Deep inferior epigastric artery perforator (DIEAP) flap is considered the gold standard for autologous flap for breast reconstruction in many centres. Computerised tomography angiogram (CTA) is often, but not always, used in preoperative planning in free flap breast reconstruction to identify the DIEA perforators, measure vessel calibre and identify any anatomical variations. We present a case with an unusual absence of left-side unilateral rectus abdominus and associated DIEAP system. A 50-year-old patient presents for an immediate, bilateral breast reconstruction after being diagnosed with right-sided invasive lobular breast carcinoma. She has a Pfannenstiel incision scar for an excision of a large ovarian cyst 15 years prior. She was referred for a pre-op CTA abdomen with an incidental finding of left-sided RA muscle and associated deep inferior epigastric blood vessel system absence. Isolated RA deficiency is a very rare condition with unknown prevalence. Only 2 published case reports citing this finding is found (Rozen et al. & Harris et al.). Due to the nonexistence of the left DIEA/V, she ended up having a unilateral right breast reconstruction and a left breast reduction for symmetrisation. This report highlights the important role of preoperative CTA, which demonstrates potential hazards in raising a DIEAP flap as it facilitates surgical planning and improves patient safety and surgical efficiency. References: Harris, T.G.W, et al. Congenital absence of the deep inferior epigastric system: a case report. Eur J Plast Surg 2019. Rozen, W.M, et al. The absent inferior epigastric artery: a unique anomaly and implications for deep inferior epigastric artery perforator flaps. J Reconstr Microsurg. 2009