Sonographic "white line sign" for detection of minimal mucosal thickening in renal transplants.

It is important to detect minimal hydronephrosis in a renal transplant because early or low-grade obstruction is clinically significant. Similarly, it is equally important to detect minimal mucosal thickening of the collecting system because this finding indicates the presence of renal disease even though thickening itself is nonspecific as to etiology. Differentiating between minimal hydronephrosis and minimal mucosal thickening may be difficult. We have noticed that meticulous sonograms made with an ultrasound transducer placed perpendicular to the interface of two opposing surfaces of thickened mucosa will produce a bright linear echo which can help discover and distinguish between these two entities. We choose to call this echo complex the "white line sign."