Anatomy
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Abdomen
A patient is brought to ED following a road traffic collision. CT demonstrates retroperitoneal haemorrhage. Which of the following structures is the most likely source of the bleeding:
Answer:
The second and third parts of the duodenum are retroperitoneal, thus are the most likely source, as all the others listed are intraperitoneal structures.Peritoneum
Anatomy / Abdomen / Topography of Abdominal Cavity
Last Updated: 3rd April 2020
The peritoneum is a continuous double-layered serous membrane. The parietal peritoneum lines the walls of the abdominal cavity and the visceral peritoneum lines the viscera. Between the parietal and visceral layers of peritoneum is a potential space, the peritoneal cavity.
Intraperitoneal vs. Retroperitoneal
Abdominal viscera are either suspended in the peritoneal cavity by folds of peritoneum called mesenteries (intraperitoneal viscera) or are outside the peritoneal cavity bound to the posterior abdominal wall (retroperitoneal viscera). Retroperitoneal organs are only covered in peritoneum on their anterior surface.
A useful mnemonic to help remember which abdominal organs are retroperitoneal is SAD PUCKER:
- Suprarenal glands
- Aorta and Inferior vena cava
- Duodenum (2nd and 3rd parts)
- Pancreas (except for the tail)
- Ureters (proximal) and Bladder
- Colon (ascending and descending)
- Kidneys
- (O)esophagus
- Rectum (lower two-thirds)
Peritoneum. (Image by OpenStax College [CC BY 3.0 , via Wikimedia Commons)
Innervation
The parietal peritoneum associated with the abdominal wall is innervated by somatic afferents carried in branches of the associated spinal nerves and is therefore sensitive to pressure, pain and temperature, and gives rise to well-localised pain. The diaphragmatic peritoneum is supplied by the phrenic nerve (C3 - C5) and the remainder of the parietal peritoneum is supplied segmentally by intercostal and lumbar nerves.
The visceral peritoneum is innervated by visceral afferents that accompany autonomic nerves back to the CNS and therefore activation gives rise to referred and poorly localised sensations of discomfort and to visceral motor activity.
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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 |
