Abdomen And Pelvis Radiology

Wala Issa Bani hamad M.D JBR

• https://www.radiologycafe.com/medical-students

What Will be Discussed

G.I Tract

GU Tract.

Anatomy.

Radiological Overview.

Radiograph.

C.T Scan.

Flouroscopy.

Ultrasound,, Liver and Right Kidney

INFERIOR

Abdominal Aorta Non Paired Branches

Aortic branches

Celiac artery

• A.K.A celiac axis or celiac trunk.

• supplying the foregut.

• It arises from the AA and commonly gives rise to three branches:

• Left gastric artery.

• Splenic artery and

• Common hepatic artery.

• AA: abdominal aorta

Celiac trunk

pancreas

Rt adrenal

Lt adrenal T12/L1

Celiac Trunk Seagull sign :

Bifurcation into common hepatic

and splenic arteries

Gall bladder

Superior mesntric artery

L1

• Arises at L1 level • Below SEAGULL SIGN • At the confluence

of portal vein

Diffuse small-bowel ischemia in 60-year-old man with occlusive mesenteric ischemia. Axial CT scan obtained at level of inferior mesenteric artery (arrow) shows large caliber of this vessel. Long segment of small-bowel dilatation has minimal wall thickness of 1-2 mm.

Lt renal artery

Lt renal vein

L1/L2 L3

IMA

IMA: Arises at L3 below SMA Going to left with all its branches.

Inferior Mesenteric Artery

Small Bowel

Second Part of Duodenum

passes between

pancreas and liver

Third part

passes anterior to the Aorta

Jejunum seen at left upper

quadrant

Ileum seen at right lower

quadrant

Radiograph

It is worth knowing that only five basic densities are normally present on X-rays, which appear thus:

Gas - black

Fat - dark grey

Soft tissue/fluid - light grey

Bone/calcification - white

Metal – intense white

N.B: Always check left and right on every film, consciously and routinely –especially just before surgical operations.

Indications (acute)

Emergent evaluation of bowel gas

negative study in some patients may obviate the need for CT

Evaluation of :

radiopaque lines and tubes

radiopaque foreign bodies

postprocedural free gas

bowel gas in postoperative ileus

benefits

• quick and accessible

Limitations

MODEST RADIATION DOSE LOW SENSITIVITY AND SPECIFICITY FOR INTRA-

ABDOMINAL PATHOLOGY

PREGNANCY IS A RELATIVE CONTRAINDICATION

procedure

patient is supine

radiograph is performed AP (anteroposterior)

performed in the radiology department

mobile abdominal radiographs are poor quality

only performed mobile if the patient is very ill

No evidence of pneumoperitoneum.

The bowel gas pattern is normal. No

evidence of bowel wall thickening. Small

right pelvic phlebolith. The

bones are normal. The lung bases are

clear.

No evidence of pneumoperitoneum.

The bowel gas pattern is normal. No

evidence of bowel wall thickening. Small

right pelvic phlebolith. The

bones are normal. The lung bases are

clear.

Purple:Liver Pink: Spleen

Green: Left 11th Rib Orange: Kidneys

Red: Psoas muscle Brown: Spinous process of L1

Light Blue: Pedicles of L3 Black: Transverse processes of L3

Yellow: Vertebral body of L4 Dark Blue: Urinary bladder

Dotted Green: Usual path of the ureter (not usually visible)

Dotted White: Left sacroiliac joint

Pathology

Pathological findings on plain

films

GAS

• Intra-luminal

• Extraluminal

• Intra-peritoneal

• In portal

• In biliary tree

CALCIFICATION

•Phleboliths

•Vascular calcifications

•Calcified LNs

•GBS

•RS / UBS

•Splenic / hepatic granulomas

•Appendicoliths / enteroliths

•Calcified adrenals

AIR

air should only be within bowel loops

free peritoneal air is known as pneumoperitoneum

erect chest x-rays are more sensitive to the presence of pneumoperitoneum than abdominal x-rays

however, there are some key signs on abdominal x-rays of a pneumoperitoneum

Pneumoperitoneum

The Rigler sign, also known as the double wall sign,seen when the air is present on both sides of the intestine, i.e. when there is air on both the luminal and peritoneal side of the bowel wall.

Pneumoperitoneum may be a result of perforation or, recent instrumentation or surgery.

Pneumoperitoneum

look at the wall of the bowel - is it seen as a crisply defined thin white line (Rigler's sign)?

can you see small triangles of air between bowel loops?

can you see the falciform ligament outlined by gas on either side?

does the liver look more lucent than expected?

Gas in the right upper quadrant within the biliary tree is a “normal” finding after sphincterotomy or biliary surgery, but it can indicate the presence of a fistula between the biliary tree and the gut.

Beware of gas in the portal vein, as this can look very similar to biliary air. Gas in the portal vein is always pathological and frequently fatal. It occurs in ischemic states, such as toxic mega colon, and it may be accompanied by gas within the bowel wall (intramural gas).

Portal Venous Gas; Contrast CT image reveals gas in the portal vein, seen as air-density tubular structures extending to the periphery of the liver. Gas in the biliary tree(Pneumobilia) is central and does not extend into the peripheral 2 cm of the liver. In this case, portal venous gas was associated with infarction of the small bowel.

Bowel

stomach, small bowel and large bowel may be differentiated on an abdominal x-ray

pathological features to detect include bowel dilatation, bowel loop displacement and bowel wall thickening

procedure

• the small bowel usually lies centrally, has folds than run all the way across the diameter of the lumen (valvulae conniventis) and usually contains a small volume of air.

• the Large bowel lies peripherally, has folds that run part of the way across the diameter of the lumen (haustral folds) and usually contains some air and fecal matter

Is the bowel dilated?

The 3-6-9- rule refers to the approximate allowable diameter (in centimeters) of the small bowel, large bowel and cecum

3: Small bowel .

6: Colon.

9: Cecum.

Differentiation between bowel on radiograph

Small bowel dilatation

Air fluid level

Distended loops of small bowel and sigmoid colon,

measuring up to 6cm.

Free intraperitoneal gas, with visibility of the inner and outer walls of the bowel

(Rigler's sign).

Large bowel dilatation

Diameter more than 6 cm

Densities

several bony structures are visible on an abdominal x-ray and should be evaluated carefully

calcification may also be visible and may provide a clue as to the cause of the patient's symptoms and signs

Bone And Calcifications

evaluate all of the bones visible on the x-ray as you would on any other x-ray

look at the contours, density, trabecular pattern, areas of lysis or sclerosis

you may see the lower thoracic vertebral bodies, all of the lumbar vertebral bodies, sacrum, iliac blades, ischium, femoral heads and necks, and lowest ribs

examine the renal shadows and paths of the ureters for small densities which indicate stones.

Gall stones are radioopaque in approximately 15-20% of cases

Bone And Calcifications

other calcifications include:

Uterine fibroids calcified

mesenteric lymph nodes

Hepatic/splenic granuloma

Injection sites

calcified lymph nodes are also sometimes identified

small pelvic calcifications are likely to be phleboliths

calcified adrenal glands

% of radio-opaque gallstones? % of radio-opaque urinary stones?

15% %85

pelvic vein phleboliths (calcified thrombi) mostly 5mm or less with central lucent

C.T

• It obtains a series of different angular x-ray projections that are processed by a computer to give a section of specified thickness.

Systematic Approach

• - Mention the section , body area

• - Contrasted versus non contrasted

• - The side for any paired organ

• Click to add text

Absolute positive: BONE +1000 Contrast: 150 Soft tissue: 40-60 Neutral: FLUID 0 Fat: -20-30 Absolute negative: GAS - 1000

Contrasted V.S Non

contrasted

Indications

Abdominal Pain

abdominal sepsis

Bowel obstruction

post-operative complications

trauma

vascular compromise, e.g. Aortic aneurysm.

Benefits

relatively quick and accessible

reproducible findings

complete assessment of the abdomen and pelvis

limitations

Uses Ionizing Radiation

risk of radiation-induced cancer

approximately 100 times the dose of a chest radiograph

requires iodinated I.V Contrast

risk of deterioration in renal function

risk of anaphylactic reaction

procedure

check renal function

lie patient supine on CT table

scout image to plan study

IV contrast injected via pump-injector

60-second delay

scan from dome of diaphragms to symphysis pubis

variations on a theme

• differing the IV contrast injection and timing may be useful

• dual-phase CT abdomen

• two scans (one arterial and one portovenous)

• assessment of vascular supply and parenchyma

• CT pancreas

• 3-phase non-contrast, arterial and portovenous

Pathology

Gastrointestinal Tract

Small Bowel Obstruction

Causes :

Adhesions.

herniae .

and gallstone ileus.

The ‘transition point’ is the point at which proximal bowel is dilated, and distal bowel is collapsed. This usually indicates site of obstruction.

Mechanical vs Functional Obstruction

• Small bowel ileus occurs due to metabolic derangements or post-operatively, with dilatation but no transition point.

Appearance: Dilated small bowel loops proximal to a transition point; Multiple air-fluid levels; Possible ischaemic bowel , at this image inguinal hernia is noted

Large Bowel Obstruction

causes : Cancers.

Diverticulosis Volvulus.

Competent ileocecal valve?

An obstruction of the large bowel causes dilatation of proximal large bowel.

However, the small bowel may or may not be dilated

This depends on ileocaecal valve competency.

.It is competent in ~70% of people.

A competent valve traps contents in the large bowel, so the small bowel is not dilated.

this causes the large bowel to dilate much more and much quicker, putting it at a higher risk of perforation.

The 3-6-9 rule:

Dilated Small bowel: > 3 cm

Dilated Large bowel: > 6 cm

Dilated Caecum: > 9 cm

Appearance: Dilated large bowel

loops proximal to a transition point; M

ultiple air-fluid levels; Dilated

small bowel loops if

valve incompetent

Gallstones

Ultrasound is the gold standard investigation.

CT may miss some stones.

Plain X-ray only shows 10% of stones.

MRCP is useful for ductal stones.

Locations: Gallbladder, Bile ducts, Small bowel (rare).

Appearance

• Ultrasound, single or multiple hyperechoic objects in the gallbladder, with acoustic shadowing.

• On CT, stones may be:

• hyperattenuating (calcified stones),

• isoattenuating (mixed),

• or hypoattenuating (cholesterol stones)

• On MRI, stones are an area of low signal (dark).

Ultrasound Semilunar echogenic intraluminal structure with posterior acoustic

shadowing suggestive of gallstone

C.T coronal images showed hyperdense gallstone

MRI multiple small hypoattenuating round structures suggestive of gallstones

Cholecystitis

Commonly due to gallstone disease.

Biliary colic: Right upper quadrant pain

Cholecystitis: Right upper quadrant pain + Fever

Ascending cholangitis: Right upper quadrant pain + Fever + Jaundice (Charcot’s triad)

Appearance

Distended fluid-filled gallbladder

Thick enhancing (bright) gallbladder wall

Fluid surrounding gallbladder

‘Fat stranding’ surrounding gallbladder (fluid density due to oedema in fat)

C.T Distended

gallbladder with wall thickening

and pericholecystic edema suggestive of cholecystitis

Ultrasound Distended gallbladder

with stone, wall thickening and pericholecystic

edema

Pancreatitis

• Complications include peripancreatic fluid collections (if encapsulated, these are called pseudocysts);

• abscesses;

• necrosis of pancreatic tissue;

• thrombosis of splenic/portal veins;

• and pseudoaneurysms +/- haemorrhage.

Appearance

Enlarged, oedematous pancreas

Fuzzy pancreas borders

Fluid around pancreas

‘Fat stranding’ in retroperitoneum (fluid density due to oedema in fat)

Areas of non-enhancement indicate necrosis

C.T coronal image showed heterogenous partially

non enhancing pancreatic parenchyma

with misty fat planes and surrounding fluid

suggestive of pancreatitis

Edematous, swollen

Renal Stones

99% of stones are visible on CT KUB (done without contrast).

CT shows the exact location of calcifications to see whether or not they are located within the renal tract.

Any associated obstructing effect causing hydroureter or hydronephrosis can be seen.

Inflammation around the ureter may also be seen which could indicate a recently passed stone.

‘Follow’ the ureter from where it leaves the renal pelvis, down along the psoas muscle, anterior to the sacroiliac joint, along the pelvic sidewall, until the ischial spine where it turns medially to reach the bladder.

Appearance

• Very small (2-10mm) hyperdense object within the renal calyces, renal pelvis, or within the course of the ureters. Possible associated hydronephrosis and hydroureter.

The path of the left ureter is

outlined with a yellow arrow. r

enal stone is indicated

with red arrow.

Bilateral nonobstructing

renal stones

Hydronephrosis

• Caused by a distal obstruction:

• stones,

• cancers,

• prostatic hypertrophy,

• pregnancy,

• congenital,

• large blood clot,

• retroperitoneal fibrosis;

• or backflow e.g. vesicoureteral reflux.

• The affected kidney frequently has impaired function. Further radiological tests to assess function include delayed phase contrast CT, intravenous pyelogram, or nuclear medicine tests.

Appearance: Enlarged renal calyces and renal

pelvis. Look for visible cause of

obstruction.

Appendicitis

Appendicitis can present at any age.

In children, mesenteric adenitis is a common and harmless differential that should be considered.

In older people, an underlying caecal carcinoma needs to be considered.

The diagnosis can be made on U/S although the appendix is frequently not visible due to being obscured by overlying bowel gas (65%).

Appearance

Dilated, fluid-filled appendix

‘Fat stranding’ around appendix

Possible associated soft tissue mass (lymphoid tissue, cancer); or hyperdense faecolith at base of appendix

U/S Appendicitis Blind ended non

compressible tube like

structure with wall thickening

and appendicolith

C.T ...Appendicitis the appendix is distended

with misty fat planes and congested mesentry

Diverticulitis

Typically occurs in those over 40

• Terminology

• Diverticulum: Single small outpouching of the bowel

• Diverticula: Plural of diverticulum (i.e. more than one diverticulum)

• Diverticulosis: Multiple diverticula, however no evidence of diverticulitis

• Diverticulitis: Inflammation or infection of a diverticulum

• Diverticular disease: When diverticula are associated with symptoms (e.g. abdominal pain)

Appearance

• Diverticula are multiple small outpouchings, particularly affecting the sigmoid colon. If these are inflamed (diverticulitis), there will be fat stranding, with possible localised perforation or collections.

C.T Divertriculosis multiple small outpouching

of sigmoid colon surface

Diverticulitis C.T

Ischaemic Bowel

Bowel ischaemia may be caused by:

arterial insufficiency (thrombosis or embolism),

venous obstruction,

or as a result of bowel obstruction.

Appearance: Variety of appearances including hypo- or hyper-density of the bowel wall, bowel distension and congestion of the mesentery. Arterial filling defect.

Bowel Ischemia with portal vein

thrombosis , thickened

bowel loops and

surrounding fatty stranding

Infarcted Bowel

Infarcted and gangrenous tissues will start to produce gas.

Therefore, severely infarcted or necrotic bowel may have gas within its walls.

The portal venous system drains the bowel walls. As a result, the portal vein fills with gas that drains into the liver.

Appearance: Air within bowel walls; Air in hepatic portal venous system.

Pneumobilia vs portal venous gas

• The liver shows a widespread branching pattern of portal venous gas, which is a premorbid sign (this is different from pneumobilia, which looks similar but the air is actually within the intrahepatic biliary ducts, seen when there is a fistula between bowel and gallbladder)

C.T coronal images showed necrotic bowel wall in form of pneumatosis

intestinalis with portal venous

gas.

Gas in Peritoneum

Causes of gas/air within intra- or retroperitoneal spaces:

Perforation - of hollow viscus (usually duodenum or sigmoid)

Recent laparoscopic surgery - from CO2 insufflation

Appearance

Free air within the peritoneum. Location of the air depends on the segment of perforated bowel i.e. intra- or retro-peritoneal.

Air can extend into other spaces e.g. pneumomediastinum.

Perforation of the rectum - air in mesorectum (mesentery surrounding rectum).

C.T axial images showed free air in the abdomen

Abdominal Aortic Aneurysm

Focal dilatation of the abdominal aorta.

Two-thirds of patients with ruptured AAAs die before reaching hospital.

Of those who make it to emergency surgery, half die.

Ultrasound used for diagnosis and screening. CT used for suspected leak, but this must not delay emergency surgery.

AAA

Screening for AAA is offered to all men when they turn .

It is a quick ultrasound scan to measure the abdominal aorta, done in the community.

If the test is negative (< 3 cm), there will be no further recall scans, unlike other screening programmes.

If the test is positive (> 3 cm), further action depends on the diameter of the aneurysm:

3.0 - 4.4 cm = repeat in 1 year;

4.5 - 5.4 cm = repeat in 3 months;

> 5.5 cm = immediate referral to vascular surgeons to consider elective repair

Appearance Aneurysm wall usually calcified.

If ruptured, free blood (higher density than fluid e.g. in stomach/GB) with possible contrast leak.

Mural thrombus common, seen as circumferential low density area.

AAA C.T massive dilatation of the abdominal aorta with wall thickening

Caecal volvulus

• describes torsion of the cecum around its mesentry which often results in obstruction . If unrecognised, it can result and fecal peritonitis..

Massive caecal volvulus.

Dilated caecal bowel loop reaching the left

upper quadrant

Plain radiograph...Caecal

Volvulus

• On abdominal radiographs, there is marked distension of a loop of large bowel with its long axis extending from the right lower quadrant to the epigastrium or left upper quadrant.

Markedly dilated loop of colon with a coffee-bean shape. Its apex points toward the right upper quadrant. Lucency at the right edge of the dilated bowel most likely represent compressed ascending colon.

• Grossly-dilated loop of large bowel has a 'coffee-bean shape' and the descending colon tapers in its inferior portion in keeping with a sigmoid volvulus. Air-fluid levels on erect projection.

Whirlpool appearance of midgut volvulus.

• The whirlpool sign of the mesentery, also known as the whirl sign, is seen when the bowel rotates around its mesentery leading to whirls of the mesenteric vessels.

Gynaecology

The preferred modality for initial diagnosis of a suspected gynaecological pathology is ultrasound (transabdominal or transvaginal).

Uterine fibroids can be very large and cause pain if they degenerate. Endometriosis may present as ovarian masses, partially cystic, or as deposits anywhere within the abdominal cavity.

Gynaecologic malignancies are staged with MRI & CT. Ovarian cancer tends to present late, frequently with spread to the peritoneum and omentum by diagnosis.

A ‘Krukenberg tumour’ refers to a metastatic deposit in the ovary which originated from a primary elsewhere within the peritoneal cavity.

Appearance: Uterine fibroids can calcify

and are seen as rounded masses with calcific rims.

Ascites

Ascites is seen in chronic liver disease, heart failure and abdominopelvic malignancies. It presents as abdominal distension.

It can be seen easily on ultrasound and CT. Ultrasound guided paracentesis/drainage can be carried out. A sample of ascitic fluid can be obtained for laboratory testing.

Appearance: Depending on the quantity, it is usually seen as fluid around the liver and spleen, surrounding the bowel, and in the pelvic cavity. It travels to dependent locations, i.e. the left and right paracolic gutters (folds of peritoneum) posteriorly.

U/S .. Ascites moderate amount of anechoic free fluid surrounding liver and bowel

C.T ...Ascites Low density free fluid surrounding the abdominal organs

FlOUROSCOPY

• The bowel filled only with barium, no air introduced.

• the mucosa is coated with barium and the stomach or colon distended by introducing gas, often combination with short acting smooth muscle relaxant.

• Double contrast shows more mucosal detail

Filling defect

- intraluminal filling defect

- intramural filling defect

-extramural compression

Ulceration

-Benign

-malignant

Stricture

-Benign

-malignant

ACHALASIA

• Primary achalasia: Primary motility disorder of the esophagus smooth muscle)

• Secondary or pseudoachalasia: Involvement of gastroesophageal junction by other abnormalities (Chagas disease, tumor)

• Diffuse mediastinal widening with air-fluid level suggests achalasia

•

Radiographic Findings

Mediastinal widening (double contour.)

Marked dilated esophagus

Retro-tracheal air-fluid level

"Bird-beak" deformity of distal esophagus

Little or absent gastric air bubble

Achalasia

Acute tapering at the lower esophageal

sphincter and narrowing at the

gastro-esophageal junction, producing

a "Bird beak" or "rat's tail" appearance.

PA chest radiograph demonstrating a relatively small gas–fluid level in the

mediastinum in a patient with achalasia. Note the soft-tissue density mass

representing the distended oesophagus inferior to the fluid level

Bird-beak" deformity

Is a herniation of the stomach into the mediastinum through the oesophageal hiatus in the diaphragm.

2 general types

- Sliding (axial) hiatal hernia, most common*

• Gastroesophageal (GE) junction and gastric cardia pass through esophageal hiatus of diaphragm into thorax

- Paraesophageal (rolling) hernia rare*

• Gastric fundus ± other parts of stomach herniate into chest while GEJ in normal position.

On conventional xray

Mass with air fluid level at rettrocardiac space

Sliding (axial) hiatal hernia

On barium studies

Sliding hiatal hernia

Paraesophageal hernia

Barium study shows a barium outlined stomach which has herniated into the thoracic cavity along with the gastro-esophageal junction which is evident on AP and oblique views.

Mediastinum enlarged with a para-cardiac

lucency indicative of air. The findings are in

keeping with a hiatus (paraesophageal) hernia.

The stomach and duodenum

Barium meal is the standard contrast medium to examine the stomach and duodenum.

Patient drinks about 200 ml of barium.

Better mucosal detail, the stomach is distended by giving a gas producing agent .

Intravenous injection of a short acting smooth muscle relaxant

Fasting patient for at least 6 hours.

Normal barium meal

Colon Carcinoma

Malignant transformation of colonic mucosa

Imaging

Location: Cecum (10%), ascending colon (15%), transverse colon (15%), descending colon (5%), sigmoid colon (25%), rectosigmoid colon (10%), rectum (20%)

Radiology is critical for screening, diagnosis, treatment, and follow-up of colorectal carcinoma

Detection: Double contrast barium enema

Early cancer: Sessile (plaque-like) lesion or thick, short polyp

Advanced cancer: Large polyp, "saddle" or "apple core" lesion