Urethral Obstruction

Question 1

compare the male urethra to the female urethra; compare cats to dogs

Answer 1

-male urethra is longer and narrower than female so is more likely to obstruct

-cats have a longer internal urethral sphincter compared to dogs, so spasm can cause obstruction

Question 2

describe the muscular construct of the urethra

Answer 2

proximal 1/4 to 1/3 is smooth muscle and the remainder is striated

Question 3

describe the consequences/pathophysiology of urethral obstruction

Answer 3

1. leads to accumulation of urine and pressure within urethra and bladder
2. once bladder can no longer distend, pressure necrosis and mucosal cell death occurs
3. if necrosis is severe enough, bladder can rupture, leading to uroabdomen
4. increased pressure in lower urinary tract is eventually transmitted up ureters to kidneys
5. post-renal pressure exceeds glomerular filtration pressure
6. marked reduction of GFR causes decreased urine production
   -elevated BUN, creatinine, phosphorous
   -metabolic acidosis
   -marked hyperkalemia
   -postrenal azotemia, can be profound but degree of azotemia does not correlate to prognosis

Question 4

describe etiology of urethral obstruction in dogs versus cats

Answer 4

dogs: urolithiasis and neoplasia most common
-terriers, cocker spaniels, pugs predisposed to stone formation

cats:
-feline idiopathic cystitis by far most common (usually young to middle aged)
-uncommon for cats to have stones or neoplasia but possible

Question 5

describe pathogensis of feline idiopathic cystitis

Answer 5

1. stress activates sympathetic nervous system, reaulting in alterations in bladder wall
   -degradation of GAG layer of bladder urothelium
   -exposure to urine activates nociceptors
2. pain causes stress and potentiates SNS response resulting in even more pain and stress
3. mucosal inflammatory debris, mucus, cells, crystalluria organize into urethral plugs, resulting in pain and stress which causes urethral spasming
4. progression from non-obstructive (just painful) commonly to obstructive uropathy

Question 6

describe feline lower urinary tract disease (FLUTD) etiology

Answer 6

1. very common
   -feline idiopathic cystitis is most common cause
2. less common is urethral calculi or uroliths
3. even rarer are UTIs, urethral strictures, or neoplasia

Question 7

describe lifestyle triggers for urethral obstruction for cats idiopathic cystitis/FLUTD

Answer 7

1. indoor only cats
2. nervous/fearful cats
3. dry food only
4. obesity, inactivity
5. multi-cat households
6. infrequent water intake
7. not enough litter boxes
8. life event: moving, new family member (human or animal), holidays (parties)

Question 8

describe lower urinary signs

Answer 8

1. stranguria: straining to urinate
   -can be confused for constipation by owners
2. dysuria: abnormal/difficult urination
3. hematuria: grossly bloody appearance to urine
   -must differentiate from pigmenturia!
4. pollakuria: frequent small urinations
   -common in inflammatory processes
5. periuria: inappropriate urination
   -outside of box
6. other clinical signs can be very vague
   -owners may not observe straining
   -multi-cat households can be difficult to ID if someone isn’t peeing
7. spectrum from lethargy to shock
   -systemic compromise
8. vomiting is frequent concurrent clinical signs
   -increased intra-abdominal pressure and straining, also secondary to azotemia.uremia

EVERY SICK MALE CAT SHOULD HAVE HIS BLADDER PALPATED

Question 9

describe physical exam for urethral obstruction

Answer 9

1. assess cardiovascular stability FIRST
   -hyperkalemia can cause ventricular arrhythmias and bradycardia
   -may be in hypovolemic shock if vomiting
2. gentle palpation of bladder
   -obstructed: large and firm, painful, unable to express (be careful!!), overfull water balloon
   -non-obstructed: small, often empty (due to pollakuria), uncomfortable, soft, expressible (if not empty)
3. rectal exam (dogs);
   -may be able to feel stones in urethra
   -prostatic enlargement can cause urethral obstruction

Question 10

describe initial ER diagnostics for urethral obstruction

Answer 10

1. PCV/TS/lactate
2. electrolytes/blood gas: mainly looking at potassium and renal markers
3. AFAST scan:
   -abdominal free fluid? tap it!
   –diagnose uroabdomen via paired K and creatinine
   -identify urinary bladder: may see debris or stones

Question 11

describe urinalysis of a urethral obstruction

Answer 11

1. usually lots of blood and protein

2 crystalluria does not confirm presence of stones but does suggest risk

3. pH:
   - <7.0: calcium oxalate, purines, and cystine
   - >7.0 struvite
4. urine culture and susceptibility:
   -indicated because UTIs may occur secondary to stones or may induce stone formation
   -FLUTD uncommonly associated with infections though

Question 12

describe radiographs of urethral obstruction

Answer 12

be sure to get ENTIRE urethra in image!!

1. radiopaque stones: size, shape, how many, where they are
2. not usually helpful for masses unless using contrast
3. if placing indwelling urinary catheter, take radiographs AFTER to also confirm placement of catheter in urinary bladder

Question 13

describe full abdominal ultrasound for urethral obstruction

Answer 13

1. not usually needed for blocked toms
   -mostly for dogs
2. most helpful if suspect tumor of bladder or urethra (such a TCC)
3. can help identify radiolucent stones

Question 14

what is the first treatment goal for urethral obstruction?

Answer 14

treat hyperkalemia!!!

1. potassium can become extremely elevated due to decreased excretion
2. clinical consequences:
   -ECG changes:
   -variable arrhythmias: predominantly bradycardia
3. life threatening!!
   -should be first priority of initial assessment and stabilization
4. unblocking and fluids are ultimate treatment
   -this takes time, so treat in other ways to buy time from definitive intervention

Question 15

describe hyperkalemia ECG in order of what is seen (earliest to latest)

Answer 15

1. suppression of P wave amplitude
   -treat even with this most mild change!!
2. widened QRS complex
3. tented T waves
4. bradycardia
5. atrial standstill
6. ventricular tachycardia/fibrillation

Question 16

describe the drugs used to treat hyperkalemia

Answer 16

1. calcium gluconate:
   -MOA: reduced cardiac excitability by increasing RMP
   -dose: give SLOW (over 10 min)
   -does not decrease K+, is just cardioprotective while waiting for other interventions to work
2. dextrose:
   -MOA: stimulates endogenous insulin release, driving K+ into cells
   -well tolerated, least aggressive
3. insulin:
   -MOA: drives K+ into cells
   -FOLLOW WITH DEXTROSE or will make hypoglycemia
4. terbutaline:
   -stimulates Na-K-ATPase pump to drive K+ into cells
   -may induce tachycardia
5. sodium bicarbonate:
   -indirectly activates Na-K-ATPase pump to drive K+ into cells
   -reserved for refractory/severe cases

Question 17

what is next for treating urethral obstruction after treating hyperkalemia?

Answer 17

urinary catheterization; but NEED SEDATION (heavy and/or general anesthesia)

1. use pure-mu such as methadone or fentanyl optimal for analesia
2. other sedation titrated to effect and based on hemodynamic stability and comorbidities
   -dexmedetomidine if no CV instability
   -midazolam +/- ketamine or alfaxolone if heart disease or CV unstable
   -intubation and inhalant GA if necessary
3. adjust based on patient
   -consider local blocks
   -very sick may need little to no drugs

Question 18

describe decompressive cystocentesis

Answer 18

1. alleviates discomfort, gives you more time to prepare to unblock
   -pros: easier to unblock without backpressure, especially if trying to retropulse stones
   -risk: uroabdomen, infection, hemoabdomen
2. likely safe IF bladder is drained
   -unhealthy bladders at risk regardless

Question 19

describe urinary catheter placement

Answer 19

1. position in dorsal, stretch legs cranially
2. clip around prepuce/scrotum, scrub (iodine)
3. use sterile technique
4. extrude penis: apply downward pressure above and below prepuce
5. once catheter is seated. pull penis dorsally and caudally to straighten urethra
6. advance catheter while flushing to retropulse intaluminal sludge, crystals, etc,
   -the flushing is what relieves the obstruction, NOT the catheter
   -DO NOT apply heavy pressure to obstruction with catheter, you WILL tear the urethra
7. if using separate unblocking catheter, remove, place indwelling, and secure to prepuce
8. empty +/- lavage bladder
9. recover with an e collar ON!!

Question 20

describe the 4 types of urinary catheters

Answer 20

1. tom cat: rigid and can cause tissue trauma, not intended for indwelling use
2. red rubber: flexible, can be left as indwelling, cheap, requires butterfly, tape, and suture to secure
3. slippery sam: can be used to unblock and left indwelling
4. mila urinary catheter: can be used to unblock or left indwelling

Question 21

describe retrograde hydropulsion

Answer 21

1. heavy sedation and decompressive cystocentesis first
2. flush urethra with a 1:1 mixture of saline and lubricant
3. assistant places gloved finger into rectum and occludes pelvic urethra by placing firm pressure against the ischium
4. a urinary catheter is attached to a 20-35ml syringe filled with saline is inserted into urethra and advaced to site of stones
5. saline injected until pelvic urethra expands
6. assistant quickly removes pressure on pelvic urethra while you continue to quickly flush saline through catheter
7. goal is to propel saline and stones back into bladder

Question 22

what if you cannot de-obstruct the urethra or tear it?

Answer 22

1. percutaneous antegrade urethral catheterization
   -feed guidewire from bladder down urethra (wuth US or fluoro guidance) and feed u cath over wire back into bladder
2. percutaneous pigtail cystotomy tube:
   -bypass urethra
   -indwelling catheter placed through body wall into bladder

both above take skill and special equipment (specialty)

when in doubt: decompressive cysto overnight, try to unblock again next day or refer

Question 23

what if the owner cannot afford hospitalization?

Answer 23

1. successful outpatient therapy
   -decompressive cysto
   -acepromazine and analgesia
   -low-stress environment or discharge
2. not for cats with elevated creatinine

Question 24

describe in hospital management of a blocked cat

Answer 24

1. IV fluids
   -correct dehydration
   -post-obstructive diuresis: match ins with outs
2. monitor urine output and appearance closely:
   -once urine appears mostly normal and underlying cause of obstruction fixed, can remove catheter
3. usually need some degree of analgesia
   -don’t usually recommend NSAIDs due to kidnye injury during obstruction
4. do not recommend antibiotics unless have proof of active UTI contributing to obstructive process

Question 25

what if it happens again?

Answer 25

perineal urethrostomy: amputates distal penile urethra, prevents obstruction
-does not prevent FIC or non-obstructive FLUTD signs

risks: ascending bacterial cystitis, urethrostomy or urethral stricture

-owners report good long term QOL

Question 26

describe prognosis of urethral obstruction

Answer 26

1. 90-95% survival to discharge with optimal care
2. recurrence is common:
   -33% of cats have recurrent UO; reobstruction is significant cause for euthanasia bc costly
3. factors associated with increased RUO
   -older, indoor only, larger, catheter, use of phenoxybenzamine and prazosin