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778.e2 Perirenal Pseudocysts

Perirenal Pseudocysts Client Education
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kidney or proximal ureter (identify and
BASIC INFORMATION
correct source of leakage). renal and ureteral compression. Uriniferous
pseudocysts may require surgical intervention.
Definition
Collection of fluid (usually transudate but DIAGNOSIS Acute General Treatment
sometimes urine) between the renal capsule • If transudative pseudocyst, percutaneous
and kidney; pseudocysts may be unilateral or Diagnostic Overview drainage or surgical intervention
bilateral Ultrasonographic identification of hypoechoic • If uriniferous, identify (i.e., by excretory
fluid between the renal capsule and parenchyma urography) and correct source of urine
Synonyms strongly supports the diagnosis but does not leakage.
Perinephric pseudocyst, capsulogenic renal cyst, usually identify a cause.
capsular cyst, pararenal pseudocyst, capsular Chronic Treatment
hydronephrosis, pseudohydronephrosis Differential Diagnosis • Repeated percutaneous drainage of transuda-
For enlarged kidneys: perinephric abscess, tive pseudocysts
Epidemiology renal lymphoma or other neoplasia, ureteral • Surgical resection (laparotomy or laparos-
SPECIES, AGE, SEX obstruction with hydronephrosis, feline infec- copy) of pseudocyst ± omentopexy
• Rare in cats; extremely rare in dogs tious peritonitis, hematoma, polycystic kidney • Treat existing bacterial cystitis, if present.
• Older cats; male cats may be overrepresented disease, and compensatory hypertrophy (NOTE: • With transudative pseudocysts, treat appro-
abscess, neoplasia other than lymphoma, ure- priately for chronic kidney disease.
RISK FACTORS teral obstruction, hematoma, and compensatory • With uriniferous pseudocysts, surgical
• Chronic kidney disease (transudative hypertrophy are more commonly unilateral than intervention
pseudocysts) bilateral) • Nephrectomy should be avoided if possible
• Trauma, obstruction, neoplasia of renal pelvis when renal function is compromised. It
or ureter causing urine leakage (uriniferous Initial Database may become necessary if persistent ascites
pseudocysts) • CBC: possibly nonregenerative anemia of develops after surgical resection of pseudocyst
chronic kidney disease or there is reason to believe neoplasia is
ASSOCIATED DISORDERS • Serum biochemistry profile: usually evidence causative (e.g., thick, irregular capsule on one
• Chronic kidney disease of mild to moderate kidney disease (e.g., kidney).
• Urinary tract infection azotemia, hyperphosphatemia)
• Urinalysis: isosthenuric or minimally Nutrition/Diet
Clinical Presentation concentrated urine specific gravity For animals with chronic kidney disease, a
HISTORY, CHIEF COMPLAINT • Urine culture: often positive even in the protein-restricted renal diet is appropriate.
• Usually abdominal enlargement/abdominal absence of pyuria
mass (noted by owner or incidental finding • Abdominal radiographs: unilateral or bilateral Possible Complications
during exam) renomegaly • Urinary tract infection
• Less frequently: weight loss, vomiting, • Ascites may be a complication of pseu-
anorexia, polyuria, and polydipsia Advanced or Confirmatory Testing docyst removal, occasionally necessitating
• Abdominal ultrasound is method of choice nephrectomy.
PHYSICAL EXAM FINDINGS to confirm diagnosis. Transudative and • Hydrothorax due to pseudocyst has been
Palpable abdominal mass (renomegaly; common uriniferous pseudocysts are characterized reported in a single cat.
but depends on size of cyst) ± thin body by an accumulation of completely anechoic
condition fluid between renal parenchyma and capsule. Recommended Monitoring
Septations, particulate matter in the perirenal • Monitor as for chronic kidney disease.
Etiology and Pathophysiology fluid, and other variations suggest a diagnosis • Repeat ultrasound exam periodically
• Incompletely understood pathophysiology other than perirenal pseudocysts. after percutaneous drainage or surgical
• Lack of epithelial lining in fibrous sacs means • Excretory urography if ultrasound is pseudocyst removal; frequency of repeat
that they are not true cysts. unavailable. Decreased renal function may ultrasound depends on rapidity of fluid
• Renal interstitial fibrosis may impair venous result in poor contrast study. Small risk reaccumulation
and lymphatic drainage, causing transudate to of contrast-induced kidney injury/renal
escape the renal parenchyma and accumulate failure. PROGNOSIS & OUTCOME
under the capsule, forming a transudative • If the diagnosis remains in question
pseudocyst. after ultrasound, aspiration of anechoic/ • Prognosis variable, generally in the range of
• Uriniferous pseudocysts may form when hypoechoic region for cytologic analysis months to years.
damage to the renal parenchyma, pelvis, or can differentiate pseudocyst from perinephric • Prognosis is better if associated chronic
ureter allows urine to leak between the renal abscess, hematoma, or lymphoma. kidney disease is IRIS stage 1 or 2, worse if
capsule and renal parenchyma. • Concentration of creatinine is higher in fluid stage 3 or 4.
• The distinction between transudative and from uriniferous pseudocysts than concurrent • Median survival after surgery (capsulectomy)
uriniferous pseudocysts may be useful with serum creatinine concentration. is 9 months, with a wide range.
respect to initial management. Transudative • Prognosis apparently worse for cats treated
pseudocysts suggest chronic kidney disease TREATMENT with nephrectomy
(International Renal Interest Society [IRIS] • No clear generalization regarding prog-
stage 2-4; consider appropriate treatment), Treatment Overview nosis for transudative versus uriniferous
whereas uriniferous pseudocysts suggest Transudative pseudocysts may be managed pseudocysts
physical disruption of the integrity of the conservatively, with the goal of preventing

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