Solitary necrotic nodule of the liver (SNNL) is a rare and benign liver lesion often discovered incidentally. Despite its occurrence, the exact cause of SNNL remains unknown, with various theories proposing traumatic, infectious, degenerative or transformative origins. The variable imaging characteristics of SNNLs frequently lead to misdiagnosis as malignant tumors, prompting patients to undergo unnecessary and high-risk procedures such as biopsies and surgeries. Moreover, biopsies often yield inconclusive results due to the presence of necrotic tissue within the lesion, posing challenges for accurate histologic diagnosis. This review aims to offer guidance on differentiating SNNLs from other liver lesions using multimodality imaging approaches. It will analyze essential imaging steps that should be performed and highlight those that should be avoided to enhance diagnostic accuracy and prevent unnecessary interventions.

Solitary necrotic nodule of the liver (SNNL) is a rare benign lesion with a complete necrotic core and a clear fibrous capsule containing elastic fibers. We present the case of a patient with a radiographic computed tomography (CT) finding of "ring"-like annular calcification within the lesion and postoperative pathologic diagnosis of necrotic nodules wrapped by dense fibers in liver tissue, as well as the patient's subsequent management and outcome.

A 38-year-old Chinese woman with a history of systemic lupus erythematosus treated with prednisone and hydroxychloroquine, without any symptoms, was found to have hepatic space-occupying lesions by imaging examination at a health examination. A subsequent CT scan suggested a space-occupying lesion of the liver with annular calcification, which was not defined to be benign or malignant. After that, a laparoscopic hepatic space-occupying resection was performed. The postoperative pathological diagnosis was necrotic nodules wrapped by dense fibers in the liver tissue, and the final diagnosis was SNNL. The patient had an uneventful postoperative recovery.

There is a "ring"-like calcification in SNNL. This patient had a history of systemic lupus erythematosus, without a history of parasite infection, trauma, or tumor. Therefore, whether the etiology and pathological changes of SNNL are related to rheumatic immune diseases remains to be investigated.

Focal lesions in fatty liver are difficult to diagnose using conventional ultrasonography (CVUS). The aim of this study was to investigate the characteristics of solitary necrotic nodules (SNNs) in fatty liver using CVUS and contrast-enhanced ultrasonography (CEUS) and to evaluate the diagnostic value of CEUS for SNNs in fatty liver.

Fifteen SNNs in the fatty liver of fifteen patients were examined by both CVUS and CEUS. The contrast agent SonoVue was used for CEUS. The characterization and shape of these SNNs in the fatty liver were analyzed using CEUS.

CVUS revealed eight oval-shaped, six irregularly shaped, and one wedge-shaped SNN in the fatty liver. The six irregularly shaped lesions on CVUS were revealed to comprise four gourd-shaped, one serpiginous, and one 3-pin socket-shaped nodule on CEUS. One of these SNNs showed a subcapsular wedge shape, with peripheral and distinct internal septal hyperenhancement in the arterial phases that washed out in the portal phase; moreover, most areas of th lesion showed no internal enhancement in any of the three phases. Fourteen of the lesions were characterized as lacking internal enhancement, and 12 of them had mild-moderate peripheral thin enhancement in the arterial phases. Twelve of the 15 nodules could be considered for diagnosis as SNNs by CEUS, which was further proved by US-guided biopsy and histopathology. However none of them could be considered for diagnosis as SNNs by CVUS.

CEUS is a valuable tool for visualizing the characteristics of SNNs in fatty liver to improve the differential diagnosis.