APOL1 risk alleles and renal transplant function: time for Mission APOLLO

APOL1 is the newest addition to the list of CKD risk factors- possibly never before in the history of nephrology has a gene associated with such a high odds ratio with disease - above 7 for hypertensive CKD & >10 for FSGS. A gene that confers heterozygous survival advantage when present as a single variant allele, but two variants lead to high CKD risk - APOL1 on chromosome 22. A similar picture of the survival advantage is seen with sickle cell disease. For more on the fascinating story of APOL1 itself, see this open access review, NephMadness coverage from 2015, and the NephJC coverage of a more recent research.

A recent study has shown increased risk of CKD and subsequent ESKD in a population of black kidney donors with high risk APOL1 genotype. High risk is defined as presence of two variants (G1 and G2 – so any combination G1/G1, G1/G2 or G2/G2 is high risk) and was associated with faster progression of renal dysfunction and lower pre- and post-donation eGFR (pre-eGFR 98 versus 108; p= 0.03 and post-eGFR 58 versus 68; p=0.01) over a median follow up of 12 years. The second part of the study involved comparison between these donors and non donors from the CARDIA cohort (Coronary Artery Risk Development in Young Adults), based on APOL1 genotype status. After median 11 years, there was no difference in eGFR decline between the two groups when segregated based on genotype status, indicating that it was the genotype which influenced the eGFR decline and not the donation. Other salient features in the study were:

• 2 donors in the high risk group developed ESRD at 10 and 18 years of donation (11 %, but there were only 19 in this group).
• 78% of the donors were first degree relatives of the recipients. So the fact that a substantial percentage of donors were at risk of subsequent renal disease in this study does raises some valid concerns. Should all black donors be genotyped before transplantation?

An original article published in the Annals of Surgery recently studied eligible kidney donors (n=3438) from the CARDIA cohort of 1985-86 and deduced some risk scores based on the clinical and genetic profile of this population. They projected the 25 year pre-donation risk of CKD (eGFR <60ml/min) or microalbuminuria or macroalbuminuria in an 18 year old and a 30 year old potential donor. This risk is for people with no clinical risk factors (family history/pre-hypertension/diabetes). The risk increases significantly if any of these risk factors are present. See the table for some examples (EA – European American; AA – African American):

How about the risk to the recipients? Case reports have shown development of post transplant FSGS in siblings and monozygotic twins, both in the donor and in the recipient. Data from other studies have shown increased risk of allograft failure in recipients if the donor has a high risk genotype. All these data clearly point to the risk of CKD and subsequent ESKD in AA individuals (both donors & recipients) following transplantation. This brings us back to the most pertinent question, should people of African ancestry be genotyped for APOL1 prior to transplantation? The present studies are not well equipped to answer this question. Though it may seem that one obviously should screen (‘11% of donors with high risk variants develop ESRD!’ ‘High risk variants increase graft failure in recipients!’), lets pause and consider this. We know that live donor transplantation is the modality that offers the best survival. We also know that minorities, in US as well as in UK and elsewhere, have a lower rate of live donor transplantation (see NephJC coverage of a recent JAMA study and the ATTOM study, as well as the NephMadness coverage from 2017 on disparities in transplantation). So, would genotyping worsen the disparity? Is our fate inextricably written in our genes? Enter APOLLO.

APOLLO, APOL1 Long-Term Kidney Transplantation Outcomes Network, is a prospective study aimed at  genotyping donors and recipients in transplants involving recent African ancestry in United States and monitoring long term follow up. This will shed more light on this question and even might have a decisive influence on the present KDRI (kidney risk donor index), replacing the race column with APOL1 genotype. We await this important piece of work with interest.

Post by Sriram Sriperumbuduri

Primary Membranous Nephropathy

The landscape of Primary Membranous Nephropathy (PMN) has significantly changed over the last decade. Most of what we now understand about the pathogenesis of PMN is derived from the Heymann Nephritis model in rats. In 1959, Dr. Walter Heymann published this landmark article, which established the autoimmune nature of the disease. In the late 1970s, two groups (Dr. Couser et al in Boston and Dr. Van Damme et al in the Netherlands) established that the deposits of Heymann Nephritis were not from circulating immune complex trapping, but due to in situ formation. The rat antigen was eventually identified as megalin. The human antigen equivalent remained unknown until much later. Finally, 2009, Salant, Beck et al found that 70% of adult patients with “idiopathic” membranous nephropathy had antibodies against M-type phospholipase A2 receptor (PLA2R), a transmembrane glycoprotein found on podocytes. Soon after, another podocyte transmembrane glycoprotein called thrombospondin type-1 domain-containing 7A (THSD7A) was discovered (See NEJM 2014; 371(24):2277-2287).

Now, approximately 85% of PMN is found to be mediated by anti-PLA2R or anti-THSD7A, with still 15% of PMN “idiopathic”. With a serologic test for anti-PLA2R now commercially available as well as a biopsy immunofluorescent stain, the diagnosis and management of patients with PMN has been completely revamped.

For more on this discussion, please join us in the next GlomCon Interactive Fellows’ Curriculum on Tuesday, July 17th at 11 am eastern time. We will be walking through a case scenario as we review several different aspects of PMN.

To join the meeting go to: https://glomcon.zoom.us/ and select 'Join a Meeting'. Enter the Meeting ID into the web site (or connect directly from your Zoom app).

Meeting ID: 394-801-817

You HAVE to be logged into ZOOM to join the session. You may either create a free ZOOM account, or sign in through a Google or Facebook account (if you have one).   

Alternatively, use your institution's 'Polycom' system, enter IP address:

US West: 162.255.37.11

US East: 162.255.36.11

Europe: 213.19.144.110

Then, enter the Meeting ID: 394-801-817

Anemia post-transplantation

A 20-year-old female had Henoch-Schönlein purpura since age 9 leading to ESRD. She underwent kidney transplantation in 2018 from a live donor (mother) and received induction immunosuppression with thymoglobulin (100 mg once) followed by maintenance with tacrolimus (6 mg twice a day), mycophenolate sodium (720mg twice a day) and prednisone (30mg daily). The patient was discharged 5 days after surgery, with creatinine 0.9 mg/dL with tacrolimus trough level of 9.2 ng/mL.

Before surgery, the hemoglobin level ranged from 12.1g/dL to 11.6g/dL. At the time of medical discharge Hb was 9.8g/dL. During the follow-up, the patient was asymptomatic, with no increase in creatinine level and with good trough tacrolimus level (range of 8-12 ng/ml). However, at 2 months post-transplant, she developed worsened anemia with a hemoglobin of 6.1g/dl. At this time, the patient remained asymptomatic. She was then referred to the ED.

The exams at the time showed: hemoglobin 6.2 g/dL; reticulocyte 0.29%; haptoglobin 89 mg/dL; LDH 220 U/L. Subsequently, a bone marrow aspirate was performed and showed a giant pronormoblast with prominent nuclear inclusions, characteristic of parvovirus B19 infection.(FIGURE 1)

The patient received 2 doses of intravenous immunoglobulin (1g/kg/day) and was switched from tacrolimus to everolimus.

Anemia is a very common finding during post-kidney transplant consults. It is not uncommon to have patients that remain with anemia in the first 3 moths after the procedure. Read more here. (FIGURE 2)

The lack of large case series would make us imagine that parvovirus B19 infection after kidney transplant is rare. The incidence in post-transplant is not easy to estimate (range from 1-10%) and mostly occur in the first year, suggesting donor transmission, as described here.  Also, anemia is a common finding after kidney transplant and may have many other differentials that would appear higher on the list, including drug-induced myelosuppression and bleeding. Additionally, parvovirus B19 surveillance is not performed in routine clinical practice.

 A 2006 review from Mayo Clinic showed that among 98 patients with PVB19 infection after transplantation, 54% were kidney transplants, 9% liver transplants, 12% heart or lung transplants and 24% autologous or allogeneic HSCT recipients. The mean age of the patients was 35.2 ± 17.1 years. The majority (58%) were male. The median time to onset of parvovirus B19 disease was 1.75 months (range, 1 week–96 months) after transplantation. Overall, this study suggested that kidney recipients are in particular susceptible to parvovirus infection and that timing of presentation is variable though highest in the early period post-transplant. (FIGURE 3). Finally, it is reasonable to think that the magnitude of parvovirus B19 infection is underestimated.

Dr Felipe Paste
São Paulo, Brazil

Free eBook on Acid Base

Benjamin Abelow's book: The Painless Guide to Mastering Clinical Acid-Base is available again as a free download in recognition of the new class of incoming nephrology fellows. We have highlighted this book in the past. It is a great primer on Acid-Base for trainees - easy to read and very informative. 

The details on how to access the offer are below. It will be available for a limited time only. 

To download a free ebook copy of The Painless Guide to Mastering Clinical Acid-Base, follow the numbered steps below. You will be downloading directly from Amazon, where you can also read editorial reviews of the book. The ebook is a Kindle file type. Apps are available for all devices: phones, tablets, and laptops, including Apple, Android, and Windows. The ebook will be available for free for three days, Sunday, July 8 - Tuesday, July 10. 

To Download:

1.  During the period Sunday, July 8 - Tuesday, July 10 click here: https://www.amazon.com/Painless-Guide-Mastering-Clinical-Acid-Base-ebook/dp/B06XRM56TY

2.  Be sure you’re on the page for the e-book (Kindle) edition, not the paperback. During the three days in questions, it should say, "Kindle Price: $0.00."

3.  Click on “Buy now with 1-Click.” (Do not click on “Read for Free,” as that leads to the “KindleUnlimited” program, which has a monthly fee.)

4.  If you don’t already have a Kindle app on your device, you can easily download one. Just go to your usual on-line source for apps and search “Kindle.” The apps are available for all types and makes of devices. You can download to multiple devices associated with your Amazon account.

Congratulations New Fellows

Congratulations to the incoming class of Nephrology fellows!

I’m one of you! I went to way too many interviews and had the pleasure of meeting several passionate nephrologists and fellows. I’m confident that there are a lot of amazing, talented physicians among us.

While we may not meet each other again until our 2nd year of fellowship, I was hoping we could plan to build a stronger social network to stay abreast of the year ahead of us and affect change.

As a start, I wanted to point out a few resources available for us to use once we’re fellows in July of 2018: 1. Societies: Sign up to ASN, NKF and ISN. It’s free for fellows and gives you access to journals [Like JASN and CJASN through ASN; KI through ISN], NephSAP and grants for travel and research. ASN allows you to sign up for free as a resident, so, you could start there for now. 2. Travel Grants: Once you enter your second year, you’ll be able to go to several conferences. Here’s a running list of courses and conferences, several of which offer travel grants for fellows. [P.S: If you’re a medical student/resident, ASN and NKF have travel grants for conferences for you too!] 3. Grants. As your research interests develop, feel free to look here for opportunities for funding. 4. Social media. Please join the Renal Fellow Network blog [this one right here!], twitter and the NSMC [Nephrology Social Media Collective]. While the NSMC has already enlisted their amazing group of interns, applications will be open again for the next year. For this year, NSMC was accepting applications till January 1st, 2018.

There are several challenges that I’m aware of facing us in nephrology today. I’m going to list a few in the hopes that you will find some of these areas to be worth your while to work on in the near future.

As I write this, health policy in the field of nephrology is changing. For instance, a bill was introduced in October, 2017, which, on the surface appears to provide integrated care for dialysis patients. However, I have some concerns related to the bill pertaining to its ability to limit small and medium sized dialysis organizations from functioning, in addition to further severing the transitions of care between CKD and dialysis for patients. We need more physicians discussing bills like this in private and in public to help advocate for the future of our profession as well as our patients. As a group, we can make a difference.

The reputation of nephrology among medical students and residents has also changed over the last few years. Currently, I do not believe there are consistent websites or resources for interested applicants to look at to make an informed decision on nephrology. While there are a lot of negative things that are being said about our field, you are all here for a reason. I hope that we can use this blog to reinforce our reasons and convince future applicants to make the right choice for their career, whatever it may be.

One of the easiest and productive ways for us to make a difference in health policy, education, recruitment, clinical research and our career as nephrologists is to improve our collective social presence. This is why I think it’s important for you to consider joining this blog or the NSMC, if you haven’t already. [links above]

The Renal Fellow Network blog was created to be by the fellows and for the fellows. I hope you will join me in keeping that promise. Posted by Yuvaram Reddy

A Nephrology Fellow’s Guide to Billing/Coding

Nephrology fellows - you don’t want to miss the Siegfried & Roy of Billing & Coding @ParinMakadia @drirfanagha at Nephrology Business Leadership 2018 https://t.co/2GtrF6hBCM @NBLUniv @Nephro_Sparks @DiMiRenalMD @DallasRenal pic.twitter.com/XaD2gmuJ1U

— Samir Nangia MD CPE (@SamirNangia) January 19, 2018

I'm a second year Nephrology fellow and have been very fortunate to receive dedicated education on the business of medicine. During my time at Baylor, I was the inaugural fellow of the business track; a track designed by our program director Dr. Raghavan for fellows interested in learning key concepts of business of nephrology.

A part of the business track curriculum, it requires fellows to attend a national conference on the topic of business. I chose to attend to Nephrology Business Leadership University (NBLU) in August of 2017. This conference is a crash course into understanding key concepts on how to be a successful nephrologist in private practice.

Personally, one of the most interesting courses at NBLU was on Billing/Coding taught by Dr. Parin Makadia and Dr. Irfan Agha. This course was effective and unique as it was taught from coder’s point of view. After returning from my time at NBLU, I was inspired to write a billing/coding guide as my scholarly project for the Baylor Business Track. Using this link below - you will be able to view each section of a physician note and the necessary documentation needed to bill at an appropriate level.

Click here for the document

I hope this guide help all graduating fellows/residents going into practice, good luck!

Natasha N Dave
Baylor Nephrology Chief Fellow
Houston, TX

MAKE this a better outcome

The PRESERVE Trial, which was recently published in the NEJM was a large study of a variety of preventive measures for contrast-induced nephropathy. It used a 2x2 factorial design to test the efficacy of NaHCO3 vs. normal saline and n-acetylcysteine vs placebo for the prevention of CIN. The trial was stopped early as there were no signals that any of the treatments were better than any other suggesting that the best treatment for CIN right now is likely the use of both saline and the smallest possible quantity of low-osmolar contrast. The overall decline in the rates of CIN over the last few years are likely more related to the change in the way that contrast is used rather than any special benefit that we were imparting using novel measures to prevent CIN.

The trial was enriched to try and increase the rate of AKI - it included patients with an eGFR between 15 and 45 (non-diabetic) increasing to 60 in diabetics. The overall mean eGFR was 50 so perhaps there were not quite enough patients with advanced disease but given that more than 5000 patients were included in the study, it is hard to really draw the conclusion that it was underpowered for subgroups. Patients with AKI were also understandably excluded and it is unclear what the risk is in this subgroup of patients.

The other thing that was really interesting about this study was the outcome used. Traditionally, studies on CIN have used AKI as the outcome. This being defined typically as some change in creatinine in either absolute or percentage terms. The current AKIN definition of stage I AKI is a 0.3mg/dl increase. This study used an increase of 0.5mg/dl. AKI of this magnitude has been shown in large studies to be associated with adverse outcomes including increased length of hospitalization and mortality but there is always a lingering question about how clinically significant it is in the long run when it tends to resolve in most patients.

Because of these concerns, there has been a recent move towards using MAKE (major adverse kidney events) as a composite outcomes in trials of kidney disease. This concept, stolen somewhat from the cardiology literature is thought to be more meaningful as it results in real, long-term harm to patients. In this study, the authors chose MAKE90 - a composite of death, need for dialysis and permament 50% increase in creatinine at 90 days as the outcome. Overall, approximately 9% of patients had AKI following contrast administration and about 4.5% had a MAKE90 event (2.5% died, 1.5% required dialysis and 1% had a permanent decline in renal function). Another thing I would take away from this study is that we should not let people tell us that CIN does not exist (which I have heard around the halls more often than I like over the last year or so).

Overall, I think this move towards MAKE as an outcome in clinical trials is a welcome one. It is a well defined outcome that demonstrates clear harm to patients. There is no reason to chuck AKI out completely - it is a perfectly good secondary outcome - but in terms of figuring out who are the patients most likely to benefit from interventions in the future, MAKE is the way to go

Minimal Change Disease

The next session of GlomCon's Nephropathology Essentials will be held this Tuesday, June 12th at 11 am EDT. Dr. Helmut Rennke will be leading the session which will focus on Minimal Change Disease and FSGS (see below for session details).

Minimal change disease (MCD) is the most common cause of nephrotic syndrome in children > 1 year of age. Adult MCD is much less common but remains an important cause of nephrotic syndrome in this population. Here are some quick points to remember in adults with MCD:

• Bimodal presentation: young children and very old adults
• The slight male predominance (2:1) found in children disappears in the adult population
• More common in atopic patients
• Clinical presentation: Abrupt onset of edema, nephrotic range proteinuria, severe hypoalbuminemia and severe hyperlipidemia
• There is a long list of secondary causes of MCD, but important ones to remember include: NSAIDs, Lithium, and Lymphoma 
• Microscopic hematuria is seen in 10-30% of cases
• AKI is present in 20% of cases (higher risk in older age, males, and presence of HTN)
• Best initial treatment is corticosteroids 
• Prednisone 1 mg/kg (maximum 80 mg) daily or alternative-day dosing of 2 mg/kg (max 120 mg)
• Time to complete remission is much longer in adults, requiring 12-16 weeks
• Relapse rates in adults with MCD are high

This is reviewed nicely in the following articles

1) CJASN 2017; 12:332-345

2) JASN 2013; 24:702-711

MCD was also covered in this past GlomCon session. For further on both MCS and FSGS pathology, make sure to join the session on Tuesday.

GlomCon's Nephropathology Essentials Details:

To join the meeting go to: https://glomcon.zoom.us/ and select 'Join a Meeting'. Enter the Meeting ID into the web site (or connect directly from your Zoom app).

Meeting ID: 394-801-817

You HAVE to be logged into ZOOM to join the session. You may either create a free ZOOM account, or sign in through a Google or Facebook account (if you have one).  

Alternatively, use your institution's 'Polycom' system, enter IP address:

US West: 162.255.37.11

US East: 162.255.36.11

Europe: 213.19.144.110

Then, enter the Meeting ID: 394-801-817

Posted by: Pravir Baxi, Rush University Medical Center

The perils of Gabapentin

One of the things that I always highlight when teaching fellows and residents is the importance of appropriate drug dosing for patients on dialysis and one of the drugs that is most often inappropriately dosed in my experience is gabapentin. Today, an article in JASN highlights again the importance of not overusing this drug in the dialysis population. 

Gabapentin and pregabalin are often used in patients with CKD primarily to treat neuropathic pain and restless leg syndrome and given the high prevalence of diabetes in this population, the proportion who receive these drugs is very high. In patients with normal renal function, the maximum dose of gabapentin is 3600mg daily in divided doses. However, gabapentin is renally cleared and so the dose needs to be adjusted according to the GFR. For patients on dialysis, the recommended dose is 100-300mg post dialysis on dialysis days only. However, this is routinely exceeded in clinical practice. 

The study in JASN looked at medicare prescriptions for gabapentin and pregabalin in dialysis patients examined the relationship between the doses used and a variety of outcomes including altered mental status, falls and fractures. 20% of the dialysis population received at least one prescription for these drugs in 2011. Even at the lowest doses (less than 300mg daily), there was an association between the use of these drugs and AMS and falls while doses greater than 300mg daily were associated with a 40% increase in the risk of fracture. Similar results were found for the higher doses of pregabalin. 

Of course, this was an observational study and there may have been unmeasured confounders that may have biased the results but the authors did account for other medications that can increase the risk of falls. 

Overall, this should serve as a reminder to the community that we need to more carefully police the dosing of medications in our dialysis population, particularly when they are admitted to hospital.

GlomCon Nephropathology Essentials

The goal of the GlomCon Teaching Platform is to enable Nephrologists, Nephropathologists, and trainees in Medicine, Nephrology, and Pathology to connect with each other to 1) Discuss challenging cases, 2) Share clinical experiences and 3) Obtain the expertise of participating faculty and invited speakers. Access to this resource is completely free!

Going forward, every Tuesday (same time weekly, 11am EDT) there will be a case-based conference, fellow's interactive conference, or renal pathology seminar.

You are invited to the inaugural session of GlomCon Nephropathology Essentials on Tuesday, June 5th at 11 am EDT. The first session will be led by Dr. Isaac E. Stillman and will focus on the basic principles of renal pathology.

For more on the Nephropathology Essentials webinars, visit: https://glomcon.org/nephropathology-essentials/

To join the meeting go to: https://glomcon.zoom.us/ and select 'Join a Meeting'. Enter the Meeting ID into the web site (or connect directly from your Zoom app).

Meeting ID: 394-801-817

You HAVE to be logged into ZOOM to join the session. You may either create a free ZOOM account, or sign in through a Google or Facebook account (if you have one). 

Alternatively, use your institution's 'Polycom' system, enter IP address:
US West: 162.255.37.11
US East: 162.255.36.11
Europe: 213.19.144.110
Then, enter the Meeting ID: 394-801-817

The Role of the Gut for Potassium Homeostasis in CKD

Recently the FDA approved one of the newer exchange resins (Lokelma, ZS-9) for the treatment of hyperkalemia. (Veltassa, Patiromer), a calcium based cation exchange resin, was recently developed and approved since 2015 for the treatment of hyperkalemia. These two new drugs, which each have large randomized placebo controlled trials confirming their effectiveness, now seem bound to replace the ancient but much experienced Kayexalate (Sodium Polystyrene Sulfonate; SPS) for the management of hyperkalemia. However, they are not approved in Canada and their cost makes them less enticing options in a publicly funded health care system. Also, what about safety concerns? SPS has been used since the 1950s, however it took decades for case reports to come out possibly linking fatal colon necrosis to Kayexalate use. This association remains hotly debated. A systematic review in 2013 found a total of 58 cases of biopsy confirmed bowel injury that were “possibly” related to SPS use based on the WHO causality criteria. Interestingly, these cases were not limited to patients using SPS with sorbitol, nor to the post-operative population as was once thought to be the major risk factors for adverse GI events from SPS. On the other hand, a retrospective single-centre review over a 10 year period found only 3 cases of colon necrosis among 2,194 patients having received SPS. When they compared this incidence of colon necrosis to control patients having not received SPS, they found a non-significant RR of 2.10 (0.66-6.64; P=0.2). Many nephrologists will argue that SPS has a long standing proven track record and that colon necrosis is such a rare side effect that it is unlikely to be related. While no one knows if this is truly the case, the uncertainty surrounding this issue is one of the major reasons that led to the development of the newer exchange resins: ZS-9 and patiromer.

Before praising and widely accepting these newer, expensive products, would it not be wise to use the same caution we would for SPS? It can take years for such a rare adverse event as colon necrosis to manifest itself, how do we know we won’t be facing this GI safety issue 5 to 10 years from now?

Perhaps we could look for other ways of trying to enhance GI elimination of potassium.

--> BK-channel in colon enterocyte (Source: Sandle et al. QJM. 2010 Feb;103(2):85-9)    
The colonic enterocyte has an ability to excrete potassium in stool. This may be an important physiologic property in patients with advanced CKD who lose the ability to renally excrete potassium. In fact, patients with ESKD are known to have a greater excretion of potassium in their stool compared to individuals with normal kidney function. An important transporter involved in this process is the BK-channel located on the apical side of the colonic enterocyte within the colon crypts (see Figure). This channel is responsible for actively secreting potassium in the GI lumen. Aldosterone stimulates this channel, enhancing K secretion in the stool, similar to its effect in the kidneys. In fact, a study in the 1970s of patients suffering from acute cholera showed that within 12 hours of receiving a single dose of 100mg of spironolactone, there was a significant decrease in stool loss of potassium and an increase in stool loss of sodium. This likely is a major reason explaining why anuric patients with ESKD may still have from hyperkalemia if given RAAS blockade. The BK channel will also be stimulated by various diarrheal states such as Ogilvie’s syndrome, villous adenoma and certain laxatives such as bisacodyl. Bisacodyl is a stimulant laxative which enhances peristalsis through parasympathetic nerve activation, but also stimulates cAMP production within the colon enterocyte. This cAMP is thought to enhance K excretion via the BK-channel. A study performed in 2005 used immunohistologic analysis of colonic enterocytes in patients with ESKD and showed that BK-channels are upregulated in these patients compared to controls with normal kidney function. The upregulation of BK-channels probably represent an adaptation to chronic potassium load in order to maintain homeostasis. Interestingly, a small study in 2003 tested the effect of Bisacodyl on potassium in patients with ESKD. Eight controls normal kidney function and 13 patients with ESKD were given Bisacodyl 5-10mg PO titrated to achieve 2 soft bowel movements per day and these were compared to 5 ESKD patients given lactulose 10ml PO titrated also to 2 soft bowel movements per day. After 2 weeks of treatment, they found that the ESKD patients with Bisacodyl had a significant decrease in potassium from 5.9 to 5.4mmol/L whereas the controls given Bisacodyl and the ESKD patients given lactulose had no change in potassium values after 2 weeks of therapy. This suggests that Bisacodyl increases potassium excretion in the stool in patients with ESKD through a mechanism not simply related to its laxative effect, but likely through stimulation of the BK-channel of the colonic enterocyte. It is unfortunate that no further studies have looked into this therapeutic option for maintaining potassium homeostasis in patients with advanced CKD. Unfortunately, we don’t know if Bisacodyl would work as well in the non-dialysis population since we could expect these patients may not have as upregulated BK channels as in ESKD who are faced with more chronically elevated potassium loads. However, this would be an interesting study to pursue since Bisacodyl would be a cheap and safe way of controlling potassium in patients with advanced CKD by enhancing the body’s natural adaptation to potassium handling.

David Massicotte-Azarniouch
Nephrology Fellow
University of Ottawa