BOWEL WALL ATTENUATION- NOT JUST ANOTHER SHADE OF GREY. T Barrow, P Arora, S Sukumar, V Rudralingam

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1 OWEL WLL TTENUTION- NOT JUST NOTHER SHDE OF GREY T arrow, P rora, S Sukumar, V Rudralingam

2 LERNING OJECTIVES Gain a better appreciation of the variation of bowel wall attenuation seen in a range of bowel pathology. Understand how through clinical information and systematic image interpretation of other imaging findings (site, mural enhancement pattern and surrounding changes) early diagnosis can be expedited.

3 CKGROUND Computed tomography (CT) is frequently the first line imaging modality performed in patients presenting acutely to the emergency department. robust knowledge and systematic approach to bowel mural attenuation patterns encountered in bowel pathology can aid timely diagnosis and early initiation of potentially life-saving therapy.

4 NORML PPERNCES ULTRSOUND: Graded compression sonography can be utilised to evaluate the bowel wall CT: Normal Fat Halo Water Halo Normal bowel is readily compressible Thickened bowel loops are typically noncompressible and show surrounding increased fat echogenicity

5 DIFFERENTIL DIGNOSIS OWEL WLL TTENUTION HYPERTTENUTION Shock bowel Haemorrhage Infection Inflammation Vasculitis OEDEM GREY TTENUTION SOFT-TISSUE DENSITY Tumours Fibrosis FT HLO Obesity Chronic Colitis LCK TTENUTION Infarcted bowel Iatrogenic: Feeding tube insertion Idioopathic: Pneumatosis Cystoides Intestinalis Post Resolution of owel Obstruction

6 HYPERTTENUTION

7 HYPERTTENUTION- SHOCK OWEL Fig 1. Shock owel Secondary to Necrotising Fasciitis. Intravenous contrast-enhanced CT images (-C) shows shocked small bowel with mucosal striking hyperenhancement (arrow head), flattening of the infra-hepatic inferior vena cava and left adrenal hyperenhancement (arrow) in a patient with necrotising fasciitis. C * Learning Point: Mucosal injury and subsequent disruption results in contrast leakage and visualised mural hyperenhancement. Learning Points: ssociated findings include: 1. Mural hyperenhancement & thickening 2. Collapsed IVC (<9mm P diameter) 3. Small calibre abdominal aorta (<13mm P diameter) 4. ilateral adrenal hyperenhancement

8 HYPERTTENUTION- HEMORRHGE * Fig 2. Small owel Intramural Haemorrhage Secondary to nticoagulation. xial () and coronal () intravenous contrast enhanced CT images show diffuse hyperattenuation of the duodenal loop, with intramural hyperattenuation and luminal effacement (arrows) consistent with acute intramural haemorrhage. Note the presence of blood within the right anterior pararenal space (star). Learning Points: Spontaneous intramural small-bowel haematoma rarely occurs in patients who are anticoagulated or have an underlying thrombophilia. CT characteristics include circumferential wall thickening, intramural hyperdensity, luminal narrowing, and intestinal obstruction.

9 HYPERTTENUTION- HEMORRHGE C D Fig 3. Intramural Haemorrhage Secondary to Henoch Schonlein Purpura. xial () and long () US images showing thickened bowel wall on US. Pre-contrast axial CT image C) shows mural hyperattenuation (arow head). Corresponding intravenous contrast-enhanced CT image (D) shows confluent distal ileal thickening from oedema and haemorrhage (arrow) in a young patient presenting with abdominal pain and vasculitic rash. Learning Points: GI symptoms occur in 75% of patients with Henoch Schonlein Purpura (HSP). Intramural haemorrhage may be seen during the first 10 days after the onset of symptoms.

10 GREY TTENUTION OEDEM SOFT-TISSUE DENSITY

11 OEDEM

12 OEDEM- INFECTION Fig 4. owel Wall Oedema Secondary to Campylobacter Enteritis. Intravenous contrast enhanced axial CT images (, ) of the same patient show uniform long segment distal ileum oedema (arrow) with no significant mesenteric fat stranding or hypervascularity. Learning Points: owel wall oedema carries a wide differential diagnosis-marker of acute gut injury. Imaging findings may be non-specific and clinical history is the most important differentiating factor.

13 OEDEM- INFECTION Fig 5. owel Wall Oedema Secondary to Pseudomembranous Colitis. Portovenous phase contrast-enhanced axial images (, ) demonstrate gross colonic bowel wall oedema (arrow head), haustral fold thickening with overlying mucosal hyperenhancement- ccordian sign (arrows). Learning Points: Early features may include; bowel dilatation, mural thickening. Haustral fold thickening, toxic megacolon and subsequent perforation may be seen in late/fulminant disease.

14 POTENTIL PITFLL- POST RESOLUTION OF OWEL OSTRUCTION C * Fig 6. owel Wall Oedema Secondary to Post Resolution of owel Obstruction. Intravenous contrast-enhanced CT image () confirms large bowel obstruction secondary to sigmoid malignancy (arrow). Fluoroscopic image () shows a colonic stent across the sigmoid colon tumour (star). Subsequent T2-weighted axial MR image (C) post procedure shows resolution of obstruction with residual gross colonic mural oedema giving a segmented appearance (arrow head). Learning Points: The presence of mural oedema may be the only clue to a recent post-obstructive state. This appearance should not be misinterpreted as acute colitis. The obstructing lesion may be benign or malignant. MR may aid diagnosis in difficult cases.

15 OEDEM- VSCULR C * D Fig 7. owel Oedema Secondary to SMV Thrombosis. Transabdominal US image () shows focal small bowel wall oedema (star). Subsequent intravenous contrast enhanced axial (, C) and sagittal (D) images shows water halo attenuation of the distal ileum (arrow head) and underlying SMV thrombosis (arrow). Note fluid and oedema within the small bowel mesentery. Learning Points: Note the vascular arcade is a mandatory review area in the acute abdomen. Imaging is often the only reliable method to reach the diagnosis. The presence of congested small bowel mesentery points towards a venous cause.

16 OEDEM- INFLMMTION Fig 8. owel Wall Oedema Secondary to Neutropenic Enteritis. Intravenous contrast enhanced axial CT images show non-specific long segment mural oedema of the distal ileum with preservation of the normal stratified mural pattern (gut signature), in a neutropenic patient receiving chemotherapy for a gastric neoplasm. Learning Point: Neutropenic enteritis should be considered in immunocompromised patients with distal ileal thickening, which can also affect the caecum (typhilitis).

17 OEDEM- INFLMMTION Fig 9. owel Wall Oedema Secondary to cute Radiation Enteritis. Intravenous contrast-enhanced axial CT image () and sagittal T2-weighted MR image () showing thickened oedematous ileal loops within the perineal hernia (arrow) following radiation therapy. Learning Points: cute radiation changes are non specific with oedematous wall with water halo sign. History is useful in making the correct diagnosis. Radiation enteritis can lead to stricturing.

18 OEDEM- INFLMMTION * Fig 10. owel Wall Oedema Secondary to ctive Crohns Disease. Intravenous contrast enhanced CT images (, ) demonstrates a thickened segment of the terminal ileum with exaggeration of the stratified gut wall layers (arrow). Penetrating ulcer can also be seen (arrow head). Note the presence of associated finding of prominent vasa recta in the peri-enteric fat ( Comb sign ; star) may point to the diagnosis of Crohns disease. Learning Point: Thickened wall, marked contrast enhancement, mural stratification with water halo pattern and perienteric hypervascularity ( Comb sign ) and fistulation indicate active

19 POTENTIL PITFLL- ORL CONTRST * Fig 11. Obscuration of Mural Enhancement by the dministration of Oral Contrast. Intravenous and oral contrast-enhanced CT images (, ) show the presence of Comb s sign (star). Note that the presence of oral contrast limits evaluation of mural stratification and enhancement (arrows). Learning Points: Positive oral contrast agents obscure the mucosa & inner bowel wall. Negative oral contrast, for instance with water preparation, is nowadays favoured and allows for the assessment of the mucosa and gut wall detail.

20 SOFT-TISSUE DENSITY

21 SOFT-TISSUE DENSITY- TUMOURS Fig 12. Soft-Tissue Density Secondary Colonic Malignancy in Longstanding Crohns Disease. Portovenous phase contrast-enhanced CT images (, ) demonstrate the presence of concentric terminal ileal thickening with mucosal hyperenhancement and subtle submucosal fat deposition (arrow) consistent with acute on chronic Crohns disease. In contrast, note annular mass-like thickening of the ileocaecal junction with disruption of mural stratification and irregular tongues of extramural tissue (arrow head). ppearances consistent with colonic neoplasia arising in the background of chronic Crohns disease. Histology confirmed. Learning Point: Features which should raise the possibility of malignancy in patients with chronic colitis include: 1. Loss of normal bowel wall stratification 2. bnormal extramural tongues of tissue 3. Eccentricity of thickening/lesion.

22 SOFT-TISSUE DENSITY- TUMOURS * Fig 13. Soft-Tissue Density Secondary to Small owel Lymphoma. xial portovenous phase CT image of a patient with known small bowel Crohns disease shows pre-stenotic small bowel loop with fat halo in keeping with chronic Crohns (star). In contrast to abnormal soft-tissue attenuation lobular mass-like thickening with aneursymal dilatation of the lumen (arrow head), typical of small bowel lymphoma. Note this is a recognised disease pattern in Crohns. Learning Point: CT assessment of bowel wall attenuation & enhancement pattern can distinguish inflammatory from neoplastic thickening.

23 FT HLO

24 FT HLO- OESITY * Fig 14. Fat Halo in a Patient with a Large ody Habitus. Unenhanced () and portovenous phase contrast-enhanced () CT images shows hepatomegaly. Note the hepatic attenuation is lower than the spleen (star), consistent with NSH. The same patient demonstrates a marked fat halo involving the ascending colon secondary to intramural fat deposition (arrow). Learning Point: In the absence of clinical or radiologic evidence of inflammatory bowel disease, the presence of the fat halo sign may represent a normal finding that is possibly related to obesity.

25 FT HLO- CHRONIC CROHNS * Fig 15. Fat Halo in Crohnic Crohns Disease. Coronal portovenous phase CT images (, ) show fat density bowel wall attenuation (arrows) and associated fibrofatty proliferation (star) in a patient with histologically proven chronic Crohns disease. Learning Points: Fat halo represents infiltration of the submucosa with fat, between the muscularis and the mucosa. Submucosal fat is a feature of longstanding inflammation seen in patients with chronic quiescent ID.

26 LCK TTENUTION

27 LCK TTENUTION- PNEUMTOSIS C D Fig 16. Pneumatosis Secondary to owel Infarction. Portovenous phase contrast-enhanced axial (), coronal on lung () and abdomen windows (C) and sagittal (D) CT images demonstrate the presence of linear crescents of intramural air in a distal ileal loop (arrow head) and a thrombus within the SM (arrow). Learning Points: Careful evaluation of the mesenteric vasculature is important to exclude thromboembolic disease that may be amenable to vascular radiological intervention. CT can map out the extent of infarcted bowel and avoid unnecessary laparotomy. Lung windows are aid depiction of free and mural gas.

28 LCK TTENUTION- PNEUMTOSIS * Fig 17. Pneumatosis Secondary to acterial Overgrowth in a ysmptomatic Patient with Known myloidosis. Intravenous contrast-enhanced axial CT image on soft-tissue () and lung windows () demonstrates the presence of extensive intramural (arrow) and mesenteric gas (star). The patient was clinically well with no peritonism and imaging appearances resolved with conservative management. Learning Points: Long-term bowel stasis is associated with bacterial overgrowth and increased mural permeability allowing for gas to dissect into the wall.. Not all pneumatosis implies bowel ischaemia. Clinical features and correlation with laboratory tests, such as serum lactate, is required.

29 LCK TTENUTION- PNEUMTOSIS C Fig 18. Pneumatosis Secondary to Surgical Jejunostomy. xial intravenous and oral contrast-enhanced (, ) and coronal lung window (C) images show portovenous gas (star) and extensive small bowel intramural gas (arrows) in a patient who has recently undergone gastrectomy with surgical jejunostomy placement. Learning Points: Feeding tube insertion is a recognised cause of pneumatosis,, presumed to be secondary to simple mechanical dissection of gas into bowel wall. Critical distinction between iatrogenic jejunostomy tube insertion vs bowel ischaemia ina the unwell post-operative patient is challenging.

30 CONCLUSION owel wall attenuation has a varied appearance and significance depending on the underlying bowel pathology. timely diagnosis can be reached through the combination of: 1) Clinical history 2) Mural attenuation pattern 3) Pattern of bowel wall thickening 4) Location 5) Extramural changes

31 REFERENCES Stuhlfaut JW, Soto J, Lucey C et-al. lunt abdominal trauma: performance of CT without oral contrast material. Radiology. 2004;233 (3): mes JT, Federle MP. CT hypotension complex (shock bowel) is not always due to traumatic hypovolemic shock. JR m J Roentgenol. 2009;192 (5): W Siti Kamariah CM, Rohaizan Y. Gastrointestinal involvement in Hencoh Schonlein Purpura: Case report. Int Medical Journal 2009;8 (2):