To investigate the clinical efficacy of low-power high-intensity focused ultrasound (HIFU) combined with medium-frequency breast therapy device in the treatment of severe lactational mastitis and its impact on immune function.

A retrospective randomized controlled study was conducted, including 208 patients with severe lactational mastitis admitted from January 2021 to January 2024. Patients were divided into combined treatment group (104 cases, low-power HIFU + medium-frequency breast therapy device) and control group (104 cases, conventional treatment). The fever clearance time, milk flow rate, visual analogue scale (VAS) pain score, and peripheral blood NK cell activity and inflammatory factor levels were compared between the two groups.

The fever clearance time in the combined treatment group was (2.89±1.25) days, significantly shorter than (5.21±1.58) days in the control group (P<0.001). The milk flow rate was 94.23%, significantly higher than 76.92% in the control group (P<0.001). The VAS pain score after treatment decreased to (2.02±0.32) points, significantly lower than (3.56±1.17) points in the control group (P<0.001). The activity of NK cells significantly increased (P<0.001), and was significantly higher than that of the control group (P<0.001). The levels of serum IL-6 and TNF-α significantly decreased (P<0.001), and were significantly lower than those of the control group (P<0.001).

Low-power HIFU combined with medium-frequency breast therapy device can significantly shorten the course of severe lactational mastitis and improve clinical symptoms. The mechanism may be related to regulating immune function and reducing inflammatory response.