Topic: Acute Renal Failure(ARF) or Acute Kidney Injury(AKI) Faculty: General Medicine Course: BSc RDT - 2nd year Definition, Causes, Pathogenesis, Clinical Features, Diagnosis and Treatment of AKI/ARF

1. ACUTE RENAL FAILURE
Dr. Salman Ahmad Ansari(MBBS)
Kanachur Institute of Medical Sciences

2. ARF
● Definition
● Causes
● Pathogenesis
● Morphology
● Stages
● Clinical features
● Diagnosis, treatment

3. Anatomy
● Unit of kidney - nephron
● Nephron consists of glomerulus, tubule and collecting system
● Glomerulus is the filtering unit

7. Acute Renal Failure(ARF) or Acute Kidney Injury(AKI)
● Definition: rapid reduction of renal function,
with severe oliguria
● Usually reversible
● Now known as AKI(acute kidney injury)
● Acute Tubular Injury(ATI) is the most common
cause of acute kidney injury(acute renal failure)
● ATI →AKI/ARF

8. ● Commonly seen in hospital setting
● Very common in ICU patients

9. KDIGO criteria
According to KDIGO(Kidney Disease: Improving Global
Outcomes), AKI is the presence of any of the following:
1. Increase in serum creatinine by 0.3 mg/dL or more
within 48 hours
2. Increase in serum creatinine to 1.5 times or more
baseline within the prior seven days
3. Urine volume less than 0.5 mL/kg/h for at least 6
hours

10. Causes of AKI
Divided into 3 categories
Pre-renal
(60%)
Intra-renal
(35%)
Post-renal
(5%)

11. 1. Pre-renal
Any cause that reduces blood flow to kidney
● Fluid loss: due to blood loss, burns, diarrhoea,
vomiting
● Hypotension: shock, pulmonary embolism
● Medications which cause renal vasoconstriction:
diuretics, ACEI, ARBs, metformin, NSAIDs, iodinated
contrast

12. 2. Intra-renal
Any condition which affects the tubules or glomeruli of
kidney
● Acute tubular necrosis(ATN)
● Acute glomerulonephritis(AGN)
● Medications which cause acute interstitial
nephritis(AIN):
clavulanic acid, penicillins, NSAIDs

13. 3. Post-renal
Any obstruction to urine flow
● Renal stones
● Blocked catheter
● tumours
● BPH(benign prostatic
hyperplasia) in older men

14. Pre-renal Renal Post-renal
Fluid loss: bleeding,
burns diarrhoea,
vomiting
Acute tubular
necrosis(ATN)
Renal calculi
Hypotension: shock Acute
glomerulonephritis(A
GN)
Blocked catheter
Drugs:
● Diuretics
● ACEI/ARB
● Metformin
● NSAIDs
● Contrast dye
Acute interstitial
nephritis(AIN) due to
drugs like:
● NSAIDs
● Penicillins
● Clavulanic acid
BPH
Tumours

15. Injury to tubular epithelial cells, due to ischemia/toxins
↓
Leads to back-leakage of fluid from lumen into interstitium
↓
Damaged tubular epithelial cells detach and form casts, which blocks the lumen
↓
Block of lumen leads to: (1)increased tubular pressure, (2) decreased GFR and
(3) decreased urine flow
↓
Ischemia also causes vasoconstriction which reduces GFR and oxygen supply
to tubules
↓
Acute tubular injury
Pathogenesis of AKI
→ Acute kidney injury

16. Clinical course
3 stages:
1. Initiation phase
2. Maintenance phase
3. Recovery phase

17. Clinical course
3 stages:
1. Initiation phase
2. Maintenance phase
3. Recovery phase
● Mild ↓urine output, ↑ in BUN
● Lasts for 10-14 days

18. Clinical course
3 stages:
1. Initiation phase
2. Maintenance phase
3. Recovery phase
● ↓↓ in urine output(oliguria),
salt and water overload, rising
BUN, hyperkalemia, metabolic
acidosis and other features of
uremia
● Lasts for days to weeks

19. Clinical course
3 stages:
1. Initiation phase
2. Maintenance phase
3. Recovery phase ● Steady ↑ in urine volume
● Loss of large amounts of
water(up to 3 litres/day), Na and
K in urine(leads of hypokalemia)

20. Clinical features
● Decreased or no urine output
● Edema
● Nausea, vomiting
● Weight gain
● Shortness of breath(dyspnea)
● Hypertension
● Confusion

21. Signs:
● Edema
● Elevated JVP
● crepitations

22. Diagnosis
● ↓ urine volume
● Renal function tests(RFT): S. urea, S.creat ↑
● hyperkalemia
● eGFR: 🙅 not useful in AKI 🙅

23. Complications of AKI
● Hyperkalemia
● Metabolic acidosis
● Cardiac arrhythmias
● Seizure
● Anemia

24. Complications of AKI

25. Treatment of AKI
● AKI is often reversible
● Treatment depends upon the cause(pre/renal/post)
● Stop any nephrotoxic drugs (Mnemonic:“stop the
DAMN” drugs)
● Input/Output monitoring
● Maintain BP and urine output
● Restrict fluid intake - up to 400 ml/day
D - Diuretics
A - ACEI/ARB
M - Metformin
N - NSAIDs

26. ● Sodium balance: sodium restriction
● Potassium balance: correction of hyperkalemia by
dietary restriction or medication(using calcium chloride
or dextrose/insulin)
● Acid-base balance: i.v sodium bicarbonate
● Phosphorous balance: controlled with aluminium
hydroxide
● Diet:
- Restrict dietary protein to 40 g/day
- Restrict salt intake
- Vitamin supplements
● If no improvement, dialysis and hemofiltration

27. References:
● Archith Boloor, Ramadas Nayak - Medicine Prep
Manual for Undergraduates
● StatPearls - Acute kidney injury
Questions:
salman.s.ansari92@gmail.com
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