Anatomy
Abdomen
The hepatic portal vein is formed from the union of which of the following veins:
Answer:
The portal vein is formed from the union of the superior mesenteric and splenic vein posterior to the neck of the pancreas at the level of vertebra L2.Hepatic Portal Vein
Anatomy / Abdomen / Liver and Biliary Tract
Last Updated: 13th October 2022
The portal vein is the final common pathway for the transport of venous blood from the spleen, pancreas, gallbladder and abdominal part of the gastrointestinal tract.
It is formed from the union of the superior mesenteric and splenic vein posterior to the neck of the pancreas at the level of vertebra L2.
![By Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://primary-cdn.frcemsuccess.com/wp-content/uploads/2017/02/Portal-vein.gif)
Hepatic Portal Vein. (Image by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
Portosystemic Anastomoses
The hepatic portal system drains deoxygenated nutrient-rich blood from the visceral organs of the abdomen to the liver. Normally 100% of portal venous blood flow is recovered from the hepatic veins. In patients with elevated portal vein pressure e.g. from cirrhosis, there is significantly less blood flow to the liver and the rest of the blood enters collateral channels which drain into the systemic circulation at specific points.
Portosystemic anastomoses occur at certain specific points, the largest of these being:
- The gastroesophageal junction around the cardia of the stomach where the left gastric vein and its tributaries form a portosystemic anastomosis with tributaries to the azygos system of veins of the caval system
- The anus where the superior rectal vein of the portal system anastomoses with the middle and inferior rectal veins of the systemic venous system
- The anterior abdominal wall around the umbilicus where the portal paraumbilical veins anastomose with systemic veins on the anterior abdominal wall
When pressure in the portal vein is elevated, venous enlargement (varices) tends to occur at and around these sites producing:
- oesophageal varices at the gastroesophageal junction
- varices at the anorectal junction
- caput medusae at the umbilicus
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
