Diagnostic Ultrasound - Abdomen and Pelvis

Cystic Renal Mass
964
Differential Diagnoses: Kidney
DIFFERENTIAL DIAGNOSIS
Common
• Simple Renal Cyst
• Complex Cysts: Hemorrhagic, Infected, or Proteinaceous
• Renal Sinus Cysts
• Hydronephrosis
• Cystic Disease of Dialysis
• Autosomal Dominant Polycystic Kidney Disease
• Multicystic Dysplastic Kidney
• Cystic Renal Cell Carcinoma
• Localized Cystic Renal Disease
• Renal Abscess
• Renal Hematoma
Less Common
• Multilocular Cystic Nephroma
• Mixed Epithelial and Stromal Tumor
• Primary Renal Synovial Sarcoma
• Lymphangioma
• Perinephric Collection
• Tuberous Sclerosis
• von Hippel-Lindau Disease
• Arteriovenous Fistula/Malformation; Intrarenal Aneurysm
• Congenital Megacalyces
• Renal Lymphoma or Metastases
• Hydatid Cyst
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
• Cystic renal masses run the gamut from simple cyst to cystic
renal carcinoma
• Simple cysts are benign and require no follow-up
• Ensure that the lesion is truly a simple cyst
• Beware of technical artifacts producing internal echoes
within cysts such as
○ Reverberation from skin-transducer interfaces superficial
to cyst
○ High gain settings
○ Side lobe artifacts from adjacent tissue
• Posterior acoustic enhancement typically occurs with larger
lesions
○ May not be seen if cyst is very small
• Multiple tiny cysts may not be resolved
○ Instead may appear as an echogenic lesion due to
multiple reflective surfaces
• Complex cysts may represent complicated benign cysts or
cystic neoplasms including renal cell carcinoma
• Therefore, it is imperative to detect features that indicate
further imaging or follow-up
○ Look for solid components or mural nodules
○ Evaluate the entire wall of large cysts
○ Evaluate septa
○ CECT: CEMR or CEUS for further evaluation
○ Bosniak classification helps in guiding management
• May difficult to confirm origin of exophytic or large renal
cysts
• Cysts in upper pole of kidney may be difficult to
differentiate from suprarenal, hepatic (right), or splenic
(left) cysts
○ Try to delineate relationship during real-time imaging
• Determine if single cystic lesion or multiple lesions
• Consider syndromes with cysts if multiple bilateral renal
cysts in young patients
Helpful Clues for Common Diagnoses
• Simple Renal Cyst
○ Extremely common; increases with age
○ Well-defined, round or oval, smooth, and thin walled
○ Entirely echo free with posterior acoustic enhancement
○ No septum or solid component; no color Doppler flow
○ May exert mass effect on calyces if large
○ Location: Renal cortex, deep or superficial
• Complex Cysts: Hemorrhagic, Infected, or Proteinaceous
○ Thin, smooth internal septa
○ Internal echoes from hemorrhage, infection, or
proteinaceous debris
○ Calcified wall or septa
• Renal Sinus Cysts
○ Include peripelvic cysts and lymphangiectasia
○ Located in renal hilum
○ Surround and may compress renal pelvis but do not
communicate with collecting system
○ Can mimic hydronephrosis
○ Most are asymptomatic; rarely associated with
hematuria or hypertension
• Hydronephrosis
○ Dilated calyces connecting to dilated pelvis
○ Use color Doppler to distinguish from prominent vessels
• Cystic Disease of Dialysis
○ 3 or more cysts per kidney in patient with chronic kidney
disease and no history of hereditary cystic disease
○ May precede dialysis, almost inevitable after long-term
dialysis
○ Atrophic echogenic kidneys with loss of corticomedullary
differentiation
○ Cysts in both renal cortex and medulla, especially at site
of renal scars
○ Renal size may be enlarged due to multiple large cysts
– May resemble polycystic kidney disease, clinical
correlation needed
○ Increased risk of renal cell carcinoma (RCC): 3-7%
• Autosomal Dominant Polycystic Kidney Disease
○ Autosomal dominant inheritance, spontaneous mutation
in 10%
○ Massively enlarged, echogenic kidneys with lack of
corticomedullary differentiation
○ Multiple bilateral cysts of varying size
○ Intracystic hemorrhage/infection/milk of calcium
○ Mural calcification
○ Associated with cysts of other organs: Liver (75%),
pancreas (10%), spleen (5%)
• Multicystic Dysplastic Kidney
○ Congenital lesion discovered on prenatal ultrasound or
incidental finding
○ Multiple noncommunicating cysts of varying size
○ No communication to ureter
○ Usually unilateral, may be complete or segmental