Renal failure in lupus

Glomerulus with thrombi in a case of thrombotic microangiopathy related to SLE


Today we discussed renal failure (or acute kidney injury) in the setting of lupus. This scenario raises many diagnostic possibilities. Some important points:

Whenever faced with a new (or worsened) problem in the setting of a pre-existing disease, a useful dichotomy is whether this new problem is related or unrelated to the underlying disease.

Directly related to SLE
1) Lupus nephritis
2) Renovascular disease
3) Thrombotic microangiopathy (TTP-like situation), especially in context of antiphospholipid antibodies
4) Libman-Sachs endocarditis embolizing to kidneys (very rare)

Indirectly related to SLE
1) Prerenal state from cardiovascular event / disease (note high risk of CV disease in SLE)
2) Tubulointerstitial disease from medications
3) Prerenal state from medications (e.g. NSAIDs)

Unrelated: Usual approach of prerenal, renal, postrenal.

As in any case of acute kidney injury, the evaluation must include

1) Clinical indications for dialysis (pulmonary edema, uremic pericarditis)
2) Clues to the etiology (BP, volume status, rashes, arthritis, etc)
3) Urinalysis (the "physical examination of the kidney")
4) Assessment of serum and urine electrolytes, osmolality, lab evaluation for secondary causes

Lupus Nephritis

Accumulation of immune complex deposits is the pathologic mechanism, esp. in glomeruli.

Abundance and intraglomerular distribution of IC's are correlated with severity of lupus
nephritis. This is the basis of the WHO classification:

I- no glomerular abnormalities or minimal mesangial.
II- mesangial lupus nephritis- mesangial immune deposits. Variable hypercellularity
III- focal, segmental lupus nephritis; scattered peripheral glomerular deposits, with focal necrotizing and proliferative changes in fewer than 50% of glomeruli
IV- diffuse proliferative GN; extensive subendothelial deposits and necrotizing changes
V- membranous- subendothelial deposits with few or no mesangial deposits. This is not a GN cause (i.e. not as 'nephritic'; more 'nephrotic')

Notes: there is overlap between classifications, and this does not represent a progression. There is a high proportion of pts who evolve from one form to another.

Thrombotic microangiopathy / TTP in SLE

It is well established that autoimmune disease is a risk factor for TTP; checking for hemolytic anemia and RBC fragments (schistocytes) is important to exclude this condition which has a 90% mortality untreated (i.e. without plasma exchange)

Links:
Click here for NEJM clinical-pathological conference on renal failure in SLE
Click here for a presentation I gave on the link between TTP and autoimmune disease (esp. SLE)