Beyond the Lungs: An Atypical Presentation of Renal Tuberculosis.

Renal tuberculosis (TB), an underrecognized form of extrapulmonary TB, often presents with nonspecific symptoms and challenging diagnosis and, therefore, it is difficult to diagnose. The subtle clinical manifestations and the absence of typical pulmonary signs frequently delay recognition and treatment. A 66-year-old man with type 2 diabetes mellitus and a cortical cyst in the left kidney presented to the emergency room with fatigue, anorexia, weight loss, and intermittent fever. Image exams revealed a large left renal cystic lesion initially suggestive of a cystic nephroma, which is a benign lesion. Ultrasound-guided aspiration and drainage of the lesion, followed by microbiological evaluation, identified co-infection with Mycobacterium tuberculosis and Escherichia coli. The patient received targeted antibacterial therapy with ceftriaxone and standard anti-tubercular therapy (isoniazid, rifampicin, pyrazinamide, and ethambutol) after pulmonary TB was excluded. His condition improved, and follow-up imaging showed a reduction of the cystic mass. Two weeks later, the pigtail, inserted at the time of the drainage of the lesion, was removed, and the patient was discharged with a referral to a Pulmonary Diagnostic Center for the continuation of TB treatment. This case highlights the diagnostic complexity of renal TB and the importance of considering it in the differential diagnosis of atypical renal lesions, particularly in patients with risk factors. Early intervention, accurate microbiological diagnosis, and appropriate anti-tubercular therapy can lead to favorable outcomes.