Calyceal diverticulum
Updates to Article Attributes
Calyceal diverticula,alsoknown as pyelocalyceal diverticula, are outpouchings of the renal calyx or pelvis into the renal cortex. These diverticula are lined with transitional cell epithelium.
Epidemiology
Relatively uncommon, historically seen in 0.21% to 0.60% of intravenous urograms (IVU).
Associations
- gender: females are more commonly affected than men, with 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 haematuria, calculi, flank pain and/or recurring infection.
Pathology
They may be congenital or acquired. The most common theory for the congenital 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. Also, they may occur secondary to infection, rupture of renal cyst or vesicoureteric reflux 6.
There are two categories of calyceal diverticula:
- type I: more common, 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
Only a diverticulum containing milk of calcium will be visible on a plain radiograph. It appears as a meniscus-shaped density on an upright radiograph that changes its shape with changing position, i.e. either supine or decubitus radiographs.
Fluoroscopy
On intravenous urograms (IVU), calyceal diverticula fill on excretory phase and appear as opacified cystic cavities connecting with pelvicalyceal system.
Ultrasound
Calculi or layered dependent "milk of calcium" complicating a calyceal diverticulum appear echogenic on ultrasound, but only the former will cast an acoustic shadow.
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.
Calculi or layered dependent milk of calcium complicating a calyceal diverticulum will be hyperattenuating on an unenhanced CT.
Differential diagnosis
General imaging differential considerations include
- renal milk of calcium cysts
- renal epithelial cyst
- focal calyectasis, most commonly renal tuberculosis 4
-<li><a title="Renal epithelial cyst" href="/articles/renal-epithelial-cyst">renal epithelial cyst</a></li>- +<li><a href="/articles/renal-epithelial-cyst">renal epithelial cyst</a></li>
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