In this prospective, non-randomized cohort study, real-time intraoperative visualization using near-infrared-fluorescence by indocyanine green injection (ICG-NIRF) is performed at three time points during ileal pouch reconstruction. Postoperatively, a detailed software-based assessment of each pouch recording is performed to determine the objective ICG-NIRF perfusion rate, which is then correlated with the 30 day postoperative clinical outcome including occurrence of anastomotic leak of the pouch.

Near-infrared-fluorescence by indocyanine green (ICG-NIRF) utilises the fluorescent property of intravenously injected indocyanine green (ICG) as an intravascular indicator of tissue and bowel perfusion.

The investigators hypothesise that ICG-NIRF is a suitable, reliable and precise method of visualisation of the blood supply and bowel perfusion in the area of ileal pouch formation and the ileal pouch-anal anastomosis.

In this prospective, non-randomized cohort study, restorative proctocolectomy with ileal pouch reconstruction and ileal pouch-anal anastomosis is performed according to standard of care for medically-refractory ulcerative colitis (UC), UC-associated neoplasia, medically-refractory Crohn´s colitis, colorectal carcinoma or familial adenomatous polyposis (FAP) in open or laparoscopic surgery, according to the surgeon's choice.

Written informed consent for participation and ICG-administration is obtained one day before surgery.

Intraoperatively, Indocyanine Green (ICG, VerDye, Diagnostic Green GmbH, Aschheim Germany, 25 mg vials) is dissolved in 5 mL sterile water to yield a 5 mg/mL concentration. It will then be administered intravenously at three consecutive time points as a bolus of 2 ml per time point at the most. The overall dose of ICG will amount to no more than 30mg of ICG per patient.

Real-time intraoperative visualization is performed with the SpectrumTM Fluorescence Imaging Platform (Quest Innovations, Middenmeer, The Netherlands) directly after each ICG injection assessing bowel perfusion at three different time points respectively: before and after J-Pouch construction by stapler anastomosis and after ileoanal anastomosis formation.

Postoperative NIRF-perfusion rate assessment Using the Quest Research SoftwareTM, the recordings before and after anastomosis formation will be analysed for their perfusion rate. This analysis will provide objective, quantitative data on the perfusion for a certain time frame which is determined by the length of the video recording. This data will be collected for statistical analysis and correlation with anastomotic leak as well as postoperative outcome.

Clinical data and follow-up Clinical data will be collected from all patients regarding anastomotic leak, bowel ischemia and necrosis as well as 30 day postoperative morbidity, mortality and length and cost of hospital stay.

Further data analysis will be performed using Microsoft Excel® and IBM SPSS®.

Inclusion Criteria:

• age ≥ 18
• capability of signing the informed consent
• diagnosis of therapy resistent ulcerative colitis, colorectal cancer, Crohn's disease, familial adenomatous polyposis
• restorative proctocolectomy (RPC) with reconstruction through ileal pouch formation and ileal pouch-anal anastomosis (IPAA) is possible and medically indicated
• ASA (American Society of Anesthesiologists) Physical Status Classification System score ≤ 3

Exclusion Criteria:

• coexistent malignant tumor of a different ethology
• liver disfunction (MELD score > 10)
• ICG (indocyanine green) specific exclusion criteria as per literature (intolerance to indocyanine green or sodium iodide, iodine allergy, hyperthyroidism, autonomous thyroid adenoma, focal or diffuse autonomies of the thyroid, previously badly tolerated injection of ICG)
• pregnancy or breastfeeding

this will be determinable at a later point when more data is available