Saturday, October 8, 2016

2 Free Kidney iBooks Available (yes FREE)

Paul G. Schmitz (Saint Louis University TPD) recently published 2 new textbooks useful for students, residents, and fellows interested in kidney disorders. These are both FREE downloads from the iBooks store. These are both self-published and interactive (Macs, iPhones, or iPads for now). Content updates will also be free and will be performed by student, resident, and fellows.

Check them both out and provide Dr. Schmitz some feedback. They look fantastic.

Wednesday, October 5, 2016

Young adults and kidney donation - To do or not do.

A short article was recently written on Washington Post by a medical student who donated a kidney at age 18 to his brother's stepfather and now regrets it. Worth a reading (link here).

 He questioned the informed consent and the poor quality data we have for long-term outcomes after donation, including the fact that we don't have a donor registry that captures all donors in the USA.

 Age of donation is an important factor to consider when assessing the potential long-term risk of kidney donation. Younger kidney donors have a greater chance of suffering a second-hit leading to kidney injury through their lifespan, in particular with life expectancies surpassing 80 years in many countries. Therefore, it is generally recommended to be more stringent in the selection of younger donors. But how should we as a Society respond to this? How individual centers approach younger donors below 30yo? Would love to hear our community thoughts on this.

 Figure from Kidney Transplant iBook (adapted from Mjoen et al. Kidney Int 2014)

Monday, October 3, 2016

Video CPC - Renal Pathology Episode #011

Try your diagnostic and biopsy reading skills as we work through an unknown case that demonstrates some very interesting renal pathology. Dr. Gaut, section head of nephropathology at Washington University in St. Louis and Dr. Younus, a 2nd year renal fellow, will read a complicated biopsy together. The diagnosis is purposefully not revealed here because the case is a real zebra!  Check out the video below.

Monday, September 5, 2016

Video Introduction to Understanding Lupus Nephritis Classification - Wash U Episode # 010

The 10th episode of the Washington University Nephrology Web Episodes delves into lupus nephritis.  This video discusses the evolution of classifications over the years from the early WHO to the most recent ISN/RPS classifications, in addition to demonstrating active and chronic lesions.  You can view the homepage here, and a link to the most recent video below.

Thursday, September 1, 2016

Clinical Scientist in Nephrology Program

The American Kidney Fund Clinical Scientist in Nephrology (CSN) fellowship program application is open for next year's cycle. It provides $80,000 per year for clinical research. Many distinguished nephrologists are prior recipients of this award including
Gary Curhan, Ravi Thadani and Glenn Chertow. Funding is provided for two years and the closing date for applications is December 1st 2016.

More details can be found here.

Tuesday, August 16, 2016

Epstein Barr Virus & Acute Interstitial Nephritis

Acute interstitial nephritis (AIN) has resurfaced as an important cause of kidney injury in the hospitalized patient, particularly because of recent evidence implicating such common medications as proton pump inhibitors. Though most current cases of AIN have been attributed to medications and autoimmune disorders, a patient I recently encountered on the consult service reminded me of an additional cause.

The patient in question was a woman with rapidly-progressive, oliguric, acute renal failure. She had just been hospitalized with infectious mononucleosis and her Epstein Barr Virus (EBV) DNA viral load was >11,000 copies/mL. Her symptoms resolved with intravenous hydration, and she was discharged in two days. Unfortunately, the patient returned two weeks later with fevers, flank pain, and anorexia. Her exam was normal apart from mild edema. Urinalysis revealed 100 mg protein, trace ketones, 21 white blood cells, and three red blood cells. A urine protein/creatinine ratio was 0.62. Serum creatinine was 2.58 mg/dL, total CO2 was 14 mmol/L, and she had no peripheral eosinophilia. The patient was initially treated with hydration and antibiotics for presumed pyelonephritis. When a urine culture revealed no organisms and her renal function continued to deteriorate, Nephrology was consulted.

Our differential diagnoses included pre-renal azotemia, acute tubular necrosis from sepsis or hypoperfusion, post-infectious glomerulonephritis, and AIN. My sediment analysis only revealed a few granular casts. Given the patient’s normal renal function at baseline, absence of diuretic use, and oliguria, we interpreted her fractional excretion of 1.1% to indicate intrinsic renal pathology. A renal ultrasound revealed mildly enlarged kidneys with increased echogenicity. Serum complements as well as anti-nuclear and anti-neutrophil cytoplasmic antibody levels were all normal. Her EBV DNA viral load was now 220 copies/mL. The patient’s creatinine continued to rise in spite of adequate hydration and discontinuation of nephrotoxic agents, peaking at 4.04 mg/dL. By this time, she was found to have an elevated urinary eosinophil count. Despite having a positive predictive value for AIN of only 30%, the patient’s urinary eosinophils increased our post-test probability for AIN in this clinical situation. As she had no comorbidities, took no home medications, and had only received antibiotics for a few days, Epstein-Barr Virus (EBV) was presumed to be the cause.

Our patient was hesitant to undergo a renal biopsy, and as the potential benefit of corticosteroids outweighed any risks, she was empirically started on 1 mg/kg po prednisone daily. Her renal function began to improve the following day and was ultimately restored to premorbid levels at her two-week follow-up visit.

Though viral infections have long been described in textbooks as known causes of AIN, few case reports of it exist in the current literature. EBV-associated AIN was first reported in 2000 when a 17-year old patient presented with jaundice, hemolytic anemia, and acute renal failure. Serology revealed elevated EBV IgM and IgG viral capsid antibody titers, elevated IgG early antigen titers, and negative IgG nuclear antigen titers. Renal biopsy and subsequent light microscopy revealed a patchy, interstitial infiltrate comprised of lymphocytes, plasma cells, eosinophils, and neutrophils. In-situ hybridization for EBV mRNA was positive. Serum creatinine returned to normal one month after treatment with prednisone. Other cases were published with similar presentations and outcomes, but reports of EBV-associated AIN continue to be scarce.

Two competing theories exist which seek to explain the pathogenesis of EBV-associated interstitial nephritis. One suggests that kidney injury is simply collateral damage from activated T lymphocytes responding to the infection. Another theory indicates that direct toxicity from the virus itself plays a role. Is EBV-associated AIN then, a result of direct viral infection or is it a consequence of an immunologic response? The literature is conflicting. Biopsied cases of EBV-associated interstitial nephritis do reveal a predominance of cytotoxic T cells. However, Mayer et al failed to identify EBV RNA in renal biopsy tissue and instead suggested that the EBV antigens in infiltrating lymphocytes activated a massive T-cell mediated immune response. This was demonstrated once more in a 2011 study that detected no EBV DNA in renal biopsy specimens of patients with suspected AIN.

In contrast, both Bao’s and Cataudella’s analyses reported the detection of the EBV genome using polymerase chain reaction (PCR) techniques in renal biopsy samples. However, EBV DNA has since been inconsistently found in other renal biopsy specimens, and EBV DNA has been found in biopsies of patients with IgA Nephropathy and Membranous Nephropathy as well.

EBV’s direct role in infection is less debated in patients with chronic interstitial nephritis. Becker et al used in-situ hybridization and PCR techniques to show that renal biopsies of patients with “idiopathic” chronic interstitial nephritis actually had EBV genomes expressed in their proximal tubule epithelia. It is now known that asymptomatic EBV can persist within B lymphocytes and that reactivation can result in a robust, pro-inflammatory cytokine cascade.

Without more invasive testing, it is impossible to determine whether our patient’s acute renal failure was a result of the virus’s direct nephrotoxicity as opposed to a consequence of cytokine-mediated inflammation. Though she was not prescribed any antiviral agents, these are not routinely recommended in immunocompetent persons infected with EBV. In the same vein, we cannot assume her rapid improvement with corticosteroids supports the pro-inflammatory hypothesis of EBV-associated AIN.

Further studies analyzing the presence or absence of EBV DNA in patients with both AIN and chronic interstitial nephritis are needed. Such studies may provide basis for the use of corticosteroids, determine baseline characteristics of latent EBV, and help to develop our understanding of the pathogenesis of AIN in general. Cases like that of our patient’s also serve to remind us of less common causes of AIN to bear in mind when in clinic or on the wards.

 Posted by Devika Nair, Vanderbilt Nephrology Fellow

Friday, August 5, 2016

A Great Primer to Review Kidney Transplant Histology - Wash U Web Episode #009

The next episode of the Wash U Nephrology Web Series was published this morning and is back to the basics with a great renal pathology teaching session with our nephropathologist.  This episode dives into the complicated world of interpreting transplant histology and is a great episode for anyone looking to brush up their skills when dealing with these complicated cases.  You can view our homepage here or check out the most recent video below.

Thursday, August 4, 2016

Hemodialysis University

The International Society for Hemodialysis' Hemodialysis University is a two-day course that will be taking place in Chicago Sept 9-10th this year. The course covers many issues current in dialysis and of particular interest are talks on HIF stabilizers for anemia and starting home HD programs.

The course offers up to 14 hours of CME credit and has special rates for fellows and NPs.

More details are available here.

Wednesday, June 29, 2016

2nd Midwest Transplant Symposium

Free accommodation is available for nephrology fellows and residents (IM or Surgery) for Friday night (October 14) at Home 2 Suites (rooms are limited). To apply for free accommodation, please email Laura Kipper 
Go here for registration and more information

Friday, June 24, 2016

How would you improve dialysis care if you had unlimited resources?

What if we could do more frequent dialysis? Would this improve QOL as potentially seen in the original FHN trial or even improve survival as seen in recent longer-term FHN follow-up?

What if we had more resources to support home dialysis? Would increasing nursing and other provider home visits and patient support make the promise of home therapy a reality for more patients?

What if we had more nurses, technicians, dieticians, or social workers in-center? Would you train them to lead intra-dialytic exercises? Give them skills in cognitive behavioral therapy? Teach patients how to eat better or how to cook? What about iPADs with educational or other productive resources for patients sitting idle in their chairs.

CJASN published an article this month calling for studies focusing on how to improve quality of life for our patients rather than debating which dialysis modality might extend life a few months/years longer. They reference an interesting qualitative study of interviews with over 30 Canadian patients, caregivers, and providers investigating potential research areas. The “top 10 research uncertainties” included items such as: enhancing communication between providers and patients; comparing dialysis modalities’ effects of QOL and mortality; addressing symptom (such as itching or fatigue) control and the psychosocial impact of ESRD; and addressing vascular access concerns. The focus on QOL by patients and their caregivers is notable and something that we should embrace.

Dialysis services in the US have an interesting, and it seems rare, quirk. 90% of patients are prescribed a therapy (in-center hemodialysis) that the vast majority of their doctors would not want for themselves. If you haven’t polled your colleagues yet you’ll likely discover they would favor PD or home hemo should they need dialysis themselves. This is a significant gap compared to our current reality.

So what would you do? 

Robert Rope, Nephrology Fellow, Stanford

Tuesday, June 14, 2016

Potassium Board Review - New Wash U Nephrology Web Episode

Hypokalemia, hypertension, and metabolic alkalosis - this clinical triad can be seen in a variety of interesting disorders that unfortunately are much more common during in-training or board certification exams than in clinical practice.  That doesn't mean you should cram for them the night before the exam!  Understanding the way these diseases affect potassium handling in the kidney can help learners of all levels acquire a better understanding of normal renal physiology.

This month's nephrology web episode from Washington University in St. Louis focuses on 4 board-style questions related to potassium disorders, and we hope you find it helpful.  The full episode can be viewed below:

Friday, June 3, 2016

Secondary Adrenal Insufficiency: An often overlooked cause of hyponatremia

As I prepare for my nephrology fellowship, I find that in preparing my didactics as a chief resident, I selfishly (and perhaps subconsciously) include kidney-related teaching wherever I can. During one such moment, I came across a something I feel is worth reviewing for early learners: the many causes of hypotonic euvolemic hyponatremia.
We have all been taught that hyponatremia is almost always the result of excess ADH.  It is then up to us to determine whether this excess hormone production is part of the body’s appropriate physiologic response to volume depletion and hyperosmolarity.  In SIADH, urinary dilution is impaired despite the absence of hypovolemia. Rather than volume depletion, the stimuli for ADH range anywhere from malignancy-related ectopic hormone production, to CNS injury, to chronic hypoxia. The resulting expansion of extracellular volume decreases aldosterone and renin activity and increases urinary sodium excretion.  This excess fluid retention in the setting of sodium loss results in a euvolemic, rather than hypervolemic hyponatremia.
Similarly, hyponatremia due to hypothyroidism is thought to be a consequence of the kidney’s inability to excrete a free water load due to an increased secretion of ADH and decreased water delivery to the distal nephron. Others implicate the depressed cardiac output and reduction in renal perfusion seen in patients with thyroid hormone deficiency, though this effect has mainly been demonstrated in myxedema coma. Because sodium excretion is intact despite excess fluid retention, these patients will also be clinically euvolemic.
Because of the negative feedback that glucocorticoids exert on ADH, secondary adrenal insufficiency also results in an ADH-related hyponatremia.  Unlike those with primary adrenal insufficiency, patients with secondary adrenal insufficiency are less at risk for stress-induced adrenal shock. This is because mineralocorticoid secretion from RAAS activation is still intact. In fact, patients with secondary adrenal insufficiency may only present with vaguesymptoms such as malaise and depression.
As a result of the subtle ways that these patients present, secondary adrenal insufficiency is an often-overlooked cause of euvolemic hyponatremia. One study revealed that hyponatremic patients with adrenal insufficiency due to hypopituitarism were admitted to hospitals up to fourtimes before their true diagnoses were discovered. Due to many of these patients presenting with symptoms of a “failure to thrive,” they inappropriately receive hydration.  This has important clinical implications, as normal saline can paradoxically worsen the hyponatremia seen in SIADH, hypothyroidism, and secondary adrenal insufficiency.
To understand why this occurs, remember that sodium and water regulation are handled independently by the kidney.  In any clinical scenario of inappropriately-elevated ADH, the mechanism for sodium excretion is intact.  This means that the kidneys will excrete whatever salt load is given to them and inappropriately retain water.  When administering normal saline to a euvolemic patient with hyponatremia and a very high urine osmolality, all of the sodium will be excreted, but a portion of the water will be retained. This can worsen a patient’s hyponatremia.
This concept is better illustrated in the below example:
Suppose our patient has a hypotonic, euvolemic hyponatremia with an inappropriately-elevated urine osmolality of 600 mosms/kg.  Remember that 1 liter of normal saline contains 154 mosms of Na and 154 mosms of Cl.  If the patient is given 1 liter of normal saline, he is receiving 308 mosms of solute in total.   Because the sodium regulation of his kidneys is intact, all 308 mosms of solute will be excreted in a small portion of free water.  The remaining free water will be retained, thus exacerbating his hyponatremia.  It should be noted that this effect is seen as long as the patient’s urine osmolality (a surrogate for his degree of ADH elevation) is greater than the osmolality of the administered fluid; that is to say, as long as the concentration of sodium in his urine is greater than the concentration of sodium in normal saline.
How then, can we distinguish “inappropriate ADH” due to medications and malignancy from “inappropriate ADH” due to secondary adrenal insufficiency?  Unfortunately, lab tests appear to be of limited value. In addition to an elevated urine osmolality and urine sodium, both sets of patients often have low uric acid levels, thought to be due to decreased tubular uric acid resorption and increased clearance. Some point out the elevated ACTH and propiomelanocortin (POMC)-derived peptide levels seen in primary adrenal insufficiency as possible distinguishing factors, but these test results often fluctuate are not used frequently in clinical practice.
The need to be meticulous in evaluating euvolemic hyponatremia was once again illustrated during a fluid and electrolyte workshop I attended at the National Kidney Foundation’s Spring Clinical Meeting this year.  The patient being discussed presented with a hypotonic euvolemic hyponatremia that many assumed to be due to SIADH, though he had no risk factors for it.  Ultimately, he was found to have secondary adrenal insufficiency from a growing pituitary tumor.
As a medical student and early resident, I always felt that SIADH was a label given to hyponatremic patients with an otherwise unrevealing work-up, aka “hyponatremia NOS.” However, budding nephrologists such as myself must remember one of the original diagnostic criteria of SIADH as first described by Schwartz and colleagues in 1957: in the evaluation of euvolemic hyponatremia, SIADH is a diagnosis of exclusion. While most of us know to rule out hypothyroidism, the subtle signs and symptoms of secondary adrenal insufficiency often make it easy to overlook.  Clinical situations such as these remind us of the importance of being systematic in our approaches to chief complaints and laboratory abnormalities regardless of our level of training.
Devika Nair, Nephrology Fellow, Vanderbilt

Wednesday, May 18, 2016

Recurrent kidney stones: causes and management

Patient is a 37-year-old female with cystic fibrosis, recurrent nephrolithiasis who presents to clinic with asymptomatic bilateral kidney stones (8mm on right; 2mm on left) on imaging.

 What type of stone and why cystic fibrosis (CF) is associated with kidney stones?
 Patients with CF are at increased risk of calcium oxalate stones. This is thought to be primarily due to enteric hyperoxaluria and hypocitraturia.
 Gut malabsorption can lead to hyperoxaluria. In malabsorption, there is an increase in free fatty acids (FFA), which bind to calcium and decrease the amount of calcium in the gut available to bind to oxalate. This leads to an increase in soluble oxalate which is absorbed in the gut (See Nezzal et al. NDT 2016 for an excellent discussion of enteric hyperoxaluria). Furthermore, chronic diarrhea from malabsorption leads to a chronic metabolic acidosis and hypocitraturia. In the urine, citrate is an inhibitor of the calcium oxalate complex. Higher urinary oxalate and less urinary citrate are associated with higher risk of stone formation.

 What is the diagnostic work-up recommended in the above patient? 
Initial evaluation of all patients with kidney stones, should include two 24-hour urine collections. Evaluating the urine composition provides crucial data for characterizing the patient’s risk of kidney stone formation (both formation of new stones and growth of existing stones). For this patient, she also had a noncontrast CT that again demonstrated a 8mm stone in the lower pole of the right kidney. She also had 2 small (2-3mm) stones on the left (See Curhan, et al. “Diagnosis and acute management of suspected nephrolithiasis in adults” Up to Date, for more in depth discussion).

 How to best manage this patient’s stones?
 For her existing calcium oxalate stones we need the help of our urology colleagues. Kidney stones less then 5mm are likely to pass on their own, without procedural intervention. For larger stones, discussion with the patient and urology is important. Options include medical expulsion therapy (MET), extracorporeal shock-wave lithotripsy (ESWL), ureteroscopy (URS), and percutaneous nephrolithotomy (PNL) (See also: AUA/EAU J Urol Vol 178, 2418-2434 2007 and prior blog). Our patient underwent urological evaluation and ureteroscopy to remove her 8mm stone.

 How can we prevent further stones formation? 
Our patient’s 24-hour urine revealed total volume of below 2 Liters, oxalate 44, and citrate 87. For her, we discussed increasing fluid intake to reach a goal of at least 2 L/day.  To lower her urinary oxalate we discussed multiple strategies, including reduction of dietary oxalate intake, increasing dietary calcium intake to the recommended daily allowance, and starting calcium supplementation with meals (to bind to oxalate in the gut and reduce oxalate absorption) [see also

We also started potassium citrate to increase urinary citrate (check this article for the updated AUA guidelines for the medical management of kidney stones). 

Megan Prochaska MD
Second year fellow BWH

Image from oxalate stone (

Tuesday, May 10, 2016

Renal Functional Reserve: Time for a Kidney stress test in clinical practice?

GFR varies under normal physiological conditions and during illnesses. A popular example is a low GFR in vegetarians and a higher GFR in consumers of large quantities of animal protein, even when they have a similar normal renal mass. It is not clear what the maximum GFR can be, but it can be approached with an acute animal protein load. One to two hours after an animal protein load, individuals with healthy kidneys will show a significant rise in their GFR independent of their baseline GFR. The difference between baseline and maximal (i.e. stress or peak) GFR is called the Renal Functional Reserve (RFR).

The maximum capacity of a functioning renal mass is not reflected by the baseline GFR of a given individual. Bellomo et al used an example of 4 different patients to explain this concept. Patients A (animal protein consumer) and B (vegetarian) have the same renal mass but different baseline GFRs owing to different basal protein in-takes levels. Patient A has a GFR of 120 ml/min that can be stimulated to 170 ml/min. Patient B has a baseline GFR of 65 ml/min that also can be stimulated to 170 ml/min. Therefore, the RFR in these two patients is different because they are using their GFR capacity at a different level. Patient C had a unilateral nephrectomy. His baseline GFR corresponds to his maximal GFR under unrestricted dietary conditions. If a moderate protein restriction is applied to his diet, his baseline GFR may decrease and some degree of RFR become evident. Patient D, who is a vegetarian who underwent unilateral nephrectomy, will have a lower baseline compared to patient C but a higher RFR. Therefore, in general, restoring some RFR requires a severe protein restriction, and hence baseline GFR does not always correspond to the extent of functioning renal mass unless we place it in the context of maximal capacity. Bellomo et al concluded the section about GFR by using a very interesting, possibly true, statement:

“In this regard GFR is not unlike a resting ECG for the kidney. When it is grossly abnormal, renal function is impaired, but when it is normal, a stress test is required.”

The GFR rises considerably during pregnancy. This physiological rise is multifactorial and is mainly attributed to increase in cardiac output and renal blood flow. It becomes apparent from the 1st month and peaks at 40% – 50% above baseline levels by the 4th or 5th month of pregnancy. This increase in GFR is referred to as renal hyperfiltration. The RFR is consumed as a part of adaptation to this physiological demand that occur during pregnancy. This was demonstrated by Ronco et al. They assessed GFR changes in pregnant women, with normal kidneys, before and after protein load. After acute protein load, all women had a significant increase in GFR. This rise was more in the first than in the last trimester. This finding explains, at least partially, renal hyperfiltration in pregnancy.

RFR allow for an increase in GFR during stressful conditions to ensure maintenance of adequate kidney function. When RFR is lost or fully utilized and the kidney insult continues, changes in baseline GFR and serum creatinine occur. After an AKI episode, creatinine and GFR may return to normal, displaying an apparent complete recovery of the kidney. Unfortunately, this recovery might be at the expense of reduction or loss of the RFR. In my opinion, without performing a kidney stress test to assess the RFR post-AKI, it will remain unclear whether the recovery from AKI was complete or was it just a biochemical recovery (reflected by creatinine level) at the expense of RFR utilization. Conceptually, recovering baseline GFR and creatinine level post-AKI without recovering the RFR should be labelled as new-onset CKD because it actually reflects an irreversible loss of nephrons/RFR. I have no evidence to support this, but I would hypothesize that these patients who lose their RFR post-AKI are the ones who were shown to progress to CKD in previous studies.

I think the following are potential benefits for using a kidney stress test/ checking RFR:
  1. Assessment of recovery post-AKI: It will help to detect patients who are likely to progress to CKD.
  2. Assessment of living kidney donors prior to donation: It is likely that a low RFR might increase the long-term risk of CKD during the post-donation period.
  3. To assess the risk of AKI in patients undergoing contrast studies and high-risk surgeries.
Of course robust studies are needed to assess the diagnostic and the prognostic utility of RFR and kidney stress test in the clinical setting.

Post by Mohammed Kaballo

Thursday, May 5, 2016

Obesity and CKD: How big is this?

How important is obesity to the field of nephrology? Perhaps obesity is the single strongest risk factor for CKD in the US and most of the developed world. While genetics are certainly important, obesity drives the diabetes epidemic and contributes significantly to the hypertensive burden in our population. But if obesity is this important, how can we best help our patients? Should nephrologists emphasize obesity along with our traditional targets (e.g. HbA1c < 7%, SBP < 130 or 140 mmHg, statin use, etc.)? Unfortunately, there is not a lot of data to guide us.

Attempting to look at obesity as a risk factor for CKD independent of diabetes or hypertension is challenging. However, there are a few studies that suggest an independent effect on CKD and its progression (Hsu, Cao). Whether or not “metabolically healthy” obese patients are at higher risk of CKD remains unclear (Hashimoto).

There are likely other mechanisms in obesity beyond diabetes and hypertension that are injurious to our beans (Rao). For example – increased abdominal pressure can activate RAAS and visceral fat itself can generate not just angiotensinogen but also inflammatory cytokines (such as leptin) which may stimulate renal fibrosis. Physiologic changes in obesity create glomerular hypertension, hyperfiltration, and glomerulomegaly. In a subset of these patients, for unclear reasons, overt glomerulosclerosis develops.

The effect of obesity on renal function was clearly reported in 1974 in four non-diabetic patients with severe obesity and nephrosis (Weisinger). The nephrosis and proteinuria resolved with significant weight loss during prolonged hospitalizations. Subsequent studies have also shown the resolution of glomerular hyperfiltration with weight loss.

The clinical and pathologic characteristics of obesity related glomerular damage have been described (Kambham). Notably, when compared to patients with idiopathic FSGS, obesity-related glomerulopathy demonstrates lower rates of true nephrotic syndrome as well as less, but certainly not insignificant, progression to ESRD. Importantly, clinical characteristics do not seem to differentiate between obesity-related glomerulomegaly with hyperfiltration and the development of obesity-related FSGS.

If obesity worsens renal function then how should we combat it? Data focusing on individual patient treatments in CKD is limited, with the majority of studies being small with short term follow-up. Weight loss is associated with a reduction in proteinuria but no clear change in GFR (Naveneethan). Bariatric surgery offers a therapy that can reliably produce significant weight loss, reduce or eliminate proteinuria, and improve diabetic and hypertensive control. Its effects on GFR however are hard to predict, especially given that creatinine often decreases post-surgery given the loss of lean body mass that parallels declines in adiposity. Likewise, the true risk of hyperoxaluria and worsened renal function in modern malabsorptive procedures is not well understood. The literature on bariatric surgery and diabetic nephropathy was recently reviewed here (Friedman).

Questions still remain.
  • How aggressive should we be regarding weight loss in our patients? 
  • Is it enough to recommend diet and exercise or should we advocate for weight loss programs? 
  • Should we prescribe medications such as orlistat or phentermine/topiramate? 
  • Should we refer patients for consideration of bariatric surgery? 
 Hopefully the coming decades will clarify these questions.

Robert Rope, Nephrology Fellow, Stanford

Wednesday, May 4, 2016

Emphysematous Pyelonephritis was asked to see 74 year old man with an acute on chronic kidney injury.  He had 2 days of generalised lower abdominal pain and vomiting but no urinary symptoms or fever.  His past history included advanced CKD, benign prostatic hypertrophy and a slow growing renal cell tumour under radiological surveillance.  His vital signs were normal and he had mildly raised inflammatory markers.  I ordered a CT KUB to exclude obstruction (it was a weekend and was no ultrasound service in the hospital).  To my surprise this came back as showing emphysematous pyelitis.  Interestingly there had been a hiss of air as he was catheterised for fluid balance monitoring – a fact I had dismissed at the time!

Emphysematous UTIs are gas forming infections of the urinary tract and can manifest as cystitis (gas within the bladder wall), pyelitis (gas within the collecting system) or pyelonephritis (gas within renal parenchyma or perinephric tissues).  It is a relatively rare condition and there is a dearth of literature describing incidence.  Diabetes and urinary tract obstruction are major risk factors, present in around 80% and 20% of patients respectively. Causative organisms are most commonly E. Coli and Klebsiella pneumoniae, with Candida being involved less frequently. Presentation is usually similar to acute severe pyelonephritis with fever, flank pain and vomiting. 50% of patients have an associated bacteraemia. Diagnosis is usually made by CT which shows the extent of gas within the urinary tract and any obstruction.
Treatment depends on the extent of infection.  It ranges from parenteral antibiotics alone for patients where gas is limited to the collecting system with no obstruction, to percutaneous drainage of purulent material and antibiotics if there is abscess formation or extension of gas into the perinephric space, to nephrectomy in patients with diffuse gas and extensive renal destruction.

In the above case, the urine sample was initially reported as ‘no significant bacteriuria’ but subsequently grew a resistant E. Coli >1,000 - <10,000 cfu/ml.  Urology felt that surgical intervention was not required as the renal parenchyma was not involved and he had no abscess formation.  The patient completed 2 weeks of ertapenem and his renal function returned to baseline.
I took several learning points away from this case:
  • As someone who spends a lot of time signing off patients’ results, I realise that ‘no significant bacteriuria’ is not the same as ‘no growth’, and in this case the difference was substantial.  The wording of how we report things and how we interpret that is crucial.
  • A high index of suspicion is required to diagnose emphysematous UTIs and the most appropriate imaging modality should be considered.  Ultrasound is generally the first line investigation for urinary obstruction in patients with acute kidney injury or febrile urinary tract infection due to high sensitivity for hydronephrosis, lack of ionising radiation and lower cost than CT. Ultrasound appearances in emphysematous UTIs can be difficult to interpret however: gas, calculi and calcifications are hard to distinguish and there is often variability in how they are reported. CT is able to precisely localise the presence of gas within the urinary tract and determine whether there is involvement of the renal parenchyma and perinephric tissues.  It can also identify any concomitant pathology or alternate diagnosis e.g. renal calculi.  CT is therefore preferable for diagnosis and subsequent severity staging.
  • Pneumaturia has been described as a presenting feature of emphysematous UTI.  Other causes include vesicovaginal or vesicoenteric fistulae, renal tumour infarction and recent instrumentation.  The unexpected air hiss when catheterising this gentleman was a warning of a more serious pathology and should prompt further investigation.

While the outcome of emphysematous pyelitis is better than that of pyelonephritis (which has a mortality of 18-70% depending on extent of involvement), it is still not a condition to be taken lightly. 
Post by Ailish Nimmo, Royal Infirmary of Edinburgh