Calyceal Diverticula: A Comprehensive Review

Calyceal diverticula are rare outpouchings of the upper collecting system that likely have a congenital origin. Stones can be found in up to 50% of calyceal diverticula, although, over the combined reported series, 96% of patients presented with stones. Diagnosis is best made by intravenous urography or computed tomography urogram. Shock wave lithotripsy (SWL) is an option for first-line therapy in patients with stone-bearing diverticula that have radiologically patent necks in mid- to upper-pole diverticula and small stone burdens. Stone-free rates are the lowest with SWL, although patients report being asymptomatic following therapy in up to 75% of cases with extended follow-up. Ureteroscopy (URS) is best suited for management of anteriorly located mid- to upperpole diverticular stones. Drawbacks to URS include difficulty in identifying the ostium and low rate of obliteration. Percutaneous management is best used in posteriorly located mid- to lower-pole stones, and offers the ability to directly ablate the diverticulum. Percutaneous nephrolithotomy remains effective in the management of upperpole diverticula, but carries the risk of pulmonary complications unless subcostal access strategies such as triangulation or renal displacement are used. Laparoscopic surgery provides definitive management, but should be reserved for cases with large stones in anteriorly located diverticula with thin overlying parenchyma, and cases that are refractory to other treatment. This article reviews the current theories on the pathogenesis of calyceal diverticula. The current classification is examined in addition to the current diagnostic methods. Here we summarize an extensive review of the literature on the outcomes of the different treatment approaches.Key words: Calyceal diverticula, Percutaneous nephrostolithotomy, Laparoscopic surgery, Shock wave lithotripsy, UreterorenoscopyCalyceal diverticula are eventrations of the upper collecting system lying within the renal parenchyma.¹ These nonsecretory outpouchings are lined by transitional cell epithelium and communicate with the main collecting system via a narrow channel, allowing for passive filling with urine. They were first described in 1841 by Rayer in “Traitements des maladies des reins.”² Thought to be either cysts or localized hydronephrosis, he used the term kyste urinaire to describe his finding of intrarenal urine-containing cavities that communicate with calyces. Other investigators reported similar findings and—depending on location and postulated etiology—described them as pelvic cysts,³ peripelvic cysts,⁴ pyelorenal cysts,⁵ pyelosynaptic cysts,⁶ pyelogenous cysts,⁷ hydrocalicosis,⁸ cystic dilatations of the calyx,⁹ congenital cortical cysts,¹⁰ congenital cystic dysplasia,^4,11 calyceal pseudocysts,¹² juxta-calyceal cysts,¹³ pelvic diverticula, ¹⁴ congenital diverticula of the calyx,¹⁵ and finally, calyceal diverticula.^16–18 Prather is credited with coining the term and the definition of calyceal diverticulum that we use today.