11. Path of Tubular and Interstitial Diseases Flashcards
what is osmotic nephrosis? is it reversible? when is it often seen?
reversible renal tubular injury, often seen following administration of agents used to induce osmotic diuresis. considered a hydropic change (swelling, taking up of fluid)
what are the agents that can induce osmotic diuresis (leads to osmotic nephrosis)?
hypertonic agents like sucrose, mannitol, dextran, IV contrast material.
where in the kidney is osmotic nephrosis most pronounced?
prox convoluted tubules
what is the histo appearance of osmotic nephrosis?
prox tubules look pale and foamy due to accumulation of vacuoles, which distend the cytoplasm of epithelial cells. the cavuoles are distended phagolysosomes.
what is hyaline droplet change? is it reversible?
protein resorption droplets in the proximal tubular epithelial cells. reversible.
what does hyaline droplet change look like on histo?
cytoplasm of the prox tubules is finaly granular, due to accumulation of resorbed droplets of protein.
what causes hyaline droplet change? what will reverse it?
excessive protein in the tubules. seen in nephrotic patients. will disappear with the reduction of proteinuria. droplets themselves are not problematic.
what is acute kidney injury? what are the 2 most common types?
acute injury of the renal tubules that results in acute renal failure (ARF).
subtypes of AKI: ischemic, toxic.
what labs define acute renal failure (ARF)?
- acute drop in GFR
- oliguria/anuria (<400ml/24hrs)
- elevated BUN and serum creatinine
what are the 3 general types of ARF?
pre-renal
post-renal
intra-renal (interstitial, tubular most common)
ischemic AKI: when does it most often occur? reversible?
in the setting of inadequate visceral blood flow. usually with hypotension/shock. reversible
ischemic AKI: what problems are seen clinically?
- decreased Na, Cl and fluid reabsorption (elevated urine Na)
- impaired ability to concentrate urine
how can AKI lead to ARF? what is the critical event?
tubular necrosis with reduction in GFR leading to elevated BUN and serum creatinine.
what are some postulated mechanisms for how ischemic AKI leads to ARF?
overall picture: reduced GFR. possible mechs:
- backleak of filtered fluid through damaged tubule wall -> incr pressure from the outside -> collapse -> decr GFR
- tubular obstruction by casts and necrotic cells -> incr tubular lumen pressure -> decr GFR
- arteriolar vasoconstriction due to secondary to activation of RAAS (tubulo-glomerular feedback) -> decr GFR
ischemic AKI: gross appearance? what regions are most affected? what is the pattern of pathology?
swollen kidney with pale cortex, congested medulla. blood has redistributed from cortex to medulla. pattern of ischemia tends to be patchy and multifocal.
affects the prox tubule and the ascending/thick LOH.
toxic AKI: as compared to ischemic AKI, what regions are most affected? what is the pattern of pathology?
mostly prox convoluted tubule affected. tends to be more diffuse (less patchy) involvement
ischemic AKI: microscopic appearance?
simplification/distalization of the prox tubules: cells are dilated, flattened, have lost brush border, lost their integrity, disintegrated. many tubules contain epithelial cells that are sloughed off. hard to distinguish from toxic AKI via microscopic view
acute tubular necrosis: part of what process? appearance on path?
- part of ischemic or toxic acute kidney injury. -epithelial lining of tubule is disrupted, cells dislodged, sloughing into lumen. may also be flattened.
- may be clumps of necrotic, shrunken sloughed cells forming a luminal cast
- may be mitotic activity indicating regeneration.
renal infarct: part of what process? reversible? appearance on gross, appearance on histo?
extreme ischemic AKI. not reversible.
will see massive areas of yellowish/pale infarcts.
-cytoplasm of epithelial cells is intact but pale. no nuclei. capillaries congested with blood.
Toxic AKI: why is the tubular epithelium vulnerable to toxins?
- high proportion of cardiac output directed to kidney
- high concentration of toxins
- high rate of energy consumption in order to reabsorb, actively transport, concentrate urine.
what are the types of toxins that may cause acute tubular necrosis via toxic AKI?
antibiotics, solvents, metals, other….
toxic AKI: what is path appearance?
tubules are diffusely hypereosinophilic, epithelial cells are sloughing into the tubular lumens. extensive loss of epithelial cell nuclei.
clinical course of AKI/ATN: what are three phases? what occurs in each?
- initiating phase. 1-2 days. mild decr in urine output.
- maintenance phase. significant drop in urine output. salt and water overload. elevated BUN and K. metabolic acidosis.
- Recover phase. increasing urine output, decr K, BUN, creatinine.