Table 1. Characteristics of benign and complex renal cysts

Benign renal cyst

Complex renal cyst

Round or oval Irregular contours
Echolucent Variable echogenicity
Thin walled Thick walled
Clearly delineated Ill defined irregular contours
   smooth contours
Sharply demarcated Posterior wall not clearly demarcated
   posterior wall
Sound wave amplification No sound wave amplification behind
   behind the cystic renal    the cystic renal mass*
   mass
Typical lateral extinction No lateral extinction of the sound
   of the sound wave/    wave/no lateral shadowing*
   lateral shadowing
No calcification Calcification*
No septa Septa*
No Doppler signals from Doppler signals from within the cyst
   within the cyst

* Not obligatory.