Intraluminal pH in the stomach, duodenum, and proximal jejunum in normal subjects and patients with exocrine pancreatic insufficiency.

In situ pH was measured simultaneously with microelectrodes in the stomach, duodenal bulb, midduodenum, duodenojejunal junction, and proximal jejunum. Fourteen healthy subjects and 8 patients with exocrine pancreatic insufficiency were studied under fasting conditions and for 3 h after a standard liquid meal. The luminal pH gradient was steepest in the proximal 10 cm of the duodenum, where acidity was reduced from pH 2 to pH 5 in the fasting state and from pH 1.7 to pH 4.3 in the second and third postprandial hour. Acidity was further reduced in the distal duodenum to a pH between 5 and 6 at the duodenojejunal junction. The frequent wide and rapid pH fluctuations seen in the duodenal bulb were gradually reduced along the duodenum and became rare in the jejunum. In patients with pancreatic insufficiency, duodenal or jejunal acidity did not differ significantly from the controls, with the exception of the single 10-min period occurring 70-80 min after the meal when duodenal bulb pH was 2.1 as compared with 3.1 in the normal subjects (p less than 0.05). All patients, including 2 patients with a very high duodenal acidity, demonstrated a duodenal pH gradient as steep as that found in the normal subjects, indicating sources of bicarbonate other than the pancreas.