IMAGING OF ACUTE ABDOMEN Dr Rista D Soetikno

IMAGING OF ACUTE ABDOMEN Dr. Rista D. Soetikno, dr. , Sp. Rad (K), M. Kes

INTRODUCTION “Acute abdomen” is a term used to encompass a spectrum of surgical, medical and gynecological conditions (intraabdominal process), ranging from the trivial to the life threatening, which require hospital admission, investigation and treatment

Assesing the patient with an acute abdomen need many investigation including laboratory test and imaging studies plain photo, US, CT and contrast study.

Imaging studies Plain abdominal films: erect chest film, supine, and upright (optional: left lateral decubitus) Abdominal US Abdominal CT

Plain abdominal film Table 1 Plain abdominal film

Supine abdomen Looking for › Gas pattern › Calcifications › Soft tissue masses Substitute – none

Erect abdomen Looking for › Free air › Air-fluid levels Substitute – left lateral decubitus

Etiologies Hemorrhage GI perforation Bowel obstruction Inflammatory disorder Circulatory impairment

HEMORRHAGE Intraperitoneal hemorrhage › Rupture: hepatoma aortic anuerysm ectopic pregnancy ovarian bleeding

Gastrointestinal hemorrhage › Upper GI hemorrhage Duodenal ulcer Gastric ulcer Hemorrhagic gastritis Esophageal or gastric varices ect. › Lower GI hemorrhage Bleeding of colon cancer Ischemic colitis ect.

Imaging US finding › Free peritoneal fluid accumulation on the Morison’s pouch, the rectovesical pouch, the pouch of Douglas, and the bilateral subphrenic space Abdominal CT › CT gold standars for specific intraabdominal pathology

US

CT

Gastrointestinal perforation are serious disorder requiring rapid diagnosis and treatment Since they may be severe enough to produce septic or hypovolemic shock rapid decision-making for urgent laparotomy is crucially important

● Radiological appearances: Plain abdominal film: - Oval/linear collection of gas: ♠ Subhepatic space ♠ Morison’s pouch ♠ Beneath the diaphragm (the cupola sign) ♠ In the centre of the abdomen over a fluid collection (the football sign) ♠ Fissure for ligamentum teres 15

- Small triangular collections of gas between loops of bowel. - Visualisation of the outer as well as the inner wall of a loop of bowel (Rigler’s sign). US not as sensitive as plain radiography for demonstating pneumoperitoneum CT: Free gas over the liver, anteriorly in the mid abdomen, & in the peritoneal recesses. 16

Plain photo

Pneumoperitoneum Fissure for ligamentum teres Rigler’s sign 18

Football sign

BOWEL OBSTRUCTION The first investigation when bowel obstruction is suspected is the supine plain abdominal X-ray, together with an erect chest film if perforation is a possibility Occasionally, all the dilated bowel may be fluid fill and not visible on a plain X-ray and further imaging with contrast studies, CT or US may be needed to demonstrate dilated bowel

Imaging aims: to confirm the presence of bowel obstruction, define the level obstruction, identify the cause and detect complications such as perforation

Table 2. Cause of bowel obstruction Extrinsic Bowel wall Intraluminal Adhesions Neoplasia Intussusception Hernia Strictures: inflamma Foreign body tory, radiation, chemical Volvulus Intestinal ischaemia Inflammation/abscess Malignant infiltration (e. g. peritoenal deposits) Gallstone ileus

Small-Bowel Obstruction: Etiology: - Adhesions due to previous surgery - Strangulated hernias - Volvulus - Gallstone ileus - Intussusception - Neoplastic, etc.

Small bowel obstruction (SBO) Plain film primary investigation of choice Plain film of SBO: Dilated small bowel loops: › › › Tend to the central Numerous 2. 5 -5. 0 cm diameter Have a small radius of curvature Valvulae conniventes: thin, numerous, and extend right across the bowel › Do not contain solid faeces

Multiple fluid levels on the erect film String of beads sign on the erect film Absent or little air in the large bowel

SBO: valvulae conniventes

SBO: stepladder pattern

Small-Bowel Obstruction: String of beads sign 28

♥ Ultrasound: - Dilated fluid-filled loops of small-bowel obstruction. - Assessment of the peristaltic activity. 29

US: SBO

CT sign of SBO › Small bowel loops measuring>2. 5 cm in diameter › Identifiable focal transition zone from prestenotic dilated bowel to post-stenotic collapsed bowel loops

CT: SBO Fluid-filled loops Bowel calibre change

LARGE-BOWEL OBSTRUCTION Etiology: - Neoplastic (benign & malignant) - Volvulus (caecal & sigmoid), etc. Radiological appearances: Depends on the state of competence of the ileocaecal valve: 33

Large bowel obstruction (LBO) Plain-film signs of LBO: › Dilated large bowel loops which: Tend to be peripheral Few in number Large: above 5. 0 cm diameter Wide radius of curvature Haustra: thick and widely separated and may or may not extend right across the bowel (compare these features with the valvulae conniventes found in the small bowel Contain solid faeces

› Caecum maybe dilated › Small bowel may be dilated Contrast enema maybe helpful: › To differentiate pseudo-obstruction and may be indistinguishable on plain film from mechanical of obstruction › To localized the point of obstruction › To diagnose the cause of obstruction e. g. tumour, inflamatory mass

Contrast-enema

Plain film: Sigmoid volvulus coffee bean sign

Plain film: Caecal Volvulus

PARALYTIC ILEUS Generalised paralytic ileus: ●Etiology: - Peritonitis - Post-operative - Hypokalaemia - General debility or infection - Drugs: morphine - Congestive cardiac failure, renal colic, etc. ●Radiological appearances: - Both small & large-bowel dilatation - Horizontal-ray films: multiple fluid levels 39

PARALYTIC ILEUS 40

INFLAMMATORY DISSORDERS Acute appendicitis Acute pancreatitis Acute cholecystitis Abdominal absces Peritonitis

Acute appendicitis Abdominal x-ray (AXR) US › Non-specific finding › Approximately 10% a calcified appendicolith › Generally, the normal cannot be defined with US, clear visualization of the appendix is suggestif of inflammation › Swollen, non compressible appendix greater than 7 mm in diameter with a target or bulls-eye configuration is produced by the hypoechoic dilated appendiceal lumen › Assymetrical wall thickening due to phlegmonous infiltration, an appendicolith with acoustic shadowing

US finding › Echogenic hallo form by omental tissues draped over the appendix › Free fluid in the culdesac › Atony in the terminal ileum with compression US

CT finding › 90% diagnostic accuracy to detect acute appendicitis › With the good contrast filling of the terminal ileum and the cecum (oral contrast given 1 hour before examination) › Tubular structure 4 mm to 20 mm in diameter with a thickened wall that enhance after administration IV contrast medium › Pericecal fluid collection and calcified appendicolith

Plain film: apendicolith

CT

Acute pancreatitis Severity of acute pancreatitis ranges mild edema with minimal symptoms to a severe necrotizing process that culminates in multiple organ failure US and CT most precisely define the anatomic extent of the lesions and the detect local complications

Imaging Plain films no significant plain film findings in up to two-thirds of patients wih acute pancreatitis Plain-film signs may include: › › Paralytic ileus in the left upper quadrant Generalized ileus Loss of left psoas outline Separation of greater curve of stomach from tranverse colon

CXR signs that may be seen include: › Left pleura effusion › Atelectasis of left lower lobe › Elevated left hemidiaphragm

US finding: › The acutely inflamed pancreas enlarged with decreased echogenicity and blurred irregular margin › Fluid collection are seen as hypoechoic areas › US can be used to guide aspiration and the drainage procedures, and for follow up

CT imaging investigation of choice for acute pancreatitis, and is particularly useful for the following: › › Confirmation of the diagnosis Identification of necrotic gland tissue Diagnosis of complication Guidance of interventional procedures CT signs of acute pancreatitis include: › Diffuse or focal pancreatic enlargement with decreased density and indistinct gland margins › Thickening of surrounding fascial planes e. g. left paranephric fascia

› Acute fluid collections, most commonly related to pancreas though also in the lesser sac and in the left pararenal space › Phlegmon appears as an irregular mass spreading along fascial planes and can be quite extensive › Abscess › Pseudocyst

US

CT

Acute cholecystitis Approximately 85%-90% of cases with acute cholecystitis (AC) develop as a complication of cholelithiasis Conversely, approximately 10%-20% of patients with gallstone will require surgery for complication, usually cholecystitis, within 15 years after their stone disease is diagnosed Acalculous cholecystitis account for 5%-15% of cases of acute cholecystitis (immunocompromize, critically ill, iatrogenic, congenital etc)

Imaging Plain films insensitive for acute cholecystitis Plain films sign nonspesific and include: › Gallstone (only seen in 10%) › Soft tissue mass in the right upper quadrant due to distended gallbladeer › Paralytic ileus in the right upper quadrant

Imaging US investigation of choice for suspected acute cholecystitis US signs of acute cholecystitis include: › Gallstones: hyperechoic lesions with acoustic shadowing which are mobile › Thickening of gallbladder wall to greater than 4 mm › Hypoechoic gallblader wall due to oedema › Surrounding fluid or localized fluid collection › Distended gallbladder › Localized tenderness to direct probe pressure

CT scanning contribute little to diagnosis of cholecystitis CT investigation of complicatios biliary or pericholecystic abscess

US: Acute cholecystitis

US: Acute cholecystitis

US: Acute cholecystitis

Peritonitis an inflammatory or suppurative reaction of the peritoneum to direct irritation Cause: › Inflammatory › Infectious › Ischemic Exudation, Hematogenous, Contiguous extension, Iatrogenic manipulation

Imaging Plain abdominal radiograph: cannot provide specific › › › Air-fluid Levels Stones Ascites Eggshell calcification Air in Biliary tree. Obliteration of psoas-shadow in retro- peritoneal disease › Right lower quadrant sentinel loops in acute appendicitis

US nonspecific Abdominal CT › CT signs Ascites (free or encapsulated) Infiltration of the omentum and/or mesentery Thickening of the parietal peritoneum Angiography for ischaemia, hemorrhage

ACUTE COLITIS Acute inflammatory colitis • Toxic megacolon • Pseudomembranous colitis • Ischaemic colitis • 66

Acute inflammatory colitis Plain film can assess : ♠ the extent of the colitis ♠ the state of mucosa: It can be assessed from : - the faecal residue: In left-sided disease, the proximal limit of faecal residue will indicate the extent of active mucosal lesion. - the width of the bowel lumen - the mucosal edge - the haustral pattern 67

Toxic megacolon A fulminating form of colitis with transmural inflammation, extensive & deep ulceration & neuromuscular degeneration. Involve the transverse colon Ro. Findings: Mucosal islands (=pseudopolyps) & dilatation (8 cm) Common complication: Perforation in the sigmoid & peritonitis 68

Toxic megacolon 69

Ischaemic colitis Etiology: Vascular insufficiency & bleeding into the wall of the colon. Sudden onset of severe abd. pain in the early hours of the morning, followed by bloody diarrhoea. In middle-aged & elderly patients. The wall of splenic flexure & descending colon is greatly thickened→ thumb printing (plain films). The right side of colon is frequently distended. 70

Pathophysiology of mesenteric ischaemia

Ischaemic colitis thumb printing 72

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