Anatomical classification of the shape and topography of the stomach

The currently presented classification seems to be the first that clearly and completely describes anatomical positions of the stomach. Similar classifications were not available in the world literature.

Among all the examined patients with anatomical variances of the stomach, the most common position was the hiatal hernia (about 60–75% depends of the year). However, such high incidence cannot be regarded as typical for the Polish and even local population, while the study was performed in the University Hospital with a Surgical Department that is highly specialized in the esophageal and stomach surgery and is referential for the south-east part of Poland. Moreover, some patients were admitted to the hospital with previous, well-documented diagnosis and additional radiological examinations were not performed.

Since the first description in 1926 [2], confirmed by later studies, translocations of the stomach along its long axis is divided into sliding, paraesophageal and mixed-form hiatal diaphragmatic hernia, as well as a congenital short esophagus.

The sliding hiatal diaphragmatic hernia is the most common type seen on the level of esophageal hiatus and is characterized by the direct dislocation of the stomach cardia into the posterior mediastinum. Such anomaly is observed in 80–90% of the abnormal translocations of the stomach through this foramen [23]. Epidemiological data suggest a strong geographical and socioeconomic-dependent distribution of the disease. Its highest prevalence was observed in well-economically developed communities of the North America and the Europe, where the incidence reaches 15–20% of the adults. It increases with age, from 10% in patients younger than 40 years to 70% in those older than 70 years [41, 47]. However, much lower incidence (0.3%) was presently found among 637,518 Americans by Hauer-Jensen et al. [21]. Contrary to those data, the disease is extremely rare in rural African communities. Such abnormal stomach position was revealed in four out of 1,030 examined Nigerians [4], one of 1,000 Kenyans [44] and one of 700 Tanzanians [19]. A low incidence was also reported throughout India, the Middle East and East Asia [9]. A strong environmental influence, with no or low genetic predisposition was proved by observation of the same incidence of the sliding hiatal hernia in Afro-Americans and Caucasian Americans [9]. It was also noted in two different Korean studies taken at a 35-year interval, characterized by extremely high positive socioeconomic changes of the country. Kim [25] found only 14 cases (1.4%) of the hernia among 1,000 examined patients, while in 1999 it was revealed in 41 (4.1%) out of 1,010 individuals [46]. Unlike other investigations, Boghratian et al. [7] observed male gender predilection in patients with hiatal hernia after examination of 4,700 Iranians. Moreover, the disease is observed mostly in older patients. However, due to the abnormal prenatal enlargement of the esophageal hiatus, a congenital sliding hiatal hernia may also be found but have to be differ from the short esophagus (see below) [34]. Furthermore, the hernia is commonly associated with diverticular disease and less frequently with cholelithiasis—Sait’s triad [21]. Also obesity (BMI ≥ 25 kg/m²), advanced renal insufficiency, prolapse of the mitral valve [22] and persistent high intraabdominal pressure increase risk of the hernia [13, 37, 45]. High abdominal pressure was also found as one of the leading factors in other diseases associated with a hiatal hernia, i.e., inguinal hernia and prolapse of pelvic organs [13, 39]. As a consequence of herniation, a relaxation of the lower esophageal sphincter, wider cardiac angle and esophageal empting impairment increase the possibility of the gastro-esophageal reflux. On the other hand, the hiatal hernia and gastro-esophageal reflux disease (GRED) itself are risk factors for Barrett’s esophagus, chronic blood loss and iron-deficiency anemia [5, 36], vertebral fracture [31], atherosclerosis, as well as esophageal and laryngeal neoplasms [5].

The second type of hiatal hernia is the paraesophageal one, morphologically characterized by the normal position of the cardia but the adjusted part of the stomach fundus is slided superiorly through the esophageal hiatus. The paraesophageal and mixed-form hernias—that combined sliding and paraesophageal features—have not been extensively epidemiologically studied. Both types (II and III according to Akerlund) are observed less often [23] nevertheless their surgical treatment significantly increases morbidity and mortality [12, 40]. In advanced stage of the mixed-form hernia, the whole stomach is located intrathoracically (upside-down stomach hernia). Nowadays, prevalence of such anomaly increases especially in symptomatic patients [35]. According to the currently published data, a frequency of the intrathoracic stomach is about 52 per one million persons. The disease is strongly associated with age, and affects especially elderly people (>65 year), more commonly blacks than whites [35].

The last type of the hiatal hernia is the congenital short esophagus. According to the classic description by Peters [34], it significantly differs from the acquired type that is always associated with the sliding diaphragmatic hernia (Table 2). The incidence of the developmental anomaly is estimated as 3–14% of all patients that undergo antireflux surgery [14] and 0.084% of the general population [34].

All anomalies listed above have to be distinguished from congenital or acquired diaphragmatic hernia, in which the stomach with or without other abdominal organs enters the thoracic cavity through diaphragmatic openings other than the esophageal hiatus. Most frequently they are enlarged sternocostal and lumbocostal triangles or pathological openings that are secondary to diaphragmatic injuries or their abnormal development. The congenital diaphragmatic hernia occurs one in every 2,500 live births, and in about 30% of spontaneous abortions [42]. The posterolateral (Bochdalek) and anterolateral (Morgagni) types are found in 70 and 27%, respectively. In remaining cases (2–3%), the opening is located on the level of the central tendon (septum-transversum type). From among all the Bachdalek’s hernias, the left (85%) and bilateral (2%) ones normally include the stomach [17, 18]. Experimental data suggest that, prenatal exposure to herbicide (i.e., nitrofene), corticosteroids and non-selective cyclooxygenase inhibitors increase the risk of the anomaly. All those xenobiotics may disturb organogenesis by the influence on vascular development of stomach, surrounding viscera and abdominal wall, including diaphragm [8, 10, 11, 18, 29, 33]. However, those findings were not entirely confirmed in humans [24], in which a strong correlation with genetic (Sonic Hedgehog—Shh gene pathways) and environmental factors were found [11]. Furthermore, the disease is more common in males and whites. It commonly complicated respiratory distress, pulmonary hypoplasia, and less frequently, pleural effusion, esophageal reflux, patent ductus arteriosus, atrial and ventricular septal defects, as well as congenital infections, acidosis and neonatal jaundice [28].

The second subgroup of abnormal position of the stomach along the long axis of the organ is various degree rotations of the stomach, which are secondary to the malrotation of the gastrointestinal tract that normally took place in an early stage of the prenatal life [16, 30]. They include: lack, incomplete (<90^o) or over-rotation (>90^o) of the stomach. When the lesions are limited to the stomach or other part of the gut, they may be asymptomatic [1]. Clinically, abnormal rotation of the stomach without its obstruction is also called volvulus. However, the malrotation of the organ could also be associated with various developmental anomalies of the stomach (i.e., congenital paraesophageal hernia), and constitute a part of serious congenital syndromes (e.g., gastric organo-axial, heterotaxy, Meckel–Gruber syndrome) [6, 15, 43]. Additionally, in Meckel–Gruber syndrome, the stomach has a longitudinal, intestine-like shape, without the proper fundus [15].

The group of abnormal positions among horizontal axis contains gastric cascades characterized by a biloculation of the gastric cavity into a ventral (corpus and antrum) and a dorsal (fundus) recess [27]. Such abnormal position may be congenital, functional or secondary to organic disorders of the stomach and surrounding organs, mostly peritoneal adhesions. Due to lack of any specific symptoms its incidence is unknown.

Stomach shape may be also affected by the feeding habits. A chronic large amount of food taken day after day may increase the organ volume. Unlike enlargement after vagotomy, such “physiologically” large stomach may be reversible [16, 30, 38].

In conclusion four primary groups of stomach variations were established: abnormal position along longitudinal (I) and horizontal axis (II), as well as abnormal shape (III) and stomach connections (IV). The first group contained the stomach rotation and translocation to the chest cavity, including sliding, paraesophageal, mixed-form and upside-down hiatal diaphragmatic hernias, short esophagus, and the other diaphragmatic hernias. The second group included the stomach cascade of different stages. The third and fourth ones comprised developmental variations and organ malformations. The last group (V) enclosed mixed forms that connect two or more previous variations.