Acute Renal Failure/Kidney Injury Flashcards Preview

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Flashcards in Acute Renal Failure/Kidney Injury Deck (38)
1

Define ARF

- clinical syndrome of sudden onset of haemodynamic, filtration and excretory failure of kidneys
- subsequent accumulation of metabolic (uraemia) toxins and dysregulation of fluid, electrolyte and acidness balance

2

Define ARF

- clinical syndrome of sudden onset of haemodynamic, filtration and excretory failure of kidneys
- subsequent accumulation of metabolic (uraemia) toxins and dysregulation of fluid, electrolyte and acidness balance

3

Define AKI

- acute kidney injury
- abrupt decline in kidney function
- acute ^ in creatinine concentration and/or acute decline in urine output (even if patient has not become azotaemic)

4

Is ARF reversible?

Potentially if dx early and animal supported while renal injury repaired
- irreversible renal damage may occur -> death

5

Define oliguria. How does its cause affect tx?

typically

6

How does ARF present? How can it be diagnosed?

- many cases no hx or CS
- potentially known toxin ingestion
- anuric/polyuric
- more often, lethargy, unwell, V+ or azotemia detected on bloods
- ureic signs (smell, ulcers etc.)
- dehydration
- brady/tachycardia
- painful kidneys

7

Define AKI

- acute kidney injury
- abrupt decline in kidney function
- acute ^ in creatinine concentration and/or acute decline in urine output (even if patient has not become azotaemic)

8

Is ARF reversible?

Potentially if dx early and animal supported while renal injury repaired
- irreversible renal damage may occur -> death

9

Clinical signs of ARF?

- anuria and oliguria characterise severe forms
- does NOT occur in all cases
- some will be PU
- NB: GFR does NOT = urine output
> GFR can v as urine output ^ if reabsorption is becoming less effective

10

How can pre-renal and renal azotemia be differentaited?

- need urine and bloods obtained simultaneously (before starting IVFT)
> USG >1.035 [cat] or >1.030 [dog] for pre-renal, 1.007-1.025 typically for a 1* renal
> urine sediment inflam/casts with 1* renal sometimes
> dipstick may show glycosuria in 1* renal sometimes
- no biochem results can be used to make a distinction BUT hyperkalaemia more common in ARF or post-renal causes (though can occur in terminal phases of CKD
- respnse to fluid tx dramatic with pre-renal, minimal if renal cases

11

How does ARF present? How can it be diagnosed?

- many cases no

12

Can pre-renal azotemia ever be present when USG

Yes : diuretics or drugs affecting concentrating ability (functional impediment to urine concentration)
- fluids, diuretics, glucocorticoids, Addiosons, hypercalcaemia
> can be better prognosis if functional renal failure present rather than structural intrinsic renal disease (where nephrons have physically been lost)

13

Causes of post-renal azotemia?

- urethral obstruction
- bladder rupture

14

Causes of pre-renal azotemia?

- severe dehydration
- shock
- any condition -> poor renal perfusion

15

How can pre-renal and renal azotemia be differentaited?

- need urine and bloods obtained simultaneously (before starting IVFT)
> USG >1.035 [cat] or >1.030 [dog] for pre-renal, 1.007-1.025 typically for a 1* renal
> urine sediment inflam/casts with 1* renal sometimes
> dipstick may show glycosuria in 1* renal sometimes
- no biochem results can be used to make a distinction BUT hyperkalaemia more common in ARF or post-renal causes (though can occur in terminal phases of CKD
- respnse to fluid tx dramatic with pre-renal, minimal if renal cases §

16

DO failing kidneys produce dilute urine?

NO! Canot dilute so hyposthenuria does NOT occur in kidney failure

17

Can pre-renal azotemia ever be present when USG

Yes : diuretics or drugs affecting concentrating ability (functional impediment to urine concentration)
- fluids, diuretics, glucocorticoids, Addiosons, hypercalcaemia
> can be better prognosis if functional renal failure present rather than structural intrinsic renal disease (where nephrons have physically been lost)

18

How can ARF and CKD be differentiated?

- NO LAB TESTS! Hyperphosphatemia seen with both acute and chronic
> Except renal BIOPSY (but this is invasive and results take a long time)
- PE: poor BCS, poor quality haircoat
- Hx: wt loss, v apetite, PUPD v hx of access to nephrotoxic drugs or toxins
- non-regenerative anaemia typically with CKD but can occour with ARF (eg. d/t haemorrhagic shock) or overhydration
- renal size (generally v with CKD, ^ with ARF but some chronic dz -> normal/^ kidney size)
- presence of CKD mineral bone disorder (renal 2* hyperparathyroidism) : resorption of bone esp. around the teeth
> NB: rubber jaw may be a presenting sign but very rare and only seen in young growing animals

19

3 main causes of acute renal failure?

> pre-renal
> intrinsic renal
- tubular necrosis (v. common) d/t ichaemia or toxins or both
- interstitial nephritis (common)
- acute glomerulonephritis (uncommon, next lect)
> post-renal

20

What is hospital acquired ARF/AKI?

- ischaemia and toxin effects on kidney working synergistically -> tubular necrosis
- eg. CV dz pre-existing, age, fever, dehydration, drugs

21

Cause and clinical signs of pyelonephritis? How is it diagnosed?

> ascending UTI -> renal pelvis and medulla causing an INTERSTITIAL NEPHRITIS
> CS
- systemic illness (fever, renal pain, nephromegaly)
- BUT signs may be absent
- PUPD esp with E. Coli
- can cause acute/chronic renal azotemia
> Dx presumptive based on cultures obtained from LUT, imaging and hx findings
- if pelvis dilated can aspirate for culture under u/s guidance

22

Tx pyelonephritis?

As for complicated UTIs (selection of ABx based on culture, 4-6w tx, cultures a week after starting and finishing tx)

23

What infectious organism also causes an interstitial nephritis?

> Leptiospriosis
- ZOONOTIC
- spirochete bacteria (each serovar typuically has 1+ host species that carry the organism asymptomatically and shed in the urine)

24

Clinical signs of leptospirosis in a non-host organism>

- ARF
- hepatocellular necoris

25

Most common route of infection of leptospirosis?

- contaminated water
> most commonly now non-vaccinal serovars that affect dogs (ie. not canicola or icterohaemorrhagica)

26

Do cats get lepto?

No resistant

27

How can lepto be dx?

- high Ab titre to non-vaccinal serovars
- rising titre over a few weeks
- PCR (not very sensitive, maybe d/t Ab use before testing?)

28

Tx leptospirosis?

- tx ARF
- penicillins (usually amoxicillin)
- if dx confirmed then 2w course doxycycline prescribed to eliminate infection and prevent dog become a chronic carrier

29

What must be remembered about lepto?

ZOONOTIC
- carefully manage patients, don't come into contact with urine

30

2 causes of tubular necrosis?

> ischaemia
- outer medulla exists in a constant state of oxygen deprivation
- cells of PCT high metabolic rate
- mitochondrial injury, cell swelling, tubular obstruction
- d/t yhpovolaemia, v effective circulating volume (heart failure/cirrhosis), thrombosis, excessive renal vasoconstriction
- pre-renal azotemia can -> renal d/t ischameia if hypoperfusion not rectified
> toxins
- may occour concurrently and synergistically with ishaemia
- often leaves some BM intact so if given the supportive tx kidneys can recover

31

Egs of nephrotoxic drugs and substances?

> drugs
- Abx (aminoglycosides, tetracyclines, amphotericin B [fungal])
- chemotx (doxorubicin [cats], cis and carboplatin, methotrexate)
- NSAIDs
- ACEI
- IV contrast agents
> other
- hypercalcaemua
- rasins/grapes (dogs)
- ethylene glycol (cats)
- plants [lillies] (cats)
-myoglobin/haemoglobin
- heavy metals
- pesticides/herbicides
- snake venom

32

3 miscellaneous causes of ARF/AKI?

> lyme disease
- borrelia burgdorferi
- acute glomerular disease
> Renal lymphoma
> cutaneous/renal vascular glomerulopathy (New FOrest Syndomre/Alabama Rot)
- thrombotic microangiopathy

33

How can ARF be prevented?

> some unavoidable (toxins etc.)
> in the hospital ID patients at high risk
- pre-existing CKD
- dehydrationhypovolaemia/hypotension
- sepsis/fever/hyperthermia
- systemic dz/multiple organ failure
- prolonged anaesthesia
- drug tx (NSAIDs, aminoglycosides, cisplatin, amphotericin, ACEI)
> more effectively prevented by correcting fluid deficits and mild ECF volume expansion

34

Tx ARF/AKI?

*aim to maintain the animal while kidneys repair themselves*
> prevent continued toxin exposure or give antidotes
- induce vomiting, NB: maintain euvolaemia
- 4-methylpyrazole for ethyleme glycol $$$
> Tx 1* underlying disease if possible
> correct fluid deficits
- monitor in and outs to prevent overhydration
- aim for mild 3-5% ECVF fluid expansion
> Recitfy potassium and acid/base balance
> attempt to ^ urine output if required
- NB: urine output does NOT = GFR
> other pharmacological tx
- controversial and infrequently used
> control V+
- address nutritional requirements
> renal replacement tx
- haemodialysis or peritoneal dialysis

35

Give examples of drugs that can be used to attempt to ^ urine output if necessary?

> mannitol
- slow IV bolus
- ^ renal blood flow, v cellular swelling, dispense tubular debris and scavenge free radiacal (Appaz)
- indicated early in course of ARF but animal MUST BE EUVOLAEMIC, not in hert failure or overhydrated
- only useful if already producing some urine
- rarely used
> furosemide
- boluses or CRI
- +- other drugs
- promotes formation of urine, facilitates management of overhyration and hyperkalaemia
- may deplete circulating volume -> pre-renal insult

36

Which other pharmacological tx may be used 9controversially) with ARF?

> dopamine
- suggested to cuase renal vasodilation and ^ blood flow at low dodses
- not recommended unless ^ BP needed- high doses -> tachycardia, arrhythmias, vasoconstriction
- do not use in cats
> Fenoldopam
- selective DA1 ag sometimes used in preference
> Diltiazem
- pre-glomerular arteriolar dilation and improve renal blood flow
- v calcium influx into damaged tubular cells may also be beneficial

37

Can extensive tubular injury be repaired?

- even if potentially reversible usually not possible to keep patients alive for weeks/months like humans on dialysis to allow regeneration

38

What can be used as an earlier indicator of acute renal failure?

Enzymeuria (occurs before azotaemia begins)