S10.2 AKI Flashcards
Define AKI
An abrupt decline in actual GFR over days to weeks.
Disturbs ECF volume and electrolyte homeostasis.
Accumulates nitrogenous waste products
What occurs in pre-renal AKI?
Decreased kidney perfusion (renal blood flow) causes a fall in GFR
What can cause pre-renal AKI?
Decreased renal blood volume due to:
Hypovolaemia (fluid loss),
Systemic vasodilation (sepsis, cirrhosis)
Cardiac failure
What drugs can cause AKI?
NSAIDs: inhibit prostaglandins, which normally dilate the afferent arteriole
ACEi/ARB: reduce Ang II so less vasoconstriction of efferent
Both cause a drop in perfusion and GFR
What occurs in intrinsic renal AKI?
AKI caused by parenchymal disorders (within kidney)
What are the causes of renal AKI?
Acute tubular necrosis: Ischaemia (depletion of cellular ATP), nephrotoxins, sepsis.
Damaged cells unable to absorb water and salt, so fluid resuscitation risks fluid overload
Where is ischaemia more likely to occur in acute tubular necrosis?
Cortex has a better blood supply than the medulla, area between the two is relatively hypoxic so ischaemia more likely here.
Describe the histology of ATN
Glomerulus normal
Proximal tubule damaged
How do nephrotoxins cause ATN?
Nephrotoxins damage the epithelial cells lining the tubules and cause cell death.
What are the other causes of renal AKI?
Small vessel disease: thrombotic microangiopathy, where there is destruction of RBCs
Glomerular disease: lupus
Acute interstitial nephritis: toxin induced infection
Why does rhabdomyolysis cause AKI?
Due to muscle necrosis causing release of myoglobin (endogenous nephrotoxin), which is toxic to tubule epithelial cells.
What occurs in post-renal AKI?
Urinary tract obstruction
Obstruction with continued urine production increases intraluminal pressure causing dilation of the renal pelvis (hydronephrosis) and decreased renal function.
What are the causes of post-renal AKI?
Stones, blood clot, megaureter, enlarged prostate, tumour
How is AKI diagnosed by examinations?
Volume depletion shall cause tachycardia and hypotension
Volume overload shall show signs of cardiac failure
Signs of sepsis eg pyrexia
Signs of obstruction eg loin pain
How is AKI diagnosed by investigations?
Serum biochemistry: increased urea and creatinine
ECG: hyperkalaemia - tall T waves
Dip stick: high blood, proteins and leucocytes may indicate renal disease
USS: for obstruction
CXR: for infection
