Tailgut cysts typically appear on CT as homogeneous hypoattenuating, well marginated, thin wall non-enhancing cystic lesions mostly multiloculated and located in the retrorectal space [4]. In rare cases they are associated thin calcifications [3].

On MRI imaging Tailgut cysts present as homogeneous hypointense on T1-weighted images and hyperintense in T2-weighted images [1].

Imaging features that suggest a superimposed infection or malignancy on CT and MR are irregular wall thickening with intermediate signal on T1 and T2 weighted images and enhancement after the administration of intravenous contrast [4]. Internal heterogeneity, intracystic vegetations and presence of enhancing components of the lesion indicate worrisome features [2]. The presence of calcifications, blurred margins and invasion of adjacent structures are also signs of malignant transformation [3].

Fig 3: No contrast enhanced CT axial images (a), (b) and axial MR T1 weighted image...

Fig 4: No contrast enhanced CT axial image (a) of a 69 year old women and MR axial T1...

Fig 5: Contrast enhanced CT axial image of a 76 year old woman. The image displays a...

MRI is probably not the best imaging modality to completly differentiate malignant from benign lesions [1, 3]. This is because a high content of protein, mucinous tissues, or internal hemorrhage might lead to a high T1 signal intensity, which has been reported in cases of Tailgut cysts with malignant transformation, and also calcifications are not easily detected using MRI. Fat suppression techniques are helpful for the diagnosis of lipoma and can exclude solid portions [3].