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Investigations in Urinary tract infection

What investigations are specific for urinary tract Infection?

The urinary tract consists of the kidneys, the ureters, the bladder and the urethra. To understand the cause and progress of treatment in any parts of this urinary tract, we need to carry out some specific investigations.

Investigation for urinary tract infection using dipstick
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The majority of investigations in case of any parts of the urinary tract are as follows:

  • Microscopy of urine:
    • examination for casts,
    • red blood cells,
    • white blood cells and
    • bacteria.
  • Urine culture and sensitivity test:
    • Urine culture and sensitivity test is carried out to isolate the organisms that may be causing the infection and to determine their susceptibility to various antibiotics.
  • X-ray of abdomen:
    • To look for presence of calculi (stones), kidney stones or any other pathology in kidneys or urinary tract .
  • Ultrasonography of abdomen:
    • To look for any abnormality in kidneys, bladder or ureters.
  • Cystoscopy:
    • To look for any abnormality in the urethra and bladder.

Let’s now learn in detail what these tests mean for you if your doctor has prescribed these tests-

Examination of Urine for casts –

 In this test, about 10 ml of urine is taken in a test tube, centrifuged and the sediment is examined under a microscope to see for casts and red blood cells.

Urine microscopy involves analyzing a urine sample under a microscope to identify different types of casts.

Casts are cylindrical structures formed in the kidney tubules and can provide valuable information about kidney health. Here are some common casts and their associations:

  • Hyaline casts: These are transparent, colorless casts and are the most commonly seen in urine samples. Their presence may indicate normal kidney function or dehydration.
  • Granular casts: These casts have a grainy appearance due to the presence of cellular debris. They are often associated with kidney damage, acute tubular injury, or certain infections. The presence of granular casts is indicative of chronic kidney disease.
  • Red blood cell (RBC) casts: RBC casts contain red blood cells and indicate bleeding within the kidney. They are commonly seen in glomerulonephritis, a condition characterized by inflammation of the kidney’s filtering units.
  • White blood cell (WBC) casts: WBC casts consist of white blood cells and suggest inflammation or infection within the kidney. They are often associated with conditions like pyelonephritis or interstitial nephritis.
  • Epithelial cell casts: These casts contain kidney tubule cells and can indicate damage to the tubules. They can be seen in acute tubular necrosis or other kidney disorders.
  • Fatty casts: Fatty casts are characterized by the presence of fat droplets and are associated with conditions like nephrotic syndrome, where there is abnormal leakage of protein from the kidneys.

It’s important to note that the presence of casts alone is not diagnostic of a specific disease. A comprehensive evaluation, including clinical history, additional tests, and consultation with a healthcare professional, is necessary for accurate diagnosis and appropriate management.

What does the presence of red blood cells in urine indicate?

The presence of red blood cells in a microscopy test is important as it can indicate various diseases.

Red blood cells in urine microscopy test may indicate the presence of underlying conditions such as urinary tract infections, kidney stones, bladder or kidney infections, trauma to the urinary tract, kidney disease, or certain types of cancer.

Examination of Urine for leukocytes and bacteria-

In this test, about 10 ml of urine is taken in a test tube and the sediment is examined under a microscope to see for leukocytes and bacteria.

Leukocytes are white blood cells. The presence of white blood cells in urine is reported as pus cells and their quantity per high power field under microscope.

The presence of leukocytes in urine is indicative of infection of the urinary tract. Examination of urine sediment under microscope will show presence of WBCs, bacteria and erythrocytes. The presence of WBCs in the urine indicates pyuria.

Urinary tract infections (UTIs) can result in the presence of white blood cells (WBCs) or pus cells in the urine. These infections are typically caused by bacteria, which can be identified under a microscope. Common bacteria associated with UTIs include Escherichia coli (E. coli), Klebsiella pneumoniae, Proteus mirabilis, and Enterococcus faecalis. Proper diagnosis and treatment from a healthcare professional are essential in managing these infections.

Urine Culture:

This is done to isolate any pathogenic organism from the urine sample. If any organism like “E. coli”, “Klebsiella pneumoniae” or any other organism are isolated from the urine sample, drug sensitivity tests are done to determine which antibiotic will be effective against that organism.

Examination of Urine for sugar

This test is done to see if there is presence of sugar in urine (diabetes). This test can be done using a urine dipstick.

Examination of Urine for ketone bodies

This test is done to see if there is presence of ketone bodies in urine (diabetic ketoacidosis). Again, this can be carried out using a dipstick or in the laboratory.

What is proteinuria?

Proteinuria is defined as excretion of more than 150 mg/day or 0.5 gm/24 hrs protein in the urine. It is reported as amount of albumin, a type of protein, present in the urine. This can be detected by dipstick test or by examination under microscope (dark field microscopy). Proteinuria is associated with glomerular disease, kidney infection and nephrotic syndrome.

Protein in urine can be caused by various conditions, such as kidney disease, urinary tract infection, diabetes, high blood pressure, or pregnancy. A particular type of protein- Bence-Jones protein- refers to a specific type of protein called immunoglobulin light chains, which can be detected in the urine in certain types of blood cancers, particularly multiple myeloma.

Urine Dipstick test

This image below shows all the tests that can be done using urine dipsticks.

Urine dipstick test 2
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