Acute Renal Failure

Question 1

Functions of the kidney?

Answer 1

1. Excretion of nitrogenous waste
2. Regulation of water, electrolytes and BP
3. Synthesis

Question 2

Effect of kidney failure on salt and water homeostasis?

Answer 2

1. Fluid overload
   - peripheral oedema
   - pulmonary oedema
2. Fluid depletion

Question 3

Effect of kidney failure on BP control?

Answer 3

hypertension

Question 4

Effect of kidney failure on the removal of uremic toxins?

Answer 4

Uremia
1. encephalopathy
2. pericarditis
3. nausea
4. vomiting
5. hiccup
6. bleeding tendency
7. neuropathy

Question 5

Effect of kidney failure on calcium/phosphate balance?

Answer 5

1. Hyperphosphatemia
2. Hypocalcaemia
3. Renal bone disease
4. Tertiary hyperparathyroidism

Question 6

Effect of kidney failure on EPO production?

Answer 6

anemia

Question 7

Effect of kidney failure on potassium balance?

Answer 7

hyperkalemia

Question 8

Effect of kidney failure on acid-base balance?

Answer 8

metabolic acidosis

Question 9

Relevance of kidney disease?

Answer 9

1. CKD = cardiovascular risk
2. CVS events are common and the major cause of morbidity and mortality from CKD
3. CKD is now affecting younger populations in their economic prime
4. Likelihood of CVS death is far greater than progression to ESRD

Question 10

Definition of acute renal failure?

Answer 10

Rapid decline in GFR over days or weeks

Question 11

AKI results in?

Answer 11

1. Retention of nitrogenous wastes, creatinine and other toxins
2. Oliguria occurs in ≈ 50%
   Note: May be reversible

Question 12

Causes of in hospital morbidity and mortality?

Answer 12

because of underlying illnesses and high incidence of subsequent complications
Complicates ≈ 5% of hospital admissions, ≈ 30% of ICU admissions

Question 13

Criteria for AKI categories?

Answer 13

1. change in serum creatinine levels
2. urine output

Question 14

Category 1 for AKI?

Answer 14

1. 1.5 – 1.9 times increase in SCr from baseline or
   >0.3mg/dl increase in se
2. <0.5ml/kg/hr for 6 to 12 hours

Question 15

Category 2 for AKI?

Answer 15

1. 2.0 – 2.9 x increase in SCr from baseline
2. <0.5ml/kg/hr for >12 hours

Question 16

Category 3 for AKI?

Answer 16

1. 3.0 x increase in SCr from baseline or Creatinine >4mg/dl
2. <0.3ml/kg/hr over 24 hours or
   Anuria > 12 hours

Question 17

Undergraduate classification of AKI?

Answer 17

1. Pre Renal - Circulatory Failure = “Shock”
2. Renal - The cells of the kidney
3. Post Renal - Obstruction

Question 18

Pre-renal failure?

Answer 18

• 50 – 60% of all cases
• Renal parenchyma preserved
• Falling renal blood flow leads to a falling GFR
• This might be due either to changes in the circulation, or to intrarenal vasomotor changes that drop glomerular perfusion pressures

Question 19

Prerenal causes of AKI?

Answer 19

1. Hypovolaemia
   - dehydration or haemorrhage
2. Hypotension without hypovolaemia
   - cirrhosis or septic shock
3. Low cardiac output
   - cardiac failure or cardiogenic shock
4. Renal artery stenosis

Question 20

Post renal AKI?

Answer 20

Mechanical obstruction of the urinary collecting system
- Renal pelvis, ureters, bladder, or urethra
- Obstructive uropathy

Question 21

Postrenal causes of AKI?

Answer 21

1. Ureteric obstruction
   - Stone disease, tumor, fibrosis, ligation during pelvic surgery
2. Bladder neck obstruction
   - Benign prostatic hypertrophy (BPH), CA prostate, neurogenic bladder, tricyclic antidepressants, ganglion blockers, bladder tumor, stone disease, hemorrhage/clot
3. Urethral obstruction
   - Strictures, tumor, phimosis
4. Intra-abdominal hypertension
   - Tense ascites
5. Renal vein thrombosis

Question 22

Describe prerenal AKI?

Answer 22

• caused by renal hypoperfusion
• Integrity of renal parenchyma is preserved = pre-renal
• 50-60% of cases

Question 23

Causes of intrinsic renal failure?

Answer 23

1. tubular
   - interstitial nephritis : 10%
   - ATN : 75-80%
   > ischemic
   > toxic
2. glomerular
   - glomerulonephritis
3. vascular
   - vasculitis

Question 24

Describe postrenal failure?

Answer 24

• Obstruction of urine flow
• < 5%

Question 25

Urine sediment used in differential diagnosis?

Answer 25

1. normal or few RBC, WBC 2. granular casts 3. RBC casts 4. WBC casts 5. Eosinophiluria 6. Crystalluria

Question 26

3 phases of acute renal failure?

Answer 26

1. Initial phase: exposure to ischemia / toxin. - Evolution of parenchymal injury - ARF preventable 2. Maintenance phase: established injury - may last 1-2 weeks or months 3. Recovery phase: repair and regeneration

Question 27

Management of prerenal ARF?

Answer 27

1. replace fluid and what was lost - controversy colloid vs. crystalloid - Normal Saline seems best - Urinary/GI losses usually hypotonic 2. If CHF treat arrhythmias, inotropes, reduce preload/afterload 3. If cirrhosis, paracentesis ± albumin, FFP, shunt 4. Remove offending drugs

Question 28

Management of intrinsic ARF?

Answer 28

1. Prevention:- optimize cardiac function, volume status 2. caution with ACEI, NSAIDS, vasodilators 3. Treat according to specific cause

Question 29

Diagnosis of ARF?

Answer 29

1. History and examination 2. Routine bloods 3. Extra bloods – bicarbonate, CK, 4. CRP + blood cultures 5. ECG 6. CXR

Question 30

Treatment of ARF?

Answer 30

1. Immediate - Airway and Breathing 2. Circulation - restore renal perfusion (fluid resuscitation ± inotrope) - hyperkalaemia - pulmonary oedema 3. Remove causes - drugs - sepsis 4. Exclude obstruction & consider ‘renal’ causes - are the pre-renal causes sufficient to account for ARF? 5. Ask for help: ICU or renal unit

Question 31

Indications for dialysis in ARF?

Answer 31

A E I O U A – severe metabolic acidosis of renal origin and refractory to medical therapy E – electrolyte abnormalities – refractory hyperkalemia =>6.5 I – intoxication with dialysable compounds O – fluid overload especially pulmonary edema refractory to diuretic therapy U- uremia – pericarditis, bleeding, confusion (encephalophathy) Oligo/anuria

Question 32

Features of the ECG in hyperkalemia?

Answer 32

1. loss of P wave 2. tall peaked T wave 3. widened QRS with tall T wave

Question 33

Management of hyperkalemia?

Answer 33

Most important when K+ >6.0 1. Remove offending agent e.g. drugs 2. 10mls of 10% Calcium gluconate IV 3. 10 units of Soluble insulin with 50mls of 50%dextrose IV – then monitor blood sugar 4. Nebulised salbutamol/albuterol 5. Frusemide if in pulmonary edema 6. Oral Kayexelate (K binding resin)