Page 681 - Small Animal Internal Medicine, 6th Edition

CHAPTER 38 Clinical Manifestations of Urinary Disorders 653

a single large calculus can be difficult to differentiate from a
BOX 38.2 tumor or large blood clot. Rectal palpation should be per-
VetBooks.ir Causes of Dysuria formed in all dysuric patients, both male and female. Not
only is rectal examination important to evaluate the prostate
• Inflammatory disease
• Urinary tract infection gland in males, but it allows the identification of urethral
tumors and proliferative urethritis in female dogs. The
• Feline idiopathic cystitis, urethritis (idiopathic feline perineum should be inspected for perineal hernia, and the
lower urinary tract disease) penis should be extruded completely to look for lesions such
• Chemically induced inflammation (e.g., as transmissible venereal tumor in male dogs.
cyclophosphamide-induced cystitis)
• Polypoid cystitis POLYURIA AND POLYDIPSIA
• Proliferative urethritis (granulomatous urethritis)
• Urolithiasis Normal water intake in dogs may be as high as 60 to 90 mL/
• Cystic calculi kg/day; maximal normal water intake in cats is 45 mL/kg/
• Urethral calculi day. Polyuria and polydipsia typically are reported simulta-
• Neoplasia neously and, with the exception of dogs with psychogenic
• Transitional cell carcinoma of bladder or urethra polydipsia (PPD; see later), polydipsia usually occurs in
• Prostatic neoplasia response to polyuria. The presence of polydipsia can be doc-
• Vaginal neoplasia umented by having the owner measure the animal’s water
• Trauma intake at home, but this is more practical in dogs than in cats.
• Bladder or urethral rupture Normal water intake is more variable than urine output
• Urethral stricture (previous trauma or surgery) because of variation in several factors, including ambient
• Neurogenic disorder
• Reflex dyssynergia temperature and respiratory evaporative loss of water, exer-
• Other cise level, water content of food, fecal water content, age, and
• Perineal hernia physiologic state (e.g., pregnancy, lactation). Normal urine
production in dogs and cats is 26 to 44 mL/kg/day.
Polyuria and polydipsia can be caused by several disor-
ders, notably diseases of the kidney and endocrine system.
incontinent because they find urine in inappropriate loca- In many cases, the pathophysiology of PU-PD is multifacto-
tions in the house. Although incontinent dogs often leave rial (Table 38.1). The history should always include informa-
wet spots where they have been lying down, dogs with poly- tion about drugs that the animal may have been given
uria and polydipsia (PU-PD) urinate voluntarily but in inap- that could contribute to PU-PD, especially corticosteroids
propriate locations and at inappropriate times because they (administered by any route, including topically) and diuret-
are not allowed outside frequently enough to accommodate ics. Pollakiuria must be differentiated from polyuria because
their large volume of urine production. A careful history is some owners erroneously conclude that because an animal
therefore very important for understanding the problem. is urinating more frequently, it must be producing more
Dogs and cats with dysuria assume the normal posture urine. Animals with polyuria may have increased frequency
for urination but spend an inordinate amount of time of urination, but each urination consists of a large volume
attempting to urinate, often passing only small volumes of and there is no evidence of stranguria. Nocturia often accom-
urine. They shift position, get up, move to another location, panies polyuria and sometimes is the first sign detected by
and posture repeatedly. Even with an empty bladder, mucosal the dog’s owner.
irritation results in repeated unsuccessful attempts to urinate. Routine urinalysis, including determination of the USG,
Cats with urethral obstruction sometimes adopt a distressed is the logical starting point for the diagnostic evaluation
yowling vocalization during attempts to urinate. It is impor- of an animal with PU-PD. The USG of dogs can vary
tant in this clinical situation to evaluate the animal for the widely throughout the day, but the highest USG (usually
presence of urethral obstruction. Complete urethral obstruc- >1.035–1.040) typically is found in the morning, before the
tion is readily identified during abdominal palpation by the dog eats and drinks. USG varies less throughout the day in
presence of a large, turgid, painful bladder, whereas a small, cats, and cats typically have moderately concentrated urine
painful bladder suggests cystitis without obstruction. when eating dry food (usually ≥1.035). USG values of 1.050
Caution should be taken to avoid excessive pressure when to 1.076 and 1.047 to 1.087 occur in normal dogs and cats,
palpating a bladder that is suspected to be obstructed. respectively, deprived of water until signs of dehydration
Observing the animal urinate can be valuable for identify- have developed. Generally, a USG of 1.040 or higher is
ing the problem as dysuria. Attempting to pass a urinary expected in sick dogs or cats that are dehydrated. Finding a
catheter allows the clinician to determine quickly whether relatively high USG (>1.025) would cast doubt about the
the urethra is patent or obstructed. Masses and calculi are accuracy of the history in an animal presented for evaluation
most easily detected by palpation when the bladder is empty of PU-PD. If the USG at presentation is in the hyposthenuric
or only partially full. The presence of many small cystic (<1.007) or isosthenuric (1.007–1.014) range, a minimum
calculi generates a crepitant sensation on palpation, whereas database of a complete blood count, serum biochemistry