Diagnostic Radiology SC085: Radiology Of Common Medical And Surgical Problems

Question 1

Acute pancreatitis

Answer 1

• Inflammation of pancreatic tissue
• Obstruction of small pancreatic ducts
• Leak of pancreatic juices to surrounding tissues
• Swollen edematous pancreas with areas of haemorrhage and necrosis
• Peripancreatic fluid collection
• Interstitial edematous vs Necrotising pancreatitis
• Chronic pancreatitis: Calcification of pancreas

Role of imaging:
1. Confirm diagnosis (if symptoms atypical / serum amylase, lipase level less than expected)
2. Determine cause of pancreatitis, exclude neoplasm / confirm presence of gallstone
3. Patient’s condition does not improve (look at disease severity)
4. Monitor evolution + complications

NB:
- Imaging often normal on first day
- Imaging does not correlate well with clinical symptom severity
- Diagnosis mainly clinical

Necrotising pancreatitis:
- Necrosis of pancreatic head: Non-enhancement (Necrotising pancreatitis) with acute necrotic collections (ANC)
- Extrapancreatic spread of inflammation: Fluid collection, Obliteration of peripancreatic soft tissue, Fascial thickening in pararenal space and lesser sac

Other complications:
- Walled off necrosis (WON) —> can develop into abscess, fistula
- Ascites
- Mesenteric involvement (e.g. Thrombosis of portal vein, SMV)

Question 2

LUL collapse

Answer 2

Investigations:
1. Blood / Sputum culture, analysis / BAL
2. Contrast CT thorax
3. Bronchoscopy

LUL collapse secondary to TB stricture:
1. Hazy / Veil-like appearance
2. Tented left hemidiaphragm (∵ volume loss)
3. Increase retrosternal density on lateral CXR
4. Look for proximal obstructing lesion

Collapse due to hilar mass obstruction (e.g. neoplastic lesion):
1. Golden S sign (凹入去: collapsed lung, 凸出黎: Hilar mass)

Question 3

Appendicitis

Answer 3

• Most frequent condition requiring emergency surgery (80%)
• Produced by luminal obstruction, secondary distension, engorgement, edema, bacterial overgrowth
• Peak frequency in children: 12-15 yo

Pathophysiology:
- Faecolith / Scarring / (Lymphoid hyperplasia: Andre Tan) that occludes neck of appendix: Close loop obstruction
- Bacterial infection + ulceration of wall —> perforates —> abscess formation / generalised peritonitis

USG diagnosis:
- **Graded-compression technique (increasing force of compression on RIF) —> Focal tenderness
- **Lack of compressibility
- Transverse diameter ***>=6mm (distended + fluid-filled)
- Appendicolith
- Peri-caecal / Peri-appendiceal fluid
(- Echogenic mucosa (∵ hyperaemia)
- Increased vascularity (∵ hyperaemia))

Perforated appendicitis:
- Phlegmon (inflammatory mass) / Abscess —> Appendix may be difficult to identify, mucosa disrupted

Appendix abscess:
- Peri-caecal mass with fluid
- Infiltration of mesenteric fat

CT:
- Less operator dependent
- Higher sensitivity than USG (94% vs USG 88%)
- Non-visualisation of appendix on CT has high negative predictive value of 98.7%
- Indications:
—> Obese
—> Delineate disease extent in perforated appendicitis
—> Guide abscess drainage (although USG is better ∵ real-time)

Question 4

Paediatric intussusception

Answer 4

• Invagination / Prolapse of bowel segment (intussusceptum) into lumen of adjacent bowel (intussuscipiens) due to peristalsis
• Major cause of SBO in children, less common in adults
• Adult: 80% due to polypoid tumour
• Children: commonly near IC valve

Classic clinical triad:
1. Acute abdominal colic
2. Currant-jelly stool
3. Palpable abdominal mass (<50%)

Epidemiology:
- 6 months - 2 yo

Location:
- ***Ileocolic mostly in paediatric (Adult can be anywhere)

USG:
- ONLY for paediatric (NOT for adult)
- Primary modality for initial diagnosis
- Sensitivity 98-100%, NPV: 100%, Specificity: 88-100%
- Look for alternative diagnosis
- Longitudinal: Pseudokidney sign
- Transverse: Doughnut sign
—> Central ring: lumen of intussusceptum
—> Middle ring: mesenteric fat
—> Outer ring: bowel wall

Management:
- Pneumatic / Hydrostatic reduction under USG control (NOT for adult)