The project presented here is a monocentric clinical study conducted by the Pediatric Surgery and Pediatrics departments of the University Hospital Erlangen. The study aims to experimentally expand the diagnostic approach for patients aged 0-17 years suffering from chronic bowel emptying disorders, regardless of any underlying causal or previously treated conditions. At the core of this clinical study is the application of Multispectral Optoacoustic Tomography (MSOT) in combination with the oral contrast agent Indocyanine Green (ICG) to measure gastrointestinal transit time in children. Unlike conventional X-ray diagnostics, MSOT is radiation-free and considered non-invasive, although it has not yet been standardized for routine clinical use. Additionally, a contrast-free, non-invasive MRI technique will be employed to assess the peristalsis of intestinal segments. The study aims to standardize the collection and evaluation of patient data following the administration of ICG and subsequent measurements using MSOT and MRI. The objective is to assess gastrointestinal transit time and peristalsis and, ultimately, to optimize therapy for affected patients. This is of particular importance in the coloproctology specialist consultation within the Pediatric Surgery and Pediatrics departments, as follows: It enables differentiation between patients with slow transit constipation and outlet obstruction. It allows for a more targeted application and evaluation of neuromodulation therapy, which is used within clinical studies. This approach allows for the identification of specific intestinal segments with delayed transit time, enabling targeted electrical stimulation of these regions. A control group of healthy adult volunteers will participate in the study on a voluntary basis.