Free UKMLA clinical imaging questions with explanations

C. MRI of the whole spine

MRI of the whole spine is the investigation of choice for suspected metastatic spinal cord compression because it provides superior soft-tissue contrast for visualising the cord, epidural space and vertebral marrow without ionising radiation. MRI is recommended within 24 hours of clinical suspicion, and the whole spine must be imaged as multiple non-contiguous levels of compression are present in up to a third of malignant cases.

B. Transvaginal ultrasound with Doppler

Pelvic ultrasound with Doppler is the first-line investigation for suspected ovarian torsion because it is rapid, avoids radiation in a young woman, and shows the typical enlarged, oedematous ovary with peripherally displaced follicles, often with a cyst as the lead point and free fluid. Doppler may show reduced or absent flow, although preserved flow does not exclude torsion. CT is reserved for when the differential is wide or ultrasound is unavailable, and MRI is too slow for an emergency in which time equals ovarian survival. Laparoscopy is the definitive diagnostic and therapeutic step, but it follows imaging in a stable patient rather than replacing it.

D. Contrast-enhanced CT of the chest

Contrast CT of the chest shows the site and degree of superior vena cava narrowing, distinguishes extrinsic compression by tumour from intraluminal thrombus, maps the collateral circulation and provides the anatomy needed to plan stenting or radiotherapy. A chest radiograph usually shows a widened mediastinum or right-sided mass but cannot define the venous obstruction or its cause. Echocardiography and upper limb Doppler each look at a part of the venous system but not at the vena cava itself in the mediastinum.

C. CT abdomen with intravenous iodinated contrast

Contrast-enhanced CT of the abdomen and pelvis is the standard investigation to characterise a collection, leak, bowel-wall viability and vascular anatomy before theatre in perforated diverticulitis. Contrast-associated AKI should be risk-assessed rather than treated as a contraindication, and contemporary evidence places that risk much lower than historically taught. In a septic patient going for source control regardless, the diagnostic benefit of contrast outweighs the renal risk, which would not alter the need for surgery.

C. No further follow-up of the cyst is required

In a premenopausal woman a simple cyst under 5 cm is almost always physiological, a follicle or corpus luteum, and resolves within a few menstrual cycles. UK guidance is that such cysts need neither follow-up imaging nor tumour markers. Ultrasound surveillance is reserved for simple cysts of 5 to 7 cm, and cysts above 7 cm need MRI or surgery because ultrasound cannot fully characterise them. CA-125 is not measured for an ultrasound-diagnosed simple cyst in this age group because it is raised by many benign conditions, endometriosis and menstruation among them, and would generate false alarms.

D. Lambda sign at the membrane insertion

Chorionicity is best determined at the 11 to 14 week scan and is the single most important piece of information in a twin pregnancy, because it dictates surveillance and timing of birth. In a dichorionic pregnancy each twin has its own placenta and the chorion extends into the base of the dividing membrane, producing a triangular wedge of placental tissue, the lambda or twin peak sign, with a thick four-layer membrane. In a monochorionic diamniotic pregnancy the two amnions meet the single placenta directly, giving a thin two-layer membrane inserting as a T. No dividing membrane means a monochorionic monoamniotic pregnancy. Fetal sex is unhelpful: different sexes prove dichorionicity but same-sex twins can be either.

A. Supracondylar humeral fracture

Supracondylar humeral fractures are the commonest paediatric elbow fracture, typically occurring after a fall onto an outstretched hand in children aged 5-7. The displaced extension-type variant can tent or entrap the brachial artery, producing a cool, poorly perfused hand. Urgent neurovascular assessment and prompt closed reduction with K-wire fixation are needed for displaced injuries to prevent Volkmann ischaemic contracture.

C. Achilles tendon rupture

Sudden onset calf pain in a sprinting athlete with the sensation of being struck, a palpable gap just proximal to the calcaneal insertion and weak resisted plantarflexion is characteristic of Achilles tendon rupture. The defect typically lies 2-6 cm above the insertion in the relatively hypovascular zone; UK BOA/BOFAS guidance supports either functional bracing in equinus or surgical repair depending on patient factors.

B. MRI of the femur

MRI is the investigation of choice for suspected acute osteomyelitis because it detects bone marrow oedema within 1–2 days of onset, well before plain radiographic changes appear (which require 30–50% bone mineral loss and typically take 10–14 days). MRI is the preferred imaging modality given its high sensitivity and specificity for early disease and its ability to delineate associated abscesses.

B. PTHrP secretion by squamous cell carcinoma

Squamous cell carcinoma of the lung classically secretes parathyroid hormone-related peptide (PTHrP), which binds PTH receptors on bone and kidney to drive calcium resorption and renal calcium retention while suppressing endogenous PTH via negative feedback. A cavitating hilar mass in a heavy smoker with severe hypercalcaemia and suppressed PTH is the textbook presentation of this humoral hypercalcaemia of malignancy.