Pathology of the kidneys and LUT Flashcards
3 functional causes of renal failure
- PRE-RENAL; compromised renal perfusion –> reduced RBF –> renal ischaemia secondary to circulatory collar or local obstruction of BVs
- INTRA-RENAL: compromised kidney function: tubular necrosis, embolic dz or ascending pyelonephritis
- POST-RENAL: obstruction of urine outflow: ascending ingection, urolithaisis , neoplasms
When does acute renal failure (ARF) occur?
when >75% renal functional capacity abruptly impaired
What happens in ARF?
- abrupt azotaemia
- retained K+ –> rapid cardiac dysryhthmias and arrest
- rentained phosphates –> binds ionised Ca (hypocalcaemia) –> mm tremors and coma
- disturbed electrolytes and reduced pH –> metabolic acidosis
- hypertension
CS - ARF
- oliguria
- anuria
Hx and CS - CRF
- PU/PD
- isothenuria
- dehydration
- wt loss
- poor coat condition
- V and inappetance
- halitosis with dribbling and oral ulceration
Gross appearance - CRF
- pale and shrunken with irregular depression of capsular surface
- excessive adhesion of capsule of capsule to underlying cortex
- thin cortex
Gross appearance - ARF
- enlarged
- softer
- redder
- smooth
Histology - CRF
- increased interstitial CT
- renal tubules absent, atrophic or compressed
- hyperplastic and hypertrophic tubules
- intraluminal protein
- thick hyalinised BM
- calcification of BVs and BM
- multiple acquired cysts
- glomerulosclerosis
- foci of interstitial lymphocytes and plasma cells
Features - endstage renal failure
- renal fibrosis is replaceent of renal parenchyma with mature fibrous tissue
- endpoint of all reparative processes. when conditions aren’t conducive for healing by regeneration
- severity = intensity of primary renal dz
- firm and distorted (contraction of fibrous scar)
Define uraemia
toxic syndrome associated with renal failure –> multisystemic CS and lesions
- ARF: rapid onset precludes renal compensation of electrolyte imbalance –> few non-renal lesions
- CRF: characteristic non-renal lesions
Outline systemic effects of uraemia
- insufficient glomerular filtration –> azotaemia –> progressive retention of nitrogenous metabolites
- concomitant tubular function failure
- plasma protein loss –> oedema
- hyperphosphataemia + secondary renal hyperparathyroidism
- reduced EPO production –> decreased stimulation of EPO maturation –> non-regenerative anaemia
- hypertension
Describe how uraemia leads to secondary renal hyperparathyroidism
When GFR hyperphosphataemia precipitates ionised calcium concentrated in serum –> decreased calcitriol activation –> decreased GIT Ca absorbed –> decreased ionised serum Ca –> PTH secretion –> Ca release by osteoclastic bone resorption –> increase renal excretion of phosphate and reabsorption of Ca –> parathyroid chief cell hyperplasia –> renal secondary hyperparathyroidism
How does nephrocalcinosis affect renal dz?
nephrocalcinosis perpetuates renal dz –> calcification of tubualr BMs, Bowman’s capsules, necrotic tubular epithelium –> gritty when cut
How does secondary renal hyperparathyroidism affect soft tissues?
causes fibrous osteodystrophy and mineralisation of soft tissues (e.g. rubber jaw)
Causes of hypercalcaemia
- secondary renal hyperparathyroidism
- primary hyperparathyroidism
- vitamin D intoxication
- hypercalcaemia of malignancy (paraneoplastic syndrome, PTHrp –> bone resorption, lymphoma or anal sac apocrine gland carcinomas or multiple myelomas)
Name 2 non-renal lesions of uraemia
- Endothelial degeneration + necrosis –> VASCULITIS with secondary thrombosis and infarction in various tissues
- CAUSTIC INJURY to epithelium of oral cavity and stomach (ulcers) consequent to production of large concentrations of ammonia after splitting of salivary gastric urea by bacteria
Describe ulcerative glossitis and stomatitis d/t uraemia
- brown foul smelling mucoid material adherent to eroded and ulcerated lingual and oral mucosa
- often bilaterally symmetrical ulceration present under tongue
Describe ulcerative and haemorrhagic colitis d/t ureamia
- horses and cattke
- large areas of colonic mucosa are often oedematous and dark-red d/t haemorrhage
List non-renal lesions of uraemia
- ulcerative glossitis and stomatitis
- ulcerative and haemorrhagic colitis
- ulcerative and haemorrhagic gastritis
- uraemic encephalopathy
- uraemic pneumonitis
- intercostal mineralisation
- fibrinous pericarditis
- arterits
Outline ulcerative and haemorrhagic gastritis d/t uraemia
- dogs, cats
- also secondary to mineralisation of gastric mucosa and submucosal arterioles
- V (black tarry stomach contents)
What is uraemic encephalopathy?
= non-renal lesion of uraemia
- white-matter spongiform degeneration
What is uraemic pneumonitis?
= non-renal lesion of uraemia
- underlying lesion –> vasculitis affecting alveolar apillaries –> increased vascular permeability
- pulmonary oedema, fibrin exudation and a mild infiltrate (macrophages, neutrophils)
- Also, patchy or diffuse pulmonary calcification –> failure to collapse, pale and gritty areas
What is intercostal mineralisaiton?
= non-renal lesion of uraemia
- clacification of subpleural CT of ICSs
WHat is fibrious pericarditis?
= non-renal lesion of uraemia
- fine granular deposits of Ca in epicardium
What is arteritis?
= non-renal lesion of uraemia
- finely granular plaques within left atrial endocardium and proximal aorta and pulmonary trunk
- arteritis in conjunction with loss of anticoagulant antithrombin 3 by glomerular leakage is conducive to formation of large mural thrombi at these sites.
How is the renal parenchyma divided proportionally?
into cortex and medulla (1:2)
T/F: porcine and bovine kidneys are multilobar but only bovine kideys have external lobation
True
Describe spp differences of renal medulla
- CAT: single renal papilla
- DOG, SHEEP, HORSES: fused crest-like papilla (renal medullary crest)
- PIG, CATTLE: multiple renal papillae
What are papillae surrounded by?
minor calyces that coalesce to form major calyces that empty into renal pelvis where urine collects before it enters the ureters
Define urineferous tubule
nephron and CD
T/F: damage to any component of the nephron –> diminished function and progressive damage to the kidney
True
In the early stages of disease, specific anatmonic components may be targeted by specific insults
True (e.g. glomeruli in IMD)
What are the portals of entry for kidney infections
- HAEMATOGENOUS: septic embolic nephritis or non-septic nephritis with infarction
- GLOMERILAR INFILTRAT
- ASCENDING FROM URETER
- DIRECT PENETRATION
Outline glomerular filtrate as a portal of entry to the kidney
- substances secreted into glomerular filtrate can produce localised trauma to tubular lining cells such as oxalate crystals
- filtered preformed toxins or metabolised substances processed by the tubular lining epithelium exert their effect principally on PCT epithelium
Outline ascrending form ureter
CONTAMINATION d/t:
- GIT content
- genital tract contamination
- dermal contamination (perivulval dermatitis)
Outline direct penetration as a portal of entry
- activation of products in PCT
- heavy metals
- crystalline oversaturation
- direct toxin action
What is the commonest kidney developmental disorder?
renal aplasia (uni or bilateral; unilateral cases can be asymptomatic)
List developmental disorders of kidneys
- RENAL APLASIA
- HYPOPLASIA
- ECTOPIC KIDNEYS
- FUSED KIDNEYS
- DYSPLASIA
- PROGRESSIVE JUVENILE NEPHROPATHY
- RENAL CYSTS
Define renal hypoplasia
incomplete development of one/both kidney (fewer than normal nephrons)
Define ectopic kidneys
pelivc canal or inguinal position –> histological structure and function usually normal byt malposition of ureters predisposes them to obstruction –> secondary hydronephrosis
What are fused kidneys
fusion of cr or cd poles –> horseshoe shape –> S+F normal
What is dysplasia?
abnormal differentiation in one/both kidneys
What is progressive juvenile nephropathy?
- familial renal dz
- Llasa apso, Shih Tzu and golden retrievers
- severe bilateral renal fibrosis
- shrunken pale kidneys, pitted surface
- foetal glomeruli, interstitial inflammation, fibrosis and tubular dilation
What are renal cysts?
= developmental disorders of kidney
- spherical thin-walled distensions of cortical or medullary tubules filled with clear fluid
- congenital secondary to renal dysplasia or acquired d/t renal interstitial fibrosis or other renal dz causing intratubular obstruction
- genetics, exposure to toxic chemicals
- as cysts enlarge, adjacent parenchyma compressed –> renal function impaired if extensive
Breeds- polycystic kidney dz
Persian cats and bull terriers
List 4 dz of glomeruli
- immune-mediated glomerulonephritis
- glomerular amyloidosis
- acute suppurative glomerulitis
- glomerulosclerosis
What does the glomerular filtration barrier consist of?
- fenestrated endothelium
- basal lamina
- pedicles of podocytes (visceral epithelium of Bowman’s capsule)
List causes of glomerular damage
- damage to filtration barrier by deposition of immune complexes
- entrapment of thromboemboli and bacterial emboli
- direct viral or bacterial infxn of glomerular components
- damage to other parts of nephron
- reduced BF
- chronic loss of tubular function
- amyloid deposition
What functions of the glomerulus might be affected in disease?
- plasma ultrafiltration
- BP regulation
- peritubular BF regulation
- tubular metabolism regulation
- circulating macromolecule removal
What is a consequence of protein losing nephropathy?
- albumin leaks into glomerular filtrate and overwhelms reabsorptibe capabilities of PCT
- protein rich glomerular filtrate accumulates in dilated tubular lumina –> proteinuria and hypoproteinaemia
- prolonged –> reduced plasma COP and loss of AT3 –> nephrotic syndrome
Characteristics - nephrotic syndrome
- generalised oedema
- ascites
- pleural effusion
- hypercoagulability
- hypercholesterolaemia
What are the responses of the glomeruli to injury?
- necrosis
- proliferation (cells and membranes)
- infiltration (leukocyte)
- reduced vascular perfusion
- increased vascular permeability (protein leakage)
- continued/ severe injury –> atrophy and fibrosis of glomerular tuft (sclerosis) and secondarily atrophy of renal tubules
Outline I-M glomerulonephritis
- criculating immune complexes may be depositied in subepithelial, subendothelial or mesangial locations
- formation of Abs against entrapped non-specific Ags or Ags within the GBM
- stimulates complement fixation –> chemotactic (neutrophils, macrophages) –>release of proteinases and O2 derived free radicals –> BM damage
- activation (glomerular epithelial and mesangial cells) to produce damaging mediators (oxidants, proteases)
What does I-M glomerulonephritis (GN) occur in association with?
- with persistent infections or other diseases with prolonged antigenaemia that enhances the formation of soluble immune complexes
- specific viruses (FeLV, FIP)
- chronic basteria (pyometra, pyoderma)
- chronic parasitism
- autoimmune dz (SLE)
- neoplasia
Effect of continual exposure of glomeruli to soluble immune complexes
Persistent infections –> progressive glomerular injury
Dx - I-M glomerulonephritis
- IF or IHC (Ig and complement in glomerular tufts)
- specific causative Ag usually undeterminable
- demonstration of electron dense deposits in mesangial, subepithelial or subendothelial locations by EM is supportive of IM-GN
Gross appearance - I-M glomerulonephritis
- glomeruli visible as pinpoint red/pale dots on cut surface of cortex
- fine granularity to cortical surface
- capsule may be adherent
Histopathology - IM-GN
- increased cellularity and proliferation (glomerular cells)
- thickening of glomerular BM and Bowman’s capsule
- deposition of fibrinous thrombi in glomerular capillaries
- dilated renal tubules filled with homegenous proteinaceous fluid
- interstitial and periglomerular fibrosis
- foci of interstitial lymphocytes and plasma cells
- glomerulosclerosis
Outline glomerular amyloidosis
- reactive amyloidosis (often associated with chronic inflammatory disorders, systemic infectious dz, neoplasia)
- amyloid deposits composed of fragments of serum APP
- glomeruli commonest renal site for deposition
- idiopathic
- Abyssinian cats and shar peis (medullary interstitium) hereditary
Consequences - glomerular amyloidosis
- PLN and nephrotic syndrome –> proteinaemia and uraemia
- decreased RBF through glomeruli and vasa recta –> tubular atrophy, degeneration, fibrosis. Severe –> renal papillary necrosis
- medullary amyloidosis usually asymptomatic unless results in papillary necrosis
Gross appearance - glomerular acidosis
- enlarged, pale, smooth to finely granular capsular surface
- amyloid laden glomeruli may be visible as fine glistening dots on cut cortex
- brown staining of glomeruli after I2 tx
- medullary amyloidosis not grossly visible
Histopathology - glomerular acidosis
- glomerular amyloid is deposited in mesangium and subendothelium
- acellular eosinophilic homogenous to fibrillar material
- secondary changes in tubules –> dilated + contain proteinaceous and cellular casts
- stains with congo red and the amyloid deposits have apple-green birefringence when viewed under polarised light
Other names - acute suppurative glomerulitis
bacterial or embolic nephritis
Describe acute suppurative glomerulitis
- Bacteraemia –> bacteria lodge in glomerular and interstitial capillaries –> microabscesses form throughout cortex.
- although glomeruli targeted –> manifestation of renal vascular dz
- bacteria produce toxic by-products –> damage endothelium –> localised vasculitis and colonisation –> embolic nephritis
CAuses - acute suppurative glomerulitis
- Actinobacillus equuli (foals)
- E. rhusiopathie (pigs)
- Corynebacterium pseudotuberculosis (sheep/goats)
- Arcanobacteirum pyogenes (cattle)
Gross appearance - acute suppurative glomerulitis
Multifocal random raised tan pinpoint foci –> subcapsular and cut surface or renal cortex
Histopathology - acute suppurative glomerulitis
- glomerular capillaries contain numerous bacterial colonies admixed with necrotic debris + neutrophils
- glomerular or interstitial haemorrhage
- can persist as focal residual abscesses or progressively replaced by chronic inflammation and coalescing scars
Define glomerulosclerosis
- decreased # functional glomeruli
- loss of glomerular capillaries and replacement of mesangial matrix and Bowman’s space by FCT
- decreased BF through vasa recta derived from glomerular efferent arteriole
- resulting hypoxia –> tubular epthelial degeneration adn loss
- chronic proteinuria
Name 2 diseases of tubules
- inherited
- acute tubular necrosis
Function - tubular BM
- prevent intraluminal organisms gaining easy access to interstitium
- scaffold for reepithelialisation of tubule which follows tubular necrosis
Causes - tubular disease
- blood borne infections
- ascending infections (intratubular pathogens)
- direct damage from toxins (intratubular effects)
- ischaemia
- infarction
- tubular obstruction
- interstitial fibrosis
- external compression
T/F: toxic and hypoxic insults to the kidney can be synergistic
True - can be hard to differentiate the two
Responses of tubules to injury
- degeneration, necrosis, apoptosis +/or atrophy –> PCT most vulnerable
- cells slough into lumen to form cellular casts
- remaining tubules undergo compensatory hypertrophy in attempt to maintain overall renal function
T/F: there is no regeneration of nephrons
True
Are tubular BMs retained more after toxic or ischaemic insults?
toxic
What happens in tubular injury if BM remains intact?
Repair by proliferation of remaining epithelial cells