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Surgical management and outcomes of renal tumors arising from horseshoe kidneys: results from an international multicenter collaboration

  • Eduard Roussel,
  • Giovanni Tasso,
  • Riccardo Campi,
  • Maximilian C Kriegmair,
  • Önder Kara,
  • Tobias Klatte,
  • Umberto Capitanio,
  • Riccardo Bertolo,
  • Alexandre Ingels,
  • Selcuk Erdem,
  • Loïc Baekelandt,
  • Maria C Mir,
  • Idir Ouzaid,
  • Nicola Pavan,
  • Benoit Beuselinck ,
  • Mauro Gacci,
  • Andrea Minervini,
  • Alessandro Volpe,
  • Maarten Albersen,
  • Young Academic Urologists (YAU) Renal Cancer Working Group

Background

Despite being the most frequent renal fusion anomaly, tumors arising from horseshoe kidneys (HSKs) are extremely rare and management guidance is lacking.

Objective

To evaluate the perioperative, oncological, and functional outcomes of surgically treated HSK tumors.

Design, setting, and participants

A retrospective, multicenter cohort study of 43 HSK tumors in 40 patients was conducted, and technical description of the surgical approach has been provided.

Surgical procedure

Surgical resection of renal tumors arising from HSKs was performed either via open surgery or via minimally invasive surgery (MIS).

Measurements

We analyzed patient and tumor characteristics as well as surgical technique, and functional and oncological outcomes.

Results and limitations

Eight patients were treated by MIS and 32 by open surgery. One patient (2.5%) experienced an intraoperative complication and 13 patients (32.5%) experienced postoperative complications, of which three (7.5%) were Clavien-Dindo ≥3 complications. Surgical margins were positive in two tumors (4.7%). The most frequent histology was clear-cell renal cell carcinoma (46.5%). The median follow-up was 51 (interquartile range [IQR] 17–73) mo. The 5-yr overall, cancer-specific, and recurrence-free survival rates were 81.2%, 86.8%, and 83.1%, respectively. The percent decreases in estimated glomerular filtration rate at discharge and the last follow-up were 15% (IQR 4–26%) and 17% (IQR 1–31%), respectively. Limitations include the cohort’s retrospective nature, heterogeneity, and small sample size.

Conclusions

Surgical management of tumors in HSKs can be approached via both open surgery and MIS, with maximal preservation of functional renal parenchyma. In this cohort, rates of complications, positive surgical margins, and renal functional decrease were acceptable, considering the anatomical complexity of these kidneys and tumors. These tumors display great variation in histological subtypes. Meticulous presurgical planning, taking advantage of advanced imaging techniques, can aid in achieving good outcomes.

Commented by Dr. Eduard Roussel

Although horseshoe kidneys are not uncommon in the general population, there has been very little research on renal tumours developing in these organs and their subsequent disease management, which could be complicated by this kidney fusion anomaly. Only a very small number of case reports have described such cases. In an effort to address this lack of knowledge, we have collected data across multiple international referral centres to study this very rare disease entity.

In our results, we have included 40 patients harbouring 43 renal tumours and described their surgical management. Given the rarity of this disease, the inclusion period was relatively broad, resulting in most patients being managed with open surgery. However, urologists have a proud tradition of pushing boundaries and the growing experience with minimally invasive and robot-assisted surgery has led to the possibility of even the most complex cases being managed with minimally invasive surgery. The use of advanced technology such as indocyanine green and three-dimensional augmented reality is applicable to minimally invasive surgery. In the current cohort, eight patients were treated with minimally invasive surgery and 32 with open surgery.

Three patients (7.5%) experienced a high-grade postoperative complication and two tumours (4.7%) had positive section margins. Five-year-overall, cancer-specific and recurrence-free survival was reasonable (81.2%, 86.8% and 83.1% respectively). Functional outcomes were also quite favourable, with a median 15% decrease of the estimated glomerular filtration rate at discharge.

A particular finding was the relatively diverse range of histologies across resected tumours, with clear-cell renal cell carcinoma found in less than half of them (46.5%). This might reflect, in part, certain underlying genetic predispositions in these horseshoe kidneys toward the development of renal tumours. Since a significant proportion of resected tumours were benign or had a rather indolent histology, clinicians might consider performing either preoperative biopsy or additional (molecular) imaging modalities to better characterise indeterminate renal lesions and their metastatic potential.

In summary, we have shown that surgical disease management of these very rare patients can be managed with minimally invasive surgery resulting in acceptable outcomes, given the often highly complex nature of these procedures. Pre-surgical planning and utilising advanced imaging techniques such as three-dimensional reconstructions can aid in achieving good outcomes. Additionally, this work underlines the importance of international collaborative efforts to collect data and push research on rare disease entities.