Category: Clinical Stones: Outcomes

MP13-9 - Assessment of residual stone fragments after retrograde intrarenal surgery

Fri, Sep 21
2:00 PM - 4:00 PM

Introduction & Objective :

Residual stone fragments after retrograde intrarenal surgery (RIRS) can cause symptoms and additional procedures. The best image method for the assessment of residual fragments is not a consensus in the literature. Noncontrast computed tomography (NCCT) is the gold standard for the evaluation of urinary stones, however, ionizing radiation from NCCT is deleterious and should be avoided as much as possible. The aim of this study is to define the most suitable approach to assess residual stone fragments after RIRS.


Methods :

Ninety two patients (115 renal units) submitted to RIRS for symptomatic kidney stones > 5 mm and < 20 mm or < 15 mm in the lower calyx diagnosed by NCCT were prospectively studied. Patients with kidney malformations, ureteral stenosis, previous ipsilateral endoscopic or open kidney surgery, hydronephrosis, indwelling double J stent and contraindications for RIRS were excluded. Residual stone fragments were assessed by endoscopic evaluation at the end of the procedure and by NCCT, ultrasound (US) and Kidneys-Ureter-Bladder X-ray (KUB) performed at the 90th postoperative-day (POD). NCCT was considered the gold standard for the evaluation of residual stone fragments after RIRS. Radiologists were blinded for the results of the different evaluation methods.


Results :

90th POD NCCT resulted stone free in 74.8% (86/115), 0 – 2 mm in 8.7% (10/115) and > 2 mm residual fragments in 16.5% (19/115) renal units. Stone free status by endoscopic evaluation at the end of RIRS was coincident to NCCT in 93.0% of the cases (40/43). There were no cases of residual fragments > 2 mm on NCCT if endoscopic evaluation resulted stone-free. Residual fragments were noted in 62.6% (72/115) renal units at endoscopic evaluation and in 25.2% (29/115) on 90th POD NCCT, resulting in a clearance rate of 59.7% (43/72). In all cases that endoscopic evaluation resulted residual fragments > 2 mm, US was correct accordingly to NCCT. US or KUB were not able to identify residual fragments between 0 – 2 mm. US misdiagnosed stone free renal units as residual fragments > 2 mm in 25.6% (22/86). However, the negative predictive value if US resulted stone free was 95.5%. KUB had only 31.6% (6/19) sensitivity to detect residual fragments > 2 mm and did not add sensitivity or specificity to US.


Conclusions :

In the follow-up imaging after RIRS, we suggest that if endoscopic evaluation resulted stone-free or residual fragments between 0 – 2 mm, a 90th POD NCCT should be performed and not US. Ultrasound may be used if endoscopic evaluation showed residual fragments > 2 mm.

Alexandre Danilovic

Urologist
Department of Urology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil
Sao Paulo, Sao Paulo, Brazil

Andrea Cavalanti

Radiologist
Department of Radiology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil
Sao Paulo, Sao Paulo, Brazil

Bruno Rocha

Radiologist
Department of Radiology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil
Sao Paulo, Sao Paulo, Brazil

Olivier O. Traxer

Professor
Sorbonne Universite, GRC n020 Lithiase Renale, AP-HP, Hospital Tenon, F-75020 Paris, France
Paris, Ile-de-France, France

Fabio Torricelli

Urologist
Department of Urology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil
Sao Paulo, Sao Paulo, Brazil

Giovanni Marchini

Urologist
Department of Urology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil
Sao Paulo, Sao Paulo, Brazil

Eduardo Mazzucchi

Head of Endourology Section
Department of Urology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil
Sao Paulo, Sao Paulo, Brazil

Miguel Srougi

Head of Department of Urology
Department of Urology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil
Sao Paulo, Sao Paulo, Brazil