Urinary Flashcards
Functions of the kidney
- Eliminate metabolic waste, toxic substances, drugs
- Fluid, acid-base, electrolyte balance
- Conserve nutrients (reabsorption proteins/glucose)
- Endocrine (Renin-angiotensin-aldosterone, erythropoietin, Vit D activation, prostaglandin production)
Components of the kidney
Capsule
Cortex
Medulla
Renal papilla/crest
Renal pelvis
Hilus (ureter, renal artery, renal vein)
Function of lower urinary tract
Transport and store urine
Components of lower urinary tract
- Ureters
- Urinary bladder
- Urethra
Examples of developmental anomalies of kidney
Renal dysplasia/maldevelopment (juvenile onset of chronic kidney disease)
Polycystic kidney disease
Examples of developmental anomalies of the lower urinary tract
Patent urachus
Urachal infection/abscess
Renal dysplasia
Disorganized development of renal parenchyma
Small/misshapen kidney
Needs histo to diagnose
Polycystic kidney disease
Inherited condition with cysts in kidney
Progressive disease —> chronic renal failure
In some animals genetic mutation known (PKD1 gene) (e.g., Persian cats, Bull terrier dogs)
Also can have cysts in liver, gall bladder, pancreas
Renal cysts
Congenital or acquired
In some species, a common incidental finding
Can become inflamed/infected…
Significance varies
Urachal abnormalities
Patent urachus
Urachal abscess
Urachal diverticulum
Components of the nephron
Glomerulus + tubules
Function of glomerulus
Blood filtration
Function of tubules
Water, acid-base, electrolyte balance
Assessment of kidney function
Glomerular filtration rate
(Kidney injury —> dec GFR —> increased BUN/creatinine)
Function of juxtaglomerular apparatus
Sensor between afferent/efferent arterioles
Component of Renin-Angiotensin-Aldosterone system (produces renin in response to dec GFR)
Functions of Angiotensin II
Act on hypothalamus —> stimulate thirst
Act on pituitary —> release antidiuretic hormone —> reabsorb water
Act on adrenal glands —> aldosterone —> increase Na reabsorption (+water retention)
Overall function: increase blood volume/pressure
Tools for evaluating renal function
Clinical pathology (bloodwork/urinalysis)
Imaging (radiographs/ultrasound)
Histo pathology (biopsy, postmortem exam)
Important mechanisms of injury /dysfunction of kidney components
Glomerulus: dysfunction of glomerular filtration membrane
Interstitium/blood vessels: fibrosis
Tubules: epithelial cell necrosis
Overall: Inflammation/necrosis
Primary portals of entry to kidney
Ascending (bladder —> kidney)
Hematogenous
BUN
Blood urea nitrogen
Creatinine
Marker of GFR (aka renal function)
SMDA
Sensitive, early marker of dec GFT in dogs and cats
Azotemia
Excess urea/creatinine in blood
Uremia
Urine in blood (uremic toxins, etc)
Urine specific gravity
Measure of urine concentration
Isosthenuria
Kidney is unable to concentrate or dilute urine (“fixed” urine specific gravity)
Anuria
Kidneys cannot produce urine
Oliguria
Production of small volume of urine
Polyuria
Production of large volume of (dilute) urine
Polydipsia
Increased thirst
Renal failure
<25% of normal renal function
Causes of acute kidney injury
Neprhotoxins
Ischemia
Infectious agents
Obstruction
Clinical manifestation of acute kidney injury
Rapid onset of symptoms
Vomiting, lethargy, diarrhea
Dec urine production
Changes in bloodwork - azotemia +/- metabolic acidosis
Chronic kidney disease
Progressive decline of renal function
IRREVERSIBLE
Symptoms of chronic kidney disease
Vomiting, lethargy, diarrhea, poor body condition
Increased urination/thirst
Bloodwork changes (azotemia, anemia +/- metabolic acidosis)
Stages of chronic kidney disease
Stage 1: decreased renal reserve (subclinical)
Stage 2: renal insufficiency (25-50% of normal renal function, azotemia)
Stage 3: renal failure (<25% renal function, azotemia, uremia)
Stage 4: end-stage renal disease (<5% renal function)
Impact and Sequelae of:
Tubular or lower urinary tract injury
- Accumulation of metabolic waste
Seq: azotemia, uremia/uremic syndrome
Impact and Sequelae of:
Tubular necrosis
- Inability to maintain fluid, acid-base, electrolyte balance
Seq: dehydration, polyuria to anuria, metabolic acidosis; altered Na, K, Ca, Phosphate —> K is cardiotoxic!!
Impact and Sequelae of:
Damage to glomerular basement membrane
- loss of selectivity of blood filtration
Seq: proteinuria, glucosuria
Impact and Sequelae of:
Interstitial necrosis, inflammation, fibrosis
- Endocrine alterations
Seq: dec erythropoietin —> anemia; dec Vit D activation —> secondary hyperparathyroidism
Impact of uremic toxins
Interfere with electrolyte, protein, acid-base metabolism
Damage to endothelial/epithelial cells
Malaise (anorexia, vomiting, diarrhea)
Impact of uremia/uremic syndrome
Multi-systemic manifestation of circulating uremic toxins (due to renal failure)
Severe acid-base + electrolyte disturbances —> death
Non-renal lesions of uremia
Ulcerative stomatitis
Uremic gastritis, colitis
Uremic endocarditis (LA)
Parietal pleural mineralization
Uremic pneumonitis (alveolar walls/blood vessels mineralize)
Uremic encephalopathy (reactive astrogliosis)
Mechanism of renal secondary hyperparathyroidism
Decreased GFR —> decrease Phos excretion / inc phos in blood —> altered CaP ratio / crystallization —> low calcium
Parathyroid compensates via hyperplasia
% of cardiac output to kidney
20-25%
Renal hemorrhage
Manifestation of a systemic disease (e.g. African Swine Fever, Equine Herpesvirus-1, Canine Herpesvirus-1)
Small foci of hemorrhage/necrosis
Renal infarcts
Caused by ischemia
Wedge-shaped area of necrosis / hemorrhage
Acute: swollen, red to tan (hemorrhage, necrosis)
Chronic: depressed, firm, tan (fibrosis)
Renal papillary necrosis
Associated with NSAID administration
(NSAID—> inhibit COX enzymes —> dec local production of prostaglandins —> loss of vasodilators action —> local ischemia —> Coagulative necrosis of renal papilla/crest)
Other causes: Pyelitis/pyelonephritis, urolithiasis, amyloid
Glomerulonephritis
Inflammation of glomeruli and tubulointerstitium
Often immune-mediated; immune complex deposition (composed of antibody-antigen +/- complement)
Diagnosis by identification of IC and microscopic changes
Predisposing: disease with prolonged antigenemia +IC formation
Tubulointersitial nephritis
Inflammation of tubules + interstitium
Injury to interstitium that also impairs tubular function —> impairment of glomerular function
Sequelae: interstitial fibrosis + nephron loss (CKD)
Pyelitis/pyelonephritis
Inflammation of the renal pelvis +/- tubulointerstitium
Embolic nephritis
Hematogenous inflammation
Inflammation centered on glomeruli + bacterial emboli in capillaries
Cystitis
Inflammation of the urinary bladder
Exemplary causes of tubulointerstitial nephritis
Leptospirosis
Borrelia burgdoferi
Canine adenovirus
Ischemia
Causes / predisposing factors for Pyelitis/pyelonephritis
Ascending infection
(Actinobacillus suis, E. coli, Corynebacterium renale)
Predisposing factors: vesicoureteral reflux, urine stasis, short urethra (females)
Causes / predisposing factors for embolic nephritis
Hematogenous infection
(E. Coli, Actinobacillus equuli, E. Rhusiopathiae, disseminated fungal infections)
Predisposing conditions: sepsis, septicemia
“White spotted kidney”
Gross appearance of embolic nephritis
Causes / predisposing factors for cystitis
Possible causes: bacteria (common), toxins
Predisposing factors: damage to mucosa, incomplete emptying of bladder, diabetes
Pizzle rot
Ulcerative urethritis/posthitis due to Corynebacterium renale
Feline infectious peritonitis (FIP)
Pyogranulomatous and necrotizing vasculitis, can affect kidneys
Glomerulitis
Inflammation of glomeruli
Often associated with septicemia
Glomerulopathy/glomerulonephropathy
Glomerular injury without inflammation
Unknown cause
Components of glomerular filtration membrane
Endothelium
Glomerular basement membrane
Visceral epithelium with podocytes
Consequence of glomerular dysfunction
Proteinuria (due to non-selective filtration)
Sequelae to glomerular dysfunction
Loss of albumin (edema)
Loss of antithrombin III (hypercoaguable state)
Eventual loss of nephron (renal failure)
Response to glomerular injury
Dysfunction of glomerular filtration membrane —> endothelial, epithelial, mesangial cell proliferation —> hyper cellular tuft (seen on histo)
Glomerular basement membrane thickening
Glomerulosclerosis
Fibrosis/scarring of the glomerulus
Glomerular obsolescence
Glomerulus is shrunken, hypocellular + sclerotic
Types of glomerulonephritis
Membranous GN
Proliferative GN
Membranoproliferativ GN
Diagnosis of ICGN
Requires: clin path, histochem stains, TEM, IFA, immunohistochem
Amyloidosis
Most species glomerular - proteinuria
Medullary interstitium in cats, Shar Pei dogs
Reactive Amyloidosis
Acute tubular injury (ATI)
Causes: ischemic, toxic
Consequence of tubular dysfunction
Unmodified urine
Sequelae: polyuria/oliguria/anuria/isothenuria, metabolic acidosis, retention of metabolic waste, electrolyte imbalance, proteinuria, glucosuria
Tubular response to injury
Epithelial cell degeneration, necrosis, regeneration
Basement membrane rupture, thickening
Pigment, glycogen, and/or lipid accumulation
Response to acute tubular injury
Necrosis/sloughing of tubular epithelial cells
Downstream luminal CASTS (block filtrate flow, damage epithelium)
Regeneration of epithelial cells
Examples of nephrotoxins
Plants: lilies (cats), oak (ruminants, horses), grapes/raisins (dogs)
Drugs: increased susceptibility if prior renal disease, dehydration
Other: endogenous pigments, antifreeze
Hemoglobinuria
Nephrotoxic hemoglobin pigment in urine; by hemolysis (e.g., copper toxicosis, red maple toxicity, babesiosis, IMHA)
Two causes of injury associated with this: ischemia, cytotoxicity
Myoglobinuria
Rhabdomyolysis/extensive muscle necrosis —> myoglobin (nephrotoxic pigment) in urine
Ethylene glycol toxicosis
Ingestion of antifreeze —> metabolized by liver to toxic species
Calcium oxalate crystals in kidney —> obstruct tubules, damage epithelial cells, AKI/ATI/ATN
Non-renal lesions: crystal deposition in brain, pulmonary edema
Urolithiasis
Obstructive lower urinary tract disease (i.e. feline lower urinary tract disease)
Uroliths can form/lodge anywhere in urinary tract (not always obstructive)
Cystorrhexis
Bladder rupture
Exemplary causes: birthing trauma in male foals, secondary to obstructive urolithiasis
Sequelae: uroperitoneum
Sequelae to lower urinary tract dysfunction
Retained K (potential acute cardiac arrhythmias or arrest), retained acids, retained waste
Uroliths / calculi / stones
Concretions of urinary solutes, urinary proteins, Proteinaceous debris
Minerals predominate
Sabulous urolithiasis
Masses of sandy sludge
Organic matrix predominates
Factors involved in urolith formation
Urine pH
Hydration status
Infection
Diet
Breed
Obstructive urolithiasis
Urethral obstruction most common
Males are predisposed (long urethral length)
Common sites for obstructive urolithiasis
Cats: urethra
Ruminants, swine: sigmoid flexure
Sheep/goats: vermiform appendage
Dogs: proximal os penis
Sequeale to obstructive urolithiasis
Hyperkalemia
Mucosal hemorrhage, ulcer necrosis
Rupture
Fibrosis (chronic stricture)
Proximal distension (hydroureter, hydronephrosis)
Infection
Smooth muscle hypertrophy
FLUTD
Feline lower urinary tract disease
Clinical syndrome in young to middle aged, overweight male cats (stranguria, hematuria, inappropriate urination)
Possible causes: urolithiasis, urethral plugs (common), strictures/developmental anomalies, bacterial cystitis, feline interstitial cystitis (neurogenic), idiopathic (common)
Renal gout
In reptilian / avian species
Rate crystal deposition (rate tophi) : articular (humans), visceral (birds/reptiles)
Causes: dehydration, renal disease, overproduction of urine acid
Neoplasias of the kidney
Epithelial: renal cell carcinoma, adenoma, urothelial cell (transitional cell) carcinoma
mesenchymal: lymphoma, hemangioma/sarcoma, nephroblastoma
Metastatic: lymphoma, hemangiosarcoma
Neoplasms of the lower urinary tract
Epithelial: urothelial cell (transitional cell) carcinoma, squamous cell carcinoma, papilloma
Mesenchymal: lymphoma, hemangioma/sarcoma, leiomyoma/sarcoma, rhabdomyosarcoma
Metastatic: uncommon
Ectopic nephroblastoma
Extramedullary intramural spinal canal mass in DOGS (T10-L2)
Bovine hemangiosarcoma
Urinary bladder neoplasia associated with Bracken Fern + Bovine papilloma virus-2
