ACUTE KIDNEY INJURY Flashcards
What is acute kidney injury?
Spectrum of a disease starting from :
Increased creatinine
Decreased urine output
Progress to failure
what the definition of AKI?
Sudden decline in kidney functions
leading to :
Blood urea nitrogen in the kidney
creatinine with 48 H after injury
Urine output less than 0.5
Metabolites and biomarkers in urine
what are 3 basic renal processess?
Glomerular filtration
tubular reabsorption
Tubular secretion
Filters 180L per day but excrete 1-2L a day
Reabsorbs 99% water
100% glucose
99.5 Na
50% urea
Most of these occur at the proximal convoluted tubule
what are the markers for AKI?
GFR
Urine output
GFR IS better
when GFR is still above 60% , the kidney damage can be reverse
if it is 30% and below = failure and chronic impairment
Serum creatinine is better used in acute settings
what are the requirements to be diagnosed with AKI?
less than 0.5 ml urine
Oliguria ( 100-400ml in 24 hours )
Anuria ( less than 100mL in 24 hours )
Increased in serum creatinine ( 1 mg/dl ) IMPORTANT MARKER FOR KIDNEY FUNCTION
what are the causes of acute renal failure?
Acute kidney injury will lead to acute renal failure :
Prerenal (HYPOVOLEMIA)
Intrarenal ( glomerular , interstitial, tubular )
Postrenal —(Obstruction by hypertrophy or anything )
But one can lead to each other for example :
Hypovolemia ( prerenal ) will lead to ischemia in kidney ( intrarenal )
what is the relation of covid and AKI?
patients with covid 19 were twice as likely to develop AKI compared to non covid patiensts who developed AKI during the same time period in 2019 ( 56.9% ) vs 25.1% respectively
AKI appears to be a marker of covid 19 infection severity and mortality rate is higher for these patients
Various COVID-19 related effects that are thought to contribute to AKI include kidney tubular injury ( Acute tubular necrosis ) with septic shock , microinflammation , increased blood clotting and probable direct infection of kidney
most patients with covid 19 related AKI who recover continue to have low kidney function after discharge from hospital
what causes AKI prerenal?
Decreased renal perfusion without cellular injury
60% of community acquired cases ( MOST COMMON )
40% Hospital acquired cases
what causes Acute renal failure in hospital patients?
45% —> ACUTE TUBULAR NECROSIS ( ischemia, nephrotoxins by drugs or substances given to patients )—-> MOST COMMON
21% prerenal —> Congestive heart failure, volume depletion , sepsis
10% urinary obstruction
4% glomerulonephritis or vasculitis
2% AIN ( acute interstitial nephritis )
1% Atheroemboli
what causes hypovolemia ( prerenal aetiology )?
Hemorrhage, burns, dehydration (IV LOSS )
GI loss : vomiting , diarrhea ( hyponatremia ) –> cholera
Renal loss : Diuresis , hypo adrenalis, osmotic diuresis
Sequestration : Pancreatitis, peritonitis, trauma, low albumin
what causes low cardiac output ( prerenal causes )?
kidney gets 25% of CO ( SV X HR )
Myocardial disease
Valvular heart disease
pericardial disease
Tamponade
pulmonary artery hypertension
pulmonary embolus
positive pressure mechanical ventilation
what are other causes of prerenal AKI/AKF?
Renal vasoconstriction : hypercalcemia , noradrenaline, cyclosporin, amphotericin B
Systemic vasodilation : sepsis, medication, anesthesia, anaphylaxis
impairment of autoregulation : NSAIDS , ACE1
Hyperviscosity syndrome : Multiple myeloma, polycthemia rubra vera
Cirrhosis in ascites
Increases IAP
what type of urine AND SERUM? u get in cases of prerenal AKF/AKI?
during hypovolemia the body compensate by water and sodium retention forming urine with :
No casts and no cells
Concentrated ( cuz low fluid but high solutes )
FeNa less than 1%
Urine Na less than 20
SERUM will have :
high solutes, BUN ( BLOOD UREA NITROGEN) and CREATININE
what are the tubular intrinsic causes of AKI?
Acute tubular necrosis
ischemia
nephrotoxic
what are the glomerular intrinsic causes of AKI?
Glomerulonephritis (GN )
What are the interstitial intrinsic causes of AKI?
acute interstitial nephritis ( AIN )
what are the classifications of acute tubular necrosis ?
Ischemic
Nephrotoxic
what are the types of nephrotoxic acute tubular necrosis ?
Endogenous toxins :
Heme pigments ( myoglobin , hemoglobin )
Myeloma light chains
Exogenous toxins :
Antibiotics ( aminoglycosides , amphotericin B )
Radiocontrast agents
Heavy metal ( Cis platinum ( chemotherapy ), mercury, Lithium )
poisons ( Ethylene glycol )
How do we differentiate between acute tubular necrosis and prerenal?
Mainly through fraction of excreted sodium
in ATN = high sodium excreted
in prerenal = Low sodium excreted
Also
ATN = has epi cells and granular casts whereas prerenal dont
Prerenal causes improve with IVF
ATN doesnt improve
what are the pathological characteristics of ATN?
patchy necrosis
Loss of brush borders
Flattening of epithelium
Detachment of Cells
Formation of intratubular casts
Tubular dilation and obstruction
what are the two types of intrinsic glomerular AKI?
Acute glomerulonephritis
Immune glomerulonephritis
what causes acute glomerulonephritis ?
Poststrept infection
Rapidly progressive Glomerulonephritis e
what causes immune glomerulonephritis ?
Immune complex (GN )
anti- glomerular basement membrane ( GBM ) —> GOODPASTURE SYNDROME
Anti neutrophil cytoplasmic antibody associated glomerulonephritis ( ANCA associated GN ), Wegener granulomoatosis, churag strauss syndrome , microscopic polyangiitis
what are the characteristics of glomerular disease ?
Hematuria ( dysmorphic RBCS )
RBC casts , no nuclie ( in prerenal no cast, in ATN we have muddy brown GRANULAR cast) here we have RED CAST , INTERSTITIAL WOULD HAVE WHITE CAST
Lipiduria ( increased glomerular permeability )
Proteinuria ( Maybe in nephrotic range )
Fever, rash , arthralgias
Elevated ESR
Low complement levels
