3. GI (Large Bowel, Peritoneal Cavity)

Question 1

Crohn’s disease (7)

Answer 1

Tyoically yound adults (15-30), with second smaller peak age 60-70.
Discontinuous involvement of entire GI tract.
Stomach - usually involved antrum, causing rams horn deformity.
Duodenal involvement is rare and never without antrum involvement.
Small bowel involved 80% of time, TI almost always involved (marked narrowing = string sign).
After surgery, neo-terminal ileum is usually involved.
Colon - usually right sided, often spares rectum/sigmoid.
Complications include fistulae, abscess, gallstones, fatty liver and sacroiliitis.

Question 2

Crohn’s buzzwords (8)

Answer 2

Squaring of the folds - early manifestation from obstructive lymphoedema
Skip lesions - discontinuous involvement of bowel
Proud loops - separation of loops caused by mesenteric infiltration, increase in mesenteric fat and enlarged nodes.
Cobblestoning - irregular appeartance of bowel wall caused by longitudinal and transverse ulcers separated by areas of oedema
Pseudopolyps - Islands of hyperplastic mucosa.
Fusiform - post inflammatory polyps - long and worm like
Pseudodiverticula - Found on anti-mesenteric side, from bulging area of normal wall opposite side of scarring from disease
String-sign - Marked narrowing of nerminal ileum from combination of oedema, spasm and fibrosis

Question 3

Ulcerative colitis (7)

Answer 3

Usually young adult (15-40), second oeak at 60-70.
Favours males.
95% involve rectum, with retrograde progression.
Terminal Ileum involved 5% with backwash ileitis (wide open appearance).
Continuous, not skip lesions.
Associated with colon cancer, PSC, arthritis (similar to ank spond).
Ahaustral colon on barium, with diffuse granular appearing mucosa. “Lead pipe”, shortened from fibrosis.
Increased risk of cancer and no enlarged lymph nodes, unlike crohns.

Question 4

UC vs Crohns (8)

Answer 4

Gallstones, Hepatic abscess and Pancreatitis more common in Crohn’s
PSC more common in UC
Continuous disease from rectum proximally vs discontinous skip lesions.
More common in rectum vs more common in TI.
Open iliocaecal valve vs stenosed.
Perirectal fat increased vs mesenteric fat increased.
Normal lymph nodes vs enlarged nodes.
No fistulas vs fistulas.

Question 5

Diverticular disease - trivia (3)

Answer 5

Diverticulosis bleeds more than diverticulitis.
Right sided is less common, but is seen in young asians.
Fistula formation most common with diverticulitis, can occur to anything around it (bowel, bladder, etc)

Question 6

Epiploic appendagitis/Omental infarct (5)

Answer 6

Both self limiting.
Epiploic appendages along the serosal surface of colon can tort, more commonly on left.
Not usually concentric bowel wall thickening, unlike diverticulitis.
Omental infarct is a larger mass with more oval shape, central low density.
More commonly on right.

Question 7

Appendicitis pathophysiology - (8)

Answer 7

Classic pathway:
Obstruction (faecolith or reactive lymphoid tissue)
–> mucinous fluid builds up increasing pressure
–> venous supply is compressed
–> necrosis starts
–> wall breaks down
–> bacteria get into wall
–> inflammation causes vague pain (umbilicus)
–> inflammed appendix gets larger and touches parietal peritoneum (RIF pain).

Question 8

Appendicitis - features (3)

Answer 8

Occurs in adolescent or yound adults mainly.
6mm usually used as a measurement of diameter for enlarged appendix.
Secondary signs of inflammation are probably a more reliable sign on CT

Question 9

Appendix mucocele (4)

Answer 9

Mucinous cystadenomas are commonest tumour of appendix.
Produce mucin, can get very dilated.
Look similar to cystadenomas and can perforate, causing pseudomyxoma peritonei.
Ultrasound, presence of onion sign (layering within cystic mass) is suggestive

Question 10

Colonic volvulus - types (3)

Answer 10

Sigmoid,
Caecal,
Caecal bascule

Question 11

Sigmoid volvulus (6)

Answer 11

Most common volvulus in adults.
Chronic constipation is a predisposing factor.
“Coffee bean sign”.
Less commonly “Frimann Dahl’s sign” - 3 dense lines converginf towards site of obstruction.
Points to RUQ.
50% recurrence after decompression.

Question 12

Caecal volvulus (3)

Answer 12

Younger person (20-40).
Associated with long mesentery.
More often points to LUQ.

Question 13

Caecal Bascule (2)

Answer 13

Anterior folding of the caecum without twisting.
Dilatation of caecum in ectopic position in the middle abdomen, without a mesenteric twist.

Question 14

Toxic megacolon (5)

Answer 14

UC then Crohns are commonest causes. C.diff can also cause.
Gaseous dilatation distends transverse colon on upright films, right and left colon on supine films.
Lack of haustra and pseudopolyps also seen.
High risk of perf, don’t do barium enema.
Peritonitis can occur without perf.

Question 15

Behcets (3)

Answer 15

Ulcers of the penis and mouth.
Can affect GI tract and look like crohn’s, most commonly affects ileocaecal region.
Also causes pulmonary artery aneurysms.

Question 16

Colonic pseudo-obstruction (4)

Answer 16

aka colonic ileus, Ogilvie syndrome.
Usually after serious medical conditions and nursing home residents.
Can persist for years or lead to bowel necrosis and perf.
Classic appearance is marked, diffuse dilatation of large bowel, without discrete transition point.

Question 17

Diversion colitis

Answer 17

Bacterial overgrowth in a blind loop, through which stool cannot pass (created by surgery)

Question 18

Colitis cystica (5)

Answer 18

Cystic dilatation of mucous glands, can be superficial or deep.
Superficial
- Small cysts across entire colon.
- Associated with vitamin deficiencies and tropical sprue.
- Can be seen in terminal leukaemia, uraemia, thyrotoxicosis and murcury poisoning.
Profunda
- Large cysts in pelvic colon and rectum

Question 19

Rectal cavernous haemangioma (3)

Answer 19

Rare.
Associated with Klippel-Trenaunay-Weber and Blue Rubber Bleb.
Can see many phleboliths.

Question 20

Gossypiboma

Answer 20

Abscess mimic, retained cotton product or surgical sponge. Can elicit inflammatory response.

Question 21

Entamoeba Histolytica (6)

Answer 21

Parasite causing bloody diarrhoea.
Can cause liver abscess, spleen abscess or brain abscess.
Can cause toxic megacolon.
“flask shaped ulcers” on endoscopy.
“Coned caecum” on barium, refers to change in normal bulbous appearance of caecum.
Typically affects caecum and ascending colon, spares the terminal ileum

Question 22

Colonic TB (4)

Answer 22

Typically involved TI, another cause of “Coned caecum”.
Causes ulcers and areas of narrowing.
Fleischner sign - enlarged, gaping IC valve.
Sterlin sign - narrowing of TI

Question 23

Colonic CMV (3)

Answer 23

Seen in immunocompromised.
Causes deep ulcerations, can lead to perf.
Pathology: Cowdry Type A intranuclear inclusion bodies.

Question 24

C-diff (5)

Answer 24

Often seen after antibiotic therapy.
Toxin leads to very high WBC.
CT: Accordion Sign - contrast trapped in mucosal folds.
Barium: Thumbprinting, ulceration and irregularity.
Can cause toxic megacolon

Question 25

Neutripenic Colitis (Typhilitis) (2)

Answer 25

Infection limited to caecum.
Occurs in severe neutropenia.

Question 26

Infection location DDx

Answer 26

Duodenum and proximal small bowel:
- Giardia, Strongyloides
Terminal ileum
- TB
- Yersinia

Question 27

Colon tumours - types (4)

Answer 27

Adenocarcinoma
Squamous carcinoma
Lipoma
Adenoma

Question 28

Adenocarcinoma (3)

Answer 28

no.2 cause of cancer death
Right sided cancers tend to bleed, left tends to obstruct.
Apple core is buzzword

Question 29

Colon squamous cell carcinoma (2)

Answer 29

Occasionally arises in the anus.
Think HPV

Question 30

Lipoma

Answer 30

Second commonest tumour in the colon

Question 31

Adenoma (2)

Answer 31

Commonest benign tumour of colon and rectum.
Villous adenoma has argest risk of malignancy

Question 32

McKittrick-Wheelock syndrome (2)

Answer 32

Villous adenoma that causes mucous diarrhoea, leading to severe fluid and electrolyte depletion.
Usually older person with diarrhoea, several reduced electrolytes and mass in rectum/bowel.

Question 33

Rectal cancer (6)

Answer 33

98% adenocarcinoma.
HPV is the cause of squamous cell ca.
Total mesorectal excision is standard surgical Rx.
Lower rectal Ca (0-5cm from anorectal angle) has highest recurrence rate.
MRI used for staging.
Stage T3 - tumour breaks out of rectum into perirectal fat, changes management (will get chemo/radiotherapy prior to surgery)

Question 34

Pseudomyxoma peritonei (3)

Answer 34

Gelatinous ascites due to ruptured mucocele (usually appendix) or intraperitoneal spread of mucinous neoplasm.
“Scalloped appearance of liver”
Recurrent bowel obstructions are common.

Question 35

Peritoneal carcinomatosis (2)

Answer 35

Natural flow of ascites determines location of implants.
Retrovesical space is most common location, most dependent part of peritoneal cavity.

Question 36

Omental seeding/caking (2)

Answer 36

Omental surface can get implanted by cancer, becoming thick like a mass.
“Posterior displacement of bowel” from anterior abdominal wall

Question 37

Primary peritoneal mesothelioma (2)

Answer 37

Rare. Mesothelioma involves pleura 75% of time, but involved peritoneal surface the other 25%.
Occurs 30-40 years after asbestos exposure.

Question 38

Cystic peritoneal mesothelioma (3)

Answer 38

Even more rare benign mesothelioma.
NOT associated with asbestos.
Seen in child bearing aged women

Question 39

Mesenteric lymphoma (3)

Answer 39

Usually non-hodgkin, involved mesentery 50% of time.
“sandwich sign”
Typically lobulated-confluent soft tissue mass encasing the mesenteric vessels, sandwiching them.

Question 40

Barium complications (7)

Answer 40

Barium peritonitis
- This is why water soluble is used whenever concern of leak.
- Attack of peritoneal barium by leukocytes, creating inflammatory reaction (massive ascites, sometimes hypovolaemia and shock).
- Rx: IV fluids to reduce hypovolaemia.
- Long term sequelae is granulomas and adhesions causing eventual obstruction
Barium intravasation
- Rare
- Barium ends up in systemic circulation, kills via pulmonary embolism 50% of time.
- Risk increased with inflammatory bowel or diverticulitis (altered mucosa)