Diagnostic Ultrasound - Abdomen and Pelvis

Complex Renal Cyst
Diagnoses: Urinary Tract
TERMINOLOGY
• Benign, fluid-filled nonneoplastic renal lesion not meeting
criteria of simple renal cyst
• Bosniak classes II, IIF, and III
IMAGING
• Round, oval, or irregular-shaped anechoic lesion
• Hemorrhagic cyst: Appearance varies with age of blood
• Proteinaceous cyst: May contain low-level echoes, with
bright reflectors or even layers of echoes
• Infected cyst: Thick wall with scattered internal echoes ±
debris-fluid level
• Calcified cyst: Wall or septal calcification ± shadowing
• Neoplastic features: Solid mural or septal nodules, irregular
wall, or irregular septal thickening
• Complex cysts should be evaluated with CEUS, CECT, or
CEMR for decision of surgical intervention
• CEUS: Increased sensitivity for detecting malignancy
compared with unenhanced US and CECT
KEY FACTS
• Contrast uptake within cystic lesion on CEUS is suspicious
for malignancy (other than a few bubbles in thin smooth
septa or wall)
TOP DIFFERENTIAL DIAGNOSES
• Renal cell carcinoma
• Multilocular cystic nephroma
• Localized cystic disease
• Renal abscess
• Renal metastasis
• Renal lymphoma
DIAGNOSTIC CHECKLIST
• Correct imaging classification of cystic masses is key to
management
(Left) Transverse US shows a
near anechoic lesion other
than thin internal septations
st, which did not have flow on
color Doppler. There are no
internal nodules, wall, or
septal thickening; this
corresponds to a Bosniak II
lesion. (Right) Longitudinal US
shows a cyst ſt with
dependent, layering echogenic
material st with posterior
shadowing , consistent with
milk of calcium. In the absence
of internal septations or
nodularity, this is consistent
with a minimally complex cyst
(Bosniak II).
(Left) Longitudinal US of the
right kidney shows an upper
pole cyst ſt with a small
echogenic peripheral nodule
st. Color Doppler does not
show internal flow; however,
the presence of a nodule
warrants follow-up (Bosniak
IIF). (Right) Longitudinal US
shows a mixed echogenicity
cystic lesion with layering
echogenic material st and
posterior acoustic
enhancement . The findings
are consistent with a
hemorrhagic cyst although
contrast-enhanced imaging is
suggested to confirm the
absence of malignancy.
466