Colon Flashcards

Question

13. A 45-year-old woman with a previous history of treatment for advanced carcinoma of the cervix 8 years earlier presents with constipation and rectal bleeding. She undergoes CT of the abdomen and pelvis, which demonstrates a narrowed rectum with symmetrical wall thickening, perirectal inflammatory changes, thickening of the perirectal fascia and an increase in the AP diameter of the presacral space. What is the most likely diagnosis? A. colorectal carcinoma B. ulcerative colitis C. radiation injury of the rectum D. Hirschsprung's disease E. lymphoma

Answer 1

The answer is: C Gastrointestinal complications following external radiotherapy are becoming more frequent as survival rates of patients with abdominal cancer improve, and they may present up to 15 years following irradiation. The colon and rectum are commonly affected following irradiation for pelvic and genitourinary tract malignancies. Chronic radiation colitis usually presents with strictures, whereas rectal injury manifests as a narrowed, thickened, poorly distensible rectum, with proliferation of the perirectal fat and thickening of the perirectal fascia. There is an increased incidence of colorectal carcinoma following pelvic irradiation, but a short irregular segment of narrowing would be more likely. Inflammatory bowel disease may result in circumferential rectal wall thickening with widening of the presacral space but is less likely given this history. Hirschsprung's disease usually presents in early childhood. The rectum is an uncommon site for gastrointestinal lymphoma.

Answer 2

b. typhlitis Typhlitis is acute inflammation of the caecum, appendix and occasionally terminal ileum, initially described in neutropenic children with leukaemia, but also seen with lymphoma, following immunosuppressive therapy and with clinical AIDS. Patients present with abdominal pain and diarrhoea, and may have a palpable, right lower quadrant mass. Characteristic findings are of circumferential caecal wall thickening, with oedematous bowel wall and inflammatory changes. Pericolonic fluid and intramural pneumatosis may be seen. Leukaemic deposits would be expected to cause more eccentric bowel wall thickening. Appendicitis may result in apical caecal wall thickening but would be accompanied by abnormal appendix. Crohn’s disease may produce a similar picture, but, in this clinical setting, typhlitis is the most likely diagnosis. Diverticulitis would be very unlikely in this age group.

Answer 3

(a) Ascending colon The ileocolic, right colic and middle colic lymph nodes are the regional drainage for the ascending colon (following arterial blood supply). All other nodal groups are considered distant metastases.

Answer 4

(b) Carcinoid Seen in up to 1.4%of histology specimens and is usually incidental. Other tumours are encountered less commonly. The presence of adenocarcinoma may necessitate a formal right hemicolectomy to resect the draining lymph nodes.

Answer 5

(d) it is the termination of the circular smooth muscle of the gastrointestinal tract The IAS comprises smooth muscle and is not under voluntary control. It appears hypoechoic on US. Obstetric injuries involve the external anal sphincter +/- IAS. Isolated injury is due to endo-anal trauma e.g. hemorrhoid surgery. Answers (a) and (e) pertain to the external anal sphincter, which is under voluntary control.

Answer 6

(b) Gardner's syndrome 5%Of colorectal carcinoma is genetic in origin; the most common inherited syndromes being familial adenomatous polyposis and hereditary non-polyposis colorectal cancer (Lynch syndrome; HNPCC). Gardner's syndrome is associated with polyposis in the colon (100%), duodenum (90%) and, rarely other bowel segments; there is an association with gastric hamartomas, osteomas in calvarium/ mandible and soft tissue tumours (30%). Turcot syndrome is a rare condition which is also associated with CNS gliomas and medulloblastomas. Peutz-Jegher’s syndrome consists of hamartomas throughout the Gl system with the rare potential for malignant transformation, and perioral pigmentation. Cowden disease has hamartomas, gingival hyperplasia, oral papillomas, muco-cutaneous pigmentation and an increased risk of breast and thyroid malignancy.

Answer 7

(e) Acute colonic pseudo-obstruction Acute colonic pseudo-obstruction (Ogilvie syndrome) is a rare condition that may be seen most commonly after trauma (including surgery), infection or with cardiac disease. The features mimic obstruction and complications include perforation. Gastrograffin enema may be therapeutic; air should never be insufflated in to the colon in these cases.

Answer 8

(c) 3 In the axial torsion type, the caecum twists around its long axis and remains in the right lower quadrant. In the loop type, the caecum twists around its long axis and also inverts. In the caecal bascule type, the caecum folds anteromedial to the ascending colon with no torsion. In the latter two scenarios, the caecum is found in the upper abdomen.

Answer 9

(b) Rectocele An anterior bulge of up to 3 or 4 cm may be normal in many cases, but beyond this, and with incomplete evacuation, the diagnosis of a rectocoelemay be made. Cystocoele and enterocoele are the abnormal descent of bladder and small bowel respectively. Prolapse is the abnormal descent of the rectum. Anismus is a functional abnormality leading to poor co-cordination Of the pelvic floor muscles.

Answer 10

(d) Increased number of folds in the ileum Jejunistion of the ileum is a feature of coeliac disease. In addition to the other features, transmural ulceration, fistulae, stenosis and fold thickening may be seen. Crohn's disease may affect any part Of the GI tract, from mouth to anus.

Answer 11

(e) Typhlitis Typhlitis (neutropenic colitis) represents acute inflammation of the caecum, appendix and occasionally terminal ileum. The aetiology is unknown, but profound neutropaenia appears to be universal. Mucosal injury from cytotoxic drugs during chemotherapy is thought to play an important role; infection may be involved (e.g.CMV). Lymphomatous deposits would be expected to produce a more eccentric thickening.

Answer 12

(b) Epiploic appendagitis Epiploic appendages are peritoneal fat outpouchings that arise from the serosal surface of the colon, attached by vascular stalks (supplied by 1-2 small end-arteries and a draining vein). They contain adipose tissue and vessels, and measure up to 5 cm (typically 1-2 cm). Epiploic appendagitis is inflammation secondary to torsion or venous occlusion. The most common location is anterior to the sigmoid colon, there is surrounding fat stranding, and a low-density (fat) center is seen; associated colon thickening is rare. Omental infarction can appear similar, but lacks the hyperdense ring enhancement and is more typically seen as an oval soft-tissue mass in the right lower quadrant, deep to the anterior abdominal muscles.

Answer 13

(b) Cronkhite Canada syndrome Cronkhite Canada syndrome is a rare non-familial condition with multiple hamartomatous polyps resulting in a protein-losing enteropathy. It is seen most commonly in Japan and the underlying cause remains unclear.

Answer 14

(a) Appendix Caused by Actinomycoces israelii, this is a rare condition which clinically mimics an appendix abscess. Sinus tracks, fistulae and a mass may all be seen at imaging. Risk factors include previous abdominal surgery, GI perforation, diabetes mellitus and steroid therapy.

Answer 15

(a) T3 disease threatening the circumferential resection margin Extension through the muscularis layer in to the mesorectal fat without invasion of other structures is T3 disease. Surgeons operating on rectal cancer perform a total mesorectal excision (TME) and remove the mesorectumen bloc. At least 3 clearance is required on MRI to confidently predict that the circumferential margin will be negative following TME. Neo-adjuvant chemo/radiotherapy is usually given to patients in this instance.

Answer 16

(c) 2.6 % The likelihood of there being advanced neoplasia (high grade dysplasia or > 25% villous adenoma) or malignancy in a polyp is, respectively, 1.7% and <0.1% for a polyp <5mm, 6.6% and 0.2% for a polyp measuring 6-9 mm, and 30.6% and 2.6% for a polyp measuring 1 cm or more.

Answer 17

(e) Colon CMV is one of the most common causes of enteric disease in AIDS patients, usually affecting those with a CD4 count < 100. The colon is the most commonly affected site, followed by the small bowel, oesophagus and stomach.

Answer 18

(c) T3 Lesions <2 cm are TI 2-5 cm are T2 > 5 cm are T3. T4 lesions are those invading adjacent organs. There is no T 5 category. Depth of invasion is irrelevant with the exception of T4 disease.

Answer 19

(e) Granularity The granular appearance on barium enema is typical. UC is typically contiguous from the rectum and appears symmetrical. In chronic dis, fibro-fatty proliferation is seen in mesorectum, there is submucosal fat deposition.

Answer 20

(a) Caecum Lipomas are relatively common sub-mucosal lesions in the GI tract, seen in 4.4% of patients at autopsy, and may be solitary or multiple. the colon, 45% of these are seen in the caecum.

Answer 21

(e) Intersphincteric fistula There are 4 types of fistula (b) - (e), with the intersphincteric type the only one that does not pass through the external sphincter (hence it is always medial to it). If a fistula extends around both sides of the anal canal, this is termed a horseshoe extension.

Answer 22

(b) T2 T2 weighted images best depict the appendix, but a STIR sequence is sensitive for identifying an inflamed and oedematous appendix. MRI has a sensitivity, specificity and accuracy of over 90% for the diagnosis of acute appendicitis.

Answer 23

(e) Sigmoid volvulus These are the classical radiological features of sigmoid volvulus on the plain abdominal film. The sigmoid is prone to twisting as it has a short mesentery and when it does so, it rotates anti-clockwise and may become ischemic. It is seen more commonly in the elderly with constipation, in those with high fibre diets, and in children. Decompression alone will lead to representation in 50% within 2 years.

Answer 24

(d) Skip lesions indicate co-infection or underlying Crohn's disease Clostridium difficile, the organism which causes pseudomembranous colitis, acts through the release of endotoxins which produce diarrhoea and abdominal pain. The use of PPIs increases the survival of vegetative matter in the stomach and is strongly associated with this condition. The colon may be affected from the rectum to the caecum in a variety of patterns.

Answer 25

(c) Sacroiliitis Crohn's disease is more commonly associated with a peripheral, migratory, non-deforming seronegative arthropathy.

Answer 26

(d) NSAIDs increase the risk of perforation Rectal involvement is rare, with localised right colonic disease seen in around 5% of cases whilst sigmoid disease accounts for 80%. Giant diverticulae most commonly arise in the sigmoid colon, but bleeding is more common from the right colon. Glucocorticoids also increase the risk of perforation.

Answer 27

4. e. Presence of haustral markings Sigmoid and caecal volvulus can sometimes be difficult to differentiate on plain abdominal film. With caecal volvulus the haustral markings are typically present, whereas these are usually absent in sigmoid volvulus. The pelvic overlap, liver overlap and coffee bean signs are typical of sigmoid volvulus. In sigmoid volvulus the apex lies high in the abdomen underneath the left hemi-diaphragm, typically above the level of T10.

Answer 28

5. b. Epiploic appendagitis Epiploic appendagitis is inflammation of one of the epiploic appendages of the colon, with the sigmoid being the commonest site. It typically presents with acute abdominal pain and is an important radiological diagnosis as it can often mimic appendicitis, and management is conservative. The diagnosis is usually made on CT with the features described in the question. Ultrasound is rarely used for diagnosis, and features include a non-compressible hyperechoic mass with hypoechoic margins.

Answer 29

6. a. Typhlitis Typhlitis, or neutropenic enterocolitis, is acute inflammation of the caecum, ascending colon, terminal ileum or appendix. It is typically described in children with neutropenia secondary to lymphoma, leukemia and immunosuppression. Concentric, often marked, bowel wall thickening with pericolic inflammatory changes is typical, and such changes in a young immunosuppressed child should raise suspicion of typhlitis as a cause. Perforation is a risk factor and therefore contrast examinations are usually avoided.

Answer 30

13. b. Cystadenocarcinoma of the appendix The CT findings described are consistent with pseudomyxoma peritonei. This describes abdominal distension secondary to the accumulation of large quantities of gelatinous ascites. It is most commonly caused by cystadenocarcinoma of the appendix in males and cystadenocarcinoma of the ovary in females. Surgical debulking and intraperitoneal chemotherapy may be offered as a treatment. Bowel obstruction is a frequent complication that may necessitate surgery.

Answer 31

14. c. Ischaemic colitis Crohn’s colitis is relatively unlikely due to lack of prior history or small bowel involvement and age of the patient. Ulcerative colitis and pseudomembranous colitis are both unlikely as the rectum is usually involved in these two conditions. Infectious colitis does not normally affect the left-sided colon only, regardless of the underlying pathogen. Ischaemic colitis is the most likely diagnosis of those listed. It typically affects a segment of bowel, with the majority of cases having left-sided colonic involvement.

Answer 32

19. a. Peutz–Jegher’s Peutz–Jegher’s syndrome is most consistent with these findings. It is an autosomal dominant syndrome but often arises as a spontaneous mutation. Hamartomas are found throughout the gastro-intestinal tract, with the exception of the oesophagus. The polyps have almost no malignant potential, but life expectancy is decreased due to associated cancers arising in the stomach, duodenum, colon and ovary. Gardner’s syndrome and familial polyposis are both associated with small bowel adenomas in approximately 5% of cases. Cowden’s syndrome does involve hamartomatous polyps, but these are typically rectosigmoid, and small bowel involvement is not a feature. Small bowel polyps are not a feature of Turcot’s syndrome.

Answer 33

20. d. Gardner’s syndrome Gardner’s syndrome is an autosomal dominant condition with colonic polyps present in all patients. Small bowel, duodenal and stomach polyps are also a feature. Extra-intestinal features include osteomas of membranous bone (typically the mandible as described in the question), other soft-tissue tumours and periampullary carcinomas. Osteomas are not a feature of the other conditions. Cronkhite–Canada syndrome and Peutz–Jegher syndrome are associated with multiple hamartomatous polyps of the colon and stomach. Cronkhite– Canada syndrome is a sporadic non-familial disorder. Lynch syndrome, or hereditary nonpolyposis colorectal carcinoma (HNPCC), is associated with increased risk of colorectal adenomas and other malignancies such as endometrial and other gastro-intestinal tract malignancies.

Answer 34

30. b. Plain abdominal film Toxic megacolon is a complication of ulcerative colitis, Crohn’s and other forms of acute colitis. It has a poor prognosis with up to 20% mortality. Plain abdominal radiography should be the first line investigation for suspected toxic megacolon, and can be repeated 24 or 48 hourly if necessary. It can often confirm the diagnosis without the need for CT, which is especially useful when considering radiation dose issues in this group of young patients. Typical features on plain film include transverse colon dilatation >5.5 cm, loss of normal haustral folds, thumbprinting of the colon and the presence of mucosal islands (pseudopolyps). CT better demonstrates potential complications of toxic megacolon such as perforation of the bowel.

Answer 35

31. a. Crohn’s disease These features are highly suggestive of Crohn’s disease. Signs on double contrast barium enema that favor a diagnosis of Crohn’s disease over ulcerative colitis include apthoid ulcers, deep ulcers, discontinuous ulceration, rectal sparing, pseudodiverticulae, fistulae and abscess formation. Ulcerative colitis can be suggested by rectal involvement, continuous pathology with no skip lesions and the presence of mucosal granularity. However, these features may also be present in Crohn’s and are not specific for ulcerative colitis. Although tuberculosis is a mimic, colonic involvement in this pattern is uncommon compared with Crohn’s disease.

Answer 36

33. a. Angiodysplasia The typical angiographic feature of a Meckel’s diverticulum is presence of the vitelline artery. Meckel’s diverticulum also typically (although not exclusively) presents in younger patients. With diverticulosis, radiation enteritis and polyps, one might expect an abnormal barium enema, and in addition these angiographic features are not typical. Angiodysplasia is the second most common cause of gastro-intestinal bleed in the elderly population after diverticular disease. It is due to dilatation of the submucosal vessels and occurs most commonly on the right side of the colon. Angiographic features include visualisation of a cluster of vessels on the antimesenteric border, early filling of the ileocolic vein in the arterial phase and delayed emptying of the same vein.

Answer 37

34. e. Tailgut cyst Tailgut cysts or cystic hamartomas are presacral, multilocular, mucous-secreting cysts found distal to the normal embryonic termination of the hindgut. Small cysts may be asymptomatic, but larger cysts may present with rectal pain or bleeding, constipation, anal fistulae or recurrent rectal abscesses. A long and tail-like coccyx is often associated, and can help distinguish between many other cystic lesions in this region. Malignant transformation is a complication, most commonly adenocarcinoma. Duplication cysts are most often unilocular unless complicated by haemorrhage or infection, a meningocele is likely to arise from the sacral foramina, piercing the presacral fascia, and dermoid tumour would be expected to contain fat or layering of contents as seen in dermoid tumours in otherlocations.

Answer 38

47. b. Pseudomembranous colitis Pseudomembranous colitis results from overgrowth of Clostridium difficile most commonly due to broad spectrumantibiotic use in the hospital population.Ascites is often present in severe cases and wall thickening >10mm is highly suggestive of this diagnosis. A layered pattern of enhancement is often present in severe cases with oedema in the submucosa producing low attenuation in the wall, deep to the enhancing mucosa. The accordion sign is caused by marked submucosal oedema producing thickening of the colonic haustra. The rectum is involved in the majority of cases but any location within the large bowel may be involved.

Answer 39

56. d. Loss of visualisation of hyperechoic submucosa The use of ultrasound for the diagnosis of acute appendicitis is particularly useful in children and women of child-bearing age. Findings indicating acute appendicitis include a tubular non-compressible blind-ending structure with diameter >6 mm and wall thickness >2 mm, although these signs do not necessarily indicate perforation. Features suggesting perforation include a fluid collection adjacent to the appendix, gas bubbles near the appendix and loss of visualisation of the submucosal layer.

Answer 40

57. c. T2 The layers of the rectum are well demonstrated at transrectal ultrasound. The innermost hyperechoic layer represents the balloon-mucosa interface, the middle hyperechoic layer represents the submucosa and the outermost hyperechoic layer represents the serosa. The tumour described in the question extends through the submucosa into the muscularispropria (outer hypoechoic layer) but does not involve the serosa. T1 disease is limited to the submucosa, T2 is limited to the muscularispropria, T3 extends through the serosa and T4 represents invasion of adjacent organs. The correct staging for tumour described in the question is therefore T2.

Answer 41

D The sensitivity of graded compression ultrasound in suspected acute appendicitis is 75—90%. Graded compression ultrasound of the appendix can avoid unnecessary surgery and ionising radiation particularly relevant for children and women of childbearing age. The finding of a non-compressible appendix with transverse diameter of 6 mm or greater is highly suggestive of acute appendicitis (specificity 86-100%). Other ultrasound findings include hyperechoic fat in the right iliac fossa, peri-appendiceal fluid or a pelvic fluid collection (appendiceal abscess)

Answer 42

B Multiple mucosal islands in a dilated transverse colon The presence of severe ulceration leading to mucosal islands is a major sign of toxic megacolon (the other key finding is colonic dilatation > 5 cm).

Answer 43

E T4 Evidence of peritoneal invasion indicates stage T4 rectal cancer.

Answer 44

A Haustrae are visible in the gas-filled viscus. The presence of haustrations in a dilated viscus and gas in the appendix are key to the diagnosis of caecal volvulus.

Answer 45

B Familial adenomatous polyposis Autosomal dominant condition with multiple colonic adenomas and 100%risk of colorectal carcinoma 20 years after diagnosis. Associated with hamartomas in stomach, gastric & duod adenomas & periampullary carcinoma.

Answer 46

D Endoanal ultrasound High-frequency endosonography allows an accurate assessment of the four layers of the anal wall; superficial and deep mucosa, submucosa and muscularis propria.

Answer 47

B Endometriosis Involvement of the GI- tract is not uncommon in endometriosis and the sigmoid colon and pelvic small bowel loops are typical sites of involvement.

Answer 48

C On ultrasound, the lesion changes shape when compressed. Known as the 'squeeze sign’.

Answer 49

E The use of an antispasmodic (eg Buscopan) immediately prior to gas insufflation enables optimal colonic distension. CT colonography (CTC) is accepted as a generally safe technique with a reported perforation rate in symptomatic patients of 0.03% (compared with 0.13% with optical colonoscopy). Supine and prone imaging is widely advocated in CTC to maximise colonic distension and discriminate between faecal/ fluid bowel residue and genuine pathology, while the use of an antispasmodic is advised to avoid colonic spasm. There is no strong evidence that intravenous contrast improves detection of colonic lesions, but it may be of benefit in symptomatic patients as it enables a more accurate assessment of extracolonic pathology.

Answer 50

A A thickened segment of sigmoid colon with mesenteric stranding and a small pericolonic fluid collection The history is typical of acute diverticulitis. These CT findings would be consistent with ‘moderate’ diverticulitis with a small pericolonic abscess.

Answer 51

A Gastroenteritis with incidental pneumatosis coli The presence of cyst-like gas pockets in the left hemicolon of a patientwith COPD is suggestive of pneumatosis cystoides intestinalis (pneumatosis coli).

Answer 52

C Neutropenic colitis The patient is highly likely to be severely neutropenic at this stage and the CT findings are typical of neutropenic colitis.

Answer 53

C Intersphincteric The Parks' classification defines anal fistulae by the structures involved. The intersphincteric fistula is the most common of anal fistulae (around 70%) and does not pass through the external sphincter. A trans-sphincteric fistula will cross both the internal and external sphincters to reach the skin surface while a suprasphincteric fistula passes above the puborectalis muscle to involve the ischiorectal fossa. The least common fistula is the extrasphincteric fistula as this arises from the rectum and passes through the levator ani muscles to reach the skin surface without involving the anal sphincter mechanism at all.

Answer 54

A Colonic pseudo-obstruction is a recognised cause of these radiographic findings. Colonic pseudo-obstruction can produce the same radiographic findings as large bowel obstruction: an instant contrast enema or CT should differentiate mechanical obstruction from pseudo-obstruction.

Answer 55

B Ascites is present in up to 40% of patients. Ascites can occur with other colitides, but is often seen in pseudomembranous colitis. CT typically demonstrates mucosal enhancement and marked colonic wall thickening but only mild pericolonic stranding, in patients with pseudomembranous colitis. These findings have a high positive predictive value but a normal CT does not exclude pseudomembranous colitis. Rectal sparing occurs in around 10% of patients.

Answer 56

B Epiploic appendagitis Torsion of an epiploic appendage leads to sudden onset of localised pain with characteristic CT findings of a pericolic inflammatory mass with central fat density.

Answer 57

C The majority of strictures in UC are benign. Benign strictures in UC are typically smooth and symmetrical and are due to chronic smooth muscle hypertrophy. These occur in 10—20% of patients with UC and are most common in the left colon. Carcinomas arise from dysplastic changes within diseased epithelium and not from adenomas as in the general population.

Answer 58

C The lesion is of homogeneous attenuation. A polyp will usually demonstrate uniform soft tissue density, similar to the surrounding bowel wall.

Answer 59

C Ischaemic colitis Stricture formation (with barium sacculation on double contrast enema) can occur in the splenic flexure due to fibrosis of the ischaemic bowel.

Answer 60

A Aphthous ulceration interspersed with areas of normal mucosa Aphthous ulceration is the earliest sign of Crohn's disease on a double contrast barium enema. The other options are all true of ulcerative colitis from the earliest signs of fine mucosal granularity to the ‘lead pipe’ appearance of the colon in chronic UC. Submucosal ulceration can extend laterally in UC giving the ‘collar button’ appearance.

Answer 61

D No stricture demonstrated An instant enema can exclude mechanical obstruction in patients with colonic pseudo-obstruction.

Answer 62

9. D. Adjacent abscess formation. Abscess formation has been found to be the most specific finding in appendiceal perforation, along with extraluminal gas and small bowel ileus. Abscess formation is also one of the least sensitive findings. Regional mesenteric lymph nodes are the most sensitive, but are reasonably non-specific. A focal wall defect, if seen, is reasonably sensitive and specific. Appendicolith is only found in 50% on CT and has a specificity of 70%.

Answer 63

22. D. Crohn’s disease. The findings described are classical for Crohn’s disease and lymphadenopathy is seen in up to 30% of cases. Tuberculosis more typically involves the caecum. Lymphoma usually causes a nodular appearance to the bowel. It is not associated with stricturing of the affected segment and is more classically associated with dilatation of the affected segment due to destruction of the myenteric plexus.

Answer 64

50. C. Epiploic appendagitis. Acute epiploic appendagitis is a self-limiting inflammation of the appendices epiploicae, associated with obesity, hernia, and unaccustomed exercise. Omental infarction typically presents with pain of several days’ duration. CT demonstrates a large non-enhancing omental mass with heterogenous attenuation, and is typically located towards the right lower quadrant. Sclerosing mesenteritis is commonly located at the root of the small bowel mesentery.

Answer 65

52. D. T3, N1, M0. T3 implies invasion beyond the muscularis propria into the pericolic fat. CT is quoted as 80% accurate in detecting extramural spread and nodal stage. T1 and T2 tumours are well-defined with no extension beyond the bowel contour. CT features of a T4 tumour include nodular penetration of the tumour through the peritonealized areas of the muscle coat or an advancing edge of the tumour penetrating adjacent organs. Nodal positivity is based on any node >1 cm or a group of three or more nodes.

Answer 66

55. D. Pseudomembranous colitis. The CT sign of oral contrast becoming trapped between thickened oedematous haustral folds is the ‘accordion’ sign, which is highly suggestive of pseudomembranous colitis. Bowel wall thickening, pericolonic stranding of fat, and ascites may be seen in all forms of colitis. Pseudomembranous colitis can be segmental, but is more commonly a pancolitis.

Answer 67

A. Small bowel obstruction, as can occur in up to 30% of these patients. Total colonic resection with J pouch anastomosis is carried out in patients with ulcerative colitis or familial adenomatous polyposis (FAP) in order to resect the entire colon, but retain anal defaecation. One of the main contraindications to total colectomy and J pouch formation is Crohn’s disease and such a procedure is uncommonly carried out in this situation due to the high recurrence rate. Pouchitis and small bowel obstruction both occur in up to 30% of patients who undergo this procedure. The radiological features of pouchitis are non-specific, but include wall thickening and increased enhancement of the bowel wall, with peripouch fat-stranding. Fat-stranding on its own is common as a result of both the surgery and possible inflammatory change due to previous proctitis. Small bowel obstruction most commonly occurs in the region of the ileostomy. Free fluid is often seen in small bowel obstruction. The absence of fluid cavities or air pockets is against a leak from the pouch anastomosis and the clinical features are not consistent with fistula. The blind ending lumen described is the normal appearance seen on a pouchogram.

Answer 68

61. A. Benign tumour. The patient has presented with a colo-colic intussusception secondary to a lipoma of the colonic wall. The intussusception has been complicated by large bowel obstruction. Intussusception is caused by prolapse of a portion of the bowel into the lumen of the adjoining bowel lumen segment. Intussusception is most commonly a disease of young children and most commonly occurs in an ileocolic location. In children, over 90% of intussusceptions are idiopathic and no lead point is identified. In adult patients approximately 80% of intussusceptions are caused by lead point lesions. The CT appearances described are typical of an intussusception. The low attenuation distal lead point represents the lipoma. Ultrasound is often used to diagnose intussusception in children and will show a mass with echogenic rings representing the fat in the invaginated mesentery.

Answer 69

69. C. Rectosigmoid. On a prone scan during a CT colonography examination, the rectosigmoid is generally better distended than on the supine scan because it is a more posteriorly placed structure and air gets displaced to the non-dependent position. The other segments named are usually better distended on the supine scan, particularly the caecum and transverse colon, as these are more anteriorly placed within the abdomen.

Answer 70

73. C. Mucosal hyperenhancement. The lack of ionizing radiation is a major advantage to MRI for patients with Crohn’s disease given the chronic nature of this condition necessitating frequent investigation. MRI can be performed via enterography or enteroclysis. In enterography, large volumes of fluid (or a fluid inducing laxative) are ingested. Enteroclysis involves administration of enteric contrast material via a nasoenteric tube. Sequence acquistion involves fat suppression and intravenous contrast. Increased mucosal hyperenhancement (compared with that seen in normal surrounding loops) may be the earliest sign of active inflammation, even in the absence of wall thickening. Increased vascularity, perienteric inflammation, and reactive adenopathy are other signs of active Crohn’sdisease. In severe Crohn’s disease mucosal hyperenhancement combined with submucosal oedema gives a ‘stratified’ appearance. Serosal hyperenhancement may also be seen, giving a‘target’ appearance. Mural thickening is defined as greater than 3mm, although an underdistended bowel may mimic this finding.

Answer 71

74. B. Turcot syndrome. FAP is a rare autosomal dominant condition resulting in the growth of hundreds of adenomatous polyps in the large bowel. Clinical symptoms commence from the third decade and include abdominal pain and PR bleeding. Colorectal cancer develops in almost all before the age of 40years. Turcot syndrome is characterized by the association of colonic polyps similar to FAP and central nervous system tumours, typically medulloblastoma and glioblastoma multiforme. The combination of intestinal polyposis (identical to FAP) and numerous osteomas and epidermal cysts is typical of Gardner syndrome. Lynch syndrome is hereditray non-polyposis colorectal cancer. Colorectal carcinoma occurs earlier than in the average population. There is also anassociation with ovarian and endometrial malignancy. Chronic inflammatory bowel disease is not associated with CNS malignancy.

Answer 72

74. E. Peutz–Jehger’s syndrome. This is an autosomal dominant disease with incomplete penetrance characterized by intestinal polyposis and mucocutaneous pigmentation. It is the most frequent of the polyposis syndromes to involve the small intestine. When symptomatic, the most common presentation is abdominal pain (due to small bowel intussusception in up to 50%). There may also be GI haemorrhage. There is an increased risk of malignancy of the GI tract, pancreas, and breast, even though the polyps are hamartomas. Cronkhite–Canada syndrome is non-neoplastic, non-hereditary inflammatory polyposis associated with ectodermal abnormalities. It usually occurs in the middle-aged to elderly and the polyps are more common in the stomach and colon than in the small bowel. Intussusception is not a typical presentation. Gardner syndrome is an autosomal dominant disease characterized by a triad of colonic polyposis, osteomas, and soft-tissue tumours (including desmoid tumours). Age at presentation is 15–30 years. The location of the polyps is colon (100%), duodenum (90%), stomach (5–58%), and the remainder of the small bowel (<5%). Small bowel intussusception is therefore a very rare presentation. There is a very high risk of malignant transformation of the colonic polyps if left untreated. Treatment is prophylactic total colectomy. Familial adenomatous polyposis syndrome is an autosomal dominant disease. The polyps start to appear around puberty and have a similar distribution/location to those in Gardner syndrome. Again there is a high risk of malignant transformation of these adenomatous polyps. Cowden disease is multiple hamartoma syndrome. It causes hamartomatous neoplasms of the skin and mucosa, GI tract, bones, CNS, eyes, and genitourinary tract. There may be associated malignant tumours of the breast and thyroid.

Answer 73

C. Insulinoma is a contraindication to the use of glucagon. Glucagon is a potent hypotonic agent. If 1mg of glucagon is injected intravenously it takes approximately 1 minute to work and lasts about 10–20 minutes. Intravenously administered glucagon decreases discomfort during barium enema examinations. Glucagon administration is generally safe, but is contraindicated in patients with insulinoma and phaeochromocytoma. Diabetes is not a recognized contraindication.

Answer 74

Answer C: Epiploic appendagitis Epiploic appendagitis (EA) is uncommon and is due to inflammation of one of the 100 or so epiploic/omental appendages that arise from the serosal surface of the colon. Histology shows acute infarction with fat necrosis, inflammation and thrombosed vessels with haemorrhagic suffusion, but if recognised on CT it can usually be treated conservatively with spontaneous resolution within two weeks. CT appearances resolve by six months. The typical patient is a male in their forties.

Answer 75

Answer C: Transverse colon The transverse colon is the area of bowel where these changes are most commonly seen, probably because it is the least dependent part in the supine position. A mean dilatation of 80 mm is seen in florid cases, but anything over 55 mm is worrying. Sometimes ulceration is so extensive that no mucosal islands remain.

Answer 76

Answer D: Intersphincteric An intersphincteric fistula passes through the internal sphincter and then between the internal and external to the perianal area.

Answer 77

Answer E: Bowel distension to the splenic flexure Bowel distension of the splenic flexure (i.e. the perfusion territory of the superior mesenteric artery) is seen in approximately 40-45 % of cases. The other options are all features of ischaemia but are not specific to the superior mesenteric artery territory.

Answer 78

Answer C: Turcot syndrome Turcot syndrome is an autosomal recessive disease characterised by colonic polyposis and central nervous system tumours especially supratentorial glioblastoma and occasionally medulloblastomas. Malignant transformation of the polyps is expected.

Answer 79

Answer A: Crohn's disease Although Crohn's disease more frequently affects the small bowel, involvement of the stomach and duodenum occurs in up to 10% of patients. Typical appearances include aphthoid ulcers, erosions, cobblestone mucosa and thickened duodenal folds.

Answer 80

Answer B: T2, N2, MO.

Answer 81

Answer B: MRI pelvis and CT chest.

Answer 82

Answer D: MRI pelvis MRI is now the modality of choice for recurrent perianal sepsis as it can delineate the anatomy and identify collections and fistulae.

Answer 83

Answer E: Shigella ` The pattern of colonic involvement can give useful clues to the causative organism in infectious colitis. Organisms that cause colitis limited to the right colon include Shigella and Salmonella.

Answer 84

Answer B: Ascites CT is abnormal in 60% of cases of pseudomembranous colitis. Marked colonic wall thickening is the commonest manifestation. Ascites occurs in 35%.

Answer 85

Answer A: Linear ulcers on mesenteric border Linear ulcers on the mesenteric border are nearly pathognomonic of Crohn's disease. Ulcers are most commonly multiple in inflammatory bowel disease. Double tracking ulcers are usually seen in the colon in the context of ulcerative colitis.

Answer 86

26 Answer C: Rectal involvement Rectal involvement is commoner in ulcerative colitis (UC) (95%) than Crohn's (50%).

Answer 87

28 Answer A: Angiodysplasia of the colon Angiodysplasia of the colon is the most common vascular malformation of the GI tract and is due to vascular ectasia rather than a true arteriovenous malformation (AVM). It is caused by age related degenerative dilatation and is associated with aortic stenosis in 20%. It is most commonly seen in the caecum/ascending colon.

Answer 88

29 Answer C: Lynch II Lynch is otherwise known as hereditary nonpolyposis colorectal cancer syndrome. The Amsterdam criteria of this syndrome are based on relatives who have been diagnosed with colorectal cancer. (Three or more family members of whom two are first-degree relatives of the third, family members in two or more generations, one family member diagnosed <50 years old.) It is present in 5-10% of individuals with colon cancer. Lynch I has no association with extracolonic malignancies. Lynch II is associated with other malignancies including transitional cell carcinoma of the ureter and renal pelvis.

Answer 89

30 Answer D: Pulmonary disease There are over 60 causative factors for pneumatosis intestinalis. However, there are four main mechanisms by which they occur: bowel necrosis/gangrene, mucosal disruption, increased mucosal permeability and pulmonary disease. As a general rule pneumatosis of the colon is likely to be clinically insignificant and the extent of the pneumatosis is inversely related to the severity of the disease. A well man is unlikely to have ischaemic bowel and with a significant smoking history and probable symptomatic lung disease then pulmonary disease is the most likely cause. He has no good history for the other two mechanisms. Gas can be seen in the mesenteric and portal veins with pulmonary disease.

Answer 90

32 Answer C: Cytornegalovirus (CMV) CMV is the commonest cause of life-threatening opportunistic infection in AIDS patients and accounts for 13 % of all gastrointestinal disease in this population.

Answer 91

33 Answer D: Caecal volvulus Caecal volvulus accounts for 40% of all colonic volvuluses and is associated with malrotation and a long mesentery giving poor fixation of the right colon (10-25 % of the population). If caecal distension greater than 10-12 cm occurs, there is an increased risk of perforation or bowel infarction.

Answer 92

34 Answer B: Ileocaecal Crohn's disease is the third commonest cause of fistula after iatrogenic and diverticular fistulae. Enterocolic are most often between ileum and caecum; other fistula may occur: enterocutaneous (8-21 %), rectum to skin or vagina, peri-anal fistulae and sinus tracts.

Answer 93

35 Answer A: Ill-defined margins

Answer 94

36 Answer E: Sigmoid volvulus Sigmoid volvulus is common in elderly and psychiatric patients. The typical plain radiograph appearance is of a dilated loop of sigmoid with a distinct midline crease - the `coffee-bean' sign. Twisting of the mesentery is seen on CT.

Answer 95

28 Answer A: MR fistulography

Answer 96

29 Answer B: The inferior mesenteric artery is evaluated before the superior mesenteric artery The inferior mesenteric artery is usually evaluated first as once the patient's bladder begins to fill with contrast it may become more difficult to evaluate this area. The celiac axis is not routinely assessed when investigating lower gastrointestinal bleeding.

Answer 97

30 Answer D: T3 N1 MO

Answer 98

31 Answer C: Ischaemic colitis The commonest cause of acute ischaemic bowel is an occlusive superior mesenteric artery (SMA) embolus - in more than 50% of cases. Other causes are non-occlusive thrombus, SMA dissection and venous occlusion.

Answer 99

32 Answer B: Angiodysplasia This is due to age-related degeneration and dilatation of the submucosal vessels in the bowel wall and is the commonest vascular lesion of the GI tract. The caecum and ascending colon are most commonly affected followed by the descending and sigmoid colon. Less frequently, the small bowel may also be affected.

Answer 100

33 Answer E: Sigmoid volvulus This is commoner in the elderly and institutionalised populations. Varying degrees of torsion can occur, the commonest being through 360 degrees.

Answer 101

34 Answer B: <5 mm The normal pre-sacral space in adults in 95 % of cases is <5 mm and abnormal is > 10 mm.

Answer 102

35 Answer B: Lobulation

Answer 103

36 Answer B: Right hemicolon

Answer 104

Answer A: Crohn's disease The age of presentation of Crohn's disease is typically 15-30 years with an equal sex distribution. The symptoms are often vague and may be present for some time before the diagnosis is made. It can affect any part of the GI tract from the mouth to the anus and can skip segments.

Answer 105

63 Answer D: Non-compressible tubular structure >6 mm thick Ultrasound features of appendicitis are total thickness >6 mm, non-compressibility, wall thickness >3 mm and a shadowing appendicolith.

Answer 106

6. (a) Familial adenomatous polyposis A combination of extensive colonic polyposis with extracolonic features such as osteoma of the skull and mandible, epidermoid cysts, abnormal dentition and desmoid tumours is called Gardner’s syndrome and is now included as a part of the spectrum of familial adenomatous polyposis.

Answer 107

12.(b) Epiploic appendagitis The typical appearance of this is a 2–4 cm fatty lesion surrounded by a rim of tissue and inflammatory change next to colon. An important differential is acute diverticulitis, which commonly has a background of diverticulosis and colonic wall thickening

Answer 108

14. (b) Familial adenomatous polyposis By definition, hundreds of polyps have to be present for this diagnosis. It is an autosomal dominant condition and the polyps present around puberty. Almost all patients have duodenal adenomas, with a 5% risk of conversion to periampullary carcinoma. Juvenile polyposis is rare and presents in infancy. Multiple metaplastic polyps are very rare. Peutz–Jeghers syndrome shows few colonic polyps, and most are seen in the small bowel. Turcot’s syndrome is a rare association between colonic carcinoma and medulloblastoma.

Answer 109

17. (b) Angiodysplasia Angiodysplasia is associated with aortic stenosis and commonly found in the ascending colon. This is seen at the antimesenteric border. On angiography, there is cluster of vessels seen on arterial phase with early filling of the draining vessel. These can be small lesions and may be missed on colonoscopy.

Answer 110

28. (a) Enteric cyst Enteric cyst may be septated and filled with mucoid contents which return high signal on T1 images. On CT they have the characteristic features as in the case. Dermoid cysts contain skin appendages and commonly contain fat. Sacrococcygeal teratomas are usually seen in paediatric age group. On CT and MRI, they appear as heterogeneously enhancing lesions with both cystic and solid components.

Answer 111

29. (a) Mucocoele of the appendix A mucocoele is a chronic cystic dilatation of the appendiceal lumen caused by mucin collection. On ultrasound it is anechoic or hypoechoic, depending on the composition of mucous. On CT the lesion is homogenous and cystic. On MRI a mucocoele is hyperintense on T2 and hypo-isointense on T1.

Answer 112

31. (b) Typhlitis Given the history of acute myeloid leukaemia with chemotherapy, this is the most likely diagnosis

Answer 113

32. (a) Postinflammatory polyps Filiform polyps adhering to the colon by their bases are typical of postinflammatorypolyps, which can be seen in ulcerative colitis.

Answer 114

36. (b) Ischaemic colitis Ischaemic colitis is usually due to indolent non-occlusive atherosclerosis in the elderly. Colonic wall thickening in a watershed area suggests ischaemia as the aetiology. Risk factors include cardiovascular disease, diabetes, vasculitis, etc. On CT, there is colonic wall thickening (> 5 mm), in a watershed distribution. The colon wall may appear non-enhancing compared with normal colon or it may appear dense due to haemorrhage. Pneumatosis coli, portal vein gas and perforation may be found.

Answer 115

Answers: (a) Not correct (b) Not correct (c) Correct (d) Correct (e) Correct Explanation: Pseudomembranous colitis is caused by Clostridium difficile toxin. It most commonly affects the rectum. Ascites is a recognised feature in severe cases.

Answer 116

Answers: (a) Correct (b) Correct (c) Not correct (d) Not correct (e) Not correct Explanation: Ischaemic colitis is usually seen in patients >50 years of age. Barium enema is abnormal in 90% of the cases showing features of bowel wall thickening, loss of haustrations and thumbprinting. Evidence of portal vein gas is seen in very rae cases and is a preterminal sign.

Answer 117

Answers: (a) Correct (b) Correct (c) Correct (d) Not correct (e) Correct Explanation: Fistula formation is seen in 15% of the cases of complicated acute diverticulitis.

Answer 118

Answers: (a) Correct (b) Correct (c) Correct (d) Correct (e) Correct Explanation: The comb sign in crohn’s disease depicts the pericolic and perienteric fat stranding due to increased mesenteric vasculature. Disease can affect any part of the gastrointestinal tract from mouth to the anus however small intestine is most frequently involved particularly the terminal ileum.

Answer 119

Answers: (a) Correct (b) Not correct (c) Not correct (d) Correct (e) Not correct Explanation: CT features of pseudomembranous colitis are non-specific and include mural thickening with bowel dilatation. There is pancolitis & right-sided colitis. The rectosigmoid is spared in 67% of the cases and ascites is not uncommon. Complications include toxic megacolon on operation and peritonitis. Typhlitis is seen in neutropenia patients and usually presents as non-specific thickening of caecum and ascending colon due to necrosis.