Cystinosis

Cystinosis is an autosomal recessive disease caused by a mutation in CTNS, which encodes the lysosomal transporter of cystine. Without this, cystine gradually accumulates in cells causing progressive damage. The commonest kind is “nephropathic cystinosis” which is the juvenile form and presents in infancy although there are milder adolescent and adult forms. It is a rare disease with only 6,000 sufferers worldwide.

It is characterized by the early development of fanconi syndrome with progressive loss of tubular function leading to ESRD by the age of 10. Most affected children are blond and have marked growth retardation. Corneal deposits are common and can cause blindness later in life. Patients may also have hepatosplenomegaly, muscle weakness, delayed puberty and eventual neurological disease. The adult form is more benign and usually presents with visual problems although it can lead to ESRD in some patients.

There is an effective treatment for cystinosis – cysteamine, given orally, enters the lysosomes and reacts with cystine forming a complex that can exit the lysosome and prevent build-up. It should be started as soon as the disease is diagnosed but even with this, the tubular defects often persist. However, there is a definite improvement in overall renal prognosis with this drug. So, if there is an effective treatment, why do many children with this disease still go on to require renal transplantation? There are huge issues surrounding compliance with the medication. It needs to be taken four times daily at equal intervals. More importantly, it causes severe halitosis and body odor that, for a young child, can be devastating. I had a patient a number of years ago who told me that he and his brother had to be removed from class because the problems with bad odors while on the drug and that he preferred going on dialysis and getting a transplant than remaining on the treatment. Unfortunately, at that time, he was developing severe visual problems related to build-up of cystine in his corneas.

There may be some more light at the end of the tunnel. Recently, phase III trials were completed on a new formulation of cysteamine. This can be given twice daily, has a lower total cumulative dose than the standard formulation and appears to cause less halitosis and body odor. According to the company, 40 of 41 patients enrolled in the study decided to continue the drug after the phase III period had ended. This is certainly encouraging.

As Nate mentioned previously, this should not be confused with cystinuria, a disease of amino acid transport in the kidney leading to an increased susceptibility to kidney stones.

Renal Fellow Network on ASN's Monthly Podcast: Part 2

FDA, Statin and Transplantation - A conundrum

We are facing a conundrum in post-transplant lipid management after the recent warning from the FDA, which updated the label of simvastatin. This drug is now contraindicated in patients taking cyclosporine due to the potential for liver dysfunction and myopathy.


Just to remind you, statins are metabolized by the hepatic cytochrome P450 3A4, similarly to calcineurin inhibitors and mTOR inhibitors. In the presence of these immunosuppressive agents, statin levels are raised and risk of myopathy is increased. This danger has always existed, however, the FDA has taken a harder stance lately with creating a “contraindication”. Moreover, simvastatin doses greater than 20 mg/day are also not recommended anymore in patients receiving amlodipine, which is the vast majority of transplant recipients (this is new since prior literature solely reported non-dihydropyridine CCB like diltiazem and verapamil as important interactions). Nonetheless, there is nothing listed when simvastatin is co-administered with tacrolimus, sirolimus and/or everolimus. However, the potential for a similar drug-interaction and adverse events exists. So what do we do?


First, let’s do a brief review of dyslipidemia post-transplantation. Elevated cholesterol levels are very prevalent in transplant recipients reaching above 80% of kidney recipients in some reports. Immunosuppressive drugs play a major role, with all the following classes glucocorticoids, calcineurin inhibitors (cyclosporine greater than tacrolimus) and mTOR inhibitors having deleterious effects. Among them, the effect of mTOR inhibitors is different since it causes predominantly elevated hypertriglycerides due to blockade of insulin-stimulated lipoprotein lipase.


The importance of dyslipidemia in the transplant population is related to the most common cause of death with a functioning allograft - cardiovascular disease (~40%). Similar to the dialysis data, statin trials in transplantation are limited to one prospective randomized trial (ALERT) with fluvastatin in kidney transplant recipients that showed lower cholesterol levels in the treatment arm compared to placebo, however there was only a non-significant trend towards reduction of composite cardiovascular events. Nonetheless, secondary outcomes of this trial, observational, long-term follow ups and post-hoc analyses have suggested some beneficial effects.


Most of our transplant patients are taking tacrolimus which is extensively metabolized by the cytochrome P450 family enzymes in the liver and excreted into the bile. Therefore, what should we do? Should we stop completely using simvastatin?


I think there is no straight answer here, especially since we have been using statins for a long time in combination with tacrolimus, monitoring in those settings LFTs and symptoms of myalgia. But now with the formal contraindication with cyclosporine, physicians will get more careful in prescribing even the sister CNI with simvastatin. Insurers will likely change their policies facilitating the use of other statins as well. So which statins are safe to use?


Fluvastatin and Pravastatin (both generic) have minimal drug interaction with CNIs/amlodipine and should be considered for mild hypercholesterolemia, since both are weaker statins (see strength and interconversion table above that I simplified from the FDA version). Atorvastatin should be the chosen statin for moderate-severe hypercholesterolemia, since it has increased potency requiring a lower dose and has a favorable safety profile despite some metabolism by P450. Rosuvastatin, a novel potent statin, could also be the agent of choice since it is not metabolized by cytochrome P450, though preliminary results from the PLANET trials have reported a higher risk of proteinuria when higher doses were administered. Therefore, it is wise to wait until final results are published.

The debate is open and would love to hear how others would face this dilemma.

The Renopoietic System

Early in 2009 Nate posted on work suggesting that renal tubular epithelial cells had the ability to repopulate the renal tubular epithelium after ischemia reperfusion injury. Since then, some amazing work has been done on what have been termed glomerular epithelial stem cells.




Podocytes, unlike glomerular mesangial and endothelial cells, cannot divide. However, there are a number of clinical situations such as the spontaneous remission of proteinuria in patients with membranous nephropathy and the remission of diabetic nephropathy after pancreatic transplantation that suggest that podocyte repair or perhaps even replacement via stem cells is possible.



To be termed a stem cell a cell must be capable of self renewal (the ability to go through numerous cycles of cell division while maintaining an undifferentiated state) and be able to differentiate into various specialized cell types.


Along these lines, an Italian group was able to identify candidate renal stem cells by using the cell surface markers CD133 and CD24 which are found on other adult stem cells elsewhere in the body. These cells initially were shown to be both capable of self renewal and generation of mature, functional, tubular cells with phenotypic features of proximal and distal tubules. In addition, given the right conditions these CD133 CD24 positive cells were able to become osteogenic cells, adipocytes, and cells that exhibited phenotypic and functional features of neuronal cells.


These renal stem cells are located in the urinary pole of the parietal epithelium of Bowman's capsule. In later experiments they were shown to be able to become not only renal tubular cells but also podocytes.


In the figure on the upper left from an excellent review written by the Italian group the exquisite organization of these cells is shown. The glomerular epithelial stem cells are shown in red at the urinary pole. A transitional cell population of podocyte progenitors closer to the vascular stalk, is colored both red and light blue. These progenitors differentiate only toward the podocyte lineage and lack the properties of self-renewal. The light blue cells in the vascular stalk and glomerular tuft express only podocyte markers and the phenotypic features of differentiated podocytes.


Suggested mechanisms of podocyte replacement are also shown with A) progressive differentiation down Bowman's capsule to the vascular stalk B) direct bridging by adjacent progenitor cells C) bridging by glomerular epithelial stem cells that subsequently acquire podocyte markers.


Excitingly, injections of these renal stem cells appear to attenuate proteinuria and histologic damage in experimental animal models of FSGS and renal dysfunction in experimental animal models of rhabdomyolysis. It's amazing how much has transpired since Nate's last post and hopefully, this science will help us move toward a better understanding glomerular disease and ultimately more effective treatments for our patients.

Bardoxolone - Part 2

Last year, Matt wrote a great post detailing the preliminary results of a randomized, controlled trial that had been presented at the ASN in November. It was reported that the anti-inflammatory modulator, Bardoxolone, significantly increased eGFR, in a dose-dependent manner, in type 2 diabetics treated for 24 weeks. The final results of the trial were published in June in the New England Journal of Medicine. The authors found that treatment with 25, 50 and 75mg of bardoxolone was associated with increases in eGFR of 5.8, 10.5 and 9.3 ml/1.73m² respectively. The increase in eGFR persisted 4 weeks after stopping the drug. The authors suggest that this increase in eGFR is due to the anti-oxidant and anti-inflammatory effects of the drug although the mechanism is not entirely certain at this time. Overall, the drug was well tolerated with the most common side-effects being dose-related muscle cramps, mild elevations in transaminases and hypomagnesemia.

Although this appears to be very promising, there are a number of questions that I have about this study. The use of eGFR as a primary endpoint is questionable. 98% of the patients in this study were on an ACE/ARB and, as Matt alluded to in his previous post, if you took all of these patients off the ACE/ARB, you would probably see an increase in GFR. This is not necessarily a good thing if, in fact, it is simply leading to increased intraglomerular pressure. In the paper, the authors state that the drug is similar in structure to the cycloprostenone prostaglandins. Although these are described as being primarily anti-inflammatory in nature, could they also cause afferent arteriolar vasodilatation and therefore have a significant hemodynamic effect? The authors point out that the effects persisted up to 4 weeks after stopping the drug which suggests that the effect is not entirely hemodynamic but does not exclude it. It is important to note that this increase does not appear to be related to changes in creatinine metabolism. In a prior, smaller study, the same authors reported increases in measured creatinine clearance in patients treated with the drug without any change in overall creatinine excretion.

More important is the issue of protein excretion. Microalbuminuria is the often the first sign of diabetic nephropathy and our treatments are targeted at reducing albumin excretion. In this study, bardoxolone reportedly caused a ‘slight but significant’ increase in the ACR that positively correlated with the GFR. Apart from this statement, there are no primary data in the main paper. In the appendix, the table below was published (click to enlarge):

I am open to correction but I take this to mean that the ACR was 1.4 times baseline in the placebo group but that this increased to 2.6 times baseline in the 75mg group. This was highly significant. The figure below, also from the appendix, tells a similar story but it must be pointed out that the scale on the left is a log scale such that any increase may appear less than it actually was. In a study of the progression of diabetic nephropathy, I would have imagined that the change in the ACR would be an important endpoint and would have been included more prominently.

(Click to enlarge)

All that said, the result of this study matches with animal data that suggested a protective effect for this drug in models of acute and chronic renal disease and if the increase in GFR is real and beneficial, this class of medications could revolutionize the treatment of CKD. It’s great to see potential new lines of therapy for our patients and we should look forward to the phase III trials that will apparently begin enrolling later this year.

Calcium blocker induced dependent oedema

Dihydropyridine (DHP) calcium channel blockers are notoriously associated with dependent oedema, but what mechanisms underlie the pathogenesis of this finding? Here are some explanations from a nice review I came across.


Going back to Starling’s forces governing the formation of interstitial fluid – net capillary fluid filtration is influenced by hydrostatic pressure, oncotic pressure, capillary permeability and lymphatic drainage.

Upon change in posture from lying to standing, hydrostatic pressure in the vessels of the lower extremities increases. However, this is held in check by autoregulatory mechanisms which cause protective vasoconstriction via local sympathetic reflexes and myogenic reflexes – the latter are caused by smooth muscle contractions in response to increased vessel transmural pressure.

These myogenic reflexes are mediated in part by L-type DHP sensitive calcium channels. They allow calcium influx, causing pre-capillary smooth muscle constriction, thereby reducing hydrostatic pressure in the capillary bed – the final result is guarding against increased interstitial fluid accumulation.

DHP calcium channel blockers can prevent the entry of calcium to smooth muscle cells, preventing this protective pre-capillary vasoconstriction, facilitating the formation of dependent oedema. In patients with already impaired autoregulation (e.g. diabetics) calcium blockers may be associated with more profound leg oedema than others. Of course, there are likely other factors at play, including increased capillary permeability and other local neurohormonal influences.

Hypokalaemia induced polyuria

Last time we reviewed the proposed mechanisms by which hypercalcaemia can induce polyuria. It’s important to know that hypokalaemia can also precipitate this presentation. So here are the proposed mechanisms for this scenario.

Potassium is required for the thick ascending limb NaKCl2 co-transporter to operate. Remember that potassium is recycled via the apical ROMK channel, which facilitates ongoing sodium reabsorption in the TAL and maintenance of the medullary concentration gradient. Therefore, potassium deficiency may lead to concentrating defects via this pathway, leading to polyuria.

There is also some evidence that hypokalaemia leads to impaired responsiveness to ADH. The exact mechanism is unclear, but obviously decreased responsiveness to ADH may lead to large volumes of dilute urine.

Other interesting nuggets with hypokalaemia – movement of potassium out of cells in the proximal tubule (in the setting of hypokalaemia) is balanced by inward movement of hydrogen ions. The creation of an intracellular acidosis increases ammonia production by the proximal tubular cells, which may exacerbate problems in patients with decompensated liver disease.

Chronic potassium depletion (over a month at least) in humans can cause the development of vacuolar lesions in renal epithelial cells, primarily in the proximal tubule. If the deficiency persists over a longer time period, changes including interstitial nephritis, tubular atrophy and medullary cyst formation have been described. Potential mechanisms underlying these changes may be related to altered growth factor and cytokine production, or ammonia accumulation. This collection of findings has loosely been referred to as hypokalaemic nephropathy.

A matter of protocol

The use of the protocol transplant biopsy is a divisive topic: some units see a protocol program as necessary for proper management post-transplantation, whilst others deride the whole concept as unnecessary. So who is right?

Protocol biopsies are taken at predefined intervals after transplantation regardless of kidney function. Their use is based on the theoretical benefit of detecting acute rejection, chronic allograft injury, calcineurin inhibitor (CnI) toxicity, recurrent primary disease & BK virus infiltration where the presence of these diagnoses is not evident by a measurable decline in allograft function.

Most work to date has focused on sub-clinical rejection. I detect two relevant questions here: is sub-clinical rejection sufficiently common to be an issue and is detection and treatment beneficial? In answer to the first point; the KDIGO guidelines list seven studies (on pg S31) which have looked at prevalence of sub-clinical rejection providing estimates of 13-25% at 1-2 weeks, 11-43% at 1-2 months, 3-31% at 2-3 months and 4-50% at 1 year. A number of studies have shown that sub-clinical rejection is associated with reduced graft survival and chronic allograft injury and that treatment of sub-clinical rejection may improve long-term graft outcomes.

However, the majority of these studies have been performed with cyclosporine (CsA) and azathioprine (Aza) maintenance regimes. As a result, perhaps most relevant to current practice is an RCT that randomized 240 patients on tacrolimus & MMF to biopsies at 0,1,2,3,6 months or 0 & 6 months. Rejection rates were generally low with clinical episodes seen in 10% of biopsy arm patients and 7% in the control arm. Additionally, sub-clinical rejection was seen in only 4.6% of the biopsy arm and creatinine clearance at 6 months was identical between the two groups.

So, perhaps not surprisingly, KDIGO feels only able to state that 'based on very-low-quality evidence, the benefit of performing protocol biopsies in CsA/Aza patients without induction therapy may outweigh the harm' (pg S32). This strikes me as a vanishingly small proportion of incident transplants. Taking this together with the fact that the KDIGO authors could find NO data showing a benefit in detecting sub-clinical CnI toxicity, recurrent disease, BK nephropathy etc, I would suggest that perhaps the protocol biopsy has had its day.

Hematuria: Deep on the DDx

Recently at our biopsy conference we had the case of a healthy middle aged man presented who had come to medical attention with episodes of painless gross hematuria. He had consistent rbcs on UAs, normal renal imaging, a serum creatinine of 1.1 mg/dl, 360 mg per day of proteinuria and unremarkable serologies. An extensive urologic evaluation had been unrevealing and a kidney biopsy was normal.


When the usual suspects of urologic and glomerular causes of relatively isolated hematuria (IgA nephropathy, Thin Basement Membrane Disease, Alport's Syndrome) are not around you sometimes have to go a bit deeper down the differential diagnostic list.


Along those lines RFN has had a couple of posts on some of the more unusual painful causes of hematuria including renal infarction, Loin Pain-Hematuria Syndrome and the Nutcracker Syndrome (also covered on PBF).


As mentioned, our patients hematuria was painless. He had no history of diabetes, NSAID use, infection or obstruction to implicate renal papillary necrosis. There was no travel history to suggest Schistosoma haematobium or Tuberculosis. His ethnicity made Sickle cell unlikely. He only exercised as much as the average first year renal fellow (ie not much) so exercise hematuria seemed out. The room was a little stumped.


A metabolic possibility that came up after conference was hypercalciuria and or hyperuricosuria in the absence of nephrolithiasis.


In a small series of patients without nephrolithiasis and with persistent microscopic hematuria in the setting of normal renal function, urinary protein excretion and renal imaging published in KI, hypercalciuria was defined as greater than 4 mg/kg/day and hyperuricosuria was defined as greater than 800 mg/day in men and greater than 750 mg/day in women.


37 patients were identified who fit the above description and had hypercalciuria, hyperuricosuria or both. 43% of them reported having episodes of gross hematuria in addition to their known microscopic hematuria. The authors went on to treat the entire group with HCTZ and or allopurinol with the goal of normalizing urinary calcium and uric acid excretion which was achieved in all patients. Hematuria completely resolved in 59.4% of cases.


In the discussion the authors speculated that perhaps microlithiasis was the cause of the hematuria in some of their cases. Of the patients who did not respond to lowering of urinary calcium and uric acid they all persisted with microscopic hematuria and at about a year followup a reasonable alternate cause (IgA nephropathy, Thin Basement Membrane Disease ect) was ultimately found or strongly suspected in all but four cases.


Another small case series of 12 similar patients in familial clusters was subsequently published in AJKD. Here again 30% had reported episodes of gross hematuria in addition to microscopic hematuria and all patients were able to normalize their urinary calcium and uric acid excretion through medication and dietary measures. All 12 patients were able to achieve resolution of their hematuria.

Peak or Trough?

We were recently consulted on a patient with a history of repeated admissions with pneumonia who had developed AKI following treatment with Tobramycin. It got me thinking about the mechanisms of aminoglycoside toxicity. The traditional teaching is that aminoglycosides are best administered in once daily doses in order to reduce toxicity but given the fact that this should lead to higher peak levels, it seems counterintuitive that this might prevent nephrotoxicity. However, this makes sense when you understand how aminoglycosides damage the kidneys.

Aminoglycosides are freely filtered at the glomerulus. 90% of the drug is excreted unchanged in the urine while the rest is reabsorbed in the proximal tubule. As Nate mentioned in a previous post, they bind to phospholipids in the cell membranes in the S1 and S2 segments of the proximal tubule. During ischemic episodes, there is some uptake in the S3 segment also. They are subsequently endocytosed via the transmembrane protein, megalin, and accumulate in the cytosol where they mediate their toxicity. The degree of renal damage associated with the various aminoglycosides is related to the ability of the drug to bind to these phospholipids. The more binding that occurs, the more nephrotoxicity. Gentamicin is the most toxic, followed by tobramycin, amikacin and streptomycin. The reason why once daily dosing is better is that this transport mechanism is saturatable and beyond a certain concentration, no more drug is taken up. Thus, peak levels correlate with bactericidal ability while trough levels correlate with renal (and oto-) toxicity.

Interestingly, this is similar to the mechanism of renal toxicity associated with imipenem. There have been efforts to develop a drug that could be co-administered with aminoglycosides that would inhibit their transport in the proximal tubule and thus prevent their nephrotoxic effects, but unfortunately none have been successful.

Gentamicin is made up of four components and when these are administered separately, it turns out that one of them, C2, does not appear to be absorbed as readily into the proximal tubular cells while still retaining the bactericidal ability of the whole drug. This may have potential for reducing nephrotocity in patients who are particularly at risk – i.e. pre-existing AKI or ischemia.

Renal Fellow Network the Subject of ASN's Monthly Podcast

Hypercalcaemia induced polyuria

So Leo’s post got me thinking about the pathophysiology of hypercalcaemia-induced polyuria. I wanted to share what I have learned in relation to the mechanisms of this phenomenon.


Calcium-sensing receptors (CaSR) are found on the basolateral membrane of the cells of the thick ascending limb of the loop of Henle. Binding of calcium, with subsequent receptor activation, appears to induce a downstream message to close off the luminal K channel. This in turn inhibits potassium recycling and thereby shuts off the NKCC2 cotransporter, leading to decreased reabsorption of sodium, potassium and chloride in this segment.


Following on from this, the medullary concentration gradient is diminished, leading to an inablility to concentrate urine and subsequent polyuria.


CaSR are also found on the luminal surface of cells in the inner medullary collecting duct. Activation of these, in the setting of increased distal calcium delivery, down-regulates AQP2 expression, again resulting in an inability to concentrate the urine.


Finally, there may be hypercalcaemia-induced PGE2 production in the thick ascending limb, which can further inhibit sodium chloride reabsorption.


Thankfully, the polyuria and concentrating defects associated with hypercalcaemia tend to regress with correction of the calcium levels. One caveat to this may be patients who have developed an interstitial nephritis (secondary to calcium deposition in the medulla ) from prolonged hypercalcaemia.

Post-transplant Lymphoproliferative Disease

Although the term Post-transplant Lymphoproliferative Disease (PTLD) encompasses all lymphoproliferative disorders post transplant, it generally refers to extra-nodal B-cell lymphomas due to Ebstein-Barr virus (EBV) infection. PTLD is a B-cell disease caused by iatrogenic T-cell dysfunction: in people with normally functioning immune systems, activated T-cells regulate B-cell proliferation, whereas in the transplant setting pharmacological T-cell inhibition permits proliferation of EBV-infected B-cells. PTLD is the commonest post-transplant malignancy in children, the second most common in adults and is the commonest cause of cancer-related post-transplant mortality. 


PTLD requires a high index of suspicion and must be on your radar. Early disease is often easily managed by lowering immunosuppression, but late detection is a disaster. Clinical presentations vary from a benign infectious mononucleosis syndrome to a severe malignant lymphoproliferative disorder; 3 distinct clinical syndromes are described:

1. Polyclonal B-cell proliferation with malignant transformation, widespread disease, and multiorgan involvement. This accounts for 30% of patients and presents within weeks of transplant. You’re less likely to miss this presentation, as patients are often closely monitored during this time.

2. The majority of cases (over 50%) present as an infectious mononucleosis within a year of transplant. This is due to a benign polyclonal proliferation of B cells. This is easily missed, which is a tragedy as this presentation is very responsive to lowering immunosuppression.

3. A minority present late with a monoclonal B-cell proliferation, extra-nodal disease, and visceral involvement late post-transplant.

Diagnosis is by tissue biopsy (preferably excisional biopsy), and is based on histological, cytological and microbiological evidence: lymphoproliferation that disrupts tissue architecture, oligoclonal or monclonal cell lines and the presence of EBV in the tissue. One group that deserves particular attention is EBV –ve recipients who receive EBV +ve kidneys (EBV D+/R-). This small, single-center study of 34 such patients teaches us a lot about PTLD and makes the case for closely monitoring EBV D+/R- recipients:

1. Of those EBV D+/R- recipients who were not monitored (n=6), 50% developed PTLD and lost their transplants
2. Of the remainder, 60% developed EBV viremia and had their immunosuppression reduced; only 1 developed PTLD. This underscores how efficacious reducing immunosuppression can be.
3. 6/20 with persistent viremia received rituximab; none got PTLD or lost their transplant. This needs to be replicated but is very encouraging.

Here are some PTLD management pearls:

1. The graft is a commonly affected site. Isolated allograft dysfunction can be a presentation PTLD, as is allograft dysfunction developing after an increase in immunosuppression.
2. Check EBV in all flu-like illnesses; doubly so if lymphadenopathy is present; triply so if during the first post transplant year.
3. Antivirals don’t work. EBV do not express thymidine kinase, the target of ganciclovir/acyclovir
4. Reducing immunosuppression does work, if instituted early. A typical regimen would be to cut CNI by 50%, discontinue MMF/AZA, and continue the same or 50% less steroid
5. Main risk factor is the EBV D+/R- recipient, and they need monitoring for EBV infection. Other risk factors include extremes of age, heavier immunosuppression especially anti-lymphocyte antibody use and CMV infection

PTLD: Preventable with Timely Lowering of Drugs

NSAIDs: new tricks from an old drug

A 62-year-old man with CKD stage 3 secondary to presumed hypertension presented with new-onset hypercalcemia. PTH level was low at 11 and abdominal imaging revealed a right renal mass that later was confirmed to be a renal cell carcinoma.

The most common cause of hypercalcemia of malignancy is secretion of PTH-related peptide, followed by increased bone resorption due to bone mets and increased 1-alpha hydroxilase activity by the tumor (similar to granulomatous disease).

His workup was remarkable for iCa 6.3, total Calcium 11.5, PO4 4.6, ACE level 36 and alk phos 109. Negative SPEP/UPEP, no elevation of 1,25 vitamin D and a mildly elevated PTHrP 49 pg/mL (14-27). One interesting aspect of PTHrP is that the most common assay measures the carboxy-terminal fragment, which is usually removed by the kidney and might be abnormality elevated in renal insufficiency. On our patient, his hypercalcemia (~11-13) was associated with worsening renal function and creatinine peaked at 4.3 mg/dl. Despite hydration and ibandronate 6mg IV, his hypercalcemia persisted at ~11-12 mg/dL (72 hours afterwards).

For further workup, another assay was performed with the amino-terminal fragment of PTHrP and revealed a low value (0.8). Lastly, there was no evidence of metastasis on bone scans. So what was the cause of the hypercalcemia in our patient and how can we get it under control?

Solid tumor cells are believed to secrete other bone-resorbing factors that mediate hypercalcemia through increased production of prostaglandins E (PGE). PGE is a potent stimulator of bone reabsorption in vitro and there is both animal and human data suggesting that PGE is an important contributor of hypercalcemia in some malignancies.

The most interesting aspect of it is that treatment involves administration of NSAIDS, which can block the production of PGE and resolves hypercalcemia. The original paper dates back to 1975 at the NEJM and there has been not many reports after that. Nonetheless, the team taking care of the patient started him on indomethacin 25mg q8hours as a last attempt to control his calcium before removal of the renal mass was performed. The results were astonishing as you can see in the graph above.

So despite all the negative effects of NSAIDs in the kidney, we have now a legitimate use in certain patients that have hypercalcemia 2/2 malignancy. Few questions still remain: how common is PGE-mediated hypercalcemia? Should we be checking for PGE levels as part of the workup? It seems that in patients that are not being considered for surgical resection and that did not respond to biphosphonates, a trial of NSAIDS could be warranted. Especially since the response is so quick!

Please share your experience as well since this was truly the first time I heard of this correlation. Kudos to the team taking care of this patient (led by Dr Mount) and Omar's grand rounds' presentation.
(Patient details modified to preserve patient identity)

National Course for Renal Fellows: Origins of Renal Physiology September 3-10, 2011

Places are still open for renal fellows to join the Mount Desert Island Biological Laboratories, near Acadia National Park in Maine, for this 1 week course. Taught by nationally prominent renal physiologists (who are also superb teachers), trainees perform classical and cutting edge experiments using mostly marine models, and share their results with each other in joint laboratory meetings. Each trainee participates in three of the seven modules, and hears about all modules at the lab meetings. As a result, trainees develop a thorough understanding of the physiology of the nephron, from the glomerulus through the collecting duct. The course provides researchers with a broad perspective on renal physiology, and, by linking basic physiology to clinical nephrology, helps future educators to become better teachers of clinical nephrology.


The course has run 4 times, and has received extremely favorable reviews from all who have taken it. Nate and Matt both took the course blogged about it here, here and here. For those of you who have not taken the course, you can apply here.

Urine Microscopy and the Camera Phone

I had a breakthrough with my iPhone 3G camera. I've tried unsuccessfully several times in the past to take pictures of urine microscopy fields through the lens of the microscope and had just about given up until I came across this NEJM letter to the editor that claimed it was doable.

The trick is to hold the lens of the camera phone about half a centimeter to a centimeter away from the eye piece. I found I needed to turn the intensity of the microscope light source down quite a bit to avoid whiting out the image. It's a little tricky getting the field into focus but with a little practice is completely doable.

Above is an image I took of a granular cast in a sea of non-dysmorphic rbcs from a patient with ATN and foley trauma. As pointed out by the letter to editor one can take video to scroll around the slide so you can show your attending, housestaff or primary team who weren't there with you what the urine microscopy looked like.

Multiple renal arteries and hypertension?

A woman in her 30's presented with five years of severe hypertension, uncontrolled on trials of four or five agents over the past few years. She had had preeclampsia nine years ago that resolved after delivery, and for the next four years she was reportedly normotensive. Her hypertension had been diagnosed five years ago when she developed disabling headaches. Despite attempts at medical control, she continued to have systolic BPs over 200 mmHg, and diastolic BPs over 100 mmHg. In the past year, she had been hospitalized several times for syncopal episodes. Each time, her BP on arrival in the ED was >200/100. Cardiac and neurologic workups were repeatedly negative. According to the patient, she had had numerous urine and blood tests, which failed to yield an explanation for her hypertension. She did not remember having a renal ultrasound, but said she had had a CT which showed "my kidneys were in the wrong place".


Workup in our clinic included normal renin and aldosterone levels (even on an ACEI, which should have increased plasma renin/aldo), and normal plasma metanephrines, VMA, and cortisol levels. She was not on oral contraceptives. Creatinine was normal, although she had trace urine protein on dipstick. Renal CT angiogram is where things got more interesting-- she had a single pelvic kidney, with duplicated renal arteries and a third, accessory artery coming off the aorta to supply the posterior aspect of the kidney. There was no evidence of arterial stenosis, and no hydronephrosis. Her adrenals appeared normal.


I must admit, I am a little stumped about why this woman has such severe hypertension. However, I came across a possible explanation while doing a literature search, and wanted some feedback from this readership. Could her anomalous renal arterial anatomy have something to do with her high blood pressure?


In the 1950s, several autopsy studies suggested that persons who were hypertensive were much more likely than normotensive persons to have multiple renal arteries (somewhere around 70%). These studies were subsequently contradicted by several series of renal angiograms, which did not show an increased incidence of multiple renal arteries among hypertensive persons. Number of renal arteries and whether both kidneys were involved were not evaluated by most of the studies, nor was arterial length or diameter. It appears as though somewhere between 20 to 30% of the population has at least one additional renal artery, though the jury on whether there is an association with hypertension is still out.


The thinking behind the connection is presumptively that narrower and/or longer accessory renal arteries have decreased blood flow compared to a single renal artery; hence, renin secretion is increased. While this mechanism might result in increased blood flow to a normal kidney in a person who has only one kidney with multiple renal vessels (and may downregulate renin secretion in the normal kidney), I wonder what the effect would be on my patient, with her solitary kidney. The problem with this theory is that her renin and aldo levels were normal. However, I'm low on other ideas.


Please let me know what your thoughts are! I'm curious to know if anyone else has had experience with hypertension in patients with anomalous renal arterial blood supplies.

Creatine vs Creatinine

Creatine monohydrate is a widely available dietary supplement. It frequently pops up during both outpatient and inpatient discussions on the differential for acute kidney injury. However, the literature is scant and appears to be conflicting. So, here are a selection of some of the papers that have been published on this subject.

Firstly, creatine itself is produced naturally in the body, mainly by the liver and kidney, and is transported mainly to muscle. It is involved in a complex interplay with phosphate to form phosphocreatine, facilitating a stable and rapid supply of energy on demand. Creatinine (our common, but imperfect, clinical surrogate of GFR) is a breakdown product of creatine.

One of the early reports of association of exogenous creatine with kidney damage was in 1998 - the case described acute on chronic renal impairment in a 25yo man on cyclosporine for FSGS, which was temporally related to ingestion of supplemental creatine (there was no reported change in proteinuria). Upon cessation of the supplement his serum creatinine returned to baseline. No biopsy was performed.


A second case reported biopsy proven acute interstitial nephritis in a 20yo man, which occurred four days after ingestion of creatine supplements. Again, upon cessation of creatine the renal function returned to baseline.


This review of the existing literature on creatine supplements, highlights the varying reported results of the effects of exogenous creatine on both CPK and serum creatinine levels, with some claiming no change and others claiming slight elevations. An interesting randomized, double-blind, placebo-controlled trial of 18 athletes looked at the effect of creatine ingestion (10 g/day over 3 months vs placebo) on cystatin C levels as an alternative measure of eGFR. The authors claimed that creatine caused no significant alteration in estimated GFR as assessed by cystatin C (in fact the cystatin C levels decreased).

Overall, it would appear that we are still awaiting more detailed information of potential renal risk associated with exogenous creatine use. The trials to date are relatively small and longer term follow up is needed. As ever, a detailed exposure history and close vigilance is required, especially in light of the current popularity of alternative and supplement based pharmacotherapy.

AKF Kids Calendar Art Contest

The American Kidney Fund is running an online contest to choose a winner in its 16th annual ‘Calendar Kids’ art contest for children with kidney disease. The winner’s artwork will grace the cover of AKF’s 2012 wall calendar.


To see the what the kids have done and cast your vote click here.


The child who wins the cover contest will receive an all-expenses-paid trip to Washington, D.C., to be honored at AKF’s annual gala, The Hope Affair, this fall. All 13 children who have been named finalists will have their artwork published in the 2012 calendar and will receive a netbook computer and an education savings bond.


Voting ends on June 15, and calendars will be available for purchase on the American Kidney Fund website in October.

Seldinger Technique

One of the many pleasures of nephrology fellowship is learning how to put in temporary hemodialysis lines safely and efficiently using the Seldinger technique (the Swede is seen to the left). As an intern I constantly said to myself "don't let go of the wire, don't let go of the wire, don't let go of the wire." Having mastered this mantra I've now picked up a few more helpful tricks...

Always use the ultrasound. You just never know what the anatomy is going to look like and real time guidance really increases the number of single pass lines. Every central line I placed in residency used ultrasound localization but then landmarks without realtime guidance for placement. Realtime ultrasound definitely helps.

Lots of saline. It's great stuff. Really helpful if you're having a difficult time getting into the vein. The needle and syringe will sometimes become occluded with clotted blood from prior attempts. Flushing both the needle and syringe until the syringe plunger action is smooth helps avoid getting into the vessel but thinking you haven't because you can't aspirate due to clot. I like to keep the fresh and used saline pools separate so there's always some fresh saline handy.

Making sure the needle is in the venous lumen. Taking the syringe off and confirming the blood is dark and nonpulsatile is key to checking that the stick isn't arterial. If it's venous and your proceeding I've found it helpful to slightly drop the angle of the needle (to avoid going though the opposite wall of the vein "through and through") and advancing it 5mm or so further to get the needle tip fully within the lumen. Sometimes, if just the bevel has gotten in just a slight release of pressure moves it out of the vessel and you can't pass the wire.

Passing the guide wire. Not infrequently you'll be able to pass the guide wire to a point that clearly is beyond the tip of the needle and then encounter resistance (if it doesn't seem to have gotten past the needle tip you may be out of the vessel and need to start over). In the case of having gotten past the needle tip and then encountering resistance, sometimes flipping the circular plastic holder that houses the wire 180 degrees (which rotates the wire 180 degrees) will move the curled tip into a more favorable position and allow you to proceed.

The skin incision. Key to a smooth initial dilator insertion is a large enough skin incision along the trajectory of the wire. I've found that holding the guide wire steady along it's natural exit trajectory and then making the incision along this same angle is very helpful. The cutting edge of the scalpel should be directed away from the artery (cutting edge facing medial for the femoral, lateral for the internal jugular).

Trying not to kink the guide wire. Again, I've found that holding the guide wire firm and steady along it's natural exit trajectory then with the other hand advancing the dilator from as close to the skin as possible reduces the chances of kinking. If the wire does kink and you are unable to advance the dilator further, try pulling the guide wire back a centimeter or so while leaving the dilator in place. This will pull the kink into the dilator and then using the same techniques as above you can often complete the dilation.

Lots of 4x4s. When the dilator comes out, lots of blood. Having a 4x4 ready keeps the field clean and minimizes blood loss.

The catheter is in but now a port won't flush or pull back. Most catheters rotate freely in the wings used to suture them in place. If a port isn't functioning try rotating the catheter 180 degrees by twirling it in the wings, this will often move the distal port off the vessel wall and allow pull back and flush.

IgG-4 associated kidney disease

We heard a very interesting presentation today on autoimmune pancreatitis and concurrent systemic disease. The pathogenesis is felt to be related to IgG-4 producing plasma cells, and has now been linked to numerous systemic disease manifestations. The case in question had possible associated autoimmune hypophysitis, leading to presentation with a central diabetes insipidus picture.

These conditions first came to light following the description of autoimmune pancreatitis and recognition of the association of this disease with various other organ system involvement. The lesions in the affected areas had in common a dense infiltration of IgG-4 plasma cells and T lymphocytes. Involvement has been described in the liver, pancreas, gallbladder, kidneys, retroperitoneum and salivary glands as well as many other tissues.

In terms of renal involvement, the most commonly reported lesion is that of tubulointerstitial nephritis, again with a characteristic infiltration of IgG-4 positive plasma cells. Nodular lesions have also been described, which in many cases can be confusing for primary or secondary malignancies. Of note, sometimes these lesions can be FDG avid, and light up on PET scans, further confusing the picture with malignancy. Membranous nephropathy with IgG-4 positive deposits has also been described. Finally, retroperitoneal fibrosis may also predispose to obstructive nephropathy.

Diagnosis involves biopsy of the affected tissue with demonstration of IgG-4 positive plasma cells. Serum IgG-4 levels should also be requested and, if elevated, have a sensitivity for disease presence of ~70-95%.

Most successful reported treatments have been with corticosteroids, usually starting high and tapering to a lower maintenance dose. There is limited experience in relation to the duration of treatment with steroids or use of steroid-sparing agents in this condition.

Noninvasive Control of Uremic Bleeding

We frequently receive requests to dialyze patients with moderate renal failure who are bleeding due to the concern that uremia may be contributing to failure to control blood loss.

Patients with renal failure do have an increased tendency to bleed, usually manifested by prolonged bleeding time. I was recently reminded by one of my colleagues in conference that while dialysis is an option for treatment of uremic bleeding, it is important to recall (ideally prior to placing the large and inflexible central line) that there are several noninvasive medical therapies for uremic bleeding, some of which work quite well and with minimal side effects.

Uremic bleeding is multifactorial, involving dysfunctional Von Willebrand factor, accumulation of many uremic toxins, particularly L-arginine, increased levels of cyclic AMP and cyclic GMP (cGMP) both of which reduce levels of thromboxane A2 (TxA2) and ADP, anemia, which causes platelets to travel midstream through the blood vessels, farther away from the endothelium. Red blood cells also scavenge nitric oxide and release ADP and TxA2. Lower levels of TxA2 and ADP lead to decreased platelet aggregation. Nitric oxide (NO) also plays a central role. L-arginine induces NO synthesis, which stimulates guanylyl cyclase, increasing cGMP levels, and thus decreasing TxA2 and ADP. TNF-alpha and IL 1beta are also increased in uremia, both of which induce NO synthase.

Treatment options for uremic bleeding include: erythropoetin, cryoprecipitate, desmopressin, conjugated estrogens (premarin, explaining the picture associated with the post), and dialysis. Various doses of erythropoetin have been studied, but the success is dependent not on the dosing regimen but the achievement of a hematocrit of 30%. Cryoprecipitate contains factor VIII, vWF, and fibrinogen, likely increasing the proportion of functional clotting factors in uremic patients' plasma. Desmopressin likely releases factor VIII from storage sites, increasing the concentration of factor VIII and minimizing the effect of dysfunctional vWF. The dose is 0.3 to 0.4mcg/kg IV or subcutaneously. It acts within an hour, but tachyphylaxis develops after one dose, likely due to depleted vWF from endothelial stores.

Estrogens can also safely and effectively improve bleeding time in uremic males and females. The dose needed is 0.6mg/kg IV conjugated estrogens over 30-40 minutes once daily for 5 days. The onset of action is about 6 hours, with maximum effect at 5-7 days and a duration of action of 14-21 days. The mechanism is thought to be reduction of L-arginine, which is a precursor to NO. This results in less guanylyl cyclase stimulation and less production of cGMP, leading to increased TxA2 and ADP and improved platelet aggregation. This theory is supported in rat studies. 17beta estradiol given to rats made uremic by reduction of renal mass significantly reduced bleeding time within 24 hours and normalizes plasma concentration of NO metabolites, nitrites and nitrates, and of NO synthase catalytic activity. Endothelial NOS and inducible NOS immunoperoxidase staining in the endothelium of uremic aortas of untreated rats was significantly more intense than in control rats. Uremic rats receiving 17beta estradiol had NOS staining comparable to controls. Estrogens have been used for patients with uremic GI bleeding, with some controversy and a negative RCT in angiodysplasia. Nate Hellman also talked about estrogens in GI bleeding here.

Nature Clinical Practice published a nice review on treatment recommendations for uremic bleeding, with a summary of recommendations and the strength of the evidence behind each recommendation, along with an algorithm for treatment of bleeding patients. Special thanks to Nirupama Ramkumar for finding and summarizing this article in clinical case conference.

Getting to the heart of the matter: Anti-PLA2R and MN

A 53-year-old Caucasian male presented with pulmonary embolism, and was found to have nephrotic syndrome. A kidney biopsy showed membranous nephropathy (MN). The disease progressed despite treatment and six years later, the patient underwent a pre-emptive living unrelated renal transplant with basiliximab induction and triple maintenance(prednisone, MMF and tacrolimus). Urine protein/creatinine ratio (U Pr/Cr) was about 1 g/g at the time of discharge. His serum creatinine (SCr) nadir at around 2 mg/dl, so a kidney biopsy was done at 1 month post-tx, showing no rejection and negative deposits on EM.

After 2 years of stable renal function and no significant proteinuria, he developed a rise in both SCr up to 3 mg/dl and U Pr/Cr up to 7 g/g. A biopsy showed recurrent membranous GN, with IF positive for granular staining with IgG1 and IgG4, and EM showing subepithelial deposits.

The two main differential diagnoses for new-onset proteinuria and renal allograft dysfunction are recurrent primary glomerulonephritis and transplant glomerulopathy (a form of chronic allograft injury which is generally believed to be immune-mediated). Idiopathic MN recurs in 30-40% of patients, usually between the 2nd and 3rd year. The outcome, as in the native kidney, can be variable, although spontaneous remission appears less common. It is tempting to speculate that transplantation selects a subtype of patients with severe disease (those who progressed to ESRD) and, therefore, patients with recurrent MN are more likely to progress than not. A study of protocol biopsies from the Mayo clinic suggested that histologic lesions of post-transplant MN persist and progress, and usually (in 86% or 12 of 14 patients) lead to clinical manifestations. The impact of recurrent MN on long-term graft survival remains unclear, and most data suggest no adverse effect, although a graft loss of 10% at ~4 years was reported in one study.

One of the exciting developments in our understanding of MN has been the identification of the antibody to M-type phospholipase A2 receptor (PLA2R), a podocyte antigen, in ~70% of patients with idiopathic MN. As has been noted previously in this blog, there is evidence suggesting that levels of the anti-PLA2R may correlate with both disease activity and the likelihood of clinical response to treatment with rituximab, a monocolonal Ab to CD20 that targets B cells. Treatment with rituximab has been shown to reduce foot process effacement and lead to regression of immune deposits in those who respond.

Stahl, et al reported a case of early recurrent MN in which anti-PLA2R Ab was detected pre-transplant and at the time of recurrence. Levels of the Ab fell rapidly (within 2 weeks) after treatment with rituximab, although proteinuria appeared to increase transiently (at 2 weeks), and then remit (at 2 months). It has been demonstrated in several reports that proteinuria is reduced gradually and may take several months to reach its nadir. Similarly, in our patient, we found (thanks to Dr. Becker's lab) that anti-PLA2R, as detected by Western blot, was present in sera pre-transplant as well as time of recurrence, and disappeared completely after treatment with 2 doses of rituximab (1 g each). Both SCr (2 mg/dl) and U Pr/Cr (1 g/g) had improved by 3 months (figure above).

Some interesting questions remain unknown: 1) Are patients with MN who have detectable antibody (at the time of transplantation or later) more likely to recur? 2) How long does the response to rituximab last? (Up to 2-year data have been reported by the Mayo group) 3) Would pre-emptive treatment with rituximab of patients who have detectable antibody (at the time of transplant or later) prevent clinical recurrence, and is it worth the risk? Sindhu Chandran, MD

Lactate gap in ethylene glycol toxicity

From Brindley P.G et al., CMAJ 4-10-07, 176(8) pg1097-1099

When making a decision about urgent dialysis it is important to have an much information as quickly as possible. In suspected ethylene glycol toxicity time is of the essence. Waiting 3-4 hours or more for the ethylene glycol level to come back can be deleterious to the patient. Often times we are left to make the decision to begin dialysis or therapy based upon a high degree of suspicion from the available laboratory data and patient circumstances. During conference recently I heard of another pearl that could help in determining if ethylene glycol was ingested.

This is termed the lactate gap. Essentially this is the difference in values obtained from 2 different analyzer methods. As seen in the graph, taken from this paper, the commonly used Radiometer method can result in a falsely elevated lactate level when compared to other assays (iSTAT, Bayer, Vtros and Beckman).

Why is this the case?

This likely occurs because metabolites of ethylene glycol cross react with L-lactate oxidase. The Radiometer assay uses the enzyme L-lactate oxidase to accelerate the reaction between L-lactate and oxygen, the products of the reaction being hydrogen peroxide and pyruvate (click here for discussion of this). The L-lactate concentration is then computed from the measured hydrogen peroxide concentration. It is thought that glycolate (a metabolite of ethylene glycol) is able to interact with L-lactate oxidase and produces a significant amount of hydrogen peroxide and thus the test reports as a high lactate level.

The enzymatic L-lactate assay are also subject to interference from certain drugs at toxic levels such as; Isoniazid, Acetaminophen and Thiocyanate.

The radiometer method of detecting lactate is commonly used in point-of-care testing such as those reported by ABG's. It is important to know what your lab is using when interpreting lactate values. Serum lactate levels are typically computed using a non-radiometry method.

Obtaining simultaneous radiometer lactate and another method of lactate measurement and computing the lactate gap (the difference between the two values) can help in distinguishing true lactic acidosis from ethylene glycol toxicity.

Hepatorenal Disease - Beyond the syndrome

In general, when we are asked to evaluate a patient with liver disease for the development of acute renal failure, the three top differentials are usually: true hepatorenal syndrome, a prerenal picture (often 2/2 overdiuresis) and ATN. Cholemic nephrosis can also be considered but it usually requires very high bilirubin levels. These causes were previously discussed on prior blogs. However, I wanted to focus on some more atypical etiologies that we should keep in our list in case things don’t look as straight forward.

The first key point is to always carefully look at the urine on microscopy and quantify the proteinuria. The latter is important since some conditions that have proteinuria do not show on dipstick (not related to albuminuria), like AL amyloidosis, which can also be a cause of liver disease.

The presence of active urine sediment opens a whole new list of differentials, which can be narrowed down by using the primary cause of liver disease as a starting point:

1) Alcoholic cirrhosis: Mesangial IgA deposition associated with chronic liver disease, is the most common form of secondary IgA nephropathy. An imparied removal IgA-containing complexes by the Kupffer cells in the liver is thought to predispose to IgA deposition in the kidney. Despite the frequency of glomerular IgA deposits in advanced liver disease, most adults have no clinical signs of glomerular disease. It is unclear why some patients are predisposed to renal manifestations while others are not.

2) Viral hepatitis (HBV or HCV): might lead to variable glomerular lesions. It is important to add complements and cryo to your workup.

• MPGN: (low C3 and C4) Renal manifestations range from hematuria to nephrotic syndrome. In some cases, its associated with mixed cryoglobulenemia (positive Cryo and low C4). Cryos picture tends to be associated with purpura, arthralgia and lymphadenopathy.

• Membranous nephropathy (normal complements): thought to be related to HBeAg and anti-HBe deposition on subepithelial space.

• Secondary polyarteritis nodosa (vasculitis): typically occurs within 4 months after the onset of HBV infection (also cases with HCV) and has similar clinical features as the idiopathic form - systemic symptoms (fever, weight loss, fatigue) + Skin signs (purpura/livedo reticularis) + neuropathy + GI symptoms (pain/bleeding) + HTN.

Don’t forget about potential drugs used for treatment of hepatitis that can be nephrotoxic to the tubules (e.g. adefovir)

3) If an auto-immune disease is the cause of liver failure, like primary sclerosing cholangitis (PSC), you have to think about a possible concomitant auto-antibody process. Interestingly, more than 75% of patients with PSC have either ANA or pANCA. A small proportion also have either anti-GBM or anticardiopilin antibody (antiphospholipid syndrome). Finally, more than 90% of patients with PSC also have ulcerative colitis. The latter may predispose to secondary amyloidosis (amyloid A deposition 2/2 chronic inflammation) or its treatment with sulfazalazine (type of NSAID) might lead to AIN or nephrotic syndrome.

Overall, just be thorough in your evaluations and don’t let the routine of patient care limit your differentials.

Picture: Chihuly amazing work on glass that is being exposed in Boston now! Truly outside the box.