Specific imaging characteristic of solitary necrotic nodule of the liver: Marked peripheral rim-like enhancement with internal hypointensity on longer delayed MRI.

OBJECTIVES: To obtain specific imaging findings of solitary necrotic nodule of the liver (SNNL) using longer delayed contrast-enhanced MRI and compare them with those of three mimic hepatic diseases.

METHODS: Sixteen patients with SNNL underwent plain and contrast-enhanced triphasic CT and multiphasic MRI with delayed time prolonged to 2 h after contrast bolus injection. Twenty-three patients with mimic lesions including seven with eight HCCs, five with five iCCs and 11 with metastatic lesions served as the control group. Those patients also received plain and multiphasic contrast-enhanced MRI. Imaging features of lesions such as peripheral wash-out time were evaluated.

RESULTS: Among the 16 SNNLs, with a prolonged delayed MRI time, the enhancement degree of tumour periphery increased gradually. When it was up to 1 h, all lesions represented moderate/marked peripheral enhancement with internal hypointensity. However, the peripheral wash-out in seven HCCs (87.5%) and all metastatic lesions except three appeared at 10 or 15 min, one iCC (20%) at 30 min and the other lesions at 1 h.

CONCLUSIONS: Longer MRI with a delayed time of 1-2 h may be useful in diagnosis SNNL, revealing the specific imaging characteristic of SNNL as pronounced peripheral enhancement with internal hypointensity.

KEY POINTS: • Longer delayed MRI plays an important role in the diagnosis of SNNL. • Characteristic imaging feature of SNNL is pronounced peripheral enhancement with internal hypointensity. • Periphery wash-out time can differentiate SNNL from mimic diseases. • Imaging findings of SNNL on routine CT and MRI are unspecific.