Topic: Acute renal failure, chronic renal failure Faculty: Pathology - Medical Course: ATOT 2nd year - Acute renal failure: definition, causes, pathogenesis, morphology, clinical course, diagnosis, treatment - Chronic renal failure: definition, causes, pathogenesis, stages, clinical features, diagnosis, treatment - Renal system - charts

1. ARF, CRF
Dr. Salman Ansari
MBBS
07/03/23

2. ● ARF
● CRF
● Charts

3. ACUTE RENAL FAILURE
New name: AKI

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

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

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

7. 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 (26.5
micromoles/L 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

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

9. 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: NSAIDs, ACEI,
ARBs, iodinated contrast, metformin

10. 2. 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

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

12. 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:
● NSAIDs
● Diuretics
● Contrast dye
● ACEI/ARB
● Metformin
Acute interstitial
nephritis(AIN) due to
drugs like:
● NSAIDs
● Penicillins
● Clavulanic acid
BPH
Tumours

13. 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
↓
Luminal obstruction 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

14. Morphology
Gross
Both kidneys are swollen with a pale cortex and congested medulla
Microscopy
● Glomeruli: normal
● Tubules: focal and multiple areas of damage, most prominently in
proximal tubules and ascending limb of loop of Henle
● Interstitium: edema, leukocytes
● Blood vessels: normal
Ischemic kidney injury

15. Toxic kidney injury
Microscopy:
● Proximal convoluted tubule(PCT) is affected most commonly
● More necrosis is seen as compared to ischemic ATN
Toxic kidney
injury

16. Clinical course
3 stages:
1. Initiation phase
2. Maintenance phase
3. Recovery phase
● Mild ↓urine output, ↑ in BUN
● ↓↓ in urine output(oliguria), salt and
water overload, rising BUN,
hyperkalemia, metabolic acidosis and
other features of uremia
● Steady ↑ in urine volume
● Loss of large amounts of
water, Na and K in
urine(leads of
hypokalemia)

17. Clinical course
3 stages:
1. Initiation phase
2. Maintenance phase
3. Recovery phase
● Mild ↓urine output, ↑ in BUN
● ↓↓ in urine output(oliguria), salt and
water overload, rising BUN,
hyperkalemia, metabolic acidosis and
other features of uremia
● Steady ↑ in urine volume
● Loss of large amounts of
water, Na and K in
urine(leads of
hypokalemia)

19. Clinical features
● Decreased or no urine output
● Edema
● Nausea
● Weight gain
● Shortness of breath
● Hypertension
● Confusion

20. Diagnosis
● ↓ urine volume
● RFT: S. urea, S.creat ↑
● hyperkalemia
● eGFR: 🙅 not useful in AKI 🙅

21. Treatment
● AKI is often reversible
● Treatment depends upon the cause(pre/renal/post)
● Maintain BP and urine output
● If hypovolemic: give IV fluids
● I/O monitoring
● Hyperkalemia: treated by dietary restriction or medications(insulin)
● Stop any nephrotoxic drugs (Mnemonic:“stop the DAMN” drugs)
● If obstruction suspected: do USG abdomen and pelvis
● Dialysis
D - Diuretics
A - ACEI/ARB
M - Metformin
N - NSAIDs

22. CHRONIC RENAL FAILURE

23. CRF
● Definition
● Causes
● Pathogenesis
● Stages of CRF
● Clinical features
● Diagnosis, treatment

24. Chronic renal failure
Definition: gradual and irreversible decline in renal function due to
slow destruction of renal tissue
● Kidneys will be shrunken
● GFR less than 50% or <60 ml/min, for 3 months or more

25. Etiology
1, Diseases affecting glomerulus:
● Chronic glomerulonephritis
● diabetic nephropathy
2. Diseases affecting tubules and interstitium:
● Vascular: long-standing hypertension
● Infectious: chronic pyelonephritis
● Toxic: long-term use of nephrotoxic
drugs(aspirin, paracetamol), lead
● Obstruction: tumours, kidney stones

26. Pathogenesis
1. Damage to glomerulus leads to changes in filtration, and
development of nephrotic syndrome(proteinuria, hypoalbuminemia
and oedema)
1. Damage to tubules leads to changes in reabsorption and secretion
of important substances, leading to excretion in large amounts of
dilute urine

27. Stages of CRF
5 stages, depending upon the GFR
1. Normal: GFR: 50-100%
2. Decreased renal reserve: GFR is <50%
3. Renal insufficiency: GFR: <25%
4. Renal failure: GFR: <10%
5. End-stage kidney disease: GFR: <5%

28. Clinical features
- Renal symptoms + extra-renal symptoms
Renal symptoms:
● Metabolic acidosis: Kussmaul breathing(rapid, deep breathing)
● Hyperkalemia: weakness, nausea, cardiac arrhythmia, diarrhoea
● Sodium and water imbalance: congestive heart failure
● Hyperuricemia: uric acid crystals in joints and soft tissues - “gout”
● Azotaemia: high serum urea, creatinine

29. Non-renal symptoms:
● Anemia(due to decreased production of erythropoietin)
● Yellowing of skin
● Congestive heart failure
● Pulmonary oedema
● Renal osteodystrophy

31. Diagnosis of CKD
● CBC: anemia
● Hyperkalemia
● RFT(renal function tests): increased serum urea, serum creatinine
● eGFR(estimated GFR): reduced to <50% or <60 ml/min
● USG Abdomen and Pelvis: shrunken kidneys
● Biopsy may be needed

33. Treatment
● No cure - treatment can only slow the disease
● Lifestyle changes, “renal diet”: low salt, protein and phosphorous
● Maintain BP
● Control blood sugar in diabetics
● Treat uremia by:
● Dialysis: 2 types - hemodialysis and peritoneal dialysis
● renal transplant
Mnemonic: “LMCT” - Let Me Cure This

34. CHART - Renal system - 1
A 56 year old women is diagnosed with diabetes since 25 years. On examination, she has a
blood pressure of 168/110 mmHg. Patient appears pale. No other abnormalities identified.
Her investigations show:
Urinalysis
pH: 7.0
Spec. grav: 1.010
Proteinuria: 2+
Urine glucose: Positive
Abdominal USG shows bilateral symmetrically small kidneys
Blood
S. urea nitrogen: 71 mg/dl
Creatinine: 4.7 mg/dl
Hemoglobin: 9 mg/dl
Questions: 1) What is the most likely diagnosis? 2) Why do you say so?
3) What is the other common condition that can progress to this condition?

35. Questions: 1) What is the most likely diagnosis? 2) Why do you say so?
3) What is the other common condition that can progress to this condition?
4) Why is the patient anemic?
Answers:
1) Chronic renal failure
2) Deranged S. urea and creatinine in the presence of shrunken kidneys
3) Long-standing hypertension
4) In CRF, the kidneys are not able to produce enough erythropoietin(EPO), thus
there is decreased synthesis of RBCs, leading to anemia.

36. CHART - Renal system - 2
A 54 year old male with a history of coronary artery disease came with complaints
of increasing tiredness since last month. He also said that his abdomen was
growing larger in size and he had gained 15 kg over the past month. During the
past week he has had breathlessness and his feet have swollen. Cardiac echo
shows ejection fraction of 30%.
On physical examination, the patient is in moderate respiratory distress. BP is
140/80mmHg, pulse 95/min and RR 28/min. Body weight: 91 kg. Abdomen is
enlarged with a positive fluid wave. Lower extremities showed pitting oedema.

37. Lab data
May July 1 July 2 July 3 Normal
Sodium 130 133 134 133 136-146 mmol/L
Potassium 4.9 5.7 5.8 6.0 3.5-5.0 mmol/L
Chloride 100 90 91 93 102-109 mmol/L
BUN 20 87 94 101 7-20 mg/dl
Creatinine 0.9 3.0 3.5 3.7 0.6-1.2 mg/dl
Renal ultrasound: right kidney 10 x 5.5, left kidney 10.5 x 6.0. Both kidneys
demonstrate normal echogenicity and are without masses or cysts. There is no
hydronephrosis.

38. Questions:
1) Is the type of kidney injury acute or chronic? Why?
2) What is the cause of kidney injury in this case?
Answers:
A1) Acute kidney injury
Reasons:
- Symptoms are of short duration(1 month)
- Sudden rise in urea and creatinine levels in a short span of time
- Ultrasound shows kidneys of normal echogenicity
A2) AKI is because of his heart failure.
The ejection fraction is low(30%), which means the heart is not able to pump blood
with enough pressure to maintain the GFR. Therefore the kidneys are not able to
clear urea and creatinine from the body adequately, leading to rise of blood levels of
the same.

39. References:
● Ramadas Nayak - Textbook of Pathology for Allied
Health Sciences
● StatPearls - Acute kidney injury
● StatPearls - Chronic renal failure
Questions:
salman.s.ansari92@gmail.com
For notes, scan:
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