Rectus-based Stoma and Rectus Abdominis Myocutaneous Flap Laterality Planning for Perineal-Anal Defects After Hemipelvectomy.

Perineal-anal defects are difficult to manage because negative-pressure wound therapy (NPWT) commonly fails to achieve an airtight seal, and stool contamination hinders wound-bed preparation. Fecal diversion is often required, with a stoma typically created within the rectus abdominis muscle. When a rectus abdominis myocutaneous (RAM) flap is planned, the stoma and flap must be placed on opposite sides, making laterality planning essential. Assessment of the deep inferior epigastric artery (DIEA) patency is critical because vascular compromise may limit flap harvesting. Herein, we report a rare case of pelvic necrotizing soft-tissue infection (NSTI) requiring hemipelvectomy in which coordinated stoma planning, vascular evaluation, and RAM flap reconstruction enabled successful treatment. A 63-year-old woman presented with a fulminant NSTI extending from the lower limbs to the pelvis. Despite emergency hip disarticulation, the infection progressed, necessitating a hemipelvectomy. To allow complete NPWT coverage, fecal diversion was planned. Preoperative computed tomography angiography revealed right DIEA occlusion, precluding RAM flap harvesting on that side; therefore, a "left-sided" RAM flap was selected, with the stoma created within the "right" rectus abdominis muscle. After hemipelvectomy and repeat NPWT-assisted debridement, definitive reconstruction using a left RAM flap with skin grafting achieved stable wound coverage. Successful reconstruction after hemipelvectomy for NSTI requires reliable DIEA evaluation, precise laterality planning, and coordinated multidisciplinary management. Preoperative computed tomography angiography is critical to determine the appropriate side for stoma creation and preserve the RAM flap donor muscle. A structured sequence integrating fecal diversion, NPWT, and flap selection enables safe and definitive soft-tissue closure.