Kidney, tuberculosis of:

Kidney, tuberculosis of: 

Renal tuberculosis (renal TB) or tuberculosis of the kidney is a type of extra-pulmonary tuberculosis that affects the kidney. Extra-pulmonary tuberculosis refers to tuberculosis that affects an organ outside the lungs. Other sites of extra-pulmonary tuberculosis are the pleura (the covering of the lungs), the lymph nodes, the fallopian tube in females and the epididymis in males, the bone marrow, and the hindbrain.

Renal tuberculosis may affect either one or both kidneys. The inner part of the kidney called the medulla is usually affected, though the infection usually starts from the cortex which is the outer part. Renal tuberculosis is sometimes a part of the tuberculosis that affects the entire genitourinary tract. 

Causes 

Renal or kidney tuberculosis is caused by Mycobacterium tuberculosis and is one of the most common forms of TB. It usually develops in adults, but it is also possible to have kidney TB in children.

Kidney TB is more likely to develop in those with pulmonary tuberculosis. This is because lung TB can spread to the kidneys by lymphatic or hematogenous means. Moreover, if the bacilli have been displaced from the lung by anti-TB drugs, they can spread to the kidneys through the bloodstream.

Symptoms 

There are no early symptoms of kidney tuberculosis, and most people have no signs or symptoms until they have been diagnosed. The clinical symptoms of urogenital TB are insidious and can be difficult to diagnose and treat. Symptoms can include: 

• Persistent fever
• Weight loss
• Night sweats
• Dysuria
• Sterile pyuria
• Hematuria
• Flank or abdominal pain
• Nocturia

These symptoms can also be associated with a genital mass or pelvic tenderness, obstructive urination, and abdominal colic. In addition, patients may develop interstitial nephritis and acid-fast bacilli, which tests can identify.

Diagnosis 

Renal tuberculosis is difficult to diagnose since not too many physicians will suspect the condition. However, it is important to diagnose it since the patient can recover completely with the right treatment.

Tests used to diagnose renal tuberculosis include the following:

Blood tests

Blood tests that should be done include the following:

• A full blood count and ESR (erythrocyte sedimentation rate) which may indicate the presence of an infection. The ESR should be repeated on a monthly basis after starting treatment to test for the response to the treatment
• Renal function tests, which include measurement of blood urea, uric acid and creatinine to test the functioning of the kidneys
• Tests to evaluate calcium metabolism in case of calcium deposits in the kidney

Tuberculin skin test

• In this test, a small amount of tubercular protein is injected into the skin of the inner forearm. A firm red bump (induration) appears after 2 to 3 days if the person has been previously exposed to M tuberculosis. The test is positive in around 80% cases of renal tuberculosis.

Urine tests

The following urine tests may be done to diagnose renal tuberculosis:

• A urine routine examination which may show the presence of pus cells and red blood cells
• Urine culture on specific media that promote the growth of mycobacteria. It should be done on three to five early morning urine samples. It takes 4 to 8 weeks for the results to be available
• The culture can be done on a specific liquid medium, which like the polymerase chain reaction (PCR) provides quicker results resulting in early detection of the infection

Imaging tests

Imaging tests of the urinary system that may be used in the diagnosis of renal tuberculosis include the following:

• Intravenous pyelogram / Intravenous urogram: In this imaging test, a dye is injected into the blood which is filtered by the kidneys, and passes through and delineates the urinary tract. It can detect structural and functional problems caused by tuberculosis on the urinary tract. The test should be repeated after three to four months after starting treatment to check if any surgical treatment is needed
• CT scan, which is useful in assessing advanced disease of the kidney
• X-ray, which may show the presence of calcium deposits
• Ultrasound, to monitor response to treatment

Note: Rate any residual disability of infection within the appropriate body system as indicated by the notes in the evaluation criteria. As applicable, consider the long-term health effects potentially associated with infectious diseases as listed in §3.317(d) of this chapter, specifically Brucellosis, Campylobacter jejuni, Coxiella burnetii (Q fever), Malaria, Mycobacterium Tuberculosis, Nontyphoid Salmonella, Shigella, Visceral Leishmaniasis, and West Nile virus.