What Is Obstructed Defecation?

Obstructed defecation syndrome

Obstructed defecation syndrome (ODS) is a syndrome in which those affected have difficulty evacuating faecal matter from the rectum, which results in constipation. ODS is an umbrella term describing conditions involving constipation,¹ its prevalence varies from 2% to 27% of the population in the US.²  ODS is often referred to as an ‘iceberg syndrome’ as those suffering from it most likely suffer from other disorders, for example, 90% of ODS patients also have rectocele and internal rectal prolapse.¹⁴ Constipation disorders are much more common in the geriatric population, approximately 50%. It is more prevalent in people assigned female at birth (people AFAB) studies have shown that it affects approximately 23% of people AFAB.¹²

Symptoms

The symptoms of ODS include difficulty in initiating bowel movements, frequent visits to the toilet due to the feeling of unsuccessful or incomplete bowel evacuation, prolonged or excessive straining during defecation, anal pain, and pelvic pain.¹ Patients may also need to press the perineum or insert a finger into the vagina or anus to pass stool. During normal defecation, the pelvic muscles and anal sphincter will relax to allow the movement of faeces. In contrast, with ODS, failure to relax these muscles is a distinctive characteristic of the disorder. Due to the broad definition of ODS, the symptoms will often overlap with other constipation-related disorders, like slow transit constipation and faecal incontinence. The clinical symptoms of ODS are also present in other conditions like rectocele and rectal prolapse, therefore it is thought that the cause of constipation and ODS lies within these pre-existing conditions.¹ 

Causes

The cause of ODS lies in the dyssynergia in the anal and rectal muscles, the lack of coordination between the muscles when trying to pass stool causes constipation. The causes of ODS can be split into two categories: functional and mechanical causes. Functional causes may include megarectum, anismus, descending perineum syndrome and solitary rectal ulcers. Megarectum is where the rectum is enlarged up to 6 cm, this can cause abnormal motor function of the rectum. Anismus, or spastic pelvic floor and pelvic floor dyssynergia is where the anal sphincter and puborectalis muscle malfunction during defecation.³ Descending perineum syndrome is caused by excessive straining and weakened perineal muscles. Mechanical causes of ODS come from anatomical abnormalities, this includes perineal hernia, rectal prolapse and rectocele. A perineal hernia is when the organs in the pelvis protrude through the pelvic floor, similarly, a rectal prolapse is where the rectal wall partially or fully protrudes through the anal sphincter. Rectocele occurs when the fibrous tissue separating the vagina and rectum is weakened, this allows herniation of the rectum into to vagina, creating a pocket in the rectum where stool can get trapped. Rectocele is more common in people with AFAB as it can be caused by vaginal childbirth.³

Diagnosis

Diagnosis of ODS will start with an evaluation of medical history and examination by a healthcare professional, as underlying pathophysiology may lie in neurological or endocrine disorders. ¹ Imaging studies provide visualisation for possible anatomical causes of ODS, for example, an endoanal ultrasound can check for problems in the anal sphincter, and anorectal ultrasonography can be used to diagnose enterocele or rectocele. Defecating proctography uses X-rays to examine the lower bowel and rectum, this can assess for enterocele and rectocele. CT colonoscopies can be used to examine colon health and fluoroscopic defecography is used to study the rectal emptying process and can be used to diagnose anismus and rectocele. Further tests may be conducted, this includes blood tests for comorbidities that may underpin the aetiology, and anorectal manometry which measures the functionality of bowel muscles and deciphers between anismus and anal sphincter abnormalities.¹

Treatment and prevention

Treatment of ODS can be categorised into conservative management of ODS and surgical intervention. Conservative, non-surgical intervention is typically the first step in treatment and prevention, this includes lifestyle changes, medication, pelvic floor exercises and biofeedback therapy. When all other treatment fails, or when the cause of ODS is a major anatomical abnormality, surgery is considered.  

Lifestyle changes 

Making lifestyle changes is an easy way to treat and, most importantly, prevent ODS. Physical exercise increases bowel functions which can help with active constipation and also reduce the risk of becoming constipated. Maintaining a balanced diet is important to prevent ODS, increasing your daily intake of fibre and fluids will result in still becoming more soft and easier to pass. This means drinking at least 8 glasses of water a day and consuming fibre-rich food like fruit, vegetables, nuts, and wholemeal bread. Dietary fibre supplements can also be taken to increase daily intake. It is important to introduce increasing amounts of fibre slowly into your diet as sudden increases can cause stomach pains, bloating and a build-up of wind. Also, consuming more fibre without enough fluids can cause further constipation. When going to the toilet, it may be useful to use a footstool, this helps open up the anorectal angle and relaxes the puborectalis muscle. Changing your positioning on the toilet can make the bowel movement process easier and less painful.¹ Patients can also perform enemas and colonic irrigation at home to accelerate the evacuation process. 

Pelvic floor exercises and biofeedback therapy

Pelvic floor exercises can relax the pelvic muscles to ease pelvic pain and allow easy bowel evacuation. Belly breathing is a technique that can relax the pelvic floor, this involves inhaling to expand the stomach fully and expelling air in a slow and controlled manner. Massaging the perineal, the area between the scrotum and anus or vagina and anus can facilitate muscle relaxation. Biofeedback therapy is frequently used as first-line therapy with pelvic floor therapy to treat ODS, especially for those who experience constipation caused by anismus or pelvic floor dyssynergia. This method uses anorectal manometry to recognise and correct patterns of pelvic muscular activity.⁴ Biofeedback training has been reported to have a 70-78% success rate in treating constipation,⁵ with a reported reduction in straining, feeling of incomplete evacuation and abdominal pain.⁶

Medications

If lifestyle changes and the use of biofeedback therapy proves ineffective, patients may consider botulinum toxin injections into the puborectalis and anal sphincter, this causes muscle paralysis in order to regain pelvic muscle synergy. Studies show that botulinum toxin injections are effective, however, the benefits are only short-term, and there is a lack of data to support its long-term effects. Drugs like stool softeners and laxatives may be prescribed to stimulate the bowel wall and allow easy passing of stool. ⁷ Laxatives like prucalopride have been clinically proven to be extremely effective in severe constipation.¹³ 

Surgical intervention 

If all previously mentioned treatments fail, surgical intervention may be recommended to treat ODS. It is important to understand that surgery is recommended as a last resort treatment option, only for ODS patients with major anatomic abnormalities as a cause. In the case of megarectum as the causal factor, surgical intervention in the form of anorectal myectomy or the Duhamel procedure may be required.⁸ A ventral rectopexy for rectal prolapse can return the rectum to its normal state, the first study documenting the use of rectopexy for ODS revealed an 84% success rate in resolving symptoms,8 Additionally, a meta-analysis of the effects of rectopexy concludes that the procedure provides significant improvement of symptoms for at least 1 year post-op.9 In the case of rectocele and rectal prolapse, stapled transanal rectal resection (STARR) may be performed to resect portions of the rectal wall to reinforce it. Studies have shown that the STARR procedure on ODS patients significantly provides outstanding short-term improvements.10 However, the efficacy and long-term risks of STARR should be considered, it is reported that 55% of patients 18 months post surgery still experienced at least 3 symptoms of ODS, with 19% of patients requiring further surgical intervention.¹¹ 

Psychological treatment and support groups 

ODS and other related constipation disorders can have a detrimental effect on mental health. Treatment may also include therapy and counselling to support patients suffering from related psychological disorders like anxiety and depression. Support groups are also available through charities and organisations, for example, Guts UK.¹⁵ 

Conclusion 

Obstructed defecation syndrome is a common problem that can significantly affect a patient’s quality of life. It is a broad umbrella term for the symptom of constipation, and therefore, ODS is often associated with other conditions affecting pelvic support and function. Since it affects so many people, timely diagnosis is extremely important. Patients are advised to stay educated on the symptoms of ODS and are encouraged to seek professional help when necessary. Diagnosis is resultant of examination techniques, tests, and imaging studies. If caught early, treatment options include non-invasive routes like lifestyle changes, therapies and medication. There is overwhelming evidence to support the efficacy of biofeedback therapy and pelvic floor exercises. Last resort treatment is often surgery, which has proven to be extremely effective for a short period of time. In most cases, the key to successful treatment of ODS lies in the use of a multidisciplinary approach. The future looks to find effective long-term treatment for ODS patients.