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Development and validation of a nomogram predicting intraoperative adverse events during robot-assisted partial nephrectomy

  • Gopal Sharma,
  • Milap Shah,
  • Puneet Ahluwalia,
  • Prokar Dasgupta,
  • Benjamin J. Challacombe,
  • Mahendra Bhandari,
  • Rajesh Ahlawat,
  • Sudhir Rawal,
  • Nicolo M. Buffi,
  • Ananthakrishnan Sivaraman,
  • James R. Porter,
  • Craig Rogers,
  • Alexandre Mottrie,
  • Ronney Abaza,
  • Khoon Ho Rha,
  • Daniel Moon,
  • Thyavihally B. Yuvaraja,
  • Dipen J. Parekh,
  • Umberto Capitanio,
  • Kris K. Maes,
  • Francesco Porpiglia,
  • Levent Turkeri,
  • Gagan Gautam

Publication: European Urology Focus, September 2022


Ability to predict the risk of intraoperative adverse events (IOAEs) for patients undergoing partial nephrectomy (PN) can be of great clinical significance.


To develop and internally validate a preoperative nomogram predicting IOAEs for robot-assisted PN (RAPN).

Design, setting, and participants

In this observational study, data for demographic, preoperative, and postoperative variables for patients who underwent RAPN were extracted from the Vattikuti Collective Quality Initiative (VCQI) database.

Outcome measurements and statistical analysis

IOAEs were defined as the occurrence of intraoperative surgical complications, blood transfusion, or conversion to open surgery/radical nephrectomy. Backward stepwise logistic regression analysis was used to identify predictors of IOAEs. The nomogram was validated using bootstrapping, the area under the receiver operating characteristic curve (AUC), and the goodness of fit. Decision curve analysis (DCA) was used to determine the clinical utility of the model.

Results and limitations

Among the 2114 patients in the study cohort, IOAEs were noted in 158 (7.5%). Multivariable analysis identified five variables as independent predictors of IOAEs: RENAL nephrometry score (odds ratio [OR] 1.13, 95% confidence interval [CI] 1.02–1.25); clinical tumor size (OR 1.01, 95% CI 1.001–1.024); PN indication as absolute versus elective (OR 3.9, 95% CI 2.6–5.7) and relative versus elective (OR 4.2, 95% CI 2.2–8); Charlson comorbidity index (OR 1.17, 95% CI 1.05–1.30); and multifocal tumors (OR 8.8, 95% CI 5.4–14.1). A nomogram was developed using these five variables. The model was internally valid on bootstrapping and goodness of fit. The AUC estimated was 0.76 (95% CI 0.72–0.80). DCA revealed that the model was clinically useful at threshold probabilities >5%. Limitations include the lack of external validation and selection bias.


We developed and internally validated a nomogram predicting IOAEs during RAPN.

Dr. Riccardo Giuseppe Bertolo

The dissemination of routine ultrasound screening has led to frequent detection of renal masses, which paired to the widespread availability of robotic platforms has exponentially broadened the indications to nephron-sparing surgical excision of small renal tumours. On the other hand, partial nephrectomy (PN) is one of the most exciting interventions among the spectrum of major urologic surgeries, including a non-negligible risk of complications. Such complications can be either intraoperative or postoperative, and the urologist should be aware of the differences in their classification and proper assessment.

The Vattikuti Collective Quality Initiative (VCQI) is an electronic prospective multinational collaborative database maintained by the Vattikuti Foundation for a variety of robotic procedures. Specifically, data are contributed by 18 centres from nine countries worldwide for patients with localised renal masses who undergo robot-assisted partial nephrectomy (RAPN).

In the observational study published by Sharma et al in European Urology Focus, the VCQI database was queried to develop first, and internally validate afterwards, a nomogram able to preoperatively predict the occurrence of intraoperative adverse events during  RAPN (PMID: 36153228). Intraoperative adverse events were defined as the occurrence of intraoperative surgical complications, blood transfusion, or conversion to open surgery/radical nephrectomy.

Among the 2114 patients in the study cohort, intraoperative adverse events were noted in 7.5% of the cases. Multivariable analysis identified R.E.N.A.L nephrometry score (odds ratio [OR] 1.13), clinical tumour size (OR 1.01), imperative/relative indication to partial (OR 3.9/4.2), Charlson comorbidity index (OR 1.17), and multifocal tumours (OR 8.8) as predictors of intraoperative adverse events and a nomogram with an estimated area under curve of 76%(95% CI 72–80) was built accordingly. Decision curve analysis revealed that the model was clinically useful at threshold probabilities >5%.

Notwithstanding the intrinsic bias relative to this kind of analysis, the study does represent a step towards the right direction. This nomogram can reliably inform the operating surgeon before surgery starts and help to identify patients at heightened risk of intraoperative adverse events. For example, a patient with a single renal mass (0 points) of 4 cm in size (2.5 points) with R.E.N.A.L. nephrometry score of 7 (5 points), and no comorbidities according to the Charlson’s index (0 points) candidate for elective (0 points) RAPN will approximately have an intraoperative adverse events risk of 5%. The same patient would see her/his risk raised to 17-18% if indication to PN was imperative or R.E.N.A.L. score 11. But the crucial point in this setting, beyond the mere prediction of the likelihood of intraoperative complications, is how to report them.

Efforts have recently been made to standardise the grading of intraoperative adverse events. However, intraoperative adverse events classification systems are rarely used and therefore their reporting was remaining heterogeneous, and lacking consistency.

In recent years, the European Association Urology (EAU) ad hoc panel for complications have contributed at improving the collection of postoperative outcomes, with related improved accuracy of surgical data (PMID: 31787430).

A similar strategy is being applied to the collection of intraoperative adverse events by the Intraoperative Complications Assessment and Reporting with Universal Standards (ICARUS) Global Collaboration (PMID: 35177353).

The primary goal of the ICARUS project is to provide guidance and guidelines for reporting of intraoperative complications in surgical research papers, a sort of a list of criteria that should be met when researchers or clinicians report intraoperative complications as an outcome of interest. This has been achieved first via a modified Delphi consensus approach performed among experienced urologic surgeons within the Italian Group for Advanced Laparoscopic and Robotic urologic Surgery (AGILE).

Researchers collecting data and publishing in the field of partial nephrectomy should be aware that such guidelines can be found in the EQUATOR network. There are 46 guidelines for “surgery” in the network, and the ICARUS is the only one regarding the report of intraoperative complications.

We underline that this represents an initial step in order to standardise definitions and reporting of intraoperative complications. It will require further validation specific for urologic surgical procedures.