Acute Abdomen Poto

8/2/2019 Acute Abdomen Poto

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Acute Abdomen - A Practical Approach

Adriaan van Breda Vriesman and Robin Smithuis

Radiology department of the Rijnland Hospital, Leiderdorp, the Netherlands

Radiological strategy

Clinics, laboratory, and plain abdominal film

Confirm or exclude the most common disease

RLQ : Appendicitis

LLQ : Diverticulitis

RUQ : Cholecystitis Screen for general signs of pathology

Inflamed fat

Bowel wall thickening

Ileus

Ascites Free air

Differential diagnosis

Mesenteric lymphadenitis.

Bacterial ileocecitis

Right-sided diverticulitis

Salphingitis

Epiploic appendagitis.

Urolithiasis

Ruptured Aneurysm

Pancreatitis

back to overview print

Publicationdate:20-10-2005

The 'acute abdomen' is aclinical condition

characterized by severe

abdominal pain, requiring theclinician to make an urgent

therapeutic decision.

This may be challenging,because the differential

diagnosis of an acute abdomen

includes a wide spectrum of

disorders, ranging from life-threatening diseases to benign

self-limiting conditions (Table

1).Indicated management may

vary from emergency surgery

to reassurance of the patientand misdiagnosis may easily

result in delayed necessary

treatment or unnecessarysurgery.Sonography and CT enable an

accurate and rapid triage of

patients with an acuteabdomen.

We present practical

guidelines on the radiologicalapproach of these patients.

Interactive cases are presented

in the menubar to test your

knowledge.

If you encounter printing

problems with the margins ofthe document, try to adjust the

margins or the scale of the

document in the print settings. Radiological strategy
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Table 1. Common causes of acute abdomen from life-threatening to

self-limiting.

Before you perform an

examination, obtain relevantinformation from the referring

clinician.

Don't let the clinician simply'order' a sonogram or CT, but

discuss the patient's age and

posture, laboratory results andthe number one clinical

diagnosis and differential

diagnosis.

Based on that information andyour own degree of

confidence with the modalities

decide for yourself whether to

perform sonography or CT.Sonography has the advantage

of close patient contact,enabling assesment of the spot

of maximum tenderness and

the severity of illness withoutionizing radiation.

In general the diagnostic

accuracy of CT is higher than

sonography.In patients with inconclusive

US-results, CT can serve as an

adjunct to sonography, andvice versa.

We advocate the following

two-step radiological approachof an acute abdomen.

1. Confirm or exclude the

most common disease

2. Screen for general signs ofpathology

You have to be familiar with

all the diagnoses listed inTable 1 to be able to recognize

them.Clinics, laboratory, and plain

abdominal film


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The clinical presentation of

patients with an acute

abdomen is often nonspecific.Both surgical and nonsurgical

diseases may present with a

similar clinical history andsymptoms.

Laboratory findings (leucocyte

count, erythrocytesedimentation rate, CRP) are

equally nonconclusive.

Findings may be normal in

patients who need emergencysurgery (such as appendicitis)

and may be abnormal in

patients without a surgical

disease (like salpingitis).A plain abdominal film has a

limited value in the evaluationof abdominal pain.

A normal film does not

exclude an ileus or otherpathology and may falsely

reassure the clinician.

LEFT: Plain abdominal film in a patient with an acute abdomen,

showing no abnormalities.RIGHT: Subsequent CT shows distended small bowel loops

(arrowheads) that are not seen on plain abdominal film because they

are filled with fluid only and do not contain intraluminal air.

An ileus may not be

appreciated on a plainabdominal film if bowel loops

are filled with fluid only

without intraluminal air(figure).

Alternatively if a plain

abdominal film does indicatean ileus than sonography or

CT are usually needed to

identify its cause.

Thus, a plain abdominal filmis seldomly useful, with the

exception of detection of

kidney stones or apneumoperitoneum.

For all other indications use

sonography or CT.

Confirm or exclude the mostcommon disease


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Many disorders may cause an

acute abdomen, but

fortunately only a few of theseare common and clinically

important.

Focus on confirming orexcluding these frequent

disorders:RLQ : Appendicitis

Pain in the RLQ, regardless of

any other symptom or

laboratory results, should beconsidered to be appendicitis

until proven otherwise.

If you are unable to find theappendix you cannot rule out

the diagnosis of appendicitisunless a good alternative

diagnosis is found.If you do not find the

appendix and there is no

altermative diagnosis call theresults of the examination

indeterminate. Do not call it:'

no appendicitis'.

Normal appendix : Longitudinal (A) sonogram depicts a blind-

ending tubular structure (arrowheads) with 'gut-signature', with amaximum outer diameter of 6 mm, with noninflamed surrounding

fat. On an axial view (B) the appendix can be compressed crossingthe iliac vessels.

Normal Appendix.

Your first task is to identify

the appendix.At sonography and CT theappendix is seen as a blind-

ending nonperistaltic tubular

structure arising from the baseof the cecum.

Do not mistake a small bowel

loop for the appendix.Secondly determine if the

appendix is normal or

inflamed.

The outer-to-outer diameter ofthe appendix is the most

important imaging criterium.

Although an overlap ofappendiceal diameters in

normal and inflamed

appendices can incidentally befound, a threshold value of 6-7


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mm is generally used.

Normal appendix: CT shows an air-containing non-distended

appendix (arrowheads), with homogeneous low-density

periappendiceal fat.

A normal appendix has a

maximum diameter of 6 mm,is surrounded by

homogeneous non-inflamed

fat, is compressible and oftencontains intraluminal gas.

Inflamed appendix at sonography. Longitudinal (A) and transverse

(B) cross-section show a distended noncompressible appendix,

surrounded bij hyperechoic inflamed fat (arrowheads).

Inflamed AppendixAn inflamed appendix has a

diameter larger than 6 mm,

and is usually surrounded byinflamed fat. The presence of

a fecolith or hypervascularity

on power Doppler stronglysupports inflammation.

Inflamed appendix at CT. The appendix (arrows) is fluid-filled and

distended with periappendiceal fat-stranding.

CT depicts an inflamed

appendix as a fluid-filled

blind-ending tubular structuresurrounded by fat-stranding.

In the case on the left a hyper-

attenuating wall is seen on theenhanced CT.

In patients who lack intra-

abdominal fat the use of iv.contrast can be helpfull in

depicting the inflamedappendix.


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Sigmoid diverticulitis at sonography. A hypoechoic thickeneddiverticulum is surrounded by hyperechoic inflamed fat (arrows).

LLQ : Diverticulitis

If the pain is located in theLLQ your main concern is

sigmoid diverticulitis.

In diverticulitis sonography

and CT show diverticulosiswith segmental colonic wall

thickening and inflammatory

changes in the fat surroundinga diverticulum.

Uncomplicated sigmoid diverticulitis. Fat stranding and focalthickening of the colonic wall in an area with diverticula. No

abscess formation.

Complications of diverticulitis

such as abscess formation orperforation, can best be

excluded with CT.


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LEFT: Sigmoid diverticulitis. Diverticulum (arrow) is surroundedby hyperattenuating fat. The sigmoid wall is thickened.

RIGHT: Sigmoid carcinoma with limited fat stranding.

An important pitfall is colon

cancer, which may present

with similar imaging features,especially when the colon

cancer is surrounded by fat

stranding due to invasivegroth, desmoplastic reaction or

inflammation.

Frequently it is not possible toreliably distinguish

diverticulitis from colon

cancer and therefore we

routinely include colon cancerin the differential diagnosis of

sigmoid diverticulitis.RUQ : Cholecystitis

Cholecystitis occurs when acalculus obstructs the cystic

duct. The trapped bile causesinflammation of the

gallbladder wall.

As gallstones are often occulton CT, sonography is the

preferred imaging method for

the evaluation of cholecystitis,also allowing assesment of the

compressiblity of the

gallbladder.The diagnosis of a hydropicgalbladder is solely made on

the non-compressability of the

galbladder. Do not rely onmeasurements. Some

galbladders happen to be small

and others are large.The imaging appearance of

cholecystis consists of an

enlarged hydropic (meaning

non-compressible) gallbladderwith a thickened wall in the

region of maximum tenderness

(the so-called 'Murphy sign')


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Longitudinal and transverse US show thickened gallbladder wall.

The gallbladder is noncompressible ('hydropic') and causes an

impression in the anterior abdominal wall (arrowheads).

Cholecystitis at CT. The gallbladder is enlarged with edematous

thickening of its wall (arrowhead), and some regional fat-strandingcan be found.

The inflamed gallbladder

usually contains stones orsludge, whereas the

obstructing calculus itself mayor may not be identified

because it is located deep

within the galbladder neck orcystic duct.

The gallbladder may be

surrounded by inflamed fat,but on sonography this

frequently is not seen, while

CT sometimes does show fat-stranding.

Potential pitfalls are

pancreatitis, hepatitis or right-

sided heart failure, which allmay lead to thickening of the

gallbladder wall without

cholecystitis.Therefore be certain that

hydropic obstruction of the

gallbladder is present before

assigning the diagnosis ofcholecystitis.

Pain in LUQ

An acute abdomen with LUQpain is rare.

Its most common cause is

gastric pathology in whichradiological imaging plays a

minor role.Screen for general signs of

pathology

After excluding these frequentdisorders, search for signs of

any other pathology, by

systematically screening thewhole abdomen.

Look for inflamed fat, bowel

wall thickening, ileus, ascites

and free air.


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Inflamed fat at sonography. Extended-view of the ventral abdomen

depicting an area of hyperechoic noncompressible inflamed fat inthe omentum (red arrows). Compare this to the echogenicity of

normal abdominal or subcutaneous fat (green arrows). This patient

had an omental infarction.

Inflamed fat

Inflamed fat is hyperechoic,space occupying and

noncompressible at

sonography.

Same patient as above. Unenhanced CT depicts an area of fatty

tissue with slightly increased density (arrowheads), in the right-upper quadrant. Compare this to normal low-density subcutaneous

fat. Diagnosis: omental infarction.

Inflamed fat is shown as fat-

stranding at CT. Inflamed fat

usefully points out where and

what the problem is.As a rule, the organ or

structure in the centre or

nearest to the inflamed fat isthe cause of the inflammation.


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Diffuse thickening of bowel wall in a patient with colitis.

Bowel wall thickening

Thickening of bowel wallindicates inflammation or

tumor, and has an extensive

differential diagnosis.

Thickening of small bowelloops usually indicates

regional inflammation, as

small bowel tumors(carcinoid, lymphoma, GIST)

are relatively infrequent.

In patients with local colonicwall thickening a carcinoma is

a prime concern.

Obstructive ileus. CT depicts distended small bowel loops, but partof the small bowel and the whole colon is nondistended. Therefore

this must be an obstructive small bowel ileus, and in this case its

cause can easily be identified: intussusception (arrowhead).

Ileus

Pathologic distention of bowelloops may be caused by

obstruction or paralysis.Firstly determine which parts

of the gut are affected: small

bowel, large bowel, or both.Look for normal nondistended

bowel loops, which, if present,

strongly suggest an obstructive

cause for the ileus.

View more images: 3/4

Small bowel obstruction

(SBO) accounts for

approximately 4% of all

patients presenting with anacute abdomen.

The diagnosis of SBO is made

when you see dilated small

bowel and collapsed smallbowel loops.

If obstruction is present, try toidentify its cause and location

(adhesion, tumor, volvulus,

intussusception, inguinal

hernia).Adhesions account for 60-80%
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Scroll through the images

Small Bowel Feces Sign: Feces in the dilated small bowel just

proximal to the site of obstruction.Obstruction was due to adhesions

of all cases and are the likely

cause when a smooth

transition from dilated tocollapsed small-bowel loops is

noted.

The 'Small Bowel Feces Sign'

(SBFS) is a very useful sign asit is seen at the zone of

transition thus facilitating

identification of the cause ofthe obstruction.

The SBFS has been defined as

gas and particulate materialwithin a dilated small-bowel

loop that simulates the

appearance of feces.Scroll through the images on

the left to see the small bowel

feces sign indicating the site of

obstruction.Alternatively, an ileus without

any normal bowel loops

strongly suggests a paralyticcause.

This is usually a response to

general peritonitis, wich may

have many possible causes ofthe inflammation.


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Clinically appendicitis. US only showed a little bit of ascites. A

diagnostic puncture (arrow marks needletip) revealed blood. In awoman this finding is very suspicious of an EUG.

Ascites

Asymptomatic volunteers donot have a detectable amount

of free intraperitoneal fluid,

with the exception of an

incidental drop of fluid inDouglas in fertile women.

The presence of ascites is a

nonspecific sign of abdominalpathology, indicating that

'something is wrong'.

You may want to perform aUS-guided diagnostic

puncture of the ascites, in

order to investigate whether itis sterile reactive fluid, pus,

blood, urine, or bile.

Intraperitoneal air in a patient suspected of having appendicitis. Airbetter seen on images with lungsetting on the right.

Free air

The presence of free

intraperitoneal air is proof ofbowel perforation, and

indicates a surgicalemergency.

A pneumoperitoneum has only

two frequent causes:

- Perforation of a gastric ulcer

- Perforation of colonic

diverticulitis

Free air is usually not seen inperforated appendicitis).

Always examine the images in

lungsetting for better detection

of free intraabdominal air(figure).

Differential diagnosis


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A complete list of all possible

causes of an acute abdomen is

of little use in daily practice,therefore we just provide some

imaging examples of several

frequent causes of acuteabdominal pain

US shows enlarged mesenteric lymph nodes in the right lower

quadrant, with no other abnormalities

Mesenteric lymphadenitis.

Mesenteric lymphadenitis is acommon mimicker of

appendicitis.

It is the second most commoncause of right lower quadrant

pain after appendicitis.

It is defined as a benign self-limiting inflammation of right-

sided mesenteric lymph nodeswithout an identifiable

underlying inflammatoryprocess, occurring more often

in children than in adults..

This diagnosis can only bemade confidently when a

normal appendix is found,

because adenopathy alsofrequently occurs with

appendicitis.

Key finding:Lymphadenopathy with anormal appendix and normal

mesenteric fat.

On the left a CT of mesentericlymphadenitis in a child

suspected of appendicitis.


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Normal appendix (green arrow) and enlarged mesenteric

lymphnodes (yellow arrows).

US typically shows submucosal wall thickening (arrowheads) of the

terminal ileum and cecum without inflammation of the surroundingfat.

Bacterial ileocecitis

Infectious enterocolitis may

cause mild symptoms

resembling a common viralgastroenteritis, but it may also

clinically present with features

indistinguishable fromappendicitis especially in

bacterial ileocecitis, caused by

Yersinia, Campylobacter, or

Salmonella.

Key finding: ileocecal wall

thickening without inflamedfat, adenopathy, normal

appendix

CT shows an inflamed cecal diverticulum (arrowhead) withregional colonic wall thickening.

Right-sided diverticulitis

Right-sided colonic

diverticulitis may clinicallymimic appendicitis or

cholecystitis, though thepatient's history is generally

more protracted.

In contrast to sigmoiddiverticula, right-sided colonic

diverticula are usually true

diverticula, that is,outpouchings of the colonic

wall containing all layers of

the wall.This may possibly explain the

essentially benign self-

limiting character of right-

sided diverticulitis.


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Enlarged adnex due to salpingitis

Salphingitis

Salphingitis is a commonmimicker of both of

appendicitis and diverticulitis.

Transvaginal sonography

depicts an inhomogeneousenlarged inflamed ovary.

CT characteristic of epiploic appendagitis with a right-sided fatty

mass surrounded by a hyperattenuating ring.

Epiploic appendagitis.

Epiploic appendages are small

adipose protrusions from the

serosal surface of the colon.

An epiploic appendage mayundergo torsion and secondary

inflammation causing focal

abdominal pain that simulatesappendicitis when located in

the right lower quadrant or

diverticulitis when located in

the left lower quadrant.The characteristic ring-sign

corresponds to inflamedvisceral peritoneal lining

surrounding an infarcted fatty

epiploic appendage.

Epiploic appendagitis has beenreported in approximately 1%

of patients clinically suspected

of having appendicitis.It is very important to make a

positive diagnosis of thischaracteristic entity sinceepiploic appendagitis is a self-

limiting disease.

Both US and CT will depict an

inflamed fatty mass adjacentto the colon.


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Left sided epiploic appendagitis in patient clinically suspected of

having a diverticulitis.

Characteristic hyperattenuating ring sign.

Key finding: inflamed fatty

mass adjacent to the colon

with characteristic ring sign.

Small stone in right ureter (arrow) causing right flank pain.

Urolithiasis

Urolithiasis often causes flank

pain, but an ureteral stone(arrowhead) may occasionally

present with clinical signs

simulating appendicitis,cholecystitis or diverticulitis.

Appendicitis on the other hand

may cause hematuria, pyuria

and albuminuria in up to 25%of patients because of ureteral

inflammation from an adjacent

inflamed appendix.

Left retroperitoneal fluid collection due to ruptured aneurysm.

Ruptured Aneurysm

Most abdominal aortic

aneurysms rupture into the left

retroperitoneum (4).Clinically this may simulate

sigmoid diverticulitis or renal

colic due to impingement ofthe hematoma on adjacent

structures.

However most patient willpresent with the classic triad

of hypotension, a pulsating

mass and back pain.Continuous leakage will lead

to rupture into the peritoneal

cavity and eventually death.

Sonography is a quick and

convenient modality, but it ismuch less sensitive and

specific for the diagnosis ofaneurysmal rupture than CT.

The absence of sonographic

evidence of rupture does notrule out this entity if clinical

suspicion is high.


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Pancreas surrounded by fat stranding due to exsudative pancreatitis.

Pancreatitis

CT depicts fat-stranding(arrowheads) surrounding the

primary focus of the

inflammation: the pancreas.

Conclusion

In patients with an acuteabdomen 'the stakes are high'.

A misdiagnosis may have

serious consequences. Weadvocate a systematic

approach:

1. First focus on the most

common diseases and make afirm diagnosis or exclude

them.

2. Always screen the wholeabdomen for general signs of

pathology.

References

1. A prospective study of ultrasonography in the diagnosis of appendicitisJB Puylaert et al; NEJM Volume 317:666-669

2. Signs in Imaging, The Hyperattenuating Ring Sign

Adriaan C. van Breda Vriesman et al ; Radiology 2003;226:556-557

3. Frequency and Relevance of the 'Small-Bowel Feces' Sign on CT in Patients with Small-

Bowel Obstruction

Dawn E. Lazarus et al, AJR 2004; 183:1361-1366

4. Abdominal Aortic Aneurysm, Rupture in eMedicine

by Walter A Tan, MD, MS and Michel S Makaroun, MD
http://content.nejm.org/cgi/content/abstract/317/11/666http://radiology.rsnajnls.org/cgi/content/full/226/2/556http://www.ajronline.org/cgi/content/full/183/5/1361http://www.ajronline.org/cgi/content/full/183/5/1361http://www.emedicine.com/radio/topic2.htmhttp://content.nejm.org/cgi/content/abstract/317/11/666http://radiology.rsnajnls.org/cgi/content/full/226/2/556http://www.ajronline.org/cgi/content/full/183/5/1361http://www.ajronline.org/cgi/content/full/183/5/1361http://www.emedicine.com/radio/topic2.htm

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