ABSTRACT - 593657 The disclosure relates to a liquid enema preparation suitable for administration intra-colonically which comprises a photosensitiser which is a 5-aminolevulinic acid (5-ALA) ester, or a pharmaceutically acceptable salt thereof, and at least one pharmaceutically acceptable carrier or excipient and which further comprises: (a) one or more viscosity enhancing agents； and optionally one or more of the following: (b) one or more mucoadhesive agents or one or more mucolytic agents； (c) one or more penetration enhancers； and (d) one or more chelating agents； wherein the viscosity of the preparation increases after instillation into the area of interest. This enema preparation is suitable for the photodynamic treatment or diagnosis of cancer or non-cancerous conditions in the lower part of the gastrointestinal tract selected from inflammatory bowel disease, ulcerative colitis, Crohn's disease and irritable bowel syndrome
