Low Anterior Resection (LAR) is a major abdominal operation performed on the rectum, the final section of the large intestine. The procedure involves surgically removing the diseased portion of the rectum and then reconnecting the remaining bowel segments. This operation aims to eliminate disease while preserving the natural function of the lower digestive tract. The primary goal of a successful LAR is to allow the patient to maintain bowel movements through the anus without the need for a permanent external pouch.
The Purpose and Candidates for Low Anterior Resection
LAR is the standard surgical treatment for most cancers located in the middle and upper third of the rectum. The specific location of the tumor determines whether this operation is feasible, as it requires enough healthy tissue to remain for a successful reconnection. While rectal cancer is the most common indication, LAR may also treat severe, complicated cases of inflammatory bowel disease or chronic diverticulitis that have damaged the lower rectum.
The distinction of LAR compared to other rectal surgeries is its ability to spare the anal sphincter muscles. By leaving these muscles intact, the surgeon can rejoin the colon to the remaining rectal stump or directly to the anus in an anastomosis. This preservation of the sphincter mechanism allows the patient to avoid a permanent colostomy. Candidates for LAR must generally have a tumor positioned high enough within the rectum, typically above the anal verge, to ensure a sufficient margin of healthy tissue is removed while maintaining sphincter function.
Detailing the Surgical Procedure
The Low Anterior Resection procedure follows three steps: resection, mobilization, and anastomosis. During the resection phase, the surgeon removes the diseased segment of the rectum along with the surrounding tissue known as the mesorectum. The mesorectum contains lymph nodes that must also be removed for complete cancer staging, often using Total Mesorectal Excision (TME) to minimize local recurrence.
Following removal, the surgeon mobilizes the remaining colon, freeing it from its attachments so it can be brought down into the pelvis. This allows for the anastomosis, where the healthy end of the colon is stapled or sutured to the remaining portion of the rectum or anus. This surgical connection must be tension-free and well-supplied with blood to ensure proper healing.
The procedure is commonly performed using open surgery, which requires a single, large abdominal incision. Minimally invasive techniques are increasingly favored, such as Laparoscopic LAR, which involves several small incisions for a camera and specialized instruments. Robotic-assisted LAR offers enhanced precision within the pelvis, providing the surgeon with a three-dimensional view and instruments with greater range of motion, which aids in nerve preservation.
To protect the newly created anastomosis while it heals, a temporary diverting stoma is often created. This involves bringing a loop of the small intestine, typically the ileum, through a small opening in the abdominal wall to divert the fecal stream. This temporary ileostomy is generally reversed in a subsequent, less-invasive procedure once the main connection is completely healed.
Immediate Post-Operative Recovery and Monitoring
The initial recovery period typically lasts five to seven days in the hospital. Pain management is a priority, often involving regional anesthesia, such as an epidural, in the first few days. Early mobilization is encouraged, with patients walking within 24 hours to promote circulation and accelerate the return of bowel function.
Monitoring for an anastomotic leak is a primary concern in the first post-operative week, as this complication occurs when the connection site fails to heal. The care team closely monitors vital signs for indicators like fever, elevated heart rate, or unexplained abdominal pain. Patients begin a diet progression, starting with clear liquids and advancing to low-fiber solid foods as bowel function returns.
If a temporary ileostomy was created, patient education on its care begins immediately, often assisted by an enterostomal therapy nurse. Patients learn how to manage the appliance, monitor the stoma’s appearance, and track output volume and consistency. High output from the stoma requires careful management to prevent dehydration and electrolyte imbalance, often needing specific dietary adjustments and anti-diarrheal medications.
Long-Term Outlook and Functional Recovery
The first long-term milestone following LAR is the reversal of the temporary ileostomy, typically occurring eight to twelve weeks after the initial surgery. This procedure is generally less complex and allows the fecal stream to resume its normal path through the healed anastomosis and remaining rectum. Once the stoma is reversed, many patients experience changes in bowel habits known as Low Anterior Resection Syndrome (LARS).
LARS is a common collection of symptoms resulting from the loss of the rectum’s function as a stool reservoir. Symptoms include increased bowel frequency, urgency, and a feeling of incomplete emptying. LARS severity varies, but management often involves dietary modifications, such as increasing soluble fiber to bulk the stool, and anti-diarrheal medications like loperamide.
Functional recovery is a gradual process that can take many months, with symptoms often improving significantly within the first year after stoma reversal. Patients may benefit from pelvic floor muscle training and biofeedback therapy to strengthen continence muscles. Long-term surveillance is necessary, especially for cancer patients, involving regular follow-up to monitor for recurrence and manage ongoing functional changes.