| K31 | Other diseases of stomach and duodenum | NON-BILLABLE CODE |
| K31.0 | Acute dilatation of stomach | BILLABLE CODE |
| K31.1 | Adult hypertrophic pyloric stenosis | BILLABLE CODE |
| K31.2 | Hourglass stricture and stenosis of stomach | BILLABLE CODE |
| K31.3 | Pylorospasm, not elsewhere classified | BILLABLE CODE |
| K31.4 | Gastric diverticulum | BILLABLE CODE |
| K31.5 | Obstruction of duodenum | BILLABLE CODE |
| K31.6 | Fistula of stomach and duodenum | BILLABLE CODE |
| K31.7 | Polyp of stomach and duodenum | BILLABLE CODE |
| K31.8 | Other specified diseases of stomach and duodenum | NON-BILLABLE CODE |
| K31.81 | Angiodysplasia of stomach and duodenum | NON-BILLABLE CODE |
| K31.811 | Angiodysplasia of stomach and duodenum with bleeding | BILLABLE CODE |
| K31.819 | Angiodysplasia of stomach and duodenum without bleeding | BILLABLE CODE |
| K31.82 | Dieulafoy lesion (hemorrhagic) of stomach and duodenum | BILLABLE CODE |
| K31.83 | Achlorhydria | BILLABLE CODE |
| K31.84 | Gastroparesis | BILLABLE CODE |
| K31.9 | Disease of stomach and duodenum, unspecified | BILLABLE CODE |
| K31.A | Gastric intestinal metaplasia | NON-BILLABLE CODE |
| K31.A0 | Gastric intestinal metaplasia, unspecified | BILLABLE CODE |
| K31.A1 | Gastric intestinal metaplasia without dysplasia | NON-BILLABLE CODE |
| K31.A11 | Gastric intestinal metaplasia without dysplasia, involving the antrum | BILLABLE CODE |
| K31.A12 | Gastric intestinal metaplasia without dysplasia, involving the body (corpus) | BILLABLE CODE |
| K31.A13 | Gastric intestinal metaplasia without dysplasia, involving the fundus | BILLABLE CODE |
| K31.A14 | Gastric intestinal metaplasia without dysplasia, involving the cardia | BILLABLE CODE |
| K31.A15 | Gastric intestinal metaplasia without dysplasia, involving multiple sites | BILLABLE CODE |
| K31.A19 | Gastric intestinal metaplasia without dysplasia, unspecified site | BILLABLE CODE |
| K31.A2 | Gastric intestinal metaplasia with dysplasia | NON-BILLABLE CODE |
| K31.A21 | Gastric intestinal metaplasia with low grade dysplasia | BILLABLE CODE |
| K31.A22 | Gastric intestinal metaplasia with high grade dysplasia | BILLABLE CODE |
| K31.A29 | Gastric intestinal metaplasia with dysplasia, unspecified | BILLABLE CODE |
