Postoperative acute kidney injury associated with cast nephropathy and marked renal interstitial plasma cell infiltration in multiple myeloma: a case report.
Marika Sakai, Minato Umehara, Tetsuro Kusaba et al.
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Case in brief
An 84-year-old man with smoldering multiple myeloma developed severe acute kidney injury after lumbar fixation for a burst fracture. Postoperative bleeding caused profound hypotension and severe anemia; renal dysfunction progressed despite transfusion and fluid resuscitation. Urinalysis showed heavy proteinuria. Kidney biopsy revealed tubular eosinophilic casts consistent with cast nephropathy, marked interstitial infiltration by λ-restricted monoclonal plasma cells, and focal peritubular capillary occlusion. Congo red staining was negative, with no significant glomerular immune deposits. Renal function partially recovered with supportive care but remained below the preoperative baseline.
What made this case unusual
The biopsy showed cast nephropathy alongside marked interstitial infiltration by monoclonal plasma cells and focal peritubular capillary occlusion, findings that may have contributed to the severity and persistence of postoperative kidney injury.
Diagnostic / clinical pearl
In a patient with multiple myeloma and postoperative AKI, heavy proteinuria may signal underlying myeloma-related renal injury; biopsy can identify coexisting lesions beyond cast nephropathy.
Why it matters
The case suggests that perioperative circulatory failure may precipitate overt kidney injury when latent myeloma-related renal lesions are present, even if preoperative serum creatinine is preserved.