What are causes of focal areas of decreased flow within a kidney?
Most causes involve mass effect from a lesion such as a cyst, abscess, or tumor (benign or malignant) that has altered renal morphologic features. Scarring in the kidney from chronic pyelonephritis or chronic ureteral reflux can also lead to focally decreased renal flow. Other causes include renal infarction or a renal hematoma associated with trauma or surgery. Such abnormalities can be either unifocal or multifocal and can be more thoroughly evaluated with structural imaging techniques such as ultrasonography (US), computed tomography (CT), or magnetic resonance imaging (MRI).
