Peter van Mourik

170 Chapter 8 or lumacaftor/ivacaftor, resulting in about 80 in vitro responders in the observed population of 500 subjects, which covers about 27 subjects for each of the three intended clinical trials. Study procedures The study procedure performed is collection of rectal biopsies by either forceps during sigmoidoscopy or using a rectal suction device. These are not part of regular medical treatment. Each site has the possibility to choose the procedure they are most experienced in. The success rate of generating organoids out of two forceps biopsies is >92%. Success rates for rectal suction device is >95% if four biopsies are obtained, and ~80% if two biopsies are obtained (unpublished data from UMCU/ HUB). Therefore, either two forceps or four rectal suction biopsies will be obtained per subject. If no organoids can be generated, the patient will be re-contacted and asked whether they are willing to undergo another biopsy. The biopsies will have no influence on regular medical care. If intestinal organoids have already been generated for a subject in a previous study or for routine medical care and can be made available for testing, subjects do not need to undergo the study procedure again. Rectal suction biopsy Biopsies can be collected using a rectal suction device. This device is used to facilitate diagnosis of the disease Morbus Hirschsprung, and to obtain material for Intestinal Current Measurement for the diagnosis of Cystic Fibrosis. Therefore, many CF-centres have experience with rectal suction biopsies. A working instruction is provided to the sites with detailed instructions how to perform the procedure. To obtain the best possible biopsies, patients will be treated with an enema (sodiumphosphate), to clean the most distal part of the colon. If this is contraindicated, biopsies will be collected without a preceding enema. During the procedure, patients will lie on their side, with knees pulled upwards towards the chest. Next, the rectal suction device is introduced rectally, and inserted ~6 cm. The rectal suction device is connected by a rubber tube to a vacuum meter, and the vacuum meter is attached by a rubber tube to a 50cc plastic syringe. The assisting nurse sucks air into the suction device by pulling on the plunger of the syringe. This creates a vacuum, and intestinal tissue is sucked into the suction device through an opening with a diameter of 2.0 millimeter. This tissue is subsequently cut by the rectal suction device, and the tissue is collected. The diameter of the collected tissue is around 2 mm, and less than 1 mm thick. The biopsies are taken on the dorsolateral sides of the rectum, because no pain receptors are present there and no major blood vessels