Infundibular stenosis is a rare pathological entity that can be congenital or acquired ( ; ). The condition is the result of the obstruction of the caliceal infundibulum associated with hydrocalycosis, and requires a differential diagnosis with other pathological entities causing segmental dilations of the upper urinary tract: caliceal diverticulum and megacalycosis ( Table 11.1 ).
|Renal papilla is present|
|Caliceal diverticulum||Nonsecreting urothelial cavities that are filled passively with urine from the adjacent collecting system|
|Renal papilla is absent|
|Megacalycosis||Idiopathic caliceal dilation|
|Absence of infundibular stenosis|
Congenital infundibular stenosis is extremely rare and is usually associated with other dysplastic lesions of the urinary tract: multicystic renal dysplasia, contralateral renal agenesis, megaureter, and hydronephrosis. Most authors consider that this condition is secondary to the hypertrophy of the infundibular smooth muscle fibers or to extrinsic vascular compression ( ; ). Histopathological examination can reveal large areas of cystic dysplasia proximal to the stenosis, thus differentiating the congenital type from the acquired one ( ).
Acquired infundibular stenosis can be intrinsic or extrinsic. Extrinsic vascular compression (by crossing renal vessels at the upper pole) can cause an infundibular stenosis associated with Fraley syndrome ( ). Other etiological causes of extrinsic infundibular stenosis are represented by trauma or neoplastic lesions ( ). Secondary intrinsic stenoses may occur after ( ; ):
chronic inflammatory disorders (tuberculosis)
posttraumatic vicious scarring
The stones impacted in the caliceal infundibulum can cause an important secondary edema. The stone’s removal determines, in most cases, the remission of the edema with repermeabilization of the caliceal infundibulum, without the need for another therapeutic procedure. However, a secondary infundibular stenosis can occur in some cases after the treatment of an impacted stone. Hence, Parsons described a 2% incidence of infundibular stenosis after percutaneous nephrolithotomy ( ). The main risk factors for this complication are: prolonged intervention, large calculi (which required multiple procedures), and maintaining the nephrostomy tube for a longer period of time. The percutaneous access area is the most frequent site for the development of infundibular stenoses.
In cases with infundibular stenosis, the radiological examination shows segmental caliceal dilation and can be diagnosed by ultrasound, urography, or retrograde ureteropyelography. In patients with congenital stenoses, it is necessary to diagnose possible associated malformations (cardiovascular, gastrointestinal, bone and testicular cryptorchidism). In some cases, retrograde ureteroscopy with an eventual biopsy of the suspected lesions is necessary to exclude a malignancy that can determine infundibular stenosis ( ). Computed tomography can be useful for establishing the relationship between the studied area and the remaining renal parenchyma. Renal scintigraphy with forced diuresis can be useful for objectifying the caliceal infundibulum obstruction. The differential diagnosis includes other segmental caliceal dilations (megacalycosis), as well as mass lesions that can be localized at this level (parapyelic cysts and tumors).
Hydrocalycosis that is secondary to caliceal infundibular stenosis is characterized by the presence of normal urothelium that continues to produce urine, contributing to the development of symptoms. The main therapeutic indications are represented by:
decrease of renal function
Caliceal infundibular stenoses that are secondary to tuberculosis or lymphoma require specific treatment of the underlying disease. In cases without an obvious etiology, it is important to establish the type of infundibular stenosis as either acquired or congenital. The treatment of the unilateral congenital type does not seem to have obvious benefits over time ( ; ). The presence of bilateral hydrocalycosis can produce a secondary impairment of the renal function, sometimes requiring renal transplantation ( ). Untreated, the acquired type can determine hydronephrosis or progressive hydrocalycosis with the impairment of renal function ( ; ; ).
The treatment of infundibular stenosis is similar to that of caliceal diverticulum ( ; ). The approach can be antegrade or retrograde. Surgical treatment is very rarely used, being reserved for neglected cases with atrophic renal parenchyma (surgical or laparoscopic partial nephrectomy) ( ).
The treatment’s objective is the decompression of the dilated calyx, achieving its adequate drainage into the collecting system, and eventually the removal of the associated lithiasis ( ).
Preoperative preparation is standard, with associated urinary infections requiring adequate treatment (they represent a relative contraindication for surgical intervention).
Choosing the optimal surgical technique depends on various factors:
severity (degree) of the stenosis (observed radiologically)
location of the stenosis
Locating the stenosis (in relation to the position of the renal artery) is very important for safely performing the surgical intervention. In order to avoid damaging an arterial branch, incision in the longitudinal axis of the infundibulum is recommended.
The therapeutic alternatives are differentiated according to the severity of stenosis. Hence, in practice, there may be two situations: stenoses that can be catheterized (allowing guidewire catheterization) and complete stenoses.
In the case of stenoses that can be catheterized, the endoscopic approach can be antegrade or retrograde.
The localization of the ostium in the renal collecting system, the reduced invasiveness, and an increased maneuverability of flexible ureteroscopes represent important factors that have allowed the use of the retrograde approach on an increasingly larger scale. The most important step of the intervention is to identify, with a guidewire, the ostium of the stenosed caliceal infundibulum and its catheterization. Most authors recommend the use of an additional safety guidewire. There are various ways to achieve a large communication between the dilated calyx and the rest of the pyelocaliceal system:
balloon dilation ( ) ( Fig. 11.1 )