Bowel preparation in CT colonography: electrolyte and renal function disturbances in the frail and elderly patient

Computed Tomography Colonography (CTC): Is It Really the Non-Invasive Option We Think It Is? A Patient Experience Study

Aims: Computed tomography colonography (CTC) is seen as a more tolerable alternative to colonoscopy, but patients struggle with the steps required for optimal diagnostic imaging. This prospective study aims to understand the experience of patients undergoing CTC. Methods: A survey was completed by a convenience sample of patients before and after CTC over 7 months. The 13-item questionnaire covered pre-test information, overall and specific experience of the test. The responses were tabulated and analyzed using descriptive statistics. Qualitative free-text responses were coded for content and thematic analysis. Results: At a response rate of 51%, surveys were received from 41 patients. Overall, most patients (54%) found the investigation better than expected. However, 18% stated they were not informed of potential side effects. Side effects were experienced by 49% of patients, including diarrhea (34%) and abdominal pain (24%). About 59% experienced discomfort with gas insufflation, and 86% found turning during the investigation difficult. Conclusion: A significant proportion of patients undergoing CTC experience side effects and difficulties completing the investigation. Patient information is important to improve patient experience of CTC.

Split-dose bowel cleansing with picosulphate is safe and better tolerated than 2-l polyethylene glycol solution

BACKGROUND

In physically less fit patients and patients requiring repeated exams, adequate bowel preparation for colonoscopy remains problematic, particularly because patients need to drink large volumes of unpleasant-tasting fluids. A further concern is potential unwarranted fluid shifts.

AIMS

This study aimed to compare the safety and burden of a small-volume sodium picosulphate/magnesium citrate preparation (SPS-MC) with a 2-l ascorbic-acid-enriched polyethylene glycol solution plus bisacodyl pretreatment (PEG-Asc+B).

PATIENTS AND METHODS

Patients referred for colonoscopy were randomized to SPS-MC or PEG-Asc+B administered as a split-dose regimen. Patients received advice on the recommended 4-l SPS-MC and 2-l PEG-Asc+B fluid intake. Safety was assessed by blood sampling before and after the preparation and during a 30-day follow-up period. A questionnaire assessed tolerability and perceived burden of the preparation.

RESULTS

A total of 341 patients underwent colonoscopy. Blood sampling showed a slight but significant decrease in sodium, chloride and osmolality and increase in magnesium in the SPS-MC group and a decrease in bicarbonate in the PEG-Asc+B group. Hyponatraemia and hypermagnesaemia without clinical signs were observed in 16 (14 SPS-MC) and 13 SPS-MC patients, respectively. Patients reported significantly fewer physical complaints and a significantly higher completion rate with SPS-MC. Patients receiving SPS-MC rated the intake as being easier and better tasting. In the event of a repeat colonoscopy, 59.7% of patients in the PEG-Asc+B and 93.6% of patients in the SPS-MC group would opt for the same preparation again.

CONCLUSION

Despite electrolyte shifts, both SPS-MC and PEG-Asc+B appeared clinically safe. From a patient's perspective, a small-volume preparation formula such as SPS-MC is preferred, resulting in fewer physical complaints and greater ease of intake.

Magnesium and Drugs Commonly Used in Chronic Kidney Disease

As with other electrolytes, magnesium homeostasis depends on the balance between gastrointestinal absorption and kidney excretion. Certain drugs used commonly in patients with CKD can decrease gastrointestinal ingestion and kidney reclamation, and potentially cause hypomagnesemia. Other magnesium-containing drugs such as laxatives and cathartics can induce hypermagnesemia, particularly in those with impaired glomerular filtration and magnesium excretion. In this review, we will discuss the potential magnesium complications associated with a range of commonly encountered drugs in the care of CKD patients, discuss the potential mechanisms, and provide basic clinical recommendations.

Single-day sodium picosulfate and magnesium citrate versus split-dose polyethylene glycol for bowel cleansing prior to colonoscopy: A prospective randomized endoscopist-blinded trial

BACKGROUND AND AIM

The intake of polyethylene glycol (PEG) prior colonoscopy is frequently associated with nausea and abdominal discomfort. The aim of this study was to investigate whether sodium picosulfate and magnesium citrate (PMC) is superior to a polyethylene glycol (PEG) preparation in regard to patient acceptance. Furthermore, it investigates possible differences in efficiency and patient safety.

METHODS

In a randomised, prospective, and endoscopist-blinded study patients were 1:1 randomized to either use PMC or 4-L PEG in order to prepare for colonoscopy. Cleansing regimes consisted of a split-dose administration in the PEG arm and standard administration in the PMC arm. Primary end point was proportion of patients evaluating the bowel preparation procedure as "very distressing," defined as ≥ 8 points on a 10-point numeric rating scale (NRS). Secondary end points were quality of bowel preparation and electrolyte parameters.

RESULTS

PMC bowel-cleansing procedure was better tolerated compared with PEG (PMC(NRS<8)  = 89.9% vs PEG(NRS<8)  = 79.2%, P = 0.037). Mean declines in serum sodium (ΔSodium(PEG)  = -0.76 ± 3.07 vs ΔSodium(PMC)  = -3.38 ± 3.56 mmol/L; P < 0.001), chloride (ΔChloride(PEG)  = -1.00 ± 3.22 vs ΔChloride(PMC)  = -3.49 ± 3.51 mmol/L; P < 0.001), and osmolality (ΔOsmolality(PEG)  = -4.23 ± 6.82 vs ΔOsmolality(PMC)  = -8.83 ± 7.43 mosmol/kg; P < 0.001) were higher in the PMC arm than in the PEG arm. Hyponatremia after bowel preparation occurred more often in PMC (21.2%) than in PEG (4.0%) (P < 0.001). Successful preparation was achieved more frequently in the PEG arm (42.9% vs 82.2%; P < 0.001).

CONCLUSION

Standard picosulfate/magnesium citrate is better accepted than a split-dose PEG regimen. From the perspective of successful preparation and patients' safety, PEG is superior to PMC.

Serum magnesium concentrations in patients receiving sodium picosulfate and magnesium citrate bowel preparation: an assessment of renal function and electrocardiographic conduction

BACKGROUND

We performed a post hoc analysis of two clinical trials to assess whether sodium picosulfate and magnesium (Mg(2+)) citrate (Prepopik(®) [P/MC]), a dual-action bowel preparation for colonoscopy, has an impact on serum Mg(2+) levels and cardiac electrophysiology. Although rare, hypermagnesemia has been reported in patients consuming Mg(2+)-containing cathartics, especially patients who are elderly and have renal impairment.

METHODS

Data were analyzed from two prospective, Phase III, randomized, assessor-blinded, active-control, multicenter, pivotal studies that investigated split-dose/day-before P/MC. Serum Mg(2+) and creatinine clearance (CrCl) were measured at screening, on the day of colonoscopy, and 24-48 hours, 7 days, and 4 weeks after colonoscopy; electrocardiograms also were obtained at these time points.

RESULTS

In total, 304 patients received split-dose P/MC and 294 patients received day-before P/MC. Only 10% of the patients had serum Mg(2+) above the upper limit of normal (1.05 mmol/L) on the day of colonoscopy. There was a slight inverse correlation between CrCl and Mg(2+) levels on the day of colonoscopy; however, even at the lowest CrCl, serum Mg(2+) remained below clinically significant levels of 2.0 mmol/L. Increases in serum Mg(2+) were transient, with levels returning to baseline within 24-48 hours, regardless of renal function. No patients with elevated Mg(2+) experienced a corrected QT (QTc) interval >500 milliseconds or a QTc interval increase of ≥60 milliseconds from baseline. P/MC had no impact on PR or QRS interval.

CONCLUSION

P/MC produces little impact on serum Mg(2+) levels with no clinically significant effect on cardiac conduction in patients, including those with mild-to-moderate renal impairment.

Effectiveness of Sodium Picosulfate/Magnesium Citrate (PICO) for Colonoscopy Preparation

Purpose

Bowel preparation with sodium phosphate was recently prohibited by the U.S. Food and Drug Administration. Polyethylene glycol (PEG) is safe and effective; however, it is difficult to drink. To identify an easy bowel preparation method for colonoscopy, we evaluated three different bowel preparation regimens regarding their efficacy and patient satisfaction.

Methods

In this randomized, comparative study, 892 patients who visited a secondary referral hospital for a colonoscopy between November 2012 and February 2013 were enrolled. Three regimens were evaluated: three packets of sodium picosulfate/magnesium citrate (PICO, group A), two packets of PICO with 1 L of PEG (PICO + PEG 1 L, group B), and two packets of PICO with 2 L of PEG (PICO + PEG 2 L, group C). A questionnaire survey regarding the patients' preference for the bowel preparation regimen and satisfaction was conducted before the colonoscopies. The quality of bowel cleansing was scored by the colonoscopists who used the Aronchick scoring scale and the Ottawa scale.

Results

The patients' satisfaction rate regarding the regimens were 72% in group A, 64% in group B, and 45.9% in group C. Nausea and abdominal bloating caused by the regimens were more frequent in group C than in group A or group B (P < 0.01). Group C showed the lowest preference rate compared to the other groups (P < 0.01). Group C showed better right colon cleansing efficacy than group A or group B.

Conclusion

Group A exhibited a better result than group B or group C in patient satisfaction and preference. In the cleansing quality, no difference was noted between groups A and C.

Bowel preparation for CT colonography

Bowel preparation represents an essential part of CT colonography, as the accuracy of the exam is strongly related to the adequacy of colonic cleansing, and a poor bowel preparation may compromise the diagnostic quality even despite optimization of all other acquisition parameters. Residual stool and fluid in the large bowel may affect the interpretation of the exam and may increase the number of false positives and false negatives. In this regard, the majority of patients having undergone CT colonography state that bowel preparation is the most unpleasant part. Unfortunately, to date no definite consensus has been reached about the ideal bowel preparation technique, and there is great variability in preparation strategies across diagnostic centers. The purpose of this review article is to describe the development and evolution of bowel preparation techniques in order to choose the best approach for optimizing the diagnostic quality of CT colonography in each patient.

Serial monitoring of the physiological effects of the standard Pico-Salax® regimen for colon cleansing in healthy volunteers

BACKGROUND

Sodium picosulfate⁄magnesium oxide⁄citric acid (Pico-Salax, Ferring Inc, Canada) is used widely in Canada and other countries for colon cleansing before colonoscopy. It is a low-volume osmotic⁄stimulant agent with the potential to deplete intravascular volume and alter electrolyte balance, yet there are little data regarding its effects on these clinically important end points.

OBJECTIVE

To serially measure parameters of intravascular volume and electrolyte status in healthy volunteers over a 24 h period using the standard two-sachet dosing.

METHODS

Twenty volunteers were given one sachet of Pico-Salax at time 0 h and another sachet 5 h later, as per usual bowel cleansing protocol. Subjects were continually monitored during the first 12 h of the study with postural vital signs, serum electrolytes and electrocardiograms obtained at intervals throughout this initial period and again at 24 h postingestion.

RESULTS

No adverse events were reported nor were there any signs of intravascular volume depletion observed. There were decreases in potassium and calcium levels from baseline to 12 h, but these appeared minor and were corrected by 24 h. The proportions of patients with hypermagnesmia at 0 h, 5 h, 12 h and 24 h were 5%, 35%, 35% and 20%, respectively (P<0.05). However, the maximal values were only minimally elevated. Mean serum sodium, phosphate and creatinine levels remained within their respective reference ranges. There was a trend toward an increase in maximum corrected QT intervals from time 0 h (418 ms) to 5 h (430 ms) (P=0.06), but no significant change was seen subsequently at 12 h (419 ms). The subjects tolerated the medication well. The mean number of bowel movements per subject was 8.15 (range four to 15). Subjects consumed a mean (± SD) of 3.49±1.53 L of fluids during the observation period.

CONCLUSIONS

The proportion of individuals with hypokalemia, hypocalcemia and hypermagnesemia following two sachets of Pico-Salax is significant, but the magnitude of the changes was not clinically relevant in this relatively small group, and both calcium and potassium levels normalized at 24 h. Nonetheless, this could have implications in patients with pre-existing electrolyte abnormalities and the safety of dosing with more than two sachets.

Evidence review and status update on computed tomography colonography

Computed tomographic (CT) colonography is being implemented increasingly in the USA and Europe, and in many centers it has become the radiological technique of choice for imaging the whole colorectum. Although high diagnostic accuracy has been demonstrated in both screening and symptomatic populations, controversy persists regarding implementation, who should interpret the examination, and its cost effectiveness, particularly in the context of primary colorectal cancer screening. Published research in recent years has demonstrated efficacy in a wide range of patient groups, striking technical improvements, and high levels of patient acceptability. New developments continue in the fields of computer aided detection, digital cleansing, and integration into positron emission tomography. The purpose of this review is to bring the reader up-to-date with the latest developments in CT colonography, in particular, those of the last year.

[CT colonography: what radiologists need to know]

In 2008, CT colonography was approved by the American Cancer Society as a technique for screening for colorectal cancer. This approval should be considered an important step in the recognition of the technique, which although still relatively new is already changing some diagnostic algorithms. This update about CT colonography reports the quality parameters necessary for a CT colonographic study to be diagnostic and reviews the technical innovations and colonic preparation for the study. We provide a brief review of the signs and close with a discussion of the current indications for and controversies about the technique.

The safety of osmotically acting cathartics in colonic cleansing

Efficient cleansing of the colon before a colonoscopy or a radiological examination is essential. The osmotically acting cathartics (those given the Anatomical Therapeutic Chemical code A06AD) currently used for this purpose comprise products based on three main substances: sodium phosphate, combinations of polyethylene glycol and electrolyte lavage solutions (PEG-ELS), and magnesium citrate. All these preparations give adequate cleansing results and have similar profiles in terms of the frequency and type of mild to moderate adverse effects. However, serious adverse events, such as severe hyperphosphatemia and irreversible kidney damage owing to acute phosphate nephropathy, have been reported after use of sodium-phosphate-based products. The aim of this Review is to provide an update on the potential safety issues related to the use of osmotically acting cathartics, especially disturbances of renal function and water and electrolyte balance. The available evidence indicates that PEG-ELS-based products are the safest option. Magnesium-citrate-based, hypertonic products should be administered with caution to elderly individuals and patients who are prone to develop disturbances in water and electrolyte balance. Sodium-phosphate-based products can occasionally cause irreversible kidney damage and should not be routinely used in bowel-cleansing procedures.

Bowel preparation suitable for same-day computed tomography colonography and colonoscopy

PURPOSE

This study was designed to evaluate whether a bowel preparation used for computed tomography (CT) colonography could also be suitable for same-day colonoscopy regardless of which test was done first.

METHOD

Six different endoscopists working at 3 separate hospitals evaluated 75 patients who underwent colonoscopy after receiving a bowel preparation that contained contrast material used to tag fecal and fluid material to facilitate CT colonography. This bowel preparation has been used in more than 1500 CT colonography studies. Evaluation included assessment of whether the colon was clean and dry, and whether the contrast material caused any impairment of visualization or clogging of the endoscopes. Some of the patients had first undergone CT colonography followed by same-day colonoscopy, whereas other patients had colonoscopy as their initial test.

RESULTS

Although the contrast material was sometimes perceptible, the volumes were very small, and caused no impairment of mucosal visualization and no clogging of the endoscopes. The bowel preparation was well tolerated. Same-day CT colonography and colonoscopy with fecal tagging was technically possible.

CONCLUSION

A simple, fairly low cost 1-day bowel preparation with fluid and fecal tagging is suitable for CT colonography and colonoscopy done the same day in either order. However, the preferences of individual endoscopists and difficulties with making oral contrast agents readily available are challenges to widespread adoption of a common bowel preparation regimen.