Urethral Obstruction Management Journals August 2022

Veterinary Emergency and Critical Care

Aim to report clinical presentation of cats with urethral obstruction (UO) and severe anaemia (UO-A) and to describe the clinical parameters, risk factors and outcome.

Review of medical records of cats with urethral obstruction and anaemia 

Severe anaemia with need for transfusion <20% with Clinical Signs attributed to anaemia (tachycardia, hypotension, tachypnoea, prolonged CRT)

Exclusions included incomplete medical record, mild anaemia (>20) or anaemia attributed to another cause 

Unmatched controls 30 cats with UO and mild to no anaemia was randomly selected 

Treatments administered were at the clinician’s discretion.

Survivors if they were discharged alive from the hospital and non survivors if they died or were euthanized 

During the period of the study, 2132 cats were treated for urethral obstruction at our institution with 17 UO-A cases during this period this equates to an incidence of 0.8%

Signalment of UO-A: Median age - 3.8 years, DSH 16/17, 16/17 MN 

Cases in UO-A group were more likely to have experience a previous obstruction 65% vs 27% in control group

UO-A cases had a significantly longer duration of CSX median 3 days compared to UO controls of 1 day 

UO-A more likely to have gallop or murmur and statistically significant lower MAP  

Median PCV 28% for UO-a compared to 44 UO, with 7 of the UO-A cats having PCV <20 at presentation and all had a PCV <20 at time of transfusion.  3 cats did not receive a transfusion despite PCV <20%.   2 were euthanised prior to transfusion and 1 cats with PCV of 18 survived.  

TP, PCO2, K, lactate was not significantly different 

UO-A cats had a significantly higher BUN and crea conc, lower pH and more negative base excess and lower PCV 

UO-A 24x more likely to have grossly bloody urine 

Length of hospitalisation was not significantly longer with UO-A group but did have a significantly longer duration of U catheter

All UO obstruction cats survived to discharge compared to 76.5% in UO-A cats (all euthanised)


Cats were presumed to have haemorrhage into the urinary bladder as the cause of the severe anaemia.

Cases in this study UO-A group 11/17 (65%) were more likely to have been previously obstructed - contradicts another study by Lee et al J. Vet Emerg. Crit care 2006; 16(2): 104-111

Possible causes for UO-A; significantly longer duration of clinical signs compared to UO controls.  Likely that prolonged bladder wall pressure could cause more significant mucosal injury and haemorrhage.

UO-A cases more metabolically compromised.  In severe uraemia and acid base changes have been reported to contribute to platelet function abnormalities including impairment of platelet-platelet and platelet - vessel wall interactions.  These factors combined with more severe bladder mucosal injury due to previous obstruction and longer duration of clinical signs these may be additive risk factors for haemorrhage.

Length hospitalization was not significantly different between UO-A and UO groups indicating that once hydration and anaemia corrected the cats stabilize quickly.

The findings that urinary catheterization was longer in UO-A cats is not surprising as most clinicians leave U cath in place until urine is grossly clear.  

Mortality greater in UO-A cats 23.5% .  Cases much higher than in previous reports of cats with UO in which mortality ranged from 5.8% to 8.9% 


Retrospective  and Small sample size 

Critical Care

Double blinded placebo-controlled study to determine whether prazosin administration following urethral obstruction (UO) reduces the risk for repeat UO (rUO) and lower urinary tract signs.  An additional aim was to document the adverse effects associated with prazosin administration.

Materials and Methods

Case selection: Male cats hospitalized with UO 

Exclusion criteria: Chronic kidney failure, persistent hypotension (i.e. systolic BP <90mmHg) cardiac disease, or prior to treatment with beta blockers, ACEI, diuretics, prazosin or phenoxybenzamine , owner cannot manage oral medication and an ultrasound with shadowing structures which were presumed to be uroliths >2mm in diameter.

All cats elected had a standard treatment protocol.

Cats randomized into double blinded fashion to receive either prazosin (0.25mg/cat PO q12hr) or placebo (1 capsule PO q12hr) for 30 days.

1 month study of medication period was chosen based on prior studies that reported a median time to rUO of 17 days and a median time to recurrence of lower urinary tract signs within 18 days of hospital discharge.

After hospital discharge, medical records were reviewed for each cat with specific attention paid to the occurrence of previous episodes of UO or lower urinary tract signs ,the type of housing (i.e. indoor, outdoor or indoor and outdoor) , the type of diet (i.e. canned/dry or both) the vaccine status, the number of litter trays in the home and the number of other cats in the household.

Cat’s age, weight , BCS blood gas, size of urinary catheter and duration of hospitalization were recorded.

Standard discharge instructions - litter trays ( = no. of cats in house + 1 ) and litter tray hygiene , strategies for increasing water consumption (Eg circulating water fountains and wet food only diet ) .  Prescription feline urinary tract diet were made on a case-by-case basis depending on the presence or absence of crystalluria in the initial urine sample.

Follow up once weekly for 1 month and then at 6 months. 

Standard questionnaire - owner compliance with meds, observation of adverse effects from medication administration evidence of lower urinary tract signs (1-5) frequency and duration of these signs, any diet or environmental modifications or rUO or surgical interventions or death or euthanised as a result of rUO of FLUTD 


47 cats - 20 placebo and 27 in prazosin groups 

No significant differences between the demographics of cats in the prazosin groups and cats in the placebo group with regard to age, weight, BCS, vaccination, environment, no. of litter trays, number of other cats in household or previous episodes of UO

The prazosin group was more likely to have had a previous episode of FLUTD 44% compared to 10% with placebo group 

The prazosin group had a significantly shorter than the median duration of urinary catheterization and hospitalization for the placebo group 32 hr and 37 hr vs 39 hr and 46 hr respectively.

3 cats developed rUO prior to hospital discharge - 2 cats in the prazosin grp and 1 cat in the placebo group 

4 additional cats 2 in prazosin groups and 2 cats in the placebo group developed rUO in the 1 month study period. 

1 month rUO rate of cats in the prazosin grp was 15% (4/26) while the rUO rate in cats in placebo grp was 17% (3/18)

6 month follow up 25 cats available: 4 rUO (3 prazosin grp and 1 placebo grp) developed rUO at 34, 48, 155 and 180 days following the initial UO 

In cats with complete follow up information at 6 months the total rUO rate was 37% (7/19) in the prazosin grp and 31% (4/13) in the placebo grp 

All owners reported the presence of lower urinary tract signs in cats in both the prazosin and placebo groups at the 1 week follow up, ranging in severity from1 (mild straining) to 5 (continual straining ) but the median score was not significantly different around cats in the prazosin grp (median score 2.25) and placebo (median score 2.0)

There was no difference in severity of these clinical signs between groups as reported by cat owners.


Failed to find a difference in the rate of rUO but the study was underpowered.

Cats receiving prazosin shorter duration of catheter time 

The 7 cats in the prazosin grp that were reported to receive less than 50% of the medication did not experience rUO during the 1 month study medication period 

The most commonly reported adverse effects in the prazosin treated cats included lethargy, diarrhea , malodorous stool, ptyalism and ataxia

Effect of prazosin on felines

Aim of the study

To evaluate the effect of prazosin on the recurrence of urethral obstruction over a 30-day period vs placebo. 

Prospective randomised placebo-controlled blinded trial


Case selection included MN , 1st UO.

Cats had a standardised treatment protocol

Randomly assigned to 2 groups within 8 hours of unblocking : prazosin group (receiving 0.5 mg/cat prazosin q12h for 7 days) or the placebo group (q12hr for 7 days). Clinicians and owners were blinded to the treatment groups. 

Cats were discharged with 7 days of study medication and TM buprenorphine.   Advice was given on litter tray management, water intake, environmental modification and prescription urinary diets were assigned on a case-by-case basis.

Follow-up involved a standardised telephone interview within 1 week of hospital discharge and after 30 days.  Owner compliance with administration of the study medication and occurrence of rUO was recorded.  

Summary of Results

No statistical difference in rUO between groups

  • Incidence of rUO of all cats was 25% which is similar to previous reports 

The only parameters related to ocurrence of rUO were 

  • Increase in creatinine increased in probability of rUO

  • Increase in total solids decreased in probability of rUO 

  • lower packed cell volume (median still within reference interval) increase in probability of rUO

Studies have correlated the degree of azotaemia in cats with UO with the length of hospitalization , the severity of the azotaemia is hypothesized to correlate with a higher level of inflammation and haemorrhage within the bladder and kidneys contributing to more urinary debris , requiring extended hospitalization

The only difference between groups was duration of catheterisation

  • shorter in the prazosin group

    • placebo cats 28 hr; prazosin cats 24 hr 

  • However; duration of catheterization was not found to be associated with any significant difference in development of rUO

  • 10 /16 cats (62%) experienced rUO post u cath removal whilst still in hospital

  • median time was 6hr post U cath removal (range 6-16 hr)

  • Of the 10 cats 2 were placebo cats and 8 were prazosin cats 

Limitations of Study 

The study was underpowered, needing 199 cats to truly determine statistical significance between groups. 15 cats were lost due to non-compliance and proportionally more from the placebo group, which could have affected results. Variables such as duration of catheterisation and management at discharge were not controlled. 

Relevance to clinical practice

Administration of prazosin does not decrease frequency of recurrent urethral obstruction. 

However, larger studies are needed. 

Appropriate analgesia and environmental modification may be equally or more important than therapy with prazosin. 

Higher doses of  prazosin are commonly used in clinical practice and for a longer duration; further studies are needed 

62% of rUO occurred whilst hospitalized (6-16 hours after u cath removal).  This may influence of the timing of u cath removal

Administration of prazosin at study dose rates does not cause a significant decrease in SBP 

Multicentre observational, retrospective cohort study.  2 Part study.

Part 1 

  • Veterinarians who self reported that they either never or always prescribed prazosin to cats with UO were recruited 

  • Exclusions vets who prescribed prazosin intermittently or on the basis of variable individual patient criteria to avoid bias 

  • Cat enrolment and data collection were performed via an electronic survey which included patient data BCS (1-9), treatment data , difficulty unblocking , colour and bloodiness of the urine , and whether the cat developed rUO prior to being discharged from the hospital or within 14 days after discharge

  • Exclusion of cats is they had developed UO secondary to urolithiasis or lower urinary tract neoplasia, if they developed a urethral tear or if the medical record contained insufficient patent data or treatment data for analysis 

Part 2

  • To further evaluate prazosin’s impact on the rate of rUO aggregated the data of this study and 3 most recent published studies while excluding the data from the previous retrospective study 


  • 388 Male cats, all but 11 were MN

  • 354 (91%) were mixed breed cats, 

  • Cats generally received 0.5-1mg of prazosin PO once daily for 14 days 

  • Compared with cats that did not receive prazosin, a greater proportion of cats that received the drug were <2 years of age.

  • No other diff between the 2 groups were identified 

  • Of the 388 cats, 302 (78%) received prazosin while 86 (22%) did not receive prazosin 

  • 302 cats receive prazosin - 34 (11%) developed rUO before discharge and cumulatively by 14 days 72 cats (24%) developed rUO 

  • Of the 86 cats not receiving prazosin 5 (6%) reobstructed before discharge and 11 (13%) reobstructed within 14 days 

  • There was no significant association between prazosin administration and risk of rUO prior to discharge 

  • However the cumulative rate of reobstuction was significantly higher in cats that were prescribed prazosin by 14 days following discharge 

  • Other associations evaluated for increased risk of rUO included:

  • the presence of crystalluria 

  • the subjectively reported difficulty or urethral catheterization

  • a subjectively gritty feel during catheterization and 

  • clarity of the urine at time of u cath removal 

  • The only significantly increased risk identified were a gritty feeling and subjectively diff u cath placement 

  • 126 cats (32%) had gritty feel on urinary catheterization 

  • Of these 8 (6%) experience rUO prior to discharge 

  • 20 (16%) experience rUO within 14 days of discharge

  • resulting in a cumulative rUO rate of 15%

  • There was no significant association between grittiness and rUO prior to discharge 

  • There was no significant difference in rates of rUO between cats that did not and did receive prazosin in the groups of cats with a gritty feel 

  • There was no statistically significant difference between rates of rUO prior to discharge in cats that were subjectively easy or difficult to unblock , but there was a significant difference between rates of rUO for these groups within 14 days of discharge 

  • There was no significant difference in rates of rUO between cats that did not receive prazosin in the groups of cats that were difficult to unblock 

Part 2 

  • 700 cats with UO, 128 (18.3) of which experienced rUO at some time point during their retrospective study with 505 receiving prazosin and 195 not receiving prazosin 

  • The rates of rUO in these populations were 19.4% and 15.4% respectively and there was no statistically significant difference in the rate of rUO between cats that did and did not receive prazosin 

  • However removing the retrospective study by Hetrick and Davidlow and using only the data presented here combined with the prospective data from Hanson et al and Reineke et al revealed that 87 of 365 cats (24%) treated with prazosin developed rUO , while only 17 of the 133 (13%) of cats not prescribed prazosin developed rUO 


  • No reduction in risk of rUO in cats treated with prazosin 

  • Prazosin cats were more likely to reobstuct within 14 days of hospital discharge 

  • Prazosin did not result in reduced risk for rUO 

  • Feline urethra is only composed of smooth muscle along the proximal 28-37% of its length with the remainder of the urethral musculature being striated muscle which not is not relaxed by alpha 1 adrenoceptor blockade 

  • Most of the urethral obstructions are thought to occur in the distal urethra well out of reach of the pharmacological activity and potential smooth muscle relaxant effect of the prazosin in the pre-prostatic and prostatic urethra 

  • Limited evidence that spontaneous urethral spasm occurs in cats 

  • Prazosin increases risk rUO within 14 days of discharge from hospital 

  • Added stress of giving oral meds to cats 

  • Potential hypotension or GIT upset 

  • Owners not administering medication as prescribed 

  • Grittiness at time of U catheterization results in an  increased risk of rUO in 14 days 

  • Increased physical obstruction 

  • Management - flush urethra both during cath  and when the urethral cath is removed but study by Dorsey et al failed to show a decreased rate of rUO associated with flushing 

  • Increased difficultly of urethral cath was associated with increased risk of rUO within 14 days of discharge 

  • Might include increased urethral inflammation and increased urethral trauma to unblock 

  • Seitz et al identified that cats with discoloured urine at the time of catheter removal were more likely to reobstruct - this study did not report a difference in rate of rUO 

  • Limitations to the study 

  • Disparity of cohort size 3.5 x more prazosin cats 

  • Observation study and lack of standardization of treatment 

  • Lack of follow up

Canadian Veterinary Journal

Management options 

In hospital vs outpatient management 

  • Seitz et al 

  • Performed a non-randomized, non-blinded trial for MN cats where the client owner declined conventional treatment.  1-time Urinary catheter placed and no intravenous fluid therapy given.  Sample size 45 in non-treatment group and 46 cats in the conventional treatment group.

  • groups matched by signalment , metabolic compromise , UA and supportive treatments 

  • Risk of rUO within 30 d was significantly higher in outpatient grp 11% vs 31%

  • Supports traditional inpatient therapy over outpatient management with respect to decreasing the risk of rUO within 30d 

  • Limitation observation - owner determined treatment groups, selection bias 

Non-traditional management without passing a urinary catheter

  • Copper et al 

  • Protocol offered to clients declining standard of care treatment

  • Protocol involved a combination of sedative and analgesia, intermittent decompressive cystocentesis, a low stress quiet room and SQ fluids as needed 

  • Exclusion criteria were abnormal clinical findings (i.e. bradycardia, hypothermia or unresponsive), sever metabolic acidosis and hyperkalaemia and radiographic evidence of cystic or urethral calculi 

  • Nonrandomized, non-blinded prospective observational study n=15 cats ,

  • spontaneous urination within 72 hours resulting in hospital discharge was observed in 11 of the 15 cats without the need for u catheter

  • 4 cats developed complications including uroabdomen (3 cats) or hemoabdomen ( 1 cat) 

  • Overall cystocentesis was performed 3 times (range 1 to 10) in each cat but 7 times in those cats that failed in treatment (range 4-11) 

  • Repeated cystocentesis over a short period of time may have predisposed patients to uroabdomen 


Fluid management 

  • Choice of fluid 

  • 2 studies compared alkalinizing balanced electrolyte solutions (BES) ( LRS and Normosol R) to Physiological saline solution (PSS)

  • Cunha et al 2010

  • In a randomized non blinded study of 10 cats with experimentally induced UO the PSS treated group had significantly lower blood pH , bicarbonate and base excess values at multiple time points over the 48 hour post unblocking period compared to LRS treated

  • Drobatz et al 2008 

  • A randomised non blinded prospective clinical trial in 68 naturally occurring urinary obstruction (NAUO) cats compared Normosol-R to PSS 

  • Acid base disturbances resolved more rapidly with the use of Normosol-R compared to PSS at multiple time points over a 12 hour post unblocking period 

  • Fluid type did not influence normalization of serum potassium or the rate at which it occurred in either of these 2 studies 

  • Compared with PSS balanced electrolyte solutions more rapidly resolved metabolic acidosis 

  • Neither exacerbated hyperkalaemia nor affected its resolution 

  • Fluid overload 

  • Ostroski et al J Vet Emerg Crit Care 2017; 27:561-568

  • Nonrandomized , non blinded , retrospective case control NAUO cats 

  • Fluid overload (FO) group and control group were evaluated for risk factors 

  • FO defined as development of respiratory distress from either pulmonary oedema or pleural effusion while receiving IVF during UO treatment 

  • Risk factors for FO include 

  • Administration of fluid bolus at presentation 

  • Development of a heart murmur 

  • Gallop sound during treatment 

  • Development of fluid overload was associated with increased cost (2.9 x) and longer duration of hospitalization (4.1 vs 1.8d) but had no effect on mortality rate 

Decompressive cystocentesis 

  • Benefits include 

  • immediate emptying of the urinary bladder to relieve pain

  • facilitate retrohydropulsion of the obstructed material and passage of urinary catheter by decreasing intraluminal pressure 

  • uncontaminated sample for UA and culture 

  • concerns 

  • potential iatrogenic trauma to further compromise the urinary bladder wall resulting in rupture and uroabdomen 

  • Hall et al J Vet Emerg Crit Care 2015 ; 25:256-262

  • Nonrandomized non blinded retrospective observational study evaluated the effect of routine decompressive cystocentesis evidence of abdominal effusion was present on survey abdominal rads in 56%

  • However, none of the cats were definitively diagnosed with urinary bladder rupture after decompressive cystocentesis 

  • Compared survival to discharge, duration of catheterization and length of hospitalization to previously reported studies and detected no differences 

  • Main limitations lack of control group 

  • DECYST TRIAL Reineke JVECC 2017 

  • Attempting to evaluate the effect of a decompressive cystocentesis before urinary catheterization vs no intervention prior to U cath (UC) 

  • No complications related to decompression cystocentesis, including uro - hemo abdomen were observed 

Anaesthetic considerations 

Coccygeal epidural 

  • O’Hearn VJECC et al 2011 

  • 12 month nonrandomized, non-blinded observational study of NAUO cats with n>15 treated with coccygeal epidurals 

  • Coccygeal epidural provides local analgesia to the perineum, tail, penis, urethra, colon and anus 

  • Potential benefits proposed included minimal additional anaesthetic and analgesic requirements in most cases, during both he unblocking procedure and the post unblocking period , easy to perform 

  • Limitation - lack of objective and placebo group

Unblocking procedure and urinary bladder lavage 

Intraurethral atracurium besylate

  • Galluzzi et al JSAP 2012 

  • Most obstructions distal to prostate of striated muscle

  • Nicotinic acetylcholine receptors on the postsynaptic motor endplate of the neuromuscular junction are completely inhibited by atracurium besylate, resulting in relaxation of the striated urethral musculature 

  • Novel nonrandomized, non-blinded, placebo controlled prospective clinical trial investigated the potential for intraurethral attracurium besylate to facilitate the unblocking procedure in NAUO cats

  • Both atracurium besylate and physiologic saline solution groups were matched for age and weight 

  • Time required for removal of UO was significantly shorter in atracurium besylate group (21.1 +/- 16.2 s) vs physiologic saline solution group (235.2 +/- 132.4s) 

  • Proportion of studied cats in which the urethral plug was removed at first attempt was significantly higher in the atracurium besylate group 64% than in PSS grp 15% 

  • No side effects 

  • Not truly randomized, lack of clinician blinding 

Urinary Bladder lavage 

  • Dorsey et al JAVMA 2019; 254:483-486

  • Randomized, non-blinded placebo controlled prospective clinical study  NAUO cats 

  • After unblocking and u cath placement bladder lavage was performed using PSS until the retrieved fluid was clear with volumes ranging from 50-500ml 

  • Flush and no flush groups were matched by age, bwt, neuter status, previous unblocking history and presence of crystalluria 

  • U bladder lavage has no impact 

  • on in hospital UO recurrence rates (flush 13 % vs 19% no flush)

  • duration of u cath {flush 37hr (range 3-172hr) vs no flush 36 hr (range 1-117hr)}

  •  or duration of hospitalization {flush 3 d (range 0.5 -12d ) vs no flush 3d (1-9d)}

  • Limitations include lack of standardization for other aspects of medical treatment, the decision not to assess azotaemia as an independent risk factor and non-blinded study group, underpowered to detect differences between the 2 groups 

Intravesical Treatments 


  • Healthy uroepithelium is covered with a layer of glycosaminoglycans and glycoproteins 

  • Significantly decreased urine glycosaminoglycan: creatinine ratio have been observed in cats with FIC compared to normal cats , suggesting a defect in the gag layer 

  • Bradley et al JFMS 2014; 16:504-506

  • Did not demonstrate statistically significant differences between treatment n=9 and placebo grp n=7 for pain scores and re-obstruction rates at the 7 day observation period 

  • Delille et al JFMS 2015; 18:492-500

  • NAUO cats n=35 did not document a benefit of intravesical pentosan polysulfate sodium treatment over placebo but limitations in sample size 

Alkalinized lidocaine

  • Zezza et al JVIM 2012; 26:526-531

  • Randomized, non-blinded placebo controlled prospective clinical trial 

  • Effect of intravesical alkalinized lidocaine treatment 

  • Reobstruction rate of treatment group 58% vs control 57% 

  • Amelioration of clinical signs scores 

  • no differences between groups were found for most individual clinical signs with one exception

  • Straining to urinate was associated with an improvement at 2 week in the treatment group compared to control group 

  • Overall follow up data from only 11 cats, including 5 in the treatment group failure of some cats in the control grp to receive intravesical placebo due to temperament, recall bias and low case numbers for which follow up was available for the secondary study endpoint 

Post-obstructive diuresis

  • Fracis et al JFMS 2010; 12:606-860

  • Defined as greater than 2ml/Kg bwt/hr 

  • Non randomized, non-blinded, retrospective study of NAUO cats n= 32 - reported overall post obstructive diuresis rate of 46% which appeared to increase throughout the 64 hour measurement period 

  • But neither fluid rate nor total volume received by this study population was controlled 

  • Frohlich et al JFMS 2016; 18:809-817

  • Nonrandomised, non blinded retrospective study NAUO cats

  • frequency of post obstructive diuresis changed from 87.7% to 36.8% when fluid therapy was taken into consideration 

  • Influence of fluid therapy of post obstructive diuresis was determined by 

  • Correlating fluid rate at time x with urine output at time x +1 

  • Defining post obstructive diuresis in relation to fluid therapy as UO > than the administered amount of IVF on at least 2 subsequent time points 

  • There was a significant correlation between IVFT at time x and urine output at time x+1 at most time points 

  • The authors of the article proposed that adjusting fluid therapy based upon UO may exacerbate post obstructive diuresis and go beyond actual requirements in some patients 

  • Both studies found that patients with acidemia were more likely to have post obstructive diuresis 

  • Francis et al observed that acidemia (pH <7.35) was associated with a 5-fold increase in post obstructive diuresis over the entire study period 

  • Frohlich et al observed that venous pH <7.27 and bicarb levels <15 mmol/L were inversely correlated with UO during the first 4 hour but not beyond that time point 

Management of indwelling urinary catheter

Size of indwelling urinary catheter

  • Hetrick et al JFMS 2011; 13:101-108

  • Nonrandomised, non-blinded retrospective study of NAUO cats

  • Identified a significantly lower rate of rUO at 24 hour post indwelling urinary catheter removal with the use of 3.5 Fr (6.67%) vs 5 Fr (18.97%)

  • Groups were matched by age, rectal temp , bwt, and proportion of cats with azotaemia or hyperkalaemia 

  • An association between catheter size and rUO was identified at 24 hour but not 30 d post indwelling urinary catheter removal 

  • Limitations - multi factors uncontrolled and no standardized treatment protocols 

  • Eisenberg et al JAVMA 2013; 243:1140-1146

  • Nonrandomized, non-blinded, prospective case series of NAUO did not document an association with catheter size 3.5 vs 5 fr and rUO rate 

  • Groups matched by body weight, azotaemia, venous blood gas electrolyte parameters, urine pH, USG , crystalluria, radiographic findings , duration of hospitalization , IVFT and critical illness but NOT age and breed 

  • Mixed breed and older cats were more likely to be associated with rUO median age 8.2yr 

  • Limitations - lack of randomisation, small sample size with a low rate of rUO (15%) and a large number of variables 

Decision to remove indwelling urinary catheter 


  • Pathophysiological basis for recommending a longer duration of catheterization includes time for resolution of post obstructive diuresis, detrusor atony, lower urinary tract inflammation (urethritis and cystitis) and urinary characteristics such as abnormal urine colour , debris, clots and crystals  and may allow time for antispasmodic medications to take effect 

  • Hetrick et al JFMS 2011; 13:101-108

  • No association between rUO and duration of Indwelling Urinary Catheterization (IUC) 

  • Eisenberg et al JAVMA 2013; 243:1140-1146

  • Longer duration of IUC was associated with a lower probability of short term rUO 

  • (24.5 hr vs 26.5 hr) 

  • Seitz et al JAVMA 2018: 252:1509-1520

  • Nonrandomised, non-blinded, prospective cohort found no relationship between duration of IUC and rUO rates 

Abnormal urine colour 

  • Seitz et al JAVMA 2018: 252:1509-1520

  • Identified an association between rUO and abnormal urine colour at the time of catheter removal 

  • Gross urine colour characteristics were subjectively determined in this study with no standardized descriptive scale or pictorial reference, which should be considered in future research 

Catheter associated bacterial complications 

  • Historically the incidence of bacteriuria has been observed to increase after 3 d of both open and closed IUC, supporting a direct relationship between duration of catheterization and incidence of bacteria 

  • Hugonnard et al JFMS 2013; 15:843-848 and Cooper et al JVECC 2019: 1-6

  • 0 cats culture positive at time of presentation 

  • After IUC positive urine cultures occurred within 24 hr in 13% (4/31) of cases in 1 study and 16.7% (3/18) in the other 

  • Second study 48 hour cultures were positive in 33% (6/18) of cases 

  • 2019 ISCAID - Weese JS et al Vet J 2019; 247:8-25

  • Catheterisation asymptomatic bacteriuria is thought to represent a transient colonization of lower urinary tract vs a true catheter associated urinary tract infection 

  • Bacterial colonisation is not predicative of cystitis and is likely to be self-limiting once the urinary catheter is removed 

  • Current recommendations do not support antimicrobial treatment of asymptomatic bacteriuria 

  • The presence of lower urinary tract signs along with fever, bacteraemia of unknown focus, sudden changes in character of the urine (gross appearance and odour), concurrent illness and patient risk factors must all be considered before initiating antimicrobial therapy

  • Cultures of the catheter tip are not recommended

Oral medications 


  • Hetrick et al JAVMA 2013: 243:512-519

  • Nonrandomized, non-blinded retrospective of feline NAUO 

  • Identified significantly lower rates of rUO with prazosin compared to phenoxybenzamine at 24 hr 7.1% vs 21.7% and at 30d 18.2% vs 39.0 % post indwelling urinary catheter removal 

  • Prazosin dose 0.5-1mg/cat PO q12hr 

  • Reineke et al JVECC 2017; 27:387-396

  • Randomized double blinded placebo controlled prospective clinical trial of NAUO cats did not identify differences between prazosin and placebo with groups with respect to rUO rates prior to discharge 7% vs 5% and a 1 month 15% vs 17% and 6 month 37% vs 31% post discharge 

  • 0.25mg/cat by mouth every 12hr for 30d 

  • Prazosin was associated with significantly shorter duration of IUC and hospitalization 

  • Proposed explanations for these contradictory results involve 

  • the prazosin dosage administrated

  • differences between the animals randomized to the prazosin placebo groups 

  • also the potential beneficial treatment effects of prazosin was masked as the groups were not matched by episodes of previous LUTD (prazosin grp had higher rates 44% than placebo grp 10% and consequently, Reineke et al speculate that the cats in the prazosin group were more likely to have episodes of LUTD and therefore increased risk of rUO , rendering detection of a treatment effect more difficult.  


  • Hetrick et al JAVMA 2013:243:512-519

  • Did not report a beneficial effect of meloxicam in the treatment of feline UO 

  • Dorsch et al JFMS 2016 18:925-933

  • Randomized, double blinded placebo controlled prospective clinical trial of NAUO cats 

  • Groups were matched by age, body weight and parameters associated with hematology , biochemistry , venous blood gas electrolyte analysis and urinalysis  

  • Groups were not matched at presentation by episode of previous LUTD , macroscopic haematuria and ionised calcium 

  • Oral meloxicam given daily for 5 days initial 0.1mg/kg and 0.05mg/kg for 4 days

  • Pain assessments were performed daily throughout hospitalization and at a 10-14 day recheck following discharge 

  • During first 5 d post discharge, clients evaluated clinical parameters including demeanour, food intake an painful behaviour using a questionnaire with a visual analogue scale 

  • rUO rates were 22% in meloxicam grp and 26% with placebo

  • limitations small sample size


Address 1-15 Lexington Rd,
Underwood, QLD, AU, 4119

PhonePh: 1300 228 377

Hours Monday-Friday: 8 am-6 pm
Saturday/Sunday - Closed

Veterinary Specialist Services