- Constipation is common, and often easily preventable
- Risk factors include low physical activity, reduced self-reported health, post-op period, diabetes, depression/anxiety, neurological disorders such as Parkinson’s disease, drugs (especially opiates)
- Little evidence for low fibre diet or fluid intake as causative
- Complications include
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- Faecal impaction and rectal distention
- Haemorrhoids, anal fissures
- Faceal incontinence (overflow)
- Obstruction, perforation
- Urinary symptoms (recurrent UTIs, retention and incontinence)
- Rectal prolapse
- Delirium in elderly
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Causes
- Drugs
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- Opiates
- Antidepressants / antipsychotics – especially olanzapine, clozapine, amisulpride, quetiapine, tricyclics
- Supplements – iron, calcium, antacids containing aluminium
- Antimuscarinics – procyclidine, oxybutynin
- Anti-seizure medications
- Antispasmodics eg hyoscine
- Diuretics and calcium channel blockers
- Others – ondansetron, hydroxyzine
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- Endocrine / metabolic
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- Diabetes with autonomic neuropathy
- Hypercalcaemia / hypermagnesemia / hypokalaemia
- Hypothyroidism
- Uraemia
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- Neurological / myotonic
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- Myotonic dystrophy
- Autonomic neuropathy
- Multiple sclerosis
- Parkinson’s disease
- Cord injuries / tumours
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- Structural / anatomical
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- Anal fissures and haemorrhoids
- Strictures
- Inflammatory bowel disease
- Cancer
- Rectal prolapse
- Post-natal pelvic floor damage
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- Functional
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- IBS-related
- Slow transit
- Dyssynergic defecation
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- Other
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- Scleroderma
- Amyloid
- Pregnancy
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Assessment
- Assess for ALARM features
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- Sudden change in bowel habit
- Rectal bleeding / bloody stools
- Unexplained abdominal pain
- Unexplained iron deficient anaemia
- Unexplained weight loss
- Family history of bowel cancer
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- Ask about
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- Lifestyle and medications (especially opioids)
- Frequency of opening bowels
- What their stools look like – Bristol stool chart types 1-7 (1 is hardest)
- Sensation of incomplete evacuation and/or blockage
- Faecal incontinence (can be urge bowel leakage or passive bowel leakage)
- Upper GI symptoms
- Urinary symptoms
- What they’ve tried so far
- Mental health conditions or psychomorbidity
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- Physical exam
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- Check for masses
- Listen for bowel sounds
- PR exam
- Pelvic floor exam if skilled – can check voluntary sphincter squeeze, puborectalis relaxation push, abdominal effort push
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- Investigation
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- Hb, TFTs, HbA1c, calcium
- Consider scopes, AxR, CT
- Specialists may request anorectal manometry, defecation proctography, and colon transit time studies (but exclude structural pathology before physiology testing)
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Chronic constipation
- Defined as 2 or more of the following (each occurring in >25% of defecations)
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- Straining during of defecations
- Lumpy or hard stools
- Sensation of incomplete evacuation
- Sensation of anorectal obstruction / blockage
- Manual manoeuvres required
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- Plus:
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- < 3 bowel motions per week
- And does not fulfil IBS diagnostic criteria (who tend to have more abdominal pain)
- And symptoms for at least the last 3 months, and onset of symptoms > 6 month ago
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- Can be a transit problem, or an evacuation problem, or both (management differs accordingly)
Management of constipation
- Start with addressing diet, medications, mobility and fluid intake (especially in the outpatient setting)
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- Increase oral fluids, exercise
- Fibre – can take several weeks to work (and the type of fibre is important)
- Consider kiwis, rye bread, probiotics
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- Laxatives
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- Most people will prefer oral agents, so generally give in preference to enemas (and do a PR before giving enemas)
- Not much evidence for any laxatives (not much financial incentive to do research)
- You need to allow time for laxatives to work
- Bulk forming laxatives (eg Ispaghula) are 1st line (but avoid in opioid-induced constipation)
- Then trial of macrogol
- Then trial of lactulose
- Then if stools soft but hard to pass – try stimulants
- Can combine types
- Consider naldemedine for opioid induced constipation
- Consider Prucalopride if 2 types of laxatives have failed and symptoms chronic. Trial for 4 weeks
- Wean laxatives over months
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- Also consider
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- Magnesium oxide supplements
- Rectal irrigation
- Dietician review
- Biofeedback training for pelvic floor dyssynergia
- Rarely surgery for slow transmit constipation
- Amitriptyline (low dose) can help in some patients with IBS
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Notes on choice of laxatives
- Bisocodyl
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- Stimulant laxative. Can be very effective (more potent than senna)
- Can be given as suppository or oral
- Best for short term use
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- Senna
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- Stimulant laxative
- Can cause melanosis coli (which is harmless but makes scopes more challenging)
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- Lactulose
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- Osmotic laxative, also used in liver disease
- Can cause bloating (but 15 ml once daily is usually ok)
- Only high doses (or long-term use) tend to impact on diabetes control
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- Laxido / Macrogol / Movicol
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- An osmotic laxative, more effective than lactulose, low cost
- Usually 1st line in hospital
- Often 2 sachets in 250ml of water, so maybe not best choice if patients finding it difficult to drink or on fluid restriction
- Contains K+ (and Na), so avoid in hyperkalaemia
- For stercoral colitis – consider 8 sachets in 1L drunk over 6 hours (the macrogol bomb!). Can avoid manual evacuation, but may need to be repeated
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- Phosphate enema
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- Can cause big electrolyte shifts, dehydration and AKI (be cautious in older adults)
- Technically should avoid in HF, CKD, if on ACE-i/diuretics
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- Microlax micro-enema
- Glycerol suppositories – safer than phosphate or microlax enemas
- Docusate – very poor evidence base, avoid
- Arachis oil enema
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- Sometimes used in impaction
- Avoid in nut allergy
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- Naloxigol
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- Peripherally acting opioid receptor antagonist
- It decreases the constipating effects of opioids without altering analgesia
- Most useful if opiates cause constipation (but some patients are constipated before opiates are given)
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Notes on causes and complications
- Functional constipation – may be due to
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- Dyssynergic defecation
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- A type of pelvic floor dysfunction where the muscles in the pelvis, rectum, and anal sphincter fail to coordinate properly during a bowel movement
- Can do anorectal manometry, defecography or balloon expulsion test
- Patients may spend a lot of time on the toilet trying to open bowels
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- Slow transit
- IBS-constipation (patients may take opioids too)
- Dyssynergic defecation
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- Levator Ani syndrome
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- Chronic or recurrent anorectal pain lasting > 30 minutes
- Tenderness during traction of puborectalis
- Consider other causes of rectal pain – fissure, haemorrhoids, cancer, IBD, abscess, fistula, prostatitis, coccygodynia, gynae causes
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- Narcotic bowel syndrome
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- Opioid-induced bowel dysfunction, characterised by the seemingly paradoxical development of escalating abdominal pain in the context of continuous or escalating doses of opioids
- Treatment is to stop opioids. May need admission for detox and patient-controlled analgesia
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- Faecal impaction
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- Try Movicol first (8 sachets daily)
- Then glycerine suppositories (after meals, they work in 10 minutes)
- Then a phosphate enema (not advised in the elderly/frail, cancer, neutropenic patients, CKD)
- Manual evacuation is a last resort
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- Bowel obstruction and ileus
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- Small intestinal and colonic dilatation can result from mechanical obstruction or severe intestinal dysmotility
- Can cause nausea and vomiting, constipation and abdominal pain or distension
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Acute small bowel obstruction
- Bowel sounds may be excessively active or reduced and high pitched
- Causes
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- Extrinsic
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- Adhesions
- Hernias
- Endometriosis
- Haematomas
- Neuro-endocrine tumours
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- Intrinsic
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- Crohn’s disease
- NSAID enteropathy
- Intestinal tuberculosis
- Intussusception
- Intestinal neoplasia
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- Small bowel adenocarcinomas (for example complicating coeliac disease or Lynch syndrome)
- Or benign small bowel tumours (such as the hamartomas of Peutz-Jegher’s syndrome)
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- Post-radiotherapy strictures
- Ischaemic strictures
- Intraluminal foreign bodies
- Bezoar
- Gallstone ileus
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- Extrinsic
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- Mechanical obstruction due to post-operative adhesions accounts for approximately 75% of acute small bowel obstruction presentations, followed by intestinal hernias and malignancies.
- Post-adhesional obstruction may occur as early as a few weeks or as late as several decades after the initial surgery
Chronic intestinal pseudo-obstruction (CIPO)
- Diagnosis of CIPO requires
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- Symptoms present for at least 6 months
- Radiological evidence of dilatation and/or air-fluid level in the gut with no evidence of mechanical cause
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- Causes
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- Familial
- Primary – due to autonomic dysfunction, neuromuscular dysfunction or enteric myopathy
- Secondary – paraneoplastic, diabetes, systemic sclerosis, Coeliac’s, Hirschsprung’s disease, Chagas disease, CMV, EBV, chemotherapy, radiotherapy, opiates, phenothiazines
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- Once gut dilatation is confirmed, CIPO is a diagnosis of exclusion – requires ruling out of other causes for GI tract dysmotility.
- Baseline blood should include
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- Amylase/lipase, lactate, inflammatory markers, coeliac serology and thyroid function
- Hypokalaemia may be present if there is vomiting, and a low potassium will exacerbate dysmotility
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- Biopsies (full thickness)
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- Can do for diagnostic confirmation of enteric neuropathy or myopathy
- Obtained from dilated and non-dilated gut segments when patients abdominal surgery for unexplained obstructive episodes
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- Management
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- No definitive curative therapy
- Consider nutrition, psychology, specialist surgery and histopathology
- Prokinetic medications (eg cholinesterase inhibitors) are evidence-based
- Alternative prokinetics such as erythromycin (motilin analogue), metoclopramide (dopamine receptor antagonist) and prucalopride (5HT-4 receptor agonist) have a limited effect in the maintenance setting
- IV neostigmine can be helpful in the acute setting, and oral pyridostigmine in the chronic setting
- Endoscopic decompression can be of useful in the acute setting (can encourage motility)
- Avoid surgery during an acute crisis – it often worsens symptoms of CIPO
- Small intestinal bacterial overgrowth is a frequent complication
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- Confirmation is typically by hydrogen-methane breath test
- Treatment is with broad-spectrum antibiotics (doxycycline, metronidazole, ciprofloxacin, rifaximin) for 10-14 days
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Acute colonic pseudo-obstruction (ACPO)
- Also known as Ogilvie’s syndrome
- Bowel dilation in the absence of mechanical obstruction
- More common in older hospitalised patients, especially men with multiple comorbidities or post-operatively
- Abdominal CT scan typically shows
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- Colonic dilation proximally up to the splenic flexure in the absence of mechanical obstruction or transition point
- Caecal diameter is an important indicator of the severity of disease
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- The primary symptom is distension but this is generally well tolerated
- Pain can suggest impending ischemia or perforation
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- Especially if associated with fever, guarding, leucocytosis and acidosis
- Can also be colonic atonia which precipitates a volvulus (of either the sigmoid, transverse colon or caecum). Colonic decompression (via a flatus tube or at endoscopy) is critical.
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- A differential is toxic megacolon which may occur in patients with IBD, infectious or ischaemic colitis. These patients often have a preceding history of diarrhoea and are usually more acutely ill.
- Management
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- Keep nil-by-mouth
- NG decompression
- If the dilatation does not settle, endoscopic decompression and use of prokinetics (as for CIPO) may be necessary
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