Patient description: The patient is a 55-year-old man diagnosed with HCV 2 years ago and the recent coinfection with HBV. His past medical history is non-significant. He is on IFN, RBV and direct antiviral drugs for the past 6 months. The patient takes no other medications. His medical records show previous positive HCV RNA tests and a positive enzyme immunoassay for anti-HCV-antibodies. The recent biopsy was negative for hepatocellular carcinoma and was only remarkable for chronic inflammation compatible with a chronic viral hepatitis. There is no evidence of alcoholic liver disease, bleeding from esophageal varices, hemochromatosis, autoimmune hepatitis, or metabolic liver disease. He is an alert male with no acute distress. His BP: 130/75, HR: 90/min and BMI: 27. His abdomen is soft with no ascites or tenderness. The lower extremities are normal with no edema.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Constipation I 01. Adult subjects that self-medicate with occasional laxative no more than 4 times in the month before confirmation I 02. Meet Rome IV for Chronic Constipation. I 03. ≥18 years of age inclusive, at the time of signing the informed consent. I 04. Screening diary confirms they experience at least 2 days in the 7 day diary with either hard stools (Bristol Stool form Score 1 or 2) or no bowel movement I 05. BMI under or equal to 35 kg/m2 I 06. Female subjects of child bearing potential must have a negative urine pregnancy test at screening. Subjects of child bearing potential or with partners of child bearing potential must agree to use methods of medically acceptable forms of contraception during the study and for 90 days after completion of study drug, (e.g. implants, injectable, combined oral contraceptives, barrier methods, true abstinence (when this is in line with the preferred and usual lifestyle of the patient) or vasectomised partners). I 07. Capable of giving signed informed consent as described in Appendix 1 (Section 10.1) which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in this protocol  E 01. Known hypersensitivity or other contraindications to bisacodyl use: such as ileus, intestinal obstruction, acute abdominal conditions including appendicitis, acute inflammatory bowel diseases, and severe abdominal pain associated with nausea and vomiting; and severe dehydration or rare hereditary conditions that may be incompatible with an excipient of the product (galactose intolerance, e.g. galactosaemia, fructose intolerance. E 02. Pregnancy and/or breast breast-feeding or positive urine pregnancy test History of known gastrointestinal organic disease (i.e. celiac disease, inflammatory bowel diseases). E 03. A positive diagnosis of irritable bowel syndrome based on the Rome IV questionnaire which requires the patient to experience abdominal pain at least weekly E 04. Reported history of previous major abdominal surgery (excluding appendectomy and cholecystectomy) E 05. Any medical condition making participation potentially compromising the participation in the study (e.g. diabetes mellitus, respiratory disease limiting ability to lie in the scanner, known allergy to one of the food products) as per investigator's judgment E 06. Contraindications for MRI scanning i.e. metallic implants, pacemakers, history of metallic foreign body in eye(s) and penetrating eye injury E 07. Any condition incompatible with the patient's participation to the study as per investigator's judgment. E 08. Not willing or able agree to dietary restrictions required in 24 hours before each MRI study day E 09. Anticipate need for antibiotics intake during the study. E 10. Unwilling to stop probiotics for the duration of the study period E 11. Unable/ not willing to stop drugs known to alter GI motility including, regular loperamide, antispasmodics, (e.g. buscopan, mebeverine, peppermint oil, alverine citrate), eluxadoline opiates, monoamine oxidase inhibitors, phenothiazines, benzodiazepines, calcium channel antagonists for the duration of the study (Selective serotonin reuptake inhibitors and low dose tricyclic antidepressants (< 30mg amitriptyline or 50mg nortriptyline) will be recorded but provided dose is stable, will not be an ). E 12. Having taken part in a research study within 3 months