Validation of a 3D-printed model of cryptoglandular perianal fistulas.

INTRODUCTION: Visualising the course of a complex perianal fistula on imaging can be difficult. It has been postulated that three-dimensional (3D) models of perianal fistulas improve understanding of the perianal pathology, contribute to surgical decision-making and might even improve future outcomes of surgical treatment. The aim of the current study is to investigate the accuracy of 3D-printed models of perianal fistulas compared with magnetic resonance imaging (MRI). METHODS: MRI scans of 15 patients with transsphincteric and intersphincteric fistulas were selected and then assessed by an experienced abdominal and colorectal radiologist. A standardised method of creating a 3D-printed anatomical model of cryptoglandular perianal fistula was developed by a technical medical physicist and a surgeon in training with special interest in 3D printing. Manual segmentation of the fistula and external sphincter was performed by a trained technical medical physicist. The anatomical models were 3D printed in a 1:1 ratio and assessed by two colorectal surgeons. The 3D-printed models were then scanned with a 3D scanner. Volume of the 3D-printed model was compared with manual segmentation. Inter-rater reliability statistics were calculated for consistency between the radiologist who assessed the MRI scans and the surgeons who assessed the 3D-printed models. The assessment of the MRI was considered the 'gold standard'. Agreement between the two surgeons who assessed the 3D printed models was also determined. RESULTS: Consistency between the radiologist and the surgeons was almost perfect for classification (κ = 0.87, κ = 0.87), substantial for complexity (κ = 0.73, κ = 0.74) and location of the internal orifice (κ = 0.73, κ = 0.73) and moderate for the percentage of involved external anal sphincter in transsphincteric fistulas (ICC 0.63, ICC 0.52). Agreement between the two surgeons was substantial for classification (κ = 0.73), complexity (κ = 0.74), location of the internal orifice (κ = 0.75) and percentage of involved external anal sphincter in transsphincteric fistulas (ICC 0.77). CONCLUSIONS: Our 3D-printed anatomical models of perianal fistulas are an accurate reflection of the MRI. Further research is needed to determine the added value of 3D-printed anatomical models in preoperative planning and education.

A woman with a solitary pulmonary nodule: is it a lung cancer?

BACKGROUND: Solitary pulmonary nodules present a real challenge for physicians. Due to the clinical implications and prognosis of a certain diagnosis, it should be pursued with any cost; a clear definition is not always simple and further investigations are often necessary to exclude the possibility of a malignancy. A diagnostic path must be followed and the clinical hypothesis should be reconsidered on the basis of the new information provided by the tests, always keeping in mind their limits! Sometimes only the surgical resection permits a definitive diagnosis. A 68 year-old non-smoker female with a pulmonary solitary nodule highly suspicious to be malignant at the chest CT, performed a FBS with BAL, negative for neoplastic cells and for infective agents, and a CT guided pulmonary biopsy that was inconclusive. The patient underwent then a video-thoracoscopic atypical lung resection that demonstrated the reactive nature of the lesion, definitely excluding the presence of a malignancy.