Urinary tract infections

Cystitis and Pyelonephritis

‘Complicated’ UTIs can be considered to be those where either there is something wrong with the patient’s immunity (e.g. diabetes) or urinary tract (e.g. polycystic kidneys), or both. Also included here would be recurrences or those failing to respond. Complications arising from a UTI are peri-nephric abscesses, ATN secondary to vomiting and dehydration, and renal failure secondary to gentamicin toxicity.

Cystitis (suprapubic pain, dysuria, minimal systemic features, polymorphs in the urine) is a self-limiting condition which may settle in 80% just with vigorous fluid intake, but is the battleground for fights to prove the relative superiority of different antibiotics, which probably cure another 10-15% of patients.

Pyelonephritis is associated with more marked systemic features and renal angle tenderness (just push gently – you don’t need to ‘punch’!) All of this group should receive antibiotics and those who are vomiting or particularly ill should get parenteral therapy.

Investigations.

In the setting of a typical clinical history, the finding of leukocytes and nitrites on dip sticks is adequate, remembering that a PV discharge may give false positives for both, and old urine from a bag will be positive for nitrites. Expired sticks will also be positive (even before dipping in the urine)

In the absence of leukocytes and nitrites, but with a strong clinical suspicion, the presence of any abnormality (e.g. blood or protein) on dipsticks should make prompt microscopy (by yourself!) mandatory. In persons with diabetes and other causes of high fluid intake (and thus dilute urine) the dipsticks may be entirely negative, but microscopy of a spun deposit may be rewarding.

Urine should only be sent to the laboratory for culture if you are still entertaining the diagnosis of a UTI in spite of negative microscopy, or if it is likely to be a ‘complicated UTI’ as defined above.

Management.

• Unless the patient has cardiac problems or chronic renal failure with fluid overload, suggest increasing fluid intake to at least 2 litres per day orally.
• Do not use mist pot citrate or other urinary alkalinisers – it may stop your antibiotic working well.
• For uncomplicated UTIs in otherwise well patients prescribe one of: fosfomycin 3 g PO as a single dose, or gentamicin 5 mg/kg intramuscularly, also as a single dose: avoid gentamicin in pregnancy and renal impairment, or nitrofurantoin 100 mg 6 hourly for 5 days (often compliance issues with dosing four times per day).
• In otherwise well patients with complicated UTIs use ciprofloxacin 500 mg 12 hourly, but extend the course to a full 7-10 days.
• In systemically ill patients needing parenteral therapy, admit and start gentamicin 6 mg/kg daily intravenously as a single dose (e.g. 320 mg daily for a 55 kg person, or 400 mg daily for a larger person with a lean body mass of 70 kg). For patients with pyelonephritis and renal impairment or pregnancy, use a third generation cephalosporin e.g. ceftriaxone 1g IV daily. Switch to oral therapy once tolerated. Duration of therapy should be 7 days for quinolones, but at least two weeks if using non-quinolone antibiotics.
• Although cheap and readily available, urinary antiseptics such as nalidixic acid and nitrofurantoin are not appropriate for complicated UTIs or pyelonephritis. Resistance may also develop quite rapidly

Perspective – diagnosing urinary tract infections.

Vaginal infections may confuse the diagnosis of UTI, so take a history for these and examine appropriately. The diagnostic value of the individual symptoms of dysuria, frequency, haematuria and flank pain and the signs (fever, lower abdominal discomfort and PV discharge) is poor, but in combination they perform better.¹ Dysuria and frequency on their own have LR+ of 1.5 and 1.8 respectively, whereas haematuria is slightly more convincing (LR+ 2.0.) Dysuria and frequency with no PV discharge has a LR+ of about 8.0. Dipsticks positive for both leukocytes and nitrites has a LR+ of 4.2, and LR- of 0.3:

A combination of dysuria and frequency without a vaginal cause for these symptoms is very suggestive, and in that context positive findings on dipsticks are more or less confirmatory. With more equivocal clinical findings the dipsticks is not diagnostic!

Bilharzia

Consider the diagnosis in any patient with haematuria who has been or still is in a bilharzia area. Other symptoms of the chronic infection include suprapubic pain, frequency and dysuria. Diagnosis is based on the microscopic identification of eggs in urine collected in the middle of the day.

Treatment

Praziquantel 40 mg/kg as a single dose (e.g. four 600 mg tablets in a 60 kg individual) will cure about 85% to 95% of patients.² If this doesn’t work, the same dose can be repeated after a fortnight.

Renal tuberculosis

Renal tuberculosis should be suspected in individuals with symptoms of urinary tract infection in whom there is pyuria but no growth. Symptoms have generally been present for longer than in patients with conventional bacterial UTIs, and some patients may present with obstructive symptoms and signs. Ultrasound may be helpful, but the diagnosis is made either by the demonstration of AFBs in the urine (microscopy or AFB culture) or by finding tuberculosis on histology (usually from cystoscopy).

Duration of therapy (conventional anti-tuberculosis treatment) is poorly defined. Some authorities suggest treating for at least 9 months in the presence of cavitatory disease, but six months should be adequate for most patients. Whether corticosteroids reduce stricture rate when there is ureteric involvement is unclear³.

Acute and chronic prostatitis

Clinical features – acute prostatitis presents with symptoms very similar to those of acute cystitis; the key differentiator is marked prostatic tenderness on PR examination. Chronic prostatitis presents with more indolent features of lower abdominal or back pain, nocturia, frequency and occasional dysuria. Tenderness on PR may be mild or non-existent. The diagnosis may be made by examining specimens from three phases of micturition – initial (urethral), mid (bladder) and terminal (after prostatic massage). If the third specimen contains leukocytes on dipsticks and this was not present on the earlier specimens, then prostatic inflammation is likely. Culture of this last specimen may be informative.

Medication

Antibiotics with good prostate penetration include doxycycline, co-trimoxazole, and the quinolones, with therapy traditionally being given in conventional doses but for a more protracted course than in cystitis – e.g. two weeks for acute prostatitis and 6-8 weeks for chronic prostatitis.

Prognosis

Acute prostatitis generally resolves rapidly; the outlook in chronic prostatitis is less favourable with some series quoting response rates of about 50%

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1. Bent S, Nallamothu BK, Simel DL, et al. Does this woman have an acute uncomplicated urinary tract infection? JAMA. 2002;287:2701-10. ↩

2. Fukushige M, Chase-Topping M, Woolhouse MEJ, et al. Efficacy of praziquantel has been maintained over four decades (from 1977 to 2018): A systematic review and meta-analysis of factors influence its efficacy. PLoS Negl Trop Dis 2021;15(3): e0009189. https://doi.org/10.1371/journal.pntd.0009189 ↩

3. Mantica G, Ambrosini F, Riccardi N,et al. Genitourinary Tuberculosis: A Comprehensive Review of a Neglected Manifestation in Low-Endemic Countries. Antibiotics. 2021; 10(11):1399. https://doi.org/10.3390/antibiotics10111399 ↩

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