A calyx is an individual cup-shaped chamber within the kidney where urine first collects after being produced by the kidney tissue. The kidneys contain multiple minor calyces that drain into two or three major calyces, which then merge to form the renal pelvis, the large collecting area that connects to the ureter. On ultrasound, normal calyces are not usually visible as distinct fluid-filled structures because they are collapsed. When they become dilated with fluid, it suggests an obstruction or other abnormality in the urinary drainage system. Recognizing dilated versus normal calyces is a fundamental skill in renal ultrasound.
Sonography Term