Endourological Options for Small (< 2 cm) Lower Pole Stones — Does the Lower Pole Angle Matter?

Abstract

Purpose of Review Small renal stones in the lower pole are often difficult to treat. The angle of the lower pole to the renal pelvis (lower pole angle) is a limiting factor to rendering the patient stone free. This review explores the definitions of the lower pole angle, the various treatment options available, and how outcomes are influenced by the angle. Recent Findings It is clear the lower pole angle definition varies widely depending on described technique and imaging modality. However, it is clear that outcomes are worse with a steeper angle, especially for shock wave lithotripsy and retrograde intrarenal surgery (RIRS). Percutaneous nephrolithotomy has similar reported outcomes to RIRS, and there is limited evidence it may be superior for steeper angles over RIRS. Summary Lower pole stones can be technically challenging and adequate assessment prior to choosing operative approach is key.

Effect of infundibulopelvic angle on outcomes of ureteroscopy: a systematic review and meta-analysis

“…In this review, there were a wide range of stone free definitions including a range of modalities, fragment sizes and follow-up intervals. There is less certainty in the literature about the gold standard definition of the IPA or lower pole angle [ 7 ]. To date there are five methods of ascertaining the IPA, all of which differ slightly [ 26 ].…”

“…One such aspect is the infundibulopelvic angle (IPA), which is often defined as “the inner angle formed at the intersection of the ureteropelvic axis and the central axis of the lower pole infundibulum” [ 5 , 6 ]. It has been suggested that the IPA is a predictive factor for achieving stone free status following ureteroscopy [ 7 ]. Although, the definition of ‘stone free’ varies from no fragments to fragments < 4 mm [ 8 ].…”

Der 1 cm UKG-Stein: ESWL, URS oder Mini-PCNL? Leitlinien versus Realität

“…Ein umfassender, systematischer Review der Literatur der letzten 25 Jahre von Lovegrove et al von 2022 [6] [7]. In den meisten Studien ist ein spitzer, pelviko-infundibulärer Winkel bei der ESWL von Unterpolsteinen mit schlechteren Ergebnissen für die Steinfreiheit assoziiert [8]. Werden Kollektive mit Nierensteinen unterschiedlicher Lokalisationen untersucht, scheint die Steinlokalisation im unteren Kelch bei der ESWL eher ein negativer Prädiktor der Steinfreiheit zu sein [9].…”