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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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