An unusually large gastric pouch (such as horizontal pouches, retained fundus, long lesser curvature based pouches or enlarged after initially being sized adequately) contain more acid-producing parietal cells. Increased acid production in the pouch carries the risk of developing marginal ulcers. Acid secretion in the small pouch after RYGB is virtually absent. Smith et al measured basal and pentagastrin-stimulated gastric acid secretion from the pouch were significantly lower compared to age and sex-matched controls. Likewise, MacLean et al reported a significantly lower pH & greater time with pH <2 in the gastric pouches of marginal ulcers and/or GGF patients after RYGB compared to non-complicated RYGB controls. Thus, creating a esophagojejunostomy would solve the gastric acid factor for developing marginal ulcers however the high incidence of anastomotic failure and unknown weight loss results are prohibitive for this approach. Sapala et al created a micro-pouch or cardiojejunostomy to decrease at maximum the parietal cell mass with a low incidence of marginal ulcers (0.01% at 1 years of follow-up) as well as to limit the pouch dilation. By Histopathology with a semi-quantitative approach, Gustavsson et al reported less acid-producing parietal cells within smaller pouches. With his next study (n=12), Gustavsson et al, demonstrated a significantly higher time exposure to a pH<4 in patients with marginal ulcer after RYGB (4x3cm pouch) compared to controls (p< 0.01). Furthermore, after downsizing the pouch, repeated pH-metry showed the % of time with pH <4 declined from 100% prior to 6% after revisionary surgery.