{"id":20136,"date":"2020-02-19T21:11:10","date_gmt":"2020-02-19T21:11:10","guid":{"rendered":"https:\/\/todaysveterinarypractice.com\/?p=20136"},"modified":"2024-07-02T17:22:54","modified_gmt":"2024-07-02T17:22:54","slug":"urinary-tract-infections-in-dogs","status":"publish","type":"post","link":"https:\/\/navc.sitepreview.app\/todaysveterinarypractice.com\/urology-renal-medicine\/urinary-tract-infections-in-dogs\/","title":{"rendered":"Urinary Tract Infections in Dogs"},"content":{"rendered":"

Urinary tract infections (UTIs) are common in small animals, developing in up to 27% of dogs.1<\/sup> Nearly all infections are caused by pathogenic bacteria, although some are caused by fungi or viruses, albeit rarely. Most bacterial lower UTIs result from bacteria ascending the external genitalia and urethra. Less commonly, bacteria travel through the bloodstream and colonize the urinary tract. <\/span><\/p>\n

Numerous innate defense mechanisms help prevent UTIs. Complete and regular voiding, along with the intrinsic properties of urine (high osmolality, antimicrobial solutes), help create a urinary tract environment that is hostile for microbes. Anatomic barriers and mucosal defenses further prevent adherence of virulent bacteria to the urothelium. <\/span><\/p>\n

However, when these defenses are inadequate, pathogenic bacteria increase the permeability of the urothelium, allowing for passage of inflammatory solutes into the subepithelium as well as secretion of inflammatory cytokines.2<\/sup> The result is inflammation and pain, which are exhibited as dysuria, pollakiuria, stranguria, and\/or hematuria. <\/span><\/p>\n

Elimination of the virulent organism can enable restoration of the normal permeability and integrity of the urothelium. Successful antimicrobial therapy requires an appropriate choice of antibiotic, including dose, frequency, and duration.<\/span><\/p>\n

UTI Diagnosis and Localization<\/h2>\n

The gold standard for UTI diagnosis is urine culture. Ideally, all patients with a suspected UTI should have a urine sample collected via cystocentesis and evaluated by aerobic culture and antibiotic susceptibility testing. The techniques used to determine antibiotic susceptibility are disk diffusion and serial antibiotic dilution. The preferred method is serial antimicrobial dilution, which provides the minimum inhibitory concentration (MIC) of the antibiotic, whereas disk diffusion is considered less reliable and does not provide MICs. <\/span><\/p>\n

Efforts should be made to identify where the UTI is located within the urinary tract.3,4<\/sup> Although locations may overlap, UTIs can occur within the bladder (bacterial cystitis or lower UTI), kidney (pyelonephritis), and\/or prostate (prostatitis). Localization is not always straightforward and is best achieved by evaluating the clinical history, presenting signs, physical examination findings, and laboratory and imaging results. <\/span><\/p>\n

Bacterial Cystitis<\/h3>\n

The most common signs of bacterial cystitis include dysuria, hematuria, pollakiuria, and stranguria. Clients may recognize blood in voided samples. For some dogs with underlying urinary incontinence, the magnitude of leaking may worsen when an infection is present. Urinalysis typically reveals bacteriuria, hematuria, and pyuria.<\/span><\/p>\n

Pyelonephritis<\/h3>\n

Pyelonephritis classically causes fever, lethargy, vomiting, and abdominal pain; however, some patients may experience few or none of these signs and symptoms.5<\/sup> Blood chemistry analysis may reveal new or worsened azotemia, with glucosuria and cylindruria (casts). Urinalysis typically shows evidence of a UTI but could show inactive sediment (few red or white blood cells) in patients with an infected and obstructed kidney (pyonephrosis). Abdominal ultrasonography is not very sensitive or specific for identifying pyelonephritis; however, for some patients, it may reveal enlarged hyperechoic kidneys with perirenal effusion and echogenic debris within the renal pelves. Pyelectasia and proximal ureteral dilation are observed in patients with both pyelonephritis and ureteral obstruction. Dogs with pyelonephritis are more likely than dogs with a sterile nephroureteral obstruction to be febrile, leukopenic, and thrombocytopenic or to have leukocytosis. <\/span><\/p>\n

Prostatitis<\/h3>\n

Prostatitis should be suspected in male dogs, particularly intact dogs, with stranguria.6<\/sup> Prostatitis in castrated male dogs is rare; such dogs often have a history of recent castration. Signs and symptoms of prostatitis vary, depending on the chronicity of the infection. Acute infection is accompanied by more serious, painful clinical signs; chronic infection is often subclinical. Clinical signs relate to pain, which can be exhibited as back or abdominal pain, stiff gait, or depression. Physical examination may reveal an enlarged and asymmetric prostate, painful to palpation. Ultrasonography can show the prostate to be enlarged, heterogeneous, and possibly containing echogenic cysts.<\/span><\/p>\n

Classification of UTIs<\/h2>\n

The 2019 International Society for Companion Animal Infectious Diseases revised the classifications of UTI.7<\/sup> They no longer recommend use of the terms \u201csimple or uncomplicated\u201d and \u201ccomplicated\u201d UTI. The revised classification has 3 diagnoses: subclinical bacteriuria, sporadic cystitis, and recurrent UTI.<\/span><\/p>\n

Subclinical Bacteriuria<\/h3>\n

Although not actually a UTI, the term \u201csubclinical bacteriuria\u201d is used for patients with bacteria identified on urine culture but no lower urinary tract signs. Older literature has often referred to \u201coccult UTIs,\u201d which were most likely subclinical bacteriuria. The term \u201coccult UTI\u201d is outdated and should no longer be used to label bacteriuria in an asymptomatic patient. Most patients with subclinical bacteriuria require no <\/span>treatment and should be considered to have colonization but not necessarily infection of the urinary tract.<\/span><\/p>\n

Sporadic Cystitis<\/h3>\n

Previously known as \u201csimple\u201d or \u201cuncomplicated\u201d UTI, sporadic bacterial infection causes cystitis and lower urinary tract signs. The term \u201ccomplicated\u201d UTI is no longer recommended. Bacterial cystitis may develop in patients with functional or anatomic abnormalities of the urinary tract; the presence of these abnormalities does not necessitate prolonged antibiotic therapy unless pyelonephritis or prostatitis is present. <\/span><\/p>\n

Recurrent UTI<\/h3>\n

A UTI is considered recurrent if the patient experiences 3 or more infections within 12 months. This condition requires investigation to determine whether it is a reinfection or a relapsing or refractory infection. Reinfection<\/b> is the return of a UTI\u2014but caused by a different organism\u2014within 6 months of discontinuation of antibiotic therapy. A relapsing <\/b>UTI is diagnosed when the same organism is cultured again within 6 months of discontinuation of antibiotic therapy. This finding suggests that the patient has a condition that allows for recolonization or prevents total elimination of infection (<\/span>BOX 1<\/b><\/span>); for these patients, additional diagnostics are warranted. A refractory <\/b>UTI is diagnosed when a positive urine culture is obtained while the patient is receiving appropriate antibiotic therapy (based on in vitro susceptibility testing). The possible causes for refractory UTI include the following:<\/span><\/p>\n