How are urinary tract infections diagnosed?

How are urinary tract infections diagnosed?

What to expect at the doctor's office when visiting for a UTI

Since the majority of UTIs are as a result of bacterial pathogens, a medical consultation should be sought so as to receive both an accurate diagnosis and appropriate treatment. A medical consultation with a family physician or general practitioner (GP) will likely entail a medical evaluation (discussion regarding symptoms, medical history, family history and previous / current medication use), physical examination and series of appropriate tests.

The medical evaluation discussion is important as it provides clues not only as they relate to current symptoms, indicative of where in the urinary tract infection has taken place, but also whether or not there are any sexual activity influences or other underlying medical conditions known to cause individuals to be more prone to frequent infections. A doctor will wish to determine how long symptoms have been experienced, if a patient has had any major injuries or surgical procedures in the recent past (which may or may not be related to current infection), and the types of medications which have recently been or are currently being used (prescription or over-the-counter – including supplements and herbal varieties).

During a physical examination, a doctor will check all vital signs and assess the nature of symptoms being experienced. This will also help to clarify lower or upper infections and assist a doctor in making an accurate diagnosis for treatment purposes.

Testing may involve the following:

1. Laboratory testing

  • Urinalysis: A doctor will request that a urine sample be given in a provided container. This will be tested with a dipstick or sent away to a laboratory for analysis. The report of the analysis will normally detail any bacteria (or fungus) determined to be present, the presence of white blood cells (which normally increase when infection is present in the body as a way to fight off the offending organism) or nitrates. The presence of bacteria in the urine alone is not enough of an indicator to make a UTI diagnosis as many of these organisms are also present in healthy individuals. The laboratory results, coupled with findings during a medical evaluation and physical examination will be used together to make an official diagnosis. A person with symptoms will be identified as having a UTI if the urine sample contains more than 100 pathogen organisms per millilitre and an increase in white blood cells (pus cells).
  • Urine culture: A culture may be recommended if a doctor feels it necessary to try and determine the type of bacteria present in the urinary tract. This may be especially helpful in individuals who experience frequent infections or who have underlying medical conditions that make them more prone to UTIs, so as to ensure that treatment (usually antibiotics) is appropriately selected and the most effective preventative measures are recommended (if necessary). A culture may take several days to process in the laboratory while bacteria is grown in the sample for easier identification.

Babies and children who are not yet toilet trained will require a little more assistance in order for urine samples to be collected. In this instance, a thin, flexible tube (catheter) may be inserted into the urethra in order to retrieve a small sample of urine for analysis. A sample retrieved in this way is more often less contaminated (with other microorganisms that can be found on the skin surface) than that which can be obtained using a collection bag secured to a baby’s nappy or diaper area. Contaminated urine can make for inaccurate results, complicating the diagnosis.

2. Imaging tests

Those who experience frequent infections or who appear to have severe or complicated UTIs may benefit from imaging tests which provide a doctor with a more detailed view of the urinary tract. Sometimes an imaging test can help to determine specific problems related to UTIs such as urinary reflux or small bladder capacity.

Some other reasons imaging tests may be beneficial include:
  • Identifying problems with urinary retention (i.e. a person is unable to completely empty their bladder during urination)
  • Discovering why frequency of urination exceeds at least 8 times in a day (i.e. within a 24-hour period)
  • Pinpointing why a person is unable to delay urination (i.e. get to a bathroom / toilet in time) or experiences incontinence
  • Confirming or allaying suspicion of a potential blockage in the urinary tract (e.g. a kidney stone, enlarged prostate gland or tumour)
  • Allowing for a more detailed view when a physical examination identifies a possible swelling or mass in the abdominal area.
  • Aiding in further investigation when blood is present in a urine sample
  • Investigating the cause of severe pain in the lower back, abdomen or groin areas
  • Aiding in identifying contributing factors to high blood pressure (hypertension)
  • Identifying signs / symptoms of kidney failure (including severe fatigue, dizziness, weakness, cognitive problems, swelling affecting the hands, feet or facial area and shortness of breath)

Types of imaging tests which may be recommended

1. X-rays:

Urinary blockages, such as tumours or kidney stones, causing pain and changes in urine flow can be picked up using an X-ray. The shape of the prostate in men can also be viewed using an X-ray to assess any potential problems. X-rays involve a little exposure to ionising radiation and an injection of a contrast dye (injected into a vein in the arm) in order to help visualise the internal structures being assessed.

  • One type of X-ray used for the urinary tract is an IVP (Intravenous pyelogram). This X-ray helps to make urine visible, indicating any blockages in the urinary tract where present. A radiologist will interpret the images taken by an X-ray technician and determine the location where infection is most prevalent in the urinary tract – bladder, ureters, kidneys etc.
  • Another option is a VCUG (Voiding cystourethrogram) which is an X-ray taken while the bladder is full, as well as during urination (voiding). A catheter is inserted into the bladder while a patient is lying on an X-ray table. A contrast dye will be injected to provide a clear view of the full bladder. Several images from various angles may be taken. The catheter may then be removed while a patient urinates – X-ray images will be taken at the same time. This is to determine whether urine flow is normal or not during the emptying of the bladder. A radiologist will interpret the visual image (X-ray) results and supply a report to the treating doctor. A radiologist will be looking for abnormalities on the inside of the bladder and urethra and can pick up abnormal flow of urine (vesicoureteral reflux) where relevant, or possible blockages (such as bladder abnormalities or an enlarged prostate). Children may be given light sedation if this test is necessary, in order to make them more comfortable during the procedure.
2. Ultrasound scan

These imaging devices make use of a transducer that bounces sound waves off of body parts and structures (organs and soft tissues) in the pelvic area in order to produce a visual of the urinary tract (viewed on a screen or monitor). The transducer is a movable device that can acquire various different angles of a structure for medical professionals to interpret for diagnostic purposes.

An ultrasound is a preferred option for children in particular, especially if they are younger than the age of 2, as it is a painless process that does not expose children to radiation during the imaging process.

Children with hypertension (high blood pressure), fever, poor growth or a history of bladder and or / kidney trouble will likely be sent for an ultrasound scan. Those who do not appear to respond well to treatment will also likely be sent for an additional scan during a follow-up consultation.

Types of ultrasound which may be recommended include:

  • Abdominal ultrasound: A gel is applied to the surface of a patient’s abdominal skin and the transducer is manoeuvred over the abdomen to assess the entire urinary tract. A technician will be looking for any signs of damage or abnormalities during the scan.
  • Transrectal ultrasound (sometimes with a prostate biopsy): This scan may be recommended for males if the assessing physician would like to examine the prostate gland. A transducer is inserted into the rectum in order to better pick up the size of the prostate gland and determine whether there are any abnormalities, like a mass or tumour present. Should there be a mass or tumour, a doctor will recommend a biopsy (removal of tissue) in order to accurately test for malignancy (cancer). Prostate tissues that are extracted will be examined under a microscope (by a pathologist) and an appropriate report provided to the physician. Some light sedation or local anaesthesia may be used during this test.
3. MRI (Magnetic resonance imaging)

This test makes use of radio waves and magnetic fields to produce detailed images of the body’s internal structures. A contrast dye may be used during the scan to highlight areas of the urinary tract being assessed (organs and soft tissues). Light sedation may be necessary for patients experiencing difficulties with being in a confined space, but generally anaesthetic is not required for this test. If one is claustrophobic, it is advisable to request that mirrors be placed above your head so that you can see outside of the scanner as this helps to alleviate anxiety.

If a doctor wishes to assess the kidney arteries, a MRA (magnetic resonance angiogram) may be recommended. This is to examine the blood vessels which supply blood to the organs for filtering. If there is any arterial stenosis or narrowing of these vessels, blood flow restriction will show on the scan and help to diagnose any kidney function difficulties that may have been picked up during the medical consultation. Signs of kidney function failure will also generally be tested using this type of scan.

4. CT (Computerised tomography) scan

This scan combines X-ray technology and computerised software in order to create three dimensional visuals of internal structures (organs and soft tissues). As with an MRI, contrast dye may be used in order to highlight these structures for the scanning process. Potential obstructions in the urinary tract (like kidney stones, cysts or tumours) can be picked up using this imaging technique, as can signs of infection.

5. Radionuclide scan

A small amount of radioactive chemical is injected into the bloodstream in order to highlight areas of examination in the urinary tract using special cameras and computers. Images are taken as the radioactive chemical passes through. This scan is typically recommended to assess kidney function but can also be used to assess the bladder and urethra.

6. Cystoscopy

A thin, flexible tube with a camera is inserted into the urethra and bladder in order to examine these structures for any signs of inflammation (redness) and swelling which may be involved in the cause of infection. A structural anomaly may be determined as a potential cause of a UTI during this examination.

7. Urodynamic testing

This test may be recommended in order to assess how well a patient’s bladder, sphincter muscles and urethra are functioning in relation to urine storage and excretion.

Factors your doctor will consider when making a diagnosis

Before making a diagnosis, a doctor will take into consideration various factors or sets of symptoms which may be similar to those experienced in UTIs. Some conditions as they relate to genders may also form part of a differential diagnosis, before a UTI (or anything else related to one) is diagnosed and a treatment plan of action recommended.

1. General considerations when diagnosing a UTI

  • The combination of a high fever, body chills, nausea and vomiting may be more suggestive of a kidney infection rather than that of the bladder.
  • Signs of dehydration (such as an elevated heart rate and dry mucous membranes), clamminess (in the extremities) and low blood pressure may indicate impairments in vascular tone as a result of bacteraemia (septic shock) and not, for instance, only an infection of the bladder.
  • UTIs which affect individuals with a spinal cord injury will display some of the following signs and symptoms: fatigue, fever, body chills, muscular spasticity, cloudy urine, dizziness and fainting (when standing up, if the injury permits), as well as an overdistended bladder.
  • Medical conditions, such as diabetes which present complicated UTIs may prompt a doctor to assess for renal and perineal abscesses, severe infections of the bladder and kidneys (emphysematous cystitis, emphysematous pyelonephritis and xanthogranulomatous pyelonephritis), fungal pathogens / infections and urinary obstructions.

2. Paediatric UTI considerations

Things specific to children (some of which may result in similar urinary troubles) that a doctor will also keep in mind during diagnosis include:

  • Uninhibited detrusor contractions (this refers to frequency and urge in relation to urinary incontinence) which may occur without any local irritation or signs of infection. To assess voiding dysfunction, a doctor may place a child in various positions to tighten the pelvic floor muscles, apply direct pressure using his or hands to the urethra, or encourage the ‘Vincent curtsy’ (placing a child in a squatting position and pressing his or her heel against the urethra).
  • Nephrolithiasis (this refers to calculi formations in the kidneys or ureters – a small but hard deposit which can result in a fair amount of pain when passing urine).
  • Paediatric appendicitis (acute inflammation and infection of the appendix).
  • Paediatric gastroenteritis (an intestinal infection which can be fairly severe and even life-threatening for a young child)
  • Pinworms (an intestinal parasite which can cause severe genital itching)
  • Urinary tract obstruction
  • Pregnancy (this may apply to sexually active teenage females – vaginitis, vulvovaginitis and cystitis may also be assessed in this regard).

3. Female (adult) UTI considerations

  • Cervical motion tenderness may indicate pelvic inflammatory disease (PID) and is assessed by lubricating and inserting two fingers into the vagina to locate the cervix.
  • Symptoms for urethritis may overlap with those of an infected bladder. These can include painful and difficult urination, as well as urinary hesitancy. Fever may be more predominant in those with urethritis and is less likely to be associated with bladder infections. Along with fever, urethral discharge is more often seen in those with urethritis. Bladder infections are more often associated with urinary urgency, excessive urination and problems with completely emptying the bladder. Urinary incontinence can sometimes occur in those with bladder infections.
  • Pregnant women may experience asymptomatic bacteriuria (ASB). This refers to an abnormally high number of bacteria in urine without other accompanying symptoms. This is often most common between weeks 9 and 17 of pregnancy. ASB can result in complications such as pre-term labour, low birth weight infants, intrauterine growth retardation, anaemia, hypertensive disorders (such as high blood pressure / preeclampsia) and amnionitis (a uterine infection). Screening may be recommended during the first trimester and again during the third should initial test results show up positive or related symptoms develop. Should any related symptoms develop, a pelvic examination may be performed (except during the third trimester) in order to identify possible cystitis (bladder infection), vaginitis (vaginal inflammation) or cervicitis (inflammation of the cervix). A woman will normally develop a high fever when an infection has reached the kidneys, experience flank tenderness and have a very pale / ill appearance. The foetal heart rate will also be assessed during all evaluations.
  • Post-menopausal women may experience urethritis (infection-induced inflammation of the urethra) along with symptoms of burning urination, increased urination urgency and frequency, as well as vulvar and or/ vaginal discharge and itching.
  • Sexually active women: A physician will take into consideration the possibility of STD-related cervicitis, pelvic inflammatory disease (PID), vaginitis, herpes simplex virus or chlamydial infections.

4. Male (adult) UTI considerations

  • A male patient will likely undergo a physical examination that pays special attention to the bladder, kidneys, prostate, external genitalia (penis, testes and epididymis) and all vital signs. Things to note or look for include the presence of any lesions, abnormal markings or ulcers, redness or discharge (meatal or penile), tenderness and swelling (which may indicate a scrotal haematoma and is usually characterised by swelling and a bluish discolouration of the scrotum), and hydrocele (a fluid-filled sac in the thin sheath surrounding the testicles).
  • A rectal examination may be recommended. This involves a complete sweep of the rectum and palpation of the prostate. Care will be taken in examining the prostate as acute bacterial prostatitis can become fairly painful.
  • During a physical examination a doctor will also look for the following: The presence of fever, abnormal / elevated heart rate, pain in the flank area or portion of back overlaying the kidneys (referred to as costovertebral angle tenderness) or inguinal adenopathy (swollen lymph nodes in the groin area).
  • Conditions a doctor will keep in mind during evaluation include: Prostatitis syndromes (acute and chronic prostatitis) which may present symptoms of pain in the lower abdomen, testicles or penis, during urination or ejaculation, as well as bladder irritation, blood in urine or semen, cloudy urine, perineal discomfort, fever, body chills, general malaise and muscle pain (myalgia); cystitis (bladder infection), epididymitis (inflammation of the epididymis), orchitis (inflammation of the testicles), pyelonephritis (kidney infection) and urethritis (infection-induced inflammation of the urethra).
  • A doctor will also keep in mind recent sexual activity, taking into account any possible STD-related conditions.
  • Other factors to consider include: Obstructive prostatism / prostatic hyperplasia (prostate enlargement), urolithiasis (kidney stones), cancer of the bladder, vasculitis (inflammation of the blood vessels), renal tuberculosis, calculi (stone) formation, glomerulonephritis (inflammation of the kidney/s), strictures, appendicitis, acute pancreatitis (inflammation of the pancreas), bacterial pneumonia, acute or chronic pyelonephritis (kidney infection), bacterial sepsis and urinary tract obstruction.
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