Pictorial Imaging Spectrum of Acute Intestinal Ischemia

1. B Toosi, BSc; D Tso, BSc; K Lee, MD; C Davison, MBChB; A Reimann, MD; F Berger, MD; J Inacio, MD; A Albuali, MD; AmitAhuja, MD; S Nicolaou, MD Pictorial Imaging Spectrum of Acute Intestinal Ischemia

2. PURPOSE/AIM • Review imaging modalities to investigate acute intestinal ischemia • Review role of MDCT in diagnosing acute intestinal ischemia & introduce an ultra high pitch low dose protocol • Differentiate between mesenteric arterial vs. venous ischemia on imaging • Discuss an imaging algorithm for the evaluation of acute intestinal ischemia

3. Acute Mesenteric Ischemia • Responsible for: 1 in 100 of patients presenting with acute abdominal pain. 1 in 1000 of all hospital admissions. • Associated with 60 -100% mortality rate. • Results from decreased blood flow to the intestines. • Patient present with severe abdominal pain in absence of significant findings on physical examination resulting in delay of diagnosis, morbidity and mortality. Gore RM, et al. Clin Gastroenterol Hepatol. 2008 Aug;6(8):849-58

4. Acute Mesenenteric Ischemia Non-Occlusive Arterial (superior mesenteric) Occlusion Venous Thrombosis 60-70% of PMI 5-10% of PMI 20% of PMI Arterial Embolism Arterial Thrombosis 40-50% of PMI 20-30% of PMI Note: PMI: Primary Mesenteric Ischemia (Arterial or Venous occlusive or nonocclusive bowel ischemia) Furukawa A, et al. AJR Am J Roentgenol. 2009 Feb;192(2):408-16.

5. Arterial embolism Arterial thrombosis • Most frequent cause of AMI. (60-70%) • Most emboli lodge in the superior mesenteric artery, 3-10 cm distal to the origin. • 50% lodge distally to the origin of the middle colic artery. • Collateral circulation is poorly developed, therefore the presentation is abrupt. • Responsible for 25% to 30% of all AMI. • Most occur in patients with severe atherosclerotic disease at the origin of the superior mesenteric artery. • The extent of ischemia is more distally distributed than arterial embolism and can reach the transverse colon. • Atherosclerosis progresses slowly overtime allowing for development of a collateral arterial system. Oldenburg WA, et al. Arch Intern Med. 2004 May 24;164(10):1054-62.

6. Sites of mesenteric thrombosis vs. embolism Thrombi Emboli Emboli lodge distal to the origin. Therefore proximal SMA perfusion is maintained and Jejunum remains viable. A clear demarcation seen on laparotomy. Gray Th, Sullivan TM. Curr Treat Options Cardiovasc Med. 2001 Jun;3(3):195-206.

7. Nonocclusive Mesenteric Ischemia. Mesenteric venous thrombosis • Accounts for 20% of all cases. • Usually no pain, abdominal distension. • Usually due to shock • Involves a low cardiac output setting with diffuse mesenteric vasoconstriction • Vasoconstriction in response to hypovolemia, decreased cardiac output, hypotension, vasopressors. • Vasoactive drugs and DIC may play a role. • Accounts for 5-10% of all cases. • Sub acute presentation • Mostly due to hypercoagulable state. • Can also be caused by cirrhosis, neoplasm, surgical injury. • Wide clinical spectrum, from asymptomatic to acute, severe, life threatening. Oldenburg WA, et al. Arch Intern Med. 2004 May 24;164(10):1054-62.

8. Clinical characteristics of acute mesenteric ischemia. Furukawa A, et al. AJR Am J Roentgenol. 2009 Feb;192(2):408-16.

9. Colonic Ischemia • Due to decrease colonic blood supply associated with a lowered systemic perfusion or an anatomic occlusion. • Cause may include: Age, hypotension/ hypovolemia, cardiac thromboembolism , MI, hypercoagulable states, medications • Rapid onset of mild abdominal pain • Tenderness over the affected bowel area Elder K, Leshner B, Solaiman F. Cleve Clin J Med. 2009 Jul;76(7):401-9

10. Differentiating from Mesenteric Ischemia Acute mesenteric ischemia Colonic mesenteric ischemia • Sudden onset of severe abdominal pain out of proportion to the tenderness on physical examination. • Profoundly ill, no bloody stools until late stages. • Report of recurrent severe postprandial abdominal pain • Weight loss • Hematochezia beginning within 24 hours of the onset of pain. Elder K, Leshner B, Solaiman F. Cleve Clin J Med. 2009 Jul;76(7):401-9

11. Summary of imaging modalities used to investigate acute intestinal ischemia Gore RM, et al. Clin Gastroenterol Hepatol. 2008 Aug;6(8):849-58

12. MDCT Protocol for acute intestinal ischemia with low dose alternative Note-Arterial Phase is triggered at the descending aorta at level of diaphragm when 100 HU of contrast density is reached followed by a 5 sec delay. PV AbdoPelvis is started at 70sec post injection.

13. Typical CT findings of mesenteric ischemia. Furukawa A, et al. AJR Am J Roentgenol. 2009 Feb;192(2):408-16.

14. Portal venous gas on plain film.

15. 48 years old male patient with acute abdominal distention. Acute aortic dissection with involvement of SMA origin and left renal vein. Non-perfusion of left kidney. Very poor enhancement of bowel with extensivepneumatosis intestinalis. Gas fills several mesenteric veins and intrahepatic portal veins.

16. Acute aortic dissection Pneumatosis Intestinalis. Non-perfusion of left kidney.

17. 86 years old female with history of renal disease presented with abdominal pain. Severe stenosis at the proximal SMA by non calcified plaque. SMV gas is present. Pneumatosis intestinalis seen within several loops.

18. Pneumatosis intestinalis Portal venous gas Bowel thickening

19. 89 years old male patient with two day history of abdominal pain Dilated and thickened loops of small bowel Filling defect in the superior mesenteric artery Mesenteric stranding

20. 76 years old patient with severe abdominal pain and hypotension. SMA long segment stenosis with poor collateralization. Dilated loops of small bowel

21. 71 years old female with sudden onset of severe abdominal pain and elevated lactate levels. Target sign is observed. A long segment of the proximal jejunum demonstratesmural thickening. Mesenteric stranding

22. 77 year old patient with increased lactate levels and history of atrial fibrillation. Dilated bowel loops with decreased enhancement. Large retroperitoneal hematoma. Oral contrast is from a scan 2 days previously

23. Dilated bowel loops with decreased enhancement.

24. 73 years old patient with history of abdominal surgeries including a SMA bypass. Multiple loops of dilated, fluid filled small bowel. Occluded SMA. Free fluid.

25. Thickened loop of small bowel with hypo-attenuation Free fluid.

26. 43 years old patient with acute pancreatitis. Pneumatosis intestinalis in cecum. Portal venous gas and focal thrombusis seen within the superior mesenteric vein.

27. 70 years old male with left atrial thrombusand acute SMA occlusion.

28. SMV occlusion from a pancreatic tumor with demonstration of venous collaterals.

29. 74 years old female with history of proximal SMA , celiac occlusion and worsening ischemia. Collateral formation from the marginal artery of Drummond. SMA occlusion

30. 57 years old female with central abdominal pain Mural wall thickening of bowel with minimal mesenteric fat stranding. SMV thrombus is present.

31. Dilated and thickened loops of small bowel. Filling defect in the superior mesenteric artery. Likely early mesenteric ischemia.

32. Patient with history of chronic pancreatitis and SMV thrombosis. Large venous collaterals. Bowel thickening.

33. 70 year old male hypotensive patient with rising lactate levels. Pneumatosis intestinalis is present within the right colon. Free gas from perforation

34. 80 years old woman with history of grafting of the abdominal aorta and red blood per rectum. Near complete occlusion of the proximal SMA just distal to the recently placed stent. Poor enhancement of the left side of the colon.

35. Role of MDCT in diagnosis of acute Mesenteric ischemia. According to Oferet al. MDCT Angiography has an accuracy of 95.6%. • 93 consecutive studies on 91 patients with clinically suspected AMI • CT Angiography was diagnostic in 92 studies. • AMI diagnosed in 18 patients • Positive CTA findings were confirmed by surgery in 13 patients and by clinical follow up in 3 cases. • There were two false positives and two false negatives. According to Menke’s meta-analysis, MDCT has a pooled sensitivity of 93.3% and pooled specificity of 94%. MDCT is fast and accurate in diagnosis of AMI. Ofer A, et al. Eur Radiol. 2009 Jan;19(1):24-30. Epub 2008 Aug 9. Menke J. Radiology. 2010 Jul;256(1):93-101.

36. Imaging algorithm for the evaluation of acute intestinal ischemia Plain film YES NO Pertinent History Mesenteric Angiography Dynamic CT Peritoneal findings NO YES Mesenteric Angiography Laparatomy No persistent Peritoneal findings Persistent peritoneal findings Normal Findings Observe Laparatomy Tendler DA, LaMount JT. Acute mesenteric ischemia In: UpToDate, Basow, DS (Ed), UpToDate, Waltham, MA, 2010

37. Future imaging directions • Dual Energy CT Material decomposition can improve hyper enhancement detection, reduce use of contrast material and radiation dose in comparison to conventional CT. Decrease in need for non-contrast CT studies radiation exposure due to virtual reconstruction. • MRI Advances of MRI techniques reduce artifactsdue to bowel peristalsis or respiration leading to more clear images. Yeh BM, et al. AJR Am J Roentgenol. 2009 Jul;193(1):47-54. Lee, HH, et al. J Magn Reson Imaging. 1998 Mar-Apr;8(2):375-83.