Anatomy
Abdomen
The abdominal aorta bifurcates into its terminal branches at which of the following vertebral levels:
Answer:
The abdominal aorta bifurcates into the right and left common iliac artery at the level of vertebra L4. This bifurcation can be visualised on the anterior abdominal wall as a point approximately 2.5 cm below the umbilicus.Abdominal Aorta
Anatomy / Abdomen / Posterior Abdominal Wall
Last Updated: 26th May 2023
The abdominal aorta begins at the aortic hiatus of the diaphragm, anterior to the lower border of vertebra T12. It descends through the abdomen, anterior to the vertebral bodies, and by the time it ends at the level of vertebra L4 it is slightly to the left of the midline.
Surface Anatomy
The main terminal branches of the abdominal aorta are the two common iliac arteries. This bifurcation can be visualised on the anterior abdominal wall as a point approximately 2.5 cm below the umbilicus.
Surface Anatomy of the Abdominal Aorta. (Image modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
Branches
The abdominal aorta gives rise to:
- three anterior unpaired visceral branches
- the coeliac trunk supplying the abdominal foregut (upper border of L1 vertebra)
- the superior mesenteric artery supplying the abdominal midgut (lower border of L1 vertebra)
- the inferior mesenteric artery supplying the abdominal hindgut (L3 vertebra)
- three lateral paired visceral branches
- the middle suprarenal (adrenal) arteries
- the renal arteries (L2 vertebra)
- the gonadal arteries
- posterior parietal branches
- the inferior phrenic arteries (paired)
- the lumbar arteries (paired)
- the median sacral artery (single)
- two terminal branches
- left common iliac artery
- right common iliac artery
Branches of the Abdominal Aorta. (Image by OpenStax College [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons)
Clinical Implications
Abdominal aortic aneurysm (AAA) is a permanent pathological dilation of the aorta with a diameter >1.5 times the expected anteroposterior (AP) diameter of that segment, given the patient's sex and body size. The most commonly adopted threshold is a diameter of 3 cm or more. More than 90% of aneurysms originate below the renal arteries and end above the iliac arteries.
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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 |
