This document provides an overview of plain abdominal x-rays and gastrointestinal imaging. It discusses how to analyze intestinal gas patterns, identify dilated bowel sections, and look for signs of pneumoperitoneum or ascites. It describes different types of bowel obstructions and how to distinguish small vs. large bowel obstruction based on dilation patterns. The document also discusses imaging of the esophagus, including how barium swallow exams are performed and what they can reveal about strictures, contractions, and dilation.

1. Plain Abdomen &
Gastrointestinal Tract
(OESOPHAGUS)
By: Khashayar
Cyrus

2.  The standard plain film of the abdomen is a supine
anteroposterior
 Free intraperitoneal air can be seen on an erect chest
radiograph (CXR), which is usually performed at the time of the
abdominal x-ray. Rarely, in patients who are unable to sit or
stand, a lateral decubitus view (i.e. an AP film with the patient
lying on his or her side) is performed using a horizontal x-ray
beam as a means of detecting free intraperitoneal air
 looking at a plain abdominal film:
• Analyze the intestinal gas pattern and identify any dilated
portion of the gastrointestinal tract.
• Look for gas outside the lumen of the bowel.
• Look for ascites and soft tissue masses in the abdomen and
pelvis.
• If there are any calcifications, try to locate exactly where they
lie.
• Assess the size of the liver and spleen.

3. Intestinal gas pattern:
 Relatively large amounts of gas are usually present in the
stomach and colon in a normal patient. The stomach can be
readily identified by its location above the transverse colon, by
the band-like shadows of the gastric rugae in the supine view.
The duodenum often contains air and there may be some gas
in the normal small bowel, but it is rarely sufficient to outline the
whole of a loop. If the bowel is dilated it is important to try and
decide which portion is involved.
 Dilatation of the bowel:
 Dilatation of the bowel is the cardinal plain film sign of intestinal
obstruction, and the pattern of dilatation is the key to the
radiological distinction between small and large bowel
obstruction. In small bowel obstruction, the small intestine is
dilated down to the point of obstruction and the bowel beyond
this point is either empty or of reduced calibre.

4.  In large bowel obstruction, the large bowel is dilated down to the
level of obstruction. If the ileocaecal valve, where the ileum joins
the colon, is incompetent, there will also be small bowel
dilatation. Making the distinction between large and small bowel
obstruction depends on the ability to recognize which portions of
bowel are dilated.Dilated small bowel usually lies in the centre
of the abdomen within the ‘frame’ of the large bowel (but the
sigmoid and transverse colon may be redundant and may also
lie in the centre of the abdomen, particularly when dilated).
When the proximal and mid small intestine are dilated, the
valvulae conniventes (plica circulares) can be identified. The
valvulae conniventes are always closer together and cross the
width of the bowel (the colonic haustra do not), often giving rise
to an appearance known as a ‘stack of coins’The distal small
intestine has a relatively smooth outline and it may be difficult to
distinguish the lower ileum and the sigmoid colon because both
may be smooth in outline. The radius of curvature of the loops is
sometimes helpful: the tighter the curve, the more likely the loop
is to be dilated small bowel.The colon is recognized by its
haustra, which usuallyform incomplete bands across the colonic
gas shadows.Haustra are always present in the ascending and
transverse colon, but may be absent distal to the splenic flexure.

5. A. B.

6.  If the cause or site of the obstruction is not evident from plain
films, and immediate exploratory surgery is not indicated,then
computed tomography (CT) or a contrast study(either a follow-
through for small bowel obstruction or instant enema for large
bowel obstruction) is helpful. CT can demonstrate the site of
obstruction by showing the location of the transition from dilated
to collapsed bowel, and can confirm or exclude a mass at the
site of obstruction
 Dilatation of the bowel occurs in a number of conditions. In
remembering causes of mechanical bowel obstruction it is often
easiest to think of conditions that: (i) obstruct the lumen (e.g.
gall stone ileus); (ii) affect the bowelwall and cause a narrowing
(e.g. Crohn’s disesase; or (iii)cause extrinsic compression of the
bowel (e.g. adhesions).Bowel dilatation, however, occurs in
conditions other than mechanical bowel obstruction, notably:
paralytic ileus,acute ischaemia and inflammatory bowel disease.
The radiologicaldiagnosis of these phenomena depends mainly
onthe pattern of distribution of the dilated loops

7. paralytic ileus Mechanical obstruction
of
the small bowel

8. Mechanical obstruction of Closed loop
obstruction
the large bowel

9. Toxic dilatation of the colon

10. Pneumoperitoneum
 The radiological diagnosis of perforation of the
gastrointestinal
 tract is based on recognizing free gas in the peritoneal cavity
(pneumoperitoneum) The most common cause of
spontaneous pneumoperitoneum is a perforated peptic ulcer
and two-thirds of such cases are recognizable radiologically.
The largest quantities of free gas are seen after colonic
perforation, and the smallest amounts with leakage from the
small bowel. A pneumoperitoneum is very rare in acute
appendicitis even if the appendix has perforated.Free
intraperitoneal air is a normal finding after laparotomy or
laparoscopy. In adults, all the air is usually absorbed within 7
days. In children, the air absorbs much faster, usually within
24 hours. An increase in the amount of airon successive films
indicates continuing leakage of air.

11.  Pneumoperitoneum under the right hemidiaphragm is usually
easy to recognize on an erect CXR as a curvilinearcollection
of gas between the line of the diaphragm and the opacity of
the liver. Free gas under the left hemidiaphragm is more
difficult to identify because of the overlapping gas shadows of
the stomach and the splenic flexure of the colon. Gas in these
organs may mimic free intraperitonealair when none is
present.

12. Gas in an abscess
 Gas in an abdominal or pelvic abscess produces a very variable pattern
on plain films. It may form either small bubbles or larger collections of
air, both of which could be confused with gas within the bowel. Fluid
levels in abscesses may be seen on a horizontal x-ray film. As
abscesses are mass lesions, they displace the adjacent structures; for
example, the diaphragm is elevated with a subphrenic abscess, and the
bowel is displaced by pericolic and pancreatic abscesses. A pleural
effusion or pulmonary collapse/ consolidation are very common in
association with subphrenic abscess. Ultrasound and CT are
extensively used to evaluate abdominal abscesses

13. Gas in the wall of the bowel
 Numerous spherical or oval bubbles of gas are seen in the wall
of the large bowel in adults in the benign condition known as
pneumatosis coli. Linear streaks of intramural gas have a more
sinister significance as they usually indicate infarction of the
bowel wall. Gas in the wall of the bowel in the neonatal period,
whatever its shape, is diagnostic of necrotizing enterocolitis a
disease that
is fairly common in premature
babies with respiratory problems.

14. Gas in the biliary system
 Gas in the biliary system is seen on plain films following
sphincterotomy or anastomosis of the common bile duct to the
bowel (Fig. 5.10). It is also seen with a fistula from erosion of a
gall stone into the duodenum or colon, or following penetration of
a duoden al ulcer into the common bile duct.
Gas may be seen, very
occasionally, in the wall or
lumen
of the gall bladder in acute
cholecystitis from gas-forming
organisms

15. Ascites
 Small amounts of ascites cannot be detected on plain films. Larger
quantities separate the loops of bowel from one another and
displace the ascending and descending colon from the fat stripes,
which indicate the position of the peritoneum along the lateral
abdominal walls The loops of small bowel float to the centre of the
abdomen In practice, plain films are of very limited value in the
diagnosis of ascites as the signs are so difficult to interpret
confidently except when a large amounts of ascites is present.
Ascites is readily recognized at ultrasound or CT

16. Abdominal calcification
 An attempt should always be made to determine the nature of
any abdominal calcification. The first essential is to localize the
calcification, as once the organ of origin is known the pattern or
shape of the calcification will usually limit the diagnosis to just
one or two choices The most common calcifications are of little
or no significance to the patient; most are phleboliths, calcified
lymph nodes, costal cartilages and arterial calcification.
Calcifications in the abdomen are likely to be one of the
following:
 Pelvic vein phleboliths:

17. Calcified mesenteric lymph nodes:
Vascular calcification:

18. Uterine fibroids
Malignant ovarian masses:

19. Adrenal calcification
Liver calcification
Splenic calcification

20. Pancreatic calcification
Faecoliths

21. Liver and spleen
 Substantial enlargement of the liver has to occur before it can be
recognized on a plain abdominal film. As the liver enlarges it
extends well below the costal margin, displacing the hepatic
flexure, transverse colon and right kidney downwards and
displacing the stomach to the left. The diaphragm may also be
elevated Occasionally, there is a tongue-like extension of the
right lobe into the right iliac fossa. This is a normal variant known
as a Reidl’s lobe and should not be confused with generalized
liver enlargement.As the spleen enlarges, the tip becomes visible
in the left

22. Abdominal and pelvic masses
 Attempting to diagnose the nature of an abdominal mass on a
plain film is notoriously difficult, and ultrasound, CT or magnetic
resonance imaging (MRI) are the appropriate imaging modalities.
The site of the mass, the displacemen of adjacent structures and
the hpresence of calcification are important diagnostic signs but
plain films are unable to distinguish between solid and cystic
masses.An enlarged bladder can be seen as a mass arising from
the pelvis, displacing loops of bowel. In females, uterine and
ovarian enlargements also appear as masses arising from the
pelvis. Ovarian cysts can become very large, almost filling the
abdomen and displacing the bowel to the sides of the abdomen
(Fig. 5.19). An ovarian dermoid cyst can be readily identified on a
plain film due to its content of low attenuation fat and often the
presence of other mesenchymal structures within it, such as
teeth.Retroperitoneal tumours and lymph nodes, when
large,become visible on plain films. Renal masses, especially cysts
and hydronephrosis, can become large and appear as masses in
the flank. With retroperitoneal masses the outline of the psoas
muscle may become invisible.

23. Gastrointestinal Tract
 Imaging techniques: general principles
 Contrast examinations
 Computed tomography
 Ultrasound examinations
 Magnetic resonance imaging
 Nuclear medicine

24. OESOPHAGUS
Plain films:
 Plain films do not normally show the oesophagus unless it is very dilated (e.g.
achalasia), but they are of use in demonstrating an opaque foreign body such as
a bone lodged in the oesophagus Plain films are also used to check the position
of a nasogastric tube, to ensure that thetube travels down through the
oesophagus and into the stomach, rather than down into one of the main bronchi
or an oesophageal pouch

25. Barium swallow examination
 The patient swallows a gas-producing agent to distend
theoesophagus, followed by barium, and its passage down the
oesophagus is observed on a television monitor. Films are taken
with the oesophagus both full of barium to show the outline, and
following the passage of the barium to show the mucosal
pattern.The oesophagus has a smooth outline when full of barium.
When empty and contracted, barium normally lies in between the
folds of mucosa, which appear as three or four long, straight,
parallel lines Peristaltic waves can be observed during
fluoroscopy.They move smoothly along the oesophagus to propel
the barium rapidly into the stomach. It is important not to confuse a
contraction wave with a true narrowing: a narrowing is constant
whereas a contraction wave is transitory.Sometimes the contraction
waves do not occur in an orderly fashion but are pronounced and
prolonged, giving the oesophagus an undulated appearance (Fig.
6.6). These socalled tertiary contractions usually occur in the
elderly, and in most instances they do not give rise to
symptoms.Occasionally, tertiary contractions cause
dysphagia.Endoscopy is the primary investigation in patients with
dysphagia.

26. Normal oesophagus barium has passed Tertiary
contractions

27. Computed tomograpphy
 Computed tomography is used in the staging of carcinoma of the
oesophagus. The primary function of CT is to detect distant
disease (e.g. lung, liver or bone metastases), and although it
does give information on local staging, this is more accurately
performed by endoscopic ultrasound

28. Fluorodeoxyglucose positron
emission tomography/
computed tomography
 In patients with oesophageal carcinoma who have potentially
curable disease, an FDG-PET/CT study is performed to identify
any occult metastases prior to undertaking either surgery or
definitive chemoradiotherapy.

29. Oesophageal abnormalities
 Strictures of the oesophagus
 Dilatation of the oesophagus
 Strictures of the oesophagus:
Oesophageal carcinoma

30. Peptic strictures

31. Achalasia

32. Corrosive strictures

33. Benign tumours
Other medistinal masses
Anomalous right subclavian artery

34. Dilatation of the oesophagus
 There are two main types of oesophageal dilatation –obstructive
and non-obstructive:
 Dilatation due to obstruction is associated with a visible
stricture. The patient with a carcinoma usually presents with
dysphagia before the oesophagus becomes very dilated.On the
other hand, a markedly dilated oesophagus indicates a very
longstanding condition, usually achalasiaor occasionally a
benign stricture.
 Dilatation without obstruction occurs in scleroderma.The
disease involves the oesophageal muscle, resulting in dilatation
of the oesophagus, which resembles an inert tube with no
peristaltic movement so that barium does not flow from the
oesophagus into the stomach unless the patient stands upright.

35. Other abnormalities of the oesophagus
 oesophageal web

36. Oesophageal diverticula

37. oesophageal atresia