Dumon K, Dempsey DT. (2019). Postgastrectomy Syndromes. Shackelford’s Surgery of the Alimentary Tract, 8th ed.: 719-734.

“Hypergastrinemia after distal gastrectomy can be caused by gastrinoma or retained antrum. In the latter there is residual antral tissue left in continuity with the duodenal stump after gastric resection with Billroth II anastomosis. The G cells in this retained antral tissue are not exposed to luminal acid, resulting in continuous secretion of gastrin and intense stimulation of acid production by parietal cells in the proximal gastric remnant. The exposure of the unbuffered jejunum to this high acid level at the Billroth II GJ results in marginal ulcer (see Fig. 62.12B ).