Yesterday, i saw a T2DM patient admitted with heavy proteinuria (10 grams), anasarca and slightly elevated serum creatinine (1.5 mg/dL). Digging into her history, T2DM was diagnosed 1.5 years ago. Still, it seems a bit older, as she had diabetic retinopathy six months after diagnosis, which was treated with Laser photo-coagulation. She has a positive family history of diabetes. All features seems complying with a diagnosis of diabetic nephropathy.
With further history checking, her edema started only two months ago, and was progressively deteriorating despite escalating doses of diuretics. On examination, she had ascites, +++ lower extremity edema. Her current investigations reveals significantly high ESR (150 first hour), progressively rising proteinuria (1.5, 5,then 10 gm over a 2 month period), HbA1C 6.2, and nothing else of significance. Her USS shows normal kidneys.
On admission, a suspicion of non-diabetic-kidney-disease (NDKD)
was raised given her progressive proteinuria and high ESR (see the previous discussion about uses of ESR in nephrology practice). A kidney biopsy and a non-contrast CAT scan of chest, abdomen and pelvis were done. CAT scan revealed an ovarian cystic lesion of suspicious nature. MRI of this lesion revealed an ovarian cancer and biopsy showed secondary membranous nephropathy (PLA2R negative in biopsy).
Kidney affection in patients with T2DM is classified into Diabetic kidney disease (DKD), Non-Diabetic kidney disease (NDKD), or combined NDKD over a DKD. In clinical practice, however, diagnostic kidney biopsy is rarely performed in patients with DM and usually, renal impairment and proteinuria are assigned to DKD. The prevalence of NDKD ranges from 33% to 72.5% among patients with T2DM. These numbers are usually inflated and biased by selection of biopsies in atypical presentations like our case. Nevertheless, it is crucial to have a clue when to suspect a NDKD and when to do a kidney biopsy for patients with DM. NDKD can be any of; IgA nephropathy, infection related GN, paraproteinemia, renovascular diseases, cholesterol emboli, ….etc.
Usually the presence of the following events, although not mandatory, raise the suspicion of NDKD; short duration of DM, rapid progression to overt proteinuria, absence of diabetic retinopathy, presence of macroscopic hematuria or RBC cast, and signs/symptoms of other systemic diseases.
In summary, having a low threshold to biopsy patients with T2DM, is advocated by some clinicians to detect NDKD alone and mixed cases of DKD and NDKD. Centers with this policy can better serve their patients and diagnose different diseases that would have been mistakenly labelled as DKD. Our case has a relatively straightforward queries, that were explained by investigations and biopsy. Other cases may need an expert eye and a high index of suspicion!
18 April 2019