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484 Hydronephrosis

DIAGNOSIS each kidney; percutaneous nephropyelogra- Possible Complications
phy to assess structure of renal pelvis and • CKD/azotemia/uremia
VetBooks.ir Hydronephrosis is usually diagnosed by renal ○ Pyelectasia • Urinary tract rupture and uroabdomen
Diagnostic Overview
• Urinary tract infection
ureter
(septic peritonitis if urinary tract is infected)
○ Ureteral dilation or lack of filling (EU
imaging studies, including ultrasound or con-
only)
trast studies, in conjunction with recognition
of a functional or physical reason for urinary ○ May identify ectopic ureter Recommended Monitoring
tract obstruction. • CT scan with contrast • Ultrasound is repeated several weeks after
○ Findings of other imaging modalities may urinary obstruction is relieved. If hydrone-
Differential Diagnosis be confirmed on CT (e.g., ectopic ureter, phrosis persists after 6 weeks, changes are
• Pyelectasia: pyelonephritis, iatrogenic fluid uroliths) likely to be permanent.
diuresis (mild) • Renal scintigraphy or CT with contrast • Animals with permanent hydronephrosis are
• Renomegaly ○ Affected kidney contributes little to monitored for CKD (pp. 167 and 169) with
glomerular filtration rate. periodic urinalysis and culture, assessment
Initial Database • Other testing is aimed at characterizing of azotemia, electrolytes, and packed cell
• Digital rectal examination: lesions of the underlying cause of hydronephrosis (e.g., volume. Azotemic animals are monitored
urethra and bladder trigone may cause quantitative analysis of uroliths, imaging more intensively than nonazotemic animals.
hydronephrosis. studies to localize neurologic lesions con-
• Urethral catheterization: can rule out or tributing to reflex dyssynergia, cystoscopy PROGNOSIS & OUTCOME
confirm urethral obstruction from urolithiasis for bladder abnormalities or ectopic ureter).
• CBC: unremarkable; neutrophilia possible • Depends on extent of renal damage, underly-
if concurrent pyelonephritis TREATMENT ing cause and resolution of cause, duration,
• Serum biochemical profile: depending on and concurrent infection. Hydronephrosis
degree of obstruction and/or nephron loss, Treatment Overview can be associated with severe renal failure
azotemia, hyperphosphatemia, hyperkalemia, Hydronephrosis has no specific treatment. or may be an incidental finding.
metabolic acidosis, increased anion gap, Instead, obstruction of urine flow should be • Structural kidney changes may be irreversible.
increased symmetric dimethylarginine corrected when possible, and complications of
(SDMA) renal failure addressed. Treatment may not be PEARLS & CONSIDERATIONS
• Urinalysis: isosthenuria (e.g., if > 66% necessary for incidentally discovered (chronic)
nephron loss), sometimes hematuria, pyuria hydronephrosis. Comments
• Urine culture and sensitivity to rule out • Hydronephrosis is a consequence of obstruc-
infection Acute General Treatment tive urinary tract disease rather than a
• Blood pressure to rule out hypertension • Relieve ureteral or urethral obstruction (pp. primary disease.
• Abdominal radiographs: rarely renomegaly; 1174, 1175, and 1176). • Hydronephrosis can lead to CKD and
additional findings may include ○ Subcutaneous ureteral bypass increasingly uremia or may manifest only as subclinical
○ Urolithiasis available (cats especially) for acute ureteral pyelectasia.
○ Urinary bladder distention obstruction.
○ Prostatomegaly • Crystalloid fluid therapy for azotemia (pp. Prevention
○ Abdominal mass effect 23 and 169) Strategies that limit the formation of uroliths
Loss of contrast in retroperitoneal space or • Analgesia for abdominal pain (e.g., buprenor- are important for patients that have already
abdomen: phine 0.01 mg/kg IM, IV, or SQ q 6-8h) demonstrated a predisposition to urolithiasis
• Abdominal ultrasound • Address electrolyte disorders and acidosis. or those with known risk factors.
○ Pyelectasia • Address uremia (pp. 23 and 169).
Dog renal pelvis diameter: normal Technician Tips
■
= 1-3.8 mm (median 2 mm), fluid Chronic Treatment • Monitor urine output via litterbox use or
therapy = 1.3-3.6 mm (median, • Antibiotics if indicated by results of urine bladder size if no urinary catheter is in place.
2.5 mm), pyelonephritis = 1.9-12 mm culture and sensitivity Alert clinician if there are any concerns.
(median, 3.6 mm) ○ If infection cannot be cured medically and • Abdomen may be painful; use caution when
Cat renal pelvis diameter: normal contralateral kidney function is adequate, picking up patient.
■
= 0.8-3.2 mm (median, 1.6 mm), nephrectomy may be indicated to remove
fluid therapy = 1.1-3.4 mm (median, infected, poorly functioning kidney. Client Education
2.3 mm), pyelonephritis = 1.7-12.4 mm • Address underlying cause of structural Urinary tract obstruction is life-threatening.
(median, 4 mm) or functional urinary obstruction (e.g., Stranguria or oliguria should prompt immediate
○ ± Renomegaly, loss of medullary paren- therapeutic measures for urolithiasis, phar- veterinary attention.
chyma, hydroureter, uroliths, masses in macologic therapy of bladder atonia, reflex
ureter/bladder/prostate/urethra dyssynergia, ureteral stenting). SUGGESTED READING
D’Anjou MA, et al: Clinical significance of renal
Advanced or Confirmatory Testing Nutrition/Diet pelvic dilatation on ultrasound in dogs and cats.
• Additional testing is not usually required or • If obstruction secondary to urolithiasis, diet Vet Radiol Ultrasound 52(1):88-94, 2011.
beneficial. appropriate for stone type
• Excretory urography (EU)/intravenous • Animals that remain azotemic should be fed AUTHORS: Adam Mordecai, DVM, MS, DACVIM
EDITOR: Leah A. Cohn, DVM, PhD, DACVIM
pyelography (IVP): to assess perfusion of a renal-appropriate diet (p. 167).

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