Approach to intestinal obstructions.pptx

approach to acute causes of intestinal obstruction

1. Approach to intestinal obstruction Moderator: Dr Umamaheshwari mam Presenter : Dr vasanth kumar L

2. INTESTINAL OBSTRUCTION A mechanical or functional obstruction of the intestines, preventing the normal transit of the products of digestion.

3. Clinical feature pain: colicky in nature & usually the first symptom. abdominal distention : more obvious in low intestinal obstruction &large bowel obstruction but less in high intestinal obstruction. absolute constipation- failure to pass feces & flatus. vomiting: early in high obstruction but late or even absent in low obstruction. O/E: -dehydrated if large amount of vomiting had occurred. -tachycardia. -raise in temperature suggest strangulation.

4. Small bowel obstruction Aim of imaging is to find : Is the small bowel obstructed? How severe is the obstruction? where is it located? what is its cause? strangulation present?

5. Abdominal radiograph Supine or prone 1. Dilated gas or fluid-filled small bowel (>3 cm) 2. Dilated stomach 3. Small bowel dilated out of proportion to colon 4. Stretch sign 5. Absence of rectal gas 6. Gasless abdomen 7. Pseudotumor sign Upright or left lateral decubitus 1. Multiple air fluid levels 2. Air fluid levels longer than 2.5 cm 3. Air fluid levels in same loop of small bowel of unequal heights 4. String of beads sign

6. supine upright

7. String of pearls sign

8. enteroclysis

9. Sonography Peristalsis of the dilated segment is increased, as shown by the to-and-fro or whirling motion of the bowel contents Level of the obstruction is determined by means of the location of the bowel loops and the pattern of the valvulae conniventes . Cause of the SBO may be determined by examining the area of transition from the dilated to normal bowel The severity of the obstruction can also be assessed. The presence of free fluid between dilated small bowel loops, aperistalsis , and wall thickening (>3 mm) in a fluid-filled distended bowel segment suggests bowel ischaemia /perforation .

10. USG

11. Findings at Multidetector CT CT criteria for SBO are the presence of dilated small bowel loops (diameter >2.5 cm from outer wall to outer wall) proximally to normal-caliber or collapsed loops distally

12. Severity of obstruction A low-grade partial SBO is considered present when there is sufficient flow of contrast material through the point of obstruction High-grade partial SBO is diagnosed when there is some stasis and delay in the passage of the contrast medium. Can be also determined by the degree of distal collapse, proximal bowel dilatation, and the presence of the “small bowel feces” sign. In a high-grade obstruction, there is a 50% difference in caliber between the proximal dilated bowel and the distal collapsed bowel.

13. Small bowel feces sign

14. Transition Point

15. Cause of the Obstruction A rule of thumb never to forget is that the answer is almost always in the transition point . Most intrinsic bowel lesions are seen at the transition point and manifest as localized mural thickening. Most extrinsic causes are seen adjacent to the transition point and usually have associated extraintestinal manifestations . Most intraluminal causes manifest as endoluminal “foreign objects” with imaging characteristics different from those of the remaining enteric content.

16. Intrinsic Causes of SBO

17. Crohn Disease SBO in Crohn disease can be a manifestation of three clinical situations. It can result from the acute presentation of the disease characterized by bowel luminal narrowing secondary to the transmural acute inflammatory process. It can be a manifestation of long-standing disease, which usually results in cicatricial stenosis of affected segments. Finally, it can be secondary to adhesions, incisional hernias, exacerbation of the inflammatory condition, or postoperative strictures in patients who have undergone previous intestinal surgery

18. Neoplasia Small bowel involvement by metastatic cancer is more common than involvement by primary neoplasms Intrinsic small bowel neoplasms constitute less than 2% of gastrointestinal malignancies. When a small bowel adenocarcinoma manifests as SBO, it is usually at an advanced state and shows pronounced, asymmetric, and irregular mural thickening at the transition point. Metastasis more frequent in the form of peritoneal carcinomatosis , which is suggested when extrinsic serosal disease involving the small bowel wall is seen in association with a transition point .

19. Intussusception Accounting for less than 5% of SBO. Only lead-point intussusceptions secondary to neoplasms, adhesions, or foreign bodies are associated with SBO. Transient intussusceptions are not associated with this condition. At CT, the presence of a bowel-within-bowel configuration with or without mesenteric fat and mesenteric vessels is pathognomonic for int.ussusception , A leading mass as the cause of the intussusception can be identified.

20. Radiation Enteritis Radiation enteritis causes obstruction in the late phase 1 year after radiation therapy, usually to the pelvis. SBO primarily by producing adhesive and fibrotic changes in the mesentery. changes produced within the bowel include luminal narrowing and dysmotility induced by radiation serositis. CT shows narrowing of the lumen secondary to mural thickening, an angular bowel wall due to adhesions, and retraction of the mesentery .

21. Hematomas Intramural small bowel hematoma may occur secondary to anticoagulant therapy, iatrogenic intervention, or trauma. usually due to luminal narrowing .. nonenhanced CT should be performed, as it will show a spontaneously hyperattenuating clot

22. Vascular Causes Occlusion or stenosis of the mesenteric arterial or venous vascular supply to the bowel usually produces bowel ischemia, which subsequently causes wall thickening, resulting in SBO. CT shows thrombosis or occlusion of the mesenteric vessels and also thickening of the bowel wall in the affected loops with noncircumferential or asymmetric wall enhancement. In advanced cases, a bowel infarct may be present, which manifests at CT as pneumatosis and air in the portal venous system

23. Extrinsic Causes of SBO

24. Adhesions main cause of SBO, ranging from 50%–80% of all cases. Mainly post-operative , but can also occur secondary to peritonitis. Diagnosis : abrupt change in the caliber of the bowel is seen without any associated mass lesion, significant inflammation, or bowel wall thickening at the transition point. Combined with history of abdominal surgery and associated kinking and tethering of the adjacent nonobstructed bowel usually suggests the diagnosis .

25. Hernias second most common cause of SBO, responsible for 10% of cases. s. They are broadly classified as external or internal. An external hernia results from a defect in the abdominal and pelvic wall at sites of congenital weakness or previous surgery . The less common internal hernia occurs when there is protrusion of the viscera through the peritoneum or mesentery and into a compartment within the abdominal cavity.

26. Endometriosis Endometrial implants are typically located on the antimesenteric edge of the bowel , and their appearance is variable. The typical appearance of intestinal endometriosis is a solid nodule with positive enhancement contiguous with or penetrating the thickened bowel wall. When the endometriotic lesion infiltrates the submucosa, it typically appears as a hypoattenuating layer between the muscularis and the mucosa

27. Intraluminal Causes of SBO

28. Gallstone Ileus Gallstone ileus is a rare complication of recurrent cholecystitis, caused by migration of a large gallstone through a biliary intestinal fistula with subsequent impaction in the small bowel. CT findings are pathognomonic, corresponding to the radiographic triad of pneumobilia , ectopic gallstone, and SBO

29. Distal Intestinal Obstruction Syndrome. occurs in older children and adults with cystic fibrosis . The obstruction is secondary to impaction of thick stool , which is probably related to inadequately controlled intestinal absorption secondary to pancreatic insufficiency. At CT, the findings consist of SBO with feculent filling defects in the small bowel.

30. SBO Simple or Complicated SBO can be divided into two types: simple obstructions and closed-loop obstructions. Simple obstruction of the bowel is considered when the bowel is occluded at one or several points along its course Closed-loop obstructions are diagnosed when a bowel loop of variable length is occluded at two adjacent points along its course.

31. closed-loop obstruction CT: Axial scans reveal a characteristic fixed radial distribution of several dilated , usually fluid-filled bowel loops with stretched and prominent mesenteric vessels converging toward the point of torsion. The configuration can be U-shaped or C-shaped , depending on the orientation of the closed loop. narrow pedicle can be formed, leading to torsion of the loops and producing a small bowel volvulus . At CT, a “beak sign” is seen at the site of the torsion as a fusiform tapering, and occasionally a “ whirl sign ” can be seen, reflecting rotation of the bowel loops around the fixed point of obstruction

32. Strangulation Defined as a closed-loop obstruction associated with intestinal ischemia . Specific finding: lack of wall enhancement . asymmetric enhancement or even delayed enhancement may also be found. Localized fluid and hemorrhage in the mesentery can also be seen. Non specific : thickening and increased attenuation of the affected bowel wall, a halo or “ target sign ,” pneumatosis intestinalis, and gas in the portal vein.

33. Large bowel obstruction LBO is four to five times less frequent than SBO emergency surgery or colonoscopy is usually required to relieve the obstruction Colonic obstruction is most often seen in elderly individuals

34. Large bowel obstruction-CAUSES

35. Clinical presentation The signs and symptoms of LBO are often insidious in contrast to the abrupt onset of symptoms seen in most SBOs; Presentation is typically with abdominal pain, distension and failure of passage of flatus and stool Eventually signs of peritonism, sepsis and shock develop, when perforation occurs.   LBO caused by obstruction in the left colon manifests earlier than that caused by obstruction in the right colon because the lumen of the sigmoid and descending colon is smaller and the stool is more inspissated in the distal colon

36. Radiography Normal colonic caliber ranges from 3 to 8 cm, with the largest diameter in the cecum; colon is dilated when it is greater than 6 cm and the cecum when larger than 9 cm in diameter. Air-fluid levels are suggest that the cause is more acute - colonic fluid has not been present long enough to be absorbed In advanced cases one may see the stigmata of an  ischemic colon small bowel dilatation , depends on duration of obstruction Incompetence of IC valve

37. CT CT is the imaging modality of choice for the diagnosis of the cause of LBO CT can be used to diagnose intraluminal,mural , and extramural causes of LBO detection of inflammation and bowel ischemia

38. Colorectal carcinoma Common sites-sigmoid colon and splenic flexure . The most common site of perforation[ 3%–8%] in LBO is not at the site of the tumor but at the cecum Barium enema  seen as filling defects appear as exophytic or sessile masses may be circumferential - apple co re sign CT Asymmetric and short-segment colonic wall thickening or an enhancing soft-tissue mass centered in the colon that narrows the colonic lumen Pericolonic lymph nodes

39. Acute colonic volvulus If the twist is greater than 360 °, the volvulus is unlikely to resolve without intervention . Sigmoid volvulus is three to four times more common than cecal volvulus volvulus of the transverse colon and splenic flexure is very rare

40. Sigmoid volvulus

41.   Frimann dahl's sign “ northern exposure” sign

42. Caecal volvulus

43. Diverticulitis A complication of diverticulosis with elderly patients being most at risk Can present with LBO due to bowel wall edema and pericolonic inflammation Obstruction occurs in the setting of multiple episodes of diverticulitis, which causes narrowing and stricture formation

44. Imaging features CT is the modality of choice for the diagnosis and staging of diverticulitis. Appearances include:  pericolic stranding , often disproportionately prominent compared to the amount of bowel wall thickening   segmental thickening of the bowel wall with hyperemia , which is typically longer segment (>10 cm) than malignant lesions enhancement of the colonic wall  usually has inner and outer high-attenuation layers, with a thick middle layer of low attenuation

45. diverticular perforation   extravasation of air and fluid into the pelvis and peritoneal cavity abscess formation (seen in up to 30% of cases) may contain fluid, gas or both fistula formation gas in the bladder direct visualisation of fistulous tract

46. Colocolonic intussusception .

47. LBO due to hernia

48. LBO due to Crohn colitis

49. Adynamic obstruction Paralytic ileus - absence of neural activity Pseudo obstruction - imbalance of neural activity -sympathetic overactivity -parasympathetic suppression

50. Paralytic ileus Causes -post operative -abdominal sepsis - metabolic;uremia and hypokalemia -CVA/spinal injury characterized by diffuse small- and large bowel dilatation without a transition point

51. Acute colonic pseudo obstruction (ACPO /Ogilvie syndrome) secondary to interruption of sympathetic innervation of the colon ACPO is most common in male patients over 60 years of age, and most are already hospitalized with a severe illness Is a disorder of bowel which symptomatically, clinically and radiologically may mimic intestinal obstruction.

52. Pseudo-obstruction can present with a sudden painless enlargement of the proximal colon accompanied by distension. Bowel sounds are normal or high-pitched, but should not be absent .  Despite the absence of mechanical obstruction, patients can nonetheless go on to bowel necrosis and perforation (especially if dilatation is severe) which in turn can go on to become generalized peritonitis.

53. It may be acute and self-limiting and associated with inflammatory, infectious, traumatic, metabolic conditions or certain drugs A large proportion of patients - idiopathic intestinal pseudo-obstruction Large quantity of bowel gas is usually present and there may be gastric, small- or large-bowel distension with associated fluid levels just as great as in true obstruction. Imaging can be performed to exclude true organic obstruction - without evidence of an abrupt transition point or mechanically obstructing lesion.  It is important to note, however, that a gradual transition point is frequently present , usually at or near the splenic flexure

54. Summary

55. REFERENCES Review of Small-Bowel Obstruction: The Diagnosis and When to Worry- 338 radiology.rsna.org, Radiology: Volume 275: Number 2—May 2015 Small bowel obstruction:what to look for- pubs.rsna.org/ doi /full/10.1148/rg.292085514 Large-Bowel Obstruction in the Adult:Classic Radiographic and CT Findings, Etiology , and Mimics- RSNA,Radiology : Volume 275: Number3— june 2015 Textbook of gastrointestinal radiology – by GORE and LEVINE