Urology

Question 1

What is an AKI? What is its effect on homostasis. How is it measured?

Answer 1

A rapid reduction in kidney function over hours to days leading to a failure to maintain fluid, electrolyte and acid base balance. Measured by serum urea and creatine

Question 2

What are the defining chemical changes in AKI? Over what timeframe

Answer 2

Rise in creatinine by more than 26micromoles/L in 48 hours Risk in creatinine by 1.5 baseline (lowest within 3 months) within one week (known or presumed) Urine output

Question 3

Risk factors for aki

Answer 3

Age Ckd Chf Liver disease Pvd Dm Sepsis Drugs Poor fluid intake / increased loss Urinary symptoms

Question 4

What drugs are nephrotoxic increasing aki risk?

Answer 4

Nsaids Acei Arbs Gentamycin Iodine contrast

Question 5

How is AKI graded?

Answer 5

Stage 1 - as diagnostic criteria Stage 2 - rise 2 to 2.9 baseline or 3 baseline or >345 or RRT needed or

Question 6

What are the three sub classifications of AKI?

Answer 6

Prerenal Renal Post renal

Question 7

What are causes of pre renal AKI? What drugs may worsen it?

Answer 7

Shock/volume depletion (CHF, hypovolaemia, sepsis, dehydration etc.) Renal artery stenosis AAA Hepatorenal syndrome ACEi or NSAIDs

Question 8

Why do ACEi cause AKI when given to a patient with renal artery stenosis?

Answer 8

Angiotensin II causes vasoconstriction of afferent and efferent arterioles in the kidney. In renal artery stenosis the afferent already has low flow so GFR is maintained by efferent constriction. ACEi stops efferent constriction via decreased ang II thus decreases GFR

Question 9

What effect does prerenal AKI have on kidney function?

Answer 9

Decreased GFR Active reabsorption of Na (as high renin thus high angiotensin II due to poor perfusion) so low amount of Na passed in urine

Question 10

How should pre renal AKI be treated?

Answer 10

Fluid replacement Treat underlying cause Stop nephrotoxic drugs, especially NSAIDs and ACEi

Question 11

What are the four broad catagories of renal AKI cause?

Answer 11

Tubular Glomerular Interstitial Vascular

Question 12

What is the general term for and what are causes of tubular renal aki?

Answer 12

Acute tubular necrosis Any cause of prerenal with progression Diuretics Myoglobinuria Haemoglobinuria Endotoxins Radiological contrast agents Nephrotixic drugs - aminoglycosides, acei, nsaids Poisons - weedkiller, antifreeze Preeclampsia and eclampsia

Question 13

What is the pathology behind acute tubular necrosis

Answer 13

Ischemia or toxic insult to tubular cells causing damage Low atp in cells Decreased reabsorption due to na/katpase dysfunction and bleb formation blocking reabsorption so more sodium to macula densa so less gfr due to afferent arteriole constriction (Tubularglomerular feedback) Increased tubular hydrostatic pressure (backleak of filtrate) decreases gfr Obstruction of tubules by debris decreases gfr

Question 14

What would help differentiate prerenal aki from acute tubular necrosis - test and clinical sign?

Answer 14

Fraction of excreted sodium high in atn Poor response to fluids with oedema

Question 15

How may urine output change over the course of acute tubular necrosis? How long does it last?

Answer 15

Early - oliguria Late - polyuria as defective reabsorption despite low gfr Usually around 1-3 weeks post initial insult but can be up to 6

Question 16

Other than atn how can tubular issues cause renal aki?

Answer 16

Blockage - e.g. Sulphonamide cystals, uraemia (eg post chemo), myeloma light chains

Question 17

Causes of glomeurlar renal AKI?

Answer 17

Glomerularnephritis Pre eclampsia Malignant hypertension

Question 18

Causes of interstitial renal AKI

Answer 18

Toxins (drugs etc) Infections (acute pylonephritis)

Question 19

Causes of vascular renal AKI?

Answer 19

Vasculitis Hypertension Pre-eclampsia

Question 22

Useful tests in AKi

Answer 22

Dip urine (everyone) Volume status (pulse, BP, JVP, peripheral temp, oedema, skin turgor) (everyone) Urine microscopy (if dipstick +ve) Urine biochemistry (FENa) (to differentiate prerenal/renal if unclear) USS (if suspected post renal or cause unknown/not improving) CXR (to look for fluid overload) Histology (not pre renal or post renal and not clear ATN or systemic signs of glomerularnephritis)

Question 23

How could AKI secondary to myoglobin be treated?

Answer 23

Alkaline diuresis

Question 24

Hw should acidosis causing AKi be treated?

Answer 24

Protein restrict Sodium bicarbonate

Question 25

Indications for dialysis in AKI

Answer 25

High K refractory to treatment Metabolic acidosis refractory to treatment Fluid overload refractory to diuretics Dialysavle nephrotoxin (aspiring, antifreeze) Uremic symptoms

Question 26

What are uremic symptoms?

Answer 26

Nausea and vomiting Puritis Fits and coma Pericarditis Hamorrhage

Question 28

Treatment of renal AKI

Answer 28

Fluid restriction aiming for euvolemic Consider frusemide Stop nephrotoxins Treat sepsis Consider dialysis Treat compications

Question 30

Causes of postrenal AKI - divide into 3 broad catagories

Answer 30

In the lumen - calculi, blood clot, sloughed papilla, tumour In the wall - stricture (congential, infection, surgery), neuropathic bladder Outside the wall - tumour, diverticulitis, AAA, prostate, phimosis

Question 31

In what ways can urine protein be measured?

Answer 31

Dipstick

24 hour collection

PCR

ACR