Caliceal diverticula are “eventrations of the upper collecting system, lying within the renal parenchyma and communicating with the main collecting system via a narrow channel.”<sup>5 Wulfsohn M.A. Pyelocaliceal diverticula J Urol 1980 ;  123 : 1

Cliccare qui per andare alla sezione Riferimenti</sup> They are lined by transitional cell epithelium but do not directly receive drainage from a renal papilla. Noted in 0.5% of the population, caliceal diverticula are clinically important only when pain, hematuria, or infection occur, which in most cases is associated with calculi.

A hydrocalyx is a renal calix drained by an obstructed infundibulum. The obstruction may be congenital or acquired. As is true for caliceal diverticula, hydrocalyces are clinically important only when pain, hematuria, or infection occur, with or without calculi. The presence of renal parenchyma draining through a papilla directly into the hydrocalyx necessitates different therapeutic considerations than a caliceal diverticulum. If a procedure that closes off the connection to the remainder of the collecting system is chosen (i.e., laparoscopy), the presence of a hydrocalyx necessitates ablation or removal of any remaining parenchyma excreting into the hydrocalyx. In a caliceal diverticulum, this maneuver is not necessary because no urine is excreted directly into the cavity. Although the distinction between the two entities is usually apparent, occasionally it is problematic. Careful inspection of the intravenous urogram with regard to caliceal configuration helps to make the correct diagnosis.