3. GI p256-262 (Large Bowel, Peritoneal Cavity) Flashcards
Crohn’s disease (7)
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.
Crohn’s buzzwords (8)
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
Ulcerative colitis (7)
Usually young adult (15-40), second peak 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.
UC vs Crohns (8)
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.
Diverticular disease - trivia (3)
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)
Epiploic appendagitis/Omental infarct (5)
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.
Appendicitis pathophysiology - (8)
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).
Appendicitis - features (3)
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
Appendix mucocele (4)
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
Colonic volvulus - types (3)
Sigmoid,
Caecal,
Caecal bascule
Sigmoid volvulus (6)
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.
Caecal volvulus (3)
Younger person (20-40).
Associated with long mesentery.
More often points to LUQ.
Caecal Bascule (2)
Anterior folding of the caecum without twisting.
Dilatation of caecum in ectopic position in the middle abdomen, without a mesenteric twist.
Toxic megacolon (5)
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.
Behcets (3)
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.
Colonic pseudo-obstruction (4)
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.
Diversion colitis
Bacterial overgrowth in a blind loop, through which stool cannot pass (created by surgery)
Colitis cystica (5)
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
Rectal cavernous haemangioma (3)
Rare.
Associated with Klippel-Trenaunay-Weber and Blue Rubber Bleb.
Can see many phleboliths.
Gossypiboma
Abscess mimic, retained cotton product or surgical sponge. Can elicit inflammatory response.
Entamoeba Histolytica (6)
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
Colonic TB (4)
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
Colonic CMV (3)
Seen in immunocompromised.
Causes deep ulcerations, can lead to perf.
Pathology: Cowdry Type A intranuclear inclusion bodies.
C-diff (5)
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
Neutripenic Colitis (Typhilitis) (2)
Infection limited to caecum.
Occurs in severe neutropenia.
Infection location DDx
Duodenum and proximal small bowel:
- Giardia, Strongyloides
Terminal ileum
- TB
- Yersinia
Colon tumours - types (4)
Adenocarcinoma
Squamous carcinoma
Lipoma
Adenoma
Adenocarcinoma (3)
no.2 cause of cancer death
Right sided cancers tend to bleed, left tends to obstruct.
Apple core is buzzword
Colon squamous cell carcinoma (2)
Occasionally arises in the anus.
Think HPV
Lipoma
Second commonest tumour in the colon
Adenoma (2)
Commonest benign tumour of colon and rectum.
Villous adenoma has largest risk of malignancy
McKittrick-Wheelock syndrome (2)
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.
Rectal cancer (6)
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)
Pseudomyxoma peritonei (3)
Gelatinous ascites due to ruptured mucocele (usually appendix) or intraperitoneal spread of mucinous neoplasm.
“Scalloped appearance of liver”
Recurrent bowel obstructions are common.
Peritoneal carcinomatosis (2)
Natural flow of ascites determines location of implants.
Retrovesical space is most common location, most dependent part of peritoneal cavity.
Omental seeding/caking (2)
Omental surface can get implanted by cancer, becoming thick like a mass.
“Posterior displacement of bowel” from anterior abdominal wall
Primary peritoneal mesothelioma (2)
Rare. Mesothelioma involves pleura 75% of time, but involved peritoneal surface the other 25%.
Occurs 30-40 years after asbestos exposure.
Cystic peritoneal mesothelioma (3)
Even more rare benign mesothelioma.
NOT associated with asbestos.
Seen in child bearing aged women
Mesenteric lymphoma (3)
Usually non-hodgkin, involved mesentery 50% of time.
“sandwich sign”
Typically lobulated-confluent soft tissue mass encasing the mesenteric vessels, sandwiching them.
Barium complications (7)
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)
