Renal Flashcards
AKI
major side effect of other medical procedures, diverse spectrum of molecular, biochemical and structural processes that characterize the AKI syndrome
The RIFLE Classification of AKI
Risk for renal dysfunction –Injury to kidney –Failure of kidney function –Loss of kidney function –End stage renal disease
These classes represent degrees of injury
R = Risk for renal dysfunction I = Injury to the kidney F = Failure of kidney function
These classes represent outcome measures
L = Loss of kidney function, E = End stage renal disease (ESRD)
R = Risk for renal dysfunction
Increase in serum creatinine ≥ 1.5× baseline, Decrease in GFR ≥ 25%, UO < 0.5 mL/kg/h for 6 h
I = Injury to the kidney
Increase in serum creatinine ≥ 2.0× baseline, Decrease in GFR ≥ 50% < 0.5 mL/kg/h for 12 h
F = Failure of kidney function
Increase in serum creatinine ≥ 3.0× baseline OR serum creatinine ≥ 4.0mg/dL in the setting of an acute rise ≥ 0.5 mg/dL, Decrease in GFR ≥ 75%, < 0.3 mL/kg/h for 24 h or anuria for 12 h
L = Loss of kidney function
Persistent failure > 4 weeks
E = End stage renal disease (ESRD)
Persistent failure > 3 months
AKIN criteria
• To further refine the definition of AKI • Proposed a modified version of the RIFLE classification, known as the AKIN• An abrupt (within 48 h) reduction in kidney function as measured by an absolute increase in serum creatinine ≥ 0.3 mg/dL, • A percentage increase in serum creatinine ≥ 50%, • Or documented oliguria (
AKIN with RIFLE
AKIN replaces the three levels of severity R, I and F with stages 1, 2 and 3.
Besides Establishing the Early Diagnosis Biomarkers are needed to determine:
- Location of injury
- Duration of AKI
- AKI subtypes
- AKI etiologies
- Differentiate from other forms of acute kidney disease
- Risk stratification and prognostication
- Defining course of AKI
- Monitoring interventions
Biomarkers also used for
Also- desperately needed for use as surrogate endpoints in clinical trials evaluating potential therapeutics for AKI
validation
This linking of the surrogate endpoint to the clinical endpoint is referred to as validation and is an essential step in the biomarker discovery process
the most important AKI biomarkers remain
those that are clinically applicable and can lead to early diagnosis and treatment of AKI
prevalence of CKD in the general population
10-13% A complex disease that often affects multiple organ systems and often coexists with numerous associated conditions, such as cardiovascular disease, diabetes mellitus, lupus, & chronic inflammation
The ‘gold standard’ measurement for CKD
is the ‘true’ glomerular filtration rate (GFR) as tracked by 24-h urine isotope clearance, Method is quite expensive and not always practical in the clinical
setting
A commonly used clinical surrogate for nuclear GFR
serum creatinine clearance, the accuracy of serum creatinine is greatly affected by a number of patient dependent and -independent variables, Serum creatinine may fall to one-third of its normal level in advanced kidney disease, unrelated to its renal clearance, Serial 24-h creatinine measurements fail to determine risk progression in approximately 20% of CKD patients
CKD Definition
The presence of kidney damage or a glomerular filtration rate less than 60 mL/min/1.73 for 3 months or greater, regardless of cause However, significant increases in cardiovascular disease risk occur at
more subtle loss of kidney function (75) so it needs to be caught earlier
AKI definition
abrupt reduction in GFR –> Acumulation of nitrogenous wastes, disturbed f+e balance, and abnormal volume status. Can be polyuric, nonliguric, anuric - can do AKIN or RIFLE. Increase in sCr by 50% in 7 days, or increase by 0.3 in 2 days or oliguria
AKD
Classifies patients who may need intervention to restore kidney function or reverse kidney damage. GFR < 60 for < 3 months
Proteinuria
Shown to directly represent kidney damage and higher levels of proteinuria correlate well with a more rapid progression of kidney disease, The earliest known marker of kidney damage in glomerular diseases, diabetes and hypertension, and is the most common marker of kidney damage in the adult population Early diagnosis would entail routinely screening asymptomatic patients
However, proteinuria has limitations
May occur long after the renal injury has occurred
• Not always present in many types of renal disease
Stages of chronic kidney disease
stages 1-5.
Stage 1
Kidney damage with normal or high GFR ≥ 90 mL, increased Cr x 1.5 or > 0.3mg/dL. UO <0.5ml/kg/h x 6 h
Stage 2
Kidney damage and mild decrease in GFR 60–89, increase Cr x 2, UO < 0,5ml/kg/h x 12 h
Stage 3
Moderate decrease in GFR 30–59, increased Cr x 3 or Cr > 4, U0 < 0.3 X 24 or anuria
Stage 4
Severe decrease in GFR 15-29
Stage 5
Kidney failure, <15 or dialysis
AKI is broadly defined
as a rapid deterioration in kidney function as manifested by a reduction in GFR Comprised of a variety of syndromes that are characterized by kidney
dysfunction that occurs over hours to days it can
occur in previously healthy individuals with completely normal kidneys The most commonly employed markers of AKI are serum creatinine and BUN, both of which rise in this setting
Azotemia
A buildup of nitrogenous wastes in blood
Uremia
A constellation of symptoms and signs of multipleorgan
dysfunction caused by retention of “uremic toxins” in the setting of renal failure
Oliguric
<400 mL/day
Oligoanuric
<100 mL/day
Polyuric
> 3L/day
Anuric
none
Does AKI need specific urine output
the presence of urine output does not exclude the possibility of AKI
Most common cause of AKI
Pre Renal
Does creatitine concentration reflect a true GFR?
Because changes in serum creatinine concentration do not precisely correlate with changes in GFR, it actually
is a poor reflection of true GFR because changes in Cr does not correlate with GFR — Why: Cr is cleared through GFR and tubular secretion, drugs can compete w tubular secretion, can be falsely elevated by lab techniques, muscle is the primary source of creatine which is coverted to Cr in the liver females w low muscle mass will have a decrease
Pre Renal AKI
A decrease in GFR that occurs as a consequence of reduced renal bloodflow
Intrinsic AKI
A decrease in GFR due to direct parenchymal injury in the kidney, subdivided by various compartments (vascular, glomerular, interstitial, tubular)
Post renal AKI
a decrease in GFR from obstruction to urine flow from the pelvis to the urethra
ARF
Acute renal failure, renal impairment is sustained.
RIFLE v AKIN
Rigle is based on serum Cr, AKIN is based on serum Cr, estimated GFR and UO
AKI functional criteria
Increase in SCr by 50% within 7 days OR increase in Cr by 0.3 within 2 days OR oliguria, no structural criteria
CKD functional criteria
GFR < 60 for > 3 months, structural criteria - kidney damage for > 3 months
AKD
AKI or GFR < 60 for < 3 months or a decrease in GFR by > 35% or an increase in SCr by > 50% for < 3 months. Structural critera - kidney damage for < 3 months
NKD
GFR > 60, Stable Cr, no damage
Lab tests to identify AKI
BUN, GFR/Cr most commonly used
A abrupt increase in Serum Cr usually reflects a decline in ____, signalling the development of AKI
GFR
BUN influenced by
level of underlying renal function, slow urine flow rates, GI bleeding, protein intake, catabolic states, protein malnutrition, cirrhosis
Prerenal causes of AKI
Volume depletion, n/v, diarrhea, overdiuresis, renal salt wasting, DI, sepsis, cardiomyopathy, cirrhosis (hepatorenal syndrome), RAS, ACE, ARB, NSAIDS,
Intrarenal causes of AKI
Glomerular diseases – glomerulonephritis. acute tubular necrosis, interstitial nephritis, infection
Post renal causes of AKI
Pelvic, ureteral obstructions, kidney stones, fungus balls omg what gross, blood clots, bladder obstruction, BPH, urethral obstruction
Blood tests that can diagnose prerenal specifically
FENa (<1%), FEUrea (<35%) , RFI (<1%) DDx use a urine microscopy
Intrinsic renal disease
Anatomic compartments that have been acutely injured – vasculature, glomerulus, tubules, insterstitium
Large vessel disease leading to AKI
from a thrombosis of RAS or thromboembolism from cardiac thrombus
UTI
bacterial infection of the urinary tract, urinary frequency and urgency from spontaneous bladder contraction due to irritation of the trigone
Urinary tract is usually sterile – why
Urinary tract is normally sterile due to the fact that bacteria moving upwards are regularly washed out by urination
Types of normal flora in the urinary tract
lactobacillus and staphylococcus
Generally speaking –UTI is infections in any components linked to the urinary tract:
kidney, bladder, prostate, urethra
To make a diagnosis of UTI you must
know and start with the site –and then the nature of the infection
Normal Mechanisms that Maintain Sterility of Urine
adequate urine volume, free flow from kidneys through the urinary meatus, complete bladder emptying, normal acidity of the urine, peristalsis of ureters and competent junction, Increased intravesicularpressure preventing reflux, In males, antibacterial effect of zinc in prostatic fluid
Risk Factors of UTI - aging
Aging – increased risk of DM, urinary stasis and impaired immune response. In females: