Pyelonephritis versus cystitis
Pyelonephritis is infection of the kidney, whereas cystitis is infection confined to the bladder; pyelonephritis adds systemic illness, in which the whole body is made ill.
Remember
Fever with one-sided loin (flank) pain and tenderness at the renal angle (the spot just below the rib, beside the spine) suggests pyelonephritis, whereas bladder symptoms alone do not show the level of infection.
Memory aid
cystitis stays below the belt, whereas pyelonephritis makes the patient feverish and loin-sore
Think of cystitis as staying low and local, and of pyelonephritis as adding fever and loin pain.
Pyelonephritis is an upper urinary tract infection (UTI): infection of the kidney and renal pelvis (the funnel-shaped space where urine collects in the kidney). It develops when bacteria ascend from the bladder up the ureter to the kidney.
Cystitis is the lower UTI, infection confined to the bladder. It causes dysuria (pain or burning when passing urine), frequency and sometimes suprapubic discomfort (aching in the lower tummy, above the pubic bone), but it does not usually make a person ill throughout the body.
The hallmark of pyelonephritis is systemic illness on top of the urinary symptoms: fever, rigors (shaking chills as the temperature climbs), sweats and malaise (a general feeling of being unwell). There is usually loin pain (pain in the flank, the side of the back below the ribs), often one-sided and worse on movement, with renal angle tenderness. A doctor checks the renal angle by gently percussing (tapping) over it.
Dysuria and frequency are usually present in pyelonephritis too, but they can be absent, so they cannot separate the two. Cloudy urine, blood in the urine and suprapubic discomfort occur in cystitis and do not on their own show which part of the tract is infected.
Pyelonephritis can progress to urosepsis (sepsis arising from the urinary tract), so any UTI with features of sepsis needs urgent hospital assessment.
Key facts
- Hallmark
- systemic illness on top of urinary symptoms, with fever, rigors, sweats and malaise.
- Loin pain
- often one-sided and worse on movement, with tenderness at the renal angle.
- Bladder symptoms
- dysuria and frequency are usually present in pyelonephritis but can be absent.
- Shared features
- dysuria, frequency, suprapubic discomfort and cloudy urine occur in both upper and lower UTI.
- Sepsis
- any UTI with features of sepsis needs urgent hospital assessment.
Exam traps
- Dysuria and frequency do not tell upper from lower infection, because they occur in both cystitis and pyelonephritis.
- Suprapubic discomfort fits cystitis, but it does not show the level of infection, because it occurs in both upper and lower UTI.
- Cloudy urine does not distinguish upper from lower infection, because it can occur in both cystitis and pyelonephritis.
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