Calyceal diverticulum is a relatively uncommon cyst-like lesion, often discovered incidentally during ultrasound examination of the kidneys. Calyceal diverticulum is a urine-containing cavity within the renal parenchyma, communicating with the collecting system through a narrow channel. ^[1]

• Two types are identified:
  • One is related to a minor calyx and usually located in the upper pole
  • Other is connected with the pelvis or a major calyx in the central portion of the kidney.
• The majority of calyceal diverticulum are small and asymptomatic, and do not require any treatment.
• Calyceal diverticulua may rarely cause urinary tract infection, renal colic, pyuria, hematuria or hypertension.
• Mobile calculi and milk of calcium are characteristic findings in calyceal diverticulum.

• Ultrasound examination suggests the diagnosis of calyceal diverticulum and it has a variable appearance.
• The diverticulum may appear as a cyst-like lesion, indistinguishable from a simple cyst.
• Recognition of mobile echogenic material within such a cyst-like structure is considered characteristic of milk of calcium. A cyst-like mass with milk of calcium is presumed to be a calyceal diverticulum.

• CT has an important role in the presence of a complicated cystic mass diagnosed by ultrasound without the characteristic features of calyceal diverticulum.
• The demonstration of the layering of contrast medium on delayed images is pathognomonic of these lesions.
• The patency of the diverticulum is demonstrated by the gradual opacification on delayed images.

Images courtesy of RadsWiki

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  CT: Calyceal diverticulum
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  CT: Calyceal diverticulum

• Goldminer: Calyceal diverticulum