RENAL SARCODOSIS
RENAL SARCODOSIS
Renal involvement that can be defined
by either renal histologic alteration
or a deterioration in kidney function,
occurs in 35-50 % of ptns
with sarcoidosis, though is commonly undetected. Primary renal
manifestations include nephrolithiasis & nephrocalcinosis + acute interstitial nephritis with or without granuloma formation.
The classic renal lesion is non-caseating granulomatous interstitial nephritis, but this
lesion per se rarely induces a clinically
significant renal disease. Hypercalciuria & hypercalcemia are mostly inducing
the clinically significant renal disease.
Glomerular disease, obstructive uropathy, and ESKD can also be seen but are not common.
Nephrocalcinosis & nephrolithiasis are the result of hypercalcemia and/or
hypercalciuria induced by hyperabsorption of ingested Ca owing
to increased production of calcitriol
by the activated mononuclear cells.
Stones are consisted primarily of Ca+ oxalate, but
can be mixed with Ca+ phosphate. Ptns may show polyuria + eGFR decline due to hypercalcemia-induced pre-glomerular
arteriole vasoconstriction. Steroids (anti-inflammatory effect > diminish calcitriol
synthesis), chloroquine, hydroxychloroquine, & ketoconazole can improve Ca+ metabolism in sarcoid ptns. Ptns with sarcoidosis interstitial nephritis present
with an high SCr that’s detected on routine lab profiles in the initial evaluation
for sarcoid disease. Ptns mostly have clear
evidence of diffuse active sarcoidosis elsewhere in his
body. Normal urinalysis is a common finding or with only sterile pyuria or
mild proteinuria.
There’s
no single diagnostic test for sarcoidosis. Dgx of sarcoidosis-induced
interstitial nephritis is usually
given via a renal biopsy that shows
an interstitial mononuclear infiltrate,
non-caseating granuloma, tubular injury, and, with more disease chronicity, interstitial fibrosis. These findings may suggest, but not diagnostic of sarcoidosis. Considering interstitial nephritis here must rely mainly upon
the exclusion
of other etiologies and upon the declaration of extrarenal manifestations of sarcoid disease
to confirm the diagnosis. Sometimes, ptns with renal
sarcoidosis have no extrarenal manifestations upon presentation. So, all
ptns with granulomatous interstitial nephritis on kidney biopsy should perform a chest
radiograph, pulmonary function testing,
and, if these’re non-diagnostic, a high-resolution chest CT to evaluate for pulmonary sarcoidosis.
Steroids have been reported
to be an effective ttt for ptns with sarcoid interstitial nephritis, despite the
recovery may be incomplete due to longstanding disease with irreversible renal damage.
All ptns with decreased eGFR related
to biopsy-proven sarcoidosis interstitial
nephritis, a trial of oral prednisone is suggested. Optimal dose is not certain.
A given regimen is prednisone
1 mg/kg/d for 6-12 weeks, with
a slow tapering thereafter to maintain the dose of 10-20 mg for an
additional 6-9 months. Ptns may present
with GN, despite the relationship to
sarcoidosis has not been proven. As in other forms of sarcoid nephropathy, the steroids can improve
kidney function. Ureteral
obstruction as a result of:
1) Nephrolithiasis,
2) Retroperitoneal fibrosis,
3) Retroperitoneal lymph node affection, &
4) Direct ureteral involvement by sarcoid.
Obstructive
uropathy due
to retroperitoneal affection may be responsive to steroid therapy, but
invasive urologic decompression or HDX may be required prior to a clinically significant response. ESKD with the need of RRT is uncommon,
despite many ptns may show a decreased eGFR.
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