RD7.4 | Imaging in Surgery — Glossary

Acute inflammation of the vermiform appendix, usually following luminal obstruction; the commonest surgical emergency of the abdomen, diagnosed largely clinically and supported by imaging in equivocal cases.

Horizontal interfaces between gas and fluid within dilated bowel loops on an erect abdominal X-ray, indicating bowel obstruction; they confirm obstruction but cannot assess viability.

'As Low As Reasonably Achievable' — the radiation-protection principle that ionising radiation should be minimised, underpinning the preference for ultrasound and MRI over CT in children and pregnancy.

A clinical scoring system for the probability of acute appendicitis, combining migratory pain, anorexia, nausea/vomiting, right-iliac-fossa tenderness, rebound, fever, leucocytosis and a left shift; used to guide observation, imaging or surgery.

A localised, walled-off collection of pus arising from a perforated appendix, seen on CT or ultrasound; often managed initially with antibiotics and image-guided percutaneous drainage.

A calcified or inspissated faecolith within the appendiceal lumen, seen as an echogenic shadowing focus on ultrasound or a calcific density on CT; it may obstruct the appendix and is associated with complicated appendicitis.

A fracture of the skull base, suggested clinically by haemotympanum, periorbital ('panda') bruising, Battle's sign, or CSF rhinorrhoea/otorrhoea, and a high-risk criterion mandating CT.

Inadequate blood supply to the bowel, progressing from wall oedema to transmural infarction and perforation; on imaging it is shown by absent enhancement, wall thickening, free fluid and, late, pneumatosis.

The normal brightening of the bowel wall after intravenous iodinated contrast on CT; reduced or absent enhancement is the cardinal sign that a bowel loop is ischaemic.

The danger of perforation of a grossly dilated caecum (approaching 9-12 cm) in large-bowel obstruction, explained by Laplace's law whereby wall tension rises with diameter; a marker of urgency.

A validated clinical decision rule for minor head injury (GCS 13-15) that uses high-risk and medium-risk criteria to select patients needing a CT head, designed to be highly sensitive for clinically important brain injury.

A traumatic bruise of the brain seen on CT as patchy cortical haemorrhage and oedema, classically at the frontal and temporal poles (coup/contre-coup), which may enlarge ('blossom') over 24-48 hours.

A bowel segment obstructed at two points (e.g. the hernia neck), seen on CT as a C- or U-shaped fluid-filled loop with converging mesenteric vessels; intrinsically prone to ischaemia and strangulation.

An ultrasound technique that displays blood flow in colour; in a hernia it assesses perfusion of the trapped bowel wall — absent colour-flow suggests ischaemia.

An ileocaecal valve that prevents reflux of colonic contents into the small bowel; in large-bowel obstruction it creates a closed loop between the valve and the obstruction, raising the risk of caecal perforation.

CT of the abdomen and pelvis with intravenous iodinated contrast; the modality of choice to confirm a strangulated hernia, assess bowel viability by enhancement, and map complications such as closed-loop obstruction and perforation.

A fracture in which bone fragments are driven inward below the level of the inner table; an open or significantly depressed fracture requires surgical elevation and debridement.

Widespread shearing injury to axons from rotational forces, characteristically producing a conscious level far worse than the CT appearance; best detected by MRI gradient-echo/SWI sequences showing micro-haemorrhages at the grey-white junction, corpus callosum and brainstem.

Conservative management of simple intestinal obstruction comprising intravenous fluids with electrolyte correction (the 'drip') and nasogastric decompression (the 'suck'), with nil by mouth and close monitoring.

A collection of blood between the skull and the dura, appearing biconvex (lentiform) on CT and not crossing suture lines; classically arterial from a torn middle meningeal artery; a time-critical neurosurgical emergency.

A hernia passing through the femoral ring below and lateral to the pubic tubercle; small, more common in older women, and disproportionately likely to strangulate.

Gas free within the peritoneal cavity on imaging, indicating perforation of a hollow viscus — in a strangulated hernia, a sign that an infarcted loop has perforated.

Gas seen under the diaphragm on an erect chest or abdominal X-ray, indicating perforation of a hollow viscus; a contraindication to barium contrast studies.

A 3-15 point scale scoring eye, verbal and motor responses; used to grade head-injury severity (mild 13-15, moderate 9-12, severe ≤8) and as a trigger threshold in imaging decision rules.

An ultrasound technique using gradual transducer pressure to displace bowel gas and assess the appendix; the first-line investigation for appendicitis in children, young/thin adults and pregnancy.

The sacculations of the large bowel whose semilunar folds do NOT cross the full width of the lumen; their presence on peripheral dilated loops identifies large-bowel obstruction.

Drainage of an abscess through the skin using ultrasound or CT guidance to place a catheter; in appendicitis it allows non-operative treatment of a contained appendiceal abscess.

A hernia whose contents cannot be reduced back into the abdomen but remain viable; it may cause obstruction and can progress to strangulation if the blood supply becomes compromised.

Appendicectomy performed several weeks after initial non-operative management of complicated appendicitis (abscess or phlegmon), once acute inflammation has settled.

Failure of passage of bowel contents due to a mechanical block (or functional failure of peristalsis), presenting with colicky pain, vomiting, distension and absolute constipation; confirmed and characterised by imaging.

Obstruction of the large intestine, shown on plain film by peripheral dilated loops with haustra (colon >6 cm, caecum >9 cm); the commonest cause is colorectal carcinoma.

A period of restored consciousness between an initial post-traumatic loss of consciousness and subsequent deterioration, classically seen with an expanding extradural haematoma.

The displacing effect of an expanding intracranial lesion, seen on CT as effacement of sulci and ventricles, midline shift and, ultimately, herniation; often a stronger determinant of surgical urgency than the volume of blood alone.

Hazy, increased attenuation of the mesenteric fat on CT around an inflamed or ischaemic bowel loop, with engorged mesenteric vessels; a supportive sign of strangulation.

An artery running in a groove on the inner table of the temporal bone near the pterion; its rupture, often with a temporal-bone fracture, is the classic source of an extradural haematoma.

Displacement of central brain structures (e.g. the septum pellucidum) across the midline on CT, a sign of mass effect from a haematoma or oedema; a shift greater than about 5 mm is a common surgical threshold for an acute subdural haematoma.

Magnetic resonance imaging, which uses no ionising radiation; the preferred next investigation for suspected appendicitis in a pregnant woman when ultrasound is inconclusive.

Surgical removal of a normal, non-inflamed appendix; pre-operative imaging in equivocal cases, especially in women of reproductive age, reduces its rate by identifying alternative diagnoses.

UK national guideline criteria (NG232) specifying which head-injured patients require an urgent CT head, including GCS <13 on arrival, GCS <15 at 2 hours, suspected fractures, seizure, focal deficit, repeated vomiting and anticoagulant use.

The key ultrasound appearance of the inflamed appendix — a tubular structure arising from the caecum that ends blindly and does not compress under transducer pressure, with an outer diameter greater than 6 mm.

CT of the head performed without intravenous contrast; the modality of choice for acute head injury because it is fast, widely available, and highly sensitive for acute haemorrhage, fractures and mass effect.

Hazy increased attenuation of the fat around the appendix on CT, indicating inflammation; a supportive sign of acute appendicitis.

An inflammatory mass of matted bowel, omentum and appendix without a drainable collection; in appendicitis it is commonly managed non-operatively with antibiotics, with interval appendicectomy considered later.

Gas within the bowel wall seen on CT; a late and ominous sign of established transmural bowel ischaemia/infarction.

Gas tracking into the portal venous system on CT, branching toward the periphery of the liver; an advanced sign of bowel ischaemia and necrosis.

The dangerous return of a strangulated hernia, including its non-viable bowel and constricting sac, into the abdominal cavity by forceful reduction, which conceals the infarcted loop and risks delayed perforation and peritonitis.

Twisting of the sigmoid colon on its mesentery causing large-bowel obstruction, producing a classic 'coffee-bean' or inverted-U loop arising from the pelvis on plain film; often decompressed endoscopically.

Obstruction of the small intestine, shown on plain film by centrally placed dilated loops (>3 cm) with valvulae conniventes and air-fluid levels; the commonest cause in adults is adhesions.

A hernia in which the blood supply to the herniated contents is compromised, causing ischaemia; a surgical emergency diagnosed primarily clinically (irreducible, tense, tender hernia with obstruction).

A collection of blood between the dura and the arachnoid, appearing crescentic on CT and crossing suture lines but not the midline; usually venous from torn bridging veins; common in the elderly and anticoagulated.

The concentric-layer appearance of the inflamed appendiceal wall on transverse ultrasound, reflecting mural oedema.

The junction on CT between dilated proximal bowel and collapsed distal bowel; it localises the level of obstruction and often reveals the cause.

Haemorrhage into the subarachnoid space following trauma, seen on CT as hyperdensity tracking along the sulci, fissures and basal cisterns; common after significant head injury.

The circular mucosal folds (plicae circulares) of the small bowel that cross the FULL width of the lumen; their presence on a dilated, centrally placed loop identifies small-bowel obstruction.