Dueling Urinary Tract Infections – Or So It Seems

Recently, we had two similar cases present to Ruby Veterinary Urgent Care with urinary symptoms including frequent urination, blood in urine, and painful urination. Both received similar treatment protocols and follow up; however, the outcomes differed. This case report illustrates the importance of diagnostics, follow-up, and how two cases can present so similarly, but have different diagnoses.

An 8.5 year old female spayed mix breed dog presented to Ruby Veterinary Urgent Care for acute onset urinating in the house, followed by dribbling urine. On presentation, vital signs were within normal limits. Physical exam showed discharge in the left ear and associated discomfort and redness, concerning for an ear infection. The remainder of the physical exam was unremarkable, including normal external genitalia (no evidence of a recessed or hooded vulva).

Unfortunately, this dog presented during an ice storm and power outage in Georgia, and our diagnostic equipment was down. Due to this pet’s discomfort, as well as history and symptoms consistent with a possible urinary tract infection, treatment for a presumptive urinary tract infection was discussed and agreed upon. The dog was discharged with a 7-day course of amoxicillin/clavulanate acid (broad-spectrum antibiotic), as well as an nonsteroidal anti-inflammatory for the discomfort (carprofen).

Two weeks later, the same dog represented to Ruby Veterinary Urgent Care for recurrent urinary symptoms. The owner reported completing the 7-day course of antibiotics and the resolution of clinical signs completely. The dog remained symptom-free for 7 days, and then frequent urinations, this time with blood, recurred. Thankfully, the power and all diagnostics were fully functional at this visit! While, this dog may have a recurrent urinary tract infection, the veterinarian discussed with her owner making sure there wasn’t any underlying bladder pathology (stones, mass, blood clot), as well as submitting a urine culture to identify if there is bacteria as well as determine the appropriate antibiotic to treat the bacteria. Her owner agreed and no stones or irregularities were noted in the bladder on x-ray or brief ultrasound while obtaining a sterile urine sample, and the urine was submitted to an outside laboratory for urinalysis and culture. The dog was again discharged on amoxicillin/clavulanate and carprofen since her clinical signs resolved with this course of treatment, while the results of the urine culture were pending.

The urinalysis and culture results returned showing red blood cells, white blood cells and bacteria in her urine. The antibiotic sensitivity showed appropriate response to the amoxicillin/clavulanate she had been prescribed. A total of 14 days was recommended on antibiotic therapy, as well as a recheck culture 3 days prior to discontinuation of antibiotic therapy to confirm resolution. At the time of her recheck culture, all clinical symptoms had resolved. The recheck urine culture came back showing resolution of the white blood cells and bacteria in her urine. Red blood cells were still present. This was suspected to be secondary to the cystocentesis; however, if the urinary symptoms return, this finding of persistent red blood cells in the urine may be clinically relevant. The owner was instructed no further antibiotic therapy was warranted and to continue to monitor for urinary symptoms.

A 7 year old spayed female Samoyed presented to Ruby Veterinary Urgent Care with dribbling urine and frequent urination. Two weeks prior, the dog had been treated with a course of antibiotics (amoxicillin/clavulante) at her primary care due to similar symptoms and a suspected urinary tract infection. Clinical symptoms had resolved with the course of antibiotics and the dog was symptom free for 3-4 days, before symptoms returned.

Physical examination was unremarkable and vital signs were within normal limits. Due to the concern for something more than just a simple UTI, diagnostics were recommended, including a urinalysis and culture and abdominal radiographs. The owner agreed.

Abdominal radiographs were performed and showed no evidence of a bladder stones or bladder irregularity. Urine was obtained via ultrasound-guided cystocentesis, allowing for a quick evaluation of the bladder, which appeared unremarkable. Pending the urinalysis and culture, which can take 3-5 days, the dog was discharged on amoxicillin/clavulanate and carprofen.

The urinalysis and culture results returned showing inappropriately concentrated urine, a high urine pH, white blood cells and red blood cells present; however, no bacteria was noted on analysis and no growth was detected on culture.

Unfortunately, this patient was lost to follow up. Knowing how the patient was doing would help guide additional recommendations. Due to there being no evidence of bacteria in her urine, antibiotic therapy was recommended to be completed and then discontinued. Possible causes of her recurrent urinary symptoms despite no bacterial growth include: sterile cystitis, stones (some stones can’t be seen on x-rays), crystals, tumors or polyps. An ultrasound performed by a board certified radiologist would be the next step if this dog continues to have urinary symptoms. Bloodwork including a chemistry profile and complete blood cell count should also be considered if not yet performed by her primary veterinarian to rule out any metabolic causes including kidney disease, diabetes, and cushing’s. Additional treatments to consider include starting this dog on a urinary diet to address the high level pH.

Lower Urinary Tract Infections in Dogs

Bacterial cystitis is common in female dogs due to:

• Shorter urethra
• Proximity of urethral opening to perineal region
• Ascending bacterial infections Common clinical signs include:
• Pollakiuria
• Stranguria
• Hematuria
• Periuria (house soiling)

Uncomplicated UTI

Defined as:

• Sporadic bacterial cystitis
• Occurring in an otherwise healthy, non-pregnant female dog
• No underlying structural or systemic disease
• No history of recurrent infections

Treatment Recommendations

• 3–7 days of appropriate antimicrobial therapy
• First-line antibiotics selected based on likely pathogens and regional resistance patterns
• Urinalysis recommended; culture may or may not be performed in first-time, uncomplicated cases depending on clinical judgment Short-course therapy is often sufficient when the infection is truly uncomplicated and the organism is susceptible.

Complicated UTI

Defined as:

• Infection associated with underlying abnormalities (e.g., urolithiasis, neoplasia, endocrine disease, anatomic defects)
• Recurrent or relapsing infections
• Infections in male dogs
• Antimicrobial-resistant organisms
• Pyelonephritis

Treatment Recommendations

• Urine culture and sensitivity testing required
• 7–14 days of targeted antimicrobial therapy (longer for upper urinary tract involvement)
• Investigation for underlying causes if recurrent In these cases, recurrence of urinary symptoms following short-course therapy, ended up benefiting from urine cultures to identify one patient with a complicated urinary tract infection and one patient who may or may not have had a true urinary tract infection. The presence high numbers of white blood cells, red blood cells and a urine pH of 9.0 without bacteria suggests a different underlying condition exists.

1. Identifies the Causative Organism

Urinalysis alone may suggest infection (bacteriuria, pyuria), but only culture confirms:

• True infection versus contamination
• Bacterial species present
• Quantitative bacterial growth

2. Guides Appropriate Antibiotic Selection

Empiric antibiotic selection is based on:

• Most common pathogens (e.g., E. coli)
• Regional resistance data
• Drug safety and efficacy However, antimicrobial resistance is increasingly common. Without culture:
• An ineffective antibiotic may temporarily suppress but not eliminate infection
• Clinical signs may improve transiently
• Relapse can occur after discontinuation

3. Prevents Antimicrobial Resistance

Inappropriate antibiotic selection:

• Promotes resistance
• Alters normal flora
• Increases risk of multidrug-resistant infections Culture-directed therapy supports antimicrobial stewardship by:
• Reducing unnecessary antibiotic exposure
• Ensuring effective treatment
• Limiting development of resistant strains

4. Differentiates Relapse vs. Reinfection

Culture results help determine:

• Relapse: Same organism persists (often due to resistance or inadequate duration)
• Reinfection: New organism introduced after successful treatment This distinction influences diagnostic workup and long-term management.

Temporary improvement likely occurred due to:

• Partial bacterial suppression
• Reduction in bacterial load
• Anti-inflammatory effects secondary to bacterial decrease
• The second patient may have had improvement in clinical signs due to the nonsteroidal anti-inflammatory.

1. Urine culture should be strongly considered even in suspected uncomplicated UTIs, especially before prescribing antibiotics.
2. Recurrence after short-course therapy warrants immediate culture and sensitivity testing.
3. Clinical improvement does not guarantee bacterial eradication.
4. Antimicrobial stewardship is essential.

Two female dogs with lower urinary tract signs were initially treated empirically for presumed uncomplicated cystitis. Recurrence of signs following antibiotic discontinuation prompted urine culture, which revealed active infection in one and possible sterile cystitis in the second. Results based on culture and sensitivity played important roles in targeted therapy and antimicrobial stewardship. While performing a urine culture and sensitivity is not always necessary in first time, uncomplicated cases of urinary tract infections and treating empirically with antibiotic therapy is an appropriate course of action, culture and sensitivity should definitely be considered if symptoms don’t resolve with therapy or return after therapy is discontinued.