Case Presentation: A 70-year-old male presented with a low-grade fever, progressive weakness and urinary frequency. Prior to this admission, he had a diagnosis of recurrent urinary tract infection (UTI) that was treated with antibiotics. A CT scan of his abdomen and pelvis, performed out of concern for an abscess, revealed right-sided ureterohydronephrosis. A stent was placed for ureteral stricture and purulent urine was drained. Cytology showed no malignancy. Record review revealed that each UTI episode was associated with sterile pyuria. In addition, he stayed in a homeless shelter for five months ten years ago. On this admission, his serum WBC was 2.9, urine WBC was >100 and the urine culture remained negative. Urine acid-fast bacilli (AFB) stain, culture and QuantiFERON were sent out. Urine stained 1+ AFB. QuantiFERON was positive after being negative two months prior. The patient had no pulmonary symptoms and his sputum stained negative for AFB. Antituberculous therapy was started. Urine M. tuberculosis (MTB) PCR was positive and his urine culture ultimately grew MTB.
Discussion: UTI, particularly in elderly patients, is commonly seen by medicine hospitalists. In the setting of persistent sterile pyuria, the absence of apparent bacterial infection prompts the investigation of an alternative etiology. This vignette illustrates the importance of considering urogenital tuberculosis (TB) as the cause of persistent sterile pyuria. Urogenital TB accounts for 10 – 15% of extrapulmonary TB (EPTB) in the world. While systemic symptoms of infection such as fever and weight loss are rare, urinary frequency, dysuria and urgency occur in up to 50% of cases. Persistent sterile pyuria is one of the characteristic findings. CT may show calcification or ureteral stricture that can cause hydronephrosis and kidney damage. The diagnosis is established through urine AFB stain, MTB culture and PCR for MTB. The sensitivity of AFB stain depends on the mycobacterial load. A positive AFB stain by itself is not diagnostic since nontuberculous mycobacteria can be present in the urine. The positive AFB stain in this vignette indicated a high mycobacterial load. Serial morning urine AFB cultures (at least 3) are the standard approach with a sensitivity of 60% and a specificity of 100%. Morning urine increases culture’s sensitivity. Urine PCR has a high specificity but low sensitivity for EPTB. A positive QuantiFERON suggests TB exposure. The treatment for EPTB is the same as pulmonary TB. Though relapse can occur up to 6% post treatment, patients that undergo nephrectomy of the involved kidney have relapse rate of <1%. Therefore post therapy surveillance is important for patients without nephrectomy.
Conclusions: Urogenital TB should be considered as an etiology of persistent sterile pyuria to avoid a potential delay in treatment. Urine AFB stain, culture and PCR are the key diagnostic tools. Nephrectomy reduces the likelihood of relapse.