In general, diseases of the stomach and duodenum can be subdivided as follows. a) Functional disorders. b) Gastritis. c) Ulcer of the stomach and duodenum. d) Cancer. e) Rare lesions. f) Pathological changes in the stomach as secondary concomitant phenomena in general diseases. 

It should be noted here that a long period of time elapses between the occurrence of complaints and the establishment of the diagnosis of stomach cancer , on average equal to 8 months. This partly explains the still very unsatisfactory results of surgical treatment, since the prognosis for this disease depends almost entirely on the time when it was recognized.  

Differential diagnosis is possible when using, firstly, anamnestic data, secondly, local examination data and, thirdly, radiological data. 

Anamnesis . Opinions differ on the differential diagnostic value of anamnesis. According to the experience of old clinicians, anamnesis is everything for the differential diagnosis of stomach diseases, objective data is nothing. Although this statement can no longer be so categorical, nevertheless, special attention should be paid to careful collection of anamnesis for stomach diseases. Here it is undoubtedly much more important than in many other diseases.

With functional lesions of the stomach, complaints are not sufficiently definite. They are irregular in the time of their appearance, non-periodic, do not depend on the time of the meal. 

Acute gastritis , in which it is usually possible to identify a connection with the effect of an accepted damaging agent, hardly presents differential diagnostic difficulties. In the clinical picture of the disease, a feeling of diffuse pressure in the stomach area prevails, which can reach the degree of intense pain. Complaints are worse after eating. Most of the vomiting is followed by relief. Within a few hours or days, complaints subside. Often gastric symptoms are accompanied by intestinal symptoms (flatulence, diarrhea). Chronic gastritis can be divided into two forms:
a) hypertrophic,
b) atrophic hyperplastic.

The first of them reveals a close relationship with peptic ulcer disease , the second with stomach cancer. The history of hypertrophic gastritis, identified by some authors with a pathologically irritable stomach, does not differ significantly from the history of a patient with peptic ulcer disease. Accordingly, there is a more distinct periodicity of complaints, their seasonality with an increase in symptoms in spring and autumn and, depending on localization, early or late hunger pains. At the same time, hungry pains are of particular importance in the diagnosis of duodenitis or duodenal ulcers. Pain in the upper abdomen regularly occurring at 11 am and 5 pm, even in the absence of characteristic clinical data, should be regarded with a high probability as a symptom of duodenitis proceeding with or without a duodenal ulcer. Unlike ulcers, with gastritis, prolonged pain prevails – within a day, and early or late pains can be layered on them. 

Eating can aggravate complaints and chronic gastritis (feeling full, pressure, discomfort). Local phenomena can be accompanied by loss of appetite and general symptoms (deterioration of the general condition). 

An ulcer is extremely painful, strictly localized in an area equal to the circumference of the fingertip, while gastritis pain is usually diffuse in nature. This precisely delineated pain point in stomach ulcers is mostly determined along the midline or somewhat to the left, less often to the right of it, while in duodenal ulcers, pain is generally noted on the right, under the edge of the costal arch. Although the pain returns to the left or right half of the abdomen, although it happens, it is not very typical, and irradiation to the shoulder, one might say, is not observed (an important distinguishing feature from lesions of the gallbladder!). Pain with a duodenal ulcer radiates to the right, with a stomach ulcer – more often to the left. For perforated ulcers, especially when perforating into the pancreas, piercing, prolonged pain in the back is typical. 

The nature of the pain makes it possible to establish important differential diagnostic differences from hepatic colic. Ulcer pain rarely begins completely suddenly. They reach their maximum intensity within 5-15 minutes or even slower, while with gallstone disease, pain often reaches its peak within 2-3 minutes. Unlike gallstone disease, ulcer pain also subsides more slowly. Based on the intensity of pain, differential diagnostic conclusions are hardly possible, although, as a rule, with gallstone disease, pain is more intense than with peptic ulcer. The immediate cause of pain with an ulcer usually cannot be established accurately, while with gallstone disease, as well as with gastritis, there is usually a close temporary connection with the intake of very fatty, difficult to digest food. 

Pain in peptic ulcer disease is almost never accompanied by nausea, while it is very often accompanied by diseases of the gallbladder. Of particular importance for distinguishing between both diseases is the duration of individual painful periods: an attack of gallstone disease lasts 1-3 days, exacerbation of peptic ulcer disease – 3-5 weeks. After eating, ulcerative pain usually disappears after a few minutes, this does not happen with pain caused by gallstone disease! 

Appetite , unlike gastritis and stomach cancer, is not impaired in peptic ulcer disease. If, despite the presence of other symptoms of an ulcer, pain is not typical, you should think about possible complications: constant pain during perforation, nausea and vomiting with a feeling of pressure in the stomach – with stenosis.