PMC9296266_01
High resolution perineal ultrasound images: position of the linear transducer with PIUR tUS Infinity System add on mediansagittal at the center of the perineal body, patient supine held in lithotomy position, foley cathter in the mucous fistula. (
A
); recto-bulbar fistula (
B
); recto-prostatic fistula (
C
).
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Toshiba 14L5) with the PIUR tUS Infinity system add-on (Piur Imaging GmbH Vienna, Austria) was positioned on the perineum ( Fig. 1A ). After documentation of the anatomy in B-mode (including video loops), the add-on scan was performed by parallel probe sliding from left-to-right in a single acquisition (with video documentation). The distinction between recto-bulbar (two cases) and recto-prostatic fistulas (two cases) was possible by direct identification of the fistula relative to the rectum and the urethra, as well as indirect visualization of the prostate ( Fig. 1B , C ). 
3D reconstruction process: on the left side respectively two coronal (
A, B
) and two sagittal cuts (
C, D
) created from the ultrasound acquisition, which are used to automatically reconstruct the structure, shown on the right side (
E
).
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 The 3D tomographic reconstruction was then automatically generated by the PIUR tUS Infinity system through threshold-based automatic segmentation of the images ( Fig. 2 ).
Comparison between distal colostogram (
A, C
) and the automatically 3D reconstructed structures, including bladder, urethra, and recto-urethral fistula, acquired from the linear ultrasound imaging (
B, D
) from the same patient.
A
and
B
show a recto-bulbar fistula,
C
and
D
a recto-prostatic fistula. The star indicates the rectum, the diamond shape of the bladder, and the arrow points to the recto-urethral fistula.
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 In all cases the results of the distal colostogram nicely correlated with the high-resolution transperineal US by B-mode and tUS ( Fig. 3A - D ).