L52 Flashcards
Define acute kidney injury
Rapid ↓fxn
↑Cr + BUN
What are the 3 categories of damage that can cause AKI?
Pre-renal
Intrinsic kidney injury
Post-renal
Describe why the ↓RBF cause pre-renal failure? Explain the change to BUN, Cr?
↓GFR
Kidney is being under profused:
1. Retain Na (H2O) = ↓FE Na
2. Reabsorb BUN, Cr is not: ↑ratio
What disease is the mot common cause of intrinsic kidney injury that leads to AKI? Name the 2 possible causes.
Acute tubular necrosis -> AKI
Due to ischemia or toxins
Ischemic cause of acute tubular necrosis:
- Biopsy?
- Reversible or not?
HYPOPROFUSION
No biopsy - very typical presentation (small/no urine)
Reversible if you remove the block in time
Results in death of tubular cells that may slough into tubular lumen
What are the changes to the kidney grossly with ischemic ATN?
Large, pale kidneys
- Cortex BVs constricted b/c ↓RBF
- Medulla becomes congested with blood
What is the microscopic histo changes with ischemic ATN? Explain prox vs distal tubule changes.
Ischemic -> reversible cell damage
Cells SWELL, interstitial edema
No inflammatory cells
Some cell death, scattered (not regular like toxic cause ATN)
1. Prox tubules lose specification from swelling, “distalization”
2. Distal tubules + hyaline casts
Does urine sediment change in ischemic ATN?
No
How does the urine profile change through the initial, maintenance, and recovery phases of ischemic ATN?
Initiating: ↑Uosm, very [ ] urine indicates injury, basically excreting what gets filtered to it
Recovery: ↓Uosm as urine becomes dilute again, ↓BUN/Cr
What histo changes indicate you’re recovering from ATN?
Mitosis
Nuclear enlargement
What is the BUN:Cr ratio for intrinsic renal failure AKI?
↓BUN/Cr
BUN reabsorption is impaired b/c kidney damaged
What is diffuse cortical necrosis?
Widespread cortical infarct of BOTH kidneys
Likely due to combo do vasospasm + DIC
Think septic shock, big surg (GYN), hemorrhage: ↓renal profusion
What are exogenous toxins that can cause toxic ATN?
IV contrast scans Aminoglycosides MTX Heavy metals Cyclosporin/tacrolimus (transplant)
What are endogenous toxins that can cause toxic ATN?
Hgb (hemolytic anemia)
Myoglobin (rhabdo) - crush injury
Uric acid
HyperCa
Main differences in damage between ischemic v toxic ATN
Ischemic - patchy throughout the nephron w/ skip areas
Toxic: damage to all prox tubules
Key finding in urine for ATN
Muddy brown, granular casts
What is acute drug induced interstitial nephritis?
Pt has allergic rxn to a normal drug at kidney (vs drugs that would damage any kidney at high doses via toxic ATN)
Latent period 1-2 wks after you take drug
May be months after if took NSAIDs
Fever, rash, hematuria, CVA tenderness
What are the histo findings that indicated drug induced interstitial nephritis?
Eosinophils in the urine + ↑IgE serum
Inflam cells (nephritis)
Maybe granulomas
↑BUN (azotemia)
How does acute cell mediated allograft rejection look different on histo than drug-induced interstitial nephritis?
Allograft rejection - immune cells vs tubules
Nephritis - inflam cells in interstitium
What is acute pyelonephritis? Gross vs histo appearance
Acute infection of cortex
Gross - abscesses
PMNs in the tubules and interstitium
- WBCs in urine +/- WBC casts
2 causes pyelonephritis?
Ascending UTI (rose from bladder), GNs: - E. Coli - Proteus - Kleb & Enterobacter (urine bag on pts bed) Blood infection spread to kidneys
Clinical presentation acute pyelo
CVA tenderness
Fever
Clinical risk factors for acute pyelo
Indwelling catheter (nosocomial) Urinary tract obstruction Vesicourteteral reflex Diabetes Preggo
2 major complications of acute pyelo
Papilary necrosis - more likely if diabetic or cause was obstruction (gray/white tips of renal pyramids)
Perinephritic abscess b/c pus went through renal capsule
If a pt has vasculitis, how would it present in the kidney?
Vasculitis = fibrinoid necrosis = necrotic damage to BV wall
Proteins leak into the BV wall and stain bright pink
Do you need to get a biopsy to dx vascular processes in the kidneys for large, medium, or micro vasculature?
Microvasculature
Give examples of diseases that would cause thrombotic microangiopathy in the kidney
Vasc damage -> thrombosis -> vasc obstruction -> distal ischemia 2ary renal failure TTP (ADAM TS 13 def - can't cleave VWF) HUS (EColi O157H7) Drugs AI: SLE
What are the 2 types of glomerulonephritis that microvascular pathology can cause (via glomerular injury)
Necrotizing
Cresentic (RPGN) - see crescents of damaged Bowman’s
