L8- AKI Clinical Flashcards
What is creatinine really? how is it made? why do we measure it?
What’s the equation eh?
Creatinine is a metabolic product from muscle metabolism and we measure it to monitor GFR bc it is filtered but not absorbed or secreted by the kidney (Pcreat x GFR) = (Ucreat x V)
Formation Rate of Creatinine based on Muscle Mass
Males = 20 mg/kg-day and Females = 15 mg/kg-day
[See picture for full equation in steady state]
What happens in AKI? Why cant you use Creatinine as a renal marker?
AKI is the “Un-Steady State” and creatinine goes out of sync w/ GFR
AKI on Physical exam and history?
Pt History: Recent events reveal the cause (hypotension, nephrotoxic drugs, infection/sepsis, IV contrast, systemic disease etc)
Physical Exam: Volume status and Myocardial function
BP orthostasis, JVP, mucosal moisture, skin turgur, HR, S3, Edema est
DIAGNOSING AKI: URINALYSIS
What would you see in urinalysis in Pre-Renal Azotemia?
High specitfic gravity
non-specific sediment
[See chart]
DIAGNOSING AKI: URINALYSIS
What would you see in urinalysis in Acute TUbular Necrosis?
Isosthenuria
“Muddy Brown” granular vasts
Renal Tubular epithelial cell casts
Maybe nothing!
[see chart]
DIAGNOSING AKI: URINALYSIS
What would you see in urinalysis in Acute Interstitial Nephritis?
White blood cells
WBC casts
Eosinophiluria (Hansel stain)
Maybe nothing!
[see chart]
DIAGNOSING AKI: URINALYSIS
What would you see in urinalysis in Acute Glomerulonephritis?
Proteinuria
Nephritic Sediment
RBC cells and RBC casts
WBC cells and WBC casts possible
[see chart]
What does the kidney do in Pre-Renal Azotemia? What would you expect the FENA to be?
Kidney thinks underperfused (either relative - cirrhosis, nephrosis, CHF; or Absolute - hemorrhage, vomit etc)
Therefore it wants to expand ECF and high RAAS and high ADH
- high Urine Osmolality - water retention
- high Urine Creatinine concentration
- positive Na/Water balance
Therefore, Expect FENA to be <1 % to show that you’ve turned on RAAAS system
What is FENA? what does it mean? What is the equation?
FENA - Fraction of Filtered Load of Na excreted into the Urine
Mass flow rate into urine / mass flow rate into bowman’s capsule
[SEE PICTURE FOR EQUATION]
“2 big numbers in demoninator”
What are the 4 broad categories of insults to renal parenchyma that we discuss causing AKI?
1) ATN - mostcommon
2) AIN - mostly allergic phenomenon
3) Acute Glomerulonephritis - RPGN
4) TTP-HUS - Thrombotic Microangiopathy (remember Ecoli!)
What are the different causes of ATN?
Exogenous nephrotoxins: Aminoglycosides, Antibiotics, Amphotericin B, and Radiocontrast
Endogenous Nephrotoxins: Myoglobinuria (Rhabdo, see granular casts); Hemoglobinuria (Intravasc Hemolysis, see tubular casts); Light Chain Nephropathy (Multiple Myeloma)
Prolonged Renal Ischemia/Sepsis: hypotension, cardiac bypass, aortic cross-clamp aneurysm repair
For ATN diagnosis, what do you see in urine and biopsy?
Urinalysis: Isosthenuria, Muddy Brown granular casts
Biopsy: Flattened epithelia, mitotic figures, debris in tubular lumen
What is the classic clinical presentation of AIN?
For AIN Diagnosis, what do you see in urine and biopsy?
Presents w/ Fever, Rash, and Eosinophilia after starting new drug (like antibiotic) and creatinine rising
Urinalysis: WBCs and WBC casts, urinary Eosinophils
Biopsy: Mononuclear and inflammatory cell infiltrate, eosinophil infiltrate
What’s the difference in histopathologic presentation of ATN when ischemic vs toxic? What does AIN look like compared to that?
ATN Patchy throughout nephron when ischemic and diffuse injury to PCT when Toxic
AIN - see diffuse INTERSTITIAL inflammation
Acute Glomerular Nephritis - Rapidly progressive glomerulonephritis (RPGN)
What are the different types? Generally just list them
Good Pasture’s Syndrome - anti-GBM
Granulomatous Polyangitis (Wegner’s) - ANCA+
Microscopic Polyarteritis - ANCA+ Vasculitis
SLE - diffuse proliferative or crescentic GN - ANA+
Post-Infectious - Strep
Other diseases - membranoproliferative GN, Cryoglobulinemia etc
What is Good Pasture’s Syndrome? What does it cause? Presentation?
Biopsy?
Treatment?
Prognosis?
Anti-GBM antibody that affects lung and kidney leading to inflammation in both
Presentation: Pulmonary hemorrhage and glomerulonephritis
(men, younger, spring, smoking)
Biopsy: ***Pathognomonic Linear IMmunofluorescent staining for IgG deposition (see picture)
Treatment: Plasmaphoresis and plasma exchang, methylprednisolone, cyclophosphamide
Prognosis: poor when oliguric or creatinine >6 mg/dl
POst-Infectious RPGN - what do you see in biopsy?
typically from Strep tonsilitis
Light Micro: Mesangial Proliferation w/ PMNs
Immuno: ***LUMPY-BUMPY deposition of antibodies (see picture)
EM: ***PATHOGNOMONIC: Subepithelial hump-shaped deposits
