The kidneys play a crucial role in BP regulation, hormone synthesis (i.e. EPO, Vitamin D), electrolyte homeostasis, acid-base balance and fluid balance. Here are a few other reminders as per our discussion on AKI this week.
Acute Kidney Injury (AKI): a rise in serum Cr 1.5x or more
the baseline value within 48h
Rapidly Progressive Glomerulonephritis (RPGN): Cr rises within days to weeks. Can be insidious in nature and patients can present quite unwell.
Major Approach to the patient with AKI: Pre-renal, Renal,
& Post-renal
Clues regarding Chronic Kidney
Disease (CKD)
· GFR <60 for three months or more and/or evidence of kidney damage (albuminuria,
urine sediment abnormalities or findings on renal imaging or biopsy
· Renal U/S: small, echogenic kidneys (most consistent with CKD) –progressive loss of
renal parenchyma and increased interstitial fibrosis over time *(keep in mind that the kidneys are
NOT small in DM, amyloidosis acromegaly, HIV nephropathy), Anemia, Volume Overload, Electrolyte-Acid Base imbalance (i.e.
hyperkalemia), Metabolic Acidosis, Ca/PO4 abnormalities (decrease in Vit D
synthesis d/t reduction in function or amt of 1-alpha hydroxylase—increase PO4
d/t decreased filtration, decrease in Ca, increases PTHà renal osteodystrophy)
Always keep in mind URGENT or ACUTE indications for dialysis ("AEIOU"): acidosis (resistant to medical therapy),
electrolytes abnormalities resistant to medical therapy (i.e. hyperkalemia), intoxication (ASA, Li,
methanol), Overload (fluid overload resistance to medical tx); Uremia
(pericarditis, encephalopathy)
Always keep RPGN on your list...
RPGN: a clinical syndrome characterized by features of glomerular disease in the urine (i.e. dysmorphic RBCs in the urine), and progressive loss of renal function over a short time period (i.e. days, weeks, months). Clinically, they can present with fatigue, edema, oliguria. The presentation may be insidious. Initial investigations reveal dysmorphic RBCs, hematuria, variable proteinuria, and elevation of Cr (usually >264).
Morphologically, there are crescent formations evident; these are non-specific markers of a response due to severe injury to the glomerular capillary wall. Left unrecognized and un-treated, these patients can undergo rapid progression to end-stage renal disease (ESRD).
Approach to RPGN
1.Vasculitis (pauci-immune): ANCA +ve
- C-ANCA, with granulomas: Granulomatosis with polyangiitis (GPA, formerly called Wegener's)
- P-ANCA: Microscopic polyangiitis (MPA) or churg-strauss
2.Anti-Glomerular Basement Membrane (GBM) Antibody Disease (linear)
- Anti-GBM Antibody
- Pulmonary hemorrhage: more in keeping with Goodpasture's
- No pulmonary hemorrhage: more in keeping with Anti-GBM disease
3.Immune Complex/Complement Mediated (granular)
- Clinical history & order Complement levels
- low C3: DDx- IBE, HCV, SLE, Cryoglobulinemia, post-strep GN (PSGN), MPGN
- normal C3: DDx- IgA, Fibrillary, HSP
4. Double Antibody Positive Disease
- Pauci-immune, but ANCA-negative
- Immune Complex, but do not fit onto the list above
Investigations:
Labs: Cr urea (*compare
to previous), lytes, extended lytes, CBC, UA, urine Cr, Urine lytes, peripheral
smear
Etiology: ANA, anti-ds
DNA, ENA, P-ANCA, C-ANCA, anti-GBM Ab, C3, C4, CK, uric acid, ASO titre,
HBV/HCV serology, RF, cryoglobulinemia, quantitative Ig, SPEP, UPEP, urine
eosinophils
Initial Management
- Recognition is key! Call Nephrology consult in
- Pulse steroids: Methylprednisolone 1g IV daily x 3 days, followed by prednisone PO (i.e. 1mg/kg PO daily) for a few months, then a taper
- Immunosuppressants: often start Cyclophosphamide 2 mg/kg/d; duration R/A by nephrology
- +/- Plasmapharesis (PLEX): removes circulating antibodies (i.e. anti-GBM Antibodies) and other mediators of inflammation (i.e. complement)
- Initiated if pulmonary hemorrhage!
- Long term: careful follow-up, with bone health preventative measures given the long-term steroid use (i.e. Vitamin D, CaCO3, Bisphosphonate)
- Immunosuppressive therapy, consider PJP Prophylaxis with Septra DS 1 tab PO M/W/F
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