Approach to Abdominal

Radiographs

Tapas K. Tejura, M.D.

Assistant Professor of Clinical Radiology

Keck Medical Center of USC

tapas.tejura@med.usc.edu

No Disclosures

34-year-old male

with acute

abdominal pain

• Normal

obstruction

series

• Now what?

• Multiple studies

have found the role

of abdominal

radiography to be

limited in the adult

emergency

department setting

• Retrospective study of 1000 consecutive patients with

abdominal pain in Emergency Department (ED)

• 871 had abdominal radiographs

– 23% normal

– 10% abnormal (bowel obstruction, urolithiasis, ileus, foreign

body, gallstones)

– 68% nonspecific

• 188 had abdomen computed tomopgrahy (CT) scan

– 20% normal

– 80% had specific diagnosisAhn, et al. Radiology 2002

• Prospective study of 91 patients

• All had unenhanced CT and three-view abdominal series

• Abdominal Series Unenhanced CT

– 30.0% sensitivity - 96.0% sensitivity

– 87.8% specificity - 95.1% specificity

– 56.0% accuracy - 95.6% accuracyMacKersie, et al. Radiology 2005

• Retrospective study of 874 patients with

abdominal pain in ED

– 34% normal, 46% nonspecific, and 19% abnormal

– Normal results led to additional imaging (CT, US,

upper GI) in 42% of patients

– 72% of patients with normal abdominal radiographic

findings had abnormal findings on further imaging

Kellow, et al. Radiology 2008

“With the exception of catheter placement assessment, this

study suggests that the appropriate work-up of a patient

presenting to the emergency department with abdominal

symptoms (without a history of trauma) should not include

radiographic imaging. Rather, if the patient requires

investigation beyond the clinical history, physical

examination, and lab results, the emergency physician

should be encouraged to immediately request more definitive

imaging techniques.”

Kellow, et al. Radiology 2008

• Abdominal radiographs frequently obtained as

initial imaging examination for evaluation of

acute abdominal pain

• Most common indications in ED:

– Bowel obstruction

– Renal colic

– General abdominal pain

• ED physicians did not seek advanced imaging

following normal abdominal radiograph

interpretation 20% of the time

Kellow, et al. Radiology 2008

Role for abdominal radiography

• Catheter placement

• Foreign Bodies

• Bowel perforation

• Acute bowel obstruction

• History of kidney stones, evaluate

change in position

Role for abdominal radiography Technique

Sandström S, Ostensen H, Pettersson H et al. The WHO Manual of Diagnostic Imaging,

Radiographic Technique and Projections. Diamond Pocket Books (P) Ltd.; 2003.

SupineAnterior-posterior (AP)Left lateral

decubitus

Radiation Dose

Mettler FA, Huda W, Yoshizumi TT, Mahesh M. Effective doses in radiology and diagnostic

nuclear medicine: a catalog. Radiology. 2008;248(1):254-63.

Search Pattern

• Demographics

• Technical assessment

• Systematic review

– Implanted devices/catheters

– Stomach and bowel gas pattern

– Organs (liver, spleen, kidneys, urinary bladder)

– Abnormal calcifications

– Bones and soft tissues

Liver

R Kidney L KidneySpleen

Psoas muscles

Implanted Devices/Catheters

and Foreign Bodies

Nasogastric / Orogastric tube

• Can be used for feeding, gastric sampling,

gastric decompression, and medication

administration

• Tip and sideport should be in stomach

– Sideport can extend up to 10 cm from tip of the tube

• Commonly malpositioned

– Can enter trachea or curl up in esophagus

• Indewlling tube can lead to gastroesophageal

reflux and cause esophagitis and stricture

Dobhoff Tube

• Typically used for nutrition

• Weighted, radiodense tip

• Tip should be in 2nd or 3rd portion of the

duodenum

– Most are in the stomach

• If tip located proximal to gastroesophageal

junction, can lead to aspiration

Gastrostomy tube

• Can be of varying length and appearance

• Should be overlying the expected location

of the stomach

• An inflated balloon tip may be seen,

preventing the tube from pulling out

• Intraluminal position can be confirmed

with contrast administration

Other Implanted Devices

Foreign Bodies

• Many foreign bodies, including glass,

metal, and stone are radiopaque and can

be detected on plain film

• CT is more sensitive to detect foreign

bodies surrounded by air (ie; in bowel)

Bowel Gas Pattern

Normal Gas Pattern

• Stomach

– Almost always has air

• Small Bowel

– Normal diameter ~ 3 cm

• Large Bowel

– Almost always has air in rectum

or sigmoid

– Normal diameter ~ 6 cm

– Cecum up to ~ 10 cm

• Distention vs. Dilatation

– Bowel containing sufficient amount of

air to fill lumen completely

– Bowel filled beyond normal size

Distinguishing Large and Small

Bowel

• Large Bowel– Peripheral

– Haustral folds usually do not extend across lumen

• Small Bowel– Central

– Valvulae conniventes usually extend across lumen

– Spaced more closely

Air-Fluid Levels

• Can be seen on

upright views

• Stomach

– Almost always

• Small Bowel

– No more than 2 or 3

levels

– Should be < 3 cm long

• Large Bowel

– Usually none

Abnormal Bowel Gas Patterns

• Ileus

• Small and large bowel obstruction

• Volvulus

• 3 Questions:

1) Is there gas in the rectum or sigmoid colon?

2) Are there dilated segments of small bowel?

3) Are there dilated segments of large bowel?

Abnormal Bowel Gas Patterns

• Generalized ileus

– Dilated small AND large bowel

• Localized ileus (sentinel loop)

– Several persistently dilated segments of large or small

bowel

– Gas in rectum/sigmoid

• Mechanical small bowel obstruction

– Dilated small bowel with little/no gas in large bowel

• Mechanical large bowel obstruction

– Dilated small and large bowel

Generalized Ileus

• Refers to disruption in the normal coordinated

propulsive motor activity of the gastrointestinal tract in

the absence of a mechanical bowel obstruction

– Suggests that the muscle of the bowel wall is transiently

impaired and fails to transport intestinal contents

– Lack of coordinated propulsive action leads to the accumulation

of both gas and fluids within the bowel

• Common causes:

– Surgery

– Inflammation

– Neural

– Metabolic

Generalized Ileus

• Radiographic features

– Generalized, uniform, gaseous distension of

both the large and small bowel

– No discrete transition point to decompressed

distal segments of bowel

Localized Ileus

• Can be the result of an adjacent

inflammatory or infectious process

• Focal cluster of 1-3 distended and/or

mildly dilated segments of small bowel

• Termed “sentinel loops”

• Location can help suggest underlying

etiology

Appendicitis

Pancreatitis

UlcerCholecystitis

Diverticulitis

Localized Ileus

Small Bowel Obstruction (SBO)

• Common clinical condition that occurs secondary to mechanical or functional obstruction of the small bowel

• Represents 20% of all surgical admissions for acute abdominal pain

• Proximal dilatation of the intestine due to accumulation of gastrointestinal secretions and swallowed air

• Bowel distal to the point of obstruction empties over time

Small Bowel Obstruction

• Eventually leads to increased intraluminal pressures – Causes compression of mucosal lymphatics

• Microvascular changes in the bowel wall allow translocation of gut bacteria to mesenteric lymph nodes– Increase in incidence of bacteremia due to E. coli

Mortality and morbidity are dependent on the etiology, the early recognition and correct

diagnosis of obstruction

Diagnosis of Small Bowel

Obstruction• Small bowel diameter > 2.5 cm (usually > 3

cm)–KEY: Disproportionate dilatation of small bowel

• Gas-fluid levels > 2.5 cm wide and at different levels

• “Small bowel feces” sign - Often seen near transition point

• Relative paucity of gas in the colon–Presence of residual colonic gas after 6-12 hours is

suggestive of partial SBO

• Early SBO may resemble ileus – need follow-upLappas et al. AJR 2001; 176:167-174

May-Smith et al. Clin Radiol 1995; 50:765-767

Causes of Small Bowel Obstruction

• Extraluminal

– Adhesions

– Hernias

– Volvulus

• Intramural

– Crohn’s disease

– Tumor

– Radiation

– Hematoma

• Intraluminal

– Foreign bodies

– Gallstones

– Inspissated meconium

SBO DDx: Adhesions,

Bulges, Crohn’s, Cancer

“Gasless Abdomen”

• Refers to little or no bowel gas

• This is nonspecific and can be seen in a

variety of etiologies

• Clinical history plays a key role in

distinguishing between benign and

threatening etiologies

Diagnosis of Large Bowel

Obstruction

• Dilated segments of colon to the point of obstruction

• Little or no gas in the rectum/sigmoid colon

• Little or no gas in the small bowel (assuming competent

ileocecal valve)

Causes of Large Bowel

Obstruction

• Tumor, tumor, tumor….

• Diverticulitis/stricture

• Hernia

• Volvulus

• Intussusception

Volvulus• Sigmoid

– More common in older patients

– Surgical emergency, as can lead to colonic

strangulation and bowel necrosis

– Classic findings include “coffee bean” or inverted “U”

appearance of sigmoid colon

– Distal large bowel obstruction

• Cecal

– Less common than sigmoid

– Displacement of massively dilated cecum away from

right lower quadrant

– Proximal large bowel obstruction• Can lead to small bowel dilatation

1 limb 1 limb

Coffee Bean

Ogilvie Syndrome / Acute

colonic Pseduo-obstruction• Refers to clinical picture of large bowel

obstruction without any demonstrable

evidence of mechanical obstruction

• Risk factors

– Medications which decrease motility

– Recent surgery

– Infection

– Debilitation

• High mortality rate if perforation occurs

Constipation and Fecal

Impaction• Clinical diagnosis that cannot be made on

imaging alone

• Be aware of fecal impaction, typically

referring to large obstructing mass of

hardened stool in the distal colon or

rectum that can occur in the setting of

constipation

• Fecal impaction can lead to stercoral colitis

and perforation

Normal Haustral Folds

• Normally are ~3-4

mm in thickness

• Thickened haustral

folds can be seen on

radiographs

• Etiologies include

inflammatory bowel

disease, infectious

colitis, hematoma,

ischemia

“Lead pipe” Colon

• Term used to describe complete loss of

normal haustration

• Presumably due to alterations in muscle

tone of the teniae coli from chronic

inflammation

• Reflects burned-out disease

Toxic Megacolon

• Life threatening condition characterized by

severe colonic dilatation without

obstruction in the setting of systemic

toxicity (fever, tachycardia, leukocytosis)

• Most often seen in infectious or

inflammatory bowel disease

Pathologic Gas

Pathologic Gas

• Pneumoperitoneum

• Pneumoretroperitoneum

• Pneumatosis

• Portal venous gas

• Emphysematous pyelpenphritis, cystitis, or

cholecystitis

Erect view

• Looking for

– Pneumopertioneum

– Air-fluid levels

• Substitute

– Left lateral decubitus

How Sensitive?

• Plain films can be 85% sensitive for free air

• Theoretical threshold is 1 mL

• CT is much more sensitive and is

considered the “Gold Standard”

• Best views

– Erect chest and left lateral decubitus abdomen

– Supine abdomen is insensitive

Miller, et al. Am J Roentgenol Radium Ther Nucl Med 1971

Roh, et al. Am J Surg, 1983

Signs for pneumoperitoneum

• Rigler’s – visualization of air on both sides

of the bowel wall

• Flaciform ligament – appearance of a

linear opacity from the liver to the mid-

abdomen

• Double bubble – subdiaphragmatic gas

outlining the wall of the stomach and

diaphragm

Extraluminal Air

• Spontaneous Pneumoperitoneum

– Gastric or duodenal ulcer perforation

– Colonic perforation

• Diverticulitis

• Appendicitis

• Cancer

– Other causes

• Thoracic disease (pneumothorax, pneumomediastinum)

• Iatrogenic

Post-operative

Pneumoperitoneum

• Usually presents 3-7 days

• When to worry?

– When volume of air increases over time

– Erect view can be used to evaluate quantity of air

Pneumatosis

• Can occur in variety of conditions,

including bowel ischemia, iatrogenic,

chemotherapy, collage vascular disease,

and chronic obstructive pulmonary disease

• Concomitant presence of gas in the portal

venous circulation is suspicious for bowel

ischemia

Pneumoretroperitoneum• Sites of origin

– Duodenum

– Ascending colon

– Descending colon

– Rectum

• Look for

– Linear air along

margins of psoas

muscle

– Gas surrounding

kidneys

– Gas under medial

surface of diaphragm

Abscess

• Small bubbles/collections of air

• Straight or triangular margins of air collections

• Unusually large collections of air

Soft Tissue Masses

• Hepatosplenomegaly

• Mass (tumor, abscess, cyst, aneurysm,

bladder)

– Bowel displacement

– Paucity of gas

– Focal region of increased density

– Extrinsic compression of bowel

Plain film diagnosis of ascites

• Gray abdomen: diffuse increase density

• Indistinct margins liver, spleen, psoas

• Medial displacement of colon, liver and

spleen away from properitoneal stripe

• Bulging flanks

• Separation of gas-filled small bowel loops

ASCITES NORMAL

Calcification Patterns

• Rimlike

• Linear or track-like

• Lamellar

• Amorphous

Rimlike Calcification

• Hollow viscus wall

– Cysts

– Aneurysms

– Saccular organs

• Porcelain gallbladder

Linear or Track-like

• Walls of a tube

– Ureters

– Arterial walls

– Vas Deferens

Lamellar

• Formed in lumen of a hollow viscus

– Renal stones

– Gallstones

– Bladder stones

Amorphous, Cloudlike Popcorn

• Formed in solid organ

or solid mass

– Leiomyomas of uterus

– Chronic pancreatitis

– Lymph nodes

Summary

• Abdominal radiographs are often the first

imaging examination performed in patients with

abdominal pain

• Understand role of abdominal radiographs in

clinical management of patients

• Recognize range of abdominal radiograph

findings, including Implanted devices/catheters,

bowel gas patterns, pathologic gas, abdominal

organs, and calcifications

Thank You