Renal Flashcards
Urinary tract infections
E.coli (Staph) usually from faeces
Urine culture and sensitivity
Antibiotics:
- Based on culture and sensitivity
- Bacteriocidal
- Excreted in urine
- No/low toxicity
- Easy and cheap
Most likely: ampicillin, potentiated amoxicillin, cefalexin, top end of dose range
Therapeutic culture if signs not improved after 3-5d
UTI
Protective factors
- Urethral high pressure zone
- Surface charcateristics of urethral urothelium
- Urethral peristalsis
- Prosthetic antibacterial fraction
- Longer urethtral length
- Ureterovesical valves
- Antibody production
- Surface GAG layer
- Intrinsic mucosal antimicrobial properties
- Bacterial interference
- Exfoliation of cells
- Extreme pH
- Hyperosmolarity
- HIgh urea
- Organic acids
UTI
Increased risk
- Urethral obstructions
- Spinal disease
- Bladder atony
- Poor husbandry
- Ectopic ureters
- Urethral sphincter mechanism incompetence
- Anatomical abnormalities following surgery e.g perineal urethrostomy
- Direct trauma e.g. urethral catheterisation
- Disease processes e.g. neoplasia
- Chemical irritants e.g. cyclophosphamide
- Older cats
- Bitches
- Diabetes mellitus
IRIS staging system
Stage 1:
- Non- azotaemic
- Normal-ish GFR
- Some other renal abnormality
Stage 2:
- Non-mildly azotaemic
- Clinical signs absent or PU/PD
Stage 3:
- Mild - moderate azotaemia
- PU/PD
- Extrarenal signs: vomiting, dehydration, weight loss may be present
Stage 4:
- > 440
- PU/PD
- Extra renal signs are likely
Causes of intrinsic renal disease in dogs and cats
Infectious:
- Dogs: pyelonephritis, leptospirosis
- Cats: pyelonephritis, FIP
Metabolic: hypercalcaemia nephropathy
Neoplastic: Primary renal tumour, lymphoma, metastatic
Congenital/familial:
- Dogs: numerous breed associated syndromes, amyloidosis
- Cats: polycystic kidney disease, amyloidosis
Other: obstructive disease, glomerulonepritis, recovery from ARF, toxins
Unidentified: tubulointerstitial nephritis
Renal secondary hyperparathyroidism
CKD
- Dietary phosphate restriction - renal diets
2. Intestinal phosphate binding drugs - mixed in food, aluminum hydroxide preparations (or lanthanum)
Glomerular hypertension and hyperfiltration
CKD
ACE inhibitors:
- Cause preferential dilation of efferent arterioles
- Reduction of glomerular capillary pressure and reduce glomerular capillary permeability to protein
- Thus reduces proteinuria prevents glomerulosclerosis development and ongoing renal injury
Hypokalaemia
CKD
20-30% cats with CKD
Treatment can lead to clinical improvement in the cats appetite and level of muscle strength and activity
Renal diets often potassium supplemented
Acidosis
CKD
Metabolic acidosis
Do not administer bicarbonate unless imbalance is well documented
Anaemia
CKD
Erythropoetin deficiency Blood loss, GI ucers, frequent blood samples, surgery Decreased RVC lifespan Uraemic inhibitors of erythropoesis Iron deficiency
Can give erythropoetin but risky!
Hypertension
CKD
Can cause acute blindness in cats
- Retinal detachment, retinal haemorrhage, hyphema
Can also cause neuron signs and cardiac changes
Oscillometric and Doppler techniques (preferred in awake patients)
Treat when >170-180mmHg and consistent ocular lesions are present
Diagnosis confirmed when two clinic trips have been made
Amlodipine in cats 0.625mg/cat/day - double if does not improve
Proximal convoluted tubule
Returns 70% of filtrate to plasma
Sodium co-transport occurs linked to:
- Glucose, amino acids
- Hydrogen ions (bicarbonate resorption)
- Phosphate
- Chloride flux (between cells)
- Water follows passively
Loop of Henle
Thick ascending limb actively transports Na, K, Cl out of tubule
Impermeable to water
Vasa recta are important in maintain concentration gradient
Distal tubule - Macula densa
Passes right next to afferent arteriole
Senses amount of chloride passing per unit time
Signals to the glomerulus - controls GFR
Functions:
- Fine regulation of urine composition
- Site of action of aldosterone - salt retaining hormone
Connecting tubule, collecting tubule and collecting duct
Sensitive to ADH:
- Increases number of water channels present in epithelium - Enhances permeability to urea
Upper urinary tract signs
PU/PD Abnormal renal palpation Oliguria/anuria Depression, lethargy Halitosis Oral ulcerations Haematuria
Lower urinary tract signs
Dysuria, polkauria Oliguria, anuria Urinary incontinence Haematuria Abnormal palpation of urethra/bladder Abnormalities of external genitalia
Catheterisation
Males:
- Extrude penis (make sure it’s straight in cat)
- Pass catheter gently via external urethral orifice - stop if resistance
- Stop once urine encountered
Females:
- Visualise using speculum
- Pass catheter into urethral orifice gently
- Can do blind
Urea and creatinine
Indicators of GFR
Urea produced in liver via urea cycle:
- Can be influenced by high protein meal, GI bleeding
- Not excreted in faeces
- Increases with dehydration
- Not a good indicator of renal function in cows - excreted in rumen and converted into ammonia - amino acids - protein production
Creatinine derived from creatine in muscle:
- More sensitive in cows and horses
- Useless in birds
- Poor in dogs and cats
- Ruptured bladder: abdominal fluid concentrations higher than serum - last longer than urea
Pre-renal azotaemia
Increased protein catabolism secondary to gastric/small bowel haemorrhage, necrosis, starvation, corticosteroid
High protein diets
Reduced renal perfusion
USG is high because ADH responds and kidney concentrate urine
Renal azotaemia
3/4 nephrons non-function (dogs)
Insufficient excretion of urea and creatinine
Post-renal azotaemia
Secondary to obstruction or post renal leakage
Oliguria, anuria
USG may vary
Urea and creatinine should return to normal once obstruction/leakage resolved
Isosthenuria
1.008-1.012
Kidney not diluting or concentrating
Hyposthenuria
Sodium
Main ion in ECF - regulated by kidney
Increased: increased intake, increased water loss or decreased water loss
Decreased: increased loss, increased water intake
Chloride
Usually coincide with changes in acid/base
Interference from bromide and iodine salts
Potassium
Main ion in ICF
Increase: renal failure especially if anuria/oliguria present (dogs and cats)
Decrease: loss (vomiting, diarrhoea, renal) and decreased intake
Calcium
In renal failure, increased amount is bound to anions
Levels regulated by PTH, vitamin D and calcitonin
Renal failure: hypo or normocalcaemic - cats, dogs and cattle
Horses: will become hypercalcaemia is major excretory route for calcium
Urine sediment
Ammonium biurate crystals
PSS
Bilirubin crystal
Most common in dog urine
No clinical importance in low numbers
Often significant in cats and horses
Calcium oxalate
(Monohydrate: ethylene glycol toxicity)
Increased incidence especially in cats - prevent struvite, promote oxalate
Breed predispositioin, males more than females, older animals, upper urinary tract
(Dihydrate: normal urine)
Surgery, urohydropropulsion, medical dissolution not possible, ignore?
Increase water
Struvite crystals
Most common type of crystals in cats and dogs
Alkaline urine pH
Often have concurrent UTI (dogs), sterile in cats
Most female, urease producing bacteria (Staph, Proteus)
Treat UTI for 3-4w
Reduce urinary magnesium, ammonium, phosphate
Can prevent with diet but is over-prescribed and can result in calcium oxalate
Calcium carbonate
Normal horse urine
Horses can also have calcium oxalate crystals in low numbers
Acute renal failure
> 75% of kidney is abruptly impaired
Abrupt increase in urea and creatinine
Retention of potassium - cardiac arrhythmias
Retention of phosphates - binds ionised calcium, muscle tremors, coma
Disturbance of electrolytes and decreased pH - metabolic acidosis
Hypertension
Oliguria/anuria
Often reversible
Non-renal lesions of uraemia
Endothelial degeneration and necrosis - vasculitis with secondary thrombosis and infarction in a variety of tissues i.e. intestinal tract
Caustic injury to epithelium of the oral cavity and stomach (ulceration) consequent to production of large concentrations of ammonia after splitting of salivary or gastric urea by bacteria
Ulcerative glossitis and stomatitis:
- Brown foul mucoid material stuck to oral mucosa
- Often bilaterally symmetrical on underside of the tongue
Ulcerative and haemorrhagic colitis - horses and cattle
Ulcerative and haemorrhagic gastritis - dogs and cats, can also occur secondary to mineralisation of the gastric mucosa and submucosal arterioles, vomiting (black tarry stomach contents)
Uraemic encephalopathy - white matter spongiform degeneration
Uraemic pneumonitis:
- Vasculitis affecting alveolar capillaries - increased vascular permeability
- Pulmonary oedema, fibrin exudation and a mild infiltrative of macrophages and neutrophils
- With uraemic pneumonitis, patchy or diffuse pulmonary calcification - failure to collapse, pale and gritty areas
Intercostal mineralisation: calcification of the subpleural connective tissue of the intercostal space
Fibrinous pericarditis
Arteritis: finely granular plaques within the left atrial endocardium and proximal aorta and pulmonary trunk
Portal of entry
Haematogenous
Glomerular infiltrate e.g. oxulate crystals, toxins
Ascending from the ureter
Direct penetration
Causes of glomerular damage
Damage to the filtration barrier by deposition of immune complexes
Entrapment of thromboemboli and bacterial emboli
Direct viral or bacterial infection of glomerular components
Damage to other parts of the nephron
Reduced blood flow
Chronic loss of tubular function
Amyloid deposition
Protein losing nephropathy
Leakage of albumin into the glomerular filtrate
Protein-rich glomerular filtrate accumulates in dilated tubular lumina - proteinuria and hypoproteinaemia
Prolonged severe renal protein loss - reduced plasma colloid osmotic pressure and loss of angiotensin III - nephrotic syndrome
- Generalised oedema
- Ascites
- Pleural effusion
- Hypercoagulability
- Hypercholesterolaemia
Immune-mediated glomerulonephritis
Immune complexes deposited in subepithelial, subendothelial or mesangial locations
Stimulates complement fixation - chemotactic for neutrophils and macrophages - release of proteineases and oxygen derived free radicals - damage the basement membrane
Persistent infections etc.
Associated with:
- Specific viral infection - FeLV and FIP
- Chronic bacterial infection
- Chronic parasitism
- Autoimmune disease such as SLE
- Neoplasia
Glomerular amyloidosis
Reactive amyloidosis - amyloid deposits are composed of fragments of a serum acute phase reactant
Idiopathic
Hereditary predisposition: Abyssinian cats and Shar Pei
PLN and the nephrotic syndrome
Acute suppurative glomerulitis
Bacterial or embolic nephritis
Bacteria lodge in glomerular and interstitial capillaries
Actinobacillus equuii (foals) Erysipelothrix rhusiopathiae (pigs) Corynebacterium pseudotuberculosis (sheep and goats) Arcanobacterium pyogenes (cattle)
Toxic by-products
Glomerulosclerosis
Decrease in number of functional glomeruli
Loss of glomerular capillaries and replacement of mesangial and Bowman’s space by FCT
Hypoxia -> tubular epithelial degeneration and loss
Chronic proteinuria
Inherited abnormalities in renal tubular function
Primary renal glucosuria:
- Norweigan Elkhounds
- Decreased ability of tubular epithelial cells
Fanconi syndrome:
- Basenji dogs - heriditory defect in tubular re-absorption of protein, glucose, phosphate, amino acids
- Can develop progressive renal insufficiency and associated renal fibrosis
Cystinuria: sex-linked inherited tubular defect in male dogs
Acute tubular necrosis
Most important cause of acute renal failure
Oliguria/anuria: leakage of filtrate across disrupted basal membrane, intratubular obstruction
Nephrotoxic pigments:
- Haemoglobinuric nephrosis: chronic copper toxicity in sheep, babesiosis in cattle, red maple toxicity in horses and AIHA in dog
- Myoglobinuria nephrosis: extensive muscle necrosis- azoturia of horses, capture myopathy of exotic/wild animals and severe trauma
- Renal threshold for re-absorption of Hg and Mg is exceeded
- Increased intraluminal concentration: increased tubular necrosis from renal ischaemia
Heavy metals: Lead - membrane or mitochondrial damage in the PCT cells
NSAIDs, fungal and plant toxins (Aspergillosis, lilies in cats, grapes and raisins, oak in cattle, oxalate containing plants), ethylene glycol (calcium oxalate crystals precipitate in renal tunular lumens), vitamin D, pet food contaminants, bacterial toxins (Clostridia in small ruminants - pulpy kidney)
Diseases of the interstitium
E.coli septicaemia - white spotted kidney Equine arteritis virus or PRRS Canine adenovirus Leptospirosis FIP
Kidney neoplasia
Primary are highly malignant
Nephroblastoma: pigs and chickens
Mesenchymal tumours: primary renal sarcomas are rare, fibromas, fibrosarcomas and haemangiosarcoma
Epithelial tumours: adenomas, carcinomas (large, usually occupy and obliterate one pole of the kidney, paraneoplastic condition), transitional cell papillomas and carcinomas
Metastatic tumours: carcinomas and sarcomas, renal lymphoma (cats and cattle)
Hydronephrosis
Dilation of the renal pelvis because of obstruction of urine outflow
If contaminated by blood borne bacteria lodging in the hydronephrosis - pus - pyonephrosis
- Corynebacterium spp., E.coli, Staphylococcus spp., Streptococcus spp., Pseudomonas aeruginosa and Arcanobacterium pyogenes
- Cow and sow - parturition, service and catheter use
- Ascending infection
Cause: congenital malformation, ureteral or urethral blockage due to urinary calculi, chronic inflammation, ureteral or urethral neoplasia, neurogenic functional disorders
Papillary necrosis
Primary:
- Prolonged/overdose NSAIDs
- Decrease prostagladin synthesis
Secondary:
- Decrease vasa recta blood flow - glomerular amyloidosis or glomerulosclerosis
- Compression of the vasa recta within the medulla - interstitial oedema or fibrosis
- Compression of the renal papilla
Development anomalies of the lower urinary tract
Ureteral aplasia and hypoplasia - obstruction - hydronephrosis
Ectopic ureters - empty in urethra, vagina or bladder neck
Patent urachus - foals, foetal urachus fails to close - direct channel between bladder and umbilicus
Lower urinary tract obstruction
Congenital: cysts, ureter aplasia or ectopic ureters
Acquired: calculi, neoplasia, trauma and inflammation, circumferential fibrosis, bladder paralysis, vaginal and uterine prolapse, Feline urologic syndrome (fine struvite crystals - sand, in a mucoid protein matrix fill the urethra)
Urolithiasis
Urinary obstruction (males) and larger calculi form (females) Local pressure necrosis and mucosal ulceration and haemorrhage Uric acid in Dalmation dogs, substances processed abnormally by the kidney (cystine or xanthine), magnesium in commercial food, vitamin A deficiency
Sites of obstruction:
- Cattle - proximal end of the sigmoid flexure
- Sheep - urethral process
- Dogs - proximal to the base of the os penis
Acute cystitis
Bacterial infection - most common cause
Uropathogenic E. coli in many spp. Corynebacterium renale in cattle and Eubacterium suis in pigs
Hydrolysis of urea by urease producing bacteria - C renale and E suis in pigs - release excessive ammonia - damage mucosa and increase urine pH
Predisposing factors:
- Urinary stasis
- Infrequent urination
- Calculi
- Catheterisation
- Prolonged antibiotic use
Neoplasia of the lower urinary tract
Epithelial tumours: transitional cell papillomas or carcinomas, SCC and adenocarcinomas
Mesenchymal tumours: leiomyomas, fibromas, lymphoma, rhabdomyosarcoma
Developmental disorders of the kidney
Renal aplasia - one or both kidneys to develop
Hypoplasia - in complete development
Ectopic kidneys - leads to secondary hydronephrosis
Fused kidneys - fusion of cranial or caudal poles
Dysplasia
Progressive juvenile nephropathy - severe bilateral renal fibrosis
Renal cysts
Ammonium urate
Dalmations: reduced conversion of uric acid to allantoin, defective transport uric acid into hepatocytes and out of the urine
Hepatic dysfunction: PSS, increased excretion of ammonia and urea
English bulldogs
Diet, allopurinol
Cystine
Renal tubular defect resulting in excess urine cystine which is poorly soluble
Middle aged dogs
Radiolucent
Medical dissolution effective but very expensive
FLUTD
FELINE LOWER URINARY TRACT DISEASE
Haematuria, stranguria, pollakiruria, dysuria Licking of penis and prepuce Inappropriate unrination Vocalisation, hiding Signs of urethral obstruction
FLUTD
Older cats
Over 10y Can usually identify underlying cause: UTI - CKD - Hyperthyroidism - Diabetes mellitus - Urolithiasis - Bladder tumours
If no UTI, identified - try imaging
FLUTD
Younger cats
Typically episodic and resolve in 3-7d unless urethral obstruction occurs
Recurrence very common
Risk factors: Persians, obesity, young, neutered, sedentary life style, dry food, stress
- Infectious agents - rarely isolated
- Viral - herpesvirus, calicivirus etc.
- Newer theories: neurogenic inflammation, deficient GAG layer, sympathetic overactivity
Treat:
Wet food, increase water intaker, reduce stress, (synthetic GAG, amitriptyline
FIRST EPISODE
- PE and history (rule out obstuction, stress)
- Urinalysis if possible - USG (high - idiopathic, stone)
- Educate owner
- Environmental changes, water fountain, wet food
- Feliway
RECURRENT
- All above
- Imaging
- If idiopathic, try GAG
- Behaviourist, butorphanol, repeat imaging
Renal diets
Reduced protein: does not protect kidneys but may reduce urea/creatinine in blood, can lead to muscle breakdown
Phosphate restriction: can have positive results but may difficult to administer
Sodium: unclear need
Acid-base status:
- Metabolic acidosis: (cats) anorexia, nausea, vomting, lethargy, weakness, muscle wasting, weight loss
- Oral bicarbonate may not work due to taste
Caloric intake:
- Supportive measures: fluids, gastroprotectants
- Slowly switch diets
- Place feeding tube
- Avoid force feeding (cats)
Omega-3 fatty acids:
- Preserve renal morphology
- Omega-6 fatty acids are detrimental
- May improve appetite
Urolithiasis
Farm
Urinary obstruction in small ruminants due to dietary imbalances:
- Generally only males show signs
- High concentrate/low roughage, high phosphate/low calcium, high magnesium, alkaline urine
- Dehydration, UTI
- Urethral processes (vermiform) in small ruminants
- Distal sigmoid flexure in cattle
- Compications: bladder rupture, urethtral ruptue, hydronephrosis
Amyloidosis
Farm
Common in cattle, associated with chronic sepsis
Inflammation drives serum amyloid A (SAA) production: glomerularopathy
Loss of glomerular function results in protein losing nephropathy
Oedema, weight loss, chronic diarrhoea
Proteinuria, hypoalbuminaemia, azotaemia
Raised serum fibrinogen, SAA, globulins
No treatment
Enzootic haematuria
Farm
Cattle and sheep grazing bracken - chronic (>12m exposure), multiple cases
Bladder wall neoplasia
Anaemia
Differentiate from haemoglobinuria
Ulcerative posthitis/vulvitis
Farm
Pizzle rot in small ruminants
Ulcerative bacterial infection of prepuce and vulva mucous membranes - Corynebacterium renale, high protein diets appear to predispose
Pain, loss of condition, decreased fertility/libido
Penicillin, NSAIDs, reduce dietary protein
Pyelonephritis
Farm and horses
Ascending infection of the urinary tract - common in renal disease
Acute: pyrexia, anorexia, depression, colic, decreased milk yield, stranguria, polyuria, haematuria, pyuria
Chronic: weight loss, colic, decreased milk yield, diarrhoea, PU, anaemia, less obvious signs of UTI
Gram negatives: coliforms, Proteus sp., Klebsiella sp., Enterobacter sp.
(Gram positive: A. pyogenes, rarely C. renale)
Protein:creatinine ratio in urine
o.4, >0.5 (cats) Proteinuric
Cause of proteinuria
Pre-glomerular
Glomerular: increased glomerular pressure
Tubular: only ever mild, can be seen in CKD
Post-glomerular: UTIs, urolithiasis
