Altered anal slow-wave pressure activity in low anterior resection syndrome: short case series in two independent specialist centres provide new mechanistic insights

Characterization of Anal Slow Waves and Ultraslow Waves in Patients With Constipation and Healthy Subjects

BACKGROUND

Anal slow waves (SW) and ultraslow waves (USW) have been documented previously, yet their significance remains uncertain. Our aims were to characterize the prevalence and features of SW and USW in healthy subjects and patients with constipation and to correlate them with clinical features and anorectal physiological testing.

METHODS

Forty-three healthy female subjects and 83 female tertiary referral patients with constipation were included. High-resolution water-perfused manometry was performed. Retrospective blinded descriptive and quantitative analyses of manometric tracings were completed with a focus on SW and USW.

KEY RESULTS

SW were present in 58% of healthy subjects and 62% of constipated patients (p = 0.72) yet USW were seen almost exclusively in constipated patients (27% vs. 2% health; p < 0.0001). Frequencies and mean amplitudes of SW and USW were similar in both groups. Anal resting and squeeze pressures were higher in patients with SW compared to those without (p < 0.001, p = 0.004, respectively). Patients with USW had higher anal resting pressure and shorter duration of sustained squeeze compared to those without (p < 0.001 for both). There was a trend for less obstetric injury in constipated patients with USW compared to those without (23% vs. 48%; p = 0.05).

CONCLUSIONS AND INTERFERENCES

While SW were common in both constipated and healthy subjects, USW were almost exclusively observed in constipated patients. Some correlations were observed with other anorectal physiology parameters such as high resting anal pressure with both SW and USW. Formal definitions for SW and USW are proposed. Further research into the clinical significance of these waves is warranted.

Preventative strategies for low anterior resection syndrome

BACKGROUND

A common and debilitating complication of low anterior resection for rectal cancer is low anterior resection syndrome (LARS). As a multifactorial entity, LARS is poorly understood and challenging to treat. Despite this, prevention strategies are commonly overlooked. Our aim was to review the pathophysiology of LARS and explore current evidence on the efficacy and feasibility of prophylactic techniques.

METHODS

A literature review was performed between [1st January 2000 to 1st October 2023] for studies which investigated preventative interventions for LARS. Mechanisms by which LARS develop are described, followed by a review of prophylactic strategies to prevent LARS. Medline, Cochrane, and PubMed databases were searched, 189 articles screened, 8 duplicates removed and 18 studies reviewed.

RESULTS

Colonic dysmotility, anal sphincter dysfunction and neorectal dysfunction all contribute to the development of LARS, with the complex mechanism of defecation interrupted by surgery. Transanal irrigation (TAI) and pelvic floor rehabilitation (PFR) have shown benefits in preventing LARS, but may be limited by patient compliance. Intraoperative nerve monitoring (IONM) and robotic-assisted surgery have shown some promise in surgically preventing LARS. Nerve stimulation and other novel strategies currently used in treatment of LARS have yet to be investigated in their roles prophylactically.

CONCLUSIONS

To date, there is a limited evidence base for all preventative strategies including IONM, RAS, PFP and TAI. These strategies are limited by either access (IONM, RAS and PFP) or acceptability (PFP and TAI), which are both key to the success of any intervention. The results of ongoing trials will serve to assess acceptability, while technological advancement may improve access to some of the aforementioned strategies.

The risk factors of low anterior resection syndrome after colorectal cancer surgery: A retrospective study of 566 patients in a single institution in China

PURPOSE

This study aims to identify the independent risk factors in the low anterior resection syndrome (LARS) after surgery for colorectal cancer (CRC).

METHOD

This was a retrospective, single-institution study in the Second Affiliation Hospital of Dalian Medical University, China. Patients underwent sphincter-preserving low anterior resection with total or partial mesorectal resection (with or without protective ileostomy) and completed a self-filled questionnaire over the phone to assess postoperative bowel dysfunction from January 2017 to December 2019. The predictors of LAR were evaluated using univariate and multivariate analyses.

RESULT

The study population was 566 patients, 264 (46.64%), 224 (39.58%), and 78 (13.78%) patients with no, minor, and major LARS, respectively. In the univariate analysis, independent factors such as tumor location and size, anastomotic height, protective ileostomy, post-operation chemoradiotherapy, tumor T stage, lymphatic nodal metastasis classification, surgery duration, and time interval for closure of stoma were significantly associated with LARS points while we found the tumor T stage and lymphatic nodal metastasis classification as the new independent risk factors compared with the last decade studies. In the multivariate analysis, factors such as low and middle tumor location and protective ileostomy, and post operation treatment, nodal metastasis classification were the independent risk factors for major LARS.

CONCLUSION

The new independence risk factors were tumor T stage and lymphatic nodal metastasis status in univariate analysis in our study, with anastomotic height, low and middle tumor location, protective ileostomy, post-operation chemoradiotherapy, nodal metastasis status increasing LARS point in multivariate analysis after surgery for CRC.

Faecal incontinence in adults

Faecal incontinence, which is defined by the unintentional loss of solid or liquid stool, has a worldwide prevalence of ≤7% in community-dwelling adults and can markedly impair quality of life. Nonetheless, many patients might not volunteer the symptom owing to embarrassment. Bowel disturbances, particularly diarrhoea, anal sphincter trauma (obstetrical injury or previous surgery), rectal urgency and burden of chronic illness are the main risk factors for faecal incontinence; others include neurological disorders, inflammatory bowel disease and pelvic floor anatomical disturbances. Faecal incontinence is classified by its type (urge, passive or combined), aetiology (anorectal disturbance, bowel symptoms or both) and severity, which is derived from the frequency, volume, consistency and nature (urge or passive) of stool leakage. Guided by the clinical features, diagnostic tests and therapies are implemented stepwise. When simple measures (for example, bowel modifiers such as fibre supplements, laxatives and anti-diarrhoeal agents) fail, anorectal manometry and other tests (endoanal imaging, defecography, rectal compliance and sensation, and anal neurophysiological tests) are performed as necessary. Non-surgical options (diet and lifestyle modification, behavioural measures, including biofeedback therapy, pharmacotherapy for constipation or diarrhoea, and anal or vaginal barrier devices) are often effective, especially in patients with mild faecal incontinence. Thereafter, perianal bulking agents, sacral neuromodulation and other surgeries may be considered when necessary.

Improvement of low anterior resection syndrome beyond 2 years after total mesorectal excision

AIM

Bowel dysfunction after sphincter-preserving proctectomy, also known as low anterior resection syndrome (LARS), has significant impact on survivors of rectal cancer. This study aimed to assess the temporal change of LARS beyond 2 years after proctectomy, which has not been fully studied.

METHODS

We longitudinally enrolled consecutive patients who had received total mesorectal excision in a tertiary academic medical center, with preoperative neoadjuvant therapy if indicated. LARS score was longitudinally assessed by two serial follow-ups, with a fixed interval of 18 months.

RESULTS

Overall, 107 patients responded for the first follow-up after a median of q20 months, 96 of whom responded for the second follow-up after a median of 38 months. At the first follow-up, 48 patients (44.9%) reported major LARS, compared with 23 (24.0%) at the second follow-up (p < 0.001). Mean LARS score improved from 27.3 to 18.6, mostly from "urgency" (12.2 vs. 6.2, p < 0.001) and "clustering of stools" (9.7 vs. 7.7, p = 0.001). Anastomosis less than 3 cm from the anal verge was independently associated with LARS improvement.

CONCLUSION

Bowel dysfunction continues to improve 2 years after total mesorectal excision, with most symptom relief in urgency and stool clustering, especially in patients with lower anastomosis.