Imaging in acute nontrumatic solid organs injuries

2. Imaging in acute nontrumatic solid organs injuries A. Norouzi MD

3. The 'acute abdomen' is a clinical condition characterized by severe abdominal pain, requiring the clinician to make an urgent therapeutic decision. • This may be challenging, because the differential diagnosis of an acute abdomen includes a wide spectrum of disorders, ranging from life-threatening diseases to benign self-limiting conditions (Table 1).

4. Table 1. Common causes of acute abdomen from life-threatening to self-limiting.

5. Indicated management may vary from emergency surgery to reassurance of the patient and misdiagnosis may easily result in delayed necessary treatment or unnecessary surgery. • Sonography and CT enable an accurate and rapid triage of patients with an acute abdomen.

6. Radiological strategy

7. Before you perform an examination, obtain relevant information from the referring clinician. • Don't let the clinician simply 'order' a sonogram or CT, but discuss the patient's age and posture, laboratory results and the number one clinical diagnosis and differential diagnosis. • Based on that information and your own degree of confidence with the modalities decide for yourself whether to perform sonography or CT.

8. Sonography has the advantage of close patient contact, enabling assessment of the spot of maximum tenderness and the severity of illness without ionizing radiation. • In general the diagnostic accuracy of CT is higher than sonography. • In patients with inconclusive US-results, CT can serve as an adjunct to sonography, and vice versa.

9. Clinics, laboratory, and plain abdominal film • The clinical presentation of patients with an acute abdomen is often nonspecific. • Both surgical and nonsurgical diseases may present with a similar clinical history and symptoms. • Laboratory findings (leucocyte count, erythrocyte sedimentation rate, CRP) are equally nonconclusive. • Findings may be normal in patients who need emergency surgery (such as appendicitis) and may be abnormal in patients without a surgical disease (like salpingitis).

10. A plain abdominal film has a limited value in the evaluation of abdominal pain. • A normal film does not exclude an ileus or other pathology and may falsely reassure the clinician. • An ileus may not be appreciated on a plain abdominal film if bowel loops are filled with fluid only without intraluminal air (figure). • Alternatively if a plain abdominal film does indicate an ileus then sonography or CT are usually needed to identify its cause.

11. Thus, a plain abdominal film is seldomly useful, with the exception of detection of kidney stones, bowel obstruction or a pneumoperitoneum. • For all other indications use sonography or CT.

13. LEFT: Plain abdominal film in a patient with an acute abdomen, showing no abnormalities. RIGHT: Subsequent CT shows distended small bowel loops (arrowheads) that are not seen on plain abdominal film because they are filled with fluid only and do not contain intraluminal air.

14. Confirm or exclude the most common disease Always remember : Commonest are the commonest

15. Many disorders may cause an acute abdomen, but fortunately only a few of these are common and clinically important. • Focus on confirming or excluding these frequent disorders:

16. Screen for general signs of pathology

17. After excluding these frequent disorders, search for signs of any other pathology, by systematically screening the whole abdomen. • Look for inflamed fat, bowel wall thickening, ileus, ascites and free air.

18. Inflamed fat Inflamed fat at sonography. Extended-view of the ventral abdomen depicting an area of hyperechoicnoncompressible inflamed fat in the omentum (red arrows). Compare this to the echogenicity of normal abdominal or subcutaneous fat (green arrows). This patient had an omental infarction. • Inflamed fat is hyperechoic, space occupying and noncompressible at sonography.

19. Same patient as above. Unenhanced CT depicts an area of fatty tissue with slightly increased density (arrowheads), in the right-upper quadrant. Compare this to normal low-density subcutaneous fat. Diagnosis: omental infarction. • Inflamed fat is shown as fat-stranding at CT. Inflamed fat usefully points out where and what the problem is. • As a rule, the organ or structure in the centre or nearest to the inflamed fat is the cause of the inflammation.

20. Bowel wall thickening • Thickening of bowel wall indicates inflammation or tumor, and has an extensive differential diagnosis. • Thickening of small bowel loops usually indicates regional inflammation, as small bowel tumors (carcinoid, lymphoma, GIST) are relatively infrequent. • In patients with local colonic wall thickening a carcinoma is a prime concern.

21. Diffuse thickening of bowel wall in a patient with colitis.

22. Ileus • Pathologic distention of bowel loops may be caused by obstruction or paralysis. • Firstly determine which parts of the gut are affected: small bowel, large bowel, or both. • Look for normal nondistended bowel loops, which, if present, strongly suggest an obstructive cause for the ileus.

23. Obstructive ileus. CT depicts distended small bowel loops, but part of the small bowel and the whole colon is nondistended. Therefore this must be an obstructive small bowel ileus, and in this case its cause can easily be identified: intussusception (arrowhead).

24. Alternatively, an ileus without any normal bowel loops strongly suggests a paralytic cause. This is usually a response to general peritonitis, which may have many possible causes of the inflammation.

25. Ascites • Asymptomatic volunteers do not have a detectable amount of free intraperitoneal fluid, with the exception of an incidental drop of fluid in Douglas in fertile women. • The presence of ascites is a nonspecific sign of abdominal pathology, indicating that 'something is wrong'. • You may want to perform a US-guided diagnostic puncture of the ascites, in order to investigate whether it is sterile reactive fluid, pus, blood, urine, or bile.

26. Clinically appendicitis. US only showed a little bit of ascites. A diagnostic puncture (arrow marks needletip) revealed blood. In a woman this finding is very suspicious of an EP.

27. Free air • The presence of free intraperitoneal air is proof of bowel perforation, and indicates a surgical emergency. • A pneumoperitoneum has only two frequent causes: • Perforation of a gastric ulcer • Perforation of colonic diverticulitis • Free air is usually not seen in perforated appendicitis. • Always examine the images in lung setting for better detection of free intraabdominal air (figure).

28. Intraperitoneal air in a patient suspected of having appendicitis. Air better seen on images with lung setting on the right.

29. Cholecystitis

30. Cholecystitis occurs when a calculus obstructs the cystic duct. The trapped bile causes inflammation of the gallbladder wall.  • As gallstones are often occult on CT, sonography is the preferred imaging method for the evaluation of cholecystitis, also allowing assesment of the compressiblity of the gallbladder.  • The diagnosis of a hydropic gall bladder is solely made on the non-compressability of the gall bladder. Do not rely on measurements. Some gall bladders happen to be small and others are large.

31. The imaging appearance of cholecystis consists of an enlarged hydropic (meaning non-compressible) gallbladder with a thickened wall in the region of maximum tenderness (the so-called 'Murphy sign')

32. Longitudinal and transverse US show thickened gallbladder wall. The gallbladder is noncompressible ('hydropic') and causes an impression in the anterior abdominal wall (arrowheads).

33. The inflamed gallbladder usually contains stones or sludge, whereas the obstructing calculus itself may or may not be identified because it is located deep within the gall bladder neck or cystic duct. • The gallbladder may be surrounded by inflamed fat, but on sonography this frequently is not seen, while CT sometimes does show fat-stranding. 

34. Potential pitfalls are pancreatitis, hepatitis or right-sided heart failure, which all may lead to thickening of the gallbladder wall without cholecystitis. • Therefore be certain that hydropic obstruction of the gallbladder is present before assigning the diagnosis of cholecystitis.

35. Gallbladder Wall Thickening

36. Thickening of the gallbladder wall is a relatively frequent finding at diagnostic imaging studies. • Historically, a thick-walled gallbladder has been regarded as proof of primary gallbladder disease, and it is a well-known hallmark feature of acute cholecystitis. • The finding itself, however, is non-specific and can be found in a wide range of gallbladder diseases and extracholecystic pathological conditions.

37. Sonography, CT and MRI all allow direct visualization of the normal and thickened gallbladder wall. • Traditionally, sonography is used as the initial imaging technique for evaluating patients with suspected gallbladder disease, because of its high sensitivity in the detection of gallbladder stones, its real-time character, speed and portability

38. However, CT has become popular for evaluating the acute abdomen and often is the first modality to detect gallbladder wall thickening, or it may be used as an adjunct to an inconclusive sonography or for staging of disease. • The potential value of MRI in the evaluation of gallbladder pathology has been shown, but it still plays little role.

39. LEFT: US of a normal gallbladder after an overnight fast shows the wall as a pencil-thin echogenic line.RIGHT: US in the postprandial state shows pseudothickening of the gallbladder • The normal gallbladder wall appears as a pencil-thin echogenic line at sonography. • The thickness of the gallbladder wall depends on the degree of gallbladder distention and pseudothickening can occur in the postprandial state.

40. Contrast-enhanced CT shows the normal gallbladder wall as a thin rim of enhancing soft-tissue • The normal gallbladder wall is usually perceptible at CT as a thin rim of soft-tissue density that enhances after contrast injection.

41. Thickened gallbladder wall • Thickening of the gallbladder wall is a relatively frequent finding at diagnostic imaging studies. • A thickened gallbladder wall measures more than 3 mm, typically has a layered appearance at sonography, and at CT frequently contains a hypodense layer of subserosaloedema that mimics pericholecystic fluid.

42. LEFT: US in a 59-year-old woman with acute cholecystitis shows the layered appearance of a thickened gallbladder wall, with a hypoechoic region between echogenic linesRIGHT: At contrast-enhanced CT the thick-walled gallbladder contains a hypodense outer layer (arrow) due to subserosaloedema

43. Differential diagnosis of gallbladder wall thickening • The differential diagnosis of gallbladder wall thickening is listed on the table 2. • Diffuse gallbladder wall thickening may produce a diagnostic problem, as it occurs in symptomatic and asymptomatic patients, and in patients with and without an indication for a cholecystectomy.

45. Diffuse thickening of the gallbladder wall may occur in patients who do not have a primary gallbladder disease, but in whom the gallbladder is secondarily involved in an extrinsic pathological condition. • In these patients a cholecystectomy is unwarranted, and gallbladder abnormalities will usually return to normal after correction of its extrinsic cause.

46. What is your diagnosis 43-year-old woman with acute calculouscholecystitis.

47. What is your diagnosis Chronic cholecystitis

48. What is your diagnosis Xanthogranulomatouscholecystitis. LEFT: US shows marked wall thickening with intramural hypoechoic nodules (arrowheads), and an intraluminal stone (arrow). RIGHT: Contrast-enhanced CT shows a deformed and thickened gallbladder wall containing hypoattenuating nodules

49. What is your diagnosis Porcelain gallbladder.

50. What is your diagnosis LEFT: Gallbladder carcinoma. US shows marked generalized wall thickening (arrowheads), replacing the gallbladder lumen. Multiple gallbladder stones (arrow) indicate the probable location of the filled lumen. RIGHT: Contrast-enhanced CT depicts a thick-walled gallbladder (arrowhead), with local infiltration of the mass in the adjacent liver (arrow).