Page 1690 - Cote clinical veterinary advisor dogs and cats 4th

850 Pyelonephritis

• Hematuria pyelonephritis); normocytic, normochromic TREATMENT
• Pollakiuria, stranguria (if concurrent lower nonregenerative anemia is possible with Treatment Overview
VetBooks.ir • Abdominal, lumbar, or general discomfort • Serum biochemical profile: often normal but The mainstay of treatment is therapy with
concurrent CKD.
UTI)
may demonstrate azotemia (elevated blood
(usually acute pyelonephritis)
appropriate antimicrobial drugs. It is often
• Recurrent lower UTIs (chronic pyelonephritis)
• Possible history of predisposing cause may be urea nitrogen [BUN], creatinine), hyper- a challenge to obtain a positive urine C&S
phosphatemia, hypokalemia or hyperkalemia,
result, despite renal infection. Because pyelo-
present (e.g., urinary catheterization, uroliths) and/or metabolic acidosis nephritis often occurs secondary to another
• Urinalysis: isosthenuria is common; disease process, recurrence is common unless
PHYSICAL EXAM FINDINGS bacteruria may be absent despite bacterial the predisposing condition can be addressed.
Exam may be normal, especially in the more urinary infection (emphasizing the value of Renal failure is addressed as needed (pp. 23,
common chronic form of infection. Abnormali- urine bacterial culture and antimicrobial 167, and 169).
ties, when present, may include susceptibility [C&S]) testing; occasionally,
• Fever (acute pyelonephritis) leukocyte casts (acute pyelonephritis), Acute General Treatment
• Dehydration pyuria, hematuria, and/or crystalluria are • Antimicrobial therapy
• Renomegaly (acute pyelonephritis) noted. ○ Antibiotic selection is based on C&S
• Renal asymmetry (chronic pyelonephritis) • Blood pressure: CKD associated with chronic results whenever possible. Interpret
• Abdominal/renal/lumbar pain (more often pyelonephritis may cause hypertension, and susceptibility data using serum rather
acute pyelonephritis) sepsis associated with acute pyelonephritis than urine antimicrobial breakpoints.
• Oral ulcerations/halitosis (if uremia) may cause hypotension. ○ Oral route is often adequate, but vomiting
• Debris or secretions (vomitus, saliva) in the • Abdominal radiographs: varied renal shadow or septicemia warrants parenteral therapy.
oral cavity (if uremia or sepsis) (normal, large, or small and irregular). ○ Pending results or if C&S is negative
• Bladder discomfort (if concurrent lower UTI) Radiopaque urinary (upper or lower) calculi despite clinical suspicion of pyelonephritis,
(suspect struvite) are sometimes present. therapy is indicated using a renally excreted
Etiology and Pathophysiology • Abdominal ultrasound: renal pelvic dilation bactericidal antibiotic with gram-negative
• Infectious agents (bacteria, fungi) usually ascend can occur (normal dog renal pelvis diameter spectrum. Examples:
to renal pelvis from lower urinary tract. Rarely, = 1-3.8 mm [median, 2 mm], on fluid ■ Fluoroquinolone (e.g., enrofloxacin
agents infect the kidneys hematogenously. therapy = 1.3-3.6 mm [median, 2.5 mm], 5-20 mg/kg q 24h IV, IM, or PO [dogs]
• Onset may be acute or insidious. pyelonephritis = 1.9-12 mm [median, or 5 mg/kg q 24h [cats], pradofloxacin
• Renal response to injury causes clinical signs. 3.6 mm]; normal cat renal pelvis diameter 5 mg/kg PO q 24h [cats], marbofloxa-
○ Acute infection results in nephritis (renal = 0.8-3.2 mm [median, 1.6 mm], on fluid cin, or orbifloxacin)
inflammation), causing renomegaly, renal therapy = 1.1-3.4 mm [median, 2.3 mm], ■ Augmented penicillin: amoxicillin-
pain, and often systemic signs of sepsis. pyelonephritis = 1.7-12.4 mm [median, clavulanate 22 mg/kg PO q 8-12h or
○ Acute or chronic infection causes nephro- 4 mm]) and may mimic hydroureter due ampicillin-sulbactam. Beta-lactams may
genic diabetes insipidus through bacterial to ureteral obstruction; renomegaly, or small be less efficacious in pyelonephritis than
toxin actions on antidiuretic hormone and irregular kidneys. Alterations in renal cystitis.
receptors. parenchymal echogenicity and other changes ■ Trimethoprim-sulfadiazine: only the
○ Chronic infection results in renal scarring, may be present. trimethoprim portion is likely to
smaller than normal kidneys, and loss of • Urine C&S: before treatment when suspicion achieve high renal concentrations.
renal function. of pyelonephritis exists, even if urine sedi- ○ For intact male dogs: antimicrobial that
○ Emphysematous pyelonephritis is rare. ment inactive penetrates blood-prostate barrier (e.g., flu-
• Infection may result in acute or chronic ○ In occult pyelonephritis, urine C&S can oroquinolone, trimethoprim-sulfadiazine)
renal failure or exacerbation of pre-existing be negative, and repeated C&S is justified ○ Although evidence regarding optimal dura-
CKD. if other features (e.g., renal ultrasound tion of antimicrobial treatment is lacking,
findings, intermittent pyuria) suggest due to issues of renal medullary blood
DIAGNOSIS pyelonephritis. flow, duration should be greater than for
bacterial cystitis. Traditionally, 3-6 weeks
Diagnostic Overview Advanced or Confirmatory Testing of treatment has been recommended, but
The diagnosis of pyelonephritis should be • Confirmatory tests are used rarely. Presump- much shorter courses are used in humans
considered for any animal with pyuria and/or tive diagnosis is based on compatible history, (7-14 days) and might be adequate in
bacteriuria (especially in the absence of lower physical, laboratory (including C&S), and dogs and cats.
urinary tract signs such as dysuria), polyuria/ ultrasonographic findings. ○ If initial urine sediment was active, a repeat
polydipsia, azotemia, CKD, chronic cystitis, • Ultrasound-guided pyelocentesis to obtain urinalysis ≈1 week after starting antibiotic
and/or immunocompromise. Although acute urine directly from the renal pelvis for C&S; therapy is recommended (ensure resolution
pyelonephritis may cause dramatic illness, begin with routine cystocentesis instead, and of bacteruria, pyuria).
chronic pyelonephritis with obscure clinical choose pyelocentesis if trying to pinpoint ○ If predisposing cause cannot be resolved,
signs occurs more commonly. source of infection to one kidney (rarely urine C&S should be repeated regularly
necessary). to identify future infections.
Differential Diagnosis • Blood cultures can be helpful, especially with ○ Fungal pyelonephritis may be more
• PU/PD (pp. 812, 1271, and 1442) acute pyelonephritis. difficult to eradicate than bacterial
• Bacteruria (p. 232) • Excretory urogram and/or cystourethrogram pyelonephritis.
• Pyelectasia (p. 483) to rule out anatomic abnormalities for recur- • Hospitalization is not indicated if the patient is
rent UTIs (abdominal ultrasound is used drinking and eating enough to maintain hydra-
Initial Database first) tion. For animals with sepsis (uncommon),
• Careful evaluation of vulvar/preputial/penile • Rule out other causes of recurrent UTI as fluid therapy and blood pressure maintenance
conformation, especially in obese (female) appropriate (e.g., hyperadrenocorticism). are key management factors (p. 907).
dogs, to identify anatomic abnormalities • Renal cortex biopsy: typically not helpful • Treatment of uremic renal failure starts with
• CBC: may be normal (chronic pyelonephri- due to localization of disease (renal pelvis isotonic crystalloid fluid therapy (pp. 23
tis) or show leukocytosis with left shift (acute and interstitium) and 169).
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