Background and aim: Clinicians encounter difficulties distinguishing enterocutaneous fistulae from postoperative suture abscesses solely by diagnostic imaging in patients with Crohn's disease. The aim of this study was to examine whether use of intraintestinal administration of indocyanine green (ICG) could differentiate the conditions.
Methods: Twenty-four patients with Crohn's disease and a possible enterocutaneous fistula at the abdominal wall based on manifestations of pus drainage and exudate were enrolled. A positive test was defined by macroscopic confirmation of staining by ICG dye, which had been administered orally, on the gauze dressing applied to the lesion site.
Results: Positive responses occurred in 16 of the 24 patients. In 13 of the 16 positive patients, a fistulous communication between the lesion and the gastrointestinal tract was documented by either surgery or X-ray examination. In the remaining three, fistulae were completely closed after administration of infliximab. The positive predictive value of the oral ICG test was 16/16 (100%). Six of the eight negative oral ICG test patients (75%) had subcutaneous (silk-suture) abscesses that were easily closed following fistulotomy. The other two patients had fistulas confirmed either by surgery or fistulography, indicating a false negative response from the oral ICG test. The negative predictive value of the oral ICG test was 6/8 (75%); thus, the ability of the oral ICG test to correctly diagnose was 22/24 (92%).
Conclusions: This oral ICG test offers a suitable methodology for those patients possessing an occult fistulous lesion at an early stage, and where a differential diagnosis is difficult using diagnostic imaging.