Limpomatous hypertrophy of the inter-atrial septum is a condition caused by benign proliferation of adipocytes in the inter-atrial septum. The condition is thus a hyperplasia rather than hypertrophy (cell enlargement) and some authors have proposed naming it as such ¹. It is usually asymptomatic and an incidental finding but may be associated with atrial arrhythmias ². Prevalence is estimated to 2-8% ^{3, 4}. There is a tendency for it to occur more amongst the elderly and the obese ¹.

The condition is characterized on CT by fat attenuation thickening of the inter-atrial septum. There is characteristically sparring of the fossa ovalis making the septum narrow and then thicken again on cross section giving rise to an appearance referred to as “dumbbell” like in shape ².  This is clearly demonstrated in the key image above.

The thickening is often more prominent cranially and there have been at least 1 reported case where the SVC/atrial junction had been obstructed secondary to mass effect ⁵. In a case series of 12 patients by Meaney et al, 4 had 50-100% circumferential fatty involvement of the SVC and the remaining 8 all had at least 25% involvement ².