Chapter 2 (page 3)

The Pyloric Sphincteric Cylinder in Health and Disease

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Chapter 2 (page 3)

Chapter 2

Some Uncertain Concepts

1. The Pyloric Antrum

Willis (l682) introduced the term "antrum pylori" (Greek antron = cave) to indicate the part of the stomach adjoining the pylorus; no further demarcation was given. Cunningham (1906) pointed out that the term was ambiguous and that it was rarely possible to obtain a clear anatomical conception of what it meant; it was largely responsible for much of the obscurity associated with the pyloric part of the stomach. Lewis (1912) also drew attention to the confusion caused by the term.

Forssell (1913) was totally opposed to the designation "antrum," as, in his view, it was vague and had no foundation in anatomical fact. Müller (l921) pointed out that the word was used in different senses; some authors used it to denote a small area close to the pylorus while others considered it to be the entire "transverse" stomach.

Cole et al. (l932) defined "antrum" as the portion of the stomach between the sulcus angularis and the pyloric valve; the fan-shaped muscle constituted a small portion of its distal end (Fig. 3.4). Golden (l937), on the other hand, used the term as a synonym for Forssell's canalis egestorius (i.e., the fan-shaped muscle) (Fig. 3.3).

While discussing a series of cases of gastric carcinoma, Coller et al. (l941) stated that in the majority the lesion was located either in the prepyloric region or in the pyloric antrum, from which it is concluded that these are different entities. In view of the ambiguities and lack of anatomical definition, Torgersen (l942) advocated abolition of the term "antrum."

Clarity is not forthcoming from the descriptions of Jenkinson (l955), who stated that the pyloric canal, approximately 3.0 cm in length, was located on the oral side of the "pyloric sphincter"; the antrum was said to be the region extending from the pyloric canal to the incisura angularis on the lesser curvature (Fig. 2.1). In another sentence the antrum was defined as the part of the stomach between the sulcus intermedius and the duodenum.

Fig. 2.1. Pyloric antrum according to Jenkinson. P.S., pyloric sphincter; P.C., pyloric canal; S.I., sulcus intermedius; I.A., incisura angularis. (In another sentence the antrum was said to be the region between the sulcus intermedius and the duodenum.)

Not only do anatomists disagree among themselves about the concept "antrum", but Foulk et al (l957) pointed out that gastric landmarks and boundaries differed in their details for the pathologist, the surgeon, the endoscopist and the radiologist. Grossman (l958) stated that many writers had commented on the lack of uniformity of terms and the ambiguity of some of them; according to him the pyloric portion was usually divided into the pyloric canal adjacent to the sphincter, and the pyloric vestibule or antrum adjacent to the corpus. He preferred to name functional divisions of the stomach in terms of their secretory characteristics; "pyloric gland area" was suggested for the mucus secreting, gastrin producing zone and "oxyntic gland area" for the acid producing region.

According to Edwards (l96l) it was widely accepted that the antrum represented the portion of the stomach distal to the incisura, which approximately defined the boundaries of the pyloric mucosal zone. Although some anatomists and clinicians adhered to this definition, du Plessis (l963), as a surgeon, was concerned with the fact that the pyloric mucosal zone was often larger than the anatomical antrum. Tanner (l964) pointed out that there was extreme variability in the extent of antral mucosa; if it were equated with the antrum, the boundaries of the latter would also be variable.

Moe et al. (l965) looked upon "antrum" as the pyloric mucosal zone. According to Capper et al (l966) the antrum was more of a physiologic concept than an anatomical one, and was best defined as the distal part of the stomach which contained and released gastrin; for antrectomy to be adequate, this zone had to be defined accurately and all of the gastrin-secreting mucosa had to be removed.

Carlson et al. (l966) and Code and Carlson (l968) defined the antrum as the region caudad to the incisura angularis. In terms of motor function it was divided into two segments of varying length (Fig. 2.2). The more caudad portion, called the terminal segment, participated in a simultaneous, segmental contraction called terminal antral contraction (TAC); the length of the segment was not fixed and its dimensions might change. The cephalad segment of the antrum was not involved in TAC but the two segments constituted a functional motor unit and contracted in a coordinated way.

Edwards and Rowlands (l968) again drew attention to the confusion in nomenclature; in their view the term "antrum" denoted the proximal part of the thickened muscle mass adjacent to the pylorus, and not the part of the stomach distal to the incisura angularis.

Fig. 2.2. Pyloric antrum according to Carlson et al. I.A., incisura angularis; T.A., terminal antrum