What is the anatomy and step-by-step procedure of a left extended hemicolectomy?

Anatomy and Stepwise Procedure of Left Extended Hemicolectomy

Anatomical Extent of Resection

Left extended hemicolectomy involves resection from the left transverse colon to the sigmoid colon, including the splenic flexure, descending colon, and proximal sigmoid, with high ligation of the inferior mesenteric artery and removal of the associated mesocolon containing lymphatic channels and nodes. 1, 2

The procedure removes:

• Left transverse colon (typically from the middle colic artery territory) 3
• Splenic flexure with complete mobilization 2, 3
• Entire descending colon 1, 3
• Proximal sigmoid colon (variable extent based on tumor location) 3
• Mesocolon with lymphovascular pedicle including high ligation at the inferior mesenteric artery origin 1, 4

The splenic flexure mobilization is particularly critical because the left colon has more limited mobility compared to the right colon, making proper mobilization techniques essential for tension-free anastomosis. 5 Damage to the marginal artery during mobilization can compromise blood supply to the anastomosis. 5

Preoperative Preparation

• Bowel preparation with hypertonic solution combined with low-residue diet 1
• Intravenous broad-spectrum antibiotic prophylaxis targeting Gram-negative bacilli and anaerobes 1, 2
• Marking of planned stoma sites if applicable 1
• Preoperative imaging (CT scan with simulation CT colonography when available) to identify tumor location, vascular anatomy, and dominant vessels 3

Stepwise Surgical Procedure

Step 1: Incision and Exploration

• Median laparotomy incision is recommended for open approach 1, 2
• Systematic exploration of the liver, pelvis, and ovaries (in women) with sampling or frozen section of suspicious masses 1
• Assessment of tumor resectability and involvement of neighboring organs 1

Step 2: Vascular Control and Mesocolic Excision

• High ligation of the inferior mesenteric artery at its origin from the aorta 1, 4
• Ligation of the inferior mesenteric vein (typically at the inferior border of the pancreas) 3
• Identification and preservation of the left branch of the middle colic artery when possible for transverse colon blood supply 3
• Meticulous mesocolic excision to optimize lymph node yield (minimum adequate nodal evaluation in 58-78% of cases) 2, 6

Step 3: Mobilization of the Colon

• Complete mobilization of the splenic flexure by dividing the splenocolic and phrenocolic ligaments 2, 5
• Mobilization of the descending colon by incising the lateral peritoneal reflection (white line of Toldt) 5
• Mobilization of the proximal sigmoid colon to the level of planned distal resection 3
• Ensure adequate mobility of both proximal and distal bowel segments for tension-free anastomosis 1, 2

Step 4: Resection

• Proximal division at the left transverse colon with safe margins (typically 5-10 cm from tumor depending on vascular anatomy) 3
• Distal division at the sigmoid colon with safe margins 1, 2
• En bloc resection if tumor has invaded neighboring organs 1
• Ensure clear surgical margins (achieved in >98% of cases in experienced hands) 6

Step 5: Anastomosis

In stable patients, primary anastomosis with or without diverting stoma should be performed based on patient stability and anastomotic risk factors. 2

Anastomotic Options:

• Transverse colon to sigmoid/rectum anastomosis (most common) 2, 6
• Side-to-side anastomosis using linear stapler (lower leak rate of 3.1% vs 13.3% for circular stapler in selected cases) 7
• Side-to-end anastomosis (safe alternative with 0% leak rate in elective settings) 7
• End-to-end anastomosis using circular stapler (traditional approach) 7
• "Flip-Flop" technique if transverse colon cannot reach rectum (repositioning right colon to reach rectum after extended left colectomy) 8

Both stapled and hand-sewn techniques yield equivalent results in experienced hands; for manual anastomosis, a one-layer technique is recommended. 1, 2

Critical requirements for effective anastomosis:

• Good bowel preparation 1, 2
• Well-maintained vascular supply to both bowel segments 1, 2
• No undue traction on the anastomosis 1, 2
• Tension-free approximation (proper mobilization is critical) 2, 5

Step 6: Closure

• Inspection for hemostasis 2
• Closure of mesenteric defects if present 2
• Abdominal wall closure in standard fashion 1

Emergency Presentations: Modified Approach

For left-sided obstruction in unstable patients, Hartmann's procedure (resection with end colostomy and rectal stump) should be considered the procedure of choice. 1, 2

Criteria for Unstable Patient (Damage Control Indication):

• pH < 7.2 1, 2
• Core temperature < 35°C 1, 2
• Base excess < -8 1, 2
• Laboratory/clinical evidence of coagulopathy 1, 2
• Any signs of sepsis/septic shock, including necessity of inotropic support 1, 2

Emergency Management Algorithm:

• Stable patients with obstruction: Primary resection with anastomosis 1, 2
• Unstable patients with obstruction: Hartmann's procedure 1, 2
• Severely unstable patients: Loop transverse colostomy only 1, 2
• Left-sided perforation: Hartmann's procedure (primary anastomosis only in stable patients with minimal contamination) 1, 2

Antibiotic Management

• Prophylactic antibiotics targeting Gram-negative bacilli and anaerobes should be discontinued after 24 hours (or 3 doses) in obstruction without systemic infection 1, 2
• Therapeutic antibiotics are always required for perforation, targeting Gram-negative bacilli and anaerobes 1, 2
• Broader-spectrum antimicrobials should be used early in critically ill patients with sepsis 1, 2
• Refine therapy based on microbiological findings and local resistance patterns 1, 2

Laparoscopic Approach

Laparoscopic left hemicolectomy is preferable in experienced centers and fit patients in elective settings. 2

• Limited role in emergency settings or unstable patients 2
• Not recommended except in selected cases in specialist centers for emergency presentations 2
• Simulation CT colonography enables clear identification of tumor position and dominant vessels, facilitating laparoscopic surgery 3

Common Pitfalls and Critical Considerations

• Inadequate splenic flexure mobilization leads to tension on the anastomosis, increasing leak risk 2, 5
• Damage to the marginal artery during mobilization compromises anastomotic blood supply 5
• Insufficient lymph node harvest (aim for adequate nodal evaluation per oncologic principles) 2, 6
• Anastomotic leak is a life-threatening complication with high morbidity and mortality; tension-free, well-vascularized anastomosis is critical 2, 5
• Increased bowel movement frequency occurs after left hemicolectomy, particularly during the first postoperative year 4
• In Lynch syndrome patients, subtotal colectomy with ileorectal anastomosis should be considered due to high risk of metachronous cancer (16-19% at 10 years with partial colectomy vs 3.4% with subtotal colectomy) 1