Urinary Tract Infection

A urinary tract infection (UTI) is referring to an infection of the bladder or kidney. An infecotin of the bladder is called cystitis. Infection of the kidney is called pyelonephritis. 

Urinary tract infections typically occur when bacteria enters the urethra and travels up into the bladder. The bacteria then multiply in the bladder. The bacteria sometimes then travel up the ureter to infect the kidney.

Risk Factors
Urinary tract infections are much more common in females as the urethra is much shorter. Urinary catheters increase the risk as bacteria can travel along the catheter and enter the urinary tract. Obstruction of the urinary tract (such as kidney stones) increases the risk, as urine flow becomes static. Other causes of static urine (such as infrequent bladder emptying or incomplete bladder emptying) also increase the risk. If a man has an enlarged prostate then this increases the risk, as the bladder may not empty fully. Having an impairment of the immune system, (such as diabetes, chronic kidney disease, advanced age) also increases the risk of contracting an infection. 

Signs and Symptoms
The most common symptom is discomfort whilst urinating (dysuria). This is often described as a burning or stinging sensation. Other symptoms include passing small amounts of urine often (urinary frequency) and having sudden and strong urges to urinate (urinary urgency). Occasionally there may be suprapubic discomfort. There may be blood in the urine (hematuria) or pus in the urine (pyuria).

Pyelonephritis may cause all of the signs and symptoms already mentioned, but may also involve fever, nausea and vomiting, and lower back pain (flank pain).

Signs may be unclear in the elderly, sometimes confusion is the only sign. For this reason, elderly patients who present in an acutely confused state should always have their urine tested.

Investigations
Analysis of the urine should be performed on patients suspected of having a urinary tract infection. The patient with a urinary tract infection shall have urine that is positive for leucocytes. Sometimes the urine will also be positive for nitrites, blood and protein.

Urine culture is used to identify the bacteria that caused the infection, and can help determine which antibiotic is best.

Routine blood tests may include renal function tests (creatinine and urea), electrolyte levels and white blood cell count.

Further investigations may be required in severe cases. Blood culture may need to be done to determine whether the infection has spread from the urinary tract into the bloodstream. 

Treatment
Most females with an infection in the bladder (cystitis) can be treated at home with oral antibiotics, mild analgesia, and the advice to drink plenty of water. If discharged home, the patient should be advised to return if the symptoms worsen, because an infection of the bladder (cystitis) can ascend up to cause infection in the kidney (pyelonephritis).

An infection in the kidney (pyelonephritis) usually requires hospital admission for intravenous antibiotics and intravenous fluids. Stronger analgesia might be required.

Complications
The urinary tract infection has the potential to spread to become a severe infection affecting the whole body (this is called urosepsis). Urosepsis should be treated aggressively with antibiotics and intravenous fluids. Inotropes, such as dopamine, may be required.

Special Groups
Special caution should be given for pregnant women, because a urinary tract infection can cause premature labor. For this reason, even asymptomatic urine infections should be treated in pregnant women.

A female who has repeated urinary tract infections, or a man with a single episode of urinary tract infection, requires further investigations so that the cause can be diagnosed (such as structural abnormality, kidney stones, enlarged prostate).