Constipation
Key points
Anatomy and physiology
Components to anal sphincter complex:
External sphincter and levator muscles - voluntary control
Internal sphincter - involuntary
Rectoanal inhibition reflex (RAIR) - causes transient relaxation of internal sphincter when rectum filling - allows distinguishing between flatus and solid stools
Both sphincters and RAIR need to be intact for optimal continence
Rectum should usually be empty
Rome IV criteria for functional constipation
≥2 of the following
1. ≤2 defecations/week in a child of a developmental age of ≥4 years.
2. ≥1 episode of faecal incontinence/week
3. History of retentive posturing or excessive volitional stool retention.
4. History of painful or hard bowel movements.
5. Presence of a large fecal mass in the rectum.
6. History of large diameter stools that can obstruct the toilet
Investigations
Thyroid function, Cystic Fibrosis testing, Coeliac screen
Anorectal manometry
Balloon catheter in anal canal
Measure resting pressure
Inflate balloon - check sensation
If pressure goes down (rectum relaxes) - means that RAIR is intact
Ask patient to squeeze then bear down and try and pass balloon
Low resting pressure - found in anorectal malformation patients, will likely be incontinent
Internal sphincter achalasia - absence of a normal RAIR with a normal rectal biopsy is diagnostic - treat with botox - as effective as myectomy - Keshtgar RCT 2007 JPedSurg
Myectomy has been abandoned due to permanent incontinence
Anal sphincter dysnergia - external sphincter contracts as opposed to relaxing at the time of bearing down - treat with biofeedback and botox
Colonic motility studies can distinguish between overflow and true incontinence
100 opaque markers given - AXR at 100 hours
NICE rectal biopsy 'do not do recommendations'
Do not do unless any have been/are present:
• delayed passage of meconium (more than 48 hours after birth in term babies)
• constipation since first few weeks of life
• chronic abdominal distension plus vomiting
• family history of Hirschsprungs disease
• faltering growth in addition to any of the previous features
Hirschprungs disease unlikely in the older child if soiling
Medical management
Refer all patients to ERIC charity website
Side effects of phosphate enema:
hyperphosphataemia, hypocalcaemia, hypernatraemia, hypokalaemia and metabolic acidosis
Lactulose
Fructose + galactose
Not metabolised in SB
Bacterial fermentation in colon into lactic + acetic acid - H+ can bind NH4
Macrogol
Polyethylene glycol - osmotic
Sodium picosulphate
Gut bacteria metabolise in colon to active compound - stimulant laxative
Senna
Breakdown products irritate colonic wall
Rectal irrigation systems e.g. Aquaflush, Qufora - large volume saline or water washout
Ideally:
Give laxatives only for continent patients that are constipated
Give enemas only for incontinent patients, can use loperamide as adjunct to thicken stool first
Surgical management
Antegrade continence enema (ACE)
Laparoscopic formation - bring out appendix as stoma
Creates stable stoma - daily catheterisations or indwelling tube
50% complication rate - stenosis/prolapse
Continence rate 70-95%
Rectal irrigation just as effective
Tube caecostomy has indwelling device e.g. Button - goes directly to caecum
If failing management - discuss in MDT
Specialist options:
Laparoscopic rectosigmoid resection - good results but only level 4-5 evidence
Ileostomy if colonic dysmotility and malnutrition
Sacral nerve stimulation (SNS)
Lead implanted in S3 foramen
Lu et al - 25 patients, varied causes of constipation, SNS improved both faecal and urinary continence
References
Whyte, Christine, et al. "Fecal Incontinence and Functional Constipation." Pediatric Surgery NaT, American Pediatric Surgical Association, 2020. Pediatric Surgery Library, www.pedsurglibrary.com/apsa/view/Pediatric-Surgery-NaT/829677/all/Fecal_Incontinence_and_Functional_Constipation.
https://www.mdcalc.com/calc/10331/rome-iv-diagnostic-criteria-child-functional-constipation
Lee TH, Bharucha AE. How to Perform and Interpret a High-resolution Anorectal Manometry Test. J Neurogastroenterol Motil. 2016 Jan 31;22(1):46-59. doi: 10.5056/jnm15168. PMID: 26717931; PMCID: PMC4699721.
Keshtgar AS, Ward HC, Sanei A, Clayden GS. Botulinum toxin, a new treatment modality for chronic idiopathic constipation in children: long-term follow-up of a double-blind randomized trial. J Pediatr Surg. 2007 Apr;42(4):672-80. doi: 10.1016/j.jpedsurg.2006.12.045. PMID: 17448764.
Lu PL et al Sacral nerve stimulation for constipation and fecal incontinence in children: Long-term outcomes, patient benefit, and parent satisfaction. Neurogastroenterol Motil. 2018 Feb;30(2). doi: 10.1111/nmo.13184. Epub 2017 Aug 10. PMID: 28799195.