CHAPTER 28 Genitourinary Tuberculosis
What is tuberculosis?
Tuberculosis is a bacterial infection caused by Mycobacterium tuberculosis. It spreads from person to person by a pulmonary route followed by hematogenous seeding to the genitourinary (GU) tract.
When was the first case of tuberculosis described?
Tuberculosis is a disease that has been prevalent for many centuries. Dating back to 7000 BC, human skeletal remains have revealed pathologic findings consistent with tuberculosis (TB) infections.
What are other historical names used for TB?
Scrofula, consumption, phthisis, and Kings-Evil.
Who first described M. tuberculosis and when?
Robert Koch first identified M. tuberculosis as the causative organism in 1882.
What is the incidence of TB worldwide?
The WHO estimated a worldwide incidence of TB at 8.8 million cases per year in 2010 with 3 million deaths per year.
What is the estimated number of people a TB-infected person could subsequently infect?
How often does GU TB occur?
Extrapulmonary TB is seen in 10% of all TB cases and of these, 30% to 40% are in the GU tract.
What are the 2 main mechanisms for eradication of TB?
Case identification and treatment, and Bacillus Calmette-Guerin (BCG) vaccination.
What are the problems associated with BCG vaccination?
The duration of response is only 15 years. It has little effect on the incidence of infection and is ineffective in patients with prior TB infections. BCG also carries many potential side effects.
What are the unique microbiologic characteristics of M. tuberculosis?
M. tuberculosis is an aerobic nonmotile bacterium with a high propensity to develop drug resistance. Its doubling time is slow at 24 hours. It can survive following phagocytosis in the lysosome of the macrophage.
What type of immune response is seen in TB infection?
A cell-mediated immune response from macrophages, T and B lymphocytes, and fibroblasts. Antibodies are not protective and viable bacilli within a tubercle consisting of Langhans giant cells can result in latent infection and reactivation.
What are risk factors for TB reactivation?
Diabetes mellitus, HIV infection, malignancies, chronic steroid use, chemotherapy, and immunosuppression.
Describe the typical histologic findings associated with GU TB.
Lymphocytes, macrophages, and fibroblasts aggregate to form a pathognomonic TB granuloma.
What is the typical gross appearance of TB-infected renal tissue?
Tissue demonstrates central caseating necrosis, sloughed renal papilla, and calyceal ulceration. Late-stage renal involvement demonstrates infundibular narrowing, ureteropelvic junction (UPJ) scarring, and segmental or generalized hydronephrosis.
What are the typical pathologic changes of the ureter in TB infection?
After tubercle formation, the ureteral mucosa undergoes ulceration, then fibrosis and scarring that ultimately cause stricture and obstruction, then fibrotic encasement of the ureter.
What is the typical pathologic appearance of the bladder in GU TB?
Mucosal caseation with an undermining tuberculous ulcer creates a “worm-eaten” appearance of the ulcer with ragged edges.
What are the gross appearance of the epididymis, vas deferens, and testis in GU TB?
Chronic inflammation causes obliteration of the epididymal lumen and nodular epididymitis. This can ulcerate to the skin, creating a tubercular sinus on the posterior scrotum. In a similar fashion, the vas deferens can take on a beaded appearance from segmental dense fibrosis. With chronic testicular infection, replacement of normal tissue with caseous material occurs.
Do nontuberculosis mycobacteria cause pathogenic changes in the GU tract?
This is very rare. Only a handful of cases have been reported. The mycobacteria involved include M. kansasii, M. avium-intracellulare, M. xenopi, and M. fortuitum.
What test can be used to differentiate M. tuberculosis from nontuberculosis mycobacteria?
p-Nitro-α-acetylamino-β-hydroxypropriophenone, the NAP test.
What populations are at highest risk for developing TB?
People living in underdeveloped countries, alcoholics, HIV patients, IV drug abusers, the homeless, and the elderly.
What is the most common age group and gender to develop GU TB?
GU TB is most commonly seen in the 20- to 40-year-old age group with a 2:1 male-to-female predominance.
What is the classic triad of TB infections?
Fatigue, weight loss, and anorexia.
How does TB spread to the GU tract?
GU TB is the result of metastatic spread of the mycobacterium via the blood stream. It usually results from a primary pulmonary focus. Only 25% of patients have a known history of TB.
What is the mechanism that leads to TB of the lower urinary tract?
Urinary excretion of the mycobacterium from the kidney causes seeding and infection of the lower urinary tract. Epididymal and prostatic TB are spread hematogenously.
What are some of the clinical findings associated with GU TB?
Sterile pyuria is the hallmark of GU TB. Other less specific signs are painless urinary frequency, nocturia, hematuria, hematospermia, suprapubic pain, and flank pain.
How often is microscopic hematuria found in cases of GU TB?
Microscopic hematuria is present in approximately 50% of cases.
How should one culture the urine of a patient suspected of having GU TB?
Five consecutive early morning urine specimens should be obtained and cultured on 2 separate media. Lowenstein–Jensen medium will isolate M. tuberculosis, BCG, and nontuberculosis mycobacterium. Radiometric media such as BACTEC 460 is much faster and takes only 2 to 3 days for results.
What is the quickest way to diagnose TB?
Polymerase chain reaction (PCR) testing is highly sensitive, specific, and quick. Results are available in 6 hours.