**Region:** Trunk and Lower Back # Omental Flap ## Anatomy - Pedicle: right and left gastroepiploic arteries with accompanying veins (gastroepiploic veins). - Right gastroepiploic artery: terminal branch of gastroduodenal artery (celiac → common hepatic → gastroduodenal → right gastroepiploic). Typical diameter: 2–3 mm; vein typically larger. - Left gastroepiploic artery: branch of the splenic artery. - The omental arcade: connective arterial arcade running transversely approximately 2 cm inferior to the greater curvature of the stomach; gives rise to right, middle, and left omental arteries that descend into the omental apron. - Anastomotic/variation pattern: five anatomic arcade variants described (Type I–V). Reported frequencies: Type I 81.7%, Type II 11.0%, Type III 4.5%, Type IV 1.2%, Type V 1.6% (useful when planning arc-lengthening maneuvers). - Gastroepiploic arcade palpable/located approximately one finger‑breadth parallel to the greater curve (intraoperative tactile landmark). - Nerves: - The greater omentum is nonneurotized for sensate reconstruction; no reliable sensory or motor nerve branches for inclusion. - Included tissues: - Visceral peritoneum, fat, lymphatic tissue (milky spots), connective tissue and macrophage-rich elements. - No skin or muscle is intrinsic to the omentum (skin grafting required for external coverage). - Thickness and bulk highly variable with BMI and prior intra‑abdominal pathology. - Typical harvest dimensions: commonly designed up to 25 × 50 cm (surface area; many patients); reported flap size range 300–1500 cm². - Arc of rotation / reach: - Pedicled flap based on either gastroepiploic artery can reach pelvis and chest depending on mobilization and side chosen. - Detached only from the colon and mobilized, pedicled omentum can reach the nipple in ~75% of cases. - Left-pedicle provides a greater arc of rotation for extended reach; right-pedicle often preferred for pelvic coverage due to orientation/length. - Common variants/anomalies: - Prior omentectomy, short gastric vessel sacrifice, splenectomy, gastrectomy, pancreaticoduodenectomy, or other operations may eliminate or compromise one or both gastroepiploic pedicles. - Omental adhesions and variable fusion to pancreas, transverse colon, or duodenum may limit harvest or increase risk of enterotomy/splenic injury. ## Dissection Steps 1. Positioning, markings, landmarks. - Position: supine for thoracic and most pelvic procedures; lithotomy or supine commonly used during colorectal extirpation (pelvic procedures performed at time of primary extirpation). - Mark midline from subxiphoid region to umbilicus when planning an open upper midline/epigastric incision. - Laparo/robotic: plan ports (typical configurations reported: one 10‑mm periumbilical/infraumbilical camera port plus three 5‑mm lateral ports for conventional laparoscopic harvest; alternative descriptions use one 10‑mm infraumbilical + three 2.5–5 mm working ports—place at right hypochondrium, right iliac fossa and left flank). - Prep abdomen and planned recipient field (thorax/pelvis) in same sterile field. 2. Plane (suprafascial/subfascial), perforator identification (handheld/IO Doppler). - Enter peritoneal cavity via upper midline/epigastric incision or laparoscopic ports. - Identify greater omentum draped over small bowel and attached to transverse colon; elevate omentum off transverse colon through the avascular apposition plane between omentum and transverse mesocolon. - Maintain the avascular plane; avoid full‑thickness defects in thin omentum. - Use transillumination and/or handheld Doppler to assess arcade and distal perfusion intraoperatively as needed. 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - Mobilization: - Reflect omentum cranially and free posterior attachments to transverse colon with countertraction (assistant retracts colon inferiorly while surgeon elevates omentum toward anterior abdominal wall or lesser sac). - Progress toward left upper quadrant cautiously to avoid short gastric vessels, spleen, and pancreatic tail; leave some omentum in LUQ when necessary. - Skeletonization / vessel control: - Choose pedicle (right vs left gastroepiploic) based on required reach and intraoperative assessment. Right is commonly dominant and often preferred for pelvic coverage; left affords greater arc when longer reach is needed. - If basing on right pedicle: ligate and divide left gastroepiploic artery and serial gastric branches along greater curvature; if basing on left pedicle, divide right gastroepiploic as indicated. - Use energy devices (Ligasure/Harmonic) for small branches; when encountering vessels >3 mm, secure with clamp‑and‑tie or hemoclips. Double‑ligate gastroepiploic origin prior to division. - Preserve perivascular tissue; avoid aggressive skeletonization to limit vasospasm. - For additional pedicle length: divide internal gastroepiploic arcades selectively after ensuring distal perfusion (confirm with palpation, Doppler, transillumination, or temporary clamping tests). - Maximal length: - Mobilize safely toward, but stop just short of, the pylorus where the right gastroepiploic contacts the stomach for maximal safe length without compromising gastric perfusion. - Transfer routes: - Pelvis: pass through right or left paracolic gutter following mobilization of white line of Toldt, or pass retrocolic through transverse mesocolon to the right of middle colic artery (repair mesocolonic defect to prevent internal hernia). - Thorax: deliver via transdiaphragmatic incision (cruciate ~4–5 cm reported), extracutaneous/subcutaneous tunnel over costal margin, or through rectus sheath depending on defect location and surgeon preference. Ensure tunnel wide enough to avoid pedicle compression (suggested ≥4 finger breadths). - Inset and fixation: - Let omentum rest dependently with no tension; tacking/stay sutures prevent sliding. - Skin graft externalized omentum when used for external coverage; consider meshed graft. - Perfusion checks: - Handheld Doppler, fluorescein angiography, transillumination; in free flap scenarios standard microvascular checks and implantable Doppler may be used. - If pedicle length inadequate: convert to free flap using recipient vessels in pelvis, thorax or neck as available. 4. Donor-site closure techniques. - Close laparotomy in layers with robust rectus fascia repair. - Place intra‑abdominal drain to detect postoperative hemorrhage; remove when output <30 mL/day for 2 consecutive days. - Close laparoscopic port sites per usual technique. - Consider nasogastric decompression postoperatively (traditional practice to prevent gastric distension and hemoclip dislodgement; in enhanced recovery protocols NG tube is avoided unless indicated). ## Indications and Contraindications - Indications: - Dead‑space obliteration and vascularized filler for pelvic floor defects after abdominoperineal resection or pelvic exenteration. - Thoracic reconstruction: mediastinal pleural defects, sternal osteomyelitis/mediastinitis, bronchopleural fistula, coverage of exposed intrathoracic hardware (eg, grafts, VAD), infected sternal wounds. - Reconstruction where a conformable, immunogenic, lymphatic‑rich tissue is beneficial (radiation injury, infected cavities). - Free omental transfer: soft‑tissue resurfacing of scalp/head–neck, extremities, and lymph node transfer for lymphedema. - Skin graftable surface coverage when bulk and lining are required. - Size limits / bulk considerations: - Bulk variable with BMI; typical harvestable dimensions commonly up to 25 × 50 cm; reported surface area 300–1500 cm². - For large external skin loss, omentum requires skin grafting; if external skin replacement is required primarily, consider musculocutaneous or fasciocutaneous flaps instead of omentum alone. - Contraindications: - Prior omentectomy or surgeries that have sacrificed/compromised gastroepiploic pedicles (eg, gastrectomy, splenectomy, pancreaticoduodenectomy) may preclude harvest. - Dense intra‑abdominal adhesions, active intra‑abdominal infection that distorts omental anatomy (relative contraindication). - Significant abdominal comorbidity that would make laparotomy/laparoscopy high risk (cardiopulmonary instability for CO2 insufflation). - Dirty/infected recipient fields with ongoing uncontrolled sepsis until source control achieved (prepare with debridement/NPWT/antibiotics first). ## Postoperative Care - Monitoring schedule/method: - Pedicled flap: clinical monitoring is difficult because flap is intrathoracic/intrapelvic; use indirect methods—skin graft window and pencil Doppler; transillumination intraop; for free omental flaps standard free flap protocols apply (hourly checks first 24 hours, implantable Doppler when used). - Suggested high‑intensity monitoring window: 24–72 hours postoperative for early vascular events. - Warming and antithrombotic practice: - Standard perioperative DVT prophylaxis for major abdominal and thoracic surgery; no specialized anticoagulation regimen specified for omental flaps beyond routine practice. - Positioning/splinting: - Avoid maneuvers that kink/compress pedicle; ensure tunnels are not under tension or compression. - Drains: - Place intra‑abdominal drain to detect hemorrhage; thoracic/pleural drains as indicated for pleural breaches. - Remove abdominal drain when output <30 mL/day for 2 consecutive days. - Mobilization/diet/analgesia: - Early mobilization recommended (postoperative day 1) unless contraindicated. - Nasogastric tube: traditional practice keeps NG tube for ~2 days after omental mobilization in some series; enhanced recovery protocols favor avoiding NG unless symptomatic. - Gradual diet advancement as tolerated if no ileus. - Return-to-OR thresholds and time windows: - Hemorrhage, increasing drain output, new abdominal distension, hemodynamic instability → return to OR promptly for source control. - For free omental flaps: signs of arterial thrombosis or venous congestion warrant immediate re‑exploration; critical window for salvage is early (first 24–72 hours). - For pedicled flaps with suspected pedicle compression/torsion: consider urgent re‑exploration or release of compression. ## Complications (rates & management) - Flap‑related complications (reported): - Partial flap loss: thoracic series reported 11 of 135 patients = 8.1%. - Total flap loss: 3 of 135 = 2.2%. - Pelvic reconstruction: studies report reduced major pelvic complications when omentoplasty used (example: major pelvic complications 61% without omentum vs 21% with omentum in one series of 70 patients). - Systematic review (14 studies): primary wound healing 66.8% with omentoplasty vs 50.1% without; median time to wound healing 24 days vs 79 days; wound infection 14.4% vs 18.5% (numerical data present in source). - Donor‑site complications (reported): - In 135 patients undergoing omental reconstruction: 25 donor‑site complications = 18.5%. - Laparoscopic harvest series: low major intra‑abdominal complication rate; single‑center laparoscopic series reported conversions for pedicle detachment and one small transdiaphragmatic hernia. - Common complications enumerated in sources: - Bleeding / intra‑abdominal hemorrhage — management: secure ligation of bleeders intraoperatively, low threshold for hemoclips/ties during harvest; postoperative drainage and prompt return to OR for ongoing bleeding. - Splenic injury / pancreatic tail injury — prevention: conservative LUQ dissection; if injured manage per general surgical principles (repair/splenectomy as indicated). - Mesocolon injury / middle colic vessel injury — prevention: awareness of middle colic course; repair mesocolonic defects to prevent internal hernia. - Gastric wall injury / clip dislodgement — prevention: careful use of thermal devices near gastric wall; double‑ligate gastroepiploic and short gastric stumps; consider NG decompression to prevent clip dislodgement from gastric distension. - Paralytic ileus, peritonitis, bowel obstruction, enterotomy — prevention: minimal bowel manipulation, meticulous adhesiolysis; repair enterotomies promptly. - Hernia / fascial dehiscence at donor site — robust fascial closure; recognize late hernias as possible complication. - Seroma / transudation under skin grafted omentum — expected; manage with drains and timely dressing removal; meshed graft recommended for external coverage. - Management algorithms (what, when, how): - Hemorrhage: detect via drain output/clinical instability → return to OR for exploration and hemostasis. - Suspected flap vascular compromise: - Free flap: immediate re‑exploration and microvascular salvage within the earliest possible window (standard microvascular protocols apply). - Pedicled flap: assess for pedicle compression or kinking along tunnel; release compression (widen tunnel/untwist) or re‑position; convert to free transfer if pedicle is not adequate or is avulsed. - Distal perfusion after arc‑lengthening: confirm perfusion intraoperatively (Doppler/transillumination/temporary clamping) before committing to division of arcades. - Prevent internal hernia: repair mesocolonic defects created by retrocolic passage. - Persistent seroma/transudate under graft: drainage and wound care; meshing of skin graft to allow egress. ## Key Clinical Pearls - The omentum is Mathes & Nahai type III: two dominant pedicles (right and left gastroepiploic) with internal omental arcade — plan pedicle side by intended reach and prior abdominal operations. - Right gastroepiploic artery typically 2–3 mm; preserve perivascular tissue and avoid over‑skeletonization to reduce vasospasm and preserve vein. - Omental arcade lies ~2 cm inferior to greater curve; gastroepiploic arcade palpable ~one fingerbreadth parallel to greater curve — use these landmarks when ligating gastric branches. - When lengthening the arc, divide internal arcades only after intraoperative confirmation of distal perfusion (handheld Doppler, transillumination, temporary clamping). - Protect LUQ structures: mobilize conservatively near short gastrics, spleen, and pancreatic tail to avoid splenic or pancreatic injury. - Tunnel planning: make transposition tunnels wide (recommendation ≥4 finger breadths) and avoid sharp angulation; for transdiaphragmatic passage use a cruciate incision ≈4–5 cm to reduce compression risk. - Hemostasis: energy devices are efficient for small omental branches, but ligate or clip vessels >3 mm and double‑ligate primary pedicle trunks to prevent delayed catastrophic bleeding. - Inset and fixation: multiple tacking sutures prevent flap sliding; skin graft a superficialized omentum with meshed graft to allow transudate egress and facilitate monitoring (skin‑graft window facilitates bedside Doppler checks). - Consider laparoscopic harvest for reduced postoperative pain, shorter bed rest, and lower wound morbidity when surgeon experience and patient condition permit. - Expect variability in bulk — always assess intraoperatively and consent patients for alternative flaps (thigh/gluteal/abdominal wall) preoperatively because suitability often determined after abdominal entry.