The present invention relates to an improved apparatus and method for instilling fluid into a patient having an intestinal stoma thereby administering an antegrade colonic enema. The portable instillation apparatus comprising in combination: a fluid reservoir, a pump assembly, a control module, a fluid delivery line and an intestinal stoma catheter wherein the control module is operable to automatically stop fluid delivery to the intestinal stoma after a predetermined volume of fluid has been instilled at a predetermined flow rate and pressure range suitable for a particular patient. The portable instillation apparatus incorporates a unique gear pump manifold facilitating the portability, durability and reliability of the apparatus overcoming the disadvantages of traditional peristaltic pump mechanisms. The portable instillation apparatus is so engineered as to maximize the ease of transport and use of the device while also enabling a method for a patient to self-administer an antegrade colonic enema within a short time period and without intervention.