Assessment and Management of Low Anterior Resection Syndrome After Sphincter-Preserving Surgery for Rectal Cancer

Assessment and Management of Low Anterior Resection Syndrome After Sphincter-Preserving Surgery for Rectal Cancer

Colorectal cancer is the third most commonly diagnosed cancer globally. Over the past two decades, significant advancements in the staging and treatment of rectal cancer, particularly the use of preoperative neoadjuvant chemoradiotherapy, have improved survival rates and reduced local recurrence rates. A notable shift in the treatment paradigm for low rectal cancer has been the move from abdominoperineal resection (APR) to sphincter-preserving surgeries (SPS). This shift has been facilitated by advances in surgical techniques, including minimally invasive surgery and preoperative chemoradiotherapy. The indications for SPS have expanded to include very low-lying tumors located within 1 to 3 cm from the anal verge. Techniques such as ultralow anterior resection (ULAR) with coloanal anastomosis and intersphincteric resection (ISR) have been employed with acceptable oncologic outcomes.

Despite these advancements, many patients experience postoperative bowel dysfunction, commonly referred to as low anterior resection syndrome (LARS). LARS encompasses symptoms such as increased stool frequency, urgency, evacuation difficulties, and varying degrees of fecal incontinence (FI), all of which negatively impact patients’ quality of life (QoL). The incidence of LARS varies in the literature, with some studies reporting rates between 19% and 52%. A recent meta-analysis estimated the prevalence of LARS at 41%.

The pathophysiology of LARS is multifactorial, involving colonic dysmotility, neorectal reservoir dysfunction, and anal sphincter dysfunction. Colonic dysmotility results from increased proximal colonic motility due to denervation of the sigmoid or descending colon during surgery, coupled with a lack of distal rectal inhibition. This leads to shorter colonic transit times and increased neorectal pressure postprandially. Neorectal reservoir dysfunction arises from denervation and reduced functional capacity of the neorectum, often due to surgery or pelvic radiotherapy. This results in hypersensitivity to mechanical and thermal stimuli, causing symptoms like urgency and multiple evacuations. Anal sphincter dysfunction can occur as a complication of rectal surgery or preoperative pelvic radiotherapy, leading to internal anal sphincter (IAS) injury and reduced anal resting and squeeze pressures.

Several risk factors for LARS have been identified, including low colorectal or coloanal anastomosis, end-to-end anastomosis, anastomotic leakage (AL), adjuvant radiotherapy, female sex, presence of a stoma, and postoperative complications. Other factors such as old age, male sex, adjuvant chemoradiation therapy, and ULAR have also been associated with increased risk. Neoadjuvant chemoradiotherapy, low rectal resection, and tumor distance from the anal verge are significant predictors of long-term bowel dysfunction.

The diagnosis of LARS involves a comprehensive assessment, including detailed history taking, physical examination, and the use of validated questionnaires and diagnostic tools. The most commonly used questionnaires are the Low Anterior Resection Syndrome (LARS) score and the Memorial Sloan-Kettering Cancer Center Bowel Function Instrument (MSKCC BFI). The LARS score, which includes questions on incontinence for flatus and liquid stool, frequency, clustering, and urgency, is particularly useful for rapid screening and assessing the impact on QoL. The MSKCC BFI provides a more detailed evaluation of bowel dysfunction, covering frequency, diet, urgency/soilage, and other aspects.

Diagnostic tools such as endorectal ultrasound (ERUS), anorectal/colonic manometry, and defecography/magnetic resonance (MR) defecography are also employed to assess anorectal function and structural abnormalities. ERUS can visualize defects or scarring in the anal sphincter, while manometry measures resting and squeeze anal pressures and rectal compliance. Defecography can reveal functional disorders such as widened anorectal angles and reduced rectal evacuation.

The management of LARS is tailored to the severity and duration of symptoms. For minor LARS (LARS score <30), medical management is often sufficient. Anti-diarrheal agents like loperamide can reduce stool frequency and improve stool consistency. Serotonin receptor antagonists such as ramosetron can alleviate postprandial urgency and incontinence. Antibiotics like rifaximin or neomycin may be used to treat excessive flatulence or abdominal bloating caused by small intestinal bacterial overgrowth. Anal bulking agents can enhance resting anal pressures and improve fecal continence in patients with passive FI or fecal soilage.

For major LARS (LARS score >30), a multimodal approach is typically required. This includes transanal irrigation (TAI), pelvic floor rehabilitation, and neuromodulation. TAI, which involves the mechanical washout of the rectum, has been shown to improve symptoms in 79% to 100% of patients with LARS. Pelvic floor rehabilitation, including biofeedback, pelvic floor muscle training, electrostimulation, and rectal balloon training, can improve FI scores, number of bowel movements, and anorectal manometry results. Sacral nerve stimulation (SNS) is considered for patients with persistent symptoms after one year of multimodal therapy. SNS has been shown to significantly improve FI episodes and QoL in LARS patients.

In cases where conservative and minimally invasive treatments fail, surgical options such as artificial sphincter implantation or fecal diversion may be considered. Fecal diversion, typically in the form of a permanent stoma, is the last resort for patients with severely compromised QoL and persistent major LARS symptoms.

Prevention of LARS involves meticulous surgical dissection with preservation of nerves, creation of a neorectal reservoir during anastomosis, and proper Kegel exercises for the anal sphincter. Preoperative counseling is essential for patients with risk factors for developing LARS. The Preoperative LARS Score (POLARS) is a nomogram and online tool that can help predict bowel dysfunction severity before surgery, aiding in patient selection and postoperative support planning.

In conclusion, LARS is an inevitable consequence of SPS for rectal cancer. Its management requires a comprehensive approach, including accurate diagnosis, tailored treatment strategies, and preventive measures. The use of validated questionnaires and diagnostic tools is crucial for assessing functional status and guiding treatment. Multimodal therapy, including TAI, pelvic floor rehabilitation, and neuromodulation, is effective for managing major LARS. In refractory cases, surgical options may be necessary. Preoperative counseling and meticulous surgical techniques can minimize the incidence and severity of LARS, ultimately improving patients’ QoL. Future research should focus on prospective longitudinal studies to better understand the functional outcomes after SPS and to develop standardized treatment protocols.

doi.org/10.1097/CM9.0000000000000852

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