A 54-year-old man with uncontrolled hypertension (BP 168/104 mmHg) and evidence of end-organ damage presents for evaluation. Fundoscopy reveals the retinal findings shown in the image. The structure marked **B** at the arteriovenous crossings is a hallmark finding of hypertensive retinopathy. Which of the following best describes the pathophysiological mechanism underlying this finding?
A. Occlusion of the arteriole by platelet aggregation and fibrin deposition
B. Neovascularization of the optic disc in response to chronic retinal ischaemia
C. Rupture of the venule wall leading to flame-shaped haemorrhages at the AV junction
D. Compression of the venule by a sclerotic arteriole, causing venous obscuration at the crossing point (Gunn's sign)
Explanation
Why "Compression of the venule by a sclerotic arteriole, causing venous obscuration at the crossing point (Gunn's sign)" is right
Arteriovenous nicking (Gunn's sign), marked as B in the diagram, is a pathognomonic finding of hypertensive retinopathy. It occurs when chronic hypertension causes arteriolar wall thickening and sclerosis, leading to compression and obscuration of the underlying venule at the arteriovenous crossing. This is a hallmark of Keith-Wagener Grade 2 hypertensive retinopathy and represents structural vascular remodelling from sustained elevated blood pressure. According to Harrison's Principles of Internal Medicine (21st Edition), this finding is an important prognostic marker of hypertensive end-organ damage and indicates the need for aggressive antihypertensive therapy.
Why each distractor is wrong
Rupture of the venule wall leading to flame-shaped haemorrhages at the AV junction: Flame haemorrhages and cotton-wool spots are features of Grade 3–4 hypertensive retinopathy (malignant hypertension), not Grade 2. The patient's fundoscopy explicitly shows absence of these findings (marked as D).
Occlusion of the arteriole by platelet aggregation and fibrin deposition: This describes acute thrombotic events seen in malignant hypertension or acute coronary syndromes, not the chronic structural remodelling characteristic of Grade 2 hypertensive retinopathy.
Neovascularization of the optic disc in response to chronic retinal ischaemia: Neovascularization is a feature of proliferative diabetic retinopathy and advanced hypertensive retinopathy (Grade 4), not Grade 2. The optic disc in this patient shows sharp margins with no papilloedema (C).
