Lower Urinary Tract Disease in Horses

What TWO major things can you notice on external urogenital examination in the horse?

1. Swelling/mass/conformation

2. Evidence of urine scald

What are FOUR things you should evaluate on rectal palpation for the bladder?

1. Wall thickness at trigone

2. Fill/tone

3. Reaction to pressure

4. Bladder stone

T/F: You should be able to feel both the urinary bladder and the ureters in an adult horse.

False! You CANNOT feel the ureters in the horse.

What TWO imaging modalities can be used to find things like thickened walls, masses, uroliths, and more?

Ultrasound and endoscopy

Endoscopy is used in what THREE anatomical regions?1

1. Bladder

2. Urethra

3. Urethral orifice

What are common CBC/Chem findings in lower urinary tract disease?

CBC: unremarkable

Chem: azotemia, hyperkalemia (bladder rupture + urethral obstruction)

What is a normal finding in the urine sediment of a horse?

Calcium carbonate (CaCO3) crystals

Is primary or secondary UTI more common in adult horses?s

Secondary

What are the TWO major key risks of secondary ascending infection?

Urolithiasis and bladder paralysis

What TWO things predispose to bacterial colonization?

Tissue damage and turbulent urine flow

Is UTI more likely to cause cystitis or pyelonephritis?

Cystitis

What is the difference between cystitis and pyelonephritis?

Cystitis: bladder -> LOWER UTI

Pyelonephritis: kidneys/ureters -> UPPER UTI

Stones, atopy, and sabulous inflammation are common in ——, while mephroliths, CKD, and ureteroliths are common in —-.

Cystitis

Pyelonephritis

T/F: Mixed bacterial infection is common with UTIs in horses.

True!

Name the FOUR major G- and TWO major G+ bugs causing UTIs in horses.

G-: E. Coli, Klebsiella, Enterobacter, Pseudomonas

G+: Streptococcus, Staphylococcus

What are the TWO major clinical signs of UTI?

1. Dysuria/pyuria/hematuria (+/- urine scald)

2. +/- systemic illness

What should be ran on an urinalysis?

Quantitative culture (

What are TWO lab findings on urinalysis of a UTI?

High WBCs and intracellular bacteria

What are the THREE staples of treating a UTI?

1. Identify and treat primary problem

2. Antimicrobial therapy

3. Other (bladder lavage or IVF to promote diuresis)

What should direct antimicrobial choice in a UTI?

Culture and sensitivity

What are the THREE major select drugs that are eliminated in the urine and concentrated in the kidney?

1. Trimethoprim sulfa

2. Beta lactam (Penicillin + Ceftiofur)

3. Aminoglycoside

What are the TWO major durations of antimicrobial therapy for a UTI?

Short (7-10 days) -> initial, uncomplicated

Long (>4 weeks) -> recurrent/complicated

What is the most common cause of obstructive urinary tract disease?

Name at least TWO uncommon causes.

Urolithiasis

Urogenital trauma, prolonged paraphimosis, neoplasia

List the FOUR common locations of an obstruction from most to least common and name what the obstruction is called in that region.

Bladder -> cystic calculi

Urethra -> urethral calculi

Kidney -> nephrolith

Ureter -> ureterolith

Is obstruction more common in males or females?

Males

What are FOUR major risk factors of uroliths in horses?

1. Urine retention

2. Tissue/mucosal damage

3. Excessive precipitation of CaCO3 crystals in urine

4. Increased urine alkalinity

Name and describe the TWO types of uroliths in horses and indicate prevalence.

1. Type I (most common-90%) -> spiculated, friable, yellow/green, mainly CaCO3

2. Type 2 (only 10%) -> smooth, hard, white color, CaCO3 + phosphate + Mg

What are the THREE major clinical signs of cystic and urethral stones?

1. Dysuria/pollakiuria/urine dribbling/urine scald

2. Hematuria typically after exercise

3. Colic

What is the gold standard diagnostic for cystic and urethral stones?

Cystoscopy

What is the best treatment for cystic stones?

Surgical removal (standing or GA)

How do you prevent cystic stones? (2)

1. Reduce calcium rich feed (avoid alfalfa hay)

2. Urine acidifiers (LIMITED efficacy); CHO-rich grain, ammonium chloride (unpalatable)

What is the recurrence of cystic stones? Why?

40-50% -> undetected fragments act as nidus

Why are males predisposed to urethral stones?

Narrowed urethra over ischial arch

Urethral stones often accompany ———-, so you should always check the —- with ———-.

Bladder stones

Bladder

Urethral endoscopy

How do you treat urethral stones?

Surgical removal (urethrotomy)

T/F: The same dietary modifications for bladder stones work for urethral stones and recurrence rates are also similar.

True!

What are the major complications of urethral stones?

Trauma, stricture, diverticulum, fistula

———- are often unrecognized until CKD is identified.

Nephrolithiasis/ureterolithiasis

What are the THREE risk factors for nephrolithiasis/ureterolithiasis?

1. Papillary necrosis (NSAID toxicity)

2. Pyelonephritis

3. Neoplasia

How do you diagnose nephrolithiasis and ureterolithiasis?

Ultrasound

Is treatment usually helpful in nephrolithiasis/ureterolithiasis?

What is the treatment option?

No, often unrewarding

Antimicrobials (>4 weeks) and nephrectomy

What is the difference between flaccid paralysis and turgid bladder?

Flaccid paralysis: LMN (L1-S5)

Turgid bladder: UMN (cranial to L1)

What bladder paralysis features loss of detrusor function, overflow incontinence, and an easily expressed bladder?

Flaccid paralysis

What bladder paralysis has decreased urethral resistance, increased sphincter tone, incomplete bladder emptying, and secondary overflow incontinence?

Turgid bladder

What, in general terms, is the major cause of bladder paralysis?

Neurologic dysfunction

Name THREE specific causes of primary UMN and primary LMN bladder conditions.

Primary UMN: EHV-1, EDM, spinal cord trauma

Primary LMN: cauda equina, lumbosacral trauma/osteomyelitis, neoplasia

Name FOUR non-neurologic causes of bladder paralysis.

1. Chronic/prolonged obstruction or inflammation of bladder (sabulous cystitis)

2. Bladder trauma or neoplasia

3. Idiopathic detrusor dysfunction

4. Musculoskeletal disease/pain interfering with normal urination

What are THREE clinical signs of bladder paralysis?

1. Dribbling urine (constant or when postured)

2. Urine scald

3. Localized neurologic/musculoskeletal abnormalities

T/F: Bladder paralysis can also be coupled with flaccid tail paralysis and fecal retention.

True!

What are THREE findings on endoscopy consistent with bladder paralysis?

1. Loss of bladder compliance

2. Dilated ureteral openings

3. Sabulous cystitis (also with urinalysis)

What is secondary to dysfunction in bladder emptying of any cause?

Sabulous cystitis

What features an accumulation of sediment ventrally in the bladder that adheres to and damages bladder mucosa and exacerbates detrusor function?

Sabulous cystitis

What is the most common complaint of sabulous cystitis?

Name THREE others.

Incontinence

Hind weakness, ataxia, distended bladder on palpation

How do you diagnose sabulous cystitis?

Cystoscopy

What are THREE treatments for sabulous cystitis?

1. Repeated bladder lavage

2. Broad spectrum antimicrobials

3. Anti-inflammatories

What are the THREE major anti-inflammatories used for sabulous cystitis?

1. Phenazopyridine

2. Bethanechol

3. Phenoxybenzamine

What is the prognosis with sabulous cystitis? Why?

Poor- high rate of urinary complications

What THREE things does bladder paralysis prognosis depend on?

1. Duration

2. Detrusor function

3. Sabulous present

What is the difference between good and guarded to poor bladder paralysis prognosis?

Good: acute (

What are TWO non-drug ways to treat bladder paralysis?

1. Treat underlying disease

2. Remove catheterization to empty bladder

What drug stimulates bladder emptying by increasing detrusor activity, relaxes bladder neck and external sphincter, but is often unsuccessful as there is only anecdotal evidence?

Bethanechol (cholinergic)

What drug decreases urethral sphincter tone and is best with acute onset UMN bladder with intact detrusor function?

Phenoxybenzamine (a-adrenergic antagonist)

What drug has an analgesic effect on urinary tract mucosa?

Phenazopyridine

T/F: Hematuria can be either microscopic or gross.

True!

What are TWO ways to differentiate hematuria from hemoglobin or myoglobin?

1. RBC in urine sediment

2. Urine clear with centrifugation (RBC pellet)

What can discolor urine and create false hematuria?

Oxidizing agents (cold air, snow, wood shavings)

Where does hematuria localize if seen early, throughout, or at the end of a urine stream?

Early: distal urethra

Throughout: renal, urethral, bladder

End: proximal urethra, bladder neck

What are THREE causes of hematuria?

1. Urethral rent/defect

2. Idiopathic

3. Hematuria of other origin

What are THREE examples of hematuria of other origin?

1. Exercise-associated

2. Systemic disease (sepsis)

3. Toxicities (blister beetle, NSAID)

What are THREE differentials for hematuria?

1. Urolithiasis

2. UTI

3. Neoplasia

A urethral rent can only be found in what horses?

Geldings/stallions

What are TWO clinical signs of urethral rent in stallions/geldings?

1. Hematuria (end stream)

2. +/- hemospermia in stallions

What causes a urethral rent?

Linear defect of urethral mucosa- convex surface at ischial arch spurts blood with urethral contraction

How is urethral rent diagnosed?

Timing and urethral endoscopy

—-% of urethral rents will self-resolve and stallions should be rested from breeding until resolved, but —- management can be described if persistent.

50%

Surgical (PU surgery)

T/F: Idiopathic hematuria is sudden onset and can range from self-limiting to life threatening and is a diagnosis of exclusion.

True!

Where is the origin of idiopathic hematuria?

Kidney (unilateral or bilateral)

What breed might be predisposed to idiopathic hematuria?

Arabian

T/F: Idiopathic hematuria typically has an unremarkable PE, but endoscopy can help localize bleeding and resolution may be spontaneous.

True!

What is the pathophysiology of exercise-associated hematuria?

RBCs filitered across glomerular barrier

Name THREE things that can cause exercise-associated hematuria.

Cystoliths, concussive bladder, kidney trauma

what are FOUR blood-related changes seen in systemic disease like sepsis?

1. Hemolysis/hematuria

2. Coagulopathy

3. Vasculitis

4. Thrombocytopenia

Blister beetle toxicity occurs when horses eat ———— contaminated with these bugs.

Alfalfa hay

What toxin do blister beetles possess?

Cantharidin

What are the TWO clinical signs of blister beetle toxicity?

Colic and hematuria

Name the FOUR common lab findings with blister beetle toxicity.

1. Hypocalcemia

2. Hypomagnesemia

3. Hypoproteinemia

4. Azotemia

What is the definitive diagnosis for blister beetle toxicity?

Beetles in hay + stomach and urine contents

What is the primary treatment for blister beetle toxicity?

Supportive care

What is the most common cause of uroperitoneum in foals?

Bladder rupture

T/F: Uroperitoneum in adult horses is rare and typically due to prolonged/severe obstruction from urethral or bladder stones.

True!

What is the most common cause of bladder rupture in a foal?

Parturition (trauma) or sepsis (infection)

Name TWO other causes of uroperitoneum in the foal.

1. Prolonged recumbency

2. Neurologic disruption of normal micturition (dummy foals)

What is the most common location of uroperitoneum in a foal?

Dorsal wall of bladder

How old are most foals that get uroperitoneum?

2-7 days

What are TWO other rarer causes of uroperitoneum in the foal?

Urachal infection/necrosis and ureteral rupture

What are the FOUR major clinical signs of uroperitoneum?

1. Stranguria/dysuria

2. Reduced urination

3. Depression/decreased nursing, colic

4. Distended abdomen or scrotum

What are FIVE things you might see on a uroperitoneum labwork?

1. Azotemia

2. Hyperkalemia (bradycardia/ECG abnormal)

3. Hyponatremia

4. Hypochloremia

5. Metabolic acidosis

What are THREE abdominal ultrasound findings of uroperitoneum?

1. Free, nonechogenic abdominal fluid

2. Visualize large tears (bladder/urachus)

3. Inverted U-shaped urinary bladder

What finding on abdominocentesis is diagnostic for Uroperitoneum?

Peritoneal creatinine more or equal to twice serum creatinine

Why should you culture and sensitivity + cytology a uroperitoneal abdominocentesis?

Concurrent peritonitis carries more guarded prognosis