Abdominal radiology pattern recognition
- 1. PATTERN RECOGNITION ABDOMEN NUR FAZDLIN BINTI ABDUL RAHIM PROFESSOR NUR YAZMIN 27.08.2020
- 2. OUTLINE ØStricture: Benign vs Malignant ØPolyps & nodules (filling defect) ØThickening: Benign vs Malignant ØEnhancement paAern of bowel wall thickening ØPneumoperitoneum signs ØBowel dilataDon/ obstrucDon – how to approach
- 3. Stricture : Benign vs Malignant
- 4. Stricture Hard to differentiate benign vs malignant course. Can be short / long segment.
- 5. Colonic Stricture Short Øscirrhous colorectal carcinoma (apple core sign) Øpost surgical (anastamotic stricture) Scirrhous: Hard, slow-growing tumour due to formation of dense connective tissue in the stroma.
- 6. Colonic strictures Long (>10cm) Ømalignancy ◦scirrhous colorectal carcinoma ◦gastrointestinal lymphoma Øinflammatory bowel disease (IBD) ◦ulcerative colitis ◦Crohn's disease Øpost radiation Øischaemic stricture Ømuscular hypertrophy as seen in diverticulitis
- 8. Polyps & Nodules (Filling Defect)
- 9. Polyps - Elevated colonic mucosal lesion Benign ◦ Polyps ◦ Epithelial: Adenoma ◦ Non epithelial: Carcinoid ◦ Pseudopolyps ◦ Polyposis syndromes ◦ Hamartomatous ◦ Adenomatous ◦ Lipoma ◦ Leiyomyomas Malignant ◦ Malignant polyp ◦ Adenocarcinoma ◦ Lymphoma
- 10. Benign polyps Elevated colonic mucosal lesion. ØEpithelial ØNon epithelial
- 11. Epithelial – Adenoma ◦Circumscribed area of dysplastic epithelium ◦Rectosigmoid (60%), descending colon (18%), transverse colon (14%), ascending colon and caecum (8%) ◦Size is an indicator of likelihood of malignancy ◦<1cm (<1% risk) ◦1 – 2 cm (10% risk) ◦>2 cm (approximately 50% risk)
- 12. Non epithelial • Lipoma – most common in category, predisposes to intussusception • Leiomyoma – arises from submucosal region causing ulceration and bleed • Carcinoid tumour – potentially malignant tumour of neuroendocrine system. Commonly arises in rectum
- 13. Polyps in barium study Localised area of increased attenuation Viewed en face : ring shadow with sharp inner border If viewed obliquely shows a hat sign
- 15. Bowler hat sign
- 16. Polyps in barium study
- 17. GI Lipoma Most easily distinguishable large bowel tumour Usually submucosal or pedunculated HU -80 to -120
- 18. Polyposis syndromes > 100 polyps in number Divided into: ◦Hamartomatous (Peutz Jeghers, Juvenile polyposis) ◦Adenomatous (Familial adenomatous polyposis (FAP), Turcot, Gardner syndrome)
- 19. Polyposis syndromes - Hamartomatous Peutz Jegher’s syndrome ◦ Autosomal dominant condi;on leading to hamartomas within stomach, small bowel and colon ◦ Associated with mucocutaneous pigments ◦ Polyps itself have no malignant poten;al ◦ However overlying mucosa may become dysplas;c-> causing increased risk of upper GI tract Ca Juvenile polyposis ◦ Smooth pedunculated hamartomatous polyps within the colon ◦ Presents in infancy ◦ Increased risk of developing carcinoma
- 20. Peutz Jegher’s syndrome Elongated polypoid small bowel hamartoma
- 21. Adenomatous polyposis FAP – autosomal dominant condition, characterised by 500 – 2500 colonic adenomas (requires >100 for Dx) - All patients will eventually develop colorectal cancer Gardner’s syndrome – part of FAP spectrum, extracolonic manifestations include multiple skull and mandible osteomas, epidermoid cysts, soft tissue tumours, fibromatosis
- 25. Bowel Wall Thickening Small bowel - >3mm despite luminal distension Large bowel – varies. ◦ 1-2mm when lumen is well-distended. ◦ Up to 5mm when the wall is contracted, or lumen is collapsed.
- 26. Normal Bowel Wall Enhancement
- 27. Normal bowel will enhance bright in late arterial phase ; 35- 40 seconds post contrast injection. If the bowel is not thickened, this is normal enhancement. When there is bright enhancement in thickened bowel, it is sometimes difficult to differentiate between the white enhancement pattern and water-target sign pattern
- 30. White Attenuation Bright enhancement of the bowel wall is seen in vasodilatation in acute inflammatory bowel disease. Injury to the intramural vessels with interstitial leakage in shock bowel. Hypoperfusion results in increased permeability and increased enhancement. Intramural haematoma – seen in trauma case or patient with anticoagulants.
- 32. Shock Bowel - Signs of hypovolemic shock – redistribution of the blood flow. - Slit like IVC – due to hypovolemia.
- 33. Hyperenhancing Adrenal Glands Redistribution to vital organs Adrenal glands produces adrenaline in order to manage the shock.
- 34. 2) Gray PaMern Bowel wall is thick, however poor enhancement despite good bolus of contrast.
- 36. Mesenteric Ischaemia Usually affects the colon, more frequently in the splenic flexure, descending colon and sigmoid. Mostly due to low flow state like hypovolemic shock or congestive cardiac failure. ** Especially in elderly with bowel wall thickening, mesenteric ischaemia should be always considered.
- 37. Bowel Ischaemia Bowel ischaemia due to SMV thrombosis (Red arrow) Also noted the venous congestion in the mesentery (Yellow arrow)
- 38. Bowel Ischaemia Thick slab coronal reconstrucEons – May help to determine the degree of enhancement. -> Good enhancement at the jejunum -> Poor enhancement at the ileum d/t ischaemia.
- 39. Neoplasm Gray enhancement + loss of normal appearance of the bowel wall - Seen in various tumour eg. adenoCA, metastasis and GIST. ** Lymphoma and neuro- endocrine tumours like carcinoid usually show more enhancement. Case of adenocarcinoma
- 40. Case of closed loop obstruction. Notice the difference in enhancement between the normal non-distended loops (green arrow) and the distended strangulated loops (red arrow). In the center are the twisted mesenteric vessels (yellow arrow).
- 41. 3) Water Target Sign Most common type of enhancement. Caused by enhancing mucosa and muscularis propria, with the oedematous submucosa in between.
- 42. Target water sign in 35-year-old woman with H/O ulceraEve coliEs. CECT axial image of rectum shows mild wall thickening with classic target appearance and inner enhancement of mucosa (short white arrow) and outer enhancement of muscular layer (long white arrow ) surrounding low-aWenuaEon edematous submucosa (black arrow ).
- 43. Target water sign in acute Crohn’s disease.
- 44. Pseudomembranous Colitis Mostly caused by bacterium Clostridium difficile. - Bacterial overgrowth of the colon, in patient who are treated with broad-spectrum antibiotic.
- 45. Pseudomembranous Colitis This disease can be complicated by a toxic megacolon.
- 46. Water-target Sign Portal hypertension Spontaneous bacterial peritoni<s
- 48. Typhlitis Typhlitis is a necrotizing inflammation of the cecum, which is usually seen in patients with neutropenia due to acute leukemia, AIDS or aplastic anemia. There is transmural edema and ulceration, which can cause perforation.
- 50. 17% of patients with Crohn’s disease have submucosal fat in the terminal ileum and ascending colon.
- 51. • Celiac disease:- • Submucosal fat is common. • More pronounced folds in the ileum compared to the jejunum, which is the opposite of the normal finding. • The faeces may contain more fat (blue arrow).
- 52. How to deal with submucosal fat? 1. In a paTent without a history of IBD the fat-target sign likely relates to the paTent's body habitus. 2. In a paTent with belly discomfort with duodenal and proximal jejunal fat or faZy feces: suggest celiac disease. 3. In paTents with acute symptoms suggest acute and chronic IBD 4. If there is only involvement terminal ileum query Crohn's disease.
- 53. 5) Gas Pneumatosis Most concerned pattern – pneumatosis intestinalis (gas within bowel wall). Can be benign or malignant:- ◦Benign - can be an incidental finding in patients without abdominal complaints. ◦Malignant – bowel ischaemia or impending bowel perforation. Gas adjacent to the bowel wall can mimic pneumatosis – pseudopneumatosis.
- 55. Identifying gas within the mesenteric or portal veins is diagnostic of pneumatosis.
- 56. Incidental pneumatosis • Asymptomatic pneumatosis can be seen in patients with asthma and COPD
- 57. § Especially in the cecum and ascending colon, where gas bubbles can be trapped between fecal debris and the mucosa Pseudopneumatosis - gas is intraluminal and not within the wall.
- 59. String of pearls sign
- 60. String of Pearls Folds of the small bowel or valvulae conniventes will be widened, and air bubbles will be trapped in a step-ladder configuration on the ventral side. Seen in a horizontal beam radiograph of abdomen.
- 61. Bowel Wall Enhancement Pattern
- 62. Length of Bowel Involvement
- 63. Focal <5cm AdenoCA: ◦Short segment of bowel wall thickening. ◦Borders are shouldering – unlike in diverticulitis (borders are tapering).
- 64. 5-10cm Longer segment of bowel involvement, which happens in:- ◦Diverticulitis. ◦Crohn’s disease ◦Bowel ischaemia
- 65. 10-30cm Submucosal haemorrhage. ◦Mostly seen in small bowel and duodenum.
- 66. Diffuse involvement Involved entire colon: ◦Ulcerative colitis. Involved both colon and small bowels: ◦Inflammatory bowel disease (IBD). ◦Oedema. ◦SLE.
- 67. MESENTERIC ABNORMALITIES Patency of the mesenteric vessels The causes of bowel ischemia are arterial occlusion, venous thrombosis, strangulation and a low flow state. - A large segment of ileum with poor enhancement. - In the mesentery, there is edema and venous engorgement. - Findings are in keeping with ischemia. - Notice the thrombus within the superior mesenteric vein.
- 68. In the mesentery we look for:- • enlarged lymph nodes • edema and engorgement of vessels • fistula formaEon Fistula between the small bowel and the colon in a patient with Crohn's disease
- 69. Mesenteric edema Mesenteric edema in association with bowel wall thickening is seen in: • Ischemia • Inflammatory bowel disease, especially Crohn's disease - Case of closed-loop small bowel obstruction. - Notice the group of small bowel loops with a thickened wall in the right upper abdomen (yellow arrow). - The mesenteric edema (red arrow) indicates increased venous pressure due to strangulation.
- 70. Engorgement of vessels Increased venous pressure in strangulation also leads to engorgement of veins (yellow arrow). This patient has a closed loop obstruction with gray enhancement pattern of the strangulated bowel loops (red arrows). Notice the normal enhancement of small bowel proximal to the obstruction (green arrow).
- 71. LUMEN CONTENT • Fecal material in the small bowel - long standing obstruction • Blood in the lumen - gastrointestinal hemorrhage • Fat in the colonic lumen - sometimes seen in celiac disease.
- 72. Small bowel feces sign: The yellow arrow indicates a small bowel feces sign in a paDent with a small bowel obstrucDon.
- 73. Gastro-intestinal haemorrhage High-density bowel content indicating gastro-intestinal haemorrhage.
- 74. Fatty bowel content in a patient with celiac disease
- 76. Summary • Focal, irregular and asymmetrical thickening of the bowel wall suggests a malignancy. • Regular, symmetric and homogeneous wall thickening is more frequently due to benign conditions, but can also be caused by neoplasms such as well-differentiated adenocarcinoma and lymphoma. • Segmental or diffuse bowel wall thickening is usually caused by ischaemic, inflammatory or infectious conditions and the attenuation pattern is helpful in narrowing the differential diagnosis.
- 77. PNEUMOPERITONEUM
- 78. Definition Presence of free air within the peritoneal cavity. Most common cause is a perforaDon of the abdominal viscus. ◦Most commonly, a perforated ulcer. Soto JA, Lucey BC. (2009). Emergency Radiology: The Requisites. Khan AN. (2014). Pneumoperitoneum Imaging. Medscape.
- 80. Signs of Pneumoperitoneum Air under diaphragm (erect radiograph) RUQ/ Liver signs on supine abdominal radiograph: ◦ Anterior subhepatic space free air. ◦ Doges cap sign ◦ Air anterior to ventral surface of liver. Rigler’s sign Decubitus abdomen sign Falciform ligament sign Football sign Continuous diaphragm sign
- 81. Signs of Pneumoperitoneum Double bubble sign Cupola sign Lesser sac gas Triangle sign Abscess gas. Pneumoretroperitoneum Others
- 82. Anterior SubhepaXc Space Free Air Normal perihepatic fat
- 83. Doges Cap Sign Aka Morrison’s pouch free gas. - Triangular shaped - Sharp lower lateral corner - Positioned inferior to the 11th rib - Positioned superior to the right renal shadow
- 84. Air Anterior to Ventral Surface of Liver Aka lucent liver sign. - Supine ; RUQ - Uneven density in geographical shape.
- 85. Rigler’s Sign Supine Bowel wall outlined by intra- and extraluminal air (free periteoneal air).
- 86. Decubitus Abdomen Sign - Left lateral decubitus - Air fluid level White arrow -> free air between liver and abdominal wall Black arrow -> intraperitoneal free fluid.
- 87. Falciform Ligament Sign - Supine - Falciform ligament - Connects the anterior abdominal wall to the liver. - Extends inferiorly beyond the liver, becomes round ligament. - Outlined by surrounding air in case of pneumoperitoneum.
- 88. Football Sign Massive air-filled peritoneum
- 89. Continuous Diaphragm Sign - Massive pneumoperitoneum - Leh and right hemidiaphragm contrasted by the free gas appear as a conDnuous structure.
- 90. Double Bubble Sign - Subdiaphragmatic air beneath the left hemidiaphragm. - 2 collections of overlapping air - Black arrow -> Subdiaphragmatic free air - White arrow -> normal air in the fundus of stomach.
- 91. Cupola Sign Dome-like Air accumulation beneath the central tendon of the diaphragm.
- 92. Lesser Sac Air Lesser sac = A potential space, positioned posteriorly to the stomach.
- 93. The triangle Sign Small triangle of free air - Located between the large bowel and the flank.
- 94. Abscess Gas The gas bubble (white arrow) not clearly contained within the bowels - Not aligned in a linear fashion nor outline normal haustration.
- 95. Pneumoretroperitoneum Air seen surrounding the lateral border of the kidney (retroperitoneal organs). ** if the air moves in an erect/ decubitus view, it’s not in the retroperitoneum.
- 96. Urachal Sign - Vertical line between bladder and umbilicus.
- 97. Inverted “V” Sign - Free air outlines the lateral umbilical ligaments, coursing inferiorly and laterally from the umbilicus. Infants -> umbilical arteries Adults -> inferior epigastric vessels.
- 98. Leaping Dolphin Sign Air under hemidiaphragm, and diaphragmatic muscle slips visible.
- 99. BOWEL DILATATION & OBSTRUCTION: HOW TO APPROACH
- 100. Small bowel obstruction (SBO) • Conventional abdominal radiography is the preferred initial radiologic examination • If features are suggestive with bowel obstruction, further imaging with CT is appropriate.
- 101. Abdominal radiograph • Only 50-60% sensitive for small bowel obstruction • Features: Ødilated loops of small bowel proximal to the obstruction Øpredominantly central dilated loops Øthree instances of dilatation over 3 cm Øvalvulae conniventes are visible Øfluid levels if the study is erect (non-standard technique)
- 102. • obstruction (high grade mechanical obstruction) may also present with the following features: Ø a gasless abdomen: Ø the string-of-beads sign: small pockets of gas within a fluid-filled small bowel
- 103. Multiple air-fluid levels (arrows), some with a width of more than 2.5 cm. In addition, there is a differential vertical height of more than 2 cm between corresponding air-fluid levels in the same bowel loop (circled area). There is also distention of the small bowel diameter to more than 2.5 cm and a small bowel–colon diameter ratio of greater than 0.5.
- 105. • CT is more sensitive than radiographs and will demonstrate the cause in ~80% of cases. • Features on CT may include: ØDilated small bowel loops >2.5cm from outer wall to outer wall ØNormal caliber or collapsed loops distally Ø"Small bowel feces sign“ - intraluminal particulate material is identified in the dilated small bowel
- 106. Distended proximal small bowel loops (diameter >3 cm) (dotted line) and collapsed distal small bowel loops (arrows)
- 107. Small bowel feces sign.
- 108. • Closed-loop obstructions are diagnosed when a bowel loop of variable length is occluded at 2 adjacent points along its course. • May be partial or complete with characteristic features: ØRadial distribution of several dilated, fluid-filled bowel loops ØStretched of prominent mesenteric vessels converging towards the point of torsion ØU-shaped or C-shaped configuration Ø"Beak sign" at site of fusiform tapering Ø"Whirl sign" reflecting rotation of bowel loops around a fixed point
- 109. U' or 'C' shaped loops of bowel. Point of obstruction has a beak-like appearance
- 110. Closed loop obstruc;on with radial array of dilated loops. There is bowel wall thickening and mesenteric edema indica;ng ischemia
- 111. Closed loop obstruction presenting as a clump of bowel loops
- 112. • Strangulation is defined as closed-loop obstruction associated with intestinal ischaemia. • Features are non-specific and include: ØThickened and increased attenuation of the bowel wall ØHalo or "target sign“ ØPneumatosis intestinalis ØPortal venous gas ØLocalised fluid or haemorrhage in the mesentery
- 113. Strangulated SBO due to adhesions. (a) Axial CT scan shows gas in the intrahepatic portal veins (arrow). (b) Axial CT scan shows dilated small bowel loops (S) proximal to infarcted bowel segments, which demonstrate pneumatosis (arrows).
- 114. Cecal Volvulus A volvulus always extends away from the area of bowel twist. So a sigmoid volvulus can only move upwards and usually goes to the right upper quadrant. Cecal volvulus however can go almost anywhere and can even be located in the pelvis (figure).
- 115. • Cecal volvulus is due to the cecum twisting around the ascending colon thus leading to small bowel obstruction. • A long narrow based mesentery predisposes to volvulus. • An incomplete midgut rotation is a predisposing factor. • Cecal volvulus accounts for about 25% of cases of colonic volvulus.
- 116. - The x-rays show a typical cecal volvulus. - Notice that the dilated bowel points toward the area of twist, which is the area where you expect the cecum to be located.
- 117. • On the left a typical cecal volvulus is seen. • We can see the beak-like transition zone located in the right lower quadrant indicating that this is a cecal volvulus. • The dilated cecum is located in the left upper quadrant. • Also notice the collapsed descending colon posterior to the dilated cecum (curved arrow) Dilated cecal volvulus (C) shiCing away from the area of bowel twist (arrow)
- 118. Sigmoid Volvulus • We can see the distended sigmoid extending from the pelvis way up into the right upper quadrant. • The key finding is the dilatation of the proximal colon. • The dilated loop seen on the left side is the dilated transverse colon.
- 119. AP supine and erect radiograph of the abdomen demonstrates the characteristic coffee bean sign in sigmoid volvulus. Notice that the dilated loops point towards the sigmoid area.
- 120. At CT we can nicely appreciate the area of the twist with the sigmoid extending up to the diaphragm. The sigmoid is the commonest site of colonic volvulus. It accounts for 75% of large bowel obstruction
- 121. The transition point (red arrows).
- 122. demonstrates the twist at the transition point (arrow). Sigmoid volvulus
- 123. • Is the Small Bowel Obstructed? • How Severe Is the Obstruction? can be determined by the degree of distal collapse, proximal bowel dilatation, and the presence of the “small bowel feces” sign • Where Is the Transition Point? The transition point is determined by identifying a caliber change between the dilated proximal and collapsed distal small bowel loops • What Is the Cause of the Obstruction? • Is the obstruction Simple or Complicated?
- 124. GRACIAS