Lameness Misc

Question 1

Clinical signs of aortoiliac thrombosis

Answer 1

Disease is characterised by intermittent claudication = pain dt decreased blood flow

Exercise-induced hindlimb lameness which generally resolves promptly with the cessation of exercise, decreased digital pulses and saphenous fill and a palpably cooler affected limb

Can be much more subtle - severity depends on the extent of the occlusion and perhaps the available collateral circulation and which vessel(s) is occluded.

External iliac artery &/or femoral artery occlusion of > 60% → exercised induced lameness is the predominant sign; can (less commonly) see marked pain at rest (sweating, colic signs etc)

Internal iliac aa; CSs and significance are less clear; internal iliac branches into caudal gluteal and internal pudendal aa’s (supplying the penis) so can rx in ↓ perfusion pressure & arterial flow to the sinusoidal spaces of the penis, thus ↑ time to max erection & ↓ penile rigidity. Reduced perfusion to the muscles of the croup/gluteal regions could result in soreness and intermittent lameness.

However no clinical reports have been written on whether complete obstruction of the internal iliac artery is associated with clinical signs. Based on Reikhausen (2019 EVE CC) US findings, horses which underwent a thrombectomy of the external iliac and femoral artery which revealed an additional occlusion of the internal iliac artery were able to perform as previously - ie internal iliac occlusion seems to bear less clinical significance.

Question 2

Diagnosis of aorto-iliac thrombosis

Answer 2

Classical CSs of exercised induced lameness which quickly resolves in some cases

Trans-rectal US +/- Doppler to visualise the thrombus in situ

Both femoral arteries should be imaged from the proximomedial aspect of the thigh (use subcutaneous medial saphenous vein as a landmark). Emboli can occlude the femoral artery even when the external iliac artery is not obliterated by an aortic thrombus

Scintigraphy - cold limb cut off

PME

Question 3

Treatment options and px for aorto-iliac thrombosis

Answer 3

• Medical management is suitable for partially occluded vessels and incl. pentoxifylline (improves erythrocyte deformability, ↓ blood viscosity, & ↓ platelet reactivity and plasma hypercoagulability), aspirin and possibly cilostazol (inhibits platelet aggregation)
• Surgery is indicated for total occlusion, or those with partial occlusion and intermittent lameness (assuming dt femoral aa; depending on the loaction of the clot)
• Attempts at surgical removal with the use of balloon angioplasty (Hilton et al. 2008) and graft thrombectomy catheters (Brama et al. 1996; Rijkenhuizen et al. 2009) via a transverse femoral arteriotomy have been successful, with up to 65% of patients regaining athletic activity (Rijkenhuizen et al. 2009).
• Chronic femoral artery thrombi may be difficult to manage surgically; diameter of the obliterated femoral artery can be markedly decreased to nearly nonexistent. This makes thrombectomy almost impossible dt firm adherence of the thrombus to the arterial wall and the inability to create a lumen (through the thrombus with the cath)
• The prognosis is still generally considered poor, particularly in cases with bilateral involvement

Question 4

Vascular anatomy of the aortic quadrification

Answer 4

The terminal aorta divides at its end into the two internal iliac arteries. Cranially, the external iliac arteries emerge from the aorta to continue as femoral arteries more distally.