Surgical Emergencies
Question 42 of 180
A 78 year old man presents to the Emergency Department complaining of abdominal pain. He describes a sudden onset of pain approximately 4 hours ago, he describes the pain as "severe" and "all over". There has been no change to his bowel or bladder function. He is nauseous but has not vomited. He has a past medical history of hypertension, gout and atrial fibrillation. What is the most likely diagnosis?
Answer:
Clinicians must maintain a high index of suspicion for bowel ischaemia, because the signs and symptoms are relatively non-specific yet the condition has significant morbidity and mortality. Early recognition, appropriate diagnostic studies, and aggressive treatment are necessary to improve outcome. Clinical features include:- Abdominal pain
- Sudden onset of diffuse abdominal pain suggests acute mesenteric ischaemia or non-occlusive mesenteric ischaemia.
- However, chronic symptoms of vague, diffuse abdominal pain may be indicative of chronic mesenteric ischaemia.
- In contrast, colonic ischaemia may cause focal or diffuse abdominal pain and often has a more insidious onset, over several hours or days.
- Rectal bleeding - haematochezia or melaena
- Diarrhoea
- Abdominal tenderness - perceived pain is out of proportion of tenderness on examination
Ischaemic Bowel Disease
Surgical Emergencies
Last Updated: 8th September 2021
Ischaemic bowel disease encompasses a heterogeneous group of disorders caused by acute or chronic processes, arising from occlusive or non-occlusive aetiologies, which result in decreased blood flow to the gastrointestinal tract. Intestinal ischaemia can be classified into three broadly defined types:
- Acute mesenteric ischaemia
- Chronic mesenteric ischaemia
- Colonic ischaemia
Causes
- Arterial compromise
- Embolism (Responsible for approximately 50% of acute mesenteric ischaemia events.)
- Thrombosis (About 15% to 20% of acute mesenteric ischaemia results from thrombus occurring as a progression of atherosclerosis at the origin of the superior mesenteric artery)
- Vasculitis
- External compression of the coeliac access and blood vessels supplying the bowel
- Venous compromise
- Venous thrombosis (Accounts for approximately 5% of cases of acute mesenteric ischaemia. Frequently involves the superior mesenteric vein.)
- Hypoperfusion (Accounts for as much as 20% of cases of acute mesenteric ischaemia)
- Shock, or hypotension, or relative mesenteric hypotension (from any aetiology). Prominent causes include heart failure, dialysis, drug-related, recent surgery or trauma or infection
Pathophysiology
- Ischaemia occurs secondary to hypoperfusion of an intestinal segment. When hypoperfusion is insidious in onset, collateral blood flow may develop, precluding or minimising ischaemia; however, the regions of the intestine with a solitary arterial supply, and the watershed areas, are both at increased risk of developing ischaemia.
- The degree of intestinal injury is dependent on the duration and severity of ischaemia. Acute or subacute mucosal sloughing and ulcerations occur as a result of ischaemia. The loss of the mucosal barrier allows for bacterial translocation and toxin or cytokine absorption. Re-perfusion injury can also occur if blood supply is re-established after a prolonged interruption.
- Thromboembolic events that lead to mesenteric ischaemia usually involve the SMA instead of the other mesenteric arteries (IMA and coeliac artery). This is because of the anatomical position of the SMA; the SMA is positioned vertically in relation to the aorta while the other vessels form more oblique angles with the aorta.
Risk factors
- Old age
- Smoking
- Hypercoagulable states
- Atrial fibrillation
- Myocardial infarction
- Structural heart defects
- History of vasculitis
Clinical features
Clinicians must maintain a high index of suspicion for bowel ischaemia, because the signs and symptoms are relatively non-specific yet the condition has significant morbidity and mortality. Early recognition, appropriate diagnostic studies, and aggressive treatment are necessary to improve outcome.
- Abdominal pain
- Sudden onset of diffuse abdominal pain suggests acute mesenteric ischaemia or non-occlusive mesenteric ischaemia.
- However, chronic symptoms of vague, diffuse abdominal pain may be indicative of chronic mesenteric ischaemia.
- In contrast, colonic ischaemia may cause focal or diffuse abdominal pain and often has a more insidious onset, over several hours or days.
- Rectal bleeding - haematochezia or melaena
- Diarrhoea
- Abdominal tenderness - perceived pain is out of proportion of tenderness on examination
Differential diagnosis
- Infectious colitis
- Ulcerative colitis
- Crohn's disease
- Diverticular disease
- Large bowel obstruction
- Peptic ulcer disease
- Small bowel obstruction
- Acute pancreatitis
- Gastroenteritis
Investigations
- Blood tests
- FBC (leucocytosis, anaemia, evidence of haemoconcentration)
- Serum lactate (raised lactate)
- ABG (acidosis)
- U&Es (uraemia, elevated creatinine)
- Serum amylase (elevated in late disease)
- Coagulation (underlying prothrombotic disease)
- ECG (atrial fibrillation, arrhythmia, acute myocardial infarction)
- Erect CXR (free air if perforation present)
- AXR (air-fluid levels, bowel dilation, bowel wall thickening, pneumatosis)
- CT scan with contrast/CT angiogram
- CT is the current first-line investigation of choice when acute ischaemia is suspected and should be obtained early.
- CT provides evidence for the extent of bowel compromise from ischaemia. It also enables stratification of patients to identify those who would benefit from mesenteric angiography from those who require primary surgery.
- CT angiography has replaced conventional angiography as standard practice for diagnosis of acute mesenteric ischaemia.
- Mesenteric angiography
- Historically this has been the definitive test for diagnosing mesenteric ischaemia. In current practice it is usually preceded by positive CT angiography in the acute setting.
- Usually performed with the intention of endovascular intervention.
Management
- Treatment for ischaemic bowel disease depends on the anatomical location and severity of ischaemia, its underlying pathophysiology and time course.
- Initial measures include supplemental oxygen via a mask, correction of hypotension with fluids and inotropic support if required, assigning nil by mouth status, inserting a nasogastric tube for decompression, and correction of any heart arrhythmias and metabolic abnormalities.
- Antibiotics suitable for enteric coverage (e.g. third-generation cephalosporin or quinolone plus metronidazole) should be given to all patients, as bacterial translocation may be significant due to the loss of the normal intestinal mucosal barrier. Antibiotics should be prescribed according to local antimicrobial guidelines that are targeted against local sensitivities.
- The presence of infarction, perforation, or peritonitis warrants urgent exploratory laparotomy or laparoscopy. The exact nature of the subsequent procedures will depend on preoperative investigations and intra-operative findings.
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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 |
