**Region:** Trunk and Lower Back # Superficial Inferior Epigastric Artery (SIEA) Flap ## Anatomy - Pedicle: superficial inferior epigastric artery (SIEA) with venae comitantes and the superficial inferior epigastric vein (SIEV). Typical pedicle length reported 4–8 cm (Jabbour & Song, Ch.32; Lee & Paek, Ch.23). - Origin/course: SIEA most often arises from the common femoral artery approximately 1–3 cm below the inguinal ligament; frequently arises on a common trunk with the superficial circumflex iliac artery. It pierces deep fascia, courses deep to Scarpa’s fascia in the femoral triangle, then becomes subcutaneous as it travels toward the umbilicus; crosses the inguinal ligament at the midpoint between the ASIS and pubic symphysis (Lee & Paek, Ch.23; Jabbour & Song, Ch.32). - Venous drainage: SIEV lies superficial and medial to the artery in the subcutaneous plane and drains toward the saphenofemoral bulb. Venae comitantes accompany the artery and often connect with the superficial circumflex iliac vein (SCIV); multiple venous branches may form a common trunk near the saphenofemoral junction (Jabbour & Song, Ch.32). - Perforator pattern / angiosome: SIEA is a direct cutaneous (adipocutaneous) pedicle—does not traverse rectus muscle. The SIEA reliably supplies the ipsilateral hemiabdomen; extension across midline is variable and often limited (Lee & Paek, Ch.23). Clinical series report SIEA present in ~58% of clinical dissections and detectable on CTA in up to 94% of cases; SIEA diameter range reported 0.3–3.1 mm and a mean caliber around 0.6 mm in one CTA series (Lee & Paek, Ch.23; Jabbour & Song, Ch.32). Estimates of suitability to support a hemiabdominal flap were reported in the literature at ~24–31% of patients (Lee & Paek, Ch.23). - Nerves: sensory branches to lower abdominal skin derive from T10–T12 intercostal nerves. A true sensory branch that enters the panniculus without an intramuscular course may be encountered at the inferolateral rectus border and can be harvested for a sensate SIEA flap when present; however, intramuscular nerve harvest usually requires rectus exposure and is therefore not routinely performed with a pure SIEA harvest (Jabbour & Song, Ch.32; Lee & Paek, Ch.23). - Included tissues: skin and subcutaneous fat (adipocutaneous flap). No rectus sheath or muscle must be violated for a standard SIEA flap—complete preservation of abdominal wall fascia/muscle. Thickness equals patient pannus; flap is thin compared with TRAM/DIEP when harvested suprafascially. Arc of rotation for free transfer limited by pedicle length and location (pedicle is shorter and more lateral than DIEA), favoring ipsilateral-to-contralateral free transfers or pedicled coverage of nearby defects (Lee & Paek, Ch.23; Jabbour & Song, Ch.32). - Variants/anomalies: absence or hypoplasia of SIEA common; SIEA can originate from different trunks (common femoral, superficial circumflex iliac common trunk, deep femoral branches); venous anatomy is variable—venae comitantes sometimes small while SIEV may be dominant (Jabbour & Song, Ch.32; Lee & Paek, Ch.23). ## Dissection Steps 1. Positioning, markings, landmarks. - Patient supine. Mark midline, ASIS, pubic symphysis; mark lower transverse incision as low as feasible (low suprapubic line/just above pubic hairline) to maximize chance of encountering larger SIEA/SIEV and to obtain desirable donor scar (Lee & Paek, Ch.23; Jabbour & Song, Ch.32). - If reconstructing breast with internal mammary recipients, plan flap and orientation so pedicle will reach recipient vessels; consider contralateral hemiabdomen preference for internal mammary orientation (Lee & Paek, Ch.23). 2. Plane (suprafascial/subfascial), perforator identification (handheld/IO Doppler). - Make inferior suprapubic incision first and proceed suprafascially. Under loupes, dissect subcutaneous tissue carefully; expect SIEV superficial and medial to the SIEA. Do not complete full flap elevation until vessel calibre and perfusion are confirmed (Lee & Paek, Ch.23). - Intraoperative decision algorithm: assess SIEA for palpable pulse at incision level and measure or visually assess SIEV/venae comitantes. A palpable arterial pulse at incision and at least one vein ≥ 1.5 mm (or large vena comitans) are commonly used intraoperative criteria to proceed with SIEA harvest; if inadequate, convert to DIEP/MS-TRAM harvest (Jabbour & Song, Ch.32). - Optional: preoperative CTA/US can identify vessel presence and calibre but many surgeons use intraoperative exploration (Lee & Paek, Ch.23; Jabbour & Song, Ch.32). 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - Once SIEV identified, dissect SIEV and SCIV laterally toward saphenofemoral junction; dissect venae comitantes. If a common venous trunk exists, plan for single or multiple venous anastomoses accordingly (Jabbour & Song, Ch.32). - Identify SIEA (typically deep and lateral to SIEV). Preserve Scarpa’s fascia while freeing the artery. Follow artery caudally to its origin at common femoral artery to maximize length (open fascial hiatus to gain 1–2 cm extra length when needed). Clip side branches long for potential spatulation or graft use (Jabbour & Song, Ch.32). - Assess and manage arterial size mismatch: spatulate at a branch point or make an antimesenteric back-cut to enlarge SIEA diameter; have plan for small‑to‑small arterial anastomosis (Jabbour & Song, Ch.32). - Division: after recipient vessels prepared, ligate/clamp pedicle at its origin and harvest flap. For breast reconstructions deepithelialize the flap on the abdomen when possible to avoid traction on short pedicle during inset (Jabbour & Song, Ch.32). - Perfusion checks: visual assessment, handheld Doppler, tissue oximetry/clinical monitoring in immediate postop. If using DIEP backup strategy, preserve DIEA perforators until SIEA adequacy confirmed (Lee & Paek, Ch.23). 4. Donor-site closure techniques. - Flex the table to reduce tension. Undermine upper flap as needed; approximate Scarpa’s fascia and subcutaneous layers; place 1–2 suction drains (commonly two Blake drains suprapubically). Close in layers; no rectus sheath closure is required because fascia is not violated (Lee & Paek, Ch.23; Jabbour & Song, Ch.32). - If a periumbilical perforator was included, manage umbilicus as in abdominoplasty (reinset or neo‑umbilicoplasty per surgeon preference) (DIEP technique principles, Lee & Paek, Ch.23). ## Indications and Contraindications - Indications: - Autologous breast reconstruction when adequate ipsilateral hemiabdominal volume exists and SIEA/SIEV anatomy suitable (Lee & Paek, Ch.23; Jabbour & Song, Ch.32). - Pedicled local coverage of groin, pubic region, perineum, thigh; free tissue transfer for head & neck or other small-to-moderate defects needing thin adipocutaneous tissue (Lee & Paek, Ch.23). - When minimizing abdominal wall morbidity is a priority (SIEA preserves rectus fascia and muscle) (Jabbour & Song, Ch.32). - Combined or stacked flaps (SIEA + DIEP or bilateral SIEA stacked) when single hemiabdomen not enough (Lee & Paek, Ch.23; Jabbour & Song, Ch.32). - Contraindications: - Absolute/relative: prior abdominoplasty or long Pfannenstiel scar that transects the SIEA; any scar that likely cut the SIEA is a contraindication (Lee & Paek, Ch.23). - Relative: prior abdominal liposuction, active smoking (associated with higher partial flap/fat necrosis risk), small or absent SIEA/SIEV on intraoperative assessment (Lee & Paek, Ch.23; Jabbour & Song, Ch.32). - If the required volume extends more than ~2 cm beyond midline on contralateral side, SIEA alone is unreliable—plan bilateral or alternate flap strategy (Lee & Paek, Ch.23). ## Postoperative Care - Monitoring schedule/method: - Immediate postop: clinical checks (color, turgor, capillary refill), handheld Doppler, and adjunctive tissue oximetry as available; frequent checks in first 24 hours (Jabbour & Song, Ch.32). - Continue routine flap checks per institutional protocol; maintain warming and avoid tight dressings that compress pedicle. - Warming, antithrombotic practice, positioning/splinting, drains, mobilization, diet/analgesia: - Maintain normothermia and adequate hydration to minimize vasospasm risk. Chemical and mechanical DVT prophylaxis per institutional protocols. Early mobilization typically from postoperative day 1 as tolerated; drains removed when output low. Analgesia and anti-anxiety measures help prevent vasospasm (Jabbour & Song, Ch.32). - Return-to-OR thresholds and time windows: - Immediate re-exploration threshold: loss of arterial Doppler signal, progressive deterioration of clinical perfusion or steady fall in tissue oximetry despite conservative measures—prompt return to OR is advised because salvage chances decline with time (Jabbour & Song, Ch.32; Lee & Paek, Ch.23). - For suspected venous congestion: urgent return to OR if leeching/medical measures are insufficient or if flap rapidly deteriorates. ## Complications (rates & management) - Common problems (no consistent numeric rates in source texts): - Venous congestion—common concern due to variable superficial–deep venous connections; manage by urgent re-exploration and addressing venous outflow (consider additional venous anastomosis to SIEV/SCIV or vena comitans, convert/augment drainage). Preserve 3–7 cm of SIEV when possible to facilitate salvage (DIEP guidance: preserve SIEV length 3–7 cm) (Lee & Paek, Ch.22; Jabbour & Song, Ch.32). - Arterial thrombosis/vasospasm—SIEA prone to vasospasm; intraoperative papaverine and gentle handling, postoperative warming, pain/anxiety control, calcium-channel blockers if tolerated. If thrombosis occurs, prompt re-exploration; thrombectomy and revision of anastomosis or use of interposition graft (deep inferior epigastric artery graft) have been described as salvage techniques (Jabbour & Song, Ch.32). - Partial flap loss/fat necrosis—risk increased with small-caliber SIEA and when attempting to capture wide contralateral tissue; be conservative with zone beyond midline and consider conversion to DIEP or staged fat grafting when required (Lee & Paek, Ch.23). - Total flap loss—reported in the literature with SIEA flaps at rates variable between series; risk increases with small artery diameter and technical factors (Jabbour & Song, Ch.32). - Donor-site issues: - Low morbidity relative to TRAM/DIEP because fascia and muscle preserved; common donor issues are seroma, delayed wound healing, contour irregularity—no specific numeric frequencies provided in the SIEA chapters (Lee & Paek, Ch.23; Jabbour & Song, Ch.32). - Management algorithms (re-exploration, leeching, thrombolysis): - Algorithm highlights: - Preemptive: assess SIEA pulse and SIEV caliber intraop; if inadequate, convert to DIEP (Lee & Paek, Ch.23; Jabbour & Song, Ch.32). - Venous congestion: urgent re-exploration to revise venous anastomosis; if venous supercharging possible, perform additional anastomosis of SIEV/SCIV or vena comitans. Temporary measures include warming and medical measures; leeching is an option for superficial congestion when re‑anastomosis is not possible (Jabbour & Song, Ch.32). - Arterial thrombosis: immediate re‑exploration, thrombectomy, revision and consideration of arterial graft (DIEA interposition graft described for salvage) (Jabbour & Song, Ch.32). ## Key Clinical Pearls - Always explore the inferior incision first and confirm both SIEA pulse and adequate SIEV/venae comitans before committing to an SIEA flap (palpable arterial pulse at incision = good predictor of usable pedicle) (Jabbour & Song, Ch.32). - Make the lower incision as low as feasible (just above pubic hairline) to increase chance of encountering larger SIEA/SIEV and to obtain the best donor scar (Lee & Paek, Ch.23). - Expect a shorter, more lateral pedicle than DIEP—maximize recipient vessel length (clear intercostal spaces from inferior edge of second rib to superior edge of fourth rib yields ~4 cm of internal mammary length) to facilitate anastomosis (Jabbour & Song, Ch.32). - Venous drainage is most frequently limiting—identify and dissect SIEV/SCIV/venae comitans; plan for single or multiple venous anastomoses as anatomy dictates (Jabbour & Song, Ch.32). - If arterial size mismatch encountered, spatulate at a branch point or perform an antimesenteric back-cut on the SIEA; preserve side branches clipped long for this purpose (Jabbour & Song, Ch.32). - Preserve DIEA perforators and/or leave option to convert to DIEP/MS-TRAM if SIEA anatomy proves inadequate intraoperatively (Lee & Paek, Ch.23). - For salvage of arterial thrombosis or short/fragile SIEA pedicle, consider interposition grafting using the deep inferior epigastric artery segment to increase length and correct size mismatch (described salvage technique) (Jabbour & Song, Ch.32).