It is well known that enterocystoplasty within terminal ileum leads to vitamin B12 deficiency and regular monitoring of this post-surgery is essential. Often supplements need to be given because of deficiency in up to 40% of patients. These authors looked at the long-term efficiency of giving B12 supplementation at a single institution with experience of over 898 patients on their database (not all children). Patients with non-ileal augment, insufficient follow-up or haematologic disorders were excluded. Patients with low or low-normal B12 levels were included. Patients had B12 supplements started if necessary after deficiency screening five years post-surgery. Treatment consisted of either daily oral therapy of 250mcg or monthly parenteral therapy 1000mcg IM and successful treatment was defined as persistent normalisation of serum B12 levels after beginning supplementation. Twenty-three out of thirty children were included (six excluded because of insufficient follow-up and one because of other haematological factors). They had a mean follow-up of 49 months (range 5-85). Sixteen required supplementation (14 oral and two IM). Of the 14 with oral supplements, six had normalisation at some point but only four had sustained normalisation. Of the 23 patients included in the analysis, none were diagnosed with megaloblastic anemia. One patient had an elevated MCV with a low-normal B12, which persisted despite treatment and normalisation of serum B12 level. No patient suffered any neurologic or haematologic sequelae of serum B12 deficiency as of the last follow-up. The authors conclude that oral supplementation with B12 does not lead to a sustained normalisation of B12 and that this may be due to reduced compliance with vitamin therapy.