Obstructed defecation

Section: Colorectal Sub-section: Proctology Curriculum: Curriculum, page 25

Definition

Obstructed defecation syndrome is a type of constipation characterized by fragmented stools, need for straining at defecation, sense of incomplete evacuation, tenesmus, urgency, pelvic heaviness and self-digitation

In a patient presenting with difficult defecating pelvic flood disorders i.e ODS can be a cause.

Constipation causes:

1. Normal transit constipation i.e Functional Constipation
2. Slow transit constipation - see Constipation
3. Outlet delay constipation - see Obstructed defecation
   • This can be divided into anatomical and functional
4. Irritable bowel syndrome
5. Secondary constipation
   • Medications - opiates, anticholinergics, antihypertensives, iron supplements, antacids and non-steroidal anti-inflammatory drugs
   • Neurological disease - Hirschsprung’s disease, multiple sclerosis, Parkinson’s disease and diabetic autonomic neuropathy
   • Electrolytes - hypercalcaemia and hypokalaemia
   • Hormonal - hypothyroidism

 ROME IV

Functional defecation disorders

1. The patient must satisfy diagnostic criteria for Constipation and/or Irritable bowel syndrome with constipation
2. During repeated attempts to defecate, there must be features of impaired evacuation, as demonstrated by 2 of the following 3 tests:
   1. Abnormal balloon expulsion test
   2. Abnormal anorectal evacuation pattern with manometry or anal surface EMG
   3. Impaired rectal evacuation by imaging

Inadequate Defecatory Propulsion

• Inadequate propulsive forces as measured with manometry with or without inappropriate contraction of the anal sphincter and/or pelvic floor muscles

Dyssynergic Defecation

• Inappropriate contraction of the pelvic floor as measured with anal surface EMG or manometry with adequate propulsive forces during attempted defecation

Aetiology

Causes of ODS are:

• Structural
  • Rectocele
  • Intussusception
  • Enterocele
  • Perineal descent
  • Rectal prolapse
• Functional
  • Pelvic floor dyssynergia
  • Poor propulsion
• Or combination of both

Clinical

History

What happens when they get to toilet?

• Slow passage of hard stool – likely SLOW TRANSIT
• Start to evacuate and then abrupt stop – likely RECTOCELE / INTUSSUSCEPTION
• Unable to evacuate despite straining – possible ANORECTAL DYSYNEGIA (Anismus)

Obstructive Defecation Syndrome Score (ODS-S)

Symptoms/variables	0	1	2	3	4
Excessive straining	Never	Rarely	Sometimes	Usually	Always
Incomplete rectal evacuation	Never	Rarely	Sometimes	Usually	Always
Use of enema/laxative	Never	Rarely	Sometimes	Usually	Always
Vaginal/perineal digital pressure	Never	Rarely	Sometimes	Usually	Always
Abdominal discomfort/pain	Never	Rarely	Sometimes	Usually	Always
A score of ≥9 suggests a diagnosis of ODS

(Renzi et al.) (https://link.springer.com/article/10.1007/s00192-022-05114-8#ref-CR10 “Renzi A, Brillantino A, di Sarno G, D’Aniello F. Five-item score for obstructed defecation syndrome: study of validation. Surg Innov. 2013;20(2):119–25.”)]

Investigations

Investigation	Role	Advantages	Disadvantages
Colonic Transit Studies	To distinguish between slow transit constipation and evacuatory difficulties	Easily accessible, simple investigation	Crude investigation which may not appreciate patients with mixed pathology
Anorectal Physiology
Anorectal Manometry	To assess the function of the anal sphincters	Highlights concurrent anal sphincter weakness which should be addressed prior to surgical interventions	Requires specialist equipment and training Results may not correlate with symptoms
Rectal Balloon studies	To assess dyssynergy and rectal compliance and sensitivity	Highlights concurrent rectal hyposensitivity	Results may not influence treatments
Imaging
Endoanal Ultrasound	Assess the structure of the anal sphincter	Assess the integrity of the anal sphincter and examine for concurrent obstetric anal sphincter injury, sepsis and fistula	Requires specialist equipment and training
Integrated Total Pelvic Floor Ultrasound	Dynamic visualisation of entire pelvic floor as an alternative to defaecatory imaging	Dynamic visualisation of anatomical changes and changes to the anorectal angle Simple to perform, cheap, safe, portable, well tolerated by patients compared to proctography. Can be performed in a one stop clinic with simultaneous endoanal assessment of anal sphincter integrity	Does not observe defaecatory dynamics. User dependent
Defaecation Proctography	Dynamic assessment of anatomical and functional aspects	Dynamic visualisation of anatomical changes and rectal emptying. Performed in the upright physiological position	Multicompartmental visualisation is invasive. May overestimate pathology There is debate regarding normal parameters. Radiation exposure
MRI	Defaecation MRI - dynamic assessment of anatomical and functional aspects Dynamic MRI – Dynamic assessment of anatomical aspects	Multicompartmental assessment No radiation	Posterior pathology underestimated without rectal evacuation Anterior pathology underestimated in the supine position Limited access to open configuration systems

Pelvic dyssynergy

The measurement of rectal and anal pressures during balloon expulsion can be used to evaluate dyssynergy.

• Type I – adequate increased rectal pressure with paradoxical rise in anal pressure
• Type II – inadequate increase in rectal pressure with paradoxical rise in anal pressure
• Type III – adequate increased rectal pressure with failure of reduction in anal pressure
• Type IV – inadequate increase in rectal pressure with failure of reduction in anal pressure

Proctography

• Dynamic investigation of rectal emptying
• Allows the visualisation of:
  • Anatomical abnormalities (namely rectocele, intussusception, rectal prolapse, enterocoele, sigmoidocele and perineal descent)
  • Functional problems (changes in the anorectal angle, the extent and duration of rectal emptying and ‘trapping’ of stool within a rectocele)

Causes and treatment

Rectocele

• Hernia of anterior rectal wall bulging into the rectovaginal septum.
• Posterior rare (due to trauma or surgical intervention breaching anococcygeal ligament) Causes:
• Muscular/nerve damage during vaginal delivery
• Hormonal changes during menopause
• Paradoxical contraction of puborectalis.
• Previous vaginal repair Treatment:
• Dietary modification, the use of laxatives, suppositories, adjuncts such as rectal irrigation and biofeedback training
• Surgical: transanal, perineal, transvaginal, abdominal – incl. lap ventral rectopexy

Enterocele

• Peritoneum of pouch of Douglas may herniate – marker of global pelvic floor weakness
• Symptoms are vague and non-specific
• The relevance of an enterocoele is controversial as an enterocoele, which descends onto the rectum during defaecation proctography does not necessarily impede evacuation.

Rectal intussusception:

• Invagination of rectal wall during defaecation.
• Classification according to Oxford Radiological Grading System:
  • Grade I-II: recto-rectal intussusception
  • Grade III-IV: recto-anal intussusception
  • Grade V: high take-off external rectal prolapse

• Half of patients with intussusception suffer with incontinence. 
  • The reasons behind this are not clear but it may be due to the infolding rectal folds leading to rectal distention, the associated chronic straining causing pudendal neuropathy, inflammation from a solitary rectal ulcer causing urgency or prolapsing rectal mucosa opening the anal canal.

Treatment:

• Dietary modification, the use of laxatives, suppositories, adjuncts such as rectal irrigation and biofeedback training
• Surgical: transanal, perineal, transvaginal, abdominal – incl. lap ventral rectopexy

Solitary rectal ulcer syndrome

• Caused by paradoxical contraction of anal sphincter muscle during defaecation.
• Associated with anal digitation, results in anterior mucosal trauma and ulceration.
• Treatment: dietary changes, bulking agents and biofeedback.
• Surgery rarely indicated, only for concomitant prolapse or refractory symptoms.