Page 898 - Small Animal Clinical Nutrition 5th Edition

930 Small Animal Clinical Nutrition

Table 46-6. Clinical presentations of cats with various lower urinary tract diseases.*
VetBooks.ir Presentation Nonobstructive Obstructive Behavioral Urinary

Probable diagnoses periuria dysuria periuria** incontinence
FIC
Neurologic incontinence
Toileting preferences/
Urethral plugs
Uroliths Urethroliths aversions and/or Anatomic abnormalities
Infection Urethral strictures marking with or Partial obstruction
Neoplasia Functional obstruction without medical
Blood clots causes of lower
Foreign material urinary tract
disease (e.g., FIC,
uroliths, UTI, others)
Initial tests Urinalysis Abdominal radiographs Urinalysis Neurologic examination
Diagnostic imaging Urinalysis Diagnostic imaging Urinalysis
Diagnostic imaging
Ancillary tests Urine culture Serum biochemistry profile Urine culture Urine culture
Abdominal ultrasound Urine culture Abdominal ultrasound Abdominal ultrasound
Contrast Contrast urethrocystography Contrast Contrast
urethrocystography Complete blood count urethrocystography urethrocystography
Coagulation profile Intravenous urography
Complete blood count Cystoscopy
Key: FIC = feline idiopathic cystitis, UTI = urinary tract infection.
*Adapted from Lulich JP. FLUTD: Are you missing the correct diagnosis? In: Proceedings. Hill’s Symposium on Feline Lower Urinary Tract
Disease, 2007: 12-19 (www.hillsvet.com/conferenceproceedings).
**May occur with or without hematuria and signs of urinary tract inflammation.

Results of urinalysis are used to: 1) help determine underly-
ing cause(s) of lower urinary tract signs, 2) detect conditions
that may predispose to formation of uroliths or urethral plugs,
3) infer mineral composition of uroliths or urethral plugs
(Figure 46-6) and 4) evaluate response to treatment or preven-
tive measures. Hematuria is a common finding in cats with
most lower urinary tract disorders; however, it is uncommon in
cats with behavioral periuria (unless it results from a previous
medical disorder). Pyuria is uncommon in cats with nonob-
structive FIC and behavioral periuria and more often occurs
with urolithiasis, urethral obstruction and UTI (Kruger et al,
1991; Osborne et al, 1990).
Figure 46-6. Magnesium ammonium phosphate (struvite) crystals Several factors influence the number of crystals present in the
(left) typically are colorless, orthorhombic, coffin-like prisms. Struvite urine sediment. Because storage at room temperature or refrig-
crystals may have square or rectangular dimensions, vary in size,
may have three to six sides and often have oblique ends. Calcium eration of urine samples may cause in vitro crystal formation,
oxalate dihydrate crystals (right) typically are colorless and have a fresh urine samples should be evaluated ideally within 30 min-
characteristic octahedral or envelope shape; they resemble small utes of collection (Sturgess et al, 2001; Albasan et al, 2003).
squares with corners connected by intersecting diagonal lines. Other factors that affect the presence of crystalluria include
volume of urine centrifuged, centrifugation speed and volume
of sediment re-suspended and transferred to the microscope
with quantitative urine culture, microscopic examination of slide for evaluation. Consequently, it is difficult to attach clini-
unstained urine sediment was associated with only an 11% cal significance to the number of crystals observed. In addition
positive predictive value (i.e., the proportion of cats with a to evaluating crystal type, sediment should be evaluated for ten-
positive test that were correctly diagnosed) (Swenson et al, dencies of crystals to aggregate. Detection of large aggregates of
2004). Bacteria may also be difficult to visualize by routine struvite or calcium oxalate crystals is an important finding
microscopic examination of urine sediment. Approximately when monitoring effectiveness of preventive measures. Crystals
10,000 rod-shaped bacteria per ml of urine are required for only form when urine is supersaturated with crystallogenic
visualization by light microscopy in unstained preparations of materials.Therefore, crystalluria is a risk factor for formation of
urine sediment. Cocci may not be consistently detected if uroliths and urethral plugs. However, crystalluria alone is not
fewer than 100,000 per ml are present. Inability to detect bac- diagnostic for uroliths or urethral plugs (Box 46-1). Conversely,
teria in urine sediment, therefore, does not exclude their pres- urolithiasis is possible without associated crystalluria (Kruger et
ence. Staining of urine sediment with Wright’s, Gram’s or al, 1991). Crystalluria should be interpreted in the context of
new methylene blue stain may significantly improve detection the patient’s medical history, laboratory methods used and
of bacteriuria (Swenson et al, 2004a). complete diagnostic findings.