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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
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
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
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.
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
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