mesothelium and adjacent fluid films
Small molecules transfer by diffusion
Fluid movement determined by osmosis:
-Dialysate dextrose concentration 
-Solvent drag for middle sized molecules

Question 13

What are the different types of donors?

Answer 13

Related
Unrelated 
Altruistic 
Deceased donors:
Donation after brain death (DBD)
Donation after circulatory death (DCD)