Abdominal X-ray Radiological Signs

1. Abdominal X-ray Radiological Signs Suzanne O’Hagan

2. Lightbulb moment a moment of sudden inspiration, revelation, or recognition

3. Approach to AXR • Bowel gas pattern • Extraluminal air • Soft tissue masses • Calcifications

4. Normal AXR Gas in stomach Liver Splenic flexure T12 11th rib Psoas margin Left kidney Hepatic flexure Transverse colon Iliac crest Gas in sigmoid Sacrum Gas in caecum SI joint Bladder Femoral head

5. Gas pattern What is normal? • Stomach • Almost always air in stomach • Small bowel • Usually small amount of air in 2 or 3 loops • Large bowel • Almost always air in rectum and sigmoid • Varying amount of gas in rest of large bowel

6. Normal fluid levels • Stomach • Always (upright, decub) • Small bowel • Two or three levels acceptable (upright, decub) • Large bowel • None normally (functions to remove fluid)

7. Large vs small bowel • Large bowel • Peripheral (except RUQ occupied by liver) • Haustral markings don’t extend from wall to wall • Small bowel • Central • Valvulae conniventes extend across lumen and are spaced closer together

8. Radiographic principles Series of films for acute abdomen • Obstruction series/ Acute abdominal series/ Complete abdominal series • Supine (almost always) • Upright or left decubitus (almost always) • Prone or lateral rectum (variable) • Chest, upright or supine (variable)

9. Acute abdominal seriesWhat to look for Substitutes: Prone Lateral rectum Upright Left lateral decub Upright chest Supine chest

10. Obtaining views • Supine • Patient on back, x ray beam directed vertically downward, casette posterior, x-ray tube anterior (AP) • Prone • Patient on abdomen, x-ray beam directed vertically downward, cassette anterior, x-ray tube posterior (PA) • Upright • Patient stands or sits, x-ray beam directed horizontally, cassette posterior, x-ray tube anterior (AP) • Upright chest • Patient stands or sits, horizontal x-ray beam, cassette anterior, x-ray tube posterior (PA) 1900s X-Ray-based fluoroscopy machine in which radiation is shot directly through the patient and into the doctor’s face.

11. Abnormal Gas Patterns • Functional ileus • One or more bowel loops become aperistaltic usually due to local irritation or inflammation • Localised “sentinel loops” (one or two loops) • Generalised (all loops of large and small bowel) • Mechanical obstruction • Intraluminal or extraluminal • Small bowel obstruction • Large bowel obstruction

12. 3, 6, 9 RULE Maximum Normal Diameter of bowel Small bowel 3cm Large bowel 6cm Caecum 9cm

13. LocalisedileusKey features • One or two persistently dilated loops of small or large bowel (multiple views) • Often air-fluid levels in sentinel loops • Local irritation, ileus in same anatomical region as pathology • Gas in rectum or sigmoid • May resemble early SBO

14. Causes of Localised Ileusby location

15. Colon cut off sign Abrupt cutoff of colonic gas column at the splenic flexure (arrow). The colon is usually decompressed beyond this point. Explanation: Inflammatory exudate in acute pancreatitis extends into the phrenicocolic ligament via lateral attachment of the transverse mesocolon Infiltration of the phrenicocolic ligament results in functional spasm and/or mechanical narrowing of the splenic flexure at the level where the colon returns to the retroperitoneum.

16. GeneralisedileusKey features • Entire bowel aperistaltic/hypoperistaltic • Dilated small bowel and large bowel to rectum (with LBO no gas in rectum/sigmoid) • Long air-fluid levels * almost always

17. Generalised adynamic ileus The large and small bowel are extensively airfilled but not dilated. The large and small bowel "look the same".

18. Mechanical SBO • Dilated small bowel • Fighting loops (visible loops, lying transversely, with air-fluid levels at different levels) • Little gas in colon, especially rectum

19. SBO Erect SBO Supine Air fluid levels

20. Causes of Mechanical SBO * May be visible on AXR

21. Step ladder appearance • Loops arrange themselves from left upper to right lower quadrant in distal SBO

22. Coil spring sign

23. String of pearls sign Considered diagnostic of obstruction (as opposed to ileus) and is caused by small bubbles of air trapped in the valvulae of the small bowel.

24. Stretch/slit sign Slit of air caught in a valvulae, characteristic of SBO

25. Closed loop obstruction • Two points of same loop of bowel obstructed at a single location • Forms a C or a U shape • Term applies to small bowel, usually caused by adhesions • Large bowel, called a volvulus

26. Crescent Sign Caused by: LUQ Soft tissue mass OR Head of intussusception in distal transverse colon

27. Double Bubble Sign Duodenal Atresia

28. Mechanical LBO • Colon dilates from point of obstruction backwards • Little/no air fluid levels (colon reabsorbs water) • Little or no air in rectum/sigmoid

29. Large bowel obstruction Bowel loops tend not to overlap therefore possible to identify site of obstruction Little or no gas in small bowel if ileocaecal valve remains competent* * If incompetent, large bowel decompresses into small bowel, may look like SBO

30. Causes of Mechanical LBO

31. Note on volvulus • Sigmoid colon has its own mesentry therefore prone to twisting • Caecum usually retroperitoneal and not prone to twisting; 20% people have defect in peritoneum that covers the caecum resulting in a mobile caecum

32. Volvulus A volvulus always extends away from the area of twist.
Sigmoid volvulus can only move upwards and usually goes to the right upper quadrant. Caecal volvulus can go almost anywhere.

33. Coffee Bean SignSigmoid volvulus Massively dilated sigmoid loop

34. Hernia Lateral decubitus of value The advantage is that there may be a greater chance of air entering the herniated bowel because it is the least dependent part of the bowel in the supine position.

35. Apple core sign • Radiologic manifestation of a focal stricture of the bowel usually at contrast material enema examination. The stricture demonstrates shouldered margins and resembles the core of an apple that has been partially eaten. The most common cause is an annular carcinoma of the colon.

36. Thumbprinting The distance between loops of bowel is increased due to thickening of the bowel wall. The haustral folds are very thick, leading to a sign known as 'thumbprinting.'

37. Lead pipe colon • Shortening of colon secondary to fibrosis • Loss of haustration • Ulcerative colitis

38. Extraluminal air • TYPES • Pneumoperitoneum/free air/intraperitoneal air • Retroperintonealair • Air in the bowel wall (pneumatosisintestinalis) • Air in the biliary system (pneumobilia)

39. Upright film best • The patient should be positioned sitting upright for 10-20 minutes prior to acquiring the erect chest X-ray image. • This allows any free intra-abdominal gas to rise up, forming a crescent beneath the diaphragm. It is said that as little as 1ml of gas can be detected in this way.

40. Free AirCauses • Rupture of a hollow viscus • Perforated peptic ulcer • Trauma • Perforated diverticulitis (usually seals off) • Perforated carcinoma • Post-op 5-7 days normal, should get less with successive studies *NOT ruptured appendix (seals off)

41. Signs of free air • Crescent sign • Chilaiditis sign • Riglers (and False Rigler’s) • Football sign • Falciform ligament sign • Triangle sign • Cupola sign • Lesser sac sign

42. Crescent Sign II Free air under the diaphragm Best demonstrated on upright chest x rays or left lat decub Easier to see under right diaphragm

43. Chilaiditis sign • May mimic air under the diaphragm • Look for haustral folds • Get left lat decub to confirm In patients who have cirrhosis or flattened diaphragms due to lung hyperinflation, a void is created within the upper abdomen above the liver. This space may be filled by bowel. If this bowel is air filled then it may mimic free gas.

44. Rigler’s Sign Bowel wall visualised on both sides due to intra and extraluminal air Usually large amounts of free air May be confused with overlapping loops of bowel, confirm with upright view

45. False Rigler’s Sign • The Rigler sign can sometimes be simulated by contiguous loops of bowel, whereby intraluminal air in one loop of bowel may appear to outline the wall of an adjacent loop, which results in a misdiagnosis of free air. • Measure distance of interface if unsure

46. Football SIgn Seen with massive pneumoperitoneum Most often in children with necrotising enterocolitis In supine position air collects anterior to abdominal viscera Paediatric Adult

47. Falciform ligament sign Normally invisible. Supine film, free air rises over anterior surface of liver

48. Other patterns of air around liver Doge’s Cap Sign

49. Inverted V sign • On the supine radiograph, an inverted "V" may be seen over the pelvis in a patient with pneumoperitoneum. • While in infants this is produced by the umbilical arteries, in adults it appears to be created by the inferior epigastric vessels

50. Continuous diaphragm sign Sufficient free air, left and right hemi- diaphragms appear continous