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

The infundibulo-pelvic angle (IPA) is reportedly a predictor of successful ureteroscopy for lower pole renal stones, however there is uncertainty at which IPA success is likely. We therefore aimed to perform a meta-analysis and determine at which the angle of likely success and failure.

We performed a systematic review and meta-analysis as per Cochrane guidelines in accordance to the PRISMA statement. The review was registered with PROSPERO prior to commencement (ID: CRD42022296732). We included studies reporting on outcomes of ureteroscopy for lower pole stones, with IPA. We excluded patients undergoing alternative treatments for lower pole stones, anatomical abnormalities and studies with < 10 patients. We assessed bias with the Newcastle-Ottawa scale. We performed meta-analysis in R, and summarised the findings as per GRADE.

Overall, there were 13 studies included, with 10 included for meta-analysis. These studies covered n = 1964 patients (71% stone free). Overall, the stone free patients had a significantly less acute mean IPA (52^o ± 9^o), compared to the non-stone free patients (39^o ± 7^o), on meta-analysis (REM MD = -13.0, 95% CI: -18.7 to -7.2, p < 0.001). On examination of forest plots, at IPA < 30^o no patients were stone free, whilst > 50^o all were stone free. Risk of bias was moderate, and certainty of evidence was 'very low'.

With a very low certainty of evidence, we demonstrate that at an IPA of < 30^o no patient is stone free, whilst > 50^o all patients (in this review) are stone free. More evidence is therefore needed.