Rapidly progressive glomerulonephritis can be a confusing topic. Thankfully, Dr. Margaret Ivanov, one of our awesome nephrologists, dropped by our Hillcrest morning report today and offered some clinical pearls. We discussed the case of a middle-aged man with no history of renal disease who presented with an elevated serum creatinine to the mid-5’s. He has no significant medical history and takes no medications. His urinalysis revealed significant proteinuria and hematuria. Serum studies are positive for ANA and anti-dsDNA, and a renal biopsy showed thrombotic microangiopathy superimposed on a background of class IV lupus nephritis.
In a patient with new renal impairment, you should always ask about medication use, urinary symptoms, and other associated symptoms. Constitutional, mucosal, respiratory, GI, neurologic, hematologic, and dermatologic signs/symptoms may suggest the presence of an underlying disorder. Be sure to also do a good volume assessment to help determine if the patient requires diuresis and/or renal replacement therapy.
A urinalysis is an important first step in the evaluation of AKI. RPGN is a clinical syndrome characterized by rapid loss of renal function (over days or weeks) and a nephritic UA (hematuria with or without proteinuria). Urine microscopy will reveal RBC casts and dysmorphic RBCs. Dr. Ivanov pointed out that the automated process used to result UAs will not disclose the presence of RBC, WBC, and other casts and that urine microscopy will have to be done separately.
We then talked about the workup of RPGN (see below). These studies are typically sent in parallel because the etiology of RPGN cannot be reliably determined based on history and exam alone. (Many of these studies are send-outs and may take days to over a week to result.) Reasons to pursue a renal biopsy include unexplained AKI and an active urinary sediment. The classic pathologic finding in RPGN is crescentic glomerulonephritis. Light microscopy, electron microscopy, and immunofluorescence can help identify the cause of the RPGN. In some cases, multiple processes may be seen on renal biopsy. The biopsy also helps inform treatment and prognosis.
Key Learning Points:
- RPGN is a clinical syndrome characterized by a rapid loss of renal function (typically over days/weeks) and nephritic syndrome (hypertension, hematuria, variable proteinuria, dysmorphic RBCs, RBC casts).
- The classic pathologic finding is cellular crescent formation in the majority of examined glomeruli due to fibrin deposition and cell proliferation (“crescentic glomerulonephritis”).
- A renal biopsy is generally indicated in patients presenting with rapidly progressive glomerulonephritis to ascertain the etiology, determine its chronicity, and inform patient prognosis.
Thank you, Dr. Ivanov, for joining us today!
Medical Spanish Word of the Day: (el) análisis de orina = urinalysis