Case of the Missing Kidney: Investigation of Metastatic Teratoma in a Solitary Kidney

Introduction: This case highlights the diagnostic and management challenges of Acute Kidney Injury (AKI) in a patient with a solitary kidney and unconfirmed medical history complicated by invasive metastatic teratoma. Case Description: A 36-year-old male with an atrophic left kidney (history of renal artery stenosis, unconfirmed if congenital) presented to the ED after his PCP noted profound AKI of 4.5 mg/dL (baseline 1.5). The patient was hypertensive in the ED (197/127 mmHg). Urinalysis was bland, and imaging revealed right sided hydronephrosis with compression of the ureter with retroperitoneal cystic necrotic retrocrural and retroperitoneal Iymph nodes (differentials: lymphoma vs tuberculous adenitis). Testicular ultrasound revealed calcified left testicle with cyst. Initial work up with tumor markers (AFP 16ng/mL, B-hCG negative, LDH 161 U/L) was equivocal. The patient underwent right nephrostomy tube placement and lymph node aspiration which was negative. Subsequent orchiectomy of the left testicle, right renal stent placement, retrocrural mass resection and left nephrectomy was performed to identify potential contribution to atrophic kidney. Pathology eventually revealed teratoma; but, the left kidney was not involved. Perioperative MRI of the right kidney showed wedge-shaped legions within the right kidney consistent with nephritis/infarct and surrounding lymphadenopathy. Post operatively, the patient’s creatinine plateaued at 2.8 mg/dL. Discussion: This case underscores the medical complexity of diagnosis when it comes to unconfirmed congenital conditions.Though the left kidney was ultimately uninvolved, there appears to have been significant impact to the right kidney. Perioperative imaging is concerning for an FSGS precipitated by the surrounding inflammation versus infarcted parenchyma. However, a renal biopsy in this individual would be risky. Additionally highlighted is the rapid renal compromise potential of an aggressive teratoma in a young adult male.Retroperitoneal Lymph nodes (white arrows)