Serial Urinalysis in Monitoring Urinary Tract Infections

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-11

Key Takeaways

• Serial urinalysis and urine culture are critical for confirming bacterial urinary tract infection (UTI) resolution and detecting recurrence in dogs and cats, with recheck urinalysis assessing pyuria and bacteriuria 5-7 days post-therapy and urine culture confirming bacteriologic cure 7-14 days post-therapy.
• Quantitative urine culture thresholds are essential for distinguishing true infection from contamination, with any growth from cystocentesis considered significant, while voided samples require ≥10^5 CFU/mL for significance.
• Persistent pyuria or hematuria at recheck warrants immediate urine culture, as active sediment indicates ongoing inflammation that may reflect bacterial persistence or non-bacterial causes like urolithiasis or neoplasia.
• Distinguishing relapse (same organism within 2 weeks) from reinfection (different organism or later recurrence) guides management, with relapse suggesting incomplete eradication and reinfection prompting investigation of underlying predisposing factors.
• Susceptibility testing is mandatory for any growth at recheck after therapy to guide antimicrobial selection for persistent infection, as emerging resistance patterns to common agents like amoxicillin-clavulanic acid are documented.
• Underlying disease screening is recommended after a second documented UTI to identify predisposing factors such as endocrinopathies or anatomical abnormalities, which are crucial for preventing future recurrences.

Serial urinalysis and urine culture are the principal laboratory tools for confirming resolution of bacterial urinary tract infection (UTI) and for detecting recurrence in dogs and cats. This article addresses the practicing veterinarian's procedural questions: when to recheck urine, how to interpret the sediment and culture results at each time point, and how to distinguish persistent infection, relapse, reinfection, and contamination. The focus is on monitoring after a diagnosis has been established, not on initial diagnostic workup.

The clinical decisions covered here include selection of the recheck interval, interpretation of pyuria and bacteriuria in the face of prior antimicrobial therapy, the role of quantitative culture thresholds, and the management of recurrent or refractory cases. The reader is assumed to be comfortable with cystocentesis technique, standard urinalysis methodology, and basic antimicrobial susceptibility testing concepts. Where the evidence base is limited or contested, this is stated explicitly.

At a Glance

Rationale for Serial Monitoring

Bacterial UTI in dogs and cats is commonly diagnosed and frequently treated empirically. Surveillance data from a UK tertiary referral hospital showed positive cultures in 17.5% of 5923 canine urine samples submitted over a 10-year period, with Escherichia coli the most common isolate at 53.9% (Prevalence and antimicrobial resistance of canine urinary tract pathogens). A separate UK laboratory study of 808 urocultures found significant bacteriuria in 18.4% of canine and 10.0% of feline samples, again with E. coli predominating (Results of urinary bacterial cultures and antibiotic susceptibility testing of dogs and cats in the UK). These prevalence figures explain why empirical therapy is common, but they also underscore the need for verification of cure.

Clinical resolution of signs does not reliably predict bacteriologic cure. A patient may become asymptomatic while low-grade infection persists, particularly when inflammation is suppressed but bacterial colonization continues. Serial urinalysis provides an objective measure of urinary tract inflammation, and urine culture provides the definitive test for bacterial presence. Used together, they detect treatment failure earlier than clinical observation alone and allow timely adjustment of therapy before complications such as ascending infection or urolithiasis develop.

Pathophysiology of Treatment Response

The urinary bladder mucosa responds to bacterial invasion with neutrophil recruitment, which produces the pyuria detected on sediment examination. Successful antimicrobial therapy eliminates the bacterial population, and the inflammatory response then resolves over several days. The rate of resolution depends on the severity of the initial infection, the presence of uroliths or mucosal damage, and the susceptibility of the organizm to the chosen drug.

Persistent pyuria at the recheck examination indicates ongoing inflammation. This may reflect bacterial persistence, but it can also result from sterile inflammation caused by urolithiasis, neoplasia, or recent catheterization. Conversely, absence of pyuria does not exclude infection. Some patients, particularly those with immunosuppression or glucocorticoid therapy, mount a blunted inflammatory response. The sediment findings must therefore be interpreted alongside culture results, not in isolation.

Antimicrobial resistance patterns influence the likelihood of treatment success. European surveillance data from the ComPath program, using Clinical and Laboratory Standards Institute methodology, showed that E. coli susceptibility to fluoroquinolones and trimethoprim-sulfamethoxazole exceeded 90% in dogs and cats, while ampicillin susceptibility was approximately 80% (Antimicrobial Susceptibility Monitoring of Bacterial Pathogens Isolated from Urinary Tract Infections in Dogs and Cats Across Europe). An Italian study of empirically treated animals found that prior antimicrobial exposure affected susceptibility patterns, with amoxicillin-clavulanic acid and doxycycline most effective against Gram-positive isolates and marbofloxacin a useful option against Gram-negative infections (Antimicrobial susceptibility survey on bacterial agents of canine and feline urinary tract infections). These population-level data inform empirical choices, but individual susceptibility testing remains necessary when monitoring reveals persistent infection.

Urinalysis Parameters in Monitoring

Pyuria and the Active Sediment

The presence of neutrophils in urine sediment is the most sensitive cytologic indicator of urinary tract inflammation. At the recheck examination, the clinician should quantify white blood cells per high-power field and compare this with the pretreatment finding. A trend toward decreasing pyuria suggests appropriate response, while stable or increasing pyuria indicates ongoing inflammation that requires culture.

Red blood cells and transitional epithelial cells frequently accompany pyuria in bacterial cystitis. Their persistence after therapy raises the possibility of urolithiasis, neoplasia, or chronic mucosal injury. The sediment should be examined fresh, ideally within 30 to 60 minutes of collection, because neutrophils lyse rapidly in dilute or alkaline urine.

Bacteriuria on Sediment Examination

Bacteria visible on sediment examination correlate with significant bacteriuria when the sample is collected by cystocentesis. However, the sensitivity of sediment examination is imperfect. Low numbers of organizms may be missed, and cocci can be difficult to distinguish from debris. A negative sediment examination therefore does not rule out infection, and a positive examination should always be confirmed by culture before antimicrobial decisions are finalized.

Urine Specific Gravity and pH

Concentrated urine inhibits bacterial growth, while dilute urine permits more rapid multiplication. A persistently low specific gravity at recheck may indicate an underlying cause of the UTI, such as renal disease, hyperadrenocorticism, or psychogenic polydipsia. Urine pH affects both bacterial survival and the efficacy of some antimicrobials. These parameters are not direct indicators of infection resolution, but they inform interpretation of the culture result and guide investigation of predisposing factors.

Culture-Based Monitoring

Timing of the Recheck Culture

The optimal time for the recheck urine culture is 7 to 14 days after completion of the antimicrobial course. This interval allows residual antimicrobial activity to clear from the urine and permits any surviving organizms to multiply to detectable numbers. A culture performed during therapy may yield false negatives because antimicrobial concentrations in urine remain high, and a culture performed too early after cessation may miss slow-growing organizms.

Quantitative Interpretation

Cystocentesis is the preferred collection method for monitoring cultures because it avoids distal urethral and genital contamination. Any bacterial growth from a cystocentesis sample is considered significant, regardless of colony count. For voided samples, the traditional threshold of 10^5 CFU/mL distinguishes true infection from contamination, though lower counts may be significant in animals with clinical signs and consistent sediment findings. The laboratory report should always be interpreted in light of the collection method.

Susceptibility Testing

When the recheck culture yields growth, susceptibility testing is mandatory. The organizm may differ from the original isolate, or the original isolate may have developed resistance during therapy. Population-level resistance data from the UK showed emerging resistance to amoxicillin-clavulanic acid in E. coli, with almost 20% of isolates resistant (Results of urinary bacterial cultures and antibiotic susceptibility testing of dogs and cats in the UK). Empirical retreatment without susceptibility data risks further therapeutic failure and contributes to antimicrobial resistance selection.

Distinguishing Relapse from Reinfection

The timing of recurrence after a documented cure informs the diagnostic approach. Growth of the same organizm within 2 weeks of completing therapy suggests relapse, indicating that the original infection was not eradicated. This may result from antimicrobial resistance, poor owner compliance, or a nidus of infection such as a urolith or devitalized tissue. Growth of a different organizm, or growth of the same organizm after a longer interval, suggests reinfection and should prompt investigation of underlying predisposing factors.

Recurrent UTI, defined as two or more infections within 6 to 12 months, warrants a systematic search for structural and functional abnormalities. This includes diagnostic imaging, biochemical screening for endocrinopathy, and assessment of voiding function. The serial monitoring protocol described here provides the documentation needed to establish the recurrence pattern and guide this investigation.

Structured Recheck Protocols

A structured recheck protocol reduces the variability that undermines serial interpretation. The protocol should specify collection method, timing relative to antimicrobial cessation, and the laboratory tests performed at each interval. For uncomplicated bacterial cystitis in dogs, a urine culture 5 to 7 days after completing antimicrobial therapy is the conventional standard. Cats with bacterial urinary tract infection, which is far less common than in dogs, warrant the same culture-based recheck because clinical signs alone correlate poorly with bacteriologic cure.

The protocol differs for complicated infections. Patients with urolithiasis, chronic kidney disease, diabetes mellitus, or anatomic abnormalities require a culture during therapy, typically 3 to 5 days after treatment initiation, to document early response. A second culture 5 to 7 days after therapy completion confirms resolution. Patients with indwelling urinary catheters or those managed with intermittent catheterization require a different schedule, with culture at catheter removal and again 7 days later, because catheter-associated infection may not declare itself until the device is gone.

Serial urinalysis alone cannot replace the recheck culture. The negative predictive value of an inactive sediment is imperfect, and subclinical bacteriuria can persist with a normal sediment examination. The culture remains the definitive monitoring tool. Urinalysis adds value by detecting recurrence between scheduled cultures and by identifying patients in whom culture is indicated sooner than planned.

The Post-Treatment Recheck Visit

The first scheduled recheck occurs 5 to 7 days after the final dose of antimicrobial. Urine should be collected by cystocentesis whenever possible. Free-catch samples in female dogs are particularly prone to contamination, and a positive culture from a free-catch sample forces a difficult distinction between true infection and sampling artefact. Cystocentesis eliminates that ambiguity.

At this visit, perform both urinalysis and quantitative culture. The urinalysis provides immediate information while the culture is pending. Pyuria with a negative culture suggests either recent antimicrobial effect with persistent inflammation or a non-bacterial cause of inflammation such as urolithiasis or neoplasia. Bacteriuria with a negative culture raises the possibility of non-viable organizms, recent antimicrobial exposure, or contamination. A positive culture with an inactive sediment indicates subclinical bacteriuria or early recurrence.

Interpretation of the post-treatment culture requires knowledge of the original isolate. If the same species and susceptibility profile returns, relapse is likely. If a different species appears, reinfection or a mixed infection that was initially missed is more probable. The distinction matters for management. Relapse suggests inadequate tissue penetration, a sequestered nidus, or a resistant subpopulation. Reinfection suggests an ongoing predisposing factor that requires identification.

Monitoring Parameters and Their Limitations

Serial monitoring should track a defined set of parameters, each with a specific interpretive value.

The sediment examination should be standardized. Centrifuge a fixed volume, typically 5 to 10 mL, at a consistent speed and duration, and resuspend in a consistent volume of supernatant. Examine the sediment systematically, reporting cells per high-power field instead of descriptive terms such as "moderate" or "many." This allows quantitative comparison across visits. The American Society for Veterinary Clinical Pathology quality assurance guidelines provide a framework for standardizing laboratory methods and reporting.

Decision Points and Protocol Modification

The monitoring protocol must adapt to the patient's response. A dog with negative culture and inactive sediment at the 7-day recheck requires no further monitoring unless clinical signs recur. A dog with negative culture but persistent pyuria warrants a repeat urinalysis in 2 to 4 weeks to document resolution of inflammation. Persistent pyuria beyond 4 weeks with negative cultures should prompt investigation for urolithiasis, neoplasia, or idiopathic sterile cystitis.

A positive culture at the 7-day recheck requires susceptibility testing on the new isolate. Empirical re-treatment without culture is discouraged, particularly given the resistance patterns documented in canine uropathogens. European surveillance data from the ComPath program show that while fluoroquinolone and trimethoprim-sulfamethoxazole susceptibility in Escherichia coli remains above 90 percent, ampicillin susceptibility is only approximately 80 percent, and resistance to amoxicillin-clavulanic acid is emerging. UK laboratory data similarly demonstrate that approximately one third of E. coli isolates are resistant to ampicillin and almost 20 percent resistant to amoxicillin-clavulanic acid. Empirical choices based on outdated assumptions risk failure.

When relapse is confirmed, the approach changes. Imaging of the urinary tract is indicated to identify uroliths, polyps, or anatomic abnormalities. Urine culture should be repeated after a short antimicrobial-free interval if the patient's condition permits, to allow any suppressed organizms to grow. Consider culture of the prostate in intact male dogs with recurrent infection, as prostatic tissue penetration of many antimicrobials is poor.

Long-Term Surveillance

Patients with recurrent or complicated infections require ongoing surveillance beyond the immediate post-treatment period. A reasonable schedule is urinalysis and culture at 1, 3, 6, and 12 months after documented cure, then annually if the patient remains infection-free. Patients with predisposing conditions such as hyperadrenocorticism, diabetes mellitus, or chronic kidney disease may need more frequent monitoring because recurrence risk is higher.

Owner observation alone is insufficient for surveillance. Many dogs with recurrent urinary tract infection show no clinical signs between episodes, and the first indication of recurrence may be a positive culture on routine monitoring. This is particularly true in patients with chronic kidney disease, where polyuria dilutes the urine and reduces the sensitivity of both sediment examination and point-of-care testing.

The monitoring interval should be shortened if the patient experiences an intercurrent illness, receives immunosuppressive therapy, or undergoes urinary catheterization. Each of these events increases infection risk and warrants a urinalysis and culture 7 to 14 days after the event.

Documentation is essential. Record the collection method, the time since the last antimicrobial dose, the sediment findings quantitatively, and the culture result with colony count and susceptibility profile. This record allows pattern recognition over time. A patient who repeatedly relapses with the same multidrug-resistant isolate requires a different investigation than one who acquires a new susceptible infection every few months. The distinction between relapse and reinfection, established by comparing serial isolates, guides whether the problem is one of treatment failure or of host susceptibility.

Recognized Complications and Failure Modes

The most consequential failure in monitoring treated urinary tract infections is the persistence of infection despite apparent clinical improvement. Owners frequently report resolution of pollakiuria and stranguria within 48 hours of starting antimicrobial therapy, but clinical improvement does not equate to microbiological cure. The post-treatment recheck culture remains the only reliable arbiter, and skipping it because the patient appears well is the most common monitoring failure in practice.

Subclinical bacteriuria presents a distinct diagnostic trap. A positive culture in a patient without active sediment or clinical signs may represent persistent infection, early relapse, or contamination, and the distinction changes management. The urine specific gravity and sediment findings must be interpreted together with the quantitative culture result. A high colony count with pyuria supports active infection. A high count without pyuria in a patient with dilute urine may indicate a compromised host response, while a low count with pyuria raises the possibility of sample contamination or recent antimicrobial exposure.

Antimicrobial resistance emerging during therapy is a recognized complication, particularly with beta-lactams and fluoroquinolones. European surveillance data show that Escherichia coli isolates from dogs and cats have reduced susceptibility to ampicillin and emerging resistance to amoxicillin-clavulanic acid, with approximately one fifth of E. coli isolates resistant to this combination Fonseca et al. 2021. A patient that fails to clear bacteriuria on the recheck culture despite an apparently appropriate agent should prompt repeat susceptibility testing instead of extension of the same drug. Prior antimicrobial exposure selects for resistant organizms, and the susceptibility profile of the relapse isolate may differ from the original Rampacci et al. 2018.

Common Errors and Corrective Actions

Less experienced clinicians often misinterpret persistent pyuria as treatment failure. Pyuria can persist for days after bacterial clearance because neutrophils and cellular debris are cleared slowly from the urinary tract. The recheck culture, not the sediment, defines cure. Conversely, the absence of pyuria does not exclude infection, particularly in immunocompromised patients or those with dilute urine.

A second recurring error is the use of dipstick leukocyte esterase as a surrogate for sediment examination. The dipstick is insensitive in veterinary urine, especially in the presence of high specific gravity, and cannot replace microscopic evaluation. The ASVCP quality assurance guidelines emphasize that sediment examination must follow standardized protocols with defined centrifugation and staining methods for results to be comparable across serial samples ASVCP guidelines.

Sampling technique errors undermine the entire monitoring sequence. Perineal or voided samples in female dogs yield false positive cultures at an unacceptable rate, and a positive culture from an improperly collected sample triggers unnecessary antimicrobial courses. Cystocentesis is the only acceptable collection method for monitoring bacteriuria. The laboratory should be told the collection method so the quantitative threshold can be interpreted correctly.

A third error is treating the susceptibility panel as a static result. Susceptibility testing reflects the isolate at the time of sampling, and the panel does not predict the response of a different organizm that emerges during therapy. Mixed cultures are more common than often assumed, and a single isolate on the initial culture does not guarantee that a subsequent positive culture will be the same species Hall et al. 2013.

Limitations of the Evidence and Areas of Disagreement

The evidence base for serial urinalysis monitoring in veterinary patients rests largely on retrospective culture surveys and expert opinion. Prospective studies defining the optimal timing of recheck cultures, the predictive value of pyuria resolution, and the cost effectiveness of routine post-treatment culture are lacking. The pan-European ComPath surveillance program provides useful susceptibility data but enrolled only animals not recently exposed to antimicrobials, which limits its direct applicability to the patient failing therapy Moyaert et al. 2017.

Expert opinion diverges on the necessity of routine recheck culture in uncomplicated lower urinary tract infections in dogs. Some clinicians argue that a healthy dog with complete clinical resolution and a normal active sediment does not require culture confirmation. Others recommend culture in all patients because of the rising prevalence of resistant uropathogens and the difficulty of predicting resistance from clinical presentation. The weight of current opinion favours culture confirmation in recurrent, complicated, or hospital-associated infections, with clinical judgment reserved for first-episode uncomplicated cases.

There is also disagreement about the management of subclinical bacteriuria detected on a surveillance culture. Some authorities recommend treatment only when pyuria or clinical signs are present, while others treat any significant bacteriuria to prevent ascending infection. The evidence does not clearly favour either position, and the decision should incorporate the patient's comorbidities, urine concentrating ability, and history of prior infections.

Referral, Consultation, and Reporting

Referral to a specialist is warranted when a patient fails to clear bacteriuria after two appropriately selected antimicrobial courses, when the relapse isolate shows resistance to all oral options, or when upper urinary tract involvement is suspected. A veterinary internal medicine specialist can guide imaging of the urinary tract, urodynamic assessment, and management of underlying predisposing conditions such as urolithiasis, neoplasia, or anatomic abnormalities. The MSD Veterinary Manual provides a structured approach to complicated and recurrent urinary tract infections for practitioners seeking a reference framework MSD Veterinary Manual.

Laboratory consultation is appropriate when culture results conflict with clinical findings, when the laboratory reports unusual organizms or mixed growth patterns, or when susceptibility testing yields results that do not match the expected profile for the species. The laboratory can clarify whether the isolate is a likely contaminant, a pathogen of emerging significance, or a technical artefact.

Regulatory reporting obligations vary by jurisdiction. Multidrug-resistant organizms, particularly those resistant to carbapenems or extended-spectrum cephalosporins, may be notifiable in some regions, and veterinary clinicians should be aware of local requirements. The World Organization for Animal Health terrestrial standards address antimicrobial resistance surveillance and stewardship expectations for veterinary services WOAH terrestrial animal health standards. When a resistant organizm is identified, the clinician should also consider whether household transmission to humans is plausible and counsel appropriate hygiene measures.

Troubleshooting Guide

Frequently Asked Questions

How Should I Adjust Monitoring When Cystocentesis Is Not Feasible?

When cystocentesis is refused or contraindicated, free-catch urine remains acceptable for sediment evaluation but not for culture. Contamination from the distal urethra and genital tract can produce false-positive cultures, particularly in female dogs. If culture is essential and cystocentesis is impossible, collect a midstream free-catch sample, interpret quantitative growth with caution, and require higher colony counts, typically greater than 10,000 CFU/mL, before considering the isolate clinically significant. Serial pyuria trends from free-catch samples remain useful for monitoring response, but a negative culture from a contaminated sample carries less certainty. Document the collection method in the record so subsequent comparisons account for this limitation.

What Is the Minimum Monitoring Protocol When Cost Is a Limitation?

A single recheck urinalysis with active sediment examination performed 5 to 7 days after completing antimicrobial therapy provides the minimum acceptable monitoring. If pyuria has resolved and bacteriuria is absent, clinical recovery is likely, though recurrence remains possible. When the owner declines the recheck urinalysis, request that they monitor for pollakiuria, stranguria, or malodorous urine and return promptly if these signs appear. For recurrent infections, culture becomes non-negotiable because susceptibility data guide the next antimicrobial choice. The cost of an untreated resistant infection, including repeated visits and potential complications such as urolithiasis or pyelonephritis, usually exceeds the cost of the recheck visit.

How Does Monitoring Differ in Cats with Chronic Kidney Disease?

Cats with chronic kidney disease produce dilute urine, and the absence of concentrated urine does not exclude infection. The active sediment becomes more important because bacteriuria and pyuria may be the only abnormalities present. Repeat culture is strongly advised in these patients because clinical signs are often subtle and antimicrobial penetration into diseased kidneys is variable. The ASVCP quality assurance guidelines emphasize that sediment examination should be standardized, which matters when dilute samples make cellular elements harder to detect. Consider that proteinuria in these cats may reflect glomerular disease instead of inflammation, so do not use protein alone as a monitoring parameter.

What Should I Record in the Medical Record for Serial Monitoring?

Record the collection method, time since last antimicrobial dose, urine specific gravity, pH, semiquantitative protein, and a standardized sediment description including the number of white blood cells per high-power field. Note the presence or absence of bacteriuria and bacterial morphology. For cultures, record the quantitative colony count, isolate identification, and susceptibility results. Include the clinical signs at each visit and the owner's report of adherence to the antimicrobial protocol. This structure allows direct comparison across visits and supports the distinction between relapse and reinfection when the isolate is typed. The AVMA practice resources recommend clear documentation of antimicrobial use decisions, which supports stewardship audits and future clinical decisions.

How Do I Explain the Need for a Recheck Culture to a Reluctant Owner?

Frame the recheck culture as a test of cure instead of a lack of trust in the treatment. Explain that clinical improvement can occur even when bacteria persist, and that a silent residual infection increases the risk of recurrence and resistance. Emphasize that the culture result determines whether the current antimicrobial was effective or whether a different drug is needed. Owners often respond well to the message that skipping the recheck may lead to a more expensive and prolonged second course of treatment. The ComPath surveillance data show that resistance to commonly used antimicrobials is present in uropathogens, which supports the argument that confirmation of cure is not optional in recurrent cases.

When Should I Refer a Case for Specialist Evaluation?

Refer when a patient has three or more culture-confirmed recurrences within 12 months despite appropriate antimicrobial selection, when imaging suggests urolithiasis, pyelonephritis, or anatomical abnormality, or when a multidrug-resistant organizm is isolated and no oral option remains. Referral is also appropriate when the infection fails to clear despite two courses of culture-guided therapy. Specialists can perform cystoscopy, advanced imaging, and urodynamic studies that are not available in general practice. The MSD Veterinary Manual notes that underlying structural disease is a common reason for treatment failure, and identifying such disease often requires specialised equipment. Send the complete monitoring record, including all urinalyses, cultures, and imaging, to avoid repeating diagnostics.

Related Clinical & Scientific Guides

• Peripheral Blood Smear Evaluation: A Step-by-Step Guide
• Reticulocyte Counts in Veterinary Medicine: Clinical Utility and Interpretation
• Cerebrospinal Fluid Analysis in Veterinary Neurology: Collection and Interpretation

References and Further Reading

• Prevalence and antimicrobial resistance of canine urinary tract pathogens.. 2013.
• Results of urinary bacterial cultures and antibiotic susceptibility testing of dogs and cats in the UK.. 2021.
• Antimicrobial susceptibility survey on bacterial agents of canine and feline urinary tract infections: Weight of the empirical treatment.. 2018.
• Mouse orthotopic models for bladder cancer research.. 2009.
• Norwegian patients and retail chicken meat share cephalosporin-resistant Escherichia coli and IncK/bla_CMY-2 resistance plasmids.. 2017.
• Antimicrobial Susceptibility Monitoring of Bacterial Pathogens Isolated from Urinary Tract Infections in Dogs and Cats Across Europe: ComPath Results.. 2017.
• American Society for Veterinary Clinical Pathology Guidelines. American Society for Veterinary Clinical Pathology.
• MSD Veterinary Manual, Professional Edition. MSD Veterinary Manual.
• American Veterinary Medical Association Practice Resources. American Veterinary Medical Association.

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This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.