Abdomen X ray signs

Abdominal X-ray Radiological Signs

Suzanne O’Hagan

Lightbulb moment

a moment of sudden inspiration, revelation, or recognition

Approach to AXR

Bowel gas pattern Extraluminal air Soft tissue masses Calcifications

Normal AXR

11th rib
Hepatic flexure
Gas in stomach
T12
Gas in caecum
Iliac crest
Femoral head
SI joint
Gas in sigmoid
Transverse colon
Splenic flexure
Psoas margin
Sacrum
Left kidney
Liver
Bladder

Gas pattern

Stomach Almost always air in stomach Small bowel Usually small amount of air in 2 or 3 loops Large bowel Almost always air in rectum and sigmoid Varying amount of gas in rest of large bowel
What is normal?

Normal fluid levels

Stomach Always (upright, decub) Small bowel Two or three levels acceptable (upright, decub) Large bowel None normally (functions to remove fluid)

Large vs small bowel

Large bowelPeripheral (except RUQ occupied by liver)Haustral markings don’t extend from wall to wallSmall bowelCentralValvulae conniventes extend across lumen and are spaced closer together

Radiographic principles

Series of films for acute abdomen Obstruction series/ Acute abdominal series/ Complete abdominal series Supine (almost always) Upright or left decubitus (almost always) Prone or lateral rectum (variable) Chest, upright or supine (variable)

VIEW

LOOK FOR
SUPINE ABDOMEN
Bowel gas pattern Calcifications Masses
PRONE ABDOMEN
Gas in rectosigmoid Gas in ascending and descending colon
UPRIGHT ABDOMEN
Free air, air-fluid levels
UPRIGHT CHEST
Free air, lung pathology secondary to intraabdominal process
Acute abdominal seriesWhat to look for
Substitutes: Prone Lateral rectum Upright Left lateral decub Upright chest Supine chest
྽Ş


Obtaining views
Supine Patient on back, x ray beam directed vertically downward, casette posterior, x-ray tube anterior (AP) Prone Patient on abdomen, x-ray beam directed vertically downward, cassette anterior, x-ray tube posterior (PA) Upright Patient stands or sits, x-ray beam directed horizontally, cassette posterior, x-ray tube anterior (AP) Upright chest Patient stands or sits, horizontal x-ray beam, cassette anterior, x-ray tube posterior (PA)
1900s X-Ray-based fluoroscopy machine in which radiation is shot directly through the patient and into the doctor’s face.

Abnormal Gas Patterns

Functional ileusOne or more bowel loops become aperistaltic usually due to local irritation or inflammationLocalised “sentinel loops” (one or two loops)Generalised (all loops of large and small bowel)Mechanical obstructionIntraluminal or extraluminalSmall bowel obstructionLarge bowel obstruction

3, 6, 9 RULE

Maximum Normal Diameter of bowel Small bowel 3cm Large bowel 6cm Caecum 9cm

Localised ileusKey features

One or two persistently dilated loops of small or large bowel (multiple views) Often air-fluid levels in sentinel loops Local irritation, ileus in same anatomical region as pathology Gas in rectum or sigmoid May resemble early SBO

Causes of Localised Ileusby location

SITE OF DILATED LOOPS
CAUSE
Right upper quadrant
Cholecystitis
Left upper quadrant
Pancreatitis
Right lower quadrant
Appendicitis
Left lower quadrant
Diverticulitis
Mid-abdomen
Ulcer or kidney/ureteric calculi

Colon cut off sign

Explanation: Inflammatory exudate in acute pancreatitis extends into the phrenicocolic ligament via lateral attachment of the transverse mesocolon Infiltration of the phrenicocolic ligament results in functional spasm and/or mechanical narrowing of the splenic flexure at the level where the colon returns to the retroperitoneum.
Abrupt cutoff of colonic gas column at the splenic flexure (arrow). The colon is usually decompressed beyond this point.

Generalised ileusKey features

Entire bowel aperistaltic/hypoperistaltic Dilated small bowel and large bowel to rectum (with LBO no gas in rectum/sigmoid) Long air-fluid levels
CAUSE
REMARK
*Postoperative
Usually abdominal surgery
Electrolyte imbalance
Diabetic ketoacidosis
* almost always

Generalised adynamic ileus

The large and small bowel are extensively airfilled but not dilated. The large and small bowel "look the same".

Mechanical SBO

Dilated small bowel Fighting loops (visible loops, lying transversely, with air-fluid levels at different levels) Little gas in colon, especially rectum

SBO Erect

SBO Supine
Air fluid levels

Causes of Mechanical SBO

* May be visible on AXR
Adhesions
Hernia*
Malignancy
Gallstone ileus*
Intussesception
Inflammatory bowel disease

Step ladder appearance

Loops arrange themselves from left upper to right lower quadrant in distal SBO



Coil spring sign

String of pearls sign

Considered diagnostic of obstruction (as opposed to ileus) and is caused by small bubbles of air trapped in the valvulae of the small bowel.

Stretch/slit sign

Slit of air caught in a valvulae, characteristic of SBO

Closed loop obstruction

Two points of same loop of bowel obstructed at a single location Forms a C or a U shape Term applies to small bowel, usually caused by adhesions Large bowel, called a volvulus

Crescent Sign

Caused by: LUQ Soft tissue mass OR Head of intussusception in distal transverse colon

Double Bubble Sign

Duodenal Atresia



Mechanical LBO
Colon dilates from point of obstruction backwards Little/no air fluid levels (colon reabsorbs water) Little or no air in rectum/sigmoid

Large bowel obstruction

Bowel loops tend not to overlap therefore possible to identify site of obstruction Little or no gas in small bowel if ileocaecal valve remains competent* * If incompetent, large bowel decompresses into small bowel, may look like SBO

Causes of Mechanical LBO

TUMOUR
VOLVULUS
HERNIA
DIVERTICULITIS
INTUSSUSCEPTION

Note on volvulus

Sigmoid colon has its own mesentry therefore prone to twisting Caecum usually retroperitoneal and not prone to twisting; 20% people have defect in peritoneum that covers the caecum resulting in a mobile caecum

Volvulus

A volvulus always extends away from the area of twist.
Sigmoid volvulus can only move upwards and usually goes to the right upper quadrant. Caecal volvulus can go almost anywhere.


Coffee Bean SignSigmoid volvulus
Massively dilated sigmoid loop

Hernia

Lateral decubitus of value The advantage is that there may be a greater chance of air entering the herniated bowel because it is the least dependent part of the bowel in the supine position.

Apple core sign

Radiologic manifestation of a focal stricture of the bowel usually at contrast material enema examination. The stricture demonstrates shouldered margins and resembles the core of an apple that has been partially eaten. The most common cause is an annular carcinoma of the colon.

Thumbprinting

The distance between loops of bowel is increased due to thickening of the bowel wall. The haustral folds are very thick, leading to a sign known as 'thumbprinting.'

Lead pipe colon

Shortening of colon secondary to fibrosis Loss of haustration Ulcerative colitis

Extraluminal air

TYPES Pneumoperitoneum/free air/intraperitoneal air Retroperintoneal air Air in the bowel wall (pneumatosis intestinalis) Air in the biliary system (pneumobilia)

Upright film best

The patient should be positioned sitting upright for 10-20 minutes prior to acquiring the erect chest X-ray image. This allows any free intra-abdominal gas to rise up, forming a crescent beneath the diaphragm. It is said that as little as 1ml of gas can be detected in this way.

Free AirCauses

Rupture of a hollow viscus Perforated peptic ulcer Trauma Perforated diverticulitis (usually seals off) Perforated carcinoma Post-op 5-7 days normal, should get less with successive studies *NOT ruptured appendix (seals off)

Signs of free air

Crescent signChilaiditis signRiglers (and False Rigler’s)Football signFalciform ligament signTriangle signCupola signLesser sac sign

Crescent Sign II

Free air under the diaphragm
Best demonstrated on upright chest x rays or left lat decub Easier to see under right diaphragm

Chilaiditis sign

May mimic air under the diaphragm Look for haustral folds Get left lat decub to confirm
In patients who have cirrhosis or flattened diaphragms due to lung hyperinflation, a void is created within the upper abdomen above the liver. This space may be filled by bowel. If this bowel is air filled then it may mimic free gas.


Rigler’s Sign Bowel wall visualised on both sides due to intra and extraluminal air Usually large amounts of free air May be confused with overlapping loops of bowel, confirm with upright view



False Rigler’s Sign The Rigler sign can sometimes be simulated by contiguous loops of bowel, whereby intraluminal air in one loop of bowel may appear to outline the wall of an adjacent loop, which results in a misdiagnosis of free air. Measure distance of interface if unsure

Football SIgn

Seen with massive pneumoperitoneum Most often in children with necrotising enterocolitis
Paediatric
Adult
In supine position air collects anterior to abdominal viscera

Falciform ligament sign

Normally invisible. Supine film, free air rises over anterior surface of liver

Other patterns of air around liver

Doge’s Cap Sign

Inverted V sign

On the supine radiograph, an inverted "V" may be seen over the pelvis in a patient with pneumoperitoneum. While in infants this is produced by the umbilical arteries, in adults it appears to be created by the inferior epigastric vessels



Continuous diaphragm sign
Sufficient free air, left and right hemi- diaphragms appear continous

Lesser sac Sign Cupola Sign

Lesser sac sign (black arrows)
The lesser sac is positioned posterior to the stomach and is usually a potential space. There is free connection between the lesser sac and the greater sac through the foramen of Winslow
Cupola sign (white arrows)
Air superior to left lobe of liver
Double Bubble Sign

Cupola Sign

The term cupola comes from a dome such as this famous dome of the Duomo in Florence.
Air beneath the central tendon of the diaphragm

Triangle Sign

The triangle sign refers to small triangles of free gas that can typically be positioned between the large bowel and the flank

Retroperitoneal Air

Recognised by: Streaky, linear appearance outlining retroperitoneal structures Mottled, blotchy appearance Relatively fixed position May outline: Psoas muscles Kidneys, ureters, bladder Aorta or IVC Subphrenic spaces

Causes of retroperitoneal air

Bowel perforation (appendix, ileum, colon) Trauma (blunt or penetrating) Iatrogenic Foreign body Gas producing infection

Pneumoretroperitoneum

This patient has free air in the retroperitoneal space. The air is seen surrounding the lateral border of the right kidney (white arrow). There is other evidence of free gas including Rigler's sign. If you are not confident that the appearance is pneumoretroperitoneum, you can try an erect and decubitus view to see if the gas moves. If the gas is seen to move, it's not in the retroperitoneum.

Air in the bowel wall

Signs Best seen in profile producing a linear lucency that parallels the bowel Air en face has a mottled appearance resembling gas mixed with faeculent material

Causes of air in bowel wall

Primary Pneumatosis cystoides intestinalis (rare) usually affects left colon Produces cyst-like collections of air in the submucosa or serosa Secondary Diseases with bowel wall necrosis Obstructing lesions of the bowel that raise intraluminal pressure Complications Rupture into peritoneal cavity Dissection of air into portal venous system

Pneumatosis intestinalis

Intramural air, best appreciated in profile

Air in the biliary tree

One or two tube-like branching lucencies in the RUQ, conform to location of major bile ducts

Causes

“Normal” if Sphincter of Oddi incompetencePrevious surgery including sphincterotomy or transplantation of CBDPathology (uncommon)Gallstone ileus: gallstone erodes through wall of GB into the duodenum producing a fistula between the bowel and the biliary system. Stone impacts in small bowel = mechanical SBO. “ileus” misnomer

Biliary vs Portal Venous Air

Portal venous air usually associated with bowel necrosis Air is peripheral rather than central Numerous branching structures

Soft tissue masses

Organomegaly Know normal landmarks 2 ways to identify soft tissue masses/organs: Direct visualisation of edges of structure Indirect by displacement of bowel
CT, US and MRI have essentially replaced conventional radiography in the assessment of organomegaly and soft tissue masses

Location Pattern

Abdominal Calcifications

First exclude artefact

Kim Kardashian’s butt – real or artefact?

Location

Vascular Liver Gallbladder Spleen Pancreas Lymph nodes Adrenals Kidneys Ureters Bladder Prostate

Rim-like

Calcification that has occurred in the wall of a hollow viscus Cysts renal, splenic, hepatic Aneurysms aortic, splenic, renal artery Saccular organs Gallbladder Urinary bladder
Calcified hydatid cysts

Linear/Track

Calcification in walls of tubular structures Arteries Fallopian tubes Vas deferens Ureter
Aortoiliac calcification

Chinese Dragon Sign

Calcified splenic artery

Calcified vas deferens

Floccular, Amorphous, Popcorn
Formed in solid organ or tumour Pancreas (chronic pancreatitis) Leiomyomas of uterus Ovarian cystadenomas Lymph nodes Adenocarcinomas of stomach, ovary, colon Metastases Soft tissue (previous trauma, crystal deposition)

Calcified enteric lymph nodes

Calcified fibroids
Calcified pancreas
Floccular

Lamellar or laminar

Formed around a nidus inside hollow lumen Concentric layers due to prolonged movement of stone inside hollow viscus Renal stones Gallstones Bladder stones

Bladder calculi

Lamellar

Renal calculi

Pelvicalyceal calcifications

Staghorn Calcification

Renal stones are often small, but if large can fill the renal pelvis or a calyx, taking on its shape which is likened to a staghorn.
Tubular



Nephrocalcinosis Uncommonly the renal parenchyma can become calcified. This is known as nephrocalcinosis, a condition found in disease entities such as medullary sponge kidney or hyperparathyroidism.
Renal calculi
Parenchymal calcification
Flocculent

Putty Kidney

"Putty kidney" – sacs of casseous, necrotic material (TB)Autonephrectomy – small, shrunken kidney with dystrophic calcification Flocculent

Calcified gallstones

Lamellar

Conclusion

Approach to AXR should include gas pattern, extraluminal air, soft tissue and calcifications Named radiological signs are a useful way of remembering, identifying and reporting on films

References

Herring, W. Learning Radiology 2nd Ed, 2012 Begg, J. Abdominal X-rays Made Easy, 1999 http://www.wikiradiography.com http://www.radiopaedia.org http://www.imagingconsult.com Roche, C et al. Radiographics: Selections from the buffet of food signs in Radiology. Nov 2002, RG, 22, 1369-1384 Young, L. Radiology Cases in Paediatric Emergency Medicine. Vol 1 Ca 2. The Target, Crescent and Absent Liver Edge Signs. Raymond, B et al. Radiographics: Classic signs in uroradiology. RSN 2004 http://www.swansea-radiology.co.uk Radiology Teaching Site. Introduction to abdominal radiography Mussin, R. Postgrad Med J 2011: 87:274-287. Gas patterns on plain abdominal radiographs http://www.radiologymasterclass.co.uk/tutorials/abdo/abdo_x-ray_abnormalities Mettler: Essentials of Radiology, 2nd Ed, 2005 http://www.learningradiology.com/radsigns Muharram Food signs in radiology. International Journal of Health Sciences Vol 1 No 1. Jan 2007.


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