Urethral Obstruction in Cats - Green

Question 1

What are the 2 most frequent causes of Urethral obstruction do to in cats?

Answer 1

1. Urethral plug
2. Idiopathic

Question 2

What are Urethral Calculi?

Answer 2

“Formed concretions”

95% mineral

<5% matrix

Question 3

What makes up Urethral Plugs?

What is the most common mineral component?

Answer 3

• > 50% matrix (debris)
• Struvite is the most common mineral component

Question 4

Describe the Clinical Presentation of Urethral Obstruction.

Answer 4

• Early ⇒ 12-48 hrs.
  
  • No C/S, normal BUN & serum Creatine or mild azotemia
• Advanced ⇒ 48-72 hrs
  
  • Post-renal azotemia & Oligo or anuria
• Death ⇒ 72-120 hrs. post obstruction
• Post-obstructive diuresis ⇒ 2-7 d.
  
  • Always measures the urine output for several days after to make sure the kidneys are still healthy

Question 5

What are some C/S of Early or Partial Urethral obstruction?

What other syndrome can it mimic?

Answer 5

• Stranguria
• Pollakiuria
• Hematuria
• mimics FIC

Question 6

What are some C/S of Late or Complete Urethral Obstruction?

Answer 6

• Vomiting
• Anorexia
• Lethargy
• Dehydration

Question 7

Which 2 metabolic abnormalities are major contributing factors

to mortality in blocked cats when they are severe?

Answer 7

• Hyperkalemia
• Metabolic acidosis

(Can cause cardiac arrest)

Question 8

What 2 metabolic factors contribute the most to the anorexia, lethargy & vomiting

seen in blocked cats?

Answer 8

• Progressive azotemia ⇒ Post-renal or Renal
• Hyperphosphatemia

Question 9

How does urethral obstruction cause azotemia in cats?

Answer 9

• Increased intratubular pressure
• Decreased GFR
• Decreased renal perfusion

Question 10

What’s going on during Post-Obstructive Diuresis?

Answer 10

• Self-limiting ⇒ lasts 2 - 7 d.
• Often proportional to the severity of intial azotemia
• Body is trying to excrete the retained solutes & H₂O
• A transient renal tubular defect in Na⁺ reabsorption & insensitivity to ADH occurs ⇒ a form of Diabetes Insipidous!

Question 11

Why do you generally want to perform a Cystocentesis on a Blocked cat?

Answer 11

• Therapeutic ⇒ prevents bladder rupture & buys you some time
• Diagnostic ⇒ can collect urine sample
• Makes passing the urethral catheter easier

Question 12

Which 2 drugs do you NEVER give to a FIC or Blocked Cat?

Answer 12

• NSAIDs
• Steroids

Question 13

How does severe hyperkalemia appear on an ECG?

Is this correlated to serum [K⁺]?

Answer 13

• Sinoventricular rhythm (atrial standstill) ⇒ Tented T waves, w/ P waves still present
• Not necessarily

Question 14

What 3 things will dictate your clincal approach to Complete Urethral Obstruction?

Answer 14

• Severity of Uremia
• Patient’s cardiovascular stability
• Magnitude of bladder distention

(NB: DX tests & TX must occur concurrently!)

Question 15

List the top 2 fluid choices for Blocked Cats?

Caveat?

Answer 15

• LRS & Normosol-R are best
• UNLESS pt is HyperK⁺ ⇒ than 0.9% NaCl is better

Question 16

How do you TX Hyperkalemia?

Answer 16

• Antagonize <3 effects ⇒ 10% Ca²⁺ gluconate
• Promote intra-cellular K ⇒ Dextrose + regular insulin

Question 17

What are the benefits of a decompressive cystocentesis?

Answer 17

• Life-saving
• Buys time
• May prevent bladder rupture
  
  • decreases intraluminal pressure
• Allows renal excretory fxn to resume
  
  • Increased GFR by decreasing intraluminal pressure
• May help dislodge a urethral plug
• Provides better quality urine sample for UA

Question 18

How do you perform Hydropulsion of a plug w/in the urethra?

Answer 18

• Sterile & gentle technique
• Stay sutures to stabilize the prepuce
• Extend penis caudally
• Inject sterile saline to hydropulse the plug back into the bladder

Question 19

When should you remove an indwelling urethral catheter?

Answer 19

• Relatively easy catherization
• Clear urine after flushing
• Minimally sick cat

Question 20

When should you place an indwelling catheter?

Answer 20

• Difficult catheterization
• Very bloody or cloudy urine after flushing
• Very sick cat

Question 21

Which catheters are good to use for placing an indwelling catheter?

Answer 21

5 French polyvinyl

(fewer problems w/ outflow obstruction)

(pick a soft one.. less irritating to cat)

Question 22

Why should you avoid using antimicrobials in patients w/ Indwelling Catheters?

Answer 22

UTI still will develop but the organisms will be resistant

Question 23

How much urine can you expect to be produced during Post-Obstructive Diuresis?

Answer 23

up to 20 mL/Kg/hr.

Question 24

What drug should you use to TX urethral sapsms?

Answer 24

Acepromazine

(spasmolytic)

Question 25

What drugs can you use to prevent bladder over distention & atony?

Answer 25

Bethanechol (Parasympathomimetic) &

Phenoxybenzamine (alpha-adreneric blocker)

Question 26

List the possible complications of Urethral Obstruction.

Answer 26

• Urethral spasm
• Bladder over-distention & atony

Question 27

Does a Perineal Urethrostomy prevent recurrence of FIC?

Answer 27

NO!!

Only prevents recurrence of urethral obstruction

Question 28

What are the complications of perineal urethrostomy?

Answer 28

• Bacterial UTI
  
  • Asymptomatic (often)
  • Monitor w/ periodic urine culture
• Infection-related calculi
• Urinary incontinence
• Urethral strictures