Question 1: Crohn’s Disease (Active)
Stem: A 30-year-old man with known Crohn’s disease presents with acute abdominal pain and diarrhoea. A CT enterogram is performed, which demonstrates marked, symmetric wall thickening of the terminal ileum. The thickened wall shows intense, layered enhancement (mural hyperenhancement), and there is prominent engorgement of the adjacent vasa recta.
Question: The finding of engorged vasa recta is known as:
(A) The “String Sign” (B) The “Comb Sign” (C) The “Pride of the Omentum” Sign (D) The “Halo Sign” (E) The “Target Sign”
Correct Answer: (B) The “Comb Sign”.
Explanation:
- Why (B) is correct: The “comb sign” refers to the hyperaemic, engorged vasa recta that penetrate the bowel wall, resembling the teeth of a comb. This is a highly specific sign of active inflammation in Crohn’s disease.
- Why (A) is wrong: The “string sign” is a finding on barium studies, referring to a long segment of severe, fixed narrowing, characteristic of fibrostenotic (scarred) disease, not acute inflammation.
- Why (C) is wrong: The “pride of the omentum” (or “creeping fat”) is fibrofatty proliferation in the mesentery, which is a sign of chronic disease, not acute inflammation.
- Why (D) is wrong: The “halo sign” (or “target sign”) refers to the layered appearance of the bowel wall itself (e.g., submucosal oedema), which is also a sign of inflammation but is not the specific term for the vascular finding.
- Why (E) is wrong: See (D). “Target sign” and “halo sign” are often used interchangeably for the bowel wall appearance.
Key Points: Crohn’s Disease (Active Inflammation)
- CT Enterography is the imaging modality of choice.
- Hallmarks of Active Disease:
- Mural Hyperenhancement: The bowel wall enhances avidly, often in a layered “target” pattern.
- “Comb Sign”: Engorged, prominent vasa recta.
- Wall Thickening: The bowel wall is thickened (typically >3 mm).
- Submucosal Oedema: A low-density layer within the thickened wall.
- “Creeping Fat”: Fibrofatty proliferation in the mesentery; a chronic sign but often seen with active flares.
Question 2: Small Bowel Obstruction (SBO)
Stem: An 80-year-old woman with no prior surgical history presents with a 2-day history of abdominal distension, vomiting, and obstipation. A CT scan of the abdomen shows dilated loops of small bowel (up to 4 cm). In the right lower quadrant, the distal ileum is seen to be herniating through a defect in the pelvic floor, inferior to the obturator internus muscle.
Question: What is the most likely cause of this patient’s obstruction?
(A) Adhesive SBO (B) Gallstone Ileus (C) Obturator Hernia (D) Inguinal Hernia (E) Spigelian Hernia
Correct Answer: (C) Obturator Hernia.
Explanation:
- Why (C) is correct: This is a classic, though rare, cause of SBO. An obturator hernia is a hernia through the obturator foramen. It is most common in elderly, thin, multiparous women. The CT finding of bowel herniating between the pelvic floor muscles is diagnostic.
- Why (A) is wrong: Adhesions are the most common cause of SBO overall, but this patient has no surgical history. Furthermore, a specific hernia is identified.
- Why (B) is wrong: Gallstone ileus would show Rigler’s triad (pneumobilia, ectopic stone, SBO), not a hernia.
- Why (D) is wrong: An inguinal hernia is a hernia through the inguinal canal, which is in a different location (anterior).
- Why (E) is wrong: A Spigelian hernia is a ventral hernia through the Spigelian fascia, lateral to the rectus abdominis muscle.
Key Points: Small Bowel Obstruction (SBO)
- Imaging: CT is the modality of choice.
- Key Findings:
- Dilated small bowel loops (proximal to obstruction), defined as >2.5-3 cm diameter.
- Collapsed small bowel loops (distal to obstruction).
- “Transition Point”: The exact site where the bowel changes from dilated to collapsed.
- Look for the Cause: Always search for the cause at the transition point (e.g., adhesion, hernia, mass, gallstone).
Question 3: Carcinoid Tumour
Stem: A 60-year-old man presents with flushing and diarrhoea. A CT enterogram reveals a 1.5 cm, intensely enhancing nodule in the wall of the distal ileum. Arising from this nodule, there is a large, infiltrative, spiculated soft-tissue mass within the adjacent mesentery, which contains punctate calcifications and is causing kinking and retraction of the nearby bowel loops.
Question: This combination of a small primary tumour and a large desmoplastic reaction is classic for:
(A) Small Bowel Carcinoid (B) GIST (C) Lymphoma (D) Adenocarcinoma (E) Metastasis (e.g., from melanoma)
Correct Answer: (A) Small Bowel Carcinoid.
Explanation:
- Why (A) is correct: This is the pathognomonic appearance. Carcinoid tumours (a type of neuroendocrine tumour) are often small and avidly enhancing in the bowel wall (the “primary”). However, they secrete serotonin, which induces a severe fibrotic (desmoplastic) reaction in the mesentery. This results in a large, spiculated, calcified mesenteric mass that tethers and kinks the bowel, often being much larger than the primary tumour itself.
- Why (B) is wrong: A GIST is typically a large, exophytic, hypervascular mass itself; it does not cause a separate desmoplastic reaction.
- Why (C) is wrong: Lymphoma is a bulky, infiltrative, hypovascular mass that aneurysmally dilates the bowel; it does not cause a desmoplastic reaction.
- Why (D) is wrong: Adenocarcinoma is a focal, annular, “apple-core” lesion, not a desmoplastic mass.
- Why (E) is wrong: Metastases are typically multiple nodules and do not cause this specific reaction.
Key Points: Small Bowel Carcinoid
- Definition: Most common tumour of the small bowel, arises from neuroendocrine cells.
- Location: Classically in the distal ileum (within 60 cm of the ileocaecal valve).
- Imaging:
- Primary: Small, avidly enhancing, intramural nodule.
- Mesenteric Mass: The key finding. A spiculated, desmoplastic mass with calcifications.
- This mass tethers and kinks bowel loops, often causing obstruction or ischaemia.
- Clinical: Can cause carcinoid syndrome (flushing, diarrhoea) after it has metastasised to the liver.
Question 4: Gallstone Ileus
Stem: An 85-year-old woman presents with abdominal pain and vomiting. An abdominal CT scan shows dilated loops of small bowel, air within the gallbladder and biliary tree (pneumobilia), and a 3 cm, laminated, calcified stone lodged in the distal ileum, which is the transition point for the obstruction.
Question: This constellation of findings is known as:
(A) Bouveret’s Syndrome (B) Mirizzi Syndrome (C) Rigler’s Triad (D) May-Thurner Syndrome (E) Boerhaave Syndrome
Correct Answer: (C) Rigler’s Triad.
Explanation:
- Why (C) is correct: Rigler’s Triad is the classic set of 3 findings for gallstone ileus: 1) Pneumobilia (air in the biliary tree), 2) Small bowel obstruction, and 3) An Ectopic gallstone. This is caused by a cholecysto-enteric fistula (a fistula between the gallbladder and duodenum), which allows the stone to pass into the bowel.
- Why (A) is wrong: Bouveret’s syndrome is a specific type of gallstone ileus where the stone impacts in the duodenum, causing a gastric outlet obstruction.
- Why (B) is wrong: Mirizzi syndrome is when an impacted stone in the cystic duct externally compresses the common hepatic duct, causing jaundice.
- Why (D) is wrong: May-Thurner syndrome is the compression of the left common iliac vein by the right common iliac artery.
- Why (E) is wrong: Boerhaave syndrome is oesophageal rupture.
Key Points: Gallstone Ileus
- Definition: A mechanical small bowel obstruction caused by an impacted gallstone.
- Pathology: A cholecysto-enteric fistula (usually to the duodenum) allows the stone to enter the GI tract.
- Classic Site of Impaction: Distal ileum (the narrowest part of the small bowel).
- Rigler’s Triad:
- Pneumobilia
- Small Bowel Obstruction
- Ectopic Gallstone (at the transition point)
Question 5: Small Bowel Ischaemia
Stem: A 70-year-old man with atrial fibrillation presents with acute, severe abdominal pain that is “out of proportion” to the physical exam findings. A contrast-enhanced CT scan shows gas bubbles within the wall of the small bowel (pneumatosis intestinalis), gas within the portal vein, and a filling defect in the superior mesenteric artery (SMA).
Question: What is the most likely diagnosis?
(A) Crohn’s Disease (B) Small Bowel Obstruction (C) Acute Mesenteric Ischaemia (D) Intramural Haematoma (E) Ulcerative Colitis
Correct Answer: (C) Acute Mesenteric Ischaemia.
Explanation:
- Why (C) is correct: This is the classic presentation. The clinical clue is “pain out of proportion to exam.” The CT findings are pathognomonic for irreversible, transmural infarction:
- Pneumatosis intestinalis (gas in the bowel wall from necrotic, gas-forming bacteria).
- Portal venous gas (a grave, pre-terminal sign, as the gas escapes into the portal system).
- The filling defect in the SMA confirms the embolic cause (common in atrial fibrillation).
- Why (A) is wrong: Crohn’s disease is a chronic inflammatory process.
- Why (B) is wrong: SBO can cause ischaemia, but this patient has a primary embolic cause.
- Why (D) is wrong: A haematoma would be hyperdense (blood) in the wall, not hypodense (gas).
- Why (E) is wrong: Ulcerative colitis is a colonic disease.
Key Points: Acute Mesenteric Ischaemia
- Clinical: Sudden, severe pain “out of proportion” to the exam. High lactate.
- Cause: Most commonly arterial embolus (from AFib) to the SMA.
- Early CT Signs (Reversible):
- Lack of bowel wall enhancement.
- Bowel wall thickening (oedema).
- Late CT Signs (Irreversible Infarction):
- Pneumatosis intestinalis (gas in the wall).
- Portal venous gas.
- Bowel wall thinning (“paper-thin” wall).
Question 6: Coeliac Disease
Stem: A 35-year-old woman with a history of iron-deficiency anaemia and dermatitis herpetiformis undergoes a CT enterogram. The scan demonstrates atrophy of the jejunal folds and a corresponding increase in the prominence and number of the ileal folds. There is also a small-volume intussusception.
Question: This “reversal” of the normal fold pattern is a classic sign of:
(A) Coeliac Disease (B) Crohn’s Disease (C) Whipple’s Disease (D) Small Bowel Lymphoma (E) GIST
Correct Answer: (A) Coeliac Disease.
Explanation:
- Why (A) is correct: In coeliac disease (gluten-sensitive enteropathy), the immune response causes villous atrophy in the proximal small bowel (duodenum and jejunum). This results in a loss of the normal, feathery jejunal folds. The ileum, which is less affected, undergoes compensatory hypertrophy, leading to an increased number of folds. This is the “jejunoileal fold pattern reversal”.
- Why (B) is wrong: Crohn’s disease causes thickened, ulcerated folds, not atrophy.
- Why (C) is wrong: Whipple’s disease is a rare infection causing massively thickened, nodular folds in the duodenum.
- Why (D) is wrong: Lymphoma causes bulky, infiltrative masses or aneurysmal dilatation.
- Why (E) is wrong: GIST is a focal tumour.
Key Points: Coeliac Disease (Sprue)
- Pathology: Autoimmune response to gluten, causing proximal small bowel villous atrophy.
- Imaging (Barium or CT/MR Enterography):
- Jejunoileal Fold Pattern Reversal: (The key sign). Loss of jejunal folds, increased ileal folds.
- Villous atrophy (a “bald” jejunum).
- Transient intussusceptions (non-obstructing, due to dysmotility).
- Complications: Hyposplenism (functional asplenia), increased risk of small bowel lymphoma and adenocarcinoma.
Question 7: Adult Intussusception
Stem: A 50-year-old man presents with intermittent, colicky abdominal pain. A CT scan is performed, which shows a 3 cm, avidly enhancing, nodular mass in the wall of the proximal ileum. This mass is acting as a “lead point”, dragging the proximal ileum into the distal ileum, creating a “bowel-in-bowel” or “target” appearance.
Question: The finding of a “lead point” is most characteristic of:
(A) Paediatric intussusception (B) Adult intussusception (C) Coeliac disease (D) Small bowel ischaemia (E) Gallstone ileus
Correct Answer: (B) Adult intussusception.
Explanation:
- Why (B) is correct: Unlike paediatric intussusception (which is usually idiopathic/lymphoid hyperplasia), adult intussusception (>90% of cases) has an underlying pathological lead point. This is most commonly a benign or malignant tumour (e.g., GIST, lipoma, metastasis, carcinoid) that the bowel’s peristalsis “grabs” and pulls forward.
- Why (A) is wrong: Paediatric intussusception is typically idiopathic and transient, with no lead point identified.
- Why (C) is wrong: Coeliac disease can cause transient intussusceptions, but these are without a lead point.
- Why (D) is wrong: Ischaemia causes wall thinning and pneumatosis, not intussusception.
- Why (E) is wrong: Gallstone ileus is a mechanical obstruction from a stone, not a telescoping of the bowel.
Key Points: Intussusception
- Definition: Telescoping of a proximal bowel segment (the intussusceptum) into a distal segment (the intussuscipiens).
- CT Appearance: “Bowel-in-bowel” or “target” sign, often with mesenteric fat and vessels trapped inside.
- Paediatric: 90% idiopathic (lymphoid hyperplasia), ileocolic, often resolves with air enema.
- Adult: 90% have a pathological lead point (tumour, polyp). Usually requires surgical resection.
Question 8: GIST (Small Bowel)
Stem: A 65-year-old man presents with an acute GI bleed and anaemia. A CT angiogram reveals a 9 cm, heterogeneously enhancing mass arising from the jejunum. The mass is growing exophytically (outwards) from the bowel wall and has a large central area of low density consistent with necrosis or ulceration.
Question: What is the most likely diagnosis?
(A) GIST (Gastrointestinal Stromal Tumour) (B) Adenocarcinoma (C) Lymphoma (D) Carcinoid (E) Crohn’s Disease
Correct Answer: (A) GIST (Gastrointestinal Stromal Tumour).
Explanation:
- Why (A) is correct: This is the classic appearance of a small bowel GIST. They are typically large, exophytic, hypervascular masses that are prone to central necrosis, ulceration, and haemorrhage (causing GI bleeding). The stomach and small bowel are the most common locations.
- Why (B) is wrong: Adenocarcinoma of the small bowel (rare) is an infiltrative, annular, “apple-core” lesion that causes obstruction. It does not grow as a large exophytic mass.
- Why (C) is wrong: Lymphoma is typically a hypovascular, infiltrative, bulky mass that causes aneurysmal dilatation, not an exophytic, necrotic mass.
- Why (D) is wrong: Carcinoid is a small primary tumour with a large mesenteric desmoplastic reaction; the primary itself is not a large exophytic mass.
- Why (E) is wrong: Crohn’s disease is an inflammatory process, not a tumour.
Key Points: GIST
- Pathology: Mesenchymal tumour from the interstitial cells of Cajal.
- Location: Stomach > Small Bowel > Colon.
- Imaging Hallmarks:
- Large, exophytic (outward) growth.
- Hypervascular (avidly enhances).
- Prone to central necrosis, ulceration, and bleeding.
Question 9: Crohn’s Disease (Barium)
Stem: A 25-year-old man undergoes a small bowel barium follow-through for chronic diarrhoea. The images of the terminal ileum show multiple, linear, deep ulcerations, a “cobblestone” mucosal pattern, and a segment of severe, fixed narrowing.
Question: The severe, fixed narrowing seen on a barium study, often >10 cm in length, is known as the:
(A) “Kantor String Sign” (B) “Apple Core Sign” (C) “Bird’s Beak Sign” (D) “Comb Sign” (E) “Pencil-in-Cup” Sign
Correct Answer: (A) “Kantor String Sign”.
Explanation:
- Why (A) is correct: The “Kantor string sign” is the classic barium finding for fibrostenotic (scarred) Crohn’s disease. It describes the thin, attenuated stream of barium passing through a long segment of severe, fixed, fibrotic narrowing (most common in the terminal ileum).
- Why (B) is wrong: The “apple core sign” is a short, shouldered, annular stricture, classic for colorectal carcinoma.
- Why (C) is wrong: The “bird’s beak sign” is the smooth, tapered narrowing of the oesophagus in achalasia.
- Why (D) is wrong: The “comb sign” is a CT sign of active inflammation (engorged vasa recta).
- Why (E) is wrong: The “pencil-in-cup” sign is a deformity of the joints in psoriatic arthritis.
Key Points: Crohn’s Disease (Barium Findings)
- Aphthous Ulcers: Early sign (small ulcers with a red halo).
- “Cobblestone” Appearance: Intersecting linear and transverse ulcers.
- “Rose Thorn” Ulcers: Deep, linear, penetrating ulcers.
- “String Sign”: A long, fixed, narrow segment of fibrostenotic disease.
- Asymmetric involvement and skip lesions (key differentiators from UC).
Question 10: Peutz-Jeghers Syndrome
Stem: A 16-year-old boy presents to the ED with a small bowel intussusception. On physical exam, he is noted to have dark, freckle-like melanotic macules on his lips, oral mucosa, and fingertips.
Question: This combination of mucocutaneous pigmentation and intussusception is most suggestive of:
(A) Peutz-Jeghers Syndrome (B) Gardner Syndrome (C) Turcot Syndrome (D) Crohn’s Disease (E) Coeliac Disease
Correct Answer: (A) Peutz-Jeghers Syndrome.
Explanation:
- Why (A) is correct: This is the classic presentation. Peutz-Jeghers is an autosomal dominant syndrome defined by: 1) Mucocutaneous pigmentation (melanotic macules), and 2) Multiple hamartomatous polyps throughout the GI tract, especially the small bowel. These hamartomas act as lead points for recurrent intussusception.
- Why (B) is wrong: Gardner syndrome (a variant of FAP) involves adenomatous polyps, osteomas of the skull, and epidermoid cysts, not pigmentation.
- Why (C) is wrong: Turcot syndrome (a variant of FAP/Lynch) involves adenomatous polyps and brain tumours (medulloblastoma/glioblastoma).
- Why (D) & (E) are wrong: These are inflammatory/autoimmune conditions, not polyposis syndromes.
Key Points: Peutz-Jeghers Syndrome
- Inheritance: Autosomal Dominant.
- Triad:
- Mucocutaneous Pigmentation (lips, mouth, hands).
- Hamartomatous Polyps (especially small bowel).
- Increased risk of GI and non-GI (e.g., breast, pancreas) cancers.
- Complication: Hamartomatous polyps act as lead points for intussusception.
Question 11: Meckel’s Diverticulum
Stem: A 15-year-old boy presents with painless, severe rectal bleeding. A Technetium-99m pertechnetate scan (a “Meckel’s scan”) is performed, which shows a focal area of abnormal tracer uptake in the right lower quadrant, separate from the stomach.
Question: This test is positive because the abnormal tracer is taken up by which of the following?
(A) Ectopic Gastric Mucosa (B) Ectopic Pancreatic Tissue (C) Actively Bleeding Vessels (D) An Inflamed Diverticulum (E) A Carcinoid Tumour
Correct Answer: (A) Ectopic Gastric Mucosa.
Explanation:
- Why (A) is correct: A Meckel’s scan works by detecting ectopic gastric mucosa. The pertechnetate tracer is taken up and secreted by gastric mucosal cells. A Meckel’s diverticulum is the most common GI congenital anomaly, and 50% of symptomatic ones contain ectopic tissue, most commonly gastric. This gastric tissue secretes acid, causing ulceration and painless bleeding.
- Why (B) is wrong: Ectopic pancreatic tissue is the second most common type, but it does not take up pertechnetate.
- Why (C) is wrong: This is not a tagged-RBC (bleeding) scan; it is a scan for a specific cell type.
- Why (D) is wrong: This is not a WBC (inflammation) scan.
- Why (E) is wrong: A carcinoid tumour would be seen on an Octreotide (somatostatin receptor) scan, not a Meckel’s scan.
Key Points: Meckel’s Diverticulum
- “Rule of 2’s”: 2% of population, 2 feet from ileocaecal valve, 2 inches long, 2 types of ectopic tissue (gastric, pancreatic), symptomatic in 2% (usually by age 2).
- Definition: A true diverticulum (all 3 layers) from a persistent vitelline duct.
- Complications: 1. Bleeding (painless, from ectopic gastric mucosa), 2. Diverticulitis (mimics appendicitis), 3. Obstruction (from volvulus or intussusception).
Question 12: Small Bowel Lymphoma
Stem: A 70-year-old man with a history of untreated coeliac disease presents with weight loss, abdominal pain, and anaemia. A CT scan reveals a segment of the jejunum with massive, bulky, circumferential wall thickening. Despite a wall thickness of 5 cm, the lumen in this segment is widened and patent (aneurysmal dilatation).
Question: This combination of massive thickening with aneurysmal dilatation is most suggestive of:
(A) Lymphoma (B) Adenocarcinoma (C) GIST (D) Crohn’s Disease (E) Metastasis
Correct Answer: (A) Lymphoma.
Explanation:
- Why (A) is correct: This is a classic, though uncommon, sign. Lymphoma infiltrates the bowel wall and destroys the autonomic nerve plexus, leading to a flaccid, non-peristaltic segment. This results in aneurysmal dilatation of the lumen, despite the massive, bulky wall thickening. The history of coeliac disease is a major risk factor for small bowel lymphoma (EATL).
- Why (B) is wrong: Adenocarcinoma is fibrotic and causes stenosis and obstruction (an “apple-core” lesion).
- Why (C) is wrong: A GIST is an exophytic, focal mass, not a circumferential, infiltrative process.
- Why (D) is wrong: Crohn’s disease causes stenosis (fibrotic or inflammatory), not aneurysmal dilatation.
- Why (E) is wrong: Metastases are typically smaller, multiple nodules, though some (like melanoma) can be bulky. Lymphoma is the best fit for this specific appearance.
Key Points: Small Bowel Lymphoma
- Risk Factor: Coeliac disease (EATL – Enteropathy-Associated T-cell Lymphoma).
- Imaging:
- Bulky, homogeneous, hypovascular soft-tissue thickening.
- Aneurysmal dilatation of the involved segment (a key sign).
- Can also be a focal mass or infiltrative lesion.
- Associated bulky lymphadenopathy is common.
Question 13: Small Bowel Ischaemia (Venous)
Stem: A 45-year-old woman with a known pro-thrombotic disorder presents with subacute, cramping abdominal pain. A contrast-enhanced CT shows a filling defect (thrombus) in the superior mesenteric vein (SMV). The small bowel wall itself appears markedly thickened, oedematous (target sign), and shows some faint enhancement, but there is no pneumatosis.
Question: This presentation is most consistent with:
(A) Mesenteric ischaemia due to venous thrombosis. (B) Mesenteric ischaemia due to arterial embolus. (C) Crohn’s disease. (D) Intramural haematoma. (E) Septic emboli.
Correct Answer: (A) Mesenteric ischaemia due to venous thrombosis.
Explanation:
- Why (A) is correct: This is the classic picture of venous ischaemia. The thrombus is in the SMV (the vein). This causes a “back-pressure” on the bowel, leading to massive submucosal oedema and wall thickening. Because arterial inflow is initially preserved, the wall will still enhance (unlike arterial ischaemia).
- Why (B) is wrong: Arterial embolus would show a lack of enhancement, a thinner (paper-thin) bowel wall in the late stages, and a filling defect in the SMA (artery).
- Why (C) is wrong: Crohn’s disease causes hyperenhancement (comb sign), but not a large thrombus in the SMV.
- Why (D) is wrong: An intramural haematoma (e.g., from anticoagulation) would be hyperdense (blood) on non-contrast CT.
- Why (E) is wrong: Septic emboli cause focal, wedge-shaped infarcts or abscesses, not diffuse venous thrombosis.
Key Points: Venous vs. Arterial Ischaemia
- Arterial Ischaemia (Embolus/Thrombosis):
- Cause: SMA embolus (AFib) or thrombosis (atherosclerosis).
- CT: Lack of enhancement, “paper-thin” wall, pneumatosis, portal venous gas.
- Venous Ischaemia (Thrombosis):
- Cause: Hypercoagulable state, portal hypertension, pancreatitis.
- CT: Thrombus in SMV/portal vein, marked bowel wall thickening (oedema/haemorrhage), preserved (but delayed) enhancement.
Question 14: Whipple’s Disease
Stem: A 50-year-old man presents with a history of weight loss, migratory polyarthralgia, and chronic diarrhoea. A CT enterogram demonstrates diffuse, massive, nodular thickening of the small bowel folds, most prominent in the duodenum and proximal jejunum. There are also several large, low-density (fatty) retroperitoneal lymph nodes.
Question: This constellation of findings is most suggestive of:
(A) Whipple’s Disease (B) Coeliac Disease (C) Crohn’s Disease (D) Lymphoma (E) Metastatic Disease
Correct Answer: (A) Whipple’s Disease.
Explanation:
- Why (A) is correct: Whipple’s disease is a rare, systemic infection (Tropheryma whipplei). The classic GI manifestation is massively thickened, nodular folds, predominantly in the proximal small bowel, from infiltration of the lamina propria with macrophages. The presence of low-density (fat-containing) lymphadenopathy is also a highly specific sign.
- Why (B) is wrong: Coeliac disease causes atrophy of the proximal folds.
- Why (C) is wrong: Crohn’s disease is an ulcerative process, typically in the distal ileum.
- Why (D) is wrong: Lymphoma causes bulky thickening but does not typically have fat-containing nodes.
- Why (E) is wrong: Metastases are typically discrete nodules.
Key Points: Whipple’s Disease
- Definition: A rare, chronic, systemic infection (Tropheryma whipplei).
- Clinical: Malabsorption, weight loss, diarrhoea, arthralgia, neurological symptoms.
- Imaging:
- Massive, nodular fold thickening (a “pseudo-tumour” appearance), worst in the duodenum and jejunum.
- Low-density, fatty lymphadenopathy (retroperitoneal, mesenteric).
Question 15: Small Bowel Adhesions
Stem: A 60-year-old man presents with acute, colicky abdominal pain and vomiting. He has a surgical history of an appendicectomy 20 years ago. A CT scan confirms a high-grade small bowel obstruction. The transition point is in the right iliac fossa, where there is an abrupt change in calibre, but there is no visible mass, hernia, or inflammatory wall thickening.
Question: What is the most likely cause of this obstruction?
(A) Adhesions (B) Carcinoid Tumour (C) Crohn’s Disease (D) Obturator Hernia (E) Gallstone Ileus
Correct Answer: (A) Adhesions.
Explanation:
- Why (A) is correct: Adhesions (fibrous bands of scar tissue from prior surgery) are the most common cause of small bowel obstruction (60-70%). They are a diagnosis of exclusion on CT. The classic finding is an abrupt transition point without any other identifiable cause (no mass, no hernia, no inflammation). The history of prior surgery is the key risk factor.
- Why (B) is wrong: A carcinoid tumour would be visible as a desmoplastic mesenteric mass.
- Why (C) is wrong: Crohn’s disease would show marked wall thickening and enhancement.
- Why (D) is wrong: An obturator hernia would be visible as a herniated loop of bowel.
- Why (E) is wrong: A gallstone would be visible in the lumen.
Key Points: Adhesive SBO
- Definition: SBO caused by fibrous bands of scar tissue.
- Risk Factor: Prior abdominal surgery (e.g., appendicectomy, gynaecological surgery).
- CT Diagnosis: This is a diagnosis of exclusion. The CT will show:
- Dilated proximal bowel.
- Collapsed distal bowel.
- A clear transition point.
- The ABSENCE of any other cause (e.g., hernia, tumour, inflammation) at the transition point.
