Acute Renal Failure - Medicine - RDT

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

4. 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

5. Commonly seen in hospital setting Very common in ICU patients

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

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

8. 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

9. 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

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

11. Pre-renal Renal Post-renal Fluid loss: bleeding, burns diarrhoea, vomiting Acute tubular necrosis(ATN) Renal calculi Hypotension: shock Acute glomerulonephritis(AGN) Blocked catheter Drugs: D iuretics A CEI/ARB M etformin N SAIDs Contrast dye Acute interstitial nephritis(AIN) due to drugs like: NSAIDs Penicillins Clavulanic acid BPH Tumours

12. 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

13. Clinical course 3 stages: Initiation phase Maintenance phase Recovery phase

14. Clinical course 3 stages: Initiation phase Maintenance phase Recovery phase M ild ↓urine output, ↑ in BUN Lasts for 10-14 days

15. Clinical course 3 stages: Initiation phase Maintenance phase 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

16. Clinical course 3 stages: Initiation phase Maintenance phase 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)

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

18. Signs: Edema Elevated JVP crepitations

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

20. Complications of AKI Hyperkalemia Metabolic acidosis Cardiac arrhythmias Seizure Anemia

21. Complications of AKI

22. 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

23. 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

24. References: Archith Boloor, Ramadas Nayak - Medicine Prep Manual for Undergraduates StatPearls - Acute kidney injury Questions: [email protected] For notes, click here or scan: For PPT, scan: