Retrograde Ureteroscopy in the Treatment of Caliceal Diverticula

7.1 Generalities

Caliceal (or pyelocaliceal) diverticula are intrarenal cavities ( Fig. 7.1 ) lined by urothelium ( Fig. 7.2 ), without secretion, that are passively filled with urine from the intrarenal tracts.

The diverticular cavity opens through the diverticulum’s neck into a calyx (most frequently) ( Fig. 7.3 ), into a caliceal infundibulum ( Fig. 7.4 ), or even into the renal pelvis.

The incidence of this malformation is relatively low, being discovered in 2.1–6 out of 1000 intravenous urographies in the adult population ( ). The analysis of groups of patients with caliceal diverticula published in the literature suggests a higher frequency in the upper caliceal group ( Table 7.1 ).

Table 7.1

Distribution of Diverticula in the Caliceal Groups

Author	Upper calyx	Middle calyx	Lower calyx
	12	12	7
	28	7	7
	12	4	6
Total	52	23	20

There were no significant differences regarding the incidence according to gender or side. There are numerous theories regarding the etiology of caliceal diverticula. The most likely one seems to be the theory that supports a congenital origin for diverticula ( ). According to this theory, pyelocaliceal diverticula originate in the grade 3–4 ureteral buds, incompletely resorbed during weeks 5–8 of intrauterine life. The absence of renal papillae opening into the diverticular cavity is due to this mechanism of incomplete resorption.

Other authors have tried to establish correlations between the origin of renal cysts and that of caliceal diverticula. Thus, the progression of diverticula to simple renal cysts through the obliteration of the lumen and their separation from the intrarenal tracts has been suggested ( ). In turn, enunciated an inversed theory of caliceal diverticula genesis through the rupture of a simple cyst or of a renal abscess in the collecting system. However, the histological differences between renal cysts (lined with cuboid epithelium) and caliceal diverticula (containing urothelium inside the cavities) show that these theories, though possible, are applicable only to some isolated cases.

suggested a mechanical-inflammatory mechanism for the production of diverticula. Thus, by studying a group of children with vesicoureteral reflux and urinary infection, he reported a higher incidence of caliceal diverticula than in the general population. However, disputed this theory, showing radiographic signs of pyelonephritis in only 17% of cases in a group of 72 consecutive patients with pyelocaliceal diverticula.

Several classifications have been proposed for pyelocaliceal diverticula, based on anatomical, radiological, or radio-endoscopic criteria.

Thus, classifies diverticula according to the insertion of the diverticular neck into:

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Type I – cavities communicating with a minor calyx or with its infundibulum
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Type II – cavities communicating with a major calyx or with the renal pelvis

According to the length and the opening of the neck, classifies diverticula into four types:

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Type 1– wide and short neck
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Type 2 – narrow and short neck
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Type 3 – narrow and long neck
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Type 4 – obliterated neck

Using anatomical, radiological, and endoscopic criteria, classifies any intrarenal tract stenosis (including also the diverticular necks in this group) as:

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Type I – neck/lumen that allows the passage of a metallic guidewire
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Type II – radiologically visible neck/lumen, but which cannot be passed by the metallic guidewire
•

Type III – completely obliterated neck/lumen

Diverticula can be single or multiple, with or without intradiverticular stones ( Fig. 7.5 ).

A particular form of diverticular lithiasis is the soft one, of the “milk of calcium” type ( Fig. 7.6 ) ( ). “Milk of calcium” stones represent approximately 0.6% of cases of urinary lithiasis ( ).

Isolated cases of patients with myxoid fibroepithelial polyps ( ) or intradiverticular transitional tumors have been reported ( ).

7.2 Indications of retrograde ureterorenoscopic approach for caliceal diverticula

Most caliceal diverticula are asymptomatic ( ) and are usually discovered incidentally. Some patients with caliceal diverticula may present lumbar pain, hematuria, or pyuria. In the series of patients reported in the literature, the incidence of intradiverticular lithiasis varies between 9.5% and 50% ( ). Less than half of the patients with symptomatic caliceal diverticula require surgical treatment. The indications for surgical treatment are represented by chronic pain, recurrent urinary tract infections, macroscopic hematuria, and progressive destruction of the renal parenchyma, regardless of the existence or not of intradiverticular stones ( ). The presence of stones is not an indication for surgical intervention in the absence of the other signs and symptoms mentioned previously.

Classically, open surgical interventions were the only therapeutic option. These were represented by partial or total nephrectomy, diverticulum resection, autologous fat filling, and neck suture, respectively partial resection of the diverticulum and parenchymal suturing after neck dilation. The development of endourological techniques currently offers a wide range of additional alternatives: retrograde ureterorenoscopic approach ( ; ), direct and indirect percutaneous approach ( ), laparoscopic approach ( ), or even SWL ( ).

Choosing the type of intervention depends on the position of the diverticulum, its dimensions, the presence and the dimensions of lithiasis, the available equipment, patient preference, and the surgeon’s experience.

Although direct percutaneous approach is a widely used minimally invasive method, retrograde ureterorenoscopic treatment may be a viable alternative for selected cases. The improvements to the flexible ureteroscopes, the use of the Ho:YAG laser, and the technological progress in the field of accessory instruments have led to this type of approach being used more and more frequently. The development of diverticula, especially in the upper caliceal group, creates the conditions for a relatively easy retrograde approach.

This method is generally reserved for symptomatic diverticula of small dimensions, up to 1.5 cm, with or without intradiverticular stones ( ). Retrograde approach is preferred in patients with caliceal diverticula located anteriorly, which are difficult to approach percutaneously ( ).

7.3 Technique particularities

7.3.1 Identifying the Diverticular Neck

The position of the pyelocaliceal diverticulum will be determined by fluoroscopy, by injecting a contrast medium through the working channel of the flexible ureteroscope.

The distal end of the flexible ureteroscope will be maneuvered under fluoroscopic control at the level of the pyelocaliceal system toward the opacified diverticulum ( Fig. 7.7 ).

In this stage, the diverticular neck will be endoscopically highlighted and a guidewire inserted through the working channel of the flexible ureteroscope will be placed at this level ( Fig. 7.8 ).

When the distal end of the guidewire is coiled at the diverticular level, the flexible ureteroscope is removed and reinserted alongside it.

7.3.2 Gaining Access to the Diverticular Cavity

The enlargement of the diverticular neck can be achieved through dilation using a balloon catheter up to 12 F, by Greenwald electrode incision, or in a more modern fashion by laser incision ( ; ).

Lasers with pulsed (such as the Ho:YAG laser) or continuous (such as the Nd:YAG laser) emission can be used. The Ho:YAG laser is preferred for incision ( Fig. 7.9 ) due to its safety (having a low tissue penetrability of just 0.5–1 mm) and also because it can be used subsequently for the lithotripsy of intradiverticular stones.

Multiple superficial incisions are made at 12, 3, 6, and 9 o’clock, which, compared with a single deep incision, have a reduced risk of bleeding by injuring an interlobar artery ( ). Because of these relations between the caliceal infundibula and the intrarenal arterial system, some authors recommend that incisions be performed preferably in the superior/inferior quadrants, and never in the anterior one ( ).

7.3.3 Lithotripsy and Intradiverticular Stones Extraction

Once access to the diverticulum’s cavity is gained ( Fig. 7.10 ), electrohydraulic ( Fig. 7.11 ) or laser lithotripsy of the stone is performed, and the fragments are eventually extracted with basket catheters or flexible forceps.