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Acute disorders of mesenteric circulation. The pathogenesis, clinical manifestations, diagnosis, principles of conservative and surgical treatment.
■It is a very serious surgical emengency , usually affecting the superior mesenteric artery or vein .
■Sudden loss of blood flow to the small intestine is called acute mesenteric ischemia. The acute type is often caused by a blood clot and requires an immediate treatment, such as surgery.
Aetiology
Both acute and chronic mesenteric ischemia are caused by a decrease in blood flow to the small intestine. Acute mesenteric ischemia is most commonly causedby a blood clot in the main mesenteric artery. The blood clot often starts in the heart. The chronic form is most commonly caused by a buildup of fatty deposits, called plaque, that narrows the arteries.
1) Mesenteric arterial embolism is the commonest cause .
2) Mesenteric acute arterial thrombosis .
3) Mesenteric venous thrombosis may be idiopathic or due to portal hypertension or intra-abdominal sepsis .
Pathology
·Mucosa (most sensitive layer to ischaemia) ,within 3 hours of vascular obstruction , sloughs , ulcerate and bleeds in the lumen ® bacteria can cross mucosal barrier
·After few hours, the whole thickness of intestine is affected and exudes seroanguinous fluid in the peritoneum .
·Loss of peristalsis in the affected segment ® adynamic I.O ® proximal distension of intestine by gas and fluid.
·Within 6-12 hours , intestinal gangrene ® perforation ® peritonitis ® paralytic ileus ® generalized distension .
Risk factors
■ The most common risk factors for acute mesenteric ischemia include:
•Atrial fibrillation — an irregular and often very rapid heart rhythm.
•Congestive heart failure — a condition in which the heart muscle doesn’t pump blood as well as it should.
•Recent vascular surgery.
■ The most common risk factors for chronic mesenteric ischemia include:
• Type 2 diabetes.
• High cholesterol levels.
• High blood pressure.
• Artery disease.
• Smoking.
• Obesity.
• Older age.
Clinical picture
1) Sudden severe diffuse abdominal pain , is main symptoms ,not relived by narcotics or nasogastric suction.
§ In early stage there are little physical signs , no corresponding to the severity of pain .
1) Tenderness , rebound tenderness ,rigidity , gaurdening an limitation of movement of anterior abdominal wall with respiration
2) Vomiting , distension and absolute constipation .
3) Hypovolaemic shock due to blood loss & peritonitis.
Complications
■ If not treated promptly, acute mesenteric ischemia can lead to:
• Irreversible bowel damage. Not getting enough blood flow to the bowel can cause parts of the bowel to die.
• Sepsis. This potentially life-threatening condition is caused by the body releasing chemicals into the bloodstream to fight infection. In sepsis, the body overreacts to the chemicals, triggering changes that can lead to multiple organ failure.
• Death. Both of the above complications may lead to death.
■People with chronic mesenteric ischemia can develop:
• Fear of eating. This happens because of the after-meal pain associated with the condition.
• Weight loss that isn’t intended. This can occur as a result of the fear of eating.
• Acute-on-chronic mesenteric ischemia. Symptoms of chronic mesenteric ischemia can get worse, leading to the acute form of the condition.
Differential Diagnosis
■ The early identification of AMI is paramount to reduce the likelihood of debilitating morbidity and high mortality.
■ AMI has a vague presentation, and a high index of suspicion is necessary to diagnose suspected patients because of the life-threatening potential of the disease.
■ Findings of abdominal pain out of proportion to a physical exam and cardiovascular risk factors that predispose a patient to embolism and peripheral thrombosis should alert the clinician to consider AMI.
■ Diseases to consider in the differential diagnosis are those that cause acute abdominal pain and are therefore variable.
■ These include acute colitis, ruptured abdominal aortic aneurysm, bowel obstruction, diabetic ketoacidosis, gastrointestinal perforation, and malignancy.
Diagnosis
1)Blood picture : there is marked leucocytosis .
2)Serum amylase : may be elevated but is not high as in acute pancreatitis .
3)Plain x-ray : show gas with fluid levels in the proximal intestine
4)CT & MRI to detect the definite oclusion of artery
5)Laparoscopic exploration .
Treatment
⁕Urgent operation after preoperative preparation .
·Pre-operative preparation : IV fluid , IV antibiotics , nasogastric tube suction .
·Urgent laparotomy :
§ In viable intestine with reversible ischaemia : Revascularization by embolectomy in embolism or endarterectomy in acute thrombosis .
§ Resection of gangrenous intestine .
Prognosis
■The prognosis of AMI is poor, with patients experiencing high morbidity and mortality rates. While there is a downward trend in mortality rates since the 1960s, the AMI mortality range remains high, occurring at rates between 60% and 80%. The specific AMI classification affects the likelihood of mortality, with acute embolism having a better prognosis, followed by NOMI and acute thrombosis. Factors associated with mortality include advanced age, bowel resection during second-look surgery, metabolic acidosis, renal insufficiency, and symptom duration.
■A study by Gupta et al. found a 30-day morbidity rate of 56%. Major postoperative 30-day complications included ventilator use over 48 hours, septic shock, pneumonia, and sepsis. Follow-up surgical interventions were common, with 30% of patients revisiting the surgical department in 30-days, and 14% of patients having a hospital stay longer than 30 days.
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