Adult cancer survivors and risk of kidney disease?

Long term renal toxicities from chemotherapy in cancer survivors is likely to exist. A recent study in CJASN 2013 looked at this very question. Over 700 childhood cancer survivors were reviewed and function was assessed regarding kidney function loss.  Risks were then identified.
What factors were major predictors of loss of GFR later in life after experiencing treatment for childhood cancers?

1. Nephrectomy  ( nephron mass related)
2. Abdominal radiation ( radiation nephropathy complications)
3. High dose ifosfamide exposure ( proximal tubular toxin)
4. High dose cisplatin exposure ( known tubular toxin)

The full study can be found here

In the NEWS: Acute tubular damage from synthetic cannabinoids

A recent report from CDC has suggested that there have now been several cases reported of acute renal injury( some requiting dialysis) from synthetic cannabinoids such as K2, spice. It all started when the cause of kidney failure was unknown and links were being made with fluorinated synthetic cannabinoids.  Kidney biopsy of some cases suggested tubular toxicity and interstitial nephritis which is the classic finding seen with most nephrotoxic agents. No reversing agents have been identified.
The full report can be found at the CDC website.  Prior cases of these reported are from n/v leading to pre renal AKI only.

Interestingly, there have been some basic science studies suggesting the opposite effect in the kidney. Some have even considered this to use for pain and symptom management of CKD.

Nevertheless, the synthetic forms are now rapidly appearing in the market and kidney disease should be considered as a toxic effect of these agents and kept in mind in the differential diagnosis of AKI( especially ATN/AIN) of unclear etiology in the right setting.

Hibernating bears and Nephrology

An interesting concept in science is biomimicry. It is the science that takes inspiration from unique designs and processes in nature to help humans.

Learning from the Ursidae( hibernating bears) about how they remain metabolically quiet and yet have no major complications can help science. If we had 6 months of bed rest, we would have heart failure, blood clots, muscle wasting, hypercalcemia and bed sores.  Interestingly, these bears have no heart failure, no blood clots, only have 10-15% reduction in muscle mass and only have fat breakdown. They remain without bed sores and normocalcemic.  Why do these bears not get azotemia in these settings? They have marked reduction in GFR when they hibernate, yet no azotemia? Why?

A recent article in Kidney international looks at this very concept and proposes some hypothesis to test.

Detective Nephron's next venture

ASN Kidney News has the next issue of the series of Detective Nephron. He returns this time with a novel glomerular disease case. Check out on pages 22-23 of the Feb 2013 issue of ASN Kidney News

Pitfalls of urinary protein/crt ratio

Nephrologists often use a rule of thumb that the urine protein: creatinine ratio—a unitless number—approximates the 24-h protein excretion in grams. This approximation is based on the assumption that the 24-h urine creatinine excretion is approximately 1000 mg.
There are few instances when this might not be true and hence in those cases the Total Protein/creatinine ratio can be misleading and give false results.

1. AKI:- As there is decreased clearance of creatinine, the total protein/crt ratio can have now a falsely lower denominator and hence leading to a larger ratio. This can possibly mistake some cases of just pure AKI with AKI now with nephrotic syndrome. 

2. Increased Muscle mass: In cases of gross increase in muscle mass, the ratio can grossly underestimate the total ratio. 

3. Severe CKD

A nice reference is in CJASN from 2009

PitFalls in GFR: Pregnancy

A 29 year old pregnant female with a serum crt of 0.8mg/dl and eGFR of 90cc/min.
During Pregnancy, GFR increases by 40-65%, as a result, crt will fall and be lower than usual state of health in most part of pregnancy. 

Per studies, the MDRD formula underestimates the true GFR on the basis of inulin clearance by more than 40ml.min.  Another study found the bias to be less- around 20cc/min. There are currently no published data on the accuracy of the MDRD formula in pregnant subjects with GFR <60 ml/min. Given these issues, 24-h urine collection for CrCl remains the gold standard for GFR estimation in pregnancy. In the above case, it may reflect diminished renal function in the setting of pregnancy. 

Ref:
http://www.ncbi.nlm.nih.gov/pubmed/17970797
http://www.ncbi.nlm.nih.gov/pubmed/17909992

Concept Map: Hypophosphatemia

Here is a concept map of hypophosphatemia based on two great articles. Click on it to get a larger view.

Two great references are:
http://www.ncbi.nlm.nih.gov/pubmed/17568018
http://www.ncbi.nlm.nih.gov/pubmed/16932412