James is a 57-year old teacher who presented in the ED with haematemesis (vomiting blood) and abdominal discomfort. James is an alcoholic. He consumes 25 units of alcohol per day and has done for the past 15 years. James was diagnosed with portal hypertension secondary to cirrhosis.
a) Describe or draw the formation of the portal vein and explain, with reference to relevant anatomy, why portal hypertension can lead to haematemesis.
The portal vein is a huge structure and is formed behind the neck of the pancreas (at around L1). It is formed by the junction of the splenic vein and the superior mesenteric vein. The inferior mesenteric vein normally drains the hindgut to the splenic vein, but in reality, can also drain to the SMV or PV directly.
The portal venous system allows for deoxygenated blood from most of the GI tract to be transported to the liver for further processing before travelling back to the heart via the inferior vena cava by hepatic veins.
Increased pressure in this system may cause blood to shunt through the portosystemic anastomoses. These are located around the umbilicus, lower rectum/upper anal canal and lower oesophagus. The portosystemic anastomoses provide alternative routes of circulation and ensure that venous blood still reaches the heart and bypasses the liver.
The consequence is that the portosystemic anastomoses may dilate, making them visible, swollen and liable to rupture. Dilatation of the anastomoses at the lower oesophagus can lead to oesophageal varices which can rupture and bleed, resulting in haematemesis.
b) Explain the other physical examination findings that might be associated with portal hypertension.
- Splenomegaly – The spleen drains into the portal venous system Increased portal venous pressure is likely to cause vascular congestion in the spleen and thus an increase in its size. It will enlarge toward the right iliac fossa.
- Anorectal varices (there are NOT haemorrhoids).
- Caput medusae (distended superficial epigastric veins, which can be seen radiating out from the umbilicus across the abdomen – called caput medusae because they often resemble the head of Medusa – I personally don’t see it but hey ho).
c) Describe where the oesophagus starts and ends (with reference to vertebral levels) and state where it passes through the diaphragm and the part of the diaphragm contributing to the lower oesophageal sphincter.
The oesophagus starts at the C6/7 vertebral level (at the bottom end of the laryngopharynx) and travels inferiorly before terminating at the stomach. Traditionally, the oesophagus was thought to pass through the diagram (at the crus) at T10, however now it’s been found to be closer to T11–12. The right crus of the diaphragm loops around the oesophagus forming part of the lower oesophageal sphincter.