NORMAL ABDOMINAL

RADIOGRAPH &

PLAIN RADIOGRAPHY IN NON TRAUMATIC

EMERGENCY

• Postgraduate: Dr Inayat Ellahi

Normal abdominal radiograph

• Plain abdominal radiographs are traditionally the initial and most useful method in the evaluation of acute abdomen

• Interpretation of plain films may lead to – A specific diagnosis– Non- specific findings– Misleading conclusions

Technical assessment

• Name, age and sex of patient• Date of radiograph• Projection of film• Penetration• Right/ left orientation• The whole abdomen should be included

Basic densities in an x-ray

Gas Black

Fat Dark grey

Soft tissues/fluid Light grey

Bone/ calcification White

Metal Intense white

Supine ant-post projection

• X-rays pass through the patient from front to back), with the patient positioned supine.

• Single most important film.

Decubitus position

• Use of the decubitus position can demonstrate pneumoperitoneum in a patient who cannot be positioned for an erect chest X-ray to be performed. Gas rises to the upper part of the abdomen and so will be seen on one side of the abdominal X-ray image.

Erect AXR

• its advantage over a supine film is the visualisation of air-fluid levels

Viewing the Xray

• A conventional X-ray should only ever be seriously inspected by uniform transmitted light coming through it, i.e. a viewing box. There is no place for waving it about in the wind when irregular illumination and reflections will prevent 10–20% of the useful information on it being visualized.\

• Even when viewing digital images on a monitor, care should be taken to minimize bright reflections off the screen and keep the background illumination down.

Normal AXR11th 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

• The bones of the spine, pelvis, chest cage (ribs) and the sacroiliac and hip

• joints• ● The dark margins outlining the liver, spleen, kidneys, bladder

and psoas• muscles – this is intra-abdominal fat• ● Gas in the body of the stomach• ● Gas in the descending colon• ● The wide gynaecoid pelvis, indicating that the patient is

female• ● Pelvic phleboliths – normal finding• ● Minor joint space narrowing in the hips (normal for this age)• ● The granular texture of the amorphous fluid faecal matter

containing pockets• of gas in the caecum, overlying the right iliac bone• ● The ‘R’ marked low down on the right side. The marker can

be anywhere on• the film and you often have to search for it. All references to

‘right’ and ‘left’• refer to the patient’s right and left. Note the name badge at

the bottom, not the• top, (blacked out)• ● Check that the ‘R’ marker is compatible with the visible

anatomy, e.g.• – liver on the right• – left kidney higher than the right• – stomach on the left• – spleen on the left• – heart on the left, when visible• ● The dark skin fold going right across the upper abdomen

(normal).• Psoas muscle

• Bowel gas pattern• Any part of the bowel may be visible if it contains gas/air within the lumen.

Gas/air is of low density and forms a natural contrast against surrounding denser soft tissues. It is often difficult to differentiate between normal small and large bowel, but this often becomes easier when the bowel is abnormally distended.

• The upper limit of normal diameter of the bowel is generally accepted as 3cm for the small bowel, 6cm for the colon and 9cm for the caecum (3/6/9 rule).

• Normal bowel sections are sometimes identified by the following features.• Stomach• The stomach may be visible if it contains gas/air. It is not visible if it is either

completely empty, or fluid filled.• Small bowel (duodenum to terminal ileum)• Generally the small bowel lies centrally within the abdomen. The valvulae

conniventes (also called plicae circulares) are thin, circular, folds of mucosa, some of which are circumferential and are seen on an X-ray to pass across the full width of the lumen.

• Large bowel• The retroperitoneal structures of the colon (ascending colon,

descending colon, and rectum) are relatively constant in position. These are often more readily identified than the transverse colon or sigmoid colon which are more variable in position. If visible, the caecum is often the widest segment. It too has a variable position, but is most often confined to the right iliac fossa.

• The longitudinal muscles (taenia coli) and circular muscles of the colon form sacculations called haustra, which have characteristic radiographic appearance.

• Another characteristic feature of large bowel is that it contains faeces. This has a mottled appearance due to its part gaseous content.

Normal fluid levels

• Stomach– Always except in supine

• Small bowel– 2 or 3

• Large bowel– None normally

• Caecal fluid level – 18%

• Abdominal X-rays provide a limited means of assessment of soft tissue structures

• Liver on abdominal X-ray• The liver lies in the right upper

quadrant (RUQ) and is seen as a bland area of grey on an abdominal X-ray.

• The superior edge of the liver forms the right hemi-diaphragm contour (arrowhead).

• In this patient the breast shadow (red line) overlies the liver, and markings of the right lung are visible behind the liver.

• The gallbladder is only rarely visible on an abdominal X-ray. Its position is very variable. This patient has had a cholecystectomy. The clips mark the previous location of the gallbladder.

• Lung bases on abdominal X-ray• The lung bases, which pass

behind the liver and diaphragm in the posterior sulcus of the thorax, may be visible on some abdominal X-rays.

• It is worth checking the lung bases as some patients with lung pathology present with abdominal symptoms.

• If there is consolidation suspected from the abdominal X-ray then a review of the patient's respiratory system is necessary.

• Costophrenic angle (*)

• Psoas edges on abdominal X-ray• The psoas muscles (red) arise from the

transverse processes of the lumbar vertebrae (arrowheads) and combine with the iliacus muscles. Together these powerful muscles form the iliopsoas tendon, which attaches to the lesser trochanter of the femur (*). The iliopsoas muscles are the flexors of the hip.

• An abdominal X-ray often demonstrates the lateral edge of the psoas muscles as a near straight line. The iliacus muscles are not visible, as they lie over the iliac bones of the pelvis.

• Kidneys on abdominal X-ray• Natural contrast between

the kidneys and the low density retroperitoneal fat that surrounds them means they are often visible on an X-ray of the abdomen.

• They lie at the level of T12-L3 and lateral to the psoas muscles. The right kidney is usually slightly lower than the left due to the position of the liver.

• Spleen on abdominal X-ray

• The spleen lies in the left upper quadrant (LUQ)immediately superior to the left kidney.

• Bladder on abdominal X-ray

• The bladder has variable appearance depending on how full it is. It has the same density as other soft tissue structures, due to its water content.

• Normal bones on abdominal X-ray• The lower ribs, lumbar vertebrae and

sacrum are highlighted.• Bones can be used as landmarks for

invisible soft tissue structures. Note the transverse processes of the lumbar vertebrae act as landmarks for the course of the ureters (arrowheads). The vesico-ureteric junctions(*) are located at the level of the ischial spines (arrows).

• Normal bones on abdominal X-ray• The sacrum, coccyx, pelvic bones and

proximal femora are highlighted. The sacro-iliac joint is formed by the overlapping of the sacrum and iliac bones of the pelvis

• There are multiple incidental and asymptomatic calcified structures seen on this X-ray. The patient is recovering from an appendicectomy (note surgical clips).

• Gallstones are seen only if calcified (20% are calcified). Although they may cause symptoms they are usually asymptomatic. If gallstone disease is suspected ultrasound examination is a more appropriate investigation.

• Costochondral calcification, calcified mesenteric lymph nodes, and phleboliths (calcified pelvic veins) are rarely clinically significant. Occasionally additional investigations are required to differentiate them from pathological calcium. For example phleboliths may be mistaken for ureteric calculi. Other investigations such as intravenous urogram (IVU) should only be performed if there are typical clinical features of ureteric calculi.

• Added densities may be due to artifact or calcified soft tissue

• Calcification of soft tissues is not always clinically significant

• Differentiating pathological from inconsequential calcification is not always straightforward

• Do not mistake the tips of the transverse processes for ureteric calculi.

Non-traumatic Abdominal Emergencies

• 1.Ruptured Abdominal Aortic Aneurysm • 2. Ruptured Ectopic Pregnancy • 3. Acute appendicitis • 4. Ruptured Peptic Ulcer • 5. Small Bowel Obstruction • 6. Acute pancreatitis• 7. Diverticulitis • 8. Ovarian torsion • 9. Testicular torsion • 10. Incarcerated or strangulated hernia • 11. Perforated viscus • 12. Mesenteric Ischemia • 13. Cholecystitis • 14. Psoas abscess• 15. Intraabdominal Abscess • 16. Intusseption • 17. urolithiasis

Approach to AXR

• Extraluminal air

• Bowel gas pattern

• Soft tissue masses

• Calcifications

Abnormal extraluminal gas

Extraluminal air• TYPES

– Pneumoperitoneum/free air/intraperitoneal air

– Pneumoretroperitoneum/Retroperintoneal air

– Air in the bowel wall (pneumatosis intestinalis)

Pneumoperitoneum • Conditions causing extraluminal• air• Perforated abdominal viscus• Abscesses (subphrenic and other)• Biliary fistula• Cholangitis• Pneumatosis coli• Necrotising enterocolitis• Portal pyaemia• NOT perforated appendix• Post op 5-7 days even upto 24 days

Signs Of Pneumoperitoneum

• Riglers double wall sign• Football sign• Falciform ligament sign• Triangle sign• Cupola sign

• Rigler's/double wall sign• Rigler's sign (also known as

the double wall sign) is the appearance of lucency (gas) on both sides of the bowel wall. Normally only the inner wall of the bowel is visible

• If there is pneumoperitoneum both sides of the bowel wall may be visible

• The falciform ligament sign (also called the Silver's sign) is a sign seen with pneumoperitoneum.

• It is almost never seen in isolation. If there is enough free air to outline the falciform ligament, there is usually enough air to also provide at least a Rigler's sign.

• The falciform ligament connects the anterior abdominal wall to the liver. The ligament continues to extend inferiorly beyond the liver where it becomes the round ligament (white arrow). Given that the falciform ligament is situated against the anterior abdominal wall, it is not surprising that it becomes outlined with air in a supine patient with free abdominal gas.

• Football sign - example• 2 radiographs were

required to completely cover the abdomen in this large patient

• A large volume of free gas has risen to the front of the peritoneal cavity resulting in a large round black area - 'football sign'

• The cupola sign is seen at supine radiography as an arcuate lucency overlying the lower thoracic spine and projecting caudad to the heart. The superior border is well defined and the inferior margin is poorly delineated. The term cupola is used to indicate the inverted cup shaped configuration of the lucency.

Triangle Sign

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

• Chilaiditi's phenomenon• In patients who have small

livers (cirrhosis), or flattened diaphragms due to lung hyperexpansion (emphysema), 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.

• Subphrenic abscess• This is a localised

collection of free gas and fluid, which usually forms under the right

hemidiaphragm, above the solid liver. This

gas collection usually occurs above the 11th rib

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.

Pneumatosis intestinalis

• Intramural air, may be in the form of cysts (benign) or linear streaks (bowel necrosis)

• Abnormal gas may be found in abdominal organs. Gas in the biliary tree and portal veins is discussed earlier. Gas may also be seen in the kidneys (emphysematous pyelonephritis),pancreas (infected necrosis or abscess), gallbladder wall and urinary bladder

• Emphysematous pyelonephritis. Patient with diabetes mellitus and sepsis. The left renal collecting system and ureter are distended and gas filled. There are also multiple dense gallstones in the gallbladder.

Emphysematous cholecystitis

Emphysematous cystitis

Abnormal intraluminal gas

• If a patient presents with clinical features of obstruction then radiological assessment can be very helpful in determining the level of obstruction, and occasionally the cause.

GASTRIC DILATATION

• Causes• Paralytic ileus (Acute Gastric Dilatation)• Mechanical gastric outlet obstruction• Gastric volvulus• Air swallowing • Intubation

PARALYTIC ILEUS• GENERALISED ileus• Appearances are similar to those of

mechanical obstruction• There are multiple loops of gas

filled bowel projected centrally over the abdomen

• This patient had prolonged non-colicky abdominal pain following a Caesarian section - recovery was spontaneous

• CAUSE• *Postoperative Usually abdominal

surgery• Electrolyte imbalance• Diabetic ketoacidosis

• Localised Ileus• A localized loop of small

bowel is dilated (sentinal loop) in this patient with acute pancreatitis.

• This appearance is not diagnostic of intra-abdominal inflammation, but rather an occasional associated feature.

Causes of Localised Ileusby location

SITE OF DILATED LOOPS CAUSERight upper quadrant CholecystitisLeft upper quadrant PancreatitisRight lower quadrant AppendicitisLeft lower quadrant DiverticulitisMid-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.

Large bowel obstruction

• Dilatation of the caecum >9cm is abnormal• Dilatation of any other part of the colon >6cm

is abnormal• Abdominal X-ray may demonstrate the level of

obstruction• Abdominal X-ray cannot reliably differentiate

mechanical obstruction from pseudo-obstruction

• Large bowel obstruction• Here the colon is dilated

down to the level of the distal descending colon. There is the impression of soft tissue density at the level of obstruction (X). No gas is seen within the sigmoid colon.

• Obstruction is not absolute in this patient as a small volume of gas has reached the rectum (arrow).

• An obstructing colon carcinoma was confirmed on CT and at surgery.

• Pseudo-obstruction• Pseudo-obstruction is a poorly understood functional

abnormality of bowel, most often occurring in the elderly population, in those with underlying systemic medical conditions, or due to certain drugs. The clinical features can be similar to true obstruction, but no mechanical cause is found. An abdominal X-ray cannot reliably differentiate true mechanical obstruction from pseudo-obstruction.

Small bowel obstruction• In small bowel obstruction, dilated small bowel loops are seen

centrally on the radiograph.• The valvulae conniventes should be visible across the whole width

of this dilated bowel.• The dilated bowel diameter is greater than 3 cm but usually less

than 5 cm. There are likely to be several dilated bowel loops. • The number of small bowel loops gives an indication of the level at

which the obstruction within the small bowel has occurred: the higher the obstruction, the fewer the number of loops seen.

• No gas should be seen within the large bowel.• An erect film tends to show multiple small Fluid levels, a

“stepladder” appearance.

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.

Coil spring sign

Comparison of large and small bowel

• Feature Obstruction Small bowel Large bowel• Bowel diameter (cm) >3 and <5 >5• Position of loops Central Peripheral• Number of loops Many Few• Fluid levels Many, short Few, long (on erect film)• Bowel markings Valvaulae Haustra (all the way across) (partially across)• Large bowel gas No Yes

Mechanical SBO Adynamic SBO

Volvulus

• Twisting of the bowel, or volvulus, is a specific cause of bowel obstruction which can have characteristic appearances on an abdominal X-ray.

• The two commonest types of bowel twisting are sigmoid volvulus and caecal volvulus.

• Sigmoid volvulus - coffee bean sign

• Sigmoid volvulus classically results in the formation of a loop of sigmoid colon, which is twisted at the root of the sigmoid mesentery, which lies in the left iliac fossa (LIF). The loop of dilated bowel usually points upwards towards the diaphragm.

• This image demonstrates dilatation of the twisted sigmoid loop 'coffee bean' and of the proximal large bowel (*). This patient is at high risk of perforation and/or bowel ischaemia.

Coffee Bean SignSigmoid volvulus

Massively dilated sigmoid loop

• Caecal volvulus• The caecum is most frequently a

retroperitoneal structure, and therefore not susceptible to twisting. However, in up to 11% of individuals there is congenital incomplete peritoneal covering of the caecum with formation of a 'mobile' caecum on a mesentery, such that it no longer lies in the right iliac fossa. This is a normal variant but is associated with increased incidence of folding or twisting of the caecum (caecal volvulus), which may be complicated by obstruction, vascular compromise, or perforation.

Gastric volvulus

• Spherical viscus• Displaced upwards & to

the left• Raised left

hemidiaphargm• Contains both air and

fluid• Usually no gas in bowel

beyond stomach

Gastric volvulus Caecal volvulus

Gallstone ileus

• 2% of SBO• Specific radiological signs in 40%• High operative mortality• Features– Branching pattern of gas n biliary tree– Gas in portal vein (peripheral)– Obstructing gallstone in ileum• Obscured by sacrum/overlying dilated gut

Biliary tree air Portal venous air

Intussussception• Plain films tray show evidence of

small-bowel obstruction, or the intussusception itself may be identified as a soft-tissue mass someftimes surrounded by a crescent of gas and most frequently i dentified in the right hypochondrium.

• More recently the `target sign' has been described, comprising two concentric circles of fat density lying to the right of the spine-often superimposed on the kidney. It is probably due to the layers of peritoneal fat surrounding and within the intussusceptum alternating with the layers of mucosa and muscle but seen `end on' as it passes forward from the right paraspinal gutter in the transverse colon.

Intraperitoneal fliud• Abdominal X-rays should not be used

to check for ascites. If this diagnosis is suspected then again ultrasound is the best initial investigation, and can also be used to assist drainage.

• Fluid and soft tissues have similar densities, and so ascites may be mistaken for organomegaly. The bowel does not appear pushed to the side as in organomegaly, but rather gas filled bowel rises in a central position, in the supine patient.

• There is generalized hazy densityof entiree abdomen

• Bowel wall inflammation• Occasionally, abdominal X-rays show signs of

inflammation in patients with inflammatory bowel disease. Abnormalities may relate to either acute or chronic stages of disease.

• Mucosal thickening - 'thumbprinting'

• This patient presented with an exacerbation of symptoms of ulcerative colitis .

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

• Lead pipe colon• This patient with ulcerative colitis

has a featureless segment of transverse colon with shows loss of the normal haustral markings.

• This 'lead pipe' appearance is associated with longstanding ulcerative colitis.

• The distal bowel is always involved in this disease but, as there is no air in the descending colon, this segment of colon is not evidently abnormal.

• Toxic megacolon is a potentially life-threatening condition characterized by dilatation of the large bowel without obstruction, in the context of acute bowel inflammation. This may be due to inflammatory bowel disease, especially ulcerative colitis, or other causes of colitis such as infection.

• Meteorism (excessive swallowed air) is particularly common in crying children and hyperventilating adults. Although there are prominent bowel loops, there is no cut off point: the bowel has beenlikened to crazy paving.

Abnormal calcification

• Renal stones/calculi are concretions of inorganic material within the renal collecting system. 90% of renal calculi contain enough calcium to be visible on abdominal X-rays. Urate and matrix stones are not visible.

• 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.

• 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. Nephrocalcinosis

• The renal parenchyma contains clusters of small calcific densities

• Ureteric stones (calculi) are often seen on an abdominal X-ray performed as a 'control' study for an IVU. This control image is known as a Kidneys-Ureters-Bladder image (KUB).

• As with renal stones approximately 90% are visible.

• Ureteric stones originate as renal stones. If a renal stone migrates into a ureter it may cause renal outflow tract obstruction, which manifests clinically with severe ipsilateral flank/loin/groin pain, usually with haematuria.

• Bladder stones generally form in the bladder itself. They arise as a result of urinary stasis such as in bladder outflow obstruction (enlarged prostate) or in patients with a neurogenic bladder (loss of bladder function due to spinal cord injury/disease). Those with bladder wall abnormalities (ureterocele, diverticulum) or those with recurrent urinary infections are also at higher risk of forming bladder stones.

• When seen on an abdominal/pelvic X-ray they are often multiple and rounded.

• Calcification of arteries seen on x-rays is a sign of more generalised atherosclerosis.

• Occasionally vascular calcification seen on an abdominal X-ray reveals an unexpected aneurysm. Remember that abdominal pain is not only caused by gastrointestinal disease.

Chinese Dragon Sign

Calcified splenic artery

• Abdominal aortic aneurysm - AAA

• There is calcification of the dilated aortic wall

• As in this case often only one side of the aneurysm is visible - the other projected over the spine

• Leaking aortic aneurysm

• Large soft tissue density shadow extends beyond the calcific rim of aneurysm suggestive of retroperitoneal hematoma.

• Retroperitoneal calcification• Occasionally you may see

calcification of retroperitoneal organs such as the pancreas or adrenals, which only become visible when calcified.

• Pancreatic calcification is a feature of chronic pancreatitis.

• Adrenal (suprarenal) calcification is an uncommon finding and is usually incidental. Most often it is considered a result of previous haemorrhage or tuberculosis.

• Gallstones and mesenteric lymph node

• Gallstones have a variable position depending on the position of the gallbladder and may be mistaken for renal stones

• Unlike renal stones they are often rounded and cluster together

• This X-ray also shows an incidental calcified mesenteric node which may also mimic renal stones

Radiological signs in acute appendicitis

• Appendicolith • Sentinal loop• Dilated caecum• Right lower quadrent haze• RIF mass indenting caecum• Blurring of right psoas outline• Intestinal obstruction

• Appendicolith• In appendicitis the abdominal X-ray is

usually normal, and is not a required investigation unless a complication such as perforation is suspected. Occasionally an appendicolith is seen. This is a small calcified stone within the appendix, and is seen in the right iliac fossa.

• Although an uncommon feature of appendicitis an appendicolith is highly predictive of the diagnosis in patients presenting with abdominal pain, and is also thought to be associated with a higher risk of gangrene or perforation.

• Gynaecological calcification

• The final structure in this section is found only in women—fibroids. These can become calcified and appear as rounded structures of varying size and location in the pelvis.

• Foreign body - ingested• This psychiatric patient

has ingested numerous radio-opaque objects

Abnormal soft tissues

• Hepatomegaly• There is diffuse soft tissue

density shadowing in the right upper quadrant due to hepatomegaly (liver enlargement)

• The enlarged liver has displaced the normal bowel downwards and to the left

• The spleen is also mildly enlarged

• Massive splenomegaly• This patient with a

myeloproliferative disorder has both hepatomegaly and massive splenomegaly

• There is generalised increase in soft tissue density but the bowel appears pushed away by the edge of the spleen

• Enlarged kidneys• Both kidneys are very

enlarged• The bowel is not displaced

because the kidneys are retroperitoneal structures

• This patient had a family history of polycystic kidneys

• This diagnosis was confirmed with ultrasound

• Abdominal X-rays should not be used to check for ascites. If this diagnosis is suspected then again ultrasound is the best initial investigation, and can also be used to assist drainage.

• Fluid and soft tissues have similar densities, and so ascites may be mistaken for organomegaly. The bowel does not appear pushed to the side as in organomegaly, but rather gas filled bowel rises in a central position, in the supine patient.

• There is generalised hazy density of the entire abdomen

• Pelvic mass - large• A very large soft tissue

density mass extends upwards from the pelvis

• Bowel is displaces superiorly in the abdomen

• Bone metastases• There are numerous

sclerotic densities (white) of the vertebrae, sacrum, pelvis and proximal femora

• This patient had a known history of breast cancer

• Abdominal pain was actually due to high serum calcium

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