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Ischaemic Colitis

 

Ischaemic Colitis occurs when there is a reduced blood supply to the colon, which results in inflammation and injury. It is most commonly seen in people aged over 50. However, it can still present in a younger person. Assessing disease severity rather than aetiology is the main priority in this acute patient as this condition can deteriorate into gangrenous bowel, perforation and sepsis leading to critical illness and even death.

 

Colonic Supply of the Superior Mesenteric Artery

 

Branches of the SMA include the:

  • Jejunal Arteries
  • Ileal Arteries
  • Ileocolic Artery
  • Right Colic Artery
  • Middle Colic Artery

 

Respectively, these branches supply the:

  • Jejunum
  • Ileum
  • Caecum and Appendix
  • Ascending Colon  
  • Transverse Colon

 

    Colonic Supply of the Inferior Mesenteric Artery

     

    Branches of the IMA include:

    • Left Colic Artery
    • Sigmoid Artery
    • Superior Rectal Artery

     

    Respectively, these branches supply the:

    • Splenic Flexure and Descending Colon
    • Sigmoid Colon
    • Upper Rectum

     

      Pathophysiology

       

      There are two main mechanisms that cause ischaemic colitis.

      • Non-occlusive ischaemia results from systemic hypotension causing the hypersensitive blood vessels of the colon to vasoconstrict thereby reducing blood flow.
      • Occlusive ischaemia results from a thrombosis, embolus or other obstructing body that blocks the blood vessels supplying the colon.

       

        Aetiology

         

        Occlusive Aetiologies

        • Vascular Thromboembolism
        • Vascular Thrombosis
        • Abdominal Aortic Aneurysm
        • Previous Gastric, Colonic or Rectal Surgery
        • Tumour Compression of Vessels
        • Amyloidosis
        • Vasculitis
        • Sickle-cell crisis
        • Oestrogen/progestogen drugs

         

           

          Non-Occlusive Aetiologies

          Systemic:

          • Hypovolemic
          • Hypotension
          • Myocardial Infarction
          • Valvular Heart Disease
          • Congestive Heart Failure

           

          Local:

          • Vasopressin
          • Ergotamine
          • Increased intraluminal colonic pressure
          • Digitalis Toxicity

           

            Presentation

             

            Patients with Ischaemic Colitis classically present with:

            • Sudden onset, left lower quadrant abdominal pain
            • Abrupt onset diarrhoea
            • Haematochezia or occassionally melena.

             

             

            However, the patient may also experience:

            • Nausea
            • Vomiting
            • Tenesmus
            • Fever
            • Hypotension
            • Tachycardia
            • Abdominal distension
            • Tenderness

             

              Differential Diagnosis

               

              • Ulcerative Colitis - Patients complain of PR bleeding, chronic diarrhoea and lower abdominal pain 
              • Crohn's Disease - Form of Inflammatory Bowel Disease involving right iliac fossa pain, weight loss and diarrhoea
              • Peptic Ulcer Disease - Usually epigastric pain with associated nausea and vomiting
              • Small Bowel Obstruction - Abdominal distension, vomiting and nausea with a past history of abdominal surgery 
              • Acute Pancreatitis - Epigastric pain that radiates to the back. History of gallstones or alcohol abuse
              • Large bowel obstruction -  Constipation 
              • Diverticular Disease - Fever common in diverticulitis with pain depending on where the diverticula are and diarrhoea
              • Gastroenteritis - Epigastric pain is less profound than that found in ischaemia. Nausea and vomiting are common.

               

                Diagnosis

                 

                • Colonoscopy is the gold standard for diagnosing ischaemic colitis.
                • It should be performed without delay in the absence of peritoneal signs and any evidence of intra-abdominal catastrophe.  

                 

                The picture depicts a very severe case of Ischaemic Colitis. The colonoscopic image shows evidence of inflammation, swelling and an almost bluish colour to the bowel wall.

                 

                Pathological Findings

                Other Investigations

                 

                • CT scan - Normally used for abdominal pain and rectal bleeding. Can show complications or offer alternate diagnosis 
                • Abdominal X-ray - Can show colic distension or pneumoperitoneum (air in the peritoneum)

                 

                  Classification of Ischaemic Colitis

                   

                  Ischaemic Colitis is managed according to the classification the patient presents with.

                  The three classifications are:

                  • Transient Disease
                  • Stricture Formation
                  • Gangrenous Injury

                   

                     

                    Management

                    Surgical Intervention

                     

                    Resection of the bowel is indicated in bowel infarction. The order of events is as follows: 

                    • Laparotomy - A large incision is made through the abdominal wall
                    • Blood vessels are mobilised and ligated 
                    • Gangrenous bowel is resected 
                    • Either anastomosis of the two bowel ends or a colostomy is required 

                     

                    An anastomosis carries the risk of dehiscence, which can chronologically result in:

                    • Contamination of the peritoneum 
                    • Peritonitis 
                    • Sepsis 
                    • Death

                     

                    However, a colostomy although safer, has a huge psychosocial and physical impact on the patients life. It is up to the surgeon to make the best decision for the patient. 

                     

                    Types of Bowel Resection

                     

                    The image on the right depicts a right hemi-colectomy, which involves resecting the ascending colon and anastomosing the transverse colon with the small bowel. Other operations include:

                    • Left hemi-colectomy - Resection of the descending colon 
                    • Total Colectomy - resection of the whole colon
                    • Sigmoidectomy - Resection of the sigmoid colon
                    • Hartmann's Operation - A sigmoidectomy followed by a terminal colostomy and closure of the rectal stump

                     

                      References

                       

                      http://www.gastro.com/Gastro/photography/ischemic_colitis.aspx

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