Acute abdomen

1. Dr.koushik sharma ACUTE ABDOMEN

2. Acute abdomen is a term used to encompass a spectrum of surgical, medical and gynecological conditions (intra-abdominal process), ranging from the trivial to the life threatening, which require hospital admission, investigation and treatment

3. Generalized AP Perforation AAA Acute pancreatitis Bilateral pleurisy

4. Central AP Early appendicitis SBO Acute gastritis Acute pancreatitis Ruptured AAA Mesenteric thrombosis

5. Epigastric pain DU / GU Oesophagitis Acute pancreatitis AAA

6. RUQ pain Gallbladder disease DU Acute pancreatitis Pneumonia Subphrenic abscess

7. LUQ pain GU Pneumonia Acute pancreatitis Spontaneous splenic rupture Acute perinephritis Subphrenic abscess

8. Suprapubic pain Acute urinary retention UTIs Cystitis PID Ectopic pregnancy Diverticulitis

9. RIF pain Acute appendicitis Mesenteric adenitis (young) Diverticulitis PID Salpingitis Ureteric colic Meckels diverticulum Ectopic pregnancy Crohns disease Biliary colic (low-lying gall bladder)

10. Loin pain Muscle strain UTIs Renal stones Pyelonephritis

11. LIF pain Diverticulitis Constipation IBS PID Rectal Ca UC Ectopic pregnancy

12. The various imaging modalities available for investigating the acute abdomen include: plain films, contrast studies ultrasound (US) computed tomography(CT), and magnetic resonance imaging (MRI). The choice of the initial modality to be used should be guided by the disease suspected on clinical grounds

13. Plain radiography plain radiographs continue to be initial imaging modality In intestinal obstruction and perforation. Contrast examinations have a limited role. An upper GI series with water soluble contrast may be performed in cases of suspected perforation or a contrast enema may be required to confirm a colonic obstruction.

14. Ultrasound US is the ideal screening modality for suspected hepatobiliary disease suspected pelvic pathology such as ectopic gestation or acute pelvic inflammatory disease (PID). right lower quadrant pain. In cases of suspected intestinal obstruction, to differentiate between mechanical obstruction and paralytic ileus. US demonstrates increased peristalsis in cases of mechanical obstruction, whereas presence of dilated, atonic loops suggest the diagnosis of paralytic ILEUS. US is also helpful in localizing intra-abdominal abscesses, particularly in the solid viscera.

15. CT MDCT has become the imaging modality of choice for evaluation of the acute abdomen. It provides a comprehensive view of all the intra-abdominal solid and hollow viscera, as well as the peritoneum, mesentery, lymph nodes and retroperitoneum. Data can be acquired in different phases making MDCT an ideal modality for evaluation of suspected mesenteric ischemia or vasculardisorders such as abdominal aortic aneurysms. Low dose unenhanced CT has replaced excretory

16. MRI Recent improvements in resolution and development of faster breath-hold sequences have drastically increased the utility of MRI in evaluation of the gut. However, MRI is still not routinely used for evaluation of an acute abdomen except in situations where iodinated contrast cannot be administered or in pregnant patients.

17. What to Examine by Plain X-ray Gas pattern Extraluminal air Soft tissue masses Calcifications Skeletal pathology

18. Normal Gas Pattern Stomach Always Small Bowel Two or three loops of non-distended bowel Normal diameter = 2.5 cm Large Bowel In rectum or sigmoid almost always

19. Gas in stomach Gas in a few loops of small bowel Gas in rectum or sigmoid Normal Gas Pattern

20. Normal Fluid Levels Stomach Always (except supine film) Small Bowel Two or three levels possible Large Bowel None normally

21. Erect Abdomen Always air/fluid level in stomach A few air/fluid levels in small bowel

22. Large vs. Small Bowel Large Bowel Peripheral Haustral markings don't extend from wall to wall Small Bowel Central Valvulae extend across lumen

23. Haustra films Faecal mottling

24. Complete Abdomen Obstruction Series Supine Erect or left decubitus Chest - erect or supine Prone or lateral rectum

25. Complete Abdomen Supine Looking for Scout film for gas pattern Calcifications Soft tissue masses Substitute none

26. Complete Abdomen Erect Looking for Free air Air-fluid levels Substitute left lateral decubitus

27. Complete Abdomen Erect Chest Looking for Free air Pneumonia at bases Pleural effusions Substitute supine chest

28. Complete Abdomen Prone Looking for Gas in rectum/sigmoid Gas in ascending and descending colon Substitute lateral rectum

29. Abnormal Gas Patterns 1. Functional Ileus Localized (Sentinel Loops) Generalized adynamic ileus 2. Mechanical Obstruction SBO LBO

30. Sentinel Loops Supine Prone Localized Ileus Key Features One or two persistently dilated loops of large or small bowel Gas in rectum or sigmoid

31. Pancreatitis Ulcer Diverticulitis Cholecystitis Appendicitis Sentinel Loops Localized Ileus

32. Localized Ileus Pitfalls May resemble early mechanical SBO Clinical course Get follow-up

33. Generalized Ileus Key Features Gas in dilated small bowel and large bowel to rectum Long air-fluid levels post-op patients have generalized ileus Other causes:- Peritonitis Hypokalemia Metabolic disorder as hypothyroidism Vascular occlusion

34. Generalized Adynamic Ileus Supine Erect

35. The distinction between small & large-bowel dilatation Small bowel large bowel 1. vulvulae conniventes present in jejunum absent 2. number of loops many few 3. distribution of loops central peripheral 4. haustra absent present 5. diameter 3-5 cm 5 cm + 6. radius of curvature small large 7. solid feces absent *present haustra may be completely absent from the descending & sigmoid colon.

36. Abnormal Gas Patterns Ileus and Obstruction Localized ileus Generalized ileus Mechanical SBO Mechanical LBO

37. Conditions causing extraluminal air Perforated abdominal viscus Abscesses (subphrenic and other) Biliary fistula Cholangitis Pneumatosis coli Necrotising enterocolitis Portal pyaemia

38. Extraluminal Air Free Intraperitoneal Air

39. Chest X-ray This is an essential examination in any patient with acute abdomen because: 1-It is the best radiograph to show the presence of a small pneumoperitoneum. (even 2ml) 2-A number of chest conditions may present as an acute abdominal pain : pneumonia (particularly lower lobe), MI, . 3- Acute abdominal conditions may be complicated by chest pathology: pleural effusion frequently complicate acute pancreatitis. 4-Even when the chest radiograph is normal it acts as a valuable baseline.

40. Small amount

41. Signs in pneumoperitoneum 42 Erect chest radiograph reveals free gas between the liver and both does of diaphragm.

42. 43 Left lateral decubitus film showing gas between the liver and abdominal wall.

43. gns of pneumoperitoneum of supine radiograph 44 Right upper quadrant gas Peri hepatic Sub hepatic Morrisons pouch Fissure for ligament teres Riglers (double wall sign) Ligament visualization Falciform Umbilical inverted V sign Triangular air The cupola sign Football or air dome Scrotal air in children

44. Crescent sign Free Intraperitoneal Air

45. Gas in subhepatic space 46 Supine abdominal radiograph shows an elliptical collection of air within the subhepatic space

46. Falciform ligament sign

47. Doges cap sign 48 Doges Cap sign refers to free air in Morrison's pouch. Morrison's pouch is normally a potential space between the right kidney and the liver

48. Triangular gas shadow superior to kidney and postero-inferior to 11th rib 49

49. Riglers sign 50 Rigler's sign refers to the appearance of the bowel wall on plain film when it is outlined by intraluminal and extraluminal air .The extra luminal air is free peritoneal gas

50. Falciform ligament visualization 51 Visualization of Falciform ligament by free gas on either side of the ligament

51. Football sign 52 The football sign likens the massively air-filled peritoneum to an American football In the supine position, free air collects anterior to the abdominal viscera, producing a sharp interface with the parietal peritoneum and thereby creating the football outline

52. 53

53. Double Bubble Sign 54 Two collections of overlapping gas- one of these collections is sub diaphragmatic free gas and the other is normal gas within the fundus of the stomach

54. The Cupola Sign 55 An arcuate collection of free intraperitoneal air beneath the central tendon of diaphragm. The superior border is well defined (arrows) compared with the inferior extent of the collection.

55. The Triangle Sign 56 The triangle sign refers to small triangles of free gas that can typically be positioned between the large bowel and the flank(black arrow)

56. CONDITIONS SIMULATING PNEUMOPERITONEUM 57 1. Chilaiditis syndrome-intestine between liver and diaphragm 2. Subphrenic abscess 3. Curvilinear supradiaphragmatic pulmonary collapse 4. Subdiaphragmatic fat 5. Cyst in pneumatosis intestinalis 6. Sub pulmonary pneumothorax

57. Chilaiditis syndrome Chilaiditis syndrome is an important normal variant on the erect chest radiograph, which must be distinguished from pathological free gas under the diaphragm. (apparent, as haustra are seen within the gas filled structure). This gas is still contained in the bowel loop.

58. 59 Chilaiditis syndrome- intestine between liver and diaphragm

59. CONDITIONS SIMULATING PNEUMOPERITONEUM 60 Right sided subphrenic abscess

60. CONDITIONS SIMULATING PNEUMOPERITONEUM 61 Large bulla at the base of the right lung mimics a large pneumoperitoneum

61. Intestinal obstruction:

62. Intestinal obstruction: Gastric dilatation : could be Part of paralytic ileus (functional). Mechanical : usually caused by peptic ulceration or a carcinoma of the pyloric antrum , often lead to massive fluid filled stomach which occupy most of the upper abdomen.

63. GASTRIC DILATATION Causes 1. Mechanical gastric outlet obstruction. 2. Paralytic ileus 3. Gastric volvulus 4. Air swallowing. 64

64. GASTRIC VOLVULUS 65 o Twisting of the stomach around its longitudinal or mesenteric axis o Organoaxial volvulus - Stomach rotates along its long axis and becomes obstructed, with the greater curvature being displaced superiorly and the lesser curvature located more caudally in the abdomen

65. 67 Mesenteroaxial volvulus --less common , occurs when the stomach rotates along its short axis, with resultant displacement of the antrum above the gastroesophageal junction

66. Mechanical SBO Key Features Dilated small bowel Little gas in colon, especially rectum Key: disproportionate dilatation of SB SBO

67. Mechanical SBO Causes Adhesions Hernia* Volvulus Gallstone ileus* Intussusception *Cause may be visible on plain film

68. Mechanical SBO Pitfalls Early SBO may resemble localized ileus -get F/O

69. Differentiating SBO from Paralytic Ileus SBO Ileus Etiology Patient with prior surgery weeks to years prior Recent (hours) post- operative patient Pain Colicky Not a prominent feature Abdominal distension Frequently prominent May not be apparent Bowel sounds Usually increased Usually absent Small bowel dilatation Present Present Large bowel dilatation Absent Present 72

70. Mechanical LBO Key Features Dilated colon to point of obstruction Little or no air in rectum/sigmoid Little or no gas in small bowel, if Ileocecal valve remains competent

71. LBO

72. LBO Supine Prone

73. Mechanical LBO Causes Tumor Volvulus Hernia Diverticulitis Intussusception

74. Mechanical LBO Pitfalls Incompetent ileocecal valve Large bowel decompresses into small bowel May look like SBO Get BE or follow-up

75. Carcinoma of Sigmoid LBO Decompressed into SB ProneSupine

76. The goals of imaging in a patient with suspected intestinal obstruction have been defined and are as follows: 1. To confirm that it is a true obstruction and to differentiate it from an ileus. 2. To determine the level of obstruction. 3. To determine the cause of the obstruction. 4. To look for findings of strangulation. 5. To allow a good management either medically or surgically by laparoscopy or laparoscopy).

77. Post-op C-section Adynamic Ileus

78. Mesenteric Occlusion

79. Small bowel obstruction Small bowel obstruction (SBO) accounts for approximately 4% of all patients presenting with an acute abdomen. The commonest cause is adhesions due to previous surgery . The main value of plain film is in assessing the degree & severity of the obstruction (not the cause). On plain film, changes in small bowel obstruction may appear after 3-5 hours if there is complete obstruction and marked after 12 hours. Radiologically, complete obstruction of the small bowel usually causes small bowel dilatation with accumulation of both gas & fluid and a reduction in caliber of the large bowel, if dilated gas filled loops of small bowel will be readily identified on the supine

80. Small Bowel Obstruction The 'Small Bowel Feces Sign' (SBFS) is a very useful sign as it is seen at the zone of transition thus facilitating identification of the cause of the obstruction. The SBFS has been defined as gas and particulate material within a dilated small-bowel loop that simulates the appearance of feces.

81. if fluid filled loops The dilated small bowel loops appears as a sausage, oval or round soft tissue densities that change in position in different views, sometime with small gas bubbles trapped in rows between the vulvulae conniventes on horizontal ray films; this is known as 'string of beads' sign which is virtually diagnostic of small bowel obstruction and does not occur in normal people.

82. Strangulating obstruction is a mechanical obstruction caused when two limbs of a loop are incarcerated within a hernia so as to cause vascular compromise by compression of the mesenteric vessels. Presence of thumb-printing due to submucosal edema or hemorrhage should suggest ischemia in the loops. If left untreated, the ischemia may progress causing breach of the mucosa, intramural air, air in the mesenteric and portal veins and frank perforation which are all ominous signs.

83. Intramural air in the form of parallel streaks of gas along the bowel wall or as rings may also be seen in infants with necrotizing enterocolitis. This appearance should not be confused with the bubbly appearance of pneumatosis coli which is a benign condition affecting the colon in adults.

84. The causes of intestinal obstruction vary with the age of the patient. In neonates and infants, the usual causes of obstruction are congenital conditions such as : 1. hypertrophic pyloric stenosis, 2. duodenal stenosis or atresia, 3. ileal atresia etc. a) In young children,intussusception or Ladds bands are common causes of b) obstruction. c) Intussusception may be seen as a mass-like soft tissue shadow with a crescent of gas surrounding the leading edge. d) A barium examination will reveal the coil-spring appearance of the intussuscepiens with the claw sign

85. 90 There is a prominent crescent sign in the left upper quadrant with a subtle target sign in right upper quadrant.

86. 91 Intussusceptions in the left upper quadrant on this plain film of an infant with pain vomiting

87. In adults, adhesions and hernias account for more than 80% of small bowel obstructions. Other causes include an intraluminal obturation by neoplasm, gallstone or bezoar or a volvulus due to twisting of the gut around its mesentery.

88. Gall stone ileus This is a mechanical obstruction caused by the impaction of one or more gall stones in the intestine, usually in the terminal ileum, but rarely in the duodenum or the colon. The commonest radiological signs to be observed are : 1- A gas shadow within the bile ducts and/ or the gall bladder. 2- Complete or incomplete intestinal obstruction. 3- An abnormal location of an already observed gall stone.

89. Air in biliary tree Gallstone Gallstone Ileus

90. Large bowel obstruction The commonest cause is carcinoma, of which about 60% are situated in the sigmoid colon. The radiological appearance of large bowel obstruction depends on the state of competence of the ileocecal valve : - TYPE 1A:the ileocecal valve is competent leading to dilated gas filled colon with its haustral markings and a distended thin-walled cecum but no distension of small bowel., this can lead to massively distended cecum, which is in then at a higher risk of perforation secondary to ischemia ( transverse cecal diameter of 9 cm had been suggested as the critical point above which the danger of perforation exists).

91. As this type progresses, small bowel distention occur (type 1B), with a radiological appearance identical to that of paralytic ileus . In TYPE II obstruction, the ileocecal valve is incompetent and the cecum and ascending colon are not distended, but the back pressure from the colon extends into the small bowel which may simulate small bowel obstruction.

92. Cecal volvulus (Right colon volvulus) This account for less than 2% of adult intestinal obstruction ( young age group). The diagnosis of acute cecal volvulus is rarely made on clinical ground alone, and so radiological diagnosis become much more important & it is usually comprises a distended lower abdominal viscus with one or two haustral markings, concomitant small bowel dilatation & a collapsed left half of the colon. Note: identification of gas filled appendix confirm the diagnosis.

93. Sigmoid volvulus This is the classic volvulus, occurring in old, mentally subnormal patients. It is usually chronic with intermittent acute attacks. Radiological signs : inverted U shaped distended loop which is devoid of haustra (ahaustral). Liver or left flank overlap signs. Apex of the volvulus above T10. Air fluid ratio greater than 2:1.

94. Sigmoid volvulus `bird of prey' sign chronic volvulus.

95. Contrast failed to progress beyond the recto-sigmoid junction. At this point, there is smooth, curved tapering like a bird's beak ("bird of prey sign")

96. Intestinal obstruction Dilated gas filled bowel loops with air-fluid levels proximal to the obstruction Paralytic ileus-both SB and LB are dilated String of beads sign-Mechanical obstruction Thumb printing due to sub mucosal edema- Ischemia Intramural air-Necrotizing enterocolitis Coffee bean appearance- Sigmoid volvulus

97. Toxic Megacolon Toxic megacolon is an acute transmural fulminant colitis which can occur as a complication of any colitis. most commonly seen with ulcerative colitis (1.6- 13% of cases). Plain radiographs show marked colonic dilatation(> 8 cm) particularly of the transverse colon as this is the least dependent part of the large bowel in the supine position. The wall has a shaggy appearance with mucosal islands or pseudopolyps with absence of haustra due to profound inflammation and ulceration. Theremay be air-fluid levels and small bowel

98. Toxic megacolon

99. CT shows the distended colon filled with air, fluid and blood with a distorted or absent haustral pattern and irregular, nodular wall. There may be presence of intra-mural air or blood

100. Other conditions Gangrenous cholecystitis -intraluminal and intramural air Sentinel loop, gasless abdomen and colon cutoff sign in Pancreatitis Extraluminal mottled gas in Abdominal abscess Gas in perinephric region Emphysematous pyelonephritis Ureteric colic Urolithiasis

101. USG and CT An ileus may not be appreciated on a plain abdominal film if bowel loops are filled with fluid only without intraluminal air. Alternatively if a plain abdominal film does indicate an ileus then sonography or CT are usually needed to identify its cause.

102. APPENDICITIS

103. Appendicitis plain radiograph Fluid levels localized to the caecum and terminal ileum, indicating inflammation in the right lower quadrant Localized ileus with gas in the cecum, ascending colon and terminal ileum Increased soft tissue density of the right lower quadrant Blurring of the right flank stripe and presence of a radiolucent line between the fat of the peritoneum and tansverus abdominis Fecolith in the right iliac fossa Gas filled appendix Blurring of the psoas shadow on the right side.

104. Appendicitis usg A normal appendix has a maximum diameter of 6 mm, is surrounded by homogeneous non- inflamed fat, is compressible and often contains intraluminal gas.

105. Appendicitis

106. Appendicitis General CT findings for acute appendicitis include: 1. Dilated appendix greater than 6 mm or visualization of an appendicolith with an appendix of any size 2. Peri-appendicial fat stranding

107. This image of an acute abdomen (arrow) displays periappendicial stranding and dilattion of its terminal portion . For comparison, this image of a normal appendix can be visualized at the ileocecal junction. Also notethe fat ventralcontaining heria

108. Inflammation- Cholecystitis Acute cholecystitis is inflammation of the gallbladder usually from impaction of a gallstone within the cystic or common bile duct. Plain radiograph: Gallstones seen in 20% Duodenal ileus Il eus of hepatic flexure of colon Right hypochondrial mass due to enlarged gallbladder Gas within the biliary system

109. Ultrasound is the preferred imaging method to confirm cholecystitis in the appropriate clinical setting. sonographic signs include calculi (in 95%) distension of the gallbladder edematous wall, mucosal irregularity, intramural gas and/or pericholecystic collection Doppler: increased mural colour uptake

110. Acute calculous cholecystitis: Calculus obstructs the cystic duct The trapped concentrated bile irritates the gallbladder wall, causing increased secretion, which in turn leads to distention and edema of the wall. Rising intra luminal pressure compresses the vessels, resulting in thrombosis, ischemia, and subsequent necrosis and perforation of the wall.

111. CT findings of cholecystitis include: wall thickening, pericholecystic stranding, GB distension, pericholecystic fluid, subserosal edema, high attenuation bile and sloughed membranes, gas or septations within the gallbladder Complicated cases may reveal perforation or hepatic abscess formation.

112. MRI IS COMPLEMENTORY TO CT AND USG IN Demonstrating impacted calculi in the gallbladder neckor cystic duct which are often difficult to detect on US. Also, conditions causing acalculous cholecystitis like adenomyomatosis, gall bladder polyp, malignant neoplasm or other cancers can be depicted on mr

113. Thickening of gallbladder wall Cholelithiasis.

114. Complications of acute cholecystitis include: empyema, gangrenous cholecystitis, Gallbladder perforation and emphysematous cholecystitis.

115. Empyema: occurs when pus fills the distended and inflamed GB,typically in diabetic patients. On US and CT, pus resembles sludge. Heavily T2-weighted images are sensitive in demonstrating purulent bile as a dependent hypointense layer relative to normal bile.

116. Gangrenous cholecystitis : is an advanced, severe form of acute cholecystitis, seen more common in elderly men. It results from marked distension of the GB with resultant increase in tension in the wall. Associated inflammation leads to ischemic necrosis. US reveals heterogenous or striated thickening of GB wall or intraluminal membranes representing desquamated mucosa. US findings typical of uncomplicated acute cholecystitis may be absent in this subset of patients: GB wall thickness may be less than 3 mm CT features consist of: intraluminal membranes, irregular wall, pericholecystic fluid/abscess and lack of mural enhancement.

117. Gall bladder perforation : most often a complication of acute gangrenous cholecystitis. blood supply is poor in the region of fundus, this is the most common site of perforation. Perforation can be classified into 3 types: A)acute free perforation into peritoneal cavity, B) subacute perforation with pericholecystic abscess and C) chronic perforation with a cholecystoenteric fistula. Subacute perforations are the most common. Following perforation, US, CT and MR show complex pericholecystic fluid collections and the wall of GB can appear focally disrupted.

118. Emphysematous cholecystitis : rare form of acute cholecystitis seen in patients with diabetes and peripheral atherosclerotic disease. The majority of patients are between 50-70 years. US demonstrates intraluminal and intramural gas as highly echogenic foci. CT is the most sensitive and specific imaging modality to identify gas in the lumen or wall.

119. ACUTE PANCREATITIS Acute pancreatitis refers to acute inflammation of the pancreas. Causes Gallstones (most common) Alcohol abuse, usually chronic Trauma, more often penetrating Drug-induced Anatomic abnormality ERCP-induced Infectious, especially post-viral in children Vasculitis Idiopathic

120. ACUTE PANCREATITIS Pathological changes are edema, hemorrhege,lnfarction,fat necrosis followed by acute suppuration Inflammatory processes tend into gastro colic ligament or paraduodenal areas- follow route of mesentry or extend out of peritoneum into perirenal space. Lot of radiological signs described, but many are of little value in diagnosing individual cases.

121. Plain film changes- Chest x-ray- o Left sided pleural effusion o Splinting of left hemidiaphragm o Basal atelactasis Abdominal film- o Duodenal ileus o Gasless abdomen o colon cut off sign o Renal halo sign o Absent left psoas shadow o Indistinct mottled shadowing o Sentinel loop o Intrapancreatic gas-abscess/ enteric fistula 150

122. The abrupt termination of gas within the proximal colon at the level of the radiographic splenic flexure, usually with decompression of the distal colon

123. A sentinel loop is a focal area of adynamic ileus close to an intra-abdominal inflammatory process. The sentinel loop sign may aid in localizing the source of inflammation

124. Later stages- pancreatic pseudocyst visible on plain film as large soft tissue mass Pleural effusions, mainly left sided.

125. A/c pancreatitis Early stages-USG is preferred USG reveals enlarged hypoechoic pancreas with peripancreatic fluid,+/- cholelithiasis Also in follow up of fluid collection or pseudocyst formation. CECET modality of choice- for diagnosis,detect extrapancreatic,intras abdomial pathology For staging of severity-CTSI

126. CT Findings typical of pancreatitis include: 1. An enlarged pancreas with infiltration of the surrounding fat 2. Peripancreatic fluid collections can often be seen 3. Pseudocysts, (encapsulated fluid collections containing pancreatic secretions, are later complications of pancreatitis)

127. MRI Recent improvements in resolution and faster breath hold sequences have drastically increased usage of MRI in abdomen. But not routinely used in a/c abdomen except in situations where contrast cannot be administered or in pregnant patients

128. Most important objective of imaging in a/c abdomen is Identify most common causes Choose the modality of imaging appropriately Diagnose or exclude common conditions

129. Notice the peripancreatic stranding (bars) as well as the fluid thickening of the interfascial space

130. A common complication of pancreatitis is the development of pancreatic necrosis. Lack of gland enhancement following IV contrast administration is diagnostic. When over half the pancreas becomes necrosed, the mortality rate may reach as high as 30%.

131. Pancreatic necrosis

132. Pancreatic pseudocyst

133. Intra-Abdominal Abscess A localized collection of pus can occur anywhere in the abdomen: in the parenchyma of solid organs, in the peritoneal or extra-peritoneal spaces. Early detection, may be seen. At times, the abscess may have a solid appearance. Color Doppler demonstrates peripheral hypervascularity. CT will show a low attenuation fluid collection with mass effect and peripheral rim enhancement with or without gas bubbles or an air-fluid level.

134. OTHER CAUSES OF ACUTE ABDOMEN

135. Sigmoid diverticulitis If the pain is located in the LLQ main concern is sigmoid diverticulitis. In diverticulitis sonography and CT show diverticulosis with segmental colonic wall thickening and inflammatory changes in the fat surrounding a diverticulum. Complications of diverticulitis such as abscess formation or perforation, can best be excluded with CT.

136. Diverticulitis

137. A case of diverticulitis showing a thickened sigmoid colon and a diverticulum

138. Mesenteric lymphadenitis A common mimicker of appendicitis. It is the second most common cause of right lower quadrant pain after appendicitis. It is defined as a benign self-limiting inflammation of right-sided mesenteric lymph nodes without an identifiable underlying inflammatory process, occurring more often in children than in adults. This diagnosis can only be made confidently when a normal appendix is found, because adenopathy also frequently occurs with appendicitis.

139. Epiploic Appendagitis Epiploic appendages are small adipose protrusions from the serosal surface of the colon. An epiploic appendage may undergo torsion and secondary inflammation causing focal abdominal pain that simulates appendicitis when located in the right lower quadrant or diverticulitis when located in the left lower quadrant. The characteristic ring-sign corresponds to inflamed visceral peritoneal lining surrounding an infarcted fatty epiploic appendage.

140. Plain radiograph Calcifications in acute appendagitis

141. USG rounded, noncompressible, hyperechoic mass, without internal vascularity, and surrounded by a subtle hypoechoic line 5. They are typically 2-4 cm in maximal diameter.

142. Renal Colic

143. Distal ureteral stone lead ing to right hyrdronephrosis in above image Ureteral junctional stone Renal Colic

144. Renal stone right sided hydronephrosis Renal Colic

145. Urolithiasis

146. Inflammation- Colitis Colitis, or inflammation of the colon, is a frequent cause of abdominal pain. Specific entities which produce inflammatory thickening of the colon include:- Diverticulitis, inflammatory bowel disease, pseudomembranous colitis, and other bacterial infections (i.e. typhlitis).

147. This example of colitis shows thickening of the colon and pericolonic stranding typical of inflammation.

148. Thickening of sigmoid colon due to pseudomembranous colitis

149. MESENTRIC ISCHEMIA Acute occlusion of the superior mesenteric artery (SMA) due to embolus is the most common cause of mesenteric ischemia accounting for nearly 50% of cases due to Thrombosis of the SMA or the superior mesenteric vein (SMV) are responsible for another 10-20% of cases.

150. The manifestation may range from a self-limiting superficial ischemia involving the watershed zones to a diffuse ischemic injury to the entire bowel - shock bowel. There are three stages of acute mesenteric ischemia: In the first stage, there is mucosal involvement with necrosis, ulcerations and/or hemorrhage. The injury is superficial and will eventually heal completely. In stage II, there is necrosis of the deep submucosal and muscular layers which may lead to the development of fibrotic strictures. Stage III ischemia represents transmural bowel necrosis which requires immediate surgical intervention. The imaging appearance in a given

151. Plain films reveal the characteristic thick-walled dilated loops with thumb-printing. Intramural air or porto-mesenteric air is also rarely visualized on the plain radiograph. MDCT angiography is the modality of choice for the evaluation of bowel ischemia The arterial occlusion/narrowing as well as the venous occlusion can be readily detected. Involvement of the vasa recta (Coombs sign) may be seen in small vessel vasculitis

152. In addition, involvement of a long segment of bowel or both small and large bowel with skip segments are features of small vessel disease. The most common finding of mesenteric ischemia is bowel wall thickening though this feature strongly depends on the degree of bowel distension. Mural thickening is commoner with ischemic colitis and with veno-occlusive disease but is rare in arterio-occlusive disease where the involved segment of bowel may show dilated, fluid-filled loops with paper-thin walls

153. The bowel wall may show a striated appearance due to the presence of sub-mucosal edema or hemorrhage. In complete arterial occlusion, there can be absence of the normal enhancement of the bowel wall. Conversely, in non-occlusive ischemia there can be abnormal persistent mural enhancement. The target sign is seen when there is hyperenhancement of the mucosa and submucosa due to hyperemia and hyperperfusion with mural edema

154. THMB PRINTING IN ISCHEMIC COLITIS

155. SMA thrombosis

156. VASCULAR CAUSES Vascular conditions that may present as acute abdomen include rupture of an aortic aneurysm, spontaneous aortic occlusion, acute hemorrhage and hepatic or splenic vascular occlusion average age at the time of diagnosis being 65-70 years. Most abdominal aortic aneurysms are true aneurysms and occur below the level of renal arteries. An abdominal aortic aneurysm is defined as an aortic diameter of 3cm or more42 while a diameter of 5.5 cm or more warrants urgent intervention.

157. Multidetector CT is the modality of choice for evaluation of acute aortic syndrome. The most common finding of rupture of aortic aneurysm is a retroperitoneal hematoma adjacent to the aneurysm . Other CT features may include active extravasation of contrast, extension of periaortic blood into perirenal or pararenal spaces or the psoas muscle or peritoneal cavity

158. Aneurysms

159. Signs predictive of impending rupture are: a. Draped aorta sign Seen with contained leak. The posterior wall of aorta cannot be defined due to close application and lateral draping of the aneurysm around the adjacent

160. b. Increase in aneurysm size A patient with a very large aneurysm (> 7cm diameter) who presents with acute aortic syndrome has a high likelihood of aneurysm rupture. Also, a rate of enlargement of >10 mm per year warrants surgical repair. c. Thrombus-to-lumen ratio - This ratio decreases with increasing aneurysm size. A thick circumferential thrombus is protective against rupture. d. Focal discontinuity in intimal calcification.

161. e. Hyperattenuating crescent sign due to hemorrhage in either the peripheral thrombus or aneurysm wall.

162. Acute abdominal hemorrhage may result due to ruptured aneurysm in a case of polyarteritis nodosa, ruptured tumor (usually renal cell carcinoma) or in a patient on anticoagulant therapy. Non-contrast CT demonstrates a hyperdense collection at the site of hemorrhage. MDCT angiography can accurately delineate the site and cause of hemorrhage.

163. Rare causes of acute abdomen include: hepatic vein thrombosis (acute Budd-Chiari syndrome) and portal vein thrombosis. US in the acute phase may show liver enlargement, partial or complete inability to visualize hepatic veins, intraluminal hepatic vein echogenicity or thrombosis, marked narrowing of intrahepatic IVC and ascites. Color Doppler: Absence of flow or flow in an abnormal direction in all or part of the hepatic veins may be seen. CT and MR are complimentary techniques for definitive diagnosis which provide a more complete evaluation of the hepatic parenchyma, hepatic veins and IVC.

164. Pelvic Disease

165. Signs of a ruptured ectopic pregnancy on ultrasound an inhomogeneous adnexal mass, pelvic fluidor hematoma, decidual reaction without intrauterine gestation sac, in the presence of a positive pregnancy test. Visualization of an echogenic adnexal ring separate from the ovary that has prominent peripheral flow on color Doppler is highly suggestive of ectopic gestation. Corpus luteum is a useful guide while looking for an ectopic pregnancy and is usually seen in the ipsilateral ovary in 70-85% cases. Using transvaginal ultrasound, the live embryo can be detected in upto 17% of all ectopic pregnancies.

166. FIBROIDS Fibroids may present with acute pain if there is torsion or degeneration of a submucosal or subserosal fibroid. On imaging, uterine enlargement with a focal mass or contour deformity are seen. Degenerated fibroids may have a cystic appearance.

167. MRI Haemorrhagic fibroid degeneration. This patient, known to have uterine fibroids, presented to the accident and emergency department with low-grade pyrexia, tachycardia and acute lower abdominal pain. a Sagittal T2 image demonstrates a large uterine fibroid with high signal intensity centrally with a very low signal intensity rim suggestive of peripheral haemosiderin. b Axial T1 with fat-saturated image shows high signal intensity within the fibroid consistent with haemorrhage (black arrow). c Axial T1 with fat saturation following gadolinium administration demonstrates lack of enhancement within the fibroid (black arrow), consistent with infarction. The surrounding myometrium enhances normally (white

168. OVARIAN TORSION Ovarian torsion usually occurs in children and is attributed to excessive mobility of the ovary. In adults,a cyst or mass, frequently a cystic teratoma, is present in the ovary undergoing torsion. Sonographic findings : 1. enlarged ovary with peripherally distributed follicles, 2. an associated cyst or mass 3. diminished or absent central venous flow on Doppler. CT: deviation of the uterus to the twisted side, obliteration of fat planes and an enlarged ovarydisplaced from its adnexal location is seen. Contrast enhanced CT may show surrounding enhancing blood vessels due to congestion.

169. Hemorrhage into a corpus luteal or follicular cyst manifest with abrupt onset of pelvic pain. If the cyst ruptures, associated hemoperitoneum can be life threatening. On imaging, hemorrhagic ovarian cysts can mimic a variety of solid and mixed solid- cysticmasses. A fluid-fluid level may be present. On CT, high attenuation components are usually seen due to hemorrhage.

170. A CT predominantly cystic lesion. MRI. On MRI the hemorrhagic content will make endometrioma appear bright on T1-weighted images. On T1-fatsat images an endometrioma will remain bright. This in contrast to teratomas, that are also bright on T1 but dark on T1-fatsat images. On T2-weighted images endometriomas typically show 'shading'

171. Ovarian vein thrombosis Pregnancy increases the risk for venous thrombosis due to stasis, alteration in coagulation factors and by nearly tripling the diameter of the ovarian veins. In 90% of cases, the right ovarian vein is involved due to dextrotorsion of the uterus. OVT may be diagnosed by US, CT or MRI, however, CT is the modality of choice and demonstrates a low attenuation thrombus in lumen of ovarian vein

172. MRI IN ACUTE ABDOMEN

173. Although US is the first-line investigation for suspected appendicitis in a pregnant patient, MR imaging is better than CT as the second-line imaging modality when US results are nondiagnostic or equivocal. Although the safety of MR imaging to the fetus has not been proved, no proved human teratogenic or carcinogenic effects of MR imaging have been described in the literature.

174. ADNEXAL TORSION The suitability of MR imaging is equal to that of CT in patients in whom an adnexal lesion is believed to be present. according to the ACR criteria; however, in postmenopausal women with a complex or solid adnexal mass depicted at US, MR imaging is considered superior to CT. MR imaging and CT are used mainly when the presence of acute torsion with a pelvic mass is suspected or when the signs and symptoms are suggestive of a subacute or chronic condition.

175. The MR imaging features of ovarian torsion: which have been well described, include ovarian enlargement with stromal edema. The common CT and MR imaging features of adnexal torsion include thickening of the twisted fallopian tube, smooth thickening of the wall of the cystic ovarian mass, ascites, and uterine deviation to the side of torsion

176. PID

Acute abdomen

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