1. PLAIN ABDOMEN AND RETROPERITONEUM
NITTHIDA BILLATEH, M.D.
RADIOLOGY DEPARTMENT

2. STANDARD PLAIN FILMS Supine Upright AP view
Alternative lateral decubitus view

3. Acute Abdomen series Abdominal supine position
Gas pattern, calcification, soft tissue masses
Abdominal upright position
Free air, air-fluid level
Chest upright position
Free air
Pneumonia at lung base
Pleural effusion

4. Normal plain abdomen

5. Plain abdomen

6. Plain abdomen
Supine
Upright

7. How to look at a plain abdominal film
Look for any dilated loops of bowel and try to decide which portions of the bowel are affected.
Look for any gas outside the lumen of the bowel.
Look for ascites and any soft tissue mass in the abdomen and pelvis.
If there are any calcifications, try to locate exactly where they life.
Assess the size of the liver and spleen.

8. Gas abnormalities

9. Normal bowel gas pattern
The radiographic evaluation of intestinal gas
Identification of the bowel segment containing the gas
Assessment of the caliber of segment
Assessment of most distal point of passage of the gas
Evaluation of the mucosa outlined by the gas

10. Normal bowel gas in the supine film
In the antrum and body of stomach
Transverse colon, may be seen immediately inferior to the stomach
Ascending and descending colon-lateral margin of peritoneal cavity
Sigmoid-inferior aspect of abdomen
Rectal gas, midline position in pelvis and extend to pubic symphysis.

11. Normal bowel gas in the supine film
Stomach
Almost always contains air or fluid
Supine position: gas in stomach rises to the anteriorly located antrum while fluid gravitates to the fundus
Upright: gas-filled fundus
Valuable landmark for identifying space-occupying lesions in surrounding structures.

12. Normal bowel gas in the supine film
Small intestine:
central portion of the abdomen, smaller caliber than colon
Plicae circulares or valvulae conniventis: 1-2 mm wide, interval 1 mm
Less than 3 cm in diameter
Colon:
Peripheral portion of abdomen
Haustra of the colon: 2-3 mm wide, interval 1 cm
Less than 5 cm in diameter

14. Abnormal bowel gas pattern
Gastric outlet obstruction
Adynamic ileus
Small bowel obstruction
Colonic obstruction
Closed loop obstruction
Volvulus

15. Gastric outlet obstructuion

16. Gastric outlet obstructuion
Antrum and pyloric region – usual site
Most common cause: Peptic ulcer disease in distal stomach/duodenum with scarring
Other cause: scirrhous gastric carcinoma, scarring from ingestion caustic substance

17. Gastric outlet obstruction
Plain film depend on
Degree of distention of stomach by air or fluid
Duration of obstruction
Position of patient
Frequency of emesis
Massively dilated fluid-filled stomach may mimic hepatomegaly or ascites
Displace transverse colon inferiorly, characteristic contour
Small amount of air: upright or right lateral decubitus film-confirm the gastric location of the fluid

18. Gastric outlet obstruction

19. Gastric outlet obstructuion
Dilated stomch
Dilated fluid-filled stomach
Contrast cannot pass through distal passage
PLAIN ABDOMEN SUPINE
UPPER GI STUDY

20. Adynamic Ileus

21. Adynamic Ileus
Dilated bowel, usually small intestine, absence of mechanical obstruction
Absent or decreased intestinal peristalsis, which allows swallowed air to accumulate in dilated small intestine
The present of colonic gas may be helpful in distinquishing from a mechanical obstruction

22. Adynamic Ileus
Localized ileus
Generalized ileus

23. Localized Ileus
One or two persistently dilated loops of large or small bowel (sentinel loop)
Gas in rectum or sigmoid
Causes: acute appendicitis, acute cholecystitis, acute pancreatitis
Pitfall:
May resemble early mechanical SBO
Clinical course
Get follow up

24. Localized Ileus cholecystitis Pancreatitis Ulcer diverticulitis
appendicitis
Ureteral calculi

25. Generalized Ileus
Gas in dilated small bowel and large bowel to rectum, long air-fluid levels
Causes: electrolyte imbalances, sepsis, generalized peritonitis, blunt abdominal trauma, infiltration of the mesentery by tumor

26. Paralytic Ileus

27. Small bowel obstruction

28. Small bowel obstruction
Duration of obstruction, frequency of emesis, use of NG-suction may effect the radiographic appearance
20% False positive and false negative rate
No gas or fluid visible in small bowel of patients with high jejunal obstruction because of vomiting

29. Small bowel obstruction
Causes:
Most of small bowel obstruction are caused by postoperative adhesion (75%)
Adhesion, may occur as early 1 wk after surgery
Obstructing hernia(20%)
95% external hernia
Internal hernia are uncommon
Tumor
Ectopic gallstones (2%)
Acute appendicitis
Intestinal parasite
food

30. Small bowel obstruction
Radiographic appearance
Dilated small bowel loops: greater than 3 cm in diameter
Air-fluid level at two different level in the same segment of bowel
(different height in the same loop)
Loops fill with air “stepladder” configuration
Occasionally, “gasless” abdomen
Small amount of air trapped between the plicae circulares in upright film “string of pearls or bead” (not seen in adynamic ileus)

31. Small Bowel Obstruction (SBO)
Generalized dilated small bowel
Different height in the same loop

32. Small Bowel Obstruction (SBO)
Different height in the same loop
Generalized dilated small bowel
Step ladder pattern
Supine: tense arch from RLQ to LUQ: step ladder pattern
Different level of air fluid level in the same loop

33. Small Bowel Obstruction (SBO)

34. Small Bowel Obstruction (SBO)

35. String of pearl or bead
String of beads sign

36. ลักษณะภาพถ่ายรังสี
ลำไส้เล็กที่อยู่ก่อนถึงจุดอุดตันมีการขยายตัวใหญ่ขึ้น (small bowel dilatation) ส่วนใหญ่มักมีขนาดเส้นผ่าศูนย์กลางมากกว่า 2.5 ซม. (แต่ไม่เกิน 5.0 ซม.)
ระดับความสูงของลม และน้ำ (air-fluid level) ที่แตกต่างกันในลำไส้ขดเดียวกัน (different height in the same loop) เป็นลักษณะที่ช่วยวินิจฉัยลำไส้เล็กอุดตัน อย่างไรก็ตามลักษณะนี้สามารถพบได้ในภาวะลำไส้อืด (รูปที่ 4)
ไม่มีการขยายตัว และไม่มีลมอยู่ในลำไส้ใหญ่ เกิดลักษณะของความไม่ได้สัดส่วนกันระหว่างลมในลำไส้เล็ก และลำไส้ใหญ่ (disproportion of air between small bowel and large bowel)
ลักษณะการวางตัวของลำไส้เหมือนขั้นบันได (step ladder pattern) เป็นลักษณะของลำไส้ที่ขยายใหญ่ และเรียงตัวขนานกันจากช่องท้องน้อยด้านขวาไปยังช่องท้องด้านซ้ายบน ลักษณะเช่นนี้เกิดจากลำไส้เล็กถูกยึดโดยเยื่อแขวนลำไส้ (mesentery) ที่วางตัวจากช่องท้องด้านขวาล่างไปที่ระดับไตด้านซ้าย (รูปที่ 5)

37. ลักษณะภาพถ่ายรังสี
5. ลักษณะลมเม็ดเล็กๆ เรียงตัวกันเหมือนสร้อยลูกปัด (string of bead) คือ การที่มีลำไส้เล็กอุดตันเป็นเวลานาน ทาให้เกิดการสะสมของของเหลวในลำไส้เพิ่มมากขึ้นร่วมกับปริมาณของลมในขดลำไส้ ลดน้อยลง ทำให้ลมที่เหลืออยู่ขังอยู่ระหว่างร่องของเยื่อบุลำไส้เล็ก (Valvular conniventis) เป็นเงาของลมเม็ดกลมๆ เรียงตัวกันเป็นแถวมีลักษณะเหมือนสร้อยลูกปัด (รูปที่ 6)
6. ไม่มีลมในช่องท้อง (gasless abdomen) หากเกิดการอุดตันเป็นเวลานานจะมีของเหลวเข้ามา

38. Colonic Obstruction Cause of colonic obstruction
Primary adenocarcinoma of the colon (>50%)
Diverticulitis stricture (15%)
Colonic volvulus (10%)
Inflammatory bowel disease
Usually occur in sigmoid colon
( narrow caliber and more solid stool )
Carcinoma of cecum and ascending colon less likely to cause obstruction
( wider caliber, more liquid stool )

39. Colonic Obstruction Radiography
Dilated gas-filled loops of colon proximal to the site of obstruction and paucity or absence of gas in the distal colon and rectum

40. Large Bowel Obstruction

41. Large Bowel Obstruction
Absent rectal air, competent IC valve (closed loop)

42. Closed-Loop Obstruction
Segment of bowel that is obstructed at two point
Usually involve small bowel
Causes:
Adhesion
Internal hernia
Volvulus

43. Closed-Loop Obstruction
Plain film:
Nonspecific
Occasionally, dilated, air-filled segment of bowel may assume a “coffee bean” configuration
Persistence of an air-filled loop on sequential films for several days should suggest the possibility of a closed loop obstruction

44. Closed-Loop Obstruction
Vascular compromise may lead to edema and thickening or effacement of the valvulae conniventis
Clinical presentation: intermittent, crampy abdominal pain
A definitive diagnosis can be made only at surgery

45. Sigmoid Volvulus Usually in elderly
60-70% of case colonic volvulus involves sigmoid colon

46. Sigmoid Volvulus The classic radiography:
Dilated loop of sigmoid colon that has an inverted U configuration and absent haustra
The dilated bowel commonly extends into the upper abdomen above transverse colon
May be located in the midline or directed toward the right or left upper quadrant (mainly on left side)
“Coffee bean” sign = distinct midline crease corresponding to mesenteric root in largely gas distended loop (supine)

47. Sigmoid Volvulus
Contrast enema: smooth, tappered narrowing or “beaking” at rectosigmoid junction

48. Sigmoid Volvulus

49. Coffee Bean Sign

50. Sigmoid Volvulus

51. Sigmoid Volvulus

52. Beak sign in sigmoid volvulus

53. Cecal volvulus
Rotational twist of the right colon on its axist associated with folding of the right colon, so that the cecum is located in the midabdomen or LUQ
Less common than sigmoid volvulus

54. Cecal volvulus Cause: Incidence: about 40% of colonic volvulus.
Sudden distension by trauma, pressure constipation, distal colonic obstruction
Incidence: about 40% of colonic volvulus.
Age peak: year
Associated with malrotation(10-25% of case)

55. Cecal volvulus Plain film:
Dilated, air-filled cecum in an ectopic location, cecal apex in the LUQ
The medially placed IC valve may produce a soft tissue indentation  gas-filled cecum (coffee bean or kidney)
Barium enema: beak sign at mid ascending colon

56. Cecal volvulus

57. Soft tissue abnormalities

58. Liver RUQ of the abdomen 20-22 cm in its greatest transverse dimension
15-17 cm in its greatest vertical dimension
The hepatic angles may obscured by effusions or blood that infiltrates the retroperitoneal fat or because ascites, which displaces the liver edge away from the adjacent fat.

59. Liver Hepatomegaly: elevation of right hemidiaphragm,
inferior displacement of the hepatic flexure of the colon
lateral displacement of the lesser curvature of stomach
displace inferior edge of the liver beyond right margin of psoas muscle
inferior displacement of the right kidney

60. Hepatomegaly Inferior displacement of the hepatic flexure of the colon
Inferior liver margin
Inferior liver margin

61. Gallbladder
A shallow fossa on the inferior surface of the liver between the right and left lobes and is not often visualized on plain films.
Superior and lateral to the duodenal bulb and gastric antrum and superior to the proximal transverse colon

62. Gallbladder
Occasionally, the fundus may be visualized in normal patients if it indents the surrounding fat
Only 15% of gallstones are sufficiently calcified to be seen on plain film

63. Spleen
LUQ, beneath the left hemidiaphragm and posterior-lateral to the gastric fundus
12 cm in length, 7 cm in width
The outline of spleen in plain radiograph cannot be identified in 42% of normal subject

64. Spleen
Splenomegaly:
A soft tissue mass extending downwards and medially from LUQ
elevation of left hemidiaphragm,
medial displacement of the gastric air bubble and left kidney
splenic tip below the costal margin
Inferior displacement of colon
Inferior margin of spleen

66. Hepatosplenomegaly

67. Pneumoperitoneum

68. Pneumoperitoneum
As little as 1 ml of air could be detected below the RT.hemidiaphragm on properly exposed upright chest film Plain film for detection free air
Chest upright (most sensitive forpneumoperitoneum)
Left lateral decubitus
Lateral cross table view

69. Cause of pneumoperitoneum
Trauma
Abdominal surgery
Anastomotic leakage
Peritoneal tap
Endoscopy biopsy
Penetraing injury
Percutaneous endoscopic gastrostomy
Bowel
Perforation of benign ulcer
Perforation of neoplasm
Perforation of appendix
Jejunal diverticulosis
Diverticulosis of sigmoid colon

70. Pneumoperitoneum
On supine abdominal films must be able to recognize the intraperitoneum air, based on following sign
Serosal or Rigler’sign
Increased lucency in the RUQ
Triangular sign
Visualization of the undersurface of the diaphragm
Air in the Morison pouch
Outline of the normal peritoneal ligament
“ Football ” sign
Air in the lesser sac of peritoneal cavity

71. Pneumoperitoneum

72. Pneumoperitoneum Double bowel wall sign Falciform ligament sign

73. Pneumoperitoneum

74. Rigler sign
Double bowel wall sign

75. Increase lucency in RUQ

76. Air in Morison pouch

77. Falciform ligament sign

78. Pneumoperitoneum
Foot ball sign

79. Triangular sign

80. Pneumoretroperitoneum
Gas that enters the retroperitoneal spaces
Usually easily distinquished from intraperitoneal gas
bound by fascial plane, linear fashion along the margins of the psoas muscle, the renal outlines and medial undersurface of hemidiaphragm

81. Pneumoretroperitoneum
Causes:
Ruptured or perforation of retroperitoneum organ
Ulcer, injury, diverticulitis, blunt abdominal trauma
Location of the retroperitoneal gas may provide a clue to its origin
Duodenal perforation: confined to the right anterior pararenal space

82. Pneumoretroperitoneum
a retroperitoneal perforation with air outlining the liver edge, right kidney and the psoas muscle edge (arrow).

83. Pneumobilia Gas in the bile duct
Thin, branches, tubular areas of lucency in the central portion of the liver
Almost always result from communication between bile duct and intestine

84. Pneumobilia Cause Post op biliary-enteric fistula
choledochojejunostomy
Penetrate duodenal ulcer
Emphysematous cholecystitis
Recent passage of common duct stone

85. Pneumobilia

86. Portal venous gas
Thin, branching, tubular areas of lucency occupy the periphery of the liver and extend almost to the liver surface
Cause:
Intestinal ischemia or infarction
Dilatation of stomach and bowel

87. Intramural gas (pneumatosis intestinalis)
Gas in wall of the intestine
Two radiographic pattern
Bubbly
Thin or linear streaks of gas
In combination with portal venous gas, linear gas collections in the intestinal wall are almost always a sign of bowel infarction in adult patient

88. Pneumatosis intestinalis

89. Intramural gas
Emphysematous gastritis

90. Pneumatosis cystoides coli
Rare benign condition:
multiple gas-filled bleb or cysts in the wall of colon
Grapelike clusters of gas, usually segmental in distribution
Left colon > right colon

91. Ascites
Only large amount of ascites can be identified on abdominal radiographs
Plain abdominal findings of ascites
Obliteration of inferior edge of the liver
Widening of the distance between the flank stripe and the ascending colon
Medial displacement of the lateral edge of the liver
Fluid accumulation in the pelvis

92. Ascites Plain abdominal findings of ascites (cont.)
Separation of the bowel loops
Centrally located bowel loops with bulging flanks
Ground-glass appearance

93. Ascites

94. Ascites

95. Ascites

96. Abnormal Calcifications
Gallstone
KUB stone
Calcified organs
Pancreas, nodes
Calcified old granuloma: liver, spleen
Calcified mass

97. Gallstones GS: investigation of choice: US
Renal stone: investigation of choice: plain KUB
DDx: lateral view

98. Gallstones
sand stones
Sandstones in GB and cystic ducts

99. Calcified Pancreas

100. Calcified Nodes

101. Calcified Splenic Granuloma

102. Calcified Uterine Fibroid

103. Retroperitoneum
Intra-abdominal tissue planes and visceral surfaces are visible on plain films- surrounding fat
Identifying normal anatomic structures and in recognizing and localizing pathologic process

104. Retroperitoneum space
Lies posterior to the parietal peritoneum and anterior to the transversalis fascia
Divided into three disinct compartment
Anterior pararenal space
Perirenal space
Posterior pararenal space

105. Anterior pararenal space
Lie anterior to the perirenal space and lateroconal fascia
Retroperitoneum duodenum
Pancreas
Ascending and descending colon

106. Perirenal space
Confined by anterior and posterior layer of renal fascia
Contains:
Kidneys
Adrenal glands
Abundant fat
Perirenal fat allows plain film visualization of the renal outlines in most patient

107. Perirenal space
Perirenal fat is responsible for plain film visualization of the upper half of the psoas muscle and medial aspect of the hepatic and splenic angles
Obliteration of perirenal fat: inflammation, blood or urine.
Medially, the perirenal space is in continuity with the aorta and often fills with blood in patient with ruptured aortic aneurysms.

108. Perirenal space
Laterally, anterior and posterior layers of perirenal fascia fuse to form the lateroconal fascia, which continues laterally and ventrally to fuse with parietal peritoneum along lateral abdominal wall

109. Posterior pararenal space
Lies posterior to the posterior perirenal and lateroconal fascia and anterior to the transversalis fascia lining the abdominal wall
Contains variable amount of fat, but no organs
Medially, the posterior pararenal space originate at the lateral margin of the psoas muscle and is not continuous across the midline

110. Posterior pararenal space
Laterally, the posterior pararenal fat continues around the flank to become continuous with properitoneal fat of the lateral abdominal wall, forming the “flank stripe”
Posterior pararenal fat is continuous inferiorly with extraperitoneal fat in the pelvis.

111. Psoas muscle Arise from the T12-L5 vertebrae
Extends inferiorly to join the iliac muscle below the iliac crest and continues as the iliopsoas muscle to the lesser trochanter
Lateral margin: outlined by perirenal fat superiorly and posterior pararenal fat below the level of the kidney
About 19% of normal individuals have a blurred right psoas outline.

112. Psoas muscle
Blood or inflammatory exudate in the adjacent retroperitoneal fat may cause obliteration of the margin of the psoas muscle.
Absence of the psoas margin on plain films must be interpreted with caution
Lumbar scoliosis
Rotation of the spinal column
Fluid-filled bowel loop
Normal variation

113. Reference
Richard M. Gore, M.D. Gastrointestinal radiology second edition
Michael P. Federle, M.D. Diagnostic Imaging Abdomen first edition