4   What might be causing Bella’s recurrent UTIs?

5   How would you account for the signs and symptoms?

6   What investigations might be considered?

7   What is the usual treatment for uncomplicated lower UTIs?

8   Describe the mode of action of trimethoprim and nitrofurantoin

9   What health promotion activities might Bella have chosen?

ANSWERS

1 What is the structure and function of the urinary system?

A

•   The urinary (sometimes called renal) system helps maintain homeostasis by keeping normal blood constituents, including water and salts, at healthy levels.

•   It includes two kidneys (located on the posterior abdominal wall) and the urinary tract, comprising the ureters, bladder and urethra (Karch 2010). The kidneys and ureters generally refer to the upper urinary tract, the bladder and urethra to the lower urinary tract.

•   Once formed, urine passes from each kidney into a thin tube, a ureter. Each ureter continuously squirts small amounts of urine into the bladder, for temporary storage.

•   When 300 to 400ml of urine accumulate in the adult bladder, sensitive nerve fibres in the stretched bladder wall are stimulated. These send a message to the brain, telling the person the bladder needs emptying.

•   The muscles in the bladder wall contract, ‘pumping’ urine into a single slit-shaped tube called the urethra from where it is expelled outside the body. The urethra is longer in men (18–20cm, running the extra length of the penis) than in women (4cm).

•   The process of expelling urine, called micturition, usually occurs voluntarily, when convenient and in private.

•   In babies and small children, a simple spinal reflex controls the passage of urine. By school age, the urinary system has reached maturity. Children normally have bladder control at age 5 (Hogston and Marjoram 2011).

2 Describe normal urine and explain how the urinary tract is kept healthy

A NORMAL URINE

•   Normal urine is pale (when dilute) to deep amber (when concentrated) in colour, clear, slightly aromatic and acidic (pH 6 with a range of 4.5–8). The pH can change as a result of metabolic processes or diet. Changes in colour (red) may occur after eating beetroot or rhubarb.

•   The daily amount of urine produced (1000–1500ml in a healthy adult) and the amount of waste it contains is tailored to the body’s needs at the time it is formed.

•   The specific gravity varies from 1.001–1.035. Urine is more concentrated in the morning; with reduced fluid intake during sleep, hot weather and muscular exercise urine production is decreased.

•   Normal urine contains little or no protein, no glucose, ketones or blood.

HEALTHY URINARY TRACT

Several physiological and immunological mechanisms keep the urinary tract healthy.

•   The bladder has a thick muscular wall, lined with specialized mucus-producing cells (transitional epithelium). This allows it to stretch, recoil and form a protective coat from the acidic urine.

•   Antibacterial substances in the mucous lining of the bladder eliminate many organisms, protecting against potential invading bacteria. Surviving micro-organisms tend to be washed out of the urethra.

•   Reflux of urine is prevented by the one-way valve effect at the junction between the ureters and the bladder. A further sphincter is located where the bladder meets the urethra (Mulryan 2011).

•   A child’s elimination pattern is similar to an adult’s, occurring six to eight times a day. Adequate intake of fluids (preferably water) and regular micturition ‘flush’ the urinary tract, keeping it healthy. This is aided by the bactericidal effect of acid urine and the presence of urea (Prosser et al. 2000).

A The distinction between a lower UTI and an upper UTI can often be made on the basis of the patient’s symptoms; there is no specific laboratory test for the differentiation of a lower and an upper UTI (Finch et al. 2003). Typically, in a lower uncomplicated UTI there will be dysuria (pain on micturition), frequency, urgency, pain and discomfort in the lower abdomen but no fever. The urine may appear cloudy and offensive. Lower UTIs can be symptomatic, asymptomatic, sporadic or recurrent. They can present silently or with symptoms. Many cases of urethritis have no known cause – i.e. non-specific urethritis (Thomas et al. 2007).

A more complicated upper UTI may involve loin pain, fever, rigors (shivering similar to the shaking associated with feeling cold) and possibly confusion. Hospital treatment may be required (Ford and Roach 2010).

The most common cause of a UTI is gram negative E. coli bacteria from the patient’s own faecal flora (Thomas et al. 2007). These originate from the bowel and settle around the urethra. They then ascend into the bladder, infecting the normally sterile urine. The ‘opening’ (meatus) of the urethra, the anus, and the vagina in females, are in close proximity, separated only by a moist, small, skin-covered structure called the perineum. This is often heavily colonized with E. coli, commensal bacteria, which, living happily in our intestines, break down foodstuffs and allow us to absorb vitamin K. They can, however, cause a UTI if they gain entry to the bladder, and cause over 80% of childhood UTIs in the community (Polnay 2003). Females are particularly susceptible to the development of UTIs due to the shortness of the urethra and the relative ease with which micro-organisms may enter the bladder via an ascending infection. Urinary stasis (when the bladder isn’t emptied often enough or residual volumes of urine are left in the bladder after micturition) is a major contributory factor.

4 What might be causing Bella’s recurrent UTIs?

A The cause could be the same bacteria that caused Bella’s previous episode or it could be different. E. coli is responsible for 85% of recurrent uncomplicated lower UTIs but other bacteria become increasingly frequent. Less commonly the cause is bacteria such as Staphylococcus (Saprophyticus in sexually active women), Proteus, Klebsiella and Enterobacteria especially in older women. Recurrent UTIs are more likely to be caused by a resistant strain of bacteria (Royal College of Physicians 2008).

Recurrent, uncomplicated lower UTIs are common in healthy, young, sexually active women. During sexual intercourse there may be trauma to the urethra which is easily irritated. Bacteria may be inoculated into the urinary tract, possibly made worse by the use of contraceptive devices such as diaphragms or spermicides.

5 How would you account for the signs and symptoms?

A

•   It is not uncommon for a UTI to be asymptomatic when bacteria are present in the urine without any symptoms, but this has few consequences apart from in pregnant women.

•   Urine becomes more acid than normal so that even small amounts irritate the bladder’s sensitive lining and urethra, producing dysuria (burning sensation on micturition).

•   The urine may be cloudy because it contains pus or blood, and smell unpleasant.

•   Lower abdominal pain often accompanies cystitis.

•   Inflammation of the protective mucosa may also lead to blood in the urine (haematuria) which further worsens the irritability of the bladder.

•   The person would have a raised white cell count as the bone marrow increases production of certain types of white blood cells (neutrophils and monocytes).

6 What investigations might be considered?

A Recurrent, uncomplicated lower UTIs in otherwise healthy, young, sexually active women require investigation and screening for Chlamydia trachomatis (HPA 2011). When a lower UTI is suspected in primary care, a dipstick urine test is carried out to guide treatment. Bella’s urine contained leukocytes (pyuria, present in order to fight infection), nitrites and blood (haematuria) indicating a UTI.

Bella’s urine also contained bacteria (bacteriuria). This would have been determined from a midstream specimen of urine (MSU), examined in a microbiology lab to determine the nature and sensitivity of the infection for treatment. Occasionally, it may be necessary to image the urinary tract (ultrasound) as this can eliminate abnormalities. Bella was referred to a urologist (a doctor specializing in urinary disorders) who performed a cystoscopy. Here, a rigid or flexible cystoscope is inserted through the urethra to inspect the interior surface of the lower urinary tract, a procedure also used to identify stones and fistulae and take a tissue biopsy.

7 What is the usual treatment for uncomplicated lower UTIs?

A The treatment for UTIs mostly consists of antimicrobials to remove bacteria from the urinary tract. Any antimicrobial therapy should be consistent with local antibiotic therapy, guided by the microbiology laboratory. Uncomplicated lower UTIs often respond to trimethoprim and nitrofurantoin, with amoxicillin or cefalexin as an alternative (BNF 2012). Drugs are also available to stop urinary tract muscle spasm, decrease urinary pain and protect the cells of the bladder from irritation. Bella is likely to have taken paracetamol for pain relief but, if this wasn’t strong enough, may have been prescribed diclofenac or mefanamic (Karch 2010).

8 Describe the mode of action of trimethoprim and nitrofurantoin

A Although Bella can’t remember which antibiotic she had when younger, it is likely to have been trimethoprim. This was first used in 1980 and is currently the first choice for lower UTIs. Amoxicillin was previously the antibiotic of choice for lower UTIs in children, however, increased rates of E. coli resistance have made this less acceptable.

Trimethoprim, a synthetic (man-made) antibiotic similar to the sulphonamides, is used to treat many forms of bacterial infection, but particularly infections of the urinary and respiratory tracts. It is cost effective, works well and is generally well tolerated. Trimethoprim interferes with the production of tetrahydrofolic acid, a chemical that is needed to produce proteins in bacteria and human cells.

Trimethoprim does not achieve significant levels in the bloodstream because it is primarily excreted by the kidneys, exerting its effect on bacteria in the urinary tract. Because of the ease with which the kidneys concentrate antibiotics in the urine, lower UTIs may be effectively treated using single doses of trimethoprim (600mg). More persistent infections, particularly those affecting the upper urinary tract (ureters and renal pelvis) are treated with 7–10 day courses of trimethoprim, 100mg at night or 200mg twice daily according to severity.

Trimethoprim is well absorbed by the GI system and administration may be as tablets, in suspension or by injection. Unwanted side-effects may be nausea, vomiting and GI disturbances. Itchy rashes may break out, and there may be effects on blood constituents, causing certain blood disorders. The drug can also lead to a type of anaemia due to its effects on folate. This is usually counteracted by giving the patient folic acid (Barber and Robertson 2012). Had Bella been pregnant, or had severely impaired kidney function, trimethoprim would not have been prescribed.

NITROFURANTOIN

Nitrofurantoin is a synthetic antimicrobial, available for oral use only. It is thought to damage the DNA of the bacteria. Used specifically for UTIs, it is absorbed from the gut and excreted through the kidneys very quickly. It is not as effective against as many gram negative bacteria as newer drugs but is reserved as a second-line drug (HPA 2011). Nitrofurantoin should be taken with caution as side-effects include anorexia, nausea, vomiting, diarrhoea and acute and chronic pulmonary reactions. Bella discussed taking a low dose of nitrofurantoin long term (a year), but declined and decided to examine her lifestyle instead.

9 What health promotion activities might Bella have chosen?

A

•   Drink 2L (4 pints) or 8–10 glasses of plain water a day including a glass of water before sexual intercourse to allow for urinary output afterwards.

•   Avoid bladder irritants such as caffeine products, alcohol, artificial sweeteners, spicy foods and carbonated drinks (remember, urine contains all the waste products filtered from the kidneys – the more these are ingested, the more waste from them there will be in the urine).

•   Be aware that vigorous or frequent intercourse may contribute to UTIs.

•   Make a point of going to the toilet often, and always before and after sexual intercourse to cleanse the urethra and empty the bladder. The maintenance of good personal and perineal hygiene is a must.

•   Avoid constipation.

•   Ensure good hygiene and wiping techniques (from front to back), avoiding introduction of pathogens from the bowel.

•   Avoid irritating soaps and bubble baths.

•   Wear cotton underwear which is not too tight, allowing ventilation.

•   Keep taking the medication as directed, even if the symptoms appear to have cleared up (very important) (adapted from Polnay 2003; Edelman and Mandle 2010).

Having followed the advice above, Bella also learned that drinking cranberry (or blueberry) juice might help. The use of cranberry juice for individuals with recurrent UTIs may relieve some of the symptoms. There is evidence that adherence to the urinary tract by E. coli can be impaired by cranberry juice (Lavender 2000; Edelman and Mandle 2010).