Low pH in the small intestine

Introduction The intestinal fluid is secreted by the small intestine glands in the small intestine mucosa. It is weakly alkaline. The daily secretion of adults is about 1 to 3L. The intestinal fluid is absorbed while secreting, and the exchange of this liquid provides a medium for the absorption of nutrients in the small intestine. In addition to water and electrolytes, the intestinal fluid contains mucus, immune proteins and two enzymes: enterokinase and small intestinal amylase. In the past, it was thought that the intestinal fluid also contained various other digestive enzymes, but it has been proved that other various digestive enzymes are not secretions of the small intestine gland, but exist in the intestinal epithelial cells of the small intestine. They are several peptidases that break down polypeptides into amino acids and several monosaccharases that break down disaccharides into monosaccharides. These nutrients continue to digest nutrients as they are absorbed into the epithelial cells. As the epithelial cells at the top of the villi fall off, these digestive enzymes enter the intestinal fluid.

Cause

The low pH in the small intestine makes certain primary bile acids insoluble and lipid micelle formation reduced, while the latter is necessary for the absorption of fatty acids and monoglycerides. Gastrinoma patients may have malabsorption of vitamin B12, which is not related to internal factors. Although the function of gastric secretion is normal, the low pH in the small intestine affects the function of internal factors to promote the absorption of vitamin B12 in the distal jejunum. This function is restored when the pH is adjusted to 7. Low pH in the small intestine is common in gastrinoma.

an examination

Related inspection

Gastric acid pH (pH) Determination of pH (pH)

The clinical manifestations of gastrinoma, especially primary gastrinoma, are indistinguishable from common ulcers, but there are some clinical conditions that can highly suggest the diagnosis of gastrinoma: the distal segment of the duodenum; Multiple ulcers of the digestive tract; usually ulcer treatment is ineffective; rapid recurrence after ulcer surgery; patients with peptic ulcer and diarrhea or diarrhea that is difficult to explain; patients with a typical family history of peptic ulcer; patients with parathyroid or pituitary tumors History or related family history; patients with peptic ulcer with urinary calculi; Helicobacter pylori-negative peptic ulcer without a history of non-steroidal anti-inflammatory drugs; with high gastric acid secretion or high gastrinemia or both .

Laboratory inspection:

1. Determination of gastric acid secretion:

Most (79%) patients with gastrinoma have a basal gastric acid secretion rate of >15 mmol/h and can be as high as 150 mmol/h. Some people think that comparing the amount of basal gastric acid secretion and the amount of gastric acid secretion after maximal stimulation is useful for the diagnosis of gastrinoma, but patients with common ulcers and even some normal people sometimes have high rate of acid secretion, and 1/2 to 2/3 of gastric secretion. The basal acid secretion of patients with tumors is also less than 60% of the maximum acid secretion, so its value is still questionable. At present, many medical institutions no longer use this technology, and some other diagnostic methods have basically replaced this test.

2. Gastrin determination:

The most sensitive and specific method of detecting gastrinoma is to determine serum gastrin concentration. In normal ulcers and normal subjects, the average fasting serum gastrin level is 50-60pg/ml (or less), the high limit is 100-150pg/ml, and the fasting serum gastrin level in gastrinoma patients is often >150pg. /ml, the average level is close to 1000pg/ml, sometimes as high as 450,000 pg/ml. In patients with clinical symptoms of peptic ulcer and high gastric acid secretion, when the concentration of fasting serum gastrin is significantly increased (>1000pg/ml), the diagnosis of gastrinoma can be established. It has been reported that patients with gastrinoma should be highly suspected to be metastatic gastrinoma when the fasting serum gastrin level is >1500pg/ml. If you have a history of hypergastrinemia or urinary calculi, unexplained diarrhea, multiple ulcers, or suspected gastrinoma in patients with distal duodenal or jejunal ulcers, they should be tested. Serum gastrin levels; this test should also be performed in patients with a family history of endocrine disease, especially multiple type I endocrine neoplasia, recurrent ulcer after surgery, and improved symptoms of drug-treated ulcers. It should be noted that some diseases that cause a decrease in gastric acid secretion can also cause an increase in serum gastrin, such as pernicious anemia. Patients with pernicious anemia are comparable to serum gastrin in patients with gastrinomas, but the pH of gastric contents in patients with pernicious anemia is not less than 6 even under maximum stimulation. Infusion of 0.1 mmol/L hydrochloric acid in patients with pernicious anemia can reduce serum gastrin levels to approximately normal, which helps to differentiate from gastrinoma.

Differential diagnosis

Differential diagnosis of low pH in the small intestine:

1. Peptic ulcer: Peptic ulcer is more common in a single ulcer or in the stomach and duodenum (complex ulcer), and multiple ulcers in the stomach or duodenum are relatively rare. Gastrinoma should be highly suspected if:

(1) Duodenal ampullary ulcer.

(2) Peptic ulcer is still ineffective after conventional doses of antisecretory drugs and regular course of treatment.

(3) ulcers rapidly relapse after surgical treatment of ulcers.

(4) Unexplained diarrhea.

(5) Personal or family history of parathyroid or pituitary tumors.

(6) Significantly high gastric acid secretion and hypergastrinemia.

2. Gastric cancer: The similarity between this disease and gastrinoma is poor medical treatment and intra-abdominal metastasis, but gastric cancer rarely combined with duodenal ulcer, no high gastric acid and high gastrin secretion characteristics, gastroscopic biopsy pathology Histological examination has a differential diagnostic value.

The clinical manifestations of gastrinoma, especially primary gastrinoma, are indistinguishable from common ulcers, but there are some clinical conditions that can highly suggest the diagnosis of gastrinoma: the distal segment of the duodenum; Multiple ulcers of the digestive tract; usually ulcer treatment is ineffective; rapid recurrence after ulcer surgery; patients with peptic ulcer and diarrhea or diarrhea that is difficult to explain; patients with a typical family history of peptic ulcer; patients with parathyroid or pituitary tumors History or related family history; patients with peptic ulcer with urinary calculi; Helicobacter pylori-negative peptic ulcer without a history of non-steroidal anti-inflammatory drugs; with high gastric acid secretion or high gastrinemia or both .

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