The Modern Equine Vet
November 2023
Vol 13 Issue 11 2023
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Technician Update

Case Study: Dribbling Urine in a Warmblood Mare

By Megan Born, MS, LVT, and Nimet Browne, DVM, MPH, DACVIM

An adult Warm-blood mare weighing approximately 600 kg presented for a history of partial urinary incontinence. The mare had been dribbling urine for a few days prior to admission. The mare is used as a riding horse and was open when seen at the hospital. An ultrasound was performed in the field prior to referral, which demonstrated a plethoric bladder and hyperechoic sediment.

She was started on trimethoprim-sulfadiazine (TMP-SMZ) of unknown dosage prior to admission. Laboratory analysis done 24 hours before admission of a complete blood count, fibrinogen, and chemistry had reportedly normal values. A urinalysis done in the facility’s laboratory found hazy urine with trace leukocytes and 3+ calcium carbonate crystals.

The mare was bright, alert and responsive on admission. On physical examination her heart rate was 40 beats per minute (BPM), her respiratory rate was 12 breaths per minute (BrPM), and her temperature was 99.6° F. The capillary refill time was 2 seconds, and her mucous membranes were pink and moist.

Her digital pulses were normal in all 4 limbs with the rear limbs having stronger pulses than the front. The hindlimbs had significant swelling below the tarsus. The semimembranosus area had some skin scalding from the dripping urine.

A neurologic exam was performed, and her mentation was normal, and cranial nerve responses were intact. No ataxia was noted when walking in a straight line and while circling. On clinical examination of this mare, she had normal systemic and neurologic parameters. The urinary tract needed more diagnostics to help determine the cause of the urinary incontinence.

A urinary catheter was placed vaginally into the urethra. Urine was siphoned and was straw colored. Approximately 16 L of urine was retrieved. Toward the end of the fluid retrieval the urine became thick with sediment. A cystoscopy was performed to visually examine the bladder. No cystoliths were observed. A lot of sediment was present in the ventral bladder. The bladder wall had crystals adhering to it, and portions of the bladder urothelium were ulcerated.

The veterinarians made an initial diagnosis of severe hemorrhagic cystitis. It was observed that this cystitis had a sabulous component, which means that the accumulation of sediment was likely due to incomplete emptying of the bladder due to a possible nervous system component to the cystitis. The reason for the bladder atony could be neurologic or idiopathic. The clinician gave a guarded prognosis to the client. The client asked about potentially using this mare as a broodmare, and the veterinarian was unable to give an affirmative until the cystitis resolved.

The mare was tested for equine protozoal myeloencephalitis (EPM) prior to arrival to assess whether EPM was the cause of the bladder nerve function component. The results were not available on admission. Other causes of urinary incontinence include equine herpesvirus 1, sacral/coccygeal trauma, congenital causes, neoplasia, idiopathic bladder paralysis, equine motor neuron disease and polyneuritis equi, according to Mair, et al.

This mare did not exhibit a fever or other systemic indicators of herpesvirus. No evidence on clinical examination or prior history of predisposition to any of these other causes of bladder atony was found. Ectopic ureters can also be the cause of urinary incontinence, but the cystoscopy showed normal functioning ureters. Mares after foaling can have some nerve damage that could cause bladder atony, but the mare was a maiden.

The geographical location of the region the mare lives has a high prevalence of EPM infection making that disease the most likely cause of the sabulous cystitis if not of idiopathic etiology.

An EPM serum titer of Sarcocystitis neurona (causative agent of EPM) types 2, 3 and 5 was performed, and the titer level was 1:500. This titer level only confirms exposure. A cerebrospinal fluid (CSF) tap would have been the gold standard for the definitive rule out of this disease as the cause of the sabulous cystitis. A CSF tap also cannot completely determine pathogenicity of EPM in the individual horse as a positive serum CSF tap is not always indicative of the organism causing systemic disruptions. A CSF tap that is negative for the organism, however, is always an indication that S. neurona is not implicated in the clinical signs. The owners of this mare were financially constrained, so a CSF tap was not feasible for them at this time.

Sabulous cystitis can be a secondary sequela to the presence of bacteria, as well as can be predisposed to bacterial proliferation due to the static urine retention. A urine culture was done after admittance to determine presence and classification of bacteria. Two isolates were found, the first was a light alpha Streptococcus species and the other was a scant Pseudomonas aeruginosa. A sensitivity was done as well to determine if the TMP-SMZ regimen the mare presented with was adequate for continued therapy. The sensitivity showed that Streptococcus had intermediate sensitivity, but the Pseudomonas was resistant to TMP-SMZ. The owners had some financial constraints that prevented a change in antibiotic therapy. However, fortunately Pseudomonas can be a contaminant, and TMP-SMZ tends to accumulate in the urinary tract potentially making both bacteria susceptible to higher doses.

The mare was managed during the hospitalization period with the following treatments and procedures:
Complete physical examination with vital parameters every 6 hours;
Assessment of urine output (non-quantifiable) every 2 hours;
Assessment of manure output every 4 hours;
Monitoring functionality and placement of urinary catheter every 2 hours;
Flush urinary catheter every 4 hours to prevent blockage;
Analgesics (detailed in next section); and
Repeat cystoscopies to assess progress and response to therapy.

On the day of admission, the mare became uncomfortable later in the evening, showing signs of colic. It was not determined whether she was having bladder pain or generalized abdominal pain. A nasogastric tube was passed and electrolytes given orally. She was also muzzled overnight in case the pain signs were due to a gastrointestinal problem. She had low manure production until the morning. Flunixin meglumine was given every 12 hours. The mare was also walked to help with GI motility.

Fluids were given the first day due to possible GI issues at a rate of 10 L every 12 hours. The bladder was lavaged with 1 L of saline and 50 mLs of 99% DMSO every 12 hours. The mare’s heart rate was in the 40s (bpm) on the first day of admission. Flushes were added to the chart every 4 hours after sediment was found to be building up in the urinary catheter.

On the day after admission no fluids were given. The mare was given free choice hay and made comfortable. Her heart rate had dropped to the low 30s (bpm). A repeat cystoscopy was performed, and the inflammation and sediment build up weres improving.

On the third day after admission bethanecol was started to assist with the emptying of the bladder. TMP-SMZ were started every 12 hours to deter bacterial growth. The IV catheter was removed, and the mare was changed to receiving the same dose of flunixin meglumine the injectable given orally to reduce owner cost. Mare remained comfortable with normal appetite, manure and vital signs.

On the fourth day after admission the bladder lavages were changed to 500 mLs of tricide flush (Bottle contained 8mM USP Disodium, 0.01 mM Disodium/kg).

On day 5, the mare continued to improve with stable parameters and behavior. Flunixin meglumine was reduced to every 24 hours. Another cystoscopy was performed and showed a reduction in inflammation by 75%.

On day 6, the urinary catheter was removed, and the mare was monitored for urination. Bladder ultrasounds were also performed to assess normal micturition.

The mare was discharged to the farm on the seventh day after admission.

On discharge from the hospital the mare had improved considerably. The most recent endoscopes showed less sediment and decreased inflammation by 75%. The mare was able to posture and urinate on her own without assistance from a urinary catheter. The mare had also stopped dribbling urine.

The veterinarian reiterated to the client that although there were marked improvements, the cystitis is still ongoing. Therefore, systemic treatment was still needed once discharged to the farm to give the mare the best possible outcome. The veterinarian also reminded the clients of the fact that a cerebrospinal fluid tap is the only way to definitely rule out EPM as the cause of the sabulous cystitis.

The goals of therapy in this case were to assist with micturition until whatever inflammatory or nervous process resolved enough for the mare to be able to fully void her bladder. The cystoscopies were helpful as an objective assessment of improvement. The mare did better than expected with therapy especially due to the financial concerns of the owners. MeV

For more information:
Dubey JP. et al. A review of Sarcocystis neurona and equine protozoal myeloencephalitis (EPM). Vet Parasitol. 2001;95(2-4):89-131.

Hay AN, et al. 2021, December. Horses affected by EPM have increased sCD14 compared to healthy horses. Vet Immunol Immunopathol. 2021;242:110338.

Mair T. 2022, April. Urinary Incontinence and Urinary Tract Infections. Vet Clin North Am: Equine Pract. 2022;38(1):73-97

Schott HC, Waldridge B, Bayley WM. 2018. Equine Internal Medicine. Fourth Edition. Page 957. Elsevier press.

Sponseller BT. 2015. Robinson’s Current Therapy in Equine Medicine. Seventh Edition. Page 443. Elsevier press.

Megan Born, MS., LVT is a licensed veterinary technician who has worked in the Internal Medicine and Critical Care Unit at Hagyard Equine Medical Institute since 2012. She is also a part time instructor for veterinary technicians at the University of Missouri Online. She enjoys showing reining horses and attends Clays Mill Baptist Church.

Dr. Nimet Browne studied veterinary medicine at University of Tennessee, graduating in 2010. Following veterinary school, Nimet went on to complete an internship in a private practice in Illinois, then a large animal internal medicine residency at Virginia Tech. During that time, she also obtained a Masters In Public Health with a focus on infectious disease. Following her residency, she completed a yearlong fellowship at Hagyard Equine Medical Institute. In 2016, she took a faculty position in the equine internal medicine department at North Carolina State University. Her interests include neonatal medicine, gastrointestinal disease, infectious disease and public health. She is currently working on manuscripts regarding infectious causes of diarrhea in neonates as well as the use on enrofloxacin in neonates

Ulcerated and hemorrhagic bladder urothelium
Images courtesy of Megan Born

Ulcerated and hemorrhagic bladder urothelium

Large amount of sediment on bladder floor

Cystoscope 3 Weeks after Initial Admission Showing Improvement in Hemorrhagic Cystitis and Sediment Accumulation