Acute Renal Failure

Dr Grania Price
 What is Acute Renal Failure?
• Deteriortion in renal function, ie increased
urea and creatinine
• Decreased urine output can occur before
abnormal blood results
• Pathophysiology
– Ischemia
– Anoxia
– Toxic
– Inflammatory
 Pre-renal ARF
• Most common and if not corrected can lead to
permenant intrinsic damage
• Can be due to
– decreased perfusion secondary to burns, bleeds,
sepsis, dehydration
– Decreased cardiac output
– Afferent arteriolar vasoconstriction seen in high
Ca2 ,medications and hepato-renal failure
– Efferent arteriolar vasodilation – ACEI or ARB
 Renal (intrinsic) ARF
• Structural injury to the kidney, commonly ATN
• Intra-renal vasoconstriction is main mode of
injury in ATN
• A physiologic hallmark of ATN is a failure to
maximally dilute or concentrate urine
• Can be further broken down into
– Vascular
– Glomerular
– Tubular
– Interstitial
 Post renal ARF
• Mechanical obstruction of the urinary
collecting system
• If obstruction is one-sided will not always
cause ARF
• Patients who develop anuria typically have
obstruction at the level of the bladder or
downstream to it.
• Causes range from stones, strictures and
tumours
 History
• Attempt to differentiate acute from chronic
• A history of chronic symptoms of fatigue,
weight loss, anorexia, nocturia, and pruritus
all suggest chronic renal failure.
• Ask for PMHx (eg BP,CCF,DM,Multiple
myeloma)
• Drug history
• Urine Output
 Examination
• BP, Pulse rate for volume status
– Hypovolemia leads to hypotension; however,
hypotension may not necessarily indicate
hypovolemia
– Severe hypertension with renal failure suggests
renovascular disease, glomerulonephritis, vasculitis,
or atheroembolic disease
• Evidence of vasculitis e.g petechiae, purpura,
uveitis
• Abdomen for bladder and obstruction
 Investigations
• Serum Creatinine and Urea
– The ratio of urea to creatinine is helpful, ie if
greater than 20:1 then consider pre-renal
– Urea can be higher in GI or mucosal bleeding,
steroid treatment, or protein loading
– As a general rule, if serum creatinine increases to
more than 1.5 mg/dL/d, rhabdomyolysis must be
ruled out
 Investigations cont.
• Blood film may show schistocytes in
conditions such as HUS or TTP
• Increased rouleaux formation suggests
multiple myeloma
• Check for ANA, ANCA, ASO, complement
levels and hepatitis can help if available
 Urine analysis
• Findings of granular muddy-brown casts are suggestive
of tubular necrosis.
• The presence of tubular cells or tubular cell casts also
supports the diagnosis of ATN
• Significant proteinuria, would suggest glomerular or
interstitial disease
• The presence of WBCs or WBC casts suggests
pyelonephritis or acute interstitial nephritis
• Presence of RBC’s if eumorphic suggest bleeding post-
renal and if dysmorphic then GN
• Uric acid crystals seen in Uric acid nephropathy
 Imaging
• ECG
– For signs of life-threatening arrythmias
• CXR
– Can help if CCF or pulmonary oedema
• Renal Ultrasound
– Check for kidney size, obstruction and cortex
Ultrasound of obstructed kidneys
 Immediate management
• Cannulate
• Bloods
• Urine analysis and culture
• Catherize and HOURLY input/output chart
• Regular blood pressure measurements
• ABG if avaliable
 Management
• Find the underlying cause
• Maintain appropriate fluid balance
– Fluids if dry
– Diuretics if wet
• Remember to use renal doses of meds
• Relieve obstruction if present
– Be prepared for diuresis post relieving
obstruction, ensure adequate fluids prescribed
 Indications for dialysis
• A - Severe acidosis, usually due to low
bicarbonate, not responding to treatment
• E – Electrolyte imbalance ie Hyperkalemia (Rx with
calcium gluconate, insulin/dextrose etc)
• I - Intoxication (methanol, ethylene glycol,
theophylline, lithium, salicylates)
• O- Fluid overload not responding to diuretics
• U- Symptomatic uremia (pericarditis,
encephalopathy, bleeding dyscrasia, nausea,
vomiting, pruritus)
 RIFLE - new classification of ARF
• R-risk of renal impairment Creatinine >1.5 x
Normal UO <0.5 mls/kg/hour for 6 hours
• I-Injury renal injury Creatinine>2 x Normal UO
<0.5 mls/kg/hour for 12 hours
• F – Failure Creatinine > 3 x Normal or >350
Anuria for 12 hours
• L –Loss complete loss of renal function for more
than 4 weeks (Needing renal replacement)
• E ESRF complete loss of function needing renal
replacement for> 12 weeks
 Case 1
• 24 year old student collapsed after running the
Kampala Marathon
• Had complained of muscle cramps during race
and these continued
• Admitted to A/E after passing a small amount
of red urine
• O/E normal BP and Pulse
• Urinalysis 2+ Protein, 4+ Blood
• Light microscopy renal tubular casts
 Investigations
• Urea 20 mmol/L
• Creatinine 350 micromol/L
• Sodium 140
• Potassium 6.1
• Calcium 2.01 mmol/l
• Phosphate 2.4 mmol/l
• Urate 500 micromol/l
• Bicarbonate 17 mmol/l
• Creatinine Kinase markedly elevated
 Diagnosis.....
• Acute renal failure secondary to
Rhabdomyolysis
• Management?
 Case 2
• A 59 year old man presents with weight loss
and night sweats.
• He had recurrent sinusitis aching joints and a
painful left ear.
• He had shortness of breath for 4 days before
and had a small amount of haemoptysis
• Has been taking brufen for the joint pains
 On Examination
• Tender over maxillary sinus and left ear drum
was inflamed.
• He appeared pale, and was hypertensive
190/100
• Bilateral fine crepitations in his lungs and his JVP
was mildly raised. He had moderate leg oedema
• Purpuric rash on his lower limbs with some
bullae
 Investigations
• Urinalysis showed 3+ Proteinuria and 3+
Blood, microscopy saw some dysmorphic red
cells
• Spot urinary protein 8g/24 hours
• Hb was low 8.8g/dl
• Urea 35 mmol/l, Creatinine 480 micromol/l
• Chest Xray showed interstitial infiltrates
• Positive ANCA
 Diagnosis
• Wegeners Granulomatosis
• Management??
Any questions?