Mycobacteria are gram-resistant, non-motile, pleomorphic rods that are often found in habitats such as water or oil. One type is Mycobacterium tuberculosis, responsible for the development of tuberculosis (TB) in humans. It is an intracellular pathogen usually infecting mononuclear phagocytes (e.g., macrophages) and is termed an “acid-fast bacillus”; once stained, it resists decolourization with acidified organic solvents. The World Health Organization (WHO) estimates that approximately one-third of the world’s population is infected with Mycobacterium tuberculosis, with around ten million new cases per year (WHO 1997). Genitourinary TB is uncommon, accounting in the UK for only 2.6 % of all tuberculosis infections. The vast majority of infections are acquired through inhalation of the organism into the lungs via airborne droplet nuclei, after close contact with an actively infectious individual. Most individuals are easily able to control the initial infection and are asymptomatic, with bacilli either killed off or lying dormant. Development of symptoms depends on both the organism and, more importantly, the host immune response, and thus, disease may occur many years later due to immunosuppression secondary to trauma, AIDS, diabetes, steroids, and other immunosuppressive agents. Prior to the advent of antibiotic therapy, the case fatality was 50 %, but this has now fallen to approximately 4 % per newly identified case. Genitourinary TB is caused by metastatic spread of the organism through the loodstream during the initial infection. The kidney is usually the primary organ infected with urinary disease, and other parts of the urinary tract become involved by direct extension. The initial infection occurs in the renal cortex, where the bacilli can remain dormant within granulomata for decades. This dormant infection then becomes activated due to failure of the local immune response. The primary site for infection of the genital tract is often the epididymis in men and the fallopian tubes in women, also by haematogenous spread. Similar to urinary disease, the infection then spreads to adjacent organs by direct extension. TB should always be suspected in the urinary tract when a patient presents with vague, long-standing urinary symptoms without obvious cause. Men are affected more commonly than women (2:1), and most patients are aged between 20 and 40 years. It is rare in children. Infection of the kidney, ureter, and bladder usually results in urinary frequency without urgency, classically associated with sterile pyuria (not present in 20 % cases). Microscopic hematuria is also often present (50 %), but visible hematuria is rare (10 %). Symptoms are often intermittent and pain is rare, although recurrent cystitis may be an early warning sign. Recurrent hematospermia is a rare presenting symptom, but tuberculosis epididymitis may be the first and only presenting symptom of genitourinary TB, which may involve the testis by direct extension. Clinically it is often identical to acute epididymo-orchitis, with a painful, inflamed scrotal swelling. The tuberculin test involves intradermal injection of a purified protein derivative of tuberculin, which, when positive, causes an inflammatory reaction at the site. A positive reaction only signifies previous infection and is not synonymous with active infection. Diagnosis therefore relies on urine examination. Sterile pyuria is the classic urine analysis finding with microscopic hematuria present 50 % of the time. Routine urine culture may show secondary bacterial infection (20 %); however, cultures for M. tuberculosis take 6–8 weeks, as the organism is slow growing. As the organism is only intermittently excreted, at least three early morning urine specimens (pooled overnight) should be sent and inoculated on Lowenstein-Jensen culture media.

Regards
Calvin Parker
Editorial Assistant
Journal of Nephrology and Urology