Abdominal Wall Defects Omphalocele Definition: incomplete formation of the embryonic ventral abdominal wall leads to a congenital midline anterior abdominal wall defect around the umbilicus (the umbilical cord inserts at the tip of the defect) ▪ Larger omphaloceles (containing liver tissue): these are due to failure of fusion of the lateral body folds ▪ Smaller omphaloceles (containing bowel only): these are due to the persistence of…

Abnormal Gas Distribution Pneumoperitoneum Definition Free intra-abdominal gas – it usually indicates perforation of a viscus (it is often a peptic ulcer – a perforated appendix rarely demonstrates free gas) ▪ Other causes: bowel obstruction ▸ appendicitis ▸ bowel ischaemia ▸ diverticular disease ▸ post colonoscopy Radiological Features Erect CXR Gas is seen under the diaphragm (this can detect as little as 1 ml of free gas)…

Benign Diseases Ascites Definition >100 ml of free fluid within the peritoneal cavity due to benign or malignant causes ▪ Transudative fluid: portal hypertension/cirrhosis/heart failure/nephrotic syndrome ▪ Exudative fluid: infection/peritoneal carcinomatosis ▪ Blood: trauma/tumour rupture/haemorrhagic diathesis ▪ Purulent fluid: intestinal perforation ▪ Others: bile (biliary leakage)/chyle (lymphatic obstruction)/pancreatitis fluid Exudates may be limited by peritoneal reaction/adhesions ▸ transudates diffuse freely Ascites usually seen in the pouch of…

Miscellaneous Splenic Conditions Normal variants and congenital anomalies Splenunculus: this represents ectopic splenic tissue of congenital origin ▸ they can be single or multiple and are usually found at the splenic hilum ▸ they have similar imaging (and enhancement) appearances to the spleen Wandering spleen: this follows laxity of the suspensory ligament ▸ torsion may occur Polysplenia: the spleen is divided into 2–16 masses ▸ this…

Congenital Abnormalities Embryology The pancreas develops in two parts from the endoderm of the primitive duodenum Dorsal part: this is the first part to appear, initially appearing as a diverticulum from the dorsal wall of the duodenum ▸ it forms the neck, body and tail of the gland and part of the head Ventral part: this develops more caudally and initially appears as a diverticulum from…

Methods of Investigation Magnetic Resonance Cholangiopancreatography (MRCP) Technique Heavily T2-weighted coronal oblique fast spin-echo sequence to obtain source data (aligned along the plane of the common bile duct [CBD]) ▪ Stationary water appears as areas of high SI and adjacent soft tissue is low SI (therefore it is not reliant on contrast excretion and can be used in jaundiced patients) ▪ Fasting reduces any unwanted signal…

Anatomy and Imaging Techniques Anatomy Couinaud classification The liver is subdivided anatomically into 8 segments; segments II – VIII are divided anatomically via the portal and hepatic veins The caudate lobe (segment I): this is autonomous, receiving vessels from both the left and right portal vein branches and the hepatic artery ▸ it has an independent venous drainage directly into the IVC Vascular anatomy Blood supply…

Ulcerative Colitis and Toxic Megacolon Ulcerative Colitis (UC) Definition A relapsing and remitting inflammatory bowel disease predominantly involving the colorectal mucosa and submucosa ▸ there is symmetrical colonic involvement (cf. asymmetrical Crohn's disease) It always involves the rectum – any remaining colitis is in continuity with its proximal extent ▪ Proctitis: inflammatory changes limited to the rectum Clinical presentation Bloody diarrhoea (± constitutional symptoms) in young…

Crohn's Disease (CD) Crohn's Disease Definition A chronic progressive transmural granulomatous inflammatory bowel disease There are typically discontinuous (‘skip’) lesions with asymmetrical bowel wall involvement It can affect any part of the GI tract – however it almost always affects the terminal ileum (in 95% of cases) Radiological features Barium studies Bowel wall ulceration ▪ Aphthoid ulcers: characteristic superficial ulcers that do not penetrate the muscularis…

Peptic Ulceration, Gastric Heterotopia, Duodenal Diverticula Peptic Ulceration Definition Mucosal ulceration occurring within an acidic part of the GI tract ▸ it is often associated with H. pylori infection ▸ duodenal ulcers are 2–3x more common than gastric ulcers ▪ Bulbar ulcers (95%): these are usually benign – Location: anterior wall > posterior wall ▪ Postbulbar ulcers (5%): these are usually malignant (95%) and fail to…

Benign Gastric Ulcers Benign Gastric Ulcers Definition Gastric ulcers penetrate the stomach wall through the mucosa and into the submucosa (and frequently also into the muscularis propria) ▸ 95% are benign and they can also be multiple Causes Helicobacter pylori infection (70%) ▸ NSAIDs ▸ alcohol abuse ▸ steroid use ▸ emotional stress ▸ smoking ▸ hereditary factors Radiological features Location Distal stomach > proximal stomach…

Hiatus Hernia and Reflux Hiatus Hernia Definition Protrusion of part of the stomach through the diaphragmatic oesophageal opening ▪ Type 1 – sliding hernia (the commonest type): the gastro-oesophageal junction (GOJ) slides proximally through the diaphragmatic hiatus to assume an intrathoracic position ▸ it is accompanied by reflux and oesophagitis – The squamocolumnar junction is seen at ≤38 cm (the normal is 40 cm) from the incisors at…

Conventional Coronary Angiography and Echocardiography Conventional Coronary Angiography This involves the selective injection of contrast medium into the right and left coronary arteries and the left ventricle (while recording the resultant moving images) Being replaced by non-invasive CCT and CMR Technique A percutaneous femoral arterial catheterization is the usual approach (an alternative percutaneous route is the radial artery) ▸ at least 3 shaped catheters are required…

Gastrointestinal Vascular Disorders Mesenteric Haemorrhage Upper gastrointestinal (GI) haemorrhage This is defined as bleeding proximal to the duodenal–jejunal flexure (most commonly from the left gastric artery) Causes: peptic ulceration ▸ pancreatitis ▸ gastro-oesophageal varices ▸ as a complication of endoscopic, surgical, or percutaneous biliary procedures Lower GI haemorrhage This is defined as bleeding distal to the duodenal–jejunal flexure and is less commonly seen Causes: colonic angiodysplasia…

Aortic Rupture Traumatic Aortic Injury (TAI) Definition This occurs as a result of a rapid deceleration injury generating shearing forces at the aortic isthmus ▸ other mechanisms of injury include an AP compression force displacing the heart to the left (a torsion stress) ▪ Incomplete rupture: the adventitia remains intact (maintaining the aortic integrity) in the majority of survivors ▸ the saccular outpouching that can develop…

Pulmonary Thromboembolic Disease Pulmonary Thromboembolic Disease Definition A pulmonary embolus (PE) usually arises from a thrombus within a pelvic or lower limb vein (>90%) ▪ ‘Saddle’ embolus: a thrombus lodged at the main pulmonary arterial bifurcation ▪ Pulmonary infarction: This is relatively rare as there is a second ‘systemic’ arterial supply to the lungs from the bronchial arteries Risk factors for a pulmonary embolism: increasing age…

Acquired Mitral Valve Disease Mitral Regurgitation Definition An incompetent mitral valve allowing regurgitant flow from the left ventricle (LV) into the left atrium (LA) during systole (mid-to-late systolic murmur) ▸ maintaining an adequate stroke volume requires an increased ventricular stroke volume and ejection fraction Clinical presentation Acute regurgitation (e.g. ruptured chordae tendineae): sudden volume loading with acute pulmonary oedema/heart failure Chronic regurgitation (e.g. hypertrophic cardiomyopathy): volume…

Lung Transplantation Lung Transplantation Definition Single lung transplantation This is indicated for non-suppurative lung disease: emphysema ▸ idiopathic pulmonary fibrosis ▸ sarcoidosis ▸ lymphangioleiomyomatosis Bilateral sequential lung transplantation This is indicated for suppurative lung disease: cystic fibrosis ▸ bronchiectasis Preoperative Imaging Typical imaging procedures that are performed: PA and lateral CXR ▸ CT chest ▸ quantitative ventilation–perfusion scintigraphy This can determine the optimum side for a…

Congenital Chest Abnormalities Congenital Pulmonary Airway Malformations (CPAM) Definition Previously known as congenital cystic adenomatoid malformation (CCAM) A rare lesion caused by hamartomatous proliferation of the terminal bronchioles at the expense of alveolar development ▸ it is characterized by a multicystic mass of pulmonary tissue with proliferation of the bronchiolar structures It is usually unilobar and communicates with a normal tracheobronchial tree ▸ it receives its…

Airspace Disease Pulmonary Oedema Definition An excess of extravascular lung water ▪ Cardiogenic oedema: increased hydrostatic pressure moves fluid out of the vascular compartment ▸ this is commonly caused by left heart failure ▸ it is rarely caused by a reduction in plasma osmotic pressure (e.g. hypoalbuminaemia) ▪ Non-cardiogenic oedema: this is caused by an increased alveolar-capillary barrier permeability – Causes: fluid overload ▸ drowning ▸…