Stomach — MRCS Part B Anatomy

The stomach and its blood supply dissected, with the questions the examiners want: its parts, its nerves, what a gastrectomy takes and what a vagotomy did.

Parts

The cardia around the oesophageal opening; the fundus above the level of that opening, under the left dome of the diaphragm, where swallowed air collects; the body; the pyloric antrum, the pyloric canal and the pylorus itself, a thick ring of circular muscle at the transpyloric plane. The lesser curvature faces up and to the right with the lesser omentum attached, and the angular notch on it marks where the body ends; the greater curvature faces down and to the left and carries the greater omentum and the gastrosplenic ligament.

Blood supply

All from the coeliac trunk. Along the lesser curve run the left gastric artery, from the trunk itself, and the right gastric from the common hepatic; along the greater curve the left gastro-epiploic from the splenic and the right gastro-epiploic from the gastroduodenal, meeting in the omentum; and the short gastric arteries from the splenic supply the fundus through the gastrosplenic ligament. The veins follow the arteries into the portal system, the left gastric vein carrying the oesophageal anastomosis that becomes varices. The gastroduodenal artery runs behind the first part of the duodenum and is the vessel that a posterior ulcer erodes.

Innervation

Parasympathetic from the vagus: the anterior vagal trunk, mostly from the left vagus, runs down the front of the lesser curve giving hepatic and pyloric branches and the anterior nerve of Latarjet; the posterior trunk, mostly from the right, gives a coeliac branch and the posterior nerve of Latarjet. They drive acid and pepsin secretion and motility. Sympathetic fibres from T6 to T9 reach the stomach through the greater splanchnic nerves and the coeliac plexus, carrying the pain of a gastric ulcer to the epigastrium.

Gastrectomy

A distal (subtotal) gastrectomy for an antral tumour, reconstructed as a Billroth I to the duodenum or Billroth II or Roux-en-Y to the jejunum; a total gastrectomy for a proximal or diffuse tumour, with a Roux-en-Y oesophagojejunostomy; a proximal gastrectomy, rarely used; and a sleeve gastrectomy, which removes the greater curve for weight loss. The D2 dissection takes the nodes along the named arteries with the specimen.

Vagotomy

Cutting the vagal supply removes the cephalic stimulus to acid secretion, so ulcers healed, but a truncal vagotomy also paralysed the antrum and pylorus, so it needed a drainage procedure — a pyloroplasty or gastro-enterostomy — and it gave diarrhoea, gallstones and dumping. A highly selective vagotomy divided only the branches to the acid-secreting body and fundus and kept the nerves of Latarjet to the antrum, so the stomach still emptied. Proton pump inhibitors and eradication of Helicobacter made the operation obsolete.

Dumping

Early dumping, within half an hour of a meal, is the hypertonic contents of a stomach without a pylorus flooding the jejunum, drawing fluid into the bowel: bloating, cramps, diarrhoea, and faintness from the fall in circulating volume. Late dumping, two or three hours later, is reactive hypoglycaemia from the surge of insulin that the rapid glucose load provoked. Small dry meals, low in sugar, are the treatment.

The mucosa

It secretes acid and intrinsic factor from the parietal cells, pepsinogen from the chief cells, gastrin from the G cells of the antrum, and the mucus and bicarbonate that protect it from its own acid; it also absorbs alcohol, water and some drugs. The rugae let it stretch, and its epithelium renews itself every few days.