Oral Bowel Cleansing Agents (Guidelines)


This document aims to distill the recommendations of the NPSA Safety Alert RRR012 (February 2009) and subsequent BSG guidelines.


There have been a number of significant adverse events related to the administration of oral bowel cleansing preparations and an NPSA alert was issued to address this problem. The British Society for Gastroenterology responded by the production of consensus guidelines.The key points of that document are listed below. The Highland colonoscopy consent booklet takes into account the BSG recommendations

Key Points

The greater toxicity of phosphate containing preparations such as Fleet Phospho-Soda means that these forms of oral bowel cleansing agent should no longer be used in NHS Highland.

Gastrograffin is hyperosmolar and undiluted or in high dose may cause an osmotic diarrhoea.

Polyethylene glycols are non-absorbable isosmotic solutions that pass through the gut without net absorption or secretion. Significant fluid and electrolyte shifts are therefore attenuated. They must be diluted in large volumes of water. Compliance can be improved by dividing the dose regimen ie. 2 to 3 litres the night before the procedure with 1 to 2 litres of prep on the morning of the procedure. There is still the risk of water intoxication in predisposed patients. Domperidone or metoclopramide may improve the prep by speeding gastric emptying.

Picolax produces the driest bowel, Citramag intermediate and Klean Prep the wettest therefore is less suitable for radiological imaging.

Complications from bowel cleansing agents

  • Hypovolaemia: more so with low volume agents
  • Hypokalaemia: due to increased gastrointestinal loss with hyperosmotic and stimulant agents
  • Hyponatraemia: high volume agents and over-zealous drinking of plenty fluids

Absolute contra-indications for the use of oral bowel cleansing preparations

  • Gastro-intestinal obstruction or perforation, ileus or gastric retention
  • Acute intestinal or gastric ulceration
  • Severe inflammatory bowel disease or toxic megacolon
  • Reduced level of consciousness
  • Allergy to any of the preparation ingredients
  • Loss of swallow
  • Ileostomy

Administration of oral bowel cleansing preparations

  • The period of bowel cleansing should not normally exceed 24 hours
  • Hypovolaemia must be corrected prior to the administration of oral bowel cleansing preparations
  • Rehydration with an isotonic fluid such as Hartmann’s solution may be preferable.
  • If using Klean Prep it is reasonable to discontinue the PEG if the motions become watery and clear
  • Isotonic electrolyte oral rehydration solutions may be of benefit in patients at risk of hyponatraemia with Picolax or Citra Fleet.
  • Consider admitting frail patients for bowel preparation.
  • Renal function (including magnesium and phosphate) must be measured prior to administering Picolax or Citra Fleet oral bowel cleansing preparations. For patients taking Klean Prep or Plenvu, eGFR estimation is not mandatory but should be considered in patients with the following conditions: Diabetes; Hypertension; Cardiovascular disease (ischaemic heart disease, chronic heart failure, peripheral vascular disease and cerebral vascular disease); Structural renal tract disease, renal calculi or prostatic hypertrophy; Multisystem diseases with potential kidney involvement (eg, systemic lupus erythematosus); Family history of stage 5 chronic kidney disease or hereditary kidney disease; Haematuria or proteinuria
  • Citramag and Citra-Fleet should be avoided in patients with stage 5 chronic kidney disease who are not receiving haemodialysis.


Chronic haemodialysis
  • Each case should be discussed with the renal physicians
  • Polyethylene glycol runs the risk of volume overload
  • Picolax and Citra Fleet are safe for patients on haemodialysis
Peritoneal dialysis
  • Peritoneal dialysis is generally associated with less significant fluid shifts than haemodialysis
  • Some patients have a small but important residual renal function therefore admission to hospital to oversee administration of oral bowel cleansing preparations should be considered.
  • Peritoneal dialysis should continue as normal with the dialysate removed prior to the procedure.

Renal Transplant recipients

  • These patients should not receive sodium phosphate preparations unless all the alternative agents are contraindicated.
  • Each case should be discussed with the renal physicians

Congestive Cardiac Failure

  • PEG preparations are the preferred oral bowel cleansing preparations in patients with CCF
  • ACE inhibitors and angiotensin 2 receptor antagonists should be discontinued on the day of administration of the oral bowel cleansing preparations and not reinstated until 72 hours after the procedure.
  • Diuretics can lead to electrolyte imbalance and predispose to intravascular volume depletion and should be temporarily discontinued on the day of administration of oral bowel cleansing preparations


NSAIDs reduce renal perfusion and therefore limit the kidneys’ capacity to compensate for reduced renal perfusion through volume depletion. NSAIDs should be discontinued on the day of administration of oral bowel cleansing preparations and withheld until 72 hours after the procedure.

Medicines that may cause SIADH

These may lead to water retention and/or electrolyte imbalance

  • Tricyclic antidepressants
  • Selective serotonin reuptake inhibitors
  • Anti-psychotic agents
  • Carbamazepine

Classification of chronic kidney disease:

  • To confirm chronicity the eGFR should be measured on 2 separate occasions  more than 90 days apart
  • Markers for kidney damage include urinalysis abnormalities (eg. proteinuria) or abnormalities evident radiologically.
1Kidney damage evident. Normal or elevated GFR>90
2Kidney damage evident. Mildly reduced GFR60 to 89
3AModerately reduced GFR +/- documented kidney damage45 to 59
3BModerately reduced GFR +/- documented kidney damage30 to 44
4Severely reduced GFR +/- documented kidney damage15 to 29
5Kidney failure +/- documented kidney damage<15 or on dialysis

GP actions

When referring a patient who is likely to be prescribed an oral bowel cleansing agent.

  • Ensure renal function has been checked within 3 months on all patients.
  • Ensure referral contains past medical history and current medication and allergies
  • If the patient is frail (eg. poor mobility) consideration should be given to having the oral bowel cleansing agent administered as an in-patient.
  • Review medications
    • ACE inhibitors, angiotensin 2 receptor antagonists: safe to stop for 72 hours?
    • Diuretics: safe to stop for 24 hours?
    • NSAIDs: safe to stop for 72 hours?

Consultant vetting referral actions

  • Ensure the above information is available
  • Patients where hypovolaemia is considered a significant risk then Klean Prep should be prescribed.
  • CKD stages 3 to 5 Klean Prep is optimal but Picolax is acceptable
  • Haemodialysis, peritoneal dialysis and renal transplant patients should be discussed with the renal physician on call or via email to nhsh.raigmorerenal@nhs.scot

On admission

Patients admitted for in-patient administration of an oral bowel cleansing agent.

  • Renal function including magnesium and phosphate must be checked on admission
  • Medication must be reviewed including all the groups listed above.
  • Patients should be offered isotonic electrolyte oral rehydration solutions instead of water
  • Klean Prep administration may be discontinued if the bowel movements have become watery and clear.
  • If the bowel preparation appears to have failed with no significant bowel movement then the patient should not be sent to have the procedure and the appropriate department informed (ie. endoscopy or radiology). Arrangements should be made for further bowel preparation provided the patient’s renal function and vital signs are being closely monitored.
  • Renal function should be rechecked on the day of the procedure. Any deterioration in renal function should be discussed with the patient’s consultant and endoscopist/ radiologist prior to the procedure.

Last reviewed: 31/12/2019

Next review date: 31/12/2021

Author(s): Gastroenterology .

Reviewer name(s): Dr N Jamieson .

Document Id: TAM482