30/11/2025
Types of Anterior Resection
The term "anterior resection" (AR) primarily refers to surgical procedures to remove cancer in the upper or middle re**um, aiming to preserve the a**l sphincter and avoid a permanent colostomy. The type is mainly defined by the height of the tumor in the re**um and consequently, how low the anastomosis (reconnection) is performed.
Here are the main types:
1. High Anterior Resection (HAR):
· Tumor Location: Upper re**um (approximately 10-15 cm from the a**l verge).
· Resection: Removes the sigmoid colon and the upper part of the re**um.
· Anastomosis: Performed above the peritoneal reflection (where the re**um transitions from having a covering peritoneum to being extraperitoneal). The anastomosis is typically intraperitoneal, within the abdominal cavity.
· Key Points: Functionally and technically, this can overlap significantly with a sigmoid colectomy for cancer. The anastomosis is generally the most straightforward and has the lowest risk of leak among the AR types. Bowel function afterward is usually close to normal.
2. Low Anterior Resection (LAR):
· Tumor Location: Mid-re**um (approximately 5-10 cm from the a**l verge).
· Resection: Removes the sigmoid colon and most of the re**um, down to the level of or just above the pelvic floor muscles.
· Anastomosis: Performed at or just above the top of the a**l ca**l, below the peritoneal reflection. This is a deep pelvic anastomosis.
· Key Points: This is the most common type referred to as "anterior resection." It requires meticulous pelvic dissection (Total Mesore**al Excision - TME is standard) to remove the cancer and surrounding lymph nodes. A temporary loop ileostomy is often created to protect the low anastomosis due to a higher risk of leak. Bowel function afterward may be altered (see LARS below).
3. Ultra-Low Anterior Resection (ULAR) / Coloa**l Anastomosis (CAA):
· Tumor Location: Very low re**um (within 5 cm of the a**l verge, but above the sphincter complex).
· Resection: Removes the sigmoid colon and nearly the entire re**um, down to the top of the a**l ca**l or just within it.
· Anastomosis: Performed to the top of the a**l ca**l (coloa**l). This may be a straight connection or involve forming a "neore**um" (colonic J-pouch or side-to-end) to improve function. It is performed deep in the pelvis, essentially at the anore**al junction.
· Key Points: This is the most technically challenging AR, performed very close to the sphincters. A temporary loop ileostomy is almost always created due to the very high leak risk. Bowel function afterward is significantly more likely to be altered (Low Anterior Resection Syndrome - LARS is common, involving frequency, urgency, clustering, incontinence).
4. Intersphincteric Resection (ISR): (A Specific Subtype of ULAR/CAA)
· Tumor Location: Extremely low re**al tumors (within 1-3 cm of the a**l verge) that would traditionally require an Abdominoperineal Resection (APR - permanent colostomy) but where the external sphincter and pubore**alis muscle can be preserved.
· Resection: Involves removing the internal a**l sphincter muscle (partially or completely) along with the re**um, either from above (abdominally) or combined with a perineal approach. The external sphincter is preserved.
· Anastomosis: Performed within the a**l ca**l, between the colon and the remaining a**l ca**l/external sphincter complex.
· Key Points: The most sphincter-preserving option for ultra-low cancers, but requires highly specialized surgical skills. Temporary ileostomy is mandatory. Functional outcomes are variable; while the sphincter is preserved, function is often significantly impaired (high risk of LARS, incontinence).
Key Factors Influencing the Type Chosen:
· Distance of the tumor from the a**l verge: Measured by rigid proctoscopy or MRI.
· Relation to the peritoneal reflection: Critical for defining HAR vs LAR/ULAR.
· Stage and characteristics of the tumor: Size, invasion depth, involvement of surrounding structures.
· Patient factors: Body habitus (obesity makes pelvic surgery harder), previous pelvic surgery/radiation, comorbidities, preoperative sphincter function.
· Surgeon's expertise and judgment.
· Goal of sphincter preservation: Balancing oncological safety with functional outcome.
Important Considerations:
· TME (Total Mesore**al Excision): This is the standard oncological technique for removing the re**um and its surrounding fatty tissue (mesore**um) containing lymph nodes, applied in LAR, ULAR, and ISR.
· Temporary Ostomy: Often used in LAR and almost always in ULAR/ISR to divert stool away from the low anastomosis while it heals, reducing the severity of consequences if a leak occurs.
· Functional Outcome (LARS): The lower the anastomosis, the higher the risk of Low Anterior Resection Syndrome, involving bowel dysfunction like frequency, urgency, incontinence, and incomplete emptying.
· Anastomotic Leak Risk: Risk increases significantly the lower the anastomosis is performed (HAR < LAR < ULAR/ISR).
The choice between these types is a complex decision made by the colore**al surgeon based on careful preoperative staging and assessment, aiming for the best cancer outcome while preserving sphincter function and quality of life where possible.
