Table 2.
Indications for kidney biopsy and corresponding findings
| Kidney Biopsy | All Patients (n=43) |
|---|---|
| Indications for kidney biopsy, n (%) | |
| CKD | 17 (39.5) |
| AKI | 13 (30.2) |
| AKI on CKD | 11 (25.6) |
| Proteinuriaa | 2 (4.7) |
| Hypercalcemiab | 4 (9.3) |
| Biopsy findings | |
| Interstitial nephritis, n (%) | 36 (83.7) |
| GIN | 14 (32.6) |
| Non-GIN | 22 (51.2) |
| Calcium phosphate deposits, n (%)c | 25 (58.1) |
| MN secondary to sarcoidosis, n (%)d | 2 (4.6) |
| Other histologic findings | |
| Global glomerulosclerosis (%) | 0 (0–20) |
| ATN, n (%) | 14 (32.6) |
| IFTA, n | 39 |
| None, n (%) | 12 (30.8) |
| Mild, n (%) | 10 (25.6) |
| Moderate, n (%) | 11 (28.2) |
| Severe, n (%) | 6 (15.4) |
| Vessels | |
| Normal | 15 (34.9) |
| Arteriosclerosis | 26 (60.5) |
| Mild, n (%) | 12 (27.9) |
| Moderate, n (%) | 14 (32.6) |
| Severe, n (%) | 0 (0) |
| Arteriolar hyalinosise | 7 (16.3) |
| Coexisting glomerular disease, n (%) | 8 (18.6) |
| IgANf | 4 (9.3) |
| DNg | 2 (4.7) |
| Glomerulomegalyg | 1 (2.3) |
| Microangiopathic changesg | 1 (2.3) |
ATN, acute tubular necrosis; DN, diabetic nephropathy; GIN, granulomatous interstitial nephritis; IFTA, interstitial fibrosis and tubular atrophy; IgAN, IgA nephropathy; MN, membranous nephropathy.
Both patients demonstrated membranous nephropathy on biopsy.
Among the four patients, two had CKD, one had AKI on CKD, and one had AKI. All three patients with CKD or AKI on CKD exhibited nongranulomatous interstitial nephritis with calcium phosphate deposits, while the patient with AKI presented with nongranulomatous interstitial nephritis.
Among the 25 patients, eight exhibited granulomatous interstitial nephritis, while 13 exhibited nongranulomatous interstitial nephritis.
Both patients lacked interstitial nephritis and calcium deposits but exhibited intrathoracic sarcoidosis lesions.
Five patients also had arteriosclerosis.
One patient exhibited granulomatous interstitial nephritis with calcium deposits, while two patients exhibited nongranulomatous interstitial nephritis with calcium deposits. The other one patient exhibited sarcoidosis lesions affecting both intrathoracic and extrathoracic regions, including bone involvement. Despite the absence of interstitial nephritis and calcium deposits, renal sarcoidosis was strongly suspected based on clinical findings with limited renal biopsy sample and steroid treatment before kidney biopsy. In biopsy, the four patients exhibited only slight mesangial expansion or evidence of IgA-positive immunofluorescence staining. As their renal manifestations were more consistent with sarcoidosis involvement, treatment decisions were primarily guided by sarcoidosis management protocols.
These patients also exhibited nongranulomatous interstitial nephritis with calcium deposits.