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Urinary Tract Diseases

Diagnosis and Treatment of Common Urinary Tract Diseases

Acute Kidney Injury

Causes:

Ischemia (especially medulla)

Dehydration, hypotension, shock, arterial blood clot, especially in combination with NSAIDs

Nephrotoxin (especially cortex)

Ethylene glycol, lilies (cats), grapes/raisins (dogs), heavy metals, myoglobinuria/hemoglobinuria, hypercalcemia (calciferol-containing rodenticide, vit D human skin scream), drugs (NSAIDs, AG, amphotericin B, contrast, ACE-inhibitor, vasodilator)

Infectious

Pyelonephritis, leptospirosis, lyme, leishmania

Obstructive

Neoplastic

Lymphoma, other

Diagnosis:

Signs: lethargy, inappetence, vomiting, diarrhea, polyuria → oliguria → anuria, polydipsia, seizures (profound azotemia), dyspnea (uremic pneumonitis)

Normal: 1-2ml urine/kg/hr

Polyuria: >2ml/kg/hr

Oliguria: <0.5ml/kg/hr

Anuria: <0-0.08ml/kg/hr

Exam: dehydration, uremic halitosis, oral ulcers/tongue tip necrosis, hypothermia, melena/diarrhea (uremic gastritis), tachycardia/bradycardia, systemic hypertension (SBP >150mmHg in dog or >180mmHg in cat) esp in lepto patients, cutaneous bruising, enlarged painful kidneys

Hypertension → risk of retinal or intracranial hemorrhage

Tests: biochem/CBC, urinalysis/culture, blood pressure, (infectious disease testing, radiographs, ultrasound, etc.)

U/A: isosthenuria (1.008-1.012) +/- glucosuria without hyperglycemia +/- proteinuria +/- hematuria, active sediment (WBC, RBC, granular casts, epithelial cells, CaOx crystals)

Urine culture (always): if AKI + positive culture → primary ddx is pyelonephritis

Ultrasound (variable):

Normal or enlarged kidney with normal architecture

Pyelonephritis or ureteral obstruction → renal pelvis dilation

Lymphoma → diffusely thickened cortex

Ethylene glycol → very hyperechoic, bright kidneys

CKD → small fibrotic kidneys

Acute vs. Chronic

Acute: 5-14 day onset, hyperkalemia, normal-high PCV, normal-large painful kidneys

Chronic: progressive, hypokalemia, anemia, small irregular kidneys

Both: azotemia, hyperphosphtaemia, isosthenuria, metabolic acidosis

Treatment

Goal: address fluid balance, hyperkalemia (if K+ >6mmol/L), hyperphosphatemia, nausea, gastric acid hypersecretion, nutrition, treat underlying cause (eg. antibiotics for lepto, pyelonephritis)

Hydrate patient!!!

Initially: rehydrate within 24h with isotonic fluids (maintenance + rehydration + ongoing losses) - usually 3x maintenance

Once hydrated: match/measure ins + outs q4-6h - can be up to 7x maintenance

Monitor hydration and body weight q6-12h - goal is normovolemia

Anti-emetic (maropitant, metoclorpamide, ondansetron)

Antacid (famotidine - eliminated renally, decrease dosing frequency)

Pain management

Anti-hypertensives (amlodipine preferred, diltiazem, NOT benazepril) - goal SBP ~150

Phosphate binders (sucralfate)

Nutrition (NE/E/G tube, “protein-restricted” but already protein-restricted by getting less than RER)

Worsening of AKI

Chronic Kidney Disease

Lower USG (2/3 loss of nephrons) → Azotemia (not sick, 3/4 loss) → Uremic Syndrome (sick)

Causes: Acute-on-chronic, urinary outflow obstruction, neoplasia, inflammatory/infectious (pyelonephritis, leptospirosis), immunological disorders (glomerular disease, lupus erythematosus, vasculitis/FIP), nephrotoxins, renal ischemia, nephrolithiasis, congenital (polycystic), idiopathic

Risk factors: poor BCS, PDD, cystitis, male neutered (vs. female spayed), anesthesia, dehydration

Diagnosis:

History: PU/PD, weight loss, decreased appetite, vomiting, bad breath, lethargy

PE: dehydration, pallor, oral ulcers, weight loss, small irregular kidneys, muscle condition score

Tests: CBC/biochem, urinalysis/culture, blood pressure, radiographs/ultrasound +/- biopsy

Persistent azotemia

Creatinine trend: 44-71umol/L (small dog), 71-88 (medium), 106-124 (large)

Hyperphosphatemia (reduced renal excretion)

Hypercalcemia

Metabolic acidosis (reduced hydrogen ion excretion)

Inadequate USG (<1.025 in dogs, <1.040 in cats)

+/- Non-regenerative anemia

+/- Abnormal sediment

Staging:

IRIS Classification

Classification

Stage 1

Stage 2

Stage 3

Stage 4

Creatinine

Dog

Cat

No azotemia <125 umol/L <140 umol/L

Mild 125-250 140-250

Moderate 251-440 251-440

Severe >440 >440

SDMA

Dog

Cat

<18 ug/dL <18 ug/dL

18-35 18-25

36-54 26-38

>54 >38

Clinical Signs

None, low USG

Mild or absent

Many signs possible

May signs present

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Proteinuria

UPCR

Non-Proteinuric

Borderline

Proteinuric

Dog

<0.2

0.2-0.5

>0.5

Cat

<0.2

0.2-0.4

>0.4

Recheck in 2 months

Treat

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⁠

Goal = reduce UPCR <1

Anemia - normocytic, normochromic, non-regenerative (30-65% of cats with CKD)

Hypertension (20-65% of cats, 31-54% of dogs)

Systolic BP

Normotension

Prehypertension

Hypertension

Severe hypertension

Dog and Cat

<140mmHg

140-159

160-179

180 and above

Organ Damage Risk

Minimal

Low

Moderate

High

Treat

There are no rows in this table

⁠

Goal = reduce systolic BP to <150-160mmHg + minimize risk of target organ damage

Treatment:

Short-term:

IV fluids

GI protectants

Anti-emetics - metoclopramide, ondansetron, maropitant

Antacid - famotidine, omeprazole

Mucosal protectant (if gastric ulcer) - sucralfate

Appetite stimulant - mirtazapine

Caloric intake - any diet if sick, renal diet longterm

Antihypertensive medication

ACE inhibitors - benazepril, enalapril (1st line in dogs, 2nd line in cats)

Calcium channel blocker - amlodipine besylate (1st line in cats)

Angiotensin receptor blocker - telmisartan (cats), losartan (dogs)

+/- Antibiotics

+/- Anemia treatment - eHu EPO (if PCV <20%, does not resolve on its own, clinical signs)

60-65% success rate

Adverse effects: antibody formation (30-40%), hypertension, seizure, iron deficiency, pure red cell aplasia, fever

Long-term:

SQ fluids - 75-150ml q24-48h (cat, small dog), recheck q7 days

Goal: no clinical signs + stable creatinine

Risks: hypokalemia (cervical ventroflexion, weakness), volume overload

Renal diet - restricted protein and phosphorus, start if Stage 2 or UPCR >0.4

Eukanuba: Multi Stage Renal Feline, Early Stage and Advanced Stage Canine

Hill’s: Feline and Canine k/d

Purina: NF Feline and Canine

Royal Canin: Feline and Canine Renal Support, Multifunction Diet +/- Hydrolyzed

IRIS 1-2 + NO proteinuric: Senior Consult, Mobility Support, Urinary SO Aging 7+

Phosphorus binders - if hyperphosphatemia or elevated FGF-23 and PTH but normal P

Aluminum hydroxide, lanthanum (binds cyclosporine, furosemide), sevelamer carbonate, etc. 30-60mg/kg/day in divided doses mixed with food

Goal: 0.8-1.5mmol/L (Stage 2), 0.8-1.6 (Stage 3), 0.8-1.9 (Stage 4)

Monitor serum calcium and phosphate q4-6 weeks until stable then q12 weeks

Antiproteinuric medication

ACE inhibitors - benazepril, enalapril (1st line)

Angiotensin receptor blocker - telmisartan (cats), losartan (dogs)

Goal: UPCR <1, adjust dose q4-6 weeks (ACEi +/- add ARB)

Recheck:

UPCR, creatinine, potassium, blood pressure 1-2 weeks after start

UPCR, UA, BP, albumin, creatinine, potassium 4 times/year

Feline Lower Urinary Tract Disease

Diagnosis:

Partial/No obstruction (urinary signs + NO systemic signs): Urinalysis +/- Culture, Radiographs

Complete obstruction (urinary + systemic signs, anuric, big bladder): Radiographs, CBC/Chem, Urinalysis, Culture +/- Ultrasound

53% idiopathic, 29% urolithiasis, 18% urethral plug

Treatment (Obstructed):

Urinary catheterization: soft 3.5F (or 5F) catheter

Removal: resolution of bloodwork abnormalities, diuresis, colour of urine (clear vs. bloody)

Alternatives: decompressive cystocentesis q8h (uroabdomen risk), temporary catheter

Hospitalization and IVF therapy

Analgesic: Opioid (buprenorphine, butorphanol or fentanyl) +/- NSAID (controversial)

Antispasmodic: Prazosin (ideal), Phenoxybenzamine, Acepromazine

Parasympathomimetic (if detrusor atony suspected): Bethanechol 2.5mg/cat PO q12h

Monitor renal profile + electrolytes

If relapses 3 times, consider permanent urethrostomy

Treatment (Unobstructed):

Spontaneous resolution in 2-3 days in 85% of cats

Analgesic: Opioid (buprenorphine, butorphanol or fentanyl) +/- NSAID (controversial)

Struvite Crystalliuria + Alkaline pH: 2 month diet trial (Hill’s s/d), maintenance if recurrent episode (Hill’s c/d or RC Urinary SO Calm)

Environmental Modification: several litter boxes, increase water intake, canned diet (Hill’s c/d multicare urinary or RC Urinary SO Calm), weight loss, pheromones (eg. Feliway)

Micturition Disorders

HORMONE-RESPONSIVE URINARY INCONTINENCE

Middle-aged to older spayed female dogs (lack of estrogen and urethral muscle tone)

Predisposition: spayed, large-giant breeds, tail docking, concurrent disease causing pu/pd

Diagnosis:

History, normal PE/perineal irritation, normal USG, urinalysis/culture (rule out urinary inflammation/infection, calculi) +/- radiographs/ultrasound

Treatment:

Phenylpropanolamine (alpha-adrenergic) 1.1-1.5mg/kg PO q8h (male or female)

85-90% successful in female dogs, taper dose/frequency to MED

Adverse effects: hyperexcitability, panting or anorexia, hypertension

Diethylstilbesterol 0.1-1mg total PO q24h for 3-5 days then 1-2 times/weekly

50-65% successful in female dogs, synergistic with phenylpropanolamine

Adverse effects: estrus-like signs, myelosuppression, endocrine alopecia

Estriol (alternative to diethylstilbesterol) 2mg PO q24h for 7 days then 0.5-2mg q24-48h

CONGENITAL INCONTINENCE

Ectopic ureters, vaginal stricture, pelvic bladder, patent urachus, urethrorectal/urethrovaginal fistula, female pseudohermaphroditism

ECTOPIC URETERS

Female dogs (or male cats), breed (husky, poodle, lab, fox terrier, westie, collie, corgi)

Diagnosis:

Perineum stained with urine, perivulvar dermatitis, unremarkable bloodwork, UTI (64%)

Concurrent abnormalities common: urinary incontinence, UTI, persistent paramesonephric septal remnant, hydroureter and hydronephrosis (male dogs with EU), short urethra, vaginal septum/dual vaginas, renal agenesis, renal dysplasia

Imaging: ultrasound (poor sensitivity), CT scan (91%), cystoscopy (100%)

Treatment: Reimplantation surgery (extramural) or laser removal (intramural)

REFLEX DYSSYNERGIA

Active contraction of detrusor muscle without relaxation of internal or external urethral sphincter

Large male dogs

Diagnosis:

Normal initial voiding then narrowed urine stream, spurts of urine, dribbling as walks away, difficult to express bladder but easy catheterization (functional urethral obstruction)

Neurological exam

Treatment:

Intermittent catheterization to keep bladder small

Pharmacological options:

Phenoxybenzamine, tamsulosin (alpha-adrenergic blocker)

Diazepam (muscle relaxant) or phenoxybenzamine, or both if urine stream intermittent/narrowed

Therapeutic response may require several days (catheterization may be needed)

DETRUSOR ATONY

Secondary to distension of bladder

Treatment: Bethanechol (cholinergic)

Adverse effects: salivation, lacrimation, urination, defecation

Prevention: Urinary catheterization

Urinary Tract Infection

BACTERIAL CYSTITIS:

Common in dogs (RARE in intact males - consider prostatitis)

Rare in cats (<2% except in those with CKD)

Diagnosis: Urinalysis, Urine Culture +/- Urogenital Radiographs/Ultrasound +/- Biochemistry/CBC (if anorexic, lethargic, vomiting, pu/pd, fever - consider pyelonephritis)

Treatment: Amoxicillin 11-15mg/kg PO q8h for 3-7 days +/- NSAID (if clinical)

Gram-positive: Amoxicillin, Ampicillin, Clavamox

Gram-negative: TMS, Enrofloxacin

PYELONEPHRITIS:

Diagnosis:

Systemic signs: fever, lethargy, anorexia, vomiting, pu/pd, renal pain

Bloodwork: azotemia, SDMA, peripheral neutrophilia +/- left shift

Renal ultrasound: +/- pelvic dilation, blunting of renal papilla

Rule out leptospirosis

Treatment: Fluoroquinolone or Cefpodoxime for 4-6 weeks

Monitoring:

Reassess diagnosis if no improvement in 72 hours

Recheck exam, creatinine, urinalysis, urine culture 1-2 weeks after antibiotics completed

If no clinical signs or azotemia, antibiotics not indicated for subclinical bacteriuria

Urolithiasis

LOWER URINARY TRACT CALCULI

Diagnosis:

Abdominal radiographs (urate + cystine are radiolucent), ultrasound, UA/culture

Crystals rarely clinically significant with the exception of ammonium urate crystals

Stone type: urine pH (fasted sample), shape, breed, underlying disease (UTI, PSS)

CaOx (Schnauzer), Urate (Dalmatian, Bulldog), Cystine (Dachshund, Basset Hound, Tibetan, Bulldog, Yorkie, Irish Terrier, Chihuahua, Mastiff, Rottweiler)

Acidic pH - cystine, silicate, uric acid, calcium oxalate

Alkaline pH - struvite, calcium phosphate, ammonium urate

Treatment:

Localization: kidney (incidental unless very sick) vs. bladder (medical txt unless obstructed)

Medical dissolution (struvite +/- urate, cystine):

Hill’s s/d (acidifying) or RC Urinary S/O

Antibiotics (amoxicillin or based on sensitivity) for entire course of medical dissolution

Recheck biweekly - radiograph, urinalysis (pH, USG, crystals), culture, ensure compliance

Dissolved in 8-10 weeks but continue diet for at least 1 month after calculi not visible on rad (dog) or maintain on acidifying diet lifelong (cat, Hill’s c/d)

Not effective if UTI persists or if ureterolith/nephrolith

Contraindications:

Restricted protein: pregnant/lactating, growing, after surgery

High salt: CHF, hypertension, nephrotic syndrome

High fat: pancreatitis in Miniature Schnauzers

Prevention: water consumption to keep USG below <1.020 (dog) and <1.045 (cat)

Removal:

Cystotomy vs. voiding urohydropulsion (stones < urethra, females, NOT male cats)

Prevention

Increase water intake to keep USG below <1.020 (dog) and <1.045 (cat)

Struvite:

RC Urinary S/O or Hill’s c/d lifelong in cats (not in dogs because underlying cause is UTI)

Calcium Oxalate:

Canned food, RC Urinary S/O EXCEPT Schnauzers

If hyperlipidemic → RC Low Fat S/O Index (canned)

If not hyperlipidemic → RC Urinary S/O Moderate Calorie

Hill’s w/d

Potassium citrate 40-75mg/kg PO q12h

Hypercalcemic cats: high fiber diet, vitamin B6 2mg/kg PO q24h, hydrochlorothiazide 1-2mg/kg PO q12h

Human Food:

Acceptable:

Vegetables: cabbage, cauliflower, mushrooms, green peas, radishes, white potato

Fruit: avocado, banana, grapefruit, mango, melons (cantaloupes, honeydew, watermelon), plums

Detrimental:

Meat/fish: bologna, herring, oyster, salmon, sardines

Vegetable: asparagus, baked beans, broccoli, carrots, celery, corn, cucumber, eggplant, green beans, green peppers, lettuce, spinach, sweet potatoes, tofu, tomatoes

Dairy: cheese, ice cream, milk, yogurt

Fruits: apple, apricot, cherry, most berries, lime, lemon, orange, pineapple, tangerine

Grains and nuts: corn bread, fruit cake, grits, peanut, pecan, soybean, wheat germ

UPPER URINARY TRACT CALCULI

Treatment:

Often incidental → do nothing!

Indication for treatment: infection, refractory uremic crisis, obstructive stones (damage reversible if patency restored within 7 days, 50% reversible in 2 weeks, irreversible if >4 weeks

Osmotic diuresis:

Indication: distal calculi (eg. last 2/3 of ureter), no cardiac disease, no financial restriction

Aggressive IV fluids

60ml/kg/day maintenance fluids

+ 45-75ml/kg/day of replacement fluids

+ Furosemide or Amitriptyline or Mannitol

Recheck U/S in 24h

Not very successful (8-17% of cats) - if not successful in 48h, move on!

Surgery (ureterotomy, nephrotomy, pyelotomy, salvage ureteronephrectomy)

Complications are severe and life-threatening

Minimally-invasive alternatives (extracorporeal shock wave lithotripsy, ureteral stent placement, SQ ureteral bypass (SUB), etc.)

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