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RADIOLOGY UNIVERSITY EXAM - GIT SECTION

Model Answers (30 Marks Each)

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QUESTION 1: Radio Imaging in Diffuse Liver Lesions (in brief)

Introduction

Classification of Diffuse Liver Lesions

1. Fatty liver (Hepatic steatosis)
2. Cirrhosis
3. Hepatitis (acute and chronic)
4. Diffuse hepatic malignancy (HCC, metastasis, lymphoma)
5. Storage disorders (Gaucher, Wilson's, hemochromatosis, amyloidosis)
6. Congestion (Budd-Chiari, congestive heart failure)

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Imaging Modalities

1. Ultrasound (USG)

• First-line modality - cheap, widely available, no radiation
• Fatty liver: Increased echogenicity ("bright liver"), hepatomegaly, posterior acoustic attenuation, poor visualization of diaphragm and portal vein walls
• Cirrhosis: Coarse heterogeneous echotexture, nodular surface, caudate lobe hypertrophy, small right lobe, splenomegaly, ascites, portal hypertension (dilated portal vein >13 mm, reversal of flow)
• Acute hepatitis: Hepatomegaly, decreased echogenicity ("starry sky" pattern - portal triad echogenicity stands out)
• Congestion: Dilated hepatic veins, dilated IVC, loss of normal hepatic vein pulsatility

2. CT Scan

• Fatty liver: Liver attenuation <40 HU (non-contrast), liver:spleen ratio <0.8. Focal fat sparing appears as relatively dense areas
• Cirrhosis: Heterogeneous enhancement, regenerative nodules (isodense), dysplastic nodules (hyperdense), HCC (arterial enhancement, portal washout - "washout sign")
• Hemochromatosis: Diffuse increased attenuation (>70 HU) on non-contrast CT
• Budd-Chiari: Peripheral hypoperfusion, caudate lobe enhancement (separate drainage), "flip-flop" pattern
• Diffuse HCC: Multiple hypervascular masses; infiltrative pattern may show portal vein thrombosis

3. MRI

• Most sensitive modality for diffuse liver diseases
• Fatty liver: Signal drop on opposed-phase (out-of-phase) T1 GRE images (chemical shift imaging - India ink artifact at fat-water interfaces)
• Hemochromatosis: Diffuse signal loss on T2 and T2* sequences ("black liver") due to iron deposition
• Fibrosis/Cirrhosis: T1 hypointense fibrous bands, T2 hyperintense inflammation
• Amyloidosis: Heterogeneous T1/T2 signal, reduced ADC on DWI
• Gadolinium-enhanced MRI: Best for characterizing vascular lesions (CEUS equivalent)
• Hepatobiliary contrast agents (Primovist/Eovist): Gadoxetate disodium - hepatocyte-specific agent; hepatic function assessment

4. Nuclear Medicine

• Tc-99m sulfur colloid scintigraphy: Cirrhosis shows decreased hepatic uptake, increased splenic and bone marrow uptake (colloid shift)
• FDG-PET: Increased uptake in malignant lesions, lymphoma

5. Elastography (Transient Elastography / MR Elastography)

• Measures liver stiffness (in kPa)
• FibroScan (vibration-controlled transient elastography) - gold standard non-invasive fibrosis assessment
• Grading: F0 (<5 kPa), F1 (5-7), F2 (7-9.5), F3 (9.5-12.5), F4 cirrhosis (>12.5 kPa)

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Summary Table

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QUESTION 2A: Enumerate Gall Bladder Pathology - Discuss One in Detail

QUESTION 2B: Sigmoid Volvulus

PART A - Gallbladder Pathologies

Enumeration of GB Pathologies:

1. Cholelithiasis (gallstones)
2. Acute cholecystitis
3. Chronic cholecystitis
4. Acalculous cholecystitis
5. Gallbladder polyps
6. Gallbladder carcinoma
7. Porcelain gallbladder
8. Empyema of gallbladder
9. Gallbladder hydrops (mucocele)
10. Gangrenous cholecystitis
11. Pericholecystic abscess
12. Mirizzi syndrome
13. Adenomyomatosis

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Detailed Discussion: ACUTE CHOLECYSTITIS

Definition

Pathophysiology

Ultrasound Findings (Investigation of Choice - 95% accuracy)

1. Gallstones - echogenic foci with acoustic shadowing
2. GB wall thickening - >3 mm (normal <3 mm)
3. Pericholecystic fluid - hypoechoic collection around GB
4. Murphy's sign on USG - maximum tenderness with probe directly over visualized GB (positive in 85%)
5. Distended GB - >5 cm transverse, >10 cm longitudinal
6. GB wall edema - striated/double-wall appearance
7. Echogenic bile (sludge)

CT Findings

• GB wall thickening with enhancement
• Pericholecystic fat stranding
• Pericholecystic fluid
• Stones (if calcified - seen in 15% on plain CT)
• Gas in GB wall = emphysematous cholecystitis (diabetics)

HIDA Scan (Hepatobiliary Iminodiacetic Acid)

• Non-visualization of GB = cystic duct obstruction = acute cholecystitis
• Sensitivity 95%, Specificity 90%
• Rim sign = pericholecystic hepatic activity = gangrenous cholecystitis

Complications on Imaging

• Gangrenous cholecystitis: Irregular/asymmetric wall, intraluminal membranes, absent Murphy's sign
• Perforation: Pericholecystic abscess, loss of wall continuity
• Emphysematous: Gas in GB wall/lumen (diabetics)
• Mirizzi syndrome: Large stone compresses CBD

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PART B - SIGMOID VOLVULUS

Definition

Risk Factors

• Elderly, institutionalized patients
• High-fiber diet
• Chronic constipation
• Chagas disease
• Long, redundant sigmoid colon ("megasigmoid")

Plain X-Ray Findings (Most Important - Diagnostic in 60-70%)

1. "Coffee bean" or "bent inner tube" sign - large, inverted U-shaped gas-filled loop in the right upper abdomen pointing to right hypochondrium
2. Loss of haustral pattern in the dilated loop
3. Two vertical white lines (convergence of walls) running to left iliac fossa = "white line sign" or "confluence of walls"
4. Disproportionately dilated colon (>6 cm)
5. Absent rectal gas

Barium Enema Findings

• "Ace of spades" or "bird's beak" deformity at the site of twist in the rectosigmoid junction
• Smooth, gradual tapering at point of obstruction

CT Findings

• "Whirl sign" - mesenteric fat and bowel twisting around mesentery
• "Coffee bean" sign - dilated sigmoid loop
• "Bird's beak" sign - tapering of colon at twist point
• Closed-loop obstruction with two transition points
• Signs of ischemia: Wall thickening, free fluid, pneumatosis coli, pneumoperitoneum in late stages

Management

• Flexible sigmoidoscopy - deflation tube placement (non-operative detorsion)
• If gangrenous/failed detorsion: Hartmann's procedure

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QUESTION 3: Clinical Application of Elastography

Introduction

Principle

• Harder tissue = Less strain = Higher E value
• Fibrotic liver, malignant nodes, carcinoma - all stiffer than normal tissue

Types of Elastography

1. Strain Elastography (SE)

• Manual compression by probe
• Measures relative stiffness (qualitative/semi-quantitative)
• Color map: Blue = hard, Red = soft (or vice versa)
• Clinical use: Breast lesions, thyroid nodules, lymph nodes

2. Shear Wave Elastography (SWE)

• ARFI (Acoustic Radiation Force Impulse)
• Transient elastography (FibroScan)
• Point SWE, 2D-SWE
• Provides quantitative stiffness values (kPa or m/s)

3. MR Elastography (MRE)

• Most accurate, large ROI
• Mechanical vibration + phase-contrast MRI
• Gold standard for liver fibrosis staging

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Clinical Applications

1. LIVER (Most Important)

• Liver fibrosis staging - non-invasive alternative to biopsy
• FibroScan (Transient Elastography): Measures stiffness in kPa
  • F0-F1: <7 kPa (no/mild fibrosis)
  • F2: 7-9.5 kPa (moderate)
  • F3: 9.5-12.5 kPa (severe)
  • F4 (cirrhosis): >12.5 kPa
• MRE: Better for obese patients (where FibroScan fails), more accurate
• Guides antiviral therapy decisions in Hepatitis B, C

2. BREAST

• Differentiate benign vs. malignant lesions
• Malignant lesions: Stiffer, size on elastogram > size on B-mode ("larger on elastogram")
• Benign fibroadenoma: Soft, red on elastogram
• Strain ratio >3 = malignant (sensitivity 87%, specificity 90%)
• Reduces unnecessary biopsies of BIRADS 3 lesions

3. THYROID

• Malignant nodules: Stiffer (blue on elastogram)
• Benign colloid nodules: Soft
• Elasticity score 4-5 = malignant; guides FNA
• Hashimoto's thyroiditis: Diffuse stiffness

4. LYMPH NODES

• Metastatic nodes: Hard, heterogeneous
• Reactive nodes: Soft, compressible
• Useful in head-neck cancer staging, axillary staging in breast cancer

5. PROSTATE

• Cancer foci are stiffer
• Guides targeted biopsy (combines with transrectal USG)
• Elastography-guided biopsy improves cancer detection rate

6. TESTIS

• Focal hard areas suggestive of testicular carcinoma
• Differentiates intratesticular lesions

7. MUSCULOSKELETAL

• Tendon pathology: Tendinopathy shows softening of tendon tissue
• Muscle injuries: Stiffness mapping
• Plantar fasciitis assessment

8. KIDNEY

• Renal fibrosis assessment (CKD monitoring)
• Transplant kidney rejection evaluation (increased stiffness)

9. PANCREAS

• Chronic pancreatitis: Increased stiffness
• Pancreatic cancer: Very stiff (harder than pancreatitis)

10. CARDIOVASCULAR

• Arterial wall stiffness assessment
• Carotid plaque vulnerability

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Limitations

• Operator dependent (strain elastography)
• Obese patients - increased failure rate
• Ascites - underestimates liver stiffness
• Right heart failure, post-meal - overestimates liver stiffness
• Learning curve required

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QUESTION 4/8: Radiological Features of Ulcerative Colitis and Crohn's Disease

Introduction

ULCERATIVE COLITIS (UC)

Distribution

• Starts in rectum, extends proximally in a continuous, uninterrupted pattern
• Always involves rectum (except after topical therapy)
• Affects only mucosa and submucosa (superficial)

Plain Abdominal X-Ray

• Toxic megacolon: Colonic dilatation >6 cm (transverse colon), loss of haustration, thumbprinting (mucosal edema)
• Loss of haustral folds ("lead pipe" appearance in chronic disease)
• Granular mucosal pattern

Barium Enema (Double Contrast - Now largely replaced by colonoscopy/MRI)

• Active disease: Granular mucosa (fine stippling), ulceration (collar-stud ulcers), loss of haustration
• Chronic disease: "Lead pipe" colon - featureless, shortened, rigid colon with no haustral pattern
• Pseudopolyps: Islands of residual mucosa between ulcers
• Backwash ileitis: Terminal ileum involvement in pancolitis (dilated, patulous ileocecal valve)
• Rectal valve loss: Loss of Houston's valves

CT/CT Colonography

• Symmetric, circumferential wall thickening
• Mural stratification (target pattern) in acute phase
• Pericolonic fat stranding
• Continuous involvement from rectum proximally

MRI (Gold Standard for Perianal Disease)

• Wall thickening, mucosal enhancement
• Used for fistula/abscess assessment (though more typical of Crohn's)

Complications on Imaging

• Toxic megacolon: Most feared; dilatation >6 cm + systemic toxicity
• Carcinoma: Stricture with irregular mucosa (malignant stricture vs. benign)
• Primary Sclerosing Cholangitis (PSC): Beaded appearance of biliary tree

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CROHN'S DISEASE

Distribution

• "Skip lesions" - non-contiguous, any part of GI tract (mouth to anus)
• Terminal ileum most commonly affected (80%)
• Transmural inflammation (all layers of bowel wall)
• "String sign of Kantor" on barium

Plain X-Ray

• Subacute/acute obstruction due to strictures
• Bowel wall thickening with separation of loops
• Free air if perforated

Barium Meal/Follow-Through

• Aphthous ulcers: Earliest lesion - small punctate ulcers with surrounding edema ("target" appearance)
• Cobblestone pattern: Deep ulcers + mucosal edema = cobblestone
• String sign of Kantor: Severely narrowed terminal ileum (fibrotic stricture)
• Skip lesions: Normal bowel between diseased segments
• Fistulae: Entero-enteric, enterovesical, enterocutaneous
• "Rose thorn" ulcers: Deep linear fissuring ulcers

CT Enterography (Most Important Investigation Today)

• Wall thickening (>3 mm) - asymmetric, eccentric
• Mural stratification (target sign) in active disease
• Fat wrapping/creeping fat - mesenteric fat enveloping bowel (highly specific for Crohn's)
• "Comb sign" - increased vascularity of mesentery (engorged vasa recta - like teeth of a comb)
• Strictures with prestenotic dilatation
• Abscesses and fistulae
• Fibrofatty proliferation of mesentery

MR Enterography (MRE)

• No radiation (preferred in young patients)
• Best for bowel wall characterization and perianal disease
• T2 edema = active inflammation; T1 post-contrast = active vs. fibrotic stricture
• DWI (Diffusion-weighted imaging): High signal in active disease

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COMPARISON TABLE: UC vs. Crohn's Disease

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QUESTION 5: Types of Esophageal Fistula with Radio Imaging Findings

Classification of Esophageal Fistulas

A. Congenital (Tracheoesophageal Fistula - TEF)

• Type A: Pure esophageal atresia (EA), no TEF - blind pouches at both ends
• Type B: EA + proximal TEF (rare)
• Type C: EA + distal TEF - Most Common (85%) - upper pouch blind, lower esophagus communicates with trachea
• Type D: EA + both proximal and distal TEF
• Type E (H-type): TEF without EA - "H-fistula" (4-5%)

• Plain X-ray: NG tube curling in upper pouch (EA), gas in stomach/bowel (indicates distal fistula), gasless abdomen (pure EA)
• Water-soluble contrast swallow: Demonstrates fistula communication
• CT: Best shows anatomy, fistula tract

B. Acquired Esophageal Fistulas

1. Esophagorespiratory fistula (esophago-tracheal or esophagobronchial)
2. Esophagoaortic fistula
3. Esophagopericardial fistula
4. Cervical/thoracic cutaneous fistula

Causes of Acquired Fistulas

• Malignancy (most common - esophageal or bronchial carcinoma)
• Post-radiation therapy
• Instrumentation/Trauma (post-endoscopy, post-surgery)
• Foreign body erosion
• Mediastinitis/lymph node perforation (TB, fungal)
• Boerhaave syndrome sequela

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Esophagorespiratory Fistula (Most Commonly Tested)

Presentation

• Coughing on swallowing (Ono's sign)
• Recurrent aspiration pneumonia
• "Aspiration pattern" lung changes

Imaging Findings

Plain X-Ray

• Aspiration pneumonia (right lower lobe most common - due to right mainstem bronchus anatomy)
• Air in mediastinum (if esophageal perforation preceded fistula)

Barium/Water-Soluble Contrast Swallow

• Investigation of choice
• Direct demonstration of contrast passing from esophagus into trachea/bronchus
• Use water-soluble contrast (Gastrografin) first (avoid barium aspiration)
• If negative with Gastrografin (more viscous), use thin barium in Trendelenburg position
• H-type fistula: Best seen in lateral projection with patient prone

CT Chest

• Demonstrates fistula tract, associated mediastinal mass/lymphadenopathy
• Air in esophageal wall
• Aspiration changes in lungs

Bronchoscopy / Esophagoscopy

• Direct visualization, biopsy for malignancy

Radionuclide Study

• Salivagram (Tc-99m in saliva) - demonstrates aspiration

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QUESTION 6: Anatomy of Biliary Tree + Radiological Evaluation of Obstructive Jaundice + Differential Diagnosis

PART A: Anatomy of Biliary Tree

Intrahepatic Ducts

• Right hepatic duct: Drains right lobe (segments V-VIII); formed by right anterior and right posterior sectoral ducts
• Left hepatic duct: Longer duct, drains left lobe (segments II-IV); runs in umbilical fissure
• Common hepatic duct (CHD): Forms at porta hepatis by union of right + left hepatic ducts; length 3 cm

Extrahepatic Ducts

• Cystic duct: From gallbladder neck; joins CHD to form CBD; contains spiral valves of Heister
• Common Bile Duct (CBD): Length 8-10 cm, diameter normally <8 mm (>10 mm = dilated); 4 parts:
  1. Supraduodenal
  2. Retroduodenal
  3. Pancreatic
  4. Intraduodenal (ampullary)
• Ampulla of Vater: Junction of CBD + pancreatic duct (Wirsung); enters into 2nd part of duodenum at major duodenal papilla (sphincter of Oddi)

Normal Diameters

• Intrahepatic ducts: <2 mm (not visible on USG)
• CHD: <7 mm
• CBD: <8 mm (<10 mm post-cholecystectomy)
• Pancreatic duct: <3 mm

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PART B: Radiological Evaluation of Obstructive Jaundice (40-year-old male)

Step 1: Ultrasound (USG) - First Line

• Dilated intrahepatic bile ducts (IHBDs): Parallel channel sign ("double barrel shotgun sign") - dilated duct parallel to portal vein
• Dilated CBD: >8 mm
• Level of obstruction:
  • If GB dilated + CBD dilated = obstruction below cystic duct confluence (Courvoisier's sign on USG)
  • If GB not dilated + CBD dilated = malignant stricture at/above cystic duct level
• Cause identification: Stones (echogenic with shadowing), mass (hypoechoic), stricture
• Courvoisier's Law: Dilated non-tender GB with jaundice = unlikely gallstones (distended GB = malignant obstruction of CBD)

Step 2: MRCP (Magnetic Resonance Cholangiopancreatography)

• Investigation of choice for biliary tree anatomy
• Non-invasive, no radiation, no contrast required
• T2-weighted sequences: Bile appears bright white
• "Meniscus sign": Stone appears as dark filling defect in bright bile
• Identifies level and cause of obstruction with 95% accuracy
• Shows dilated ducts, stricture morphology, mass lesions

Step 3: CT Scan (CECT Abdomen)

• Better for malignant causes, local staging, vascular involvement
• "Double duct sign": Simultaneous dilation of CBD + pancreatic duct = periampullary malignancy (head of pancreas carcinoma)
• Identifies pancreatic mass, liver metastases, lymphadenopathy
• CT angiography for vascular involvement (portal vein, SMA - resectability assessment)

Step 4: ERCP (Endoscopic Retrograde Cholangiopancreatography)

• Diagnostic AND therapeutic (gold standard intervention)
• Can perform: Stone extraction, stenting, brush cytology/biopsy
• Complication rate 5-10% (pancreatitis, cholangitis, perforation)

Step 5: PTC (Percutaneous Transhepatic Cholangiography)

• When ERCP fails or not accessible (hilar obstruction, altered anatomy)
• Diagnostic + therapeutic (PTBD - Percutaneous Transhepatic Biliary Drainage)
• Contraindication: Coagulopathy, ascites

Step 6: EUS (Endoscopic Ultrasound)

• Best for ampullary lesions, distal CBD stones, pancreatic head masses
• Can guide FNA for tissue diagnosis

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PART C: Differential Diagnosis of Obstructive Jaundice in a 40-Year-Old Male

Intraluminal Causes

1. Choledocholithiasis (CBD stones) - Most common cause in adults
2. Blood clot (haemobilia)
3. Parasites (Ascaris, Clonorchis sinensis)

Wall Causes

1. Cholangiocarcinoma (Klatskin tumor - hilar; most common at bile duct in 40s-60s)
2. Choledochal cyst (Type I - most common)
3. Primary sclerosing cholangitis (PSC)
4. Post-inflammatory/ischemic stricture
5. Ampullary carcinoma

Extrinsic Compression

1. Carcinoma head of pancreas - Most common malignant cause overall
2. Lymphadenopathy (Mirizzi syndrome, porta hepatis nodes)
3. Chronic pancreatitis (inflammatory mass)
4. Gallbladder carcinoma
5. Hepatocellular carcinoma involving porta hepatis
6. Metastatic nodes

Benign vs. Malignant Obstruction (Imaging Clues)

• Benign: Abrupt transition, stone visible, history of gallstones, USS stones
• Malignant: Shouldering, irregular margins, "rat-tail" stricture on MRCP, double duct sign

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QUESTION 7: Diagnostic and Therapeutic Role of Radiology in Lower GI Bleeding (7-year-old / 60-year-old)

Introduction

Causes in a Child (7 years)

1. Meckel's diverticulum (Most important - ectopic gastric mucosa)
2. Juvenile polyps (most common overall cause of rectal bleeding in children)
3. Intussusception
4. Inflammatory bowel disease
5. Henoch-Schonlein purpura (HSP)
6. Rectal prolapse
7. Ano-rectal fissure

Causes in a 60-year-old Male

1. Diverticular disease (most common)
2. Angiodysplasia (arteriovenous malformation)
3. Colorectal carcinoma
4. Ischemic colitis
5. IBD (UC, Crohn's)
6. Internal hemorrhoids
7. Radiation proctitis

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DIAGNOSTIC ROLE OF RADIOLOGY

1. Technetium-99m Pertechnetate Scan (Meckel's Scan)

• Investigation of choice for Meckel's diverticulum in children
• Tc-99m pertechnetate is taken up by ectopic gastric mucosa
• Hot spot in right iliac fossa = Meckel's diverticulum
• Sensitivity 85%, Specificity 95% in children

2. Tc-99m Labeled Red Blood Cell (RBC) Scan

• Detects active bleeding at rates as low as 0.1-0.5 mL/min
• Sensitivity superior to angiography
• Localizes bleeding site (quadrant level)
• Not useful for intermittent bleeding

3. CT Angiography (CTA) - Most Important in Adults

• Detects bleeding at 0.3-0.5 mL/min
• Non-invasive, rapid
• Shows "blush" = contrast extravasation into bowel lumen
• Localizes bleeding to a segment
• Shows cause: Diverticulum, polyp, tumor, AVM

4. Conventional Catheter Angiography (DSA)

• Detects bleeding at 0.5-1 mL/min
• Gold standard for intervention
• Finds bleeding source + can treat

5. USG

• Intussusception: "Target sign"/"Pseudokidney sign" on ultrasound (most important in children)
• Donut sign on transverse section
• USG-guided hydrostatic/pneumatic reduction of intussusception (diagnostic + therapeutic)

6. Barium Enema

• Diagnoses intussusception, polyps, colonic lesions
• Hydrostatic reduction of intussusception (air/barium enema)

7. MRI Enterography

• IBD evaluation

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THERAPEUTIC ROLE OF RADIOLOGY (Interventional)

1. Transarterial Embolization (TAE)

• Most important therapeutic IR procedure
• Catheter angiography identifies bleeding vessel (e.g., right colic artery for cecal AVM)
• Superselective embolization with microcoils, gelfoam, PVA particles
• Success rate 70-90% in diverticular bleeding
• Risk: Bowel ischemia (hence "superselective" technique important)

2. Vasopressin Infusion

• Intra-arterial vasopressin (0.2 units/min)
• Causes vasoconstriction, controls bleeding temporarily
• Now largely replaced by embolization

3. USG-Guided Procedures

• Pneumatic/hydrostatic reduction of intussusception in children (80-90% success)
• Air enema under fluoroscopy: Contraindicated if perforation, peritonitis, or >48 hours

4. CT-Guided Drainage

• Drainage of pericolic abscess (Crohn's, diverticular)

5. Coiling of Pseudoaneurysms

• Splenic, renal, GDA pseudoaneurysms causing secondary LGIB

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QUESTION: Imaging Features of Acute and Chronic Pancreatitis

ACUTE PANCREATITIS

Causes

• Gallstones (40%), Alcohol (35%), Idiopathic (15%), ERCP, drugs, trauma, hypercalcemia, hypertriglyceridemia

Ultrasound

• Enlarged, hypoechoic pancreas
• Peripancreatic fluid
• Gallstones (identifies etiology)
• Dilated CBD
• Limited by overlying bowel gas

CT (Investigation of Choice for Staging)

• Normal pancreas = 0 points
• Intrinsic abnormality +/- peripancreatic fat changes = 2 points
• Pancreatic/peripancreatic fluid collection or fat necrosis = 4 points
• Necrosis: None = 0, ≤30% = 2, >30% = 4
• Extra-pancreatic complications (pleural effusion, ascites, vascular complications) = +2

• Pancreatic enlargement, indistinct margins
• Peripancreatic fat stranding
• Peripancreatic fluid collections
• Necrosis: Non-enhancing areas on CECT (>30% = severe, high mortality)
• "Halo sign" - rim of fluid around pancreas
• Pleural effusion (left > right)

Complications (CT)

• Acute Peripancreatic Fluid Collection (APFC): No encapsulation, <4 weeks
• Pseudocyst: Encapsulated fluid collection, >4 weeks, no solid component
• Acute Necrotic Collection (ANC): Heterogeneous, contains necrotic material, <4 weeks
• Walled-Off Necrosis (WON): Encapsulated necrosis, >4 weeks - "heterogeneous collection with thick wall"
• Splenic vein thrombosis, pseudoaneurysm (splenic artery)

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CHRONIC PANCREATITIS

Causes

• Alcohol (most common), tropical/hereditary pancreatitis, hyperparathyroidism, CF

Plain X-Ray

• Pancreatic calcifications ("chain of lakes" pattern) - pathognomonic
• Curvilinear calcifications along pancreatic axis

Ultrasound

• Heterogeneous, echogenic pancreas (fibrosis)
• Dilated, irregular pancreatic duct (>3 mm)
• Ductal calculi (echogenic foci with shadowing)
• Atrophy
• Pseudocysts

CT

• Pancreatic atrophy
• Dilated, irregular ("chain of lakes") pancreatic duct
• Pancreatic calcifications
• Ductal stones
• Pseudocysts
• Splenic vein thrombosis

MRCP / MRI

• "Chain of lakes" duct - alternating dilations and strictures
• Side branch ectasia
• Ductal stones as filling defects (dark in bright bile)
• Pancreatic parenchymal loss

EUS

• Best for early chronic pancreatitis (Rosemont criteria)

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QUESTION: ERCP vs MRCP

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QUESTION: Barium Meal Findings in 5 Common Small Intestinal Pathologies

1. Tuberculosis (TB) of Small Bowel

• Ileocecal region most commonly affected
• Stierlin's sign: Rapid emptying (irritability) of cecum + terminal ileum with normal surrounding bowel = "string sign" of terminal ileum
• Conical, shrunken, fibrotic cecum (gaping ileocecal valve)
• Transverse ulcers (perpendicular to long axis)
• Strictures - short, multiple, "hour-glass" deformity
• "Fleischner sign": Patulous (wide open) ileocecal valve in early TB

2. Crohn's Disease (Terminal Ileum)

• "String sign of Kantor": Severely narrowed terminal ileum due to fibrotic stricture
• Cobblestone pattern: Transverse + longitudinal ulcers between edematous islands
• Rose thorn ulcers: Deep fissuring ulcers
• Skip lesions
• Fistulae: "Pipestem" fistula tract

3. Malabsorption Syndrome (Celiac Disease)

• Dilution pattern: Barium diluted and scattered due to excess fluid
• Moulage sign: Featureless, tube-like jejunum with effaced folds (wax cast appearance)
• Jejunization of ileum: Ileal folds become prominent (compensatory)
• Jejunal fold reversal (Reversal of folds): Jejunum has <3 folds/inch, ileum has >5 folds/inch - reversal of normal pattern
• Flocculation and segmentation of barium

4. Small Bowel Obstruction (Mechanical)

• Multiple dilated small bowel loops (>3 cm)
• "Herringbone pattern" or "stack of coins" - valvulae conniventes (plicae circulares) visible in dilated jejunum
• Fluid levels on erect film
• Transition point: Caliber change from dilated to collapsed bowel
• Water-soluble contrast follow-through: Gastrografin challenge

5. Carcinoid Tumor

• Usually submucosal, ileum most common
• Desmoplastic reaction: Mesenteric tethering, kinking, angulation of bowel loops
• Fixed, angulated loops
• "Sunburst" pattern of mesenteric fibrosis on CT
• Primary lesion may be tiny, indentation/filling defect

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QUESTION: Role of Radio-Imaging in Interventional Radiology in HCC Management

Staging (BCLC - Barcelona Clinic Liver Cancer)

Loco-Regional Therapies (Imaging-Guided)

1. TACE (Trans-Arterial Chemo-Embolization)

• Most widely used treatment for intermediate-stage HCC
• DSA: HCC arterial supply identified (hepatic angiography), hypervascular tumor blush
• Lipiodol (iodized oil) + chemotherapy (doxorubicin/cisplatin) injected, then gelfoam embolization
• Post-TACE: Dense lipiodol uptake on CT = treatment response ("lipiodol retention")
• mRECIST criteria: Viable tumor = arterial enhancement; necrosis = no enhancement

2. TARE/SIRT (Trans-Arterial Radio-Embolization / Selective Internal Radiation Therapy)

• Yttrium-90 microspheres injected intra-arterially
• Pre-procedure: Tc-99m MAA scan to assess lung shunting fraction (<20% required)
• Post-procedure: Bremsstrahlung scan or PET Y-90 to confirm distribution

3. RFA (Radiofrequency Ablation)

• CT/USG-guided: Electrode placed in tumor, heat destroys cancer cells
• Best for lesions <3 cm
• Image guidance: Real-time USG or CT fluoroscopy
• Post-ablation zone = hyperechoic on USG, low density on CT

4. MWA (Microwave Ablation)

• Faster, larger ablation zones than RFA
• CT/USG guided

5. Cryoablation

• Ice ball formation (T2 MRI: dark ice ball in bright background)

6. PEI (Percutaneous Ethanol Injection)

• USG-guided; ethanol injected into tumor
• Now largely replaced by RFA

7. HIFU (High-Intensity Focused Ultrasound)

• Non-invasive thermal ablation

8. Portal Vein Embolization (PVE)

• Pre-operative: Embolize portal vein to affected lobe
• Induces hypertrophy of future liver remnant (FLR)
• CT volumetry: Measures FLR volume before surgery

Assessment of Treatment Response

• mRECIST criteria: Only enhancing (viable) tumor measured
• EASL criteria: Necrosis = no arterial enhancement
• Follow-up CT at 4-6 weeks post-TACE

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QUESTION: Enumerate Congenital Malrotation of Gut - Embryological Basis

Normal Gut Rotation

• Midgut undergoes 3 rotational steps (total 270° counterclockwise) during weeks 6-12 of embryological development
• Primary intestinal loop returns to abdomen and rotates around superior mesenteric artery (SMA) axis

Types of Congenital Malrotation

1. Non-rotation (Failure of Rotation)

• Gut returns without rotation
• Small bowel on right, colon on left
• SMA and SMV positions reversed (SMV left of SMA)
• Volvulus risk present

2. Incomplete Rotation (Most Common - 1:500 births)

• 90° or 180° rotation only (not full 270°)
• Cecum in right upper quadrant or midline
• Duodenojejunal (DJ) flexure to the right of midline
• Ladd's bands: Peritoneal bands from abnormally positioned cecum crossing over duodenum → duodenal obstruction
• Narrow SMA pedicle → midgut volvulus

3. Reversed Rotation

• 90° clockwise rotation
• Transverse colon behind SMA
• Causes colon obstruction

4. Mesocolic Hernias

• Right-sided: Due to non-fixation of right mesentery
• Left-sided (Paraduodenal hernia): Due to abnormal rotation

5. Internal Hernias

• Due to abnormal fixation of mesentery

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Radiological Findings

Plain X-Ray

• "Double-bubble sign" (if duodenal obstruction by Ladd's bands)
• High obstruction pattern

Barium Meal / Follow-Through

• DJ flexure to the right of L1/L2 vertebral body = hallmark of malrotation
• Corkscrew pattern of duodenum/jejunum = volvulus
• Cecum in right upper quadrant or epigastrium

USG

• SMV to the left of SMA (reversal of normal relationship - SMA on left, SMV on right)
• Whirlpool sign of mesentery = midgut volvulus

CT

• Abnormal gut positioning
• Whirlpool sign: Mesenteric vessels twisting
• SMA-SMV inversion
• "Corkscrew" duodenum in volvulus

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Embryological Basis

Week 5-6: Physiological Herniation

• Rapid elongation of midgut → herniation into umbilical cord (primary umbilical herniation)
• Gut elongates as a U-loop around SMA axis

Week 6-10: 1st Rotation (90° CCW)

• Pre-arterial (small intestine) segment rotates to right
• Post-arterial (large intestine) segment to left

Week 10-12: Return to Abdomen (2nd Rotation - 180° CCW)

• Pre-arterial segment returns first, goes to right then to left (dorsal position)
• Post-arterial segment (cecum) returns, undergoes further rotation: Right → Descends to RIF
• Total rotation = 270° counterclockwise

Week 12 onwards: 3rd Stage - Fixation

• Mesentery of small bowel fixed from DJ flexure (left of L2) to ileocecal junction (RIF) - "broad base" prevents volvulus

In Malrotation:

• Incomplete rotation → narrow mesenteric pedicle (from abnormal DJ position to abnormal cecum position) → entire midgut hangs on a narrow pedicle → catastrophic midgut volvulus

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QUESTION: Imaging in Ischemic Bowel Disease

Causes

• Superior mesenteric artery (SMA) occlusion (thromboembolism) - acute
• Venous (SMV thrombosis)
• Non-occlusive mesenteric ischemia (NOMI) - low-flow states
• Strangulation, volvulus

Imaging

Plain X-Ray (Non-specific, Late Changes)

• "Thumbprinting" - rounded soft-tissue projections into lumen = submucosal hemorrhage/edema
• Paralytic ileus
• Pneumatosis intestinalis - gas in bowel wall = transmural infarction (ominous sign)
• Portal venous gas - gas outlining portal vein and liver (late, severe) = usually lethal
• Pneumoperitoneum - perforation

CT Angiography (Gold Standard)

• Non-enhancing bowel wall = infarction
• Bowel wall thickening or thinning
• Pneumatosis coli/intestinalis = intramural gas
• Portal venous gas = gas in portal vein branches (hepatic)
• Mesenteric fat stranding
• SMA filling defect (embolus/thrombosis)
• SMV thrombosis = hyperdense clot in SMV

MRI/MRA

• Non-occlusive ischemia assessment
• Portal vein thrombosis assessment

DSA (Conventional Angiography)

• Diagnostic and therapeutic (thrombolysis, papaverine infusion for NOMI)

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QUESTION: Imaging of Benign and Neoplastic Lesions of Stomach

BENIGN LESIONS

1. Peptic Ulcer (Gastric Ulcer)

• Barium meal: Niche (crater) projecting beyond lumen, Hampton's line, ring shadow of edema, folds radiating from ulcer
• CT: Focal wall thickening with ulcer crater
• Benign signs: Projects beyond lumen, smooth margins, radiating folds, Hampton's line, ulcer collar

2. Gastric Polyps

• Hyperplastic polyps: Sessile, smooth, <10 mm, no malignant potential
• Adenomatous polyps: Sessile, lobulated, >2 cm = malignant potential; filling defect on barium
• CT: Focal intraluminal filling defect, enhancing lesion

3. Leiomyoma (GIST - Gastrointestinal Stromal Tumor, benign)

• Submucosal mass, smooth, bull's-eye lesion
• Central ulceration = "target lesion" on barium
• CT: Exophytic, homogeneous, enhancing mass

4. Ménétrier's Disease

• Giant rugal hypertrophy (folds >1 cm) on barium
• Predominantly in fundus/body
• CT: Marked mucosal thickening, protein-losing enteropathy

MALIGNANT LESIONS

1. Gastric Carcinoma (Adenocarcinoma - 95%)

• Barium meal signs:
  • Filling defect (polypoid type - best prognosis)
  • Irregular ulcer (malignant ulcer): Meniscus sign (Carman's sign/Meniscus of Carman), irregular base, raised edges ("mound of Kirklin"), interrupted folds ("clubbed folds")
  • Linitis plastica: Rigid, narrowed "leather bottle" stomach (Borrmann type IV), poor distensibility, no peristalsis
• CT staging:
  • T1: Mucosal layer
  • T2: Muscularis propria
  • T3: Through serosa
  • T4: Adjacent organs
  • Regional nodes, liver mets, peritoneal deposits
  • Krukenberg tumor: Ovarian metastases

2. Gastric Lymphoma (MALT lymphoma, Diffuse large B-cell)

• H. pylori associated
• Barium: Thickened, lobulated folds + ulcers, flexible (not rigid like carcinoma)
• CT: Homogeneous thickening, bulky lymphadenopathy, preserved fat planes

3. GIST (Gastrointestinal Stromal Tumor)

• Submucosal origin, exophytic growth
• CT: Large, heterogeneous (central necrosis/hemorrhage), enhancing mass
• "Dumbbell" shape (endo and exophytic components)
• c-kit (CD117) positive

4. Gastric Carcinoid

• Multiple small enhancing lesions (associated with type A gastritis)
• Submucosal nodules

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All answers are written at 30-mark examination standard (DMRD/MD level). Each answer includes: introduction, classification/enumeration, imaging findings across modalities, distinguishing signs/mnemonics, complications, and comparison tables where relevant. These cover all questions visible in your 2025 exam paper images.