How can I differentiate between pyelonephritis and lower urinary tract infections based on clinical presentation?

To differentiate between pyelonephritis (acute upper UTI) and lower urinary tract infections (UTIs) based on clinical presentation:

• Pyelonephritis typically presents with systemic symptoms such as fever (≥38°C), chills or shivering, and flank (loin) pain or tenderness, indicating upper urinary tract involvement.
• Patients with pyelonephritis may also have signs of systemic illness such as malaise and sometimes sepsis.
• Lower urinary tract infections (cystitis) usually present with localized urinary symptoms such as dysuria (painful urination), increased frequency, urgency, suprapubic pain or tenderness, cloudy or malodorous urine, and sometimes visible haematuria, but without systemic features like high fever or loin pain.
• In children, the presence of bacteriuria with fever ≥38°C or bacteriuria with fever <38°C plus loin pain or tenderness suggests pyelonephritis, whereas bacteriuria without systemic symptoms suggests lower UTI.
• Absence of systemic symptoms and presence of only lower urinary tract symptoms generally indicate a lower UTI.

Therefore, the key clinical differentiators are the presence of systemic symptoms (fever, chills, loin pain) for pyelonephritis versus localized urinary symptoms without systemic illness for lower UTI.

Urgent hospital admission or specialist referral is advised if severe systemic symptoms or signs of complications such as pyelonephritis or sepsis are present.

This clinical differentiation guides management decisions in primary care.

References: ¹,²