[Optimal Laxatives for Oral Colonoscopy Bowel Preparation: from High-volume to Novel Low-volume Solutions]

Optimal bowel preparation is essential for a more accurate, comfortable, and safe colonoscopy. The majority of postcolonoscopy colorectal cancers can be explained by procedural factors, mainly missed polyps or inadequate examination. Therefore the most important goal of optimal bowel preparation is to reduce the incidence of colorectal cancer. Although adequate preparation should be achieved in 85-90% or more of all colonoscopy as a quality indicator, unfortunately 20-30% shows inadequate preparation. Laxatives for oral colonoscopy bowel preparation can be classified into polyethylene glycol (PEG)-electrolyte lavage solution, osmotic laxatives, stimulant laxatives, and divided into high-volume solution (≥3 L) and low-volume solution (<3 L). The updated 2019 European Society of Gastrointestinal Endoscopy (ESGE) guideline is broadly similar to the 2014 American Society for Gastrointestinal Endoscopy (ASGE) recommendations and reaffirms the importance of split-dosing. However, new ESGE guideline, unlike the 2014 ASGE recommendation, suggests the use of high volume or low volume PEG-based regimens as well as that of non-PEG based agents that have been clinically validated for most outpatient scenarios. For effective, safe, and highly adherent bowel preparation, physicians who prescribe and implement colonoscopy should properly know the advantages and limitations, the dosing, and the timing of regimens. Recently many studies have attempted to find the most ideal regimens, and more convenient, effective, and safe regimens have been developed by reducing the dosing volume and improving the taste. The high tolerability and acceptability of the new low-volume regimens suggest us how we should use it to increase the participation of the national colorectal cancer screening program.

Safety and Efficacy of Low-Volume Preparation in the Elderly: Oral Sulfate Solution on the Day before and Split-Dose Regimens (SEE SAFE) Study

Background/Aims

The use of a low-volume bowel cleansing agent is associated with a greater willingness to undergo repeat colonoscopy. Oral sulfate solution (OSS) is a recently approved low-volume agent; however, its efficacy and safety in the elderly population remain unclear. We aimed to evaluate the efficacy, safety, and acceptability of the OSS preparation, in comparison to those of a standard polyethylene glycol (PEG; 4 L) preparation, in elderly patients.

Methods

A multicenter, randomized, investigator-blinded study was conducted. Participants were randomized to receive OSS or 4-L PEG with a split-dose regimen. Bowel cleansing efficacy was assessed using the Boston Bowel Preparation Scale (BBPS). Acceptance, satisfaction, and preparation-related symptoms were recorded. Additionally, blood parameters were analyzed for electrolyte abnormalities and nephrotoxicity.

Results

A total of 193 patients were analyzed. No group differences in overall bowel cleansing efficacy were observed, with “adequate” preparations achieved in 95.9% (93/97) and 94.8% (91/96) of patients in the OSS and 4L PEG groups, respectively (p=0.747). However, mean BBPS scores for the entire (p=0.010) and right colon (p=0.001) were significantly higher in the OSS group than in the 4-L PEG group. The severity of clinical adverse events and frequency of acute kidney injury were similarly low, and no clinically meaningful electrolyte changes were identified. Self-reported scores regarding amount (p<0.001) and feeling (p=0.007), as well as overall satisfaction (p=0.001) and willingness to repeat the preparation (92.8% vs 67.7%, p<0.001), were significantly better in the OSS group than in the 4-L PEG group.

Conclusions

In elderly individuals, OSS with a split-dose regimen has greater acceptability and comparable efficacy in bowel cleansing compared to 4-L PEG. (Clinical trials registration number: NCT03112967)

Bowel preparation for colonoscopy: what is best and necessary for quality?

PURPOSE OF REVIEW

Colonoscopy is recognizably, the best colon cancer prevention test, provided the quality of the preparation is adequate for detection of precancerous polyps but also allowing for accurate identification of margins, thereby facilitating complete endoscopic resection. As there are many aspects effecting colon prep outcomes, it is timely to review new standards for optimizing outcomes, including product selection based on patient demographics.

RECENT FINDINGS

New national guidelines have set a minimum quality threshold for adequacy and also defined a split day delivery for oral options as the "standard of care". Several new prep options have been recently released and these data are discussed.

SUMMARY

Optimizing the quality of colon preps has major implications for clinical practice. Clinicians must recognize new targets for standard of care, providing the best approach for each individual patient, considering variable factors which may otherwise compromise success.

A comparative review of use of sulphate and phosphate salts for colonoscopy preparations and their potential for nephrotoxicity

Background and study aims  Colonoscopy is a widely used diagnostic procedure which requires prior cleansing of the bowel. Many different bowel cleansing preparations have been developed, all of which have specific advantages and disadvantages. This review compares two low-volume high-osmolarity bowel cleansing preparations, oral phosphate salts and oral sulphate salts, with a particular focus on risk of nephrotoxicity. Patients and methods  An electronic search of the Medline database was performed using the search terms "(phosphates OR sulfates) AND cathartics [MeSH Term] AND kidney" restricted to humans with a cut-off date of December 31, 2016. Results  Introduction of oral phosphate salts offered the advantage of low intake volume and low risk of bowel irritation compared to previous options. However, phosphate salts have been associated with renal toxicity (acute phosphate nephropathy [APN]), thought to arise due to perturbations of calcium and phosphate homeostasis as a consequence of increases in serum phosphate. This results in high concentrations of calcium phosphate in the distal tubule and collecting ducts of the kidney, where it may precipitate. Although APN is rare, it may lead to permanent kidney damage. For this reason, phosphate salts are contraindicated in vulnerable patient groups. As an alternative to phosphate salts, oral sulphate salts have recently been introduced. Because sulphate absorption from the intestinal tract is saturable, serum sulphate concentrations increase only minimally after ingestion. Furthermore, excretion of sulphate in the kidney is not accompanied by calcium excretion and urine calcium levels are unchanged. For these theoretical reasons, use of sulphate salts as bowel cleansing solutions is not expected to lead to calcium precipitation in the nephron. Conclusions  Oral phosphate salts are no longer recommended for routine use as bowel cleansing preparations as they carry significant risk of kidney damage and a safer alternative is available in the form of oral sulphate solutions. To date, use of sulphate salts has not been associated with elevations in serum creatinine or other markers of renal impairment, nor with clinical manifestations of kidney injury. Nonetheless, experience with sulphate salts in everyday practice is limited and physicians should be vigilant in detecting potential safety issues.

Acute kidney injury following implementation of an enhanced recovery after surgery (ERAS) protocol in colorectal surgery

PURPOSE

Fluid management within Enhanced Recovery After Surgery (ERAS) protocols is designed to maintain a euvolemic state avoiding the negative sequelae of hypervolemia or hypovolemia. We sought to determine the effect of a recent ERAS protocol implementation on kidney function and on the incidence of postoperative acute kidney injury (AKI).

METHODS

A total of 132 elective colorectal resections performed using our ERAS protocol were compared to a propensity-matched group prior to ERAS implementation. Fluid balance, urine output, creatinine, and blood urea nitrogen (BUN) were recorded for all patients, and the incidence of AKI was determined according to the Kidney Disease Improving Global Outcomes (KDIGO) criteria.

RESULTS

Implementation of our ERAS protocol decreased average postoperative length of hospital stay (5.5 vs 7.7 days, p < 0.0001) and time to return of bowel function (2.5 vs 4.1 days, p < 0.0001). The rate of postoperative AKI increased following implementation of the protocol (11.4 vs 2.3%, p < 0.0001). However, by the time of discharge, the average creatinine of ERAS patients who had experienced AKI had returned to their preoperative baseline values (p = 0.9037). Significant univariate predictors of AKI in ERAS patients were longer operative times (p < 0.01) and the diagnosis of diverticulitis (p < 0.01). Within our ERAS patients, AKI was associated with a prolonged postoperative length of hospital stay (p < 0.01).

CONCLUSIONS

Despite the proven benefits of the Enhanced Recovery After Surgery (ERAS) protocols, care should be taken during protocol implementation to monitor for and to prevent acute kidney injury.

Comparison of trends in colorectal cancer screening in the US end-stage renal disease population and the US Medicare population

Background

Methods

Results

Conclusions

Severe metabolic changes following oral sodium phosphate in a patient of renal cell carcinoma - On dialysis

Oral sodium phosphate (OSP), an effective bowel purgative, is available over the counter (OTC) and requires a substantially lower volume than polyethylene glycol-based preparative agents. Rarely, OSP consumption has been associated with acute hypocalcemia and hyperphosphatemia. We describe a case of chronic kidney disease patient developing symptomatic hypocalcemia following OTC OSP.

Acute Phosphate Nephropathy with Diffuse Tubular Injury Despite Limited Calcium Phosphate Deposition

An 86-year-old woman developed acute kidney injury after colonoscopy. A renal biopsy showed diffuse tubular injury with minimal calcium phosphate deposits (CPDs), which were thought to be caused by an oral sodium phosphate bowel purgative before colonoscopy. According to these findings, she was diagnosed with acute phosphate nephropathy (APhN). In contrast to previous reports of diffuse tubular injury associated with tubular CPDs in APhN, this case demonstrated diffuse tubular injury despite a limited distribution of CPDs, suggesting that calcium phosphate can cause tubular injury without deposition. This case thus supports the hypothesis that urinary calcium phosphate crystals may cause tubular injury via other mechanisms, including inflammatory cytokines.

Advances in bowel preparation for colonoscopy

Precolonoscopy bowel preparation is adequate to identify lesions larger than 5 mm about 70% to 75% of the time, but the opportunity for further improvement exists. The use of high-quality formulations with established efficacy rates of 90% or greater, identification of patients who are at increased risk of an inadequate preparation, as well as patient education and motivation to be invested in the process further improves the success of cleansing. Endoscopists should strive to achieve an adequate bowel preparation in 85% or more of patients. High-quality colonoscopy requires high-quality bowel cleansing.

Safety of medical therapy in patients with chronic kidney disease and end-stage renal disease

PURPOSE OF REVIEW

Maintaining patient safety is a necessary step to improve healthcare delivery. Patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD) have an increased frequency of adverse safety events largely because of medication errors.

RECENT FINDINGS

CKD and ESRD have several features which threaten patient safety. Reduced glomerular filtration rate affects the clearance of many medications and is also associated with several comorbidities such as diabetes, cardiovascular disease, metabolic bone disease, and anemia. These comorbidities of CKD often increase the complexity of treatment regimens. Patients with ESRD, requiring dialysis or transplantation, have an even greater potential for adverse safety events because of the reliance on renal replacement modalities and the frequent requirements of polypharmacy and potential drug-drug interactions.

SUMMARY

There is an important need to develop strategies to provide inpatient and outpatient management plans to limit the risk of adverse medication errors across a wide range of educational and socioeconomic backgrounds, and a critical need to develop a uniform set of standards for evaluating patient safety in CKD and ESRD as well as appropriate descriptions of the prototypical safety profiles of patients who have CKD, a kidney transplant, or who are on dialysis.

Sodium phosphate does not increase risk for acute kidney injury after routine colonoscopy, compared with polyethylene glycol

BACKGROUND & AIMS

Oral sodium phosphate (OSP) is a common bowel purgative administered before colonoscopy; the Food and Drug Administration has warned against its use because of concerns about acute kidney injury (AKI) from the absorbed phosphate and dystrophic calcification. However, it is not clear if OSP is associated with AKI in the general population or in high-risk subgroups undergoing colonoscopy. We estimated the risk of AKI among patients undergoing a screening colonoscopy using OSP vs polyethylene glycol (PEG) for bowel cleansing in a large, US-based claims database.

METHODS

We used an insurance database to identify a cohort of patients ages 50 to 75 years who underwent screening colonoscopies as outpatients from January 2000 through November 2008 (before the Food and Drug Administration warning), receiving OSP (n = 121,266) or PEG (n = 429,430) within 30 days beforehand, without prior use of either drug. We collected data from patients for 6 months afterward to identify those who developed AKI or renal failure, or received dialysis. Adjusted and propensity score-matched hazard ratios (HR) and 95% confidence intervals (CI) were estimated using Cox proportional hazards models. We investigated the effects in subgroups with higher AKI risk (patients with chronic kidney disease, kidney stones, hypertension, or diabetes, or using antihypertensive or nonsteroidal anti-inflammatory drugs).

RESULTS

AKI occurred in 0.2% of OSP users and in 0.3% of PEG users (adjusted HR, 0.86; 95% CI, 0.75-0.99). OSP users matched well with PEG users, producing similar estimates (HR, 0.85; 95% CI, 0.72-1.01). We did not observe a consistent increase in the risk of AKI or other outcomes in any subgroups analyzed.

CONCLUSIONS

In a large database analysis, we did not associate administration of OSP before colonoscopy with increased risk of postprocedure AKI, even in high-risk clinical subgroups.

A murine model of phosphate nephropathy

We established a murine model of phosphate nephropathy with secondary hyperparathyroidism. db/db mice, which develop obesity and type 2 diabetes mellitus, were uninephrectomized at the age of 6 weeks and were fed either standard chow or a phosphorus-rich diet during the next 8 weeks. Thereafter, renal cryosections showed abundant tubular casts with a strong histochemical von Kossa reaction in all db/db mice on the phosphorus-rich diet but none in the controls. X-ray diffraction and Raman spectroscopy proved that these tubular casts consist mostly of hydroxyapatite Ca₅(PO₄)₃(OH). These intraluminal precipitations were located in distal tubuli and collecting ducts and were associated with degenerative tubular changes and peritubular infiltration of T cells and macrophages. In line, kidneys of db/db mice on the phosphorus-rich diet displayed significantly increased mRNA expression of the T(H)1 cytokines interferon γ, IL-6, and tumor necrosis factor α. In addition, mice developed signs of secondary hyperparathyroidism as shown by elevated serum phosphate, decreased serum calcium, and increased parathyroid hormone, osteopontin, and fibroblast growth factor 23 levels. db/db mice on the phosphorus-rich diet also presented with significantly lower body weight, lower homeostasis model assessment of insulin resistance index, and hypertrophic cardiomyopathy. Thus, we provide a murine model of phosphate nephropathy and secondary hyperparathyroidism, which can be used for future pharmacologic and pathophysiologic studies to analyze the effect of hyperphosphatemia on renal, metabolic, and cardiovascular phenotypes.

Acute phosphate nephropathy: a cause of chronic kidney disease

Acute phosphate nephropathy occurs whenever a patient with renal dysfunction is exposed to high doses of phosphate. Bowel purgative agents are a common source of high doses of sodium phosphate and are widely used as bowel preparation agents prior to colonoscopy due to their efficacy and tolerability. Oral sodium phosphate (OSP) preparations used to prepare patients for colonoscopy may be a cause of acute and chronic kidney disease (CKD). CKD associated with OSP agents is the result of nephrocalcinosis, or calcium phosphorus crystal deposition in the renal parenchyma leading to interstitial disease. It is often irreversible and progressive in nature. The authors report a case of CKD which presented with non-specific symptoms weeks after use of an OSP agent as part of a bowel preparation regimen. Renal biopsy confirmed nephrocalcinosis.

Randomised clinical trial: MiraLAX vs. Golytely - a controlled study of efficacy and patient tolerability in bowel preparation for colonoscopy

BACKGROUND

MiraLAX is gaining acceptance as a bowel cleanser for colonoscopy. We hypothesize that MiraLAX/Gatorade is as efficacious for bowel cleansing as Golytely and is more tolerable for patients undergoing screening colonoscopy.

AIM

To compare bowel preparation scores of MiraLAX/Gatorade vs. Golytely and examine differences in patient tolerability.

METHODS

  Patients undergoing screening colonoscopy were randomized to 4 L Golytely or 238 g MiraLAX in 64 ounces Golytely and four bisacodyl tablets. Efficacy in bowel cleansing was assessed using the Boston Bowel Preparation Scale (BPPS). Subjects completed a brief survey assessing patient tolerability.

RESULTS

A total of 190 patients were enrolled (85 male, 105 female; mean age 56.9 years, s.d. 6.3); 87 were randomized to MiraLAX, 103 to Golytely. There was no difference in age, gender or timing of colonoscopy between the bowel preparation groups. Golytely's median total BBPS score was significantly higher than that of MiraLAX [9 (IQR 7-9) vs. 8 (IQR 6-9), P = 0.034]. Golytely had a higher rate of an excellent equivalent BBPS score of 8 or 9 than MiraLAX (70% vs. 55%, P = 0.036). There was no difference in patient tolerability (P = 0.857).

CONCLUSIONS

Golytely was more efficacious than MiraLAX/Gatorade in bowel cleansing; both preparations were equally tolerated by patients.

Design and analysis of multiple events case-control studies

In case-control research where there are multiple case groups, standard analyses fail to make use of all available information. Multiple events case-control (MECC) studies provide a new approach to sampling from a cohort and are useful when it is desired to study multiple types of events in the cohort. In this design, subjects in the cohort who develop any event of interest are sampled, as well as a fraction of the remaining subjects. We show that a simple case-control analysis of data arising from MECC studies is biased and develop three general estimating-equation-based approaches to analyzing data from these studies. We conduct simulation studies to compare the efficiency of the various MECC analyses with each other and with the corresponding conventional analyses. It is shown that the gain in efficiency by using the new design is substantial in many situations. We demonstrate the application of our approach to a nested case-control study of the effect of oral sodium phosphate use on chronic kidney injury with multiple case definitions.

Incidence and outcome of acute phosphate nephropathy in Iceland

BACKGROUND

Oral sodium phosphate solutions (OSPS) are widely used for bowel cleansing prior to colonoscopy and other procedures. Cases of renal failure due to acute phosphate nephropathy following OSPS ingestion have been documented in recent years, questioning the safety of OSPS. However, the magnitude of the problem remains unknown.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted a population based, retrospective analysis of medical records and biopsies of all cases of acute phosphate nephropathy that were diagnosed in our country in the period from January 2005 to October 2008. Utilizing the complete official sales figures of OSPS, we calculated the incidence of acute phosphate nephropathy in our country. Fifteen cases of acute phosphate nephropathy were diagnosed per 17,651 sold doses of OSPS (0.085%). Nine (60%) were women and mean age 69 years (range 56-75 years). Thirteen patients had a history of hypertension (87%) all of whom were treated with either ACE-I or ARB and/or diuretics. One patient had underlying DM type I and an active colitis and one patient had no risk factor for the development of acute phosphate nephropathy. Average baseline creatinine was 81.7 µmol/L and 180.1 at the discovery of acute renal failure, mean 4.2 months after OSPS ingestion. No patient had a full recovery of renal function, and at the end of follow-up, 26.6 months after the OSPS ingestion, the average creatinine was 184.2 µmol/L. The average eGFR declined from 73.5 ml/min/1.73 m(2) at baseline to 37.3 ml/min/1.73 m(2) at the end of follow-up. One patient reached end-stage renal disease and one patient died with progressive renal failure.

CONCLUSION/SIGNIFICANCE

Acute phosphate nephropathy developed in almost one out of thousand sold doses of OSPS. The consequences for kidney function were detrimental. This information can be used in other populations to estimate the impact of OSPS. Our data suggest that acute phosphate nephropathy may be greatly underreported worldwide.

Complications of colonoscopy: magnitude and management

Although complications of colonoscopy are rare, they are potentially serious and life threatening. In addition, less serious adverse events may occur frequently and may have an impact on a patient's willingness to undergo future procedures. This article reviews the magnitude of and risk factors for major and minor colonoscopy complications, discusses management of complications, and suggests ways to design quality improvement programs to reduce the risk of complications.

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.

A prospective assessment of renal impairment after preparation for colonoscopy: oral sodium phosphate appears to be safe in well-hydrated subjects with normal renal status

BACKGROUND

The outcome of colonoscopy is highly dependent upon the quality of bowel cleansing prior to the procedure. Oral sodium phosphate solutions (OSPS) or preparations containing polyethylene glycol (PEG) are generally employed. However, the safety of administering OSPS prior to colonoscopy has been questioned because of the potential for renal failure.

AIM

To compare rates of renal failure after OSPS and PEG in a randomized, prospective trial and to assess the quality of colonoscopy after these two bowel preparations.

METHODS

Subjects with eGFR >or= 60 ml/min/1.73 m(2) and expressed willingness to adhere to hydration recommendations were randomized to OSPS or PEG solutions. Renal function was assessed 1 week prior to, immediately prior to, and 1 week after colonoscopy.

RESULTS

No subject had acute kidney failure after OSPS or PEG. OSPS was associated with significant increases in the serum phosphate and sodium levels and significant decreases in the calcium and potassium levels. These values returned to normal limits in all subjects by 1 week after colonoscopy. The quality of colonic cleansing was superior after OSPS than after PEG (Ottawa score 2.5 +/- 2.2 vs. 3.5 +/- 2.3, respectively, P < 0.05). The detection of one or more adenomatous polyps was higher after OSPS than after PEG.

CONCLUSIONS

Renal failure was not detected after the use of OSPS for colonoscopy preparation in subjects with recently documented normal renal function who were able to consume the required amounts of water after each dose. However, based on the number of subjects studied, the theoretical risk of this complication is still between 0 and 6.3%. Thus, it is appreciated that only a very large prospective trial would have yielded a more accurate estimate of the likelihood of renal compromise after OSPS. Despite this caveat, OSPS has advantages over PEG in terms of the adequacy of colonic visualization and the number of polyps detected.

Change in renal function after sodium phosphate preparation for screening colonoscopy

AIM: To investigate the changes in renal function at 12-24 mo in patients following sodium phosphate (NaP) preparation for screening colonoscopy.

METHODS: We carried out a retrospective study on the results from patients who received health check-up services as part of an employer-provided wellness program performed between August 2006 and May 2008 and who were followed up for 12-24 mo. Prior to screening colonoscopy, 224 patients underwent bowel cleansing with NaP (NaP group) and 113 patients with polyethylene glycol (PEG group). The control group comprised 672 age-matched patients. We compared the changes in the creatinine levels and the glomerular filtration rates (GFRs) from baseline to 12-24 mo between the NaP, PEG, and control groups using two-way repeated measured analysis of variance. In addition, multivariate linear regression analysis was performed to assess the risk factors for a decreased GFR.

RESULTS: The baseline mean serum creatinine level in the NaP, PEG, and control groups was 1.12 ± 0.15, 1.12 ± 0.16, and 1.12 ± 0.15 mg/dL, which increased to 1.15 ± 0.15, 1.15 ± 0.18, and 1.15 ± 0.15 mg/dL, respectively, after 12-24 mo. The baseline mean GFR in the NaP, PEG, and control groups was 69.0 ± 7.7, 68.9 ± 8.0, and 69.6 ± 6.7 mL/min per 1.73 m², which decreased to 66.5 ± 7.8, 66.5 ± 8.3, and 67.4 ± 6.4 mL/min per 1.73 m², respectively, after 12-24 mo. The changes in serum creatinine levels and GFRs were not significantly between the NaP, PEG, and control groups (P = 0.992 and P = 0.233, respectively). Using multivariate linear regression analysis, only the baseline GFR was associated with the change in GFR (P < 0.001). Indeed, the bowel preparations were not associated with the change in GFR (P = 0.297).

CONCLUSION: NaP bowel preparation in subjects with normal renal function was not associated with renal injury, and NaP can thus be used safely for screening colonoscopy.

Clinical trial: the efficacy and safety of routine bowel cleansing agents for elective colonoscopy in persons with spinal cord injury - a randomized prospective single-blind study

BACKGROUND

As difficulty with evacuation is a common occurrence in individuals with spinal cord injury, preparation prior to colonoscopy may be suboptimal and, perhaps, more hazardous.

AIM

To assess the safety and efficacy of bowel cleansing regimens in persons with spinal cord injury.

METHODS

Randomized, prospective, single blind study comparing polyethylene glycol (PEG), oral sodium phosphosoda (OSPS) and combination of both for colonic preparation prior to colonoscopy in subjects with spinal cord injury.

RESULTS

Thirty six subjects with eGFR > or =60 mL/min/1.73 m(2) were randomized to PEG or OSPS or PEG+OSPS. Regardless of bowel preparation employed, >73% of subjects had unacceptable colonic cleansing. No subject in the OSPS preparation group demonstrated a decrease in eGFR or an increase in serum creatinine concentration from the baseline. OSPS and PEG+OSPS preparations caused a transient change in serum potassium, phosphate and calcium concentrations, but no change in electrolytes was noted in the PEG group.

CONCLUSIONS

Neither OSPS alone, PEG alone nor their combination was sufficient to prepare adequately the bowel for colonoscopy in most patients with spinal cord injury. However, administration of OSPS and/or PEG appears to be safe in the spinal cord injury population, provided adequate hydration is provided.

Acute phosphate nephropathy

Acute phosphate nephropathy (APhN) is a clinical pathological entity characterized by acute and subsequent chronic renal failure following exposure to oral sodium phosphate (OSP) bowel purgatives. Renal biopsy findings include acute and chronic tubular injury with prominent tubular and interstitial calcium phosphate deposits. Risk factors for APhN include older age, female gender, hypertension, chronic kidney disease (CKD), and treatment with angiotensin converting enzyme inhibitors, angiotensin receptor blockers, and diuretics. The pathomechanism of APhN involves hypovolemia-induced avid proximal salt and water reabsorption, delivery of a large phosphate load to the distal nephron, and precipitation of calcium phosphate in the distal tubule and collecting duct. To date, 37 cases of biopsy-proven APhN have been reported, and epidemiologic studies have produced inconsistent results regarding the incidence of acute kidney injury (AKI) following the use of OSP purgatives. OSP solution was withdrawn from the market in December of 2008, but OSP tablets, offered by prescription only, remain available. Prevention of APhN is best achieved by avoiding OSP in high-risk patients, aggressive hydration before, during, and after OSP administration, minimizing the dose of OSP, and maintaining a minimum of a 12 h interval between OSP administrations.

Colon cleansing before colonoscopy: does oral sodium phosphate solution still make sense?

Oral sodium phosphate (NaP) solution has been withdrawn from the market in the United States but remains available for over-the-counter purchase for bowel preparation for colonoscopy in Canada. The present review summarizes recent data regarding the renal toxicity of oral NaP as well as its efficacy and tolerability relative to other preparations. Given the availability of effective alternatives to NaP solution, its use for colonoscopy preparation in Canada should be limited. Candidate patients for oral NaP solution should be assessed for eligibility and preparation instructions should adhere to the current recommendations for maximizing the safety of oral NaP.

Randomized study comparing two regimens of oral sodium phosphates solution versus low-dose polyethylene glycol and bisacodyl

PURPOSE

Low-volume bowel preparation regimens for colonoscopy are reported to improve patient acceptance and compliance. We sought to compare the bowel cleansing efficacy, tolerability, and acceptability of three low-volume regimens: an oral sodium phosphates solution 45/45 ml (NaP-45/45), a reduced-dose oral sodium phosphates solution 45/30 ml (NaP-45/30), and polyethylene glycol plus bisacodyl (PEG-2L).

RESULTS

A total of 121 patients were evaluated (mean age 55.2 +/- 8.9 years). Bowel cleansings rated as excellent and good were significantly different among the groups: NaP-45/45 = 98%, NaP-45/30 = 88%, and PEG-2L = 76% (P < 0.04). Side effects were not significantly different except for greater thirst in the NaP-45/45 group (P = 0.001) and increased vomiting in females using PEG-2L (two-tailed interaction, P < 0.10). Willingness to retake the preparation was higher among the sodium phosphates regimens (88, 95, and 73%, respectively; P = 0.019).

CONCLUSIONS

Better cleansing and willingness to retake the regimen was achieved with the oral sodium phosphates solutions than with polyethylene glycol plus bisacodyl.

Bowel preparations for colonoscopy: a review

PURPOSE

The mechanisms of action, clinical efficacy, tolerability, and safety of two major classes of bowel purgatives, poly-ethylene glycol- electrolyte lavage solutions (PEG-ELSs) and sodium phosphate preparations, are reviewed.

SUMMARY

PEG-ELSs are osmotically balanced preparations that promote bowel cleansing through the ingestion of nonabsorbable fluid. Sodium phosphate preparations are hyperosmotic purgatives that promote bowel cleansing by osmotically drawing fluid into the bowel lumen for evacuation. Studies suggest that 2-L PEG-ELS regimens are generally as effective as and more tolerable than full-volume PEG-ELS preparations. Studies have also found that sodium phosphate tablets may provide a more tolerable alternative to PEG-ELS regimens and traditional sodium phosphate products without compromising bowel cleansing efficacy. Proper renal function plays a particularly important role in avoiding potential safety issues related to sodium phosphate-induced shifts in the fluid and electrolyte balance. Preventing dehydration in patients undergoing bowel preparation can prevent severe adverse events, regardless of the purgative administered. Optimizing the process of bowel preparation involves administering proper purgative choices in appropriate patient populations. Moreover, patient education and compliance with preparation instructions, including correct dosing and adequate hydration, may reduce the risk of adverse events and serious complications.

CONCLUSION

Although next-generation PEG-ELS and sodium phosphate products are well tolerated and preferred by patients over traditional bowel preparation regimens, safety issues remain a concern for both purgative classes. Sodium phosphate preparations are generally more effective and better tolerated than PEG-ELS formulations but should be administered with caution in patients with preexisting or at an increased risk for electrolyte disturbances.

Drug-induced Kidney Disease – Pathology and Current Concepts

The kidneys can be damaged by a large number of therapeutic agents. The aim of this article is to discuss the pathological features of drug-induced renal disease as diagnosed by kidney biopsy. The literature is reviewed and cases seen by the authors that have a known drug association are analysed. Mechanisms of injury are varied and all renal structures may be affected. The tubulointerstitial compartment is most frequently involved, but glomerular and vascular lesions are seen in a significant proportion of cases. Key words: Drug, Kidney, Nephrotoxicity, Pathology

Risk of further decline in renal function after the use of oral sodium phosphate or polyethylene glycol in patients with a preexisting glomerular filtration rate below 60 ml/min

OBJECTIVES

The aim of this study was to estimate the risk of further creatinine increase in patients with preexisting renal disease after the use of oral sodium phosphate (OSP) versus polyethylene glycol (PEG), and to study usage patterns of OSP in relation to renal function.

METHODS

A cohort study was done using clinical records and electronic patient information from the Henry Ford Health System (HFHS) in patients who had used either OSP or PEG for colonoscopy between February 1999 and April 2006. Among patients with an estimated GFR < 60 ml/min before colonoscopy, we identified cases with an unexplained creatinine increase of > or = 0.5 mg/dl within 14 days after colonoscopy.

RESULTS

We identified 7,971 OSP and 1,511 PEG users. Relative use of OSP versus PEG decreased from 88.0% before 2004 to 48.4% in 2006. 70.2% of OSP users had no recorded creatinine determination within 60 days before colonoscopy, and this proportion did not decrease over time. The study population included 317 patients with a baseline GFR < 60 ml/min, and we identified one case with an unexplained creatinine increase > or = 0.5 mg/dl among 191 PEG users (0.5%) versus eight cases among 126 OSP users (6.3%). Unadjusted and adjusted relative risk estimates on comparing OSP with PEG were 12.1 (95% CI, 1.5-95.8) and 12.6 (95% CI, 1.5-106.5), respectively.

CONCLUSIONS

In patients with preexisting renal disease, OSP use was associated with an increased risk of aggravated renal dysfunction versus PEG. Creatinine measurement with GFR estimation should be done before OSP administration in order to avoid its use in patients with renal disease.

Is bowel preparation before colonoscopy a risky business for the kidney?

Acute phosphate nephropathy after bowel preparation with oral sodium phosphate (OSP) for colonoscopy has emerged as an important clinical entity. In 2004, five cases of nephrocalcinosis and irreversible renal failure after bowel preparation with OSP were reported. More recently, several retrospective studies have shown that the incidence of acute kidney injury after OSP use is in the range of 1-4%, similar to the incidence of contrast nephropathy in the general population. The degree of renal failure is not generally as severe as in the first reported cases, but irreversible damage can still occur. Millions of people worldwide undergo screening colonoscopies for colon and rectal cancer after the age of 50, so careful patient selection and monitoring for possible complications is essential when OSP is used. In addition to educating patients about the possibility of renal damage, physicians should routinely watch for considerable weight loss during bowel preparation and correct the fluid deficit as needed. Carrying out a renal function panel, which includes serum phosphorus level, is prudent after colonoscopy. Alternative bowel cleansing agents are needed because calcium phosphate precipitation is inevitable after OSP use even in the normal kidney.

Adverse renal and metabolic effects associated with oral sodium phosphate bowel preparation

Colorectal cancer can be prevented by the removal of adenomatous polyps during screening colonoscopy, but adequate bowel preparation is required. Oral sodium phosphate (OSP), an effective bowel purgative, is available over the counter and requires a substantially lower volume than polyethylene glycol-based preparative agents. Accumulating reports implicate OSP in electrolyte disturbances as well as acute kidney injury (AKI) in a syndrome termed phosphate nephropathy (a form of nephrocalcinosis). Despite published case reports and case series, the actual incidence, risk factors, and natural history of phosphate nephropathy remain largely undefined. Several recent observational studies have provided new information on these important issues while supporting a link between OSP and acute phosphate nephropathy as well as the development of chronic kidney disease in elderly patients, many of whom had a normal serum creatinine at the time of OSP ingestion. This review summarizes current knowledge about the renal complications of OSP, risk factors for its development, and the pathophysiology of acute and chronic kidney damage in nephrocalcinosis.