Pyelonephritis & UTI

1 · Distinguish upper from lower

Lower UTI (cystitis) — dysuria, frequency, urgency, suprapubic discomfort. Systemically well.

Acute pyelonephritis — the above plus any of:

• Fever and rigors
• Loin pain and renal angle tenderness
• Nausea and vomiting
• Systemic upset

That distinction changes the antibiotic, the route, the duration and the disposal.

2 · Send an MSU before antibiotics

• Obtain a midstream urine sample before antibiotics are started and send for culture and susceptibility (NG111 is explicit)
• Bloods if systemically unwell: FBC, U&E, CRP, blood cultures if febrile or septic
• Pregnancy test in any woman of childbearing age
• Review the choice of antibiotic when cultures return, and narrow the spectrum wherever possible

3 · The dipstick trap in older people

A positive dipstick in a confused older person is not a diagnosis of UTI.

• Asymptomatic bacteriuria is common in older inpatients and in anyone with a long-term catheter — it is a finding, not an infection
• Dipstick is unreliable over 65 and in catheterised patients
• Treating it does not fix the delirium, and it exposes the patient to *C. difficile*, resistance and the harm of a missed real diagnosis

In delirium, look for the actual cause — pain, constipation, retention, hypoxia, drugs, and drug withdrawal — before settling on the urine. Diagnose UTI when there are urinary symptoms or genuine signs of systemic infection, not because the dipstick was to hand.

4 · Antibiotics for pyelonephritis

• Oral first line if they can take it and are not severely unwell
• Cefalexin 500mg BD–TDS, 7–10 days (up to 1–1.5g TDS–QDS if severe)
• Co-amoxiclav 500/125mg TDS, 7–10 days — only if culture confirms susceptibility
• Trimethoprim 200mg BD, 14 days — only if culture confirms susceptibility
• IV (vomiting, unable to swallow, severely unwell): co-amoxiclav, cefuroxime, ceftriaxone or an aminoglycoside
• Review IV by 48 hours and step down to oral

Local antimicrobial policy overrides all of this — resistance is local, and a national default can be wrong on your ward.

5 · Fluoroquinolones — a deliberate last resort

Ciprofloxacin 500mg BD (oral) or 400mg BD–TDS (IV) is listed only if other first-choice antibiotics are unsuitable.

Following MHRA advice (January 2024), fluoroquinolones must only be prescribed when other commonly recommended antibiotics are inappropriate, because of the risk of disabling and potentially long-lasting or irreversible side effects — tendon, musculoskeletal and neurological.

If you find yourself reaching for ciprofloxacin out of habit, that is the moment to check the local guideline instead.

6 · Look for obstruction

An obstructed, infected kidney is a urological emergency. Antibiotics alone are generally insufficient while the obstruction remains — the system needs decompressing.

Suspect it with: a known stone, a single kidney, failure to improve at 48 hours, worsening AKI, or severe unilateral loin pain.

• Urgent imaging — CT KUB (or ultrasound in pregnancy)
• Urology immediately for decompression: nephrostomy or ureteric stent
• This is the pyelonephritis that kills

7 · Admit, refer, or treat at home

Refer to hospital if there are signs of a more serious illness — in particular sepsis.

Consider referral or specialist advice if the person is:

• Significantly dehydrated or unable to take oral fluids and medicines
• Pregnant — admit; pyelonephritis in pregnancy risks preterm labour
• At higher risk of complications: structural or functional urinary tract abnormality, diabetes, immunosuppression

Reassess anyone whose symptoms worsen at any time or fail to start improving within 48 hours — think resistant organism, obstruction, abscess, or a different diagnosis.