Page 881 - Small Animal Clinical Nutrition 5th Edition

912 Small Animal Clinical Nutrition

CASE 43-3
VetBooks.ir Recurrent Urinary Tract Infection in a Rottweiler

Carl A. Osborne, DVM, PhD, Dipl. ACVIM (Internal Medicine)
College of Veterinary Medicine
University of Minnesota
St. Paul, Minnesota, USA

Patient Assessment
A five-year-old, 41-kg, neutered male rottweiler was examined for recurrent dysuria and pollakiuria of six months’ duration, pre-
sumed to be caused by bacterial urinary tract infection. These clinical signs had been treated intermittently with a variety of orally
administered antibiotics given for intervals ranging from 10 to 21 days.Treatment was associated with remission of dysuria and pol-
lakiuria, but these signs recurred a short time following cessation of therapy.
The results of physical examination, including rectal palpation and body condition assessment (body condition score 3/5), were
normal. Micturition was normal. Analysis of a urine sample collected by cystocentesis revealed that the urine was slightly concen-
trated (specific gravity 1.015), had a neutral pH and contained evidence of inflammation, most likely due to an infectious process
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(Table 1). Crystals were not observed. Aerobic culture of an aliquot of urine revealed significant numbers (>10 colony-forming
units/ml) of urease-producing Staphylococcus intermedius, which was susceptible to many antimicrobial agents. Results of a complete
blood count and serum biochemistry profile were normal (Table 1).
Problems identified on the basis of the animal assessment included bacterial urinary tract infection with staphylococci character-
ized by dysuria and pollakiuria, possible impaired urine concentrating capacity, and hematuria, pyuria, proteinuria and bacteriuria.

Assess the Food and Feeding Method
The dog was fed a commercial dry adult maintenance food free choice and offered commercial treats/snacks several times each day.
Questions
1. What is the anatomic site or sites of the bacterial urinary tract infection?
2. Are further diagnostic tests justified for this patient?

Answers and Discussion
1. Dysuria and pollakiuria suggest involvement of the lower urinary tract but formation of urine with a specific gravity of 1.015 in
absence of azotemia suggests that ascending infection may have involved the medullary portions of the kidney.
2. Additional diagnostic tests should be considered because: 1) the bacterial urinary tract infection appears to be recurrent, 2) the
sites of infection and inflammation have not been confirmed and 3) the predisposing causes of infection are unknown. There is
no evidence of diabetes mellitus or hyperadrenocorticism, both of which are frequently associated with recurrent bacterial urinary
tract infection. Another urinalysis is indicated to assess the concentrating capacity of the kidneys. Survey and contrast abdomi-
nal radiography and/or ultrasonography will help evaluate the patient for uroliths, neoplasia and anatomic abnormalities. These
imaging procedures will also assist in evaluation of the prostate gland.

Further Assessment
Results of a second urinalysis included a urine specific gravity of 1.021. Hematuria, pyuria, proteinuria and bacteriuria were still
present. Survey radiography and ultrasonography of the abdomen revealed a large urolith in the pelvis of the right kidney (Figures
1 and 2). Retrograde positive-contrast urethrocystography revealed normal size, shape and position of the lower urinary tract and
prostate gland. Double-contrast cystography revealed a few uroliths approximately 1 mm in diameter in the bladder. An intravenous
urogram revealed no evidence of outflow obstruction in the ureters (Figure 2).
Further Questions
1. On the basis of the available data, what is the most likely mineral composition of this patient’s uroliths?
2. Why were crystals not identified in the urine sediment even though the patient had multiple uroliths?
3. Outline a treatment and feeding plan for this dog.

Answers and Discussion
1. The mineral composition of the nephrolith and urocystoliths most likely is infection-induced struvite because: 1) staphylococci
may cause formation of struvite uroliths, 2) very large radiodense nephroliths are usually composed of infection-induced struvite,
3) the urinary pH was not acidic and 4) crystals associated with other types of uroliths were not detected.
2.The combination of risk factors necessary for struvite crystals to form was not present at the time urine samples were collected