Revision 8 for 'Calyceal diverticulum'

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Calyceal diverticulum

Calyceal diverticula, also known as pyelocalyceal diverticula are congenital outpouchings from the renal calyx or pelvis into the renal cortex. These diverticula are lined with transitional cell epithelium.

Epidemiology

Relatively uncommon, seen in 0.21% to 0.60% of intravenous urograms (IVU).

Associations include

  • gender: females are more commonly affect than men by a ratio of 2:1
  • high incidence of stone formation due to urine stagnation

Clinical presentation

The majority of cases are asymptomatic and discovered incidentally on imaging. Up to 50%, though, present with hematuria, calculi, flank pain and/or recurring infection.

Pathology

The most common theory for the origin of calyceal diverticula is a failure of regression of the third and fourth-generation ureteric buds, as a result of obstructing stones or infection.

There are two categories of calyceal diverticula. Type I is more common and communicates with a minor calyx. Type II communicates with a major calyx or the renal pelvis and tends to be symptomatic.

Radiographic features

Plain radiograph

Plain abdominal radiographs will rarely show a meniscus-shaped calcification of radio-opaque milk of calcium within a diverticulum.

Ultrasound

A calyceal diverticulum complicated by calculi or layered dependent milk of calcium appears echogenic on ultrasound.

CT

On nephrographic phase contrast-enhanced CT, a calyceal diverticulum will have an appearance similar to that of a simple cyst. The diagnosis is made with certainty in the excretory phase, when the cystic structure fills with contrast material due to communication with the collecting system, and layering of contrast material is seen within. This helps differentiate it from a renal cyst, which does not connect with the collecting system.

A calyceal diverticulum complicated by calculi or layered dependent milk of calcium will be a hyperattenuating on an unenhanced CT.

Differential diagnosis

General imaging differential considerations include

 

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